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  • 1.
    da Silva, Cristina
    et al.
    KTH, School of Technology and Health (STH). Karolinska Inst, Sweden.
    Sahlen, Anders
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska Univ Hosp, Sweden.
    Back, Magnus
    Ruck, Andreas
    Settergren, Magnus
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska Univ Hosp, Sweden.
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering. Sunderby Hosp, Sweden.
    Prosthesis-patient mismatch after transcatheter aortic valve implantation: impact of 2D-transthoracic echocardiography versus 3D-transesophageal echocardiography2014In: International Journal of Cardiac Imaging, ISSN 1569-5794, E-ISSN 1875-8312, Vol. 30, no 8, p. 1549-1557Article in journal (Refereed)
    Abstract [en]

    To investigate the role of 2D-transthoracic echocardiography (2D-TTE) and 3D-transesophageal echocardiography (3D-TEE) in the determination of aortic annulus size prior transcatheter aortic valve implantation (TAVI) and its' impact on the prevalence of patient prosthesis mismatch (PPM). Echocardiography plays an important role in measuring aortic annulus dimension in patients undergoing TAVI. This has great importance since it determines both eligibility for TAVI and selection of prosthesis type and size, and can be potentially important in preventing an inadequate ratio between the prosthetic valvular orifice and the patient's body surface area, concept known as prosthesis-patient mismatch (PPM). A total of 45 patients were studied pre-TAVI: 20 underwent 3D-TEE (men/women 12/8, age 84.8 +/- A 5.6) and 25 2D-TTE (men/women 9/16, age 84.4 +/- A 5.4) in order to measure aortic annulus diameter. The presence of PPM was assessed before hospital discharge and after a mean period of 3 months. Moderate PPM was defined as indexed aortic valve area (AVAi) a parts per thousand currency sign 0.85 cm(2)/m(2) and severe PPM as AVAi < 0.65 cm(2)/m(2). Immediately post-TAVI, moderate PPM was present in 25 and 28 % of patients worked up using 3D-TEE and 2D-TTE respectively p value = n.s) and severe PPM occurred in 10 % of the patients who underwent 3D-TEE and in 20 % in those with 2D-TTE (p value = n.s). The echocardiographic evaluation 3 months post-TAVI showed 25 % moderate PPM in the 3D-TEE group compared with 24 % in the 2D-TTE group (p value = n.s) and no cases of severe PPM in the 3DTEE group comparing to 20 % in the 2D-TTE group (p = 0.032). Our results indicate a higher incidence of severe PPM in patients who performed 2DTTE compared to those performing 3DTEE prior TAVI. This suggests that the 3D technique should replace the 2DTTE analysis when investigating the aortic annulus diameter in patients undergoing TAVI.

  • 2.
    da Silva, Cristina
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska Institute, Stockholm, Sweden .
    Sahlén, Anders
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Karolinska University Hospital, Sweden.
    Bäck, Magnus
    Ruck, Andreas
    Settergren, Magnus
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Department of Cardiology, Karolinska University Hospital, Huddinge, Sweden .
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging. Department of Cardiology, Karolinska University Hospital, Huddinge, Sweden .
    Hemodynamic outcomes of transcatheter aortic valve implantation with the CoreValve system: an early assessment2015In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 35, no 3, p. 216-222Article in journal (Refereed)
    Abstract [en]

    Background and Aims: Transcatheter aortic valve implantation (TAVI) is an established method for the treatment of high-risk patients with aortic stenosis (AS). The beneficial effects of TAVI in cardiac hemodynamics have been described in recent studies, but those investigations were mostly performed after an interval of more than 6 months following aortic valve implantation. The aim of this study is to investigate the acute and short-term alterations in hemodynamic conditions using the echocardiography outcomes in patients undergoing TAVI. Methods and Results: A total of 60 patients (26 males, 34 females; age 84·7 ± 5·8) who underwent TAVI with CoreValve system were included in the study. Echocardiography was performed before hospital discharge and at 3 months follow-up. As expected, TAVI was associated with an immediate significant improvement in aortic valve area (AVA) (from 0·64 ± 0·16 cm2 to 1·67 ± 0·41 cm2, P-value<0·001) and mean gradient (from 51·9 ± 15·4 mmHg to 8·8 ± 3·8 mmHg, P-value<0·001). At 3-month follow-up, systolic LV function was augmented (EF: 50 ± 14% to 54 ± 11%, P-value = 0·024). Left ventricle (LV) mass and left atrium (LA) volume were significantly reduced (LV mass index from 126·5 ± 30·5 g m-2 to 102·4 ± 32·4 g m-2; LA index from 42·9 ± 17·3 ml m-2 to 33·6 ± 10·6 ml m-2; P-value<0·001 for both). Furthermore, a decrement in systolic pulmonary artery pressure (SPAP) from 47·5 ± 13·5 mmHg to 42·5 ± 11·2 mmHg, P-value = 0·02 was also observed. Despite the high incidence of paravalvular regurgitation (PVR) (80%), most of the patients presented mild or trace PVR and no significant progress of the regurgitation grade was seen after 3 months. Conclusion: This study demonstrates that the beneficial effects of TAVI in cardiac function and hemodynamics occur already after a short period following aortic valve implantation.

