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Marek Belohlavek

Publications and source records attributed to Marek Belohlavek.

At least 19 recordsLinked to original sources
PubMed2006

High-resolution ultrasound analysis of subsynovial connective tissue in human cadaver carpal tunnel.

The carpal tunnel contains the median nerve, nine flexor tendons, two synovial bursae, and peritendinous subsynovial connective tissue (SSCT). Fibrosis of the SSCT is the most consistent pathological finding in patients with carpal tunnel syndrome. We investigated the anatomy and gliding characteristics of the flexor digitorum superficialis tendon and its adjacent SSCT with high-resolution ultrasound (15 MHz). Our hypotheses were that tendon and SSCT are distinguishable by ultrasound and that their velocities during tendon excursion are different. Qualitative ultrasound analysis of a flexor tendon and its SSCT was performed on five cadaver wrists and correlated to respective findings after anatomical study of the same cadavers. Quantitative Doppler velocity analysis of eight cadaver wrists was done to assess the sliding movement of the tendon and its SSCT within the carpal tunnel. No significant difference was found between the thickness of SSCT measured by ultrasound and that measured directly after dissection. The SSCT moved slower than its flexor tendon. The SSCT velocities were statistically different from the tendon velocities (t-test, p>0.001). High-resolution ultrasound is a very precise method to display the anatomy of the tendon and SSCT within the carpal tunnel, and their different velocities can be detected with Doppler. Noninvasive assessment of the thickness and velocity of the tenosynovium in carpal tunnel syndrome by high-resolution sonography might be a new diagnostic tool for disorders affecting the SSCT, especially carpal tunnel syndrome.

Aged↗
PubMed2006

Accuracy, reproducibility, and comparability of Doppler tissue imaging by two high-end ultrasound systems.

INTRODUCTION: Doppler tissue imaging is a new technology for quantitative evaluation of myocardial motion and contractility, and is available in several ultrasound systems. This study evaluates the comparability, accuracy, and reproducibility of measurements of velocity, strain rate, and strain by two high-end ultrasound systems. METHODS: Accuracy was assessed by imaging a tissue-mimicking gelatin phantom, and the comparability of measurements in the right ventricular free wall and interventricular septum was assessed in 20 healthy participants. Reproducibility was evaluated by repeated recordings in vitro and in a random subset of patients. RESULTS: In vitro, a high degree of accuracy was found in both systems, with one system measuring slightly lower values than the reference values (mean difference 0.35 +/- 0.18 cm/s, P < .001). Values higher than the reference values were measured by both systems for strain and strain rate. In vivo, no systematic differences in measured velocities, strain rate, and strain were found; however, wide limits of agreement were seen for strain and strain rate. Measurements of tissue velocity, strain, and strain rate were well reproducible, nevertheless wide variation was found in both systems (coefficient of variation = 9%-19%). CONCLUSION: For clinical purposes, both systems have sufficient accuracy for measurements of tissue velocity. The variation in measurements of strain rate and strain by Doppler tissue imaging should be taken into account when designing studies using this new technology. Approaches to potentially reduce this variation should be addressed in future studies.

Echocardiography, Doppler↗
PubMed2006

Analysis of postsystolic myocardial thickening work in selective myocardial layers during progressive myocardial ischemia.

BACKGROUND: Myocardial function is transmurally heterogeneous. Postsystolic work may functionally reflect ischemic but viable myocardium. We calculated systolic and postsystolic regional myocardial work index (RMWi) in subendocardial and subepicardial layers of myocardium supplied by a slowly occluding coronary artery. METHODS: Progressive stenosis of the left anterior descending coronary artery lasting 11 +/- 5 days (end point) was induced in 10 dogs, and pressure-strain loops were obtained from subendocardial and subepicardial layers of apical and middle anterior segments by intracardiac ultrasound. RESULTS: At baseline, the RMWi was significantly higher (P < .05) in the subendocardial layer. At the end point, there was no significant change in the RMWi in ischemic myocardium; however, the postsystolic RMWi was higher (P < .05) in the subendocardial layer and accompanied a decrease in subendocardial myocardial blood flow, although viability was largely maintained. CONCLUSION: A significant subendocardial postsystolic RMWi at rest suggests an impending ischemic injury in coronary artery disease when segmental function is still preserved.

