Regional left ventricular mechanics in hypertrophic cardiomyopathy

Characterization of motion patterns by a spatio-temporal saliency descriptor in cardiac cine MRI

BACKGROUND AND OBJECTIVE

Abnormalities of the heart motion reveal the presence of a disease. However, a quantitative interpretation of the motion is still a challenge due to the complex dynamics of the heart. This work proposes a quantitative characterization of regional cardiac motion patterns in cine magnetic resonance imaging (MRI) by a novel spatio-temporal saliency descriptor.

METHOD

The strategy starts by dividing the cardiac sequence into a progression of scales which are in due turn mapped to a feature space of regional orientation changes, mimicking the multi-resolution decomposition of oriented primitive changes of visual systems. These changes are estimated as the difference between a particular time and the rest of the sequence. This decomposition is then temporarily and regionally integrated for a particular orientation and then for the set of different orientations. A final spatio-temporal 4D saliency map is obtained as the summation of the previously integrated information for the available scales. The saliency dispersion of this map was computed in standard cardiac locations as a measure of the regional motion pattern and was applied to discriminate control and hypertrophic cardiomyopathy (HCM) subjects during the diastolic phase.

RESULTS

Salient motion patterns were estimated from an experimental set, which consisted of 3D sequences acquired by MRI from 108 subjects (33 control, 35 HCM, 20 dilated cardiomyopathy (DCM), and 20 myocardial infarction (MINF) from heterogeneous datasets). HCM and control subjects were classified by an SVM that learned the salient motion patterns estimated from the presented strategy, by achieving a 94% AUC. In addition, statistical differences (test t-student, p<0.05) were found among groups of disease in the septal and anterior ventricular segments at both the ED and ES, with salient motion characteristics aligned with existing knowledge on the diseases.

CONCLUSIONS

Regional wall motion abnormality in the apical, anterior, basal, and inferior segments was associated with the saliency dispersion in HCM, DCM, and MINF compared to healthy controls during the systolic and diastolic phases. This saliency analysis may be used to detect subtle changes in heart function.

The Role of New Imaging Technologies in the Diagnosis of Cardiac Amyloidosis

Cardiac amyloidosis is an infiltrative disorder caused by transthyretin or immunoglobulin free light-chain deposition, which determines clinical disease with similar phenotype but different time course, prognosis and therapy. Multimodality imaging is the cornerstone for disease diagnosis and management. Multimodality imaging has revolutionized the approach to the disease favoring its awareness and simplifying its diagnosis, especially in ATTR cardiac amyloidosis. This describes the different imaging tools, from the traditional to the more novel ones, and highlights the different approach in each different setting (prognosis, subtyping, prognosis, monitoring disease progression, and response to therapy).

Ion Channel Impairment and Myofilament Ca2+ Sensitization: Two Parallel Mechanisms Underlying Arrhythmogenesis in Hypertrophic Cardiomyopathy

Life-threatening ventricular arrhythmias are the main clinical burden in patients with hypertrophic cardiomyopathy (HCM), and frequently occur in young patients with mild structural disease. While massive hypertrophy, fibrosis and microvascular ischemia are the main mechanisms underlying sustained reentry-based ventricular arrhythmias in advanced HCM, cardiomyocyte-based functional arrhythmogenic mechanisms are likely prevalent at earlier stages of the disease. In this review, we will describe studies conducted in human surgical samples from HCM patients, transgenic animal models and human cultured cell lines derived from induced pluripotent stem cells. Current pieces of evidence concur to attribute the increased risk of ventricular arrhythmias in early HCM to different cellular mechanisms. The increase of late sodium current and L-type calcium current is an early observation in HCM, which follows post-translation channel modifications and increases the occurrence of early and delayed afterdepolarizations. Increased myofilament Ca²⁺ sensitivity, commonly observed in HCM, may promote afterdepolarizations and reentry arrhythmias with direct mechanisms. Decrease of K⁺-currents due to transcriptional regulation occurs in the advanced disease and contributes to reducing the repolarization-reserve and increasing the early afterdepolarizations (EADs). The presented evidence supports the idea that patients with early-stage HCM should be considered and managed as subjects with an acquired channelopathy rather than with a structural cardiac disease.

Preoperative left ventricular longitudinal strain predicts outcome of septal myectomy for obstructive hypertrophic cardiomyopathy

OBJECTIVE

The objective of this study was to determine the characteristics of longitudinal strain and its effect on outcomes in patients with obstructive hypertrophic cardiomyopathy (HCM) who underwent septal myectomy.

METHODS

We reviewed patients with obstructive HCM who underwent septal myectomy at our clinic from 2007 to 2016. Data of those who had strain echocardiography within 6 months before isolated myectomy were analyzed.

RESULTS

The median age of the 857 patients studied was 55 (interquartile range [IQR], 44-63) years, and 451 (52.6%) were male. Left ventricular ejection fraction was 71% (IQR, 67%-74%), and the resting peak outflow tract gradient was 58 (IQR, 27-85) mm Hg. The median global longitudinal strain (GLS) was -14.6% (IQR, -12.0% to -17.3%). Regional longitudinal strain was nonuniform as reflected by more normal values in apical segments and more abnormal in basal segments. Moreover, GLS correlated poorly with ejection fraction and outflow tract gradient. In 64 patients who had postoperative strain echocardiography, GLS was comparable before and after septal myectomy, but regional strain was more uniform after myectomy. Over a follow-up of 8.3 (IQR, 6.5-10.3) years, when patients were equally stratified according to GLS (cutoff, -14.64%), the group with worse GLS had significantly poorer survival compared with the better GLS group (P = .002). Left ventricular ejection fraction had no association with survival.