  • 3. Fomin, Å.a
    et al.
    Da Silva, Cristina
    KTH, School of Technology and Health (STH). Department of Cardiology, Karolinska University Hospital, Stockholm, Sweden.
    Ahlstrand, M.
    Sahlén, A.
    Lund, L.
    Stahlberg, M.
    Gabrielsen, A.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH). Department of Cardiology, Karolinska University Hospital, Stockholm, Sweden.
    Gender differences in myocardial function and arterio-ventricular coupling in response to maximal exercise in adolescent floor-ball players2014In: BMC Sports Science, Medicine and Rehabilitation, ISSN 2052-1847, Vol. 6, no 1Article in journal (Refereed)
    Abstract [en]

    Background: The hemodynamic and cardiac responses to exercise have been widely investigated in adults. However, little is known regarding myocardial performance in response to a short bout of maximal exercise in adolescents. We therefore sought to study alterations in myocardial function and investigate sex-influences in young athletes after maximal cardiopulmonary testing. Methods: 51 adolescent (13-19 years old) floor-ball players (24 females) were recruited. All subjects underwent a maximal exercise test to determine maximal oxygen uptake (VO2max) and cardiac output. Cardiac performance was investigated using conventional and tissue velocity imaging, as well as 2D strain echocardiography before and 30 minutes following exercise. Arterio-ventricular coupling was evaluated by means of single beat ventricular elastance and arterial elastance. Results: Compared to baseline the early diastolic myocardial velocity (E’LV) at the basal left ventricular (LV) segments declined significantly (females: E’LV: 14.7 +/- 2.6 to 13.6 +/- 2.9 cm/s; males: 15.2 +/- 2.2 to 13.9 +/- 2.3 cm/s, p > 0.001 for both). Similarly, 2D strain decreased significantly following exercise (2D strain LV: from 21.5 +/- 2.4 to 20.2 +/- 2.7% in females, and from 20 +/- 1 to 17.9 +/- 1.5% in males, p > 0.05 for both). However, there were no significant changes in LV contractility estimated by elastance in either sex following exercise (p > 0.05). Arterial elastance) Ea) at baseline was identified as the only predictor of VO2max in males (r = 0.76, p < 0.001) but not in females (p > 0.05). Conclusions: The present study demonstrates that vigorous exercise of short duration results in a significant decrease of longitudinal myocardial motion in both sexes. However, in view of unaltered end systolic LV elastance (Ees), these reductions most probably reflect changes in the loading conditions and not an attenuation of myocardial function per se. Importantly, we show that arterial load at rest acts as a strong predictor of VO2max in males but not in female subjects.

  • 4.
    Johnson, Jonas
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Håkansson, Felicia
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Norman, Mikael
    Sahlén, Anders
    Impact of tachycardia and sympathetic stimulation by cold pressor test on cardiac diastology and arterial function in elderly females2013In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 304, no 7, p. H1002-H1009Article in journal (Refereed)
    Abstract [en]

    Johnson J, Hakansson F, Shahgaldi K, Manouras A, Norman M, Sahlen A. Impact of tachycardia and sympathetic stimulation by cold pressor test on cardiac diastology and arterial function in elderly females. Am J Physiol Heart Circ Physiol 304: H1002-H1009, 2013. First published January 25, 2013; doi:10.1152/ajpheart.00837.2012.-Abnormal vascular-ventricular coupling has been suggested to contribute to heart failure with preserved ejection fraction in elderly females. Failure to increase stroke volume (SV) during exercise occurs in parallel with dynamic changes in arterial physiology leading to increased afterload. Such adverse vascular reactivity during stress may reflect either sympathoexcitation or be due to tachycardia. We hypothesized that afterload elevation induces SV failure by transiently attenuating left ventricular relaxation, a phenomenon described in animal research. The respective roles of tachycardia and sympathoexcitation were investigated in n = 28 elderly females (70 +/- 4 yr) carrying permanent pacemakers. At rest, during atrial tachycardia pacing (ATP; 100 min(-1)) and during cold pressor test (hand immersed in ice water), we performed Doppler echocardiography (maximal untwist rate analyzed by speckle tracking imaging of rotational mechanics) and arterial tonometry (arterial stiffness estimated as augmentation index). Estimation of arterial compliance was based on an exponential relationship between arterial pressure and volume. We found that ATP produced central hypovolemia and a reduction in SV which was larger in patients with stiffer arteries (higher augmentation index). There was an associated adverse response of arterial compliance and vascular resistance during ATP and cold pressor test, causing an overall increase in afterload, but nonetheless enhanced maximal rate of untwist and no evidence of afterload-dependent failure of relaxation. In conclusion, tachycardia and cold provocation in elderly females produces greater vascular reactivity and SV failure in the presence of arterial stiffening, but SV failure does not arise secondary to afterload-dependent attenuation of relaxation.

  • 5.
    Johnson, Jonas
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska Institute, Sweden.
    Bergholm, Fredrik
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Brodin, Lars Åke
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Agewall, S.
    Henareh, L.
    The early diastolic myocardial velocity: A marker of increased risk in patients with coronary heart disease2014In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 34, no 5, p. 389-396Article in journal (Refereed)
    Abstract [en]