Animals↗
PubMed2006

An echocardiographic left ventricular wall area index for functional detection of myocardial injury in hemodynamically unloaded hearts.

Functional assessment of the left ventricle is affected by loading conditions. Detection of rejection-mediated myocardial injury in a heterotopic heart transplant model is a challenge for the echocardiographer because the heart is in an unloaded state. We examined the relationship of a novel left ventricular (LV) wall area index (LVWAI) and serum cardiac troponin T (cTnT) levels. The LVWAI, based on prior methods of determining LV mass, was defined as the difference between epicardial and endocardial areas divided by the epicardial area. The biphasic morphometric response of LVWAI reflected changes in the cTnT levels and allowed echocardiographic detection of myocardial injury in hemodynamically unloaded hearts.

Animals↗
PubMed2005

Apex-to-base dispersion in regional timing of left ventricular shortening and lengthening.

OBJECTIVES: We investigated whether the onset and progression of regional left ventricular (LV) shortening and lengthening parallel the apex-to-base differences in depolarization and repolarization. BACKGROUND: Limited information exists regarding apex-to-base differences in longitudinal and circumferential deformation sequence of the LV. METHODS: The apex-to-base differences in electric activation and the progression of longitudinal and circumferential shortening and lengthening sequences were determined in 8 porcine beating hearts in situ by implanting bipolar electrodes and an array of 14 sonomicrometry crystals in the LV free wall. RESULTS: Electric activation started at the apical subendocardium and showed significant delay in reaching the LV base. The onsets of mechanical activation and subsequent 20%, 40%, and 80% peak longitudinal shortenings required longer time to occur at base compared to the apex. The repolarization sequence propagated in reverse, with the base repolarizing before the apex. Subendocardial longitudinal shortening at base and subepicardial circumferential shortening at apex continued beyond the period of LV ejection, resulting in an apex-to-base gradient in the onset of lengthening. This gradient correlated with the duration of isovolumic relaxation (r = 0.85, p = 0.004) and the time required for reaching the lowest LV diastolic pressure (r = 0.70, p = 0.04). CONCLUSIONS: Apex-to-base delay in mechanical shortening of LV parallels the apex-to-base direction of the electric activation sequence. Basal subendocardial and apical subepicardial regions deform through a characteristic phase of postsystolic shortening. Short-lived apex-to-base and subendocardial-to-subepicardial relaxation gradients at the onset of diastole may have a physiologic significance in facilitating active restoration of the LV cavity in diastole.

Animals↗
PubMed2005

Two-dimensional acoustic pattern derived strain parameters closely correlate with one-dimensional tissue Doppler derived strain measurements.

BACKGROUND: Two-dimensional strain echocardiography (2D-SE) calculates tissue velocities via frame-to-frame tracking of unique acoustic markers within the image and provides strain parameters in two dimensions. Novel 2D-SE software allows semi-automated strain measurements and increased averaging capabilities optimizing signal-noise ratio. AIM: We tested whether 2D-SE and the currently used and well-validated tissue Doppler derived strain echocardiography (TD-SE) yield similar information in the clinical setting. METHODS AND RESULTS: We performed 2D-SE and TD-SE on 17 patients with amyloid cardiomyopathy and 10 age-matched healthy volunteers. Single walls from standard apical views (2- and 4-chamber) were acquired at high frame rates ( approximately 200fps). Offline analysis was performed by observers blinded to clinical data using the EchoPAC program with custom 2D-SE software. Longitudinal strain rate and strain from the basal, mid and apical segments of the septal and lateral walls were determined by each method (TD-SE and 2D-SE). Ejection fraction was >0.55 in healthy volunteers and ranged from 0.30 to 0.80 in cardiomyopathy group. A total of 54 walls (162 segments) were examined. Acceptable quality strain data was available in 92% and 85% segments by 2D-SE and TD-SE, respectively. Two-dimensional strain echocardiography values correlated closely with TD-SE values (r=0.94 and 0.96 for strain rate and strain, respectively). CONCLUSIONS: Deformation analysis by 2D-SE is feasible in a clinical setting and 2D-SE values correlate closely with TD-SE measurements over a wide range of global systolic function. Two-dimensional strain echocardiography may help to facilitate the routine clinical implementation of deformation analysis.