CONCLUSIONS

Left ventricular longitudinal strain is nonuniform and might be significantly reduced in patients with obstructive HCM. Septal myectomy does not impair GLS but is associated with more uniform regional strains. Most importantly, reduced GLS preoperatively is strongly and independently associated with increased all-cause mortality after septal myectomy for obstructive HCM.

Diagnostic value of the novel CMR parameter "myocardial transit-time" (MyoTT) for the assessment of microvascular changes in cardiac amyloidosis and hypertrophic cardiomyopathy

BACKGROUND

Coronary microvascular dysfunction (CMD) is present in various non-ischemic cardiomyopathies and in particular in those with left-ventricular hypertrophy. This study evaluated the diagnostic value of the novel cardiovascular magnetic resonance (CMR) parameter "myocardial transit-time" (MyoTT) in distinguishing cardiac amyloidosis from other hypertrophic cardiomyopathies.

METHODS

N = 20 patients with biopsy-proven cardiac amyloidosis (CA), N = 20 patients with known hypertrophic cardiomyopathy (HCM), and N = 20 control patients without relevant cardiac disease underwent dedicated CMR studies on a 1.5-T MR scanner. The CMR protocol comprised cine and late-gadolinium-enhancement (LGE) imaging as well as first-pass perfusion acquisitions at rest for MyoTT measurement. MyoTT was defined as the blood circulation time from the orifice of the coronary arteries to the pooling in the coronary sinus (CS) reflecting the transit-time of gadolinium in the myocardial microvasculature.

RESULTS

MyoTT was significantly prolonged in patients with CA compared to both groups: 14.8 ± 4.1 s in CA vs. 12.2 ± 2.5 s in HCM (p = 0.043) vs. 7.2 ± 2.6 s in controls (p < 0.001). Native T1 and extracellular volume (ECV) were significantly higher in CA compared to HCM and controls (p < 0.001). Both parameters were associated with a higher diagnostic accuracy in predicting the presence of CA compared to MyoTT: area under the curve (AUC) for native T1 = 0.93 (95% confidence interval (CI) = 0.83-1.00; p < 0.001) and AUC for ECV = 0.95 (95% CI = 0.88-1.00; p < 0.001)-compared to the AUC for MyoTT = 0.76 (95% CI = 0.60-0.92; p = 0.008). In contrast, MyoTT performed better than all other CMR parameters in differentiating HCM from controls (AUC for MyoTT = 0.93; 95% CI = 0.81-1.00; p = 0.003 vs. AUC for native T1 = 0.69; 95% CI = 0.44-0.93; p = 0.20 vs. AUC for ECV = 0.85; 95% CI = 0.66-1.00; p = 0.017).

CONCLUSION

The relative severity of CMD (measured by MyoTT) in relationship to extracellular changes (measured by native T1 and/or ECV) is more pronounced in HCM compared to CA-in spite of a higher absolute MyoTT value in CA patients. Hence, MyoTT may improve our understanding of the interplay between extracellular/intracellular and intravasal changes that occur in the myocardium during the disease course of different cardiomyopathies.

Biventricular pacemaker therapy improves exercise capacity in patients with non-obstructive hypertrophic cardiomyopathy via augmented diastolic filling on exercise

AIMS

Treatment options for patients with non-obstructive hypertrophic cardiomyopathy (HCM) are limited. We sought to determine whether biventricular (BiV) pacing improves exercise capacity in HCM patients, and whether this is via augmented diastolic filling.

METHODS AND RESULTS

Thirty-one patients with symptomatic non-obstructive HCM were enrolled. Following device implantation, patients underwent detailed assessment of exercise diastolic filling using radionuclide ventriculography in BiV and sham pacing modes. Patients then entered an 8-month crossover study of BiV and sham pacing in random order, to assess the effect on exercise capacity [peak oxygen consumption (VO₂ )]. Patients were grouped on pre-specified analysis according to whether left ventricular end-diastolic volume increased (+LVEDV) or was unchanged/decreased (-LVEDV) with exercise at baseline. Twenty-nine patients (20 male, mean age 55 years) completed the study. There were 14 +LVEDV patients and 15 -LVEDV patients. Baseline peak VO₂ was lower in -LVEDV patients vs. +LVEDV patients (16.2 ± 0.9 vs. 19.9 ± 1.1 mL/kg/min, P = 0.04). BiV pacing significantly increased exercise ΔLVEDV (P = 0.004) and Δstroke volume (P = 0.008) in -LVEDV patients, but not in +LVEDV patients. Left ventricular ejection fraction and end-systolic elastance did not increase with BiV pacing in either group. This translated into significantly greater improvements in exercise capacity (peak VO₂  + 1.4 mL/kg/min, P = 0.03) and quality of life scores (P = 0.02) in -LVEDV patients during the crossover study. There was no effect on left ventricular mechanical dyssynchrony in either group.

CONCLUSION

Symptomatic patients with non-obstructive HCM may benefit from BiV pacing via augmentation of diastolic filling on exercise rather than contractile improvement. This may be due to relief of diastolic ventricular interaction.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT00504647.