    Objective: Tissue Doppler imaging (TDI) is a promising echocardiographic modality allowing quantification of myocardial performance. However, the prognostic potential of TDI in patients with acute myocardial infarction (AMI) is not yet investigated. We sought to explore the ability of TDI in identifying patients at risk for new cardiovascular events after AMI. Methods: One hundred and nineteen patients with AMI were recruited prospectively (mean age 61 years; range 32-81 years of age). Patients with diabetes mellitus (DM) were excluded. Echocardiography was performed 3-12 months after AMI. Two-dimensional (2-D) and TDI variables were recorded. The patients were followed during a mean period of 4·6 years (range 1-8 years). The primary end-point was defined as any of the following: death from any cause, non-fatal reinfarction or stroke, unstable angina pectoris, congestive heart failure requiring hospitalization and coronary revascularization procedure. Results: Thirty patients had some form of cardiovascular events during follow-up. Seven patients had cardiovascular death, 13 patients had reinfarction and four patients had a stroke. New angina or unstable angina was recorded in 21 patients. Of these patients, 13 underwent percutaneous coronary angioplasty (PCI) or coronary artery bypass grafting (CABG). The early diastolic myocardial velocity (Em) emerged as the only echocardiographic variable that offered a clear differentiation between patients that presented with new cardiovascular (CV) events as compared to the corresponding group without any CV events at follow-up (P&lt;0·05). In multivariate statistical analysis and after adjustment for age, sex, total cholesterol, body mass index (BMI) and other baseline characteristics, Em remained as independent predictors of CV events (HR, 1·18, 95% CI, 1·02-1·36; P&lt;0·05). However, none of the investigated variables evolved as an independent predictor of cardiovascular morbidity and mortality. Conclusion: Em appears to be a sensitive echocardiographic index in identifying non-diabetic patients with AMI at risk of new cardiovascular events.

  • 6.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Tissue Doppler in Spectral and Color ModeMethodological ConsiderationsNon-invasive Estimation of Left Ventricular Filling Pressures using the E/Em index2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Aims: Tissue Doppler (TD) in spectral mode (spectral TD) and color TD are the two modalities available today in tissue velocity echocardiography (TVE). Measurements of left ventricular (LV) myocardial velocities and displacement may yield different results depending on the employed sonographic modality and the subjective adjustments during data analysis. The ratio of transmitral early diastolic velocity (E) to early diastolic myocardial velocity (Em) has been suggested as a non-invasive estimate of LV filling pressures. The present studies aimed to evaluate the compatibility between the two TD modalities and the effect of temporal filtering and offline gain on velocity and displacement measurements obtained using these two methods. The validity of E/Em in identifying elevated LV filling pressures after acute reductions in hemodynamic LV loading was assessed.

    Methods and Results: In 57 patients, longitudinal myocardial velocity profiles were acquired from the basal LV segments, using spectral and color TD. Peak systolic (Sm) and early diastolic (Em) myocardial velocities and the myocardial displacement during the ejection phase were measured offline. Spectral TD measurements were performed using three different gain settings (0%-, 50%- 100% offline gain). Color TD analysis were performed before and after the application of temporal filtering at 30, 50 and 70 ms filter width. The E/Em ratio was calculated at the different settings. The correlation between spectral- and color TD measurements was good. Changes in offline gain and filter width resulted in significant alterations on spectral and color TD derived measurements, respectively. Sm and Em were significantly higher (p < 0.001) whereas the E/Em was significantly lower (p < 0.001) for measurements performed with spectral TD compared to color TD and the discrepancy among the measurements increased at increasing filter width and gain level. In Study II the results of spectral- and color TD derived displacement were compared to anatomic M-mode. Spectral TD at different gain settings significantly overestimated M-mode derived displacement measurements, whereas the concordance between color TD and M-mode was considerably better.

    In Study III, LV longitudinal systolic myocardial velocities and displacement during ejection period were quantified at the basal septal and lateral wall in 24 healthy individuals using spectral TD, color TD and M-mode. Mean spectral TD systolic velocity and displacement values were obtained from the outer and inner borders of the spectral velocity signal. The estimated mean spectral TD systolic myocardial velocities were highly concordant with corresponding color TD measurements (mean difference 0.1 ± 0.6 cm/s, septal wall; 0.1 ± 1.0 cm/s, lateral wall). Similarly, myocardial displacement obtained by integration over time of mean spectral TD velocities was in good agreement with color TD (mean difference 0.2 ± 0.7 mm, septal wall; 0.02 ± 0.86 mm, lateral wall) as well as with the corresponding M-mode measurements.

    In Study IV, simultaneous LV catheterization and echocardiographic examination was performed in 68 consecutive patients referred for coronary angiography. Doppler signals of the transmitral flow and spectral TD signals at the level of mitral annulus were obtained and the E/Em was then calculated. All examinations were repeated after nitroglycerin (NTG) infusion. At baseline, the predictive ability of E/Em in identifying elevated LVDP was modest at best (area under curve [AUC] ± SE = 0.71 ± 0.08, p < 0.01). The index was more strongly associated with LVDP in patients with reduced ejection fraction (EF) < 55% (r = 0.68; p < 0.01) compared to patients with EF ≥ 55%(r = 0.4; p < 0.05). Following NTG administration, the diagnostic ability of E/Em in detecting elevated LVDP was significantly reduced (area under curve [AUC] ± SE =0.6 ± 0.08, p > 0.05). Changes in LVDP were not reliably tracked using E/Em (p > 0.05).

    Conclusions: Spectral TD yields significantly higher myocardial velocity and displacement values and lower E/Em compared to color TD modality. Increasing gain and temporal smoothing significantly alters the obtained velocity and displacement information and yield greater disparity between measurements derived using the two TD methods. Spectral TD significantly overestimates myocardial displacement obtained using M-mode. On the other hand, the agreement between color TD and anatomic M-mode is considerably better. Measurements based on mean spectral TD velocities were highly concordant with those provided by color TD and M-mode. However, unfavorable limits of agreement discourage the interchangeable use of these modalities. The diagnostic ability of E/Em was poor and declined significantly following acute reduction in LV hemodynamic loading. Changes in LVDP were not predicted by alterations in E/Em. Our findings imply that E/Em might not be sufficiently robust to be employed as a single non-invasive estimate for tailoring medical therapy in patients with elevated LVDP.