Acoustics↗
PubMed2005

Relation of tissue displacement and strain to invasively determined right ventricular stroke volume.

The role of echocardiography in the clinical assessment of right ventricular (RV) systolic function remains limited. Limited data exist on the potential use of newer techniques for RV function assessment. Conventional echocardiography and tissue Doppler echocardiography (TDE) were performed during right-sided cardiac catheterization in 46 patients. Thermodilution or the Fick-derived RV stroke volume indexed (RVSVI) indexed to body surface area was used as the reference standard. Univariate and multivariate regression analyses were used to test correlations between RVSVI and various echocardiographic and TDE-derived parameters. In a subset of 12 subjects, changes in echocardiographic and TDE variables to reduced afterload from intravenous epoprostenol were measured. TDE-derived RV tissue displacement and systolic strain best predicted the RVSVI (r = 0.63, p = 0.001; r = 0.48, p = 0.002, respectively). The prediction improved after adjustment for tricuspid regurgitation jet vena contracta width (r = 0.74, p < 0.0001; r = 0.60, p < 0.001, respectively). Assuming a RVSVI of > or =30 ml/m(2) as normal, a RV displacement cutoff of 15 mm yielded a sensitivity of 100% and a specificity of 41% for RV dysfunction, and an RV systolic strain cutoff of 20% yielded a sensitivity of 91% and a specificity of 63%. The percentage change of RV systolic displacement correlated well with the percentage change of RVSVI after epoprostenol infusion (r = 0.75, p < 0.001). In conclusion, TDE-derived RV displacement and strain closely correlate with RVSVI and appropriately track load-related changes in RV function. These new parameters may help provide the noninvasive, quantitative assessment of RV function.

Cardiac Catheterization↗
PubMed2005

Delayed onset of subendocardial diastolic thinning at rest identifies hypoperfused myocardium.

BACKGROUND: Onset of myocardial relaxation is highly energy dependent. Perfusion and therefore energy substrate delivery are predominantly reduced in the subendocardial myocardium in the early stages of progressive ischemia. We hypothesized that delayed onset of subendocardial diastolic thinning will functionally identify regionally hypoperfused resting myocardium. METHODS AND RESULTS: Progressive left anterior descending coronary artery stenosis was induced by an ameroid occluder and maintained for 1 or 2 weeks (end point) in 12 dogs. M-mode tissue Doppler images of the anterior apical and middle segments (testing region) and middle inferior segment (control region) were acquired selectively in the subendocardium and subepicardium. The time to the onset of thinning was measured with the use of tissue Doppler velocity (TOTv) and a thickness function (TOTt). At the end point in the testing region, myocardial flow was significantly lower in the subendocardial layer (P<0.05) in all animals, whereas viability staining showed preserved transmural viability in 10 dogs and thin subendocardial necrosis in 2 dogs. Both TOTv and TOTt were significantly (P<0.01) prolonged in the testing region. The mean difference between subendocardial and subepicardial TOTv values versus that in the control region identified the ischemic region, even when only dogs with hypoperfused but transmurally viable myocardium were considered (P<0.05). Systolic and diastolic myocardial velocities did not identify subendocardial hypoperfusion. CONCLUSIONS: In resting myocardium subtended to progressive coronary stenosis, a delayed onset of subendocardial thinning suggests an early stage of hypoperfusion, before the development of local wall motion abnormalities.