Hypertrophic Cardiomyopathy: A Vicious Cycle Triggered by Sarcomere Mutations and Secondary Disease Hits

Significance: Hypertrophic cardiomyopathy (HCM) is a cardiac genetic disease characterized by left ventricular hypertrophy, diastolic dysfunction, and myocardial disarray. Disease onset occurs between 20 and 50 years of age, thus affecting patients in the prime of their life. HCM is caused by mutations in sarcomere proteins, the contractile building blocks of the heart. Despite increased knowledge of causal mutations, the exact path from genetic defect leading to cardiomyopathy is complex and involves additional disease hits. Recent Advances: Laboratory-based studies indicate that HCM development not only depends on the primary sarcomere impairment caused by the mutation but also on secondary disease-related alterations in the heart. Here we propose a vicious mutation-induced disease cycle, in which a mutation-induced energy depletion alters cellular metabolism with increased mitochondrial work, which triggers secondary disease modifiers that will worsen disease and ultimately lead to end-stage HCM. Critical Issues: Evidence shows excessive cellular reactive oxygen species (ROS) in HCM patients and HCM animal models. Oxidative stress markers are increased in the heart (oxidized proteins, DNA, and lipids) and serum of HCM patients. In addition, increased mitochondrial ROS production and changes in endogenous antioxidants are reported in HCM. Mutant sarcomeric protein may drive excessive levels of cardiac ROS via changes in cardiac efficiency and metabolism, mitochondrial activation and/or dysfunction, impaired protein quality control, and microvascular dysfunction. Future Directions: Interventions restoring metabolism, mitochondrial function, and improved ROS balance may be promising therapeutic approaches. We discuss the effects of current HCM pharmacological therapies and potential future therapies to prevent and reverse HCM. Antioxid. Redox Signal. 31, 318-358.

Energetic drain driving hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common form of hereditary cardiomyopathy and is mainly caused by mutations of genes encoding cardiac sarcomeric proteins. HCM is characterized by hypertrophy of the left ventricle, frequently involving the septum, that is not explained solely by loading conditions. HCM has a heterogeneous clinical profile, but diastolic dysfunction and ventricular arrhythmias represent two dominant features of the disease. Preclinical evidence indicates that the enhanced Calcium (Ca²⁺ ) sensitivity of the myofilaments plays a key role in the pathophysiology of HCM. Notably, this is not always a direct consequence of sarcomeric mutations, but can also result from secondary mutation-driven alterations. Here, we review experimental and clinical evidence indicating that increased myofilament Ca²⁺ sensitivity lies upstream of numerous cellular derangements which potentially contribute to the progression of HCM toward heart failure and sudden cardiac death.

Development and validation of a new method to diagnose apical hypertrophic cardiomyopathy by gated single-photon emission computed tomography myocardial perfusion imaging

AIM

The aim of this study is to develop and validate a new method to diagnose apical hypertrophic cardiomyopathy (AHCM) by the integral quantitative analysis of myocardial perfusion and wall thickening from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI).

PATIENTS AND METHODS

Twenty-two consecutive patients, who showed T wave inversion of at least 3 mm in precordial leads and sinus rhythm in ECG, were enrolled. All the patients underwent cardiac magnetic resonance (CMR), gated rest SPECT MPI and echocardiography. According to CMR diagnostic results, 13 patients were categorized as in the AHCM group and the remaining nine patients were categorized as in the non-AHCM group. Operators who were blinded to the CMR diagnosis independently performed the diagnosis by gated SPECT MPI. The regions of interest inside the apical hotspots on the perfusion polar map were drawn and the mean values of wall thickening in the drawn region of interests were calculated. Using MRI diagnosis as the gold standard, AHCM was diagnosed based on receiver operating characteristic analysis of the mean wall thickening in the apical perfusion hotspot. The area under curve, sensitivity, specificity, and accuracy of our method were 0.97, 100%, 89%, and 95%, respectively.

CONCLUSION

Our new method has high sensitivity, specificity, and accuracy against CMR diagnosis. It has great promise to become a clinical tool in the diagnosis of AHCM.

Age-related changes in familial hypertrophic cardiomyopathy phenotype in transgenic mice and humans

β-myosin heavy chain mutations are the most frequently identified basis for hypertrophic cardiomyopathy (HCM). A transgenic mouse model (αMHC(403)) has been extensively used to study various mechanistic aspects of HCM. There is general skepticism whether mouse and human disease features are similar. Herein we compare morphologic and functional characteristics, and disease evolution, in a transgenic mouse and a single family with a MHC mutation. Ten male αMHC(403) transgenic mice (at t-5 weeks, -12 weeks, and -24 weeks) and 10 HCM patients from the same family with a β-myosin heavy chain mutation were enrolled. Morphometric, conventional echocardiographic, tissue Doppler and strain analytic characteristics of transgenic mice and HCM patients were assessed. Ten male transgenic mice (αMHC(403)) were examined at ages -5 weeks, -12 weeks, and -24 weeks. In the transgenic mice, aging was associated with a significant increase in septal (0.59±0.06 vs. 0.64±0.05 vs. 0.69±0.11 mm, P<0.01) and anterior wall thickness (0.58±0.1 vs. 0.62±0.07 vs. 0.80±0.16 mm, P<0.001), which was coincident with a significant decrease in circumferential strain (-22%±4% vs. -20%±3% vs. -19%±3%, P=0.03), global longitudinal strain (-19%±3% vs. -17%±2% vs. -16%±3%, P=0.001) and E/A ratio (1.9±0.3 vs. 1.7±0.3 vs. 1.4±0.3, P=0.01). The HCM patients were classified into 1st generation (n=6; mean age 53±6 years), and 2nd generation (n=4; mean age 32±8 years). Septal thickness (2.2±0.9 vs. 1.4±0.1 cm, P<0.05), left atrial (LA) volume (62±16 vs. 41±5 mL, P=0.03), E/A ratio (0.77±0.21 vs. 1.1±0.1, P=0.01), E/e' ratio (25±10 vs. 12±2, P=0.03), global left ventricular (LV) strain (-14%±3% vs. -20%±3%, P=0.01) and global LV early diastolic strain rate (0.76±0.17 s(-1) vs. 1.3±0.2 s-1, P=0.01) were significantly worse in the older generation. In β-myosin heavy chain mutations, transgenic mice and humans have similar progression in morphologic and functional abnormalities. The αMHC(403) transgenic mouse model closely recapitulates human disease.