  • 7.
    Manouras, Aristomenis
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nyktari, Evangelia
    Sahlén, Anders
    Winter, Reidar
    Vardas, Panagiotis
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    The value of E/Em ratio in the estimation of left ventricular filling pressures: impact of acute hemodynamic load reductionManuscript (preprint) (Other academic)
  • 8.
    Manouras, Aristomenis
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nyktari, Evangelia
    Sahlén, Anders
    Winter, Reidar
    Vardas, Panagiotis
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    The value of E/E(m) ratio in the estimation of left ventricular filling pressures: Impact of acute load reduction A comparative simultaneous echocardiographic and catheterization study2013In: International Journal of Cardiology, ISSN 0167-5273, E-ISSN 1874-1754, Vol. 166, no 3, p. 589-595Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The ratio of the early transmitral flow velocity to the early diastolic tissue velocity (E/E(m)) has been suggested as a reliable estimate of left ventricular diastolic pressures (LVDP). However, the evidence regarding the ability of E/E(m) to detect LVDP changes is relatively equivocal. Our aim was to evaluate the validity of the ratio following acute load reduction. METHODS AND RESULTS: 68 consecutive patients referred for coronary angiography underwent LV catheterization and echocardiography simultaneously. Doppler signals of transmitral flow and spectral TD signals at the level of the mitral annulus were obtained before and directly after intravenous administration of nitroglycerin (NTG). The predictive ability of E/E(m) to identify elevated LVDP was modest (area under curve=0.71±0.08, p<0.01). The index was more strongly associated with LVDP in patients with reduced ejection fraction (EF)<55% (r=0.68; p<0.01) than in patients with normal EF. Following NTG, E/E(m) lacked any predictive potential for elevated LVDP whereas changes LVDP could not be reliably tracked using E/E(m). CONCLUSION: The predictive capacity of E/E(m) for elevated LVDP was weak and declined significantly following acute reduction in LV load. Changes in LVDP were not reliably predicted by E/E(m). The current findings derived from a real-world patient population with relatively high filling pressures indicate that E/E(m) may not be sufficiently robust to be employed as a single non-invasive estimate of LVDP nor for monitoring load reducing medical therapy.

  • 9.
    Manouras, Aristomenis
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Shahgaldi, Kambiz
    Winter, Reidar
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    Measurements of left ventricular myocardial longitudinal systolic displacement using spectral and colour tissue Doppler: time for a reassessment?2009In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 7, p. 12-Article in journal (Refereed)
    Abstract [en]

    Background: Echocardiographic measurements of left ventricular (LV) myocardial displacement may produce different results depending on the choice of employed modality and subjective adjustments during data acquisition and analysis. Methods: In this study, left ventricular longitudinal systolic displacement was quantified in 57 patients (31 women and 26 men, 50 +/- 16 years) using colour (colour TD) and spectral tissue Doppler (spectral TD) before and after temporal filtering (30 to 70 milliseconds in 20-millisecond steps) and changed offline gain saturation (0%, 50% and 100%), respectively. The results were compared with those obtained with anatomic M-mode. Results: Whereas only minor differences occurred between the results of colour TD and anatomic M-mode measurements, spectral TD significantly overestimated the results obtained with both these methods. However, the limits of agreement between the results produced by all three studied methods were not clinically acceptable in any of the cases. The spectral TD displacement values increased along with increasing offline gain saturation whereas the effect of temporal filtering on colour Doppler measurements was insignificant. Conclusion: Measurements of LV myocardial longitudinal displacement employing spectral TD, colour TD or anatomic M-mode produce different results, thus discouraging interchangeable use of these modalities. Whereas the results of spectral TD measurements can be significantly altered by changing offline gain setting, the effect of temporal filtering on colour TD measurements is insignificant, a fact that increases clinical practicality of the latter method.

  • 10.
    Manouras, Aristomenis
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Shahgaldi, Kambiz
    Winter, Reidar
    Nowak, Jacek
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Comparison between colour-coded and spectral tissue Doppler measurements of systolic and diastolic myocardial velocities: effect of temporal filtering and offline gain setting2009In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 10, no 3, p. 406-413Article in journal (Refereed)
    Abstract [en]

    Colour tissue Doppler (TD) has been reported to underestimate the longitudinal myocardial motion velocities measured with spectral TD. This study evaluates the effect of temporal smoothing and offline gain settings on the results of velocity measurements with these two methods and the difference between them. In 57 patients, 2D data and left ventricular velocity profiles were acquired using spectral and colour TD for a subsequent offline analysis. Longitudinal myocardial velocities were measured at unsaturated, 50%-saturated and fully saturated gain, and before and after temporal smoothing using 30, 50, and 70 ms filters, respectively. Gain level and filter width altered significantly the measured velocities. Peak systolic and early diastolic velocities were significantly higher (P < 0.001) and E/E' ratio was significantly lower (P < 0.001) with spectral TD than with colour TD, although there was a good correlation between the results of both TD modalities. The differences between the methods increased at increasing filter width and gain level. Despite good correlation of the results, spectral TD produces significantly higher myocardial velocity values and lower E/E' ratio than colour TD modality. Increasing gain and temporal smoothing alter significantly the results of velocity measurements and accentuate the difference between the two TD methods.