Animals↗
PubMed2005

Biphasic tissue Doppler waveforms during isovolumic phases are associated with asynchronous deformation of subendocardial and subepicardial layers.

Subendocardial and subepicardial layers of the left ventricle (LV) are characterized with right- and left-handed helical orientations of myocardial fibers. We investigated the origin of biphasic deformations of the LV wall during isovolumic contraction (IVC) and relaxation (IVR). In eight open-chest adult pigs, strain rates were measured along the right- and left-handed helical directions in the LV anterior wall by implanting 16 sonomicrometry crystals. Sonomicrometry strain rates were compared with the longitudinal subendocardial strain rates obtained by tissue Doppler imaging. During ejection and diastolic filling, shortening and lengthening occurred synchronously along the right- and left-handed helical directions. However, during IVC and IVR, the deformations were dissimilar in the two directions. Transmural shortening during IVC occurred along the right-handed helical direction and was accompanied with transient lengthening in the left-handed helical direction. Conversely, during IVR, the LV lengthened along the left-handed helical direction and shortened in the right-handed helical direction. Peak subendocardial strain rates obtained by tissue Doppler imaging during IVC and IVR correlated with corresponding sonomicrometry strain rate values obtained along the right- and left-handed helical directions (r = 0.81, P < 0.001 and r = 0.70, P = 0.001, respectively). Our data suggest that brief counterdirectional movements occur within the LV wall during IVC and IVR. Shortening along the right-handed helical direction is accompanied with reciprocal lengthening in the left-handed helical direction during IVC and vice versa during IVR. The results support an association between asynchronous deformation of subendocardial and subepicardial muscle fibers and the biphasic isovolumic movements observed with high-resolution tissue Doppler imaging.

Animals↗
PubMed2005

Increased right ventricular afterload induces postsystolic thickening of the ventricular septum in nonischemic hearts.

BACKGROUND: We aimed to assess whether myocardial postsystolic thickening (PST) can be induced by an acute increase in right ventricular (RV) afterload and, thus, demonstrate that PST may have a nonischemic cause. METHODS: In 8 anesthetized open-chest pigs, radial strains of the interventricular septum (IVS) and left ventricular inferolateral wall were obtained by Doppler tissue echocardiography before and during constriction of the pulmonary artery. RESULTS: After each constriction, RV peak systolic pressure increased from 30 +/- 5 to 57 +/- 8 mm Hg (P < .001). Peak systolic radial strain of the IVS decreased from 20.8% +/- 5.3% to 9.5% +/- 4.1% (P = .003), and PST of the IVS increased from 0.3% +/- 0.5% to 6.1% +/- 4.8% (P = .01). The onset of PST started 41 +/- 20 milliseconds after peak negative dP/dt of RV pressure. The inferolateral wall did not show PST. CONCLUSION: An acute increase in RV pressure causes a significant reduction in peak systolic strain of the IVS associated with the nonischemic appearance of PST.

Animals↗
PubMed2005

Two-dimensional strain--a Doppler-independent ultrasound method for quantitation of regional deformation: validation in vitro and in vivo.