Early diastolic function during exertion influences exercise intolerance in patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) patients with preserved left ventricular ejection fraction (LVEF) often develop dyspnea and exercise intolerance. Diastolic dysfunction may contribute to exercise intolerance in these patients. This study aimed to clarify our hypothesis as to whether diastolic function rather than systolic function would be associated with exercise intolerance in HCM using two-dimensional (2D) speckle tracking echocardiography during exercise.

METHODS

Thirty-three HCM patients (mean age 59.3 ± 15.7 years) underwent 2D speckle tracking echocardiography at rest and during submaximal semi-supine bicycle exercise. Global longitudinal strain (LS), LS rate during systole (LSRs), early diastole (LSRe), and late diastole (LSRa) were measured. The symptom-limited cardiopulmonary exercise testing was performed using a cycle ergometer for measuring the peak oxygen consumption (peak [Formula: see text]).

RESULTS

In the multivariate linear regression analysis, peak [Formula: see text] did not associate with strain or strain rate at rest. However, peak [Formula: see text] correlated with LS (β = -0.403, p = 0.007), LSRe (β = 6.041, p = 0.001), and LSRa (β = 5.117, p = 0.021) during exercise after adjustment for age, gender, and heart rate. The first quartile peak [Formula: see text] (14.2 mL/min/kg) was assessed to predict exercise intolerance. The C-statistic of delta LSRe was 0.74, which was relatively greater than that of delta LS (0.70) and delta LSRa (0.58), indicating that early diastolic function rather than systolic and late diastolic function affects exercise intolerance.

CONCLUSIONS

LSRe during exercise is closely associated with the peak [Formula: see text]. Early diastolic function during exercise is an important determinant of exercise capacity in patients with HCM.

Pacing tachycardia exaggerates left ventricular diastolic dysfunction but not systolic function and regional asynergy or asynchrony in patients with hypertrophic cardiomyopathy

AIMS

Myocardial ischaemia and angina have been demonstrated in patients with hypertrophic cardiomyopathy (HCM). We hypothesized that left ventricular (LV) systolic or diastolic dysfunction would be provocated by pacing tachycardia in patients with HCM.

METHODS AND RESULTS

We investigated LV global and regional systolic and diastolic function in 17 patients with HCM without LV outflow obstruction and 7 normal subjects by analysing LV angiograms and simultaneously obtained high-fidelity LV pressures before and after rapid cardiac pacing (150 b.p.m.). Biplane LV silhouettes were digitized frame by frame (50 frames/s). To quantify regional dynamics, the ventricular area of the right anterior oblique projection was divided into six sections originating from the midpoint of the long axis at end-diastole. There were no significant changes in LV function after pacing in normal subjects. In HCM, the ejection fractions remained unchanged. However, LV end-diastolic pressures rose (+12 mmHg, P < 0.01), and the time constants of isovolumic pressure decay were significantly increased (T(1/2): +5.2 ms, P < 0.01; T(1/)(e): +6.8 ms, P < 0.01). The LV global diastolic pressure-volume relationships and regional diastolic pressure-area relationships of regional myocardium shifted upward (indicating decreased diastolic distensibility) in all patients. These diastolic abnormalities were not accompanied by regional asynchrony or asynergy.

CONCLUSION

Most patients with HCM have a reduced reactive capacity to chronotropic stress, which is haemodynamically characterized by evenly distributed diastolic dysfunction. In contrast with coronary artery disease, these diastolic abnormalities were not accompanied by systolic dysfunction, regional asynchrony, asynergy, or inhomogenous diastolic distensibility.

Left ventricular strain and untwist in hypertrophic cardiomyopathy: relation to exercise capacity

Background

Nonobstructive hypertrophic cardiomyopathy (nHCM) is often associated with reduced exercise capacity despite hyperdynamic systolic function as measured by left ventricular ejection fraction. We sought to examine the importance of left ventricular strain, twist, and untwist as predictors of exercise capacity in nHCM patients.

Methods

Fifty-six nHCM patients (31 male and mean age of 52 years) and 43 age- and gender-matched controls were enrolled. We measured peak oxygen consumption (peak Vo₂) and acquired standard echocardiographic images in all participants. Two-dimensional speckle tracking was applied to measure rotation, twist, untwist rate, strain, and strain rate.

Results

The nHCM patients exhibited marked exercise limitation compared with controls (peak Vo₂ 23.28 ± 6.31 vs 37.70 ± 7.99 mL/[kg min], P < .0001). Left ventricular ejection fraction in nHCM patients and controls was similar (62.76% ± 9.05% vs 62.48% ± 5.82%, P = .86). Longitudinal, radial, and circumferential strain and strain rate were all significantly reduced in nHCM patients compared with controls. There was a significant delay in 25% of untwist in nHCM compared with controls. Both systolic and diastolic apical rotation rates were lower in nHCM patients. Longitudinal systolic and diastolic strain rate correlated significantly with peak Vo₂ (r = −0.34, P = .01 and r = 0.36, P = .006, respectively). Twenty-five percent untwist correlated significantly with peak Vo₂ (r = 0.36, P = .006).