  • 11.
    Manouras, Aristomenis
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Shala, Arben
    Nyktari, Evangelia
    Shahgaldi, Kambiz
    Winter, Reidar
    Vardas, Panagiotis
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Nowak, Jacek
    Are measurements of systolic myocardial velocities and displacement with colour and spectral Tissue Doppler compatible?2009In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 7, p. 29-Article in journal (Refereed)
    Abstract [en]

    Background: Tissue Doppler (TD) in pulsed mode (spectral TD) and colour TD are the two modalities today available in tissue velocity echocardiography (TVE). Previous studies have shown poor agreement between these two methods when measuring myocardial velocities and displacement. In this study, the concordance between the myocardial velocity and displacement measurements using colour TD and different spectral TD procedures was evaluated. Methods: Left ventricular (LV) longitudinal systolic myocardial velocities and displacement during ejection period were quantified at the basal septal and lateral wall in 24 healthy individuals (4 women and 20 men, 34 +/- 12 years) using spectral TD, colour TD and M-mode recordings. Mean, maximal and minimal spectral TD systolic velocities and the corresponding displacement values were obtained by measurements at the outer and inner borders of the spectral velocity signal. The results were then compared with those obtained with the two other modalities used. Results: Systolic myocardial velocities derived from mean spectral TD frequencies were highly concordant with corresponding colour TD measurements (mean difference 0.10 +/- 0.54 cm/sec in septal and 0.09 +/- 0.97 cm/sec in lateral wall). Similarly, the agreement between spectral and colour TD (mean difference 0.22 +/- 0.74 mm in septal and 0.02 +/- 0.86 mm in lateral wall) as well as M-mode was good when mean spectral velocities were temporally integrated and the results did not differ statistically. Conversely, displacement values from the inner or outer border of the spectral signal differed significantly from values obtained with colour TD and M-mode (p < 0.001, in both cases). Conclusion: LV systolic myocardial measurements based on mean spectral TD frequencies are highly concordant with those provided by colour TD and M-mode. Hence, in order to maintain compatibility of the results, the use of this particular spectral TD procedure should be advocated in clinical praxis.

  • 12. Nagy, A. I.
    et al.
    Venkatesharan, Ashwin I.
    KTH, School of Technology and Health (STH). Sri Sathya Sai Institute of Higher Medical Sciences, India.
    Merkely, B.
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska University Hospital, Sweden.
    Barooah, B.
    Dash, P. K.
    Manouras, Aristomenis I.
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska University Hospital, Sweden.
    The pulmonary capillary wedge pressure accurately reflects both normal and elevated left atrial pressure2014In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 35, p. 1184-1184Article in journal (Other academic)
  • 13. Nagy, Aniko I.
    et al.
    Sahlen, Anders
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH). Karolinska Institute, Sweden.
    Henareh, Loghman
    da Silva, Cristina
    KTH, School of Technology and Health (STH). Karolinska Institute, Sweden.
    Gunyeli, Elif
    Apor, Astrid A.
    Merkely, Bela
    Winter, Reidar
    KTH, School of Technology and Health (STH). Karolinska Institute, Sweden.
    Combination of contrast-enhanced wall motion analysis and myocardial deformation imaging during dobutamine stress echocardiography2015In: European Heart Journal Cardiovascular Imaging, ISSN 2047-2404, E-ISSN 2047-2412, Vol. 16, no 1, p. 88-95Article in journal (Refereed)
    Abstract [en]

    Background The combination of deformation analysis with conventional wall motion scoring (WMS) has been shown to increase the diagnostic sensitivity of dobutamine stress echocardiography (DSE). The feasibility and diagnostic power of WMS is largely improved by contrast agents; however, they are not used in combination with deformation analysis, as contrast agents are generally considered to render strain measurement unfeasible. Aims To assess the feasibility of tissue velocity (TVI)- and 2D speckle tracking (ST)-based strain analysis during contrast-enhanced DSE; and to show whether there is an incremental value in combining deformation analysis with contrast-enhanced WMS. Methods DS echocardiograms containing native, tissue Doppler, and contrast-enhanced loops of 60 patients were analysed retrospectively. The feasibility of WMS, TVI-, and ST-strain measurement was determined in 40 patients according to pre-defined criteria. The diagnostic ability of a combined protocol integrating data from contrast-WMS and TVI-strain measurement was then compared with contrast-WMS alone in all 60 patients, using coronary angiograms as a gold standard. Results Both TVI- and ST-based strain analysis were feasible during contrast-DSE (feasibility at peak stress: 87 and 75%). At the patient level, the diagnostic accuracy of the combined method did not prove superior to contrast-WMS (82 vs. 78%); a trend towards improved sensitivity and specificity for detecting coronary artery disease in the right coronary artery circulation (sensitivity: 85 vs. 77%, P = NS; specificity: 96 vs. 94%) was, however, observed. Conclusion Both TVI- and ST-based myocardial deformation analysis are feasible during contrast-enhanced DSE, however, our results fail to demonstrate a clear diagnostic benefit of additional strain analysis over expert WMS alone.

  • 14. Nagy, Aniko I.
    et al.
    Venkateshvaran, Ashwin
    KTH, School of Technology and Health (STH).
    Dash, Pravat Kumar
    Barooah, Banajit
    Merkely, Bela
    Winter, Reidar
    KTH, School of Technology and Health (STH).
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH).
    The pulmonary capillary wedge pressure accurately reflects both normal and elevated left atrial pressure2014In: American Heart Journal, ISSN 0002-8703, E-ISSN 1097-6744, Vol. 167, no 6, p. 876-883Article in journal (Refereed)
    Abstract [en]