BACKGROUND: A new 2-dimensional strain echocardiography (2DSE) method has been introduced that measures myocardial deformations by tracking localized acoustic markers. We compared strains measured in vitro and in vivo by 2DSE with those obtained by sonomicrometry. METHODS: For the in vitro study, a tissue-mimicking gelatin block was cyclically compressed and longitudinal strains obtained by 2DSE and sonomicrometry crystals. For the in vivo study, arrays of crystals were implanted into the apical anteroseptal (test region) and midposterior (control region) in 16 open-chest pigs and strains measured by 2DSE and crystals at baseline and after acute ischemia. RESULTS: In vitro, pooled data demonstrated good correlation (r = 0.99, P < .0001) and close agreement (bias +/- 2SD = 0.7 +/- 2.2%) of 2DSE and sonomicrometry. For a combination of low testing strains (5.4%) and strain rates (0.8 and 1.2 Hz), 2DSE overestimated strains by sonomicrometry. In vivo, linear regression analysis of pooled measurements demonstrated again a good correlation (r = 0.94, P < .0001) and agreement (1.1 +/- 7.5%) of 2DSE with sonomicrometry with a trend toward lower absolute values of strains by 2DSE. CONCLUSION: The 2DSE demonstrated good overall correlation and agreement with sonomicrometry for the tested in vitro and in vivo values. Some caution with 2DSE measurements is needed for combinations of low strains and strain rates.

Animals↗
PubMed2005

Analysis of the interaction between segmental relaxation patterns and global diastolic function by strain echocardiography.

BACKGROUND: Strain echocardiography can depict segmental mechanical activity with high temporal and spatial accuracy, and may allow assessment of segmental relaxation not possible with conventional echocardiography. METHODS: Conventional and strain echocardiography were performed in healthy volunteers (young [group 1] and old [group 2]) and patients with normal 2-dimensional and stress echocardiography, with either normal global diastolic function (group 3a) or grade I or II global diastolic dysfunction (DD) (group 3b). Standard echocardiography criteria were used to define global DD. Early to late diastolic strain rate ratio less than 1.1 was defined as altered segmental relaxation. RESULTS: All participants had normal wall motion and ejection fraction. Participants of group 1 had normal segmental and global diastolic function. Participants of groups 2 and 3a demonstrated a wide range of altered segmental relaxation in the absence of global DD. All patients of group 3b had 12 or more segments with altered relaxation and global DD. Age and hypertension were associated with a larger number of altered segments, a lower mean early to late diastolic strain rate ratio, and global DD. CONCLUSIONS: A wide range of altered segmental relaxation can exist in the absence of global DD. Age and hypertension are associated with altered segmental relaxation and global DD. Assessment of segmental relaxation may be beneficial in the elderly and patients with hypertension.

Adult↗
PubMed2004

Left atrial myopathy in cardiac amyloidosis: implications of novel echocardiographic techniques.

AIMS: To assess left atrial (LA) function and determine the prevalence of LA dysfunction in AL amyloidosis (AL) using conventional and strain echocardiography. METHODS AND RESULTS: LA ejection fraction, LA filling fraction, LA ejection force, peak LA systolic strain rate (LAsSR), and LA systolic strain (LA epsilon) were determined in 95 AL patients (70 with and 25 without echocardiographic evidence of cardiac involvement, abbreviated CAL and NCAL, respectively), 30 age-matched controls (CON), and 20 patients with diastolic dysfunction and LA dilatation (DD). Peak LAsSR >2 standard deviations below mean CON value was used as the cut-off for normal LA function. LA ejection fraction was lower in CAL when compared with CON (40.4+/-13.6 vs. 67.0+/-6%, P=0.01). Left atrial septal strain rate and strain were lower in CAL (0.8+/-0.5 s(-1) and 5.5+/-4%, respectively) compared with CON (1.8+/-0.8 s(-1) and 14+/-4%, respectively, P=<0.0001), NCAL (1.6+/-0.8 s(-1) and 13+/-7%, respectively, P<0.0001) and DD (1.3+/-0.4 s(-1) and 10+/-2%, respectively, P<0.0001). Based on peak LA systolic strain rate criteria, the cut-off values for normal LA function were -1.1 s(-1) and -1.05 s(-1) for lateral and septal walls. Using these criteria, LA dysfunction was identified in 32% (lateral LA criteria) and 60% (septal LA criteria) of CAL patients. Lateral and septal LAsSR were lower in CAL patients with vs. those without symptoms of heart failure. Inter- and intra-observer agreement was high for LA strain echocardiography. CONCLUSION: LA function assessment using strain echocardiography is feasible with low intra- and inter-observer variability. LA dysfunction is observed in AL patients without other echocardiographic features of cardiac involvement and may contribute to cardiac symptoms in CAL.