Conclusions

In nHCM patients, there are widespread abnormalities of both systolic and diastolic function. Reduced strain and delayed untwist contribute significantly to exercise limitation in nHCM patients.

Echocardiography in patients with hypertrophic cardiomyopathy: usefulness of old and new techniques in the diagnosis and pathophysiological assessment

Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiomyopathy. The identification of patients with HCM is sometimes still a challenge. Moreover, the pathophysiology of the disease is complex because of left ventricular hyper-contractile state, diastolic dysfunction, ischemia and obstruction which can be coexistent in the same patient. In this review, we discuss the current and emerging echocardiographic methodology that can help physicians in the correct diagnostic and pathophysiological assessment of patients with HCM.

Therapeutic strategies for diastolic dysfunction: a clinical perspective

Diastolic dysfunction, which is increasingly viewed as being influential in precipitating heart failure and determining prognosis, is often unrecognized and has therapeutic implications distinct from those that occur with systolic dysfunction. In this review, several therapeutic modalities including pharmacologic, nonpharmacologic, and surgical approaches for primary diastolic dysfunction and heart failure will be discussed.

Right ventricular diastolic dysfunction in patients with left ventricular hypertrophy: analysis of right ventricular myocardial relaxation using two-dimensional speckle tracking imaging

BACKGROUND

Although several previous studies have suggested the presence of right ventricular (RV) diastolic dysfunction in patients with hypertrophic cardiomyopathy (HCM) and those with hypertensive left ventricular hypertrophy (HT-LVH), the mechanisms are still unclear. This study aimed to clarify the relationship between the RV global diastolic dysfunction in these patients and the regional myocardial diastolic function, including synchronicity of the interventricular septum and RV free wall.

METHODS

In 20 age-matched patients with HT-LVH, 20 patients with HCM and 22 control subjects without pulmonary hypertension, RV isovolumic relaxation time (IRTR) was measured using continuous-wave Doppler echocardiography. The early diastolic peak strain rate (E SR) and time from QRS to E SR (T-E SR) were measured in the apical, mid-ventricular and basal segments of the interventricular septum and RV free wall using two-dimensional speckle tracking imaging (2DST).

RESULTS

IRTR was more prolonged both in HT-LVH and in HCM than in the controls. The averaged septal E SR was reduced both in HT-LVH and in HCM (P < 0.0001, respectively), but the averaged RV free wall E SR was decreased only in HCM (P = 0.0007). E SR averaged for six septal and RV free wall segments was correlated with IRTR (r = -0.46, P = 0.0001). Neither intergroup difference nor correlation with IRTR was observed in a coefficient of variation of T-E SR for the six segments.

CONCLUSIONS

RV global diastolic function is impaired in patients with HT-LVH and HCM due to relaxation abnormalities, not an asynchrony, of the myocardium surrounding the RV cavity. The detection of RV free wall relaxation abnormality using 2DST may be useful to differentiate HCM from HT-LVH.

Effects of exercise on the duration of diastole and on interventricular phase differences in patients with hypertrophic cardiomyopathy: relationship to cardiac output reserve

BACKGROUND

Our study sought to characterize the effect of exercise on the duration of left ventricular (LV) diastole and interventricular dyssynchrony in patients with hypertrophic cardiomyopathy (HCM). We hypothesized that an abnormally shortened diastolic time may adversely affect cardiac performance.

METHODS

We studied 49 symptomatic patients with HCM during incremental exercise. Twenty-nine patients had obstructive disease (HOCM) and 20 no resting or provocable gradient (HNCM). Right heart catheterization and high temporal resolution radionuclide angiography were simultaneously performed. The loss of diastolic time per beat (LDT(RR)) was quantified using a regression equation obtained from a healthy control group (n = 30).

RESULTS

During rest and peak exercise, a significant shortening of the relative duration of LV diastole (35.6 +/- 5 vs. 38.0 +/- 3 s/min and 29.3 +/- 6 vs. 32.4 +/- 3 s/min; P < or = .02) and an increased interventricular phase delay were evident in patients with HOCM compared to controls. Baseline and peak exercise LDT(RR) values were inversely related to cardiac output reserve and exercise duration. In multivariate analysis, LDT(RR) at peak exercise was identified as an independent predictor of cardiac output reserve.

CONCLUSIONS

In HOCM, baseline abnormalities of the relative duration of LV systolic and diastolic time aggravate during exercise. The disproportionate shortening of diastolic time may significantly impair cardiac efficiency by restricting diastolic filling.

Validity of ejection fraction as a measure of myocardial functional state: impact of asynchrony

AIMS

The goal of this study was to test whether peculiarities of left ventricular (LV) regional function place limits on the validity of ejection fraction (EF) as a measure of the myocardial functional state.

METHODS AND RESULTS

Transthoracic and transoesophageal data from patients with a variety of cardiac conditions were used for analysis of LV regional function. The focus was on the effects of mechanical asynchrony. Ejection fraction was calculated on the basis of LV end-diastolic volume and end-systolic volume obtained by two different ways: (i) end-systolic volume as a whole; and (ii) the sum of all regional end-systolic volumes (which may occur at different times). The relative difference, D-EF, between EFs obtained by (i) and (ii) was taken as the 'merit' of EF. A value of zero is the highest merit. Irrespective of the examination method, we found that D-EF was always higher than zero, and that its value depended on the extent of mechanical asynchrony.