    Background Pulmonary capillary wedge pressure (PCWP) is routinely used as an indirect measure of the left atrial pressure (LAP), although the accuracy of this estimate, especially under pathological hemodynamic conditions, remains controversial. Objectives The aim of this prospective study was to investigate the reliability of PCWP for the evaluation of LAP under different hemodynamic conditions. Methods Simultaneous left and right heart catheterization data of 117 patients with pure mitral stenosis, obtained before and immediately after percutaneous mitral comissurotomy, were analyzed. Results A strong correlation and agreement between PCWP and LAP measurements was demonstrated (correlation coefficient = 0.97, mean bias +/- CI, 0.3 +/- -3.7 to 4.2 mm Hg). Comparison of measurements performed within a 5-minute interval and those performed simultaneously revealed that simultaneous pressure acquisition yielded better agreement between the 2 methods (bias +/- CI, 1.82 +/- 1.98 mm Hg). In contrast to previous observations, the discrepancy between the 2 measures did not increase with elevated PCWP. Multiple regression analysis failed to identify hemodynamic confounders of the discrepancy between the 2 pressures. The ability of PCWP to distinguish between normal and elevated LAP (cutoff set at 12 and 15 mm Hg, respectively), as tested by receiver operating characteristics analysis, demonstrated a remarkably high diagnostic accuracy (area under the curve: 0.989 and 0.996, respectively). Conclusions Although the described limits of agreement may not allow the interchangeability of PCWP and LAP, especially at lower pressure ranges, our data support the clinical use of PCWP as a robust and accurate estimate of LAP.

  • 15. Sahlen, A.
    et al.
    Abdula, G.
    Norman, M.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Lund, L. H.
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Altered arterial haemodynamics during exercise in elderly female hypertensives with poor stroke volume reserve2011In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 32, p. 10-11Article in journal (Other academic)
  • 16. Sahlen, A.
    et al.
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Johnson, Jonas
    KTH, School of Technology and Health (STH), Medical Engineering.
    Analysis of aortic characteristic impedance in the time domain: validation using computer simulation2012In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 33, p. 138-138Article in journal (Other academic)
  • 17. Sahlen, A.
    et al.
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering.
    Johnson, Jonas
    KTH, School of Technology and Health (STH), Medical Engineering.
    Altered visco-elasticity of common carotid artery of elderly female hypertensives2012In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 33, p. 618-618Article in journal (Other academic)
  • 18. Sahlen, Anders
    et al.
    Abdula, Göran
    Norman, Mikael
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Ake
    KTH, School of Technology and Health (STH), Medical Engineering.
    Lund, Lars H.
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering.
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering.
    Arterial vasodilatory and ventricular diastolic reserves determine the stroke volume response to exercise in elderly female hypertensive patients2011In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 301, no 6, p. H2433-H2441Article in journal (Refereed)
    Abstract [en]

    Sahlen A, Abdula G, Norman M, Manouras A, Brodin LA, Lund LH, Shahgaldi K, Winter R. Arterial vasodilatory and ventricular diastolic reserves determine the stroke volume response to exercise in elderly female hypertensive patients. Am J Physiol Heart Circ Physiol 301: H2433-H2441, 2011. First published September 16, 2011; doi:10.1152/ajpheart.00555.2011.-Elderly female hypertensives with arterial stiffening constitute a majority of patients with heart failure with preserved ejection fraction (HFpEF), a condition characterized by inability to increase cardiac stroke volume (SV) with physical exercise. As SV is determined by the interaction between the left ventricle (LV) and its load, we wished to study the role of arterial hemodynamics for exertional SV reserve in patients at high risk of HFpEF. Twenty-one elderly (67 +/- 9 yr) female hypertensive patients were studied at rest and during supine bicycle stress using echocardiography including pulsed-wave Doppler to record flow in the LV outflow tract and arterial tonometry for central arterial pressure waveforms. Arterial compliance was estimated based on an exponential relationship between pressure and volume. The ratio of aortic pressure-to-flow in early systole was used to derive characteristic impedance, which was subsequently subtracted from total resistance (mean arterial pressure/cardiac output) to yield systemic vascular resistance (SVR). It was found that patients with depressed SV reserve (NoRes; reserve <15%; n = 10) showed decreased arterial compliance during exercise, while patients with SV reserve >= 15% (Res; n = 11) showed increased compliance. Exercise produced parallel increases in LV end-diastolic volume and arterial volume in Res patients while NoRes patients exhibited a lesser decrease in SVR and a drop in effective arterial volume. Poor SV reserve in elderly female hypertensives is due to simultaneous failure of LV preload and arterial vasodilatory reserves. Abnormal arterial function contributes to a high risk of HFpEF in these patients.

  • 19. Sahlén, Anders
    et al.
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH), Medical Engineering.
    Aagaard, Philip
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering.
    Braunschweig, Frieder
    Altered ventriculo-arterial coupling during exercise in athletes releasing biomarkers after endurance running2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 12, p. 4069-4079Article in journal (Refereed)
    Abstract [en]

    Exercise can lead to release of biomarkers such as cardiac troponin T (cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP), a poorly understood phenomenon proposed to especially occur with highintensity exercise in less trained subjects. We hypothesised that haemodynamic perturbations during exercise are larger in athletes with cTnT release, and studied athletes with detectable cTnT levels after an endurance event (HIGH; n = 16; 46 ± 9 years) against matched controls whose levels were undetectable (LOW; n = 11; 44 ± 7 years). Echocardiography was performed at rest and at peak supine bicycle exercise stress. Left ventricular (LV) end-systolic elastance (ELV a load-independent measure of LV contractility), effective arterial elastance (EA a lumped index of arterial load) and end-systolic meridional wall stress were calculated from cardiac dimensions and brachial blood pressure. Efficiency of cardiac work was judged from the ventriculo-arterial coupling ratio (EA/ELV: optimal range 0.5-1.0). While subgroups had similar values at rest, we found ventriculo-arterial mismatch during exercise in HIGH subjects (0.47 (0.39-0.58) vs. LOW: 0.73 (0.62-0.83); p<0.01] due to unopposed increase in ELV (p<0.05). In LOW subjects, a greater increase occurred in EA during exercise (+81 ± 67 % vs. HIGH: +39 ± 32 %; p = 0.02) which contributed to a maintained coupling ratio. Subjects with higher baseline NT-proBNP had greater systolic wall stress during exercise (R2 = 0.39; p<0.01) despite no correlation at rest (p = ns). In conclusion, athletes with exercise-induced biomarker release exhibit ventriculo-arterial mismatch during exercise, suggesting non-optimal cardiac work may contribute to this phenomenon.