Aged↗
PubMed2004

Strain echocardiography tracks dobutamine-induced decrease in regional myocardial perfusion in nonocclusive coronary stenosis.

OBJECTIVES: This study was designed to determine whether strain echocardiography parameters reflect changes in regional myocardial perfusion during dobutamine stress. BACKGROUND: Strain echocardiography depicts regional myocardial mechanical activity. Ischemia has been shown to reduce systolic strain rate (sSR) and prolong the time to regional lengthening (T(RL)). In an experimental model, we tested whether sSR and T(RL) tracked dobutamine-induced changes in regional myocardial perfusion (regional myocardial blood flow [RMBF]), as measured by colored microspheres. METHODS: We used a closed-chest pig model of nonocclusive coronary stenosis (n = 14) created by inflating an angioplasty balloon in the proximal left anterior descending artery. Invasive hemodynamics, RMBF, and strain parameters were measured at baseline and peak dobutamine stimulation before and during the coronary stenosis. We compared segments with reduced RMBF versus those with preserved RMBF at peak dobutamine stimulation. RESULTS: Peak sSR correlated with RMBF (r = 0.70). In the absence of coronary stenosis, dobutamine stimulation caused a significant increase in RMBF and sSR and a decrease in T(RL). This response was blunted during coronary stenosis. Using the "best cutoff" method, the sensitivity and specificity for prediction of reduced RMBF (ischemia) was 81% and 91% for sSR and 65% and 91% for T(RL), respectively. These changes occurred in the absence of any change in global systolic and diastolic function (dP/dT(max), dP/dT(min), and tau). CONCLUSIONS: Novel strain parameters that depict regional myocardial mechanics are able to predict changes in RMBF during dobutamine stress. Quantitative strain parameters may complement current echocardiographic techniques for ischemia detection and potentially improve the accuracy and reproducibility of stress echocardiography.

Animals↗
PubMed2004

Strain rate and strain: a step-by-step approach to image and data acquisition.

The advent of strain and strain rate imaging in clinical echocardiography prompted an examination of proper techniques for image acquisition and analysis. For this promising and relatively new method of assessing myocardial performance to be successful in diagnostic echocardiography, close adherence to a standardized method is imperative. This article provides the echocardiographer with a step-by-step approach.

Algorithms↗
PubMed2004

Both systolic and diastolic dysfunction characterize nonischemic inhibition of myocardial energy metabolism: an experimental strain rate echocardiographic study.

BACKGROUND: Ischemia is primarily a metabolic event. However, regional functional changes can be affected by structural alterations. We developed an experimental model of sole myocardial energy metabolism inhibition and characterized the resulting regional dysfunction. METHODS: In 12 pigs, we regionally inhibited creatine kinase (CK) and, consequently, myocyte high-energy phosphate transfer by intracoronary administration of iodoacetamide. Myocardial biopsies for CK activity and structural analyses and strain rate (SR) echocardiography scans were obtained at baseline and 60 minutes after iodoacetamide administration. Plasma levels of the CK isoenzyme MB and troponin I were assessed to determine possible myocardial damage. RESULTS: CK activity in the iodoacetamide-perfused myocardium decreased to 0.5% of the original value and was accompanied by a reduction in peak systolic SR ( P < .0001), end-systolic strain ( P < .0001), and peak SRs of myocardial early and late filling waves ( P < .0001). Microscopy showed contracture without sarcomere disruption. Plasma levels of CK isoenzyme MB and troponin I did not change. CONCLUSIONS: Regional inhibition of myocyte energetics leads to both systolic and diastolic dysfunction by SR echocardiography, but the presence of a residual phosphotransfer protects microstructural integrity.

Animals↗