CONCLUSIONS

Ejection fraction is not the arithmetic average of regional EFs. An increase of asynchrony increases D-EF, i.e. it reduces the merit of EF as a measure of cardiac function.

Elucidation of spatially distinct compensatory mechanisms in diastole: radial compensation for impaired longitudinal filling in left ventricular hypertrophy

Cardiac output maintenance is so fundamental that, when regional systolic function is impaired, as during ischemia, nonischemic segments compensate by becoming hypercontractile. By analogy, diastolic compensatory mechanisms that maintain filling volume must exist but remain to be fully elucidated. Viewing filling in spatially distinct (longitudinal, radial) mechanistic terms facilitates elucidation of diastolic compensatory mechanisms. Because impairment of longitudinal (long axis) diastolic function (DF) in left ventricular hypertrophy (LVH) is established, we hypothesized that to maintain filling volume, radial (short-axis) filling function would compensate. In 20 normal left ventricular ejection fraction (LVEF) subjects (10 with LVH, 10 without LVH), we analyzed longitudinal function via Doppler tissue imaging of mitral annular motion and radial function as change in short-axis endocardial dimension via M-mode. The spatial (long axis, short axis) endocardial LV dimensions and their changes allowed assignment of E-wave filling volume into (cylindrical geometry-based) longitudinal and radial components. Despite indistinguishable (P = 0.70) E-wave velocity-time integrals (E-wave filling volume surrogate), systolic stroke volumes, and end-diastolic volumes in the LVH and control groups, longitudinal volume in absolute terms and the percent of E-wave volume accommodated longitudinally were reduced in the LVH group (P < 0.05 and P < 0.01, respectively), whereas the percent of E-wave volume accommodated radially was enhanced (P < 0.01). We conclude that, in normal LVEF (decreased longitudinal volume accommodation) LVH subjects vs. controls, spatially distinct compensatory mechanisms in diastole manifest as increased radial volume accommodation per unit of E-wave filling volume. Assessment of spatially distinct diastolic compensatory mechanisms in other pathophysiological subsets is warranted.

Effect of hypertrophy on left ventricular diastolic function in patients with hypertrophic cardiomyopathy

Background.

Hypertrophic cardiomyopathy (HCM) is characterized by asymmetric LV hypertrophy (LVH) and impairment in diastolic function. We assess the relationship between LVH and invasive indexes of diastolic function.

Methods.

21 HCM patients underwent cardiac catheterization to assess pulmonary capillary wedge pressure, LV end-diastolic pressure (measured by microtip catheters), and LV volumes (calculated by simultaneous radionuclide angiography). We calculated from LV pressure the time constant of isovolumetric relaxation (τ, variable asymptote method, ms), and from LV pressure and volume the constant of chamber stiffness (k, ml⁻¹). LVH was assessed by different indexes: maximal wall thickness, number of hypertrophied LV segments, LVH index, and Wigle’s score. Results. Wigle’s score was directly related to pulmonary capillary Wedge pressure (r=0.436, p=0.048), peak V wave of pulmonary capillary wedge pressure (r=0.503, p=0.024), LV end-diastolic pressure (r=0.643, p=0.002) and k (r=0.564, p=0.015). HCM patients were divided into 2 groups according to Wigle’s score: 10 with mild or moderate LVH (< 8), and 11 with severe LVH (≥ 8). HCM patients with severe LVH showed a higher pulmonary capillary Wedge pressure (15.1±7.2 vs 9.5±2.4, p=0.033), peak V wave of pulmonary capillary wedge pressure (20.7±4.6 vs 14.6±4.9, p=0.011), LV end-diastolic pressure (23.9±10.9 vs 10.6±2.5, p=0.002), k (0.0465±0.032 vs 0.015±0.007, p=0.022) and LV outflow tract gradient (72±36 mmHg vs 29±30 mmHg, p=0.01).τ was similar in the two groups. Other indexes of LVH were not related to diastolic function.

Conclusions.

Wigle’s score is the only index of LVH that relates to invasive indices of diastolic function.

Role of Left Ventricular Regional Diastolic Abnormalities for Global Diastolic Dysfunction in Patients with Hypertrophic Cardiomyopathy

BACKGROUND

The usefulness of Doppler strain rate imaging for assessment of left ventricular regional diastolic function has not been fully determined.

OBJECTIVE

We aimed to clarify the relationships between diastolic strain rates and global diastolic function and find a useful index for regional diastolic function in patients with hypertrophic cardiomyopathy (HCM).

METHODS

Strain rate curves were obtained using an apical approach at 12 different sites of the left ventricular myocardium in 25 patients with HCM and 20 control subjects, and peak early diastolic strain rate (ESR), peak late diastolic strain rate, and the time from QRS to ESR were measured. The flow propagation velocity was measured using color M-mode Doppler echocardiography as a global diastolic index.

RESULTS

Each of the spatially averaged values of ESR and ESR/peak late diastolic strain rate and the coefficients of variation of time from QRS to ESR was significantly correlated with flow propagation velocity, but the best correlation was observed in ESR. Although both ESR and peak late diastolic strain rate of each myocardial segment of patients with HCM tended to decrease as the wall thickness increased, only ESR significantly decreased even in the segments without apparent hypertrophy.

CONCLUSIONS

In patients with HCM, the reduction of ESR was more closely associated with global diastolic dysfunction than asynchrony, and ESR may be a useful and sensitive index for regional diastolic function.