  • 20.
    Shahgaldi, Kambiz
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    da Silva, Cristina
    KTH, School of Technology and Health (STH).
    Bäck, Magnus
    Rück, Andreas
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Sahlén, Anders
    Transesophageal echocardiography measurements of aortic annulus diameter using biplane mode in patients undergoing transcatheter aortic valve implantation2013In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 11, no 1, p. 5-Article in journal (Refereed)
    Abstract [en]

    Background: Aortic stenosis (AS) is a relevant common valve disorder. Severe AS and symptoms and/or left ventricular dysfunction (EF<50%) have the indication for aortic valve replacement (AVR). Majority of the patients with AS are elderly often with co-morbidities and generally have high preoperative risk. Transcatheter aortic valve implantation (TAVI) is offered in this group. Four different sizes of Corevalve prosthesis are available. Correct measurement of aortic size prior to TAVI is of great important to choose the right prosthesis size to avoid among others paravalvular leak or prosthesis patient mismatch. Aim of the study is to assess the aortic annulus diameter in patients undergoing TAVI by biplane (BP) mode using transesophageal echocardiography (TEE) and compare it to two-dimensional (2D) transthoracic echocardiography (TTE) and 2DTEE using three-dimensional (3D) TEE as reference method. Methods: The study population consisted of 50 patients retrospectively (24 men and 26 women, mean age 85 +/- 8 years of age) who all had undergone echocardiography examination prior to TAVI. Results: The mean aortic annulus diameter was 20.4 +/- 2.2 mm with TTE, 22.3 +/- 2.5 mm with 2DTEE, 22.9 +/- 1.9 mm with BP-mode and 23.1 +/- 1.9 mm with 3DTEE. TTE underestimated the mean aortic annulus diameter in comparison to transesophageal imaging modalities (p<0.001). Using 3DTEE, 2% of patients were unsuitable for TAVI due to a too-small AoA (n=1). This figure was similar with BP (4%, n=2; p=1.00) but considerably larger with 2DTTE (36%, n=18; p<0.001) and 2DTEE (12%, n=6; p=0.06). There was a strong correlation between BP-mode and 3DTEE for assessment of aortic annulus diameter (r-value 0.88) with small mean difference (-0.2 +/- 0.9 mm) whereas the other modalities showed larger 95% confidence interval and modest correlation (2DTTE vs. 3DTEE, -6.3 to 0.9 mm, r=0.64 and 2DTEE vs. 3DTEE, -4.8 to 3.2 mm, r=0.61). Conclusion: A multi-dimensional method is preferred to assess aortic annulus diameter in TAVI patients since there is risk of underestimation using single plane. Biplane mode is the method of choice in view of speedy post-processing with no need for expensive dedicated software. Lastly, single plane methods lead to misclassification of patients as unsuitable for TAVI. This may be of major clinical importance.

  • 21.
    Shahgaldi, Kambiz
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Abrahamsson, Anna
    Gudmundsson, Petri
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Winter, Reidar
    Three-dimensional echocardiography using single-heartbeat modality decreases variability in measuring left ventricular volumes and function in comparison to four-beat technique in atrial fibrillation2010In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 8, no 1Article in journal (Refereed)
    Abstract [en]

    Background: Three dimensional echocardiography (3DE) approaches the accuracy of cardiac magnetic resonance in measuring left ventricular (LV) volumes and ejection fraction (EF). The multibeat modality in comparison to single-beat (SB) requires breath-hold technique and regular heart rhythm which could limit the use of this technique in patients with atrial fibrillation (AF) due to stitching artifact. The study aimed to investigate whether SB full volume 3DE acquisition reduces inter-and intraobserver variability in assessment of LV volumes and EF in comparison to four-beat (4B) ECG-gated full volume 3DE recording in patients with AF.

    Methods: A total of 78 patients were included in this study. Fifty-five with sinus rhythm (group A) and 23 having AF (group B). 4B and SB 3DE was performed in all patients. LV volumes and EF was determined by these two modalities and inter-and intraobserver variability was analyzed.

    Results: SB modality showed significantly lower inter-and intraobserver variability in group B in comparison to 4B when measuring LV volumes and EF, except for end-systolic volume (ESV) in intraobserver analysis. There were significant differences when calculating the LV volumes (p < 0.001) and EF (p < 0.05) with SB in comparison to 4B in group B.

    Conclusion: Single-beat three-dimensional full volume acquisition seems to be superior to four-beat ECG-gated acquisition in measuring left ventricular volumes and ejection fraction in patients having atrial fibrillation. The variability is significantly lower both for ejection fraction and left ventricular volumes.

  • 22.
    Shahgaldi, Kambiz
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Winter, Reidar
    Direct measurement of left ventricular outflow tract area using three-dimensional echocardiography in biplane mode improves accuracy of stroke volume assessment2010In: Echocardiography, ISSN 0742-2822, E-ISSN 1540-8175, Vol. 27, no 9, p. 1078-1085Article in journal (Refereed)
    Abstract [en]

    Aims: The aim of the study was to investigate whether left ventricular stroke volume (LVSV) assessment using direct measurement of left ventricular outflow tract area (LVOTA) is superior to conventional methods for SV calculation. Methods and results: Thirty patients were included in the study (39 +/- 12 years). LVSV was assessed by multiplying LVOT velocity time integral (VTI) by LVOTA provided by direct plani-metrical measurements from real time three-dimensional echocardiography (RT3DE) in biplane mode (SV2). These measurements were compared to conventional methods using either the LVOT diameter for LVOTA multiplied with VTI (SV1) or biplane Simpson (SV3). Direct SV measurements by RT3DE were used as gold standard (SVref). There was an excellent correlation and agreement between SV determined by SV2 and 3DE (r = 0.98, mean difference 0.5 +/- 3.3 mL). However, the concordance of the traditional methods (SV1 and SV3) with 3DE was weaker (r = 0.38, mean difference -2.0 +/- 17.6 mL, r = 0.84, mean difference -7.6 +/- 8.7 mL, respectively). Furthermore, cardiac output (CO) measurements performed by the different modalities were not concordant with wide limits of agreement, except by SV2 the mean difference of CO by SV1 was -0.12 +/- 1.05 L/min, 0.03 +/- 0.20 L/min by SV2, and -0.45 +/- 0.52 L/min by SV3. Conclusions: SV and CO calculations using direct measurement of LVOT area is a feasible, accurate and reproducible method and correlates extremely well with 3DE volume measurements. SV and CO calculation by LVOTA is therefore an appealing method for LVSV assessment in clinical routine.

  • 23.
    Venkateshvaran, Ashwin
    et al.
    KTH, School of Technology and Health (STH).
    Sola, S.
    Govind, Satish Chandra
    KTH, School of Technology and Health (STH).
    Dash, P. K.
    Barooah, B.
    Shahgaldi, Kambiz
    KTH, School of Technology and Health (STH).
    Sahlén, Anders
    KTH, School of Technology and Health (STH).
    Lund, L.
    Winter, Reidar
    KTH, School of Technology and Health (STH).
    Nagy, A. I.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH).
    The impact of arterial load on left ventricular performance: An invasive haemodynamic study in severe mitral stenosis2015In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 593, no 8, p. 1901-1912Article in journal (Refereed)
    Abstract [en]

    Key points: A hallmark of mitral stenosis (MS) is the markedly altered left ventricular (LV) loading. As most of the methods used to determine LV performance in MS patients are influenced by loading conditions, previous studies have shown conflicting results. The present study calculated LV elastance, which is a robust method to quantify LV function. We demonstrate that LV loading in MS patients is elevated but normalizes after valve repair and might be a result of reflex pathways. Additionally, we show that the LV in MS is less compliant than normal due to a combination of right ventricular loading and the valvular disease itself. Immediately after valve dilatation the increase in blood inflow into the LV results in even greater LV stiffness. Our findings enrich our understanding of heart function in MS patients and provide a simple reproducible way of assessing LV performance in MS. Left ventricular (LV) function in rheumatic mitral stenosis (MS) remains an issue of controversy, due to load dependency of previously employed assessment methods. We investigated LV performance in MS employing relatively load-independent indices robust to the altered loading state. We studied 106 subjects (32 ± 8 years, 72% female) with severe MS (0.8 ± 0.2 cm2) and 40 age-matched controls. MS subjects underwent simultaneous bi-ventricular catheterization and transthoracic echocardiography (TTE) before and immediately after percutaneous transvenous mitral commisurotomy (PTMC). Sphygmomanometric brachial artery pressures and TTE recordings were simultaneously acquired in controls. Single-beat LV elastance (E<inf>es</inf>) was employed for LV contractility measurements. Effective arterial elastance (E<inf>a</inf>) and LV diastolic stiffness were measured. MS patients demonstrated significantly elevated afterload (E<inf>a</inf>: 3.0 ± 1.3 vs. 1.5 ± 0.3 mmHg ml-1; P < 0.001) and LV contractility (E<inf>es</inf>: 4.1 ± 1.6 vs. 2.4 ± 0.5 mmHg ml-1; P < 0.001) as compared to controls, with higher E<inf>a</inf> in subjects with smaller mitral valve area (≤ 0.8 cm2) and pronounced subvalvular fusion. Stroke volume (49 ± 16 to 57 ± 17 ml; P < 0.001) and indexed LV end-diastolic volume (LVEDV<inf>index</inf>: 57 ± 16 to 64 ± 16 ml m-2; P < 0.001) increased following PTMC while E<inf>es</inf> and E<inf>a</inf> returned to more normal levels. Elevated LV stiffness was demonstrated at baseline and increased further following PTMC. Our findings provide evidence of elevated LV contractility, increased arterial load and increased diastolic stiffness in severe MS. Following PTMC, both LV contractility and afterload tend to normalize.

  • 24.
    Westholm, Carl
    et al.
    Karolinska Institute, Sweden.
    Johnson, Jonas
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    Gunyeli, Elif
    Karolinska Institute, Sweden.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering. Karolinska Institute, Sweden.
    Jernberg, Tomas
    Lundbäck, Stig
    Winter, Reidar
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Imaging.
    The Cardiac State Index (CSI), a new timing-based diagnostic tool foridentifying patients with acute coronary syndromeManuscript (preprint) (Other academic)
1 - 24 of 24
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