Prognostic value of intra-left ventricular electromechanical asynchrony in patients with mild hypertrophic cardiomyopathy compared with power athletes

OBJECTIVES

We sought to assess the indexes of myocardial activation delay, using Doppler myocardial imaging (DMI), as potential diagnostic tools and predictors of cardiac events in patients with hypertrophic cardiomyopathy (HCM) compared with power athletes.

BACKGROUND

the distribution and magnitude of left ventricular (LV) hypertrophy are not uniform in patients with HCM, which results in heterogeneity of regional LV systolic function.

METHODS

The study population comprised 70 young patients with HCM (mean (SD) age 29.4 (5.9) years) with mild septal hypertrophy (15-19 mm) and 85 age and sex matched athletes with septal thickness >12 mm, followed up for 44.4 (10.8) months. Using pulsed DMI, myocardial peak velocities, systolic time intervals, and myocardial intraventricular and interventricular systolic delays were measured in six different basal myocardial segments.

RESULTS

DMI analysis showed in HCM lower myocardial both systolic and early diastolic peak velocities of all the segments. Patients with HCM also showed significant interventricular and intraventricular delay (p<0.0001), whereas athletes showed homogeneous systolic activation of the ventricular walls. During the follow up, seven sudden deaths occurred in the HCM group, while no cardiovascular event was observed in the group of athletes. In patients with HCM, intraventricular delay on DMI was the most powerful independent predictor of sudden cardiac death (p<0.0001). An intraventricular delay >45 ms identified with high sensitivity and specificity patients with HCM at higher risk of ventricular tachycardia and cardiac events (test accuracy 90.6%).

CONCLUSIONS

DMI may be a valid supporting tool for the differential diagnosis between HCM and "athlete's heart". In patients with HCM, DMI indexes of intraventricular delay may provide additional information for selecting subgroups of patients with HCM at increased risk of ventricular arrhythmias and sudden cardiac death at follow up. Accordingly, such patients may benefit from early intensive treatment and survey. MINIABSTRACT: Doppler myocardial imaging may represent a valid supporting tool for the differential diagnosis between mild hypertrophic cardiomyopathy (HCM) and "athlete's heart". In patients with HCM, DMI indexes of intraventricular delay may provide additional information for selecting subgroups of patients with HCM at increased risk of ventricular arrhythmias and sudden cardiac death at follow up.

Prognostic value of intra-left ventricular electromechanical asynchrony in patients with hypertrophic cardiomyopathy†

AIMS

We sought to assess the indexes of myocardial activation delay, using Doppler myocardial imaging (DMI), as potential predictors of cardiac events in patients with hypertrophic cardiomyopathy (HCM). The distribution and magnitude of left ventricular (LV) hypertrophy are not uniform in patients with HCM, which results in heterogeneity of regional LV systolic function.

METHODS AND RESULTS

The study population included 123 HCM patients (39.4+/-5.9 years) and 123 age- and sex-matched healthy subjects, followed up for 48.4+/-8.8 months. By use of pulsed DMI, the following regional parameters were evaluated in six different basal myocardial segments: myocardial peak velocities and systolic time-intervals; myocardial intraventricular (intra-V-Del) and interventricular (inter-V-Del) systolic delays. DMI analysis in HCM showed lower myocardial systolic and early-diastolic peak velocities of all the segments. As for time intervals, HCM showed significant inter- and intra-V delays (P<0.0001), whereas homogeneous systolic activation of the ventricular walls was assessed in controls. During the follow-up, 16 cardiac deaths (12 sudden deaths) were observed in HCM patients. InHCM, DMI intra-V-Del was the most powerful independent predictor of sudden cardiac death (P<0.0001). In particular, an intra-V-Del>45 ms is identified with high sensitivity and specificity in HCM patients at higher risk of ventricular tachycardia and sudden cardiac death (test accuracy: 88.8%).

CONCLUSION

In HCM patients, DMI indexes of intra-V-Del may provide additional information for selecting subgroups of HCM patients at increased risk of ventricular arrhythmias and sudden cardiac death at follow-up. Accordingly, such patients may be more actively identified for early intensive treatment and survey.

Cine MR Imaging of Myocardial Contractile Impairment in Patients with Hypertrophic Cardiomyopathy Attributable to Asp175Asn Mutation in the α-Tropomyosin Gene

PURPOSE

To prospectively investigate the relationship between myocardial contractile impairment and left ventricular (LV) hypertrophy measured at cardiac magnetic resonance (MR) imaging in patients with hypertrophic cardiomyopathy (HCM) caused by the substitution of aspartic acid 175 with asparagine (ie, Asp175Asn mutation) in the alpha-tropomyosin gene (TPM1).

MATERIALS AND METHODS

The study protocol was approved by the hospital ethics committee, and all subjects gave written informed consent. LV mass, maximal LV wall thickness, and myocardial fractional thickening during systole were measured at cine MR imaging in 24 subjects (11 male, 13 female; mean age, 42 years; age range, 17-68 years) with the Asp175Asn mutation in TPM1 and in 17 healthy volunteers (eight men, nine women; mean age, 38 years; age range, 23-60 years). The proportion of hypokinetic LV segments was calculated as the number of LV segments with fractional thickening of less than 30% divided by the total number of segments measured. Anthropometric and biochemical correlates of LV hypertrophy were determined. Univariate and multiple linear regression analyses were used to investigate the association of the proportion of hypokinetic segments and other correlates of LV hypertrophy with LV mass and maximal wall thickness.

RESULTS

The proportion of hypokinetic segments was higher in patients with HCM than in control subjects (37% +/- 20 [standard deviation] vs 12% +/- 12, P < .001). In stepwise multiple regression analysis, the proportion of hypokinetic segments accounted for 42% (P < .001); the LV end-diastolic volume, for 24% (P = .003); and male sex, for 10% (P = .014) of the variability in LV mass in patients with HCM. The proportion of hypokinetic LV segments, which accounted for 48% of the variability in LV maximal wall thickness (P < .001), was the only variable significantly associated with maximal wall thickness.

CONCLUSION

The extent of myocardial contractile impairment is strongly and independently related to LV mass and maximal wall thickness in patients with HCM attributable to the Asp175Asn mutation in TPM1.

Quantification of Regional Nonuniformity and Paradoxical Intramural Mechanics in Hypertrophic Cardiomyopathy by High Frame Rate Ultrasound Myocardial Strain Mapping

This study tested the hypothesis that linear mapping of regional myocardial strain comprehensively assesses variations in regional myocardial function in hypertrophic cardiomyopathy. Hypertrophic cardiomyopathy is characterized by disorganized myocardial architecture that results in spatial and temporal nonuniformity of regional function. Left ventricular deformation was quantified in 20 patients with hypertrophic cardiomyopathy and compared with 25 age- and sex-matched control subjects. Abnormalities in subendocardial strain ranged from reduced longitudinal shortening to paradoxical systolic lengthening and delayed regional longitudinal contractions that were often located in small subsegmental areas. These variations were underestimated significantly by arbitrary measurements compared with linear mapping, in which a region of interest was moved across the longitudinal length of left ventricle (difference of peak and least strain, 10.7% +/- 5.1% vs 17% +/- 5.5%; P < .001). Echocardiographic assessment of variations in regional strain requires careful mapping and may be inappropriately assessed if left ventricular segments are sampled at arbitrary focal locations.

Prognostic value of heart rate variability in patients with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) have been reported to display impaired heart rate variability, although little is known regarding its prognostic value. By using fast Fourier transformation of 24-hour Holter recordings in 73 HCM patients at a stable clinical condition, we computed 4 spectral components: very low frequency, low frequency, high frequency, and total power. During 28 months, 7 HCM patients experienced death or acquired hospitalization for heart failure. Sudden death did not occurred. High frequency component was lower in HCM patients with cardiac events than that in patients without cardiac events (3.78 +/- 0.66 vs. 4.43 +/- 0.92 In(ms(2)), P =.045). There were no significant differences in other heart rate variability variables between HCM patients with and without cardiac events. In multivariate analysis, high frequency component remained to be an independent predictor of cardiac events (relative risk=0.10, 95% CI 0.01-0.73, P =.023). Heart rate variability analysis is predictive of heart failure in our cohort of HCM patients, whereas its predictive value of sudden death remains unclear.

Significance and relation between magnitude of left ventricular hypertrophy and heart failure symptoms in hypertrophic cardiomyopathy

In hypertrophic cardiomyopathy (HC), an important subgroup of patients develop progressive and disabling symptoms that are related to heart failure and death. Although a direct relation has been demonstrated between left ventricular (LV) wall thickness and likelihood of sudden and unexpected death (usually in patients who are asymptomatic or mildly symptomatic), it is unresolved whether magnitude of hypertrophy is similarly associated with severity of heart failure. To determine the relation of LV wall thickness to heart failure symptoms in HC, 700 consecutive patients who had HC were assessed by 2-dimensional echocardiography. The relation between maximum level of heart failure symptoms by New York Heart Association functional class and maximum LV wall thickness was not linear but rather parabolic. Therefore, marked symptoms were most commonly associated with moderate degrees of LV hypertrophy (wall thickness 16 to 24 mm; 27%) but less frequently with extreme hypertrophy (>/=30 mm 13%) or mild hypertrophy (</=15 mm; 19%, p = 0.0001). Mean New York Heart Association functional class showed a similar pattern with respect to moderate hypertrophy (1.9 +/- 0.8), mild hypertrophy (1.6 +/- 0.9), and extreme hypertrophy (1.6 +/- 0.7, p = 0.005). Multivariable regression analysis showed the parabolic relation between heart failure symptoms and magnitude of LV hypertrophy to be independent of other hypertrophic cardiomyopathy related clinical variables. In conclusion, no direct relation was evident between symptoms of heart failure and magnitude of LV wall thickness, with implications for the natural history of HC.

Assessment of regional left ventricular filling dynamics using color kinesis in patients with hypertrophic cardiomyopathy

OBJECTIVES

Using color kinesis, we evaluated regional left ventricular filling dynamics in patients with hypertrophic cardiomyopathy (HCM).

METHODS

In all, 20 patients (14 men and 6 women) and 20 age-matched healthy control subjects (10 men and 10 women) were studied. From color kinesis diastolic images in a left ventricular short-axis view, we generated regional time curves (6 segments) of left ventricular filling. The percent filling fraction at 25%, 50%, and 75% of filling time was averaged for all segments in each patient, and the SD of its mean was used as an asynchrony index at each particular filling time. The mean filling time for each segment was also measured.

RESULTS

The asynchrony index was increased significantly in mid (50%) to late (75%) diastole in patients with HCM as compared with control subjects. Patients with HCM had regional mean filling times prolonged even in the nonhypertrophic segments. Moreover, there was significant correlation between the asynchrony index at mid and late diastole, and the global mean filling time.

CONCLUSIONS

Color kinesis is useful in evaluating regional filling dynamics in patients with HCM. Our data reinforce the notion that HCM is a functionally heterogeneous disorder.

Acute Effects of Diltiazem on Regional Left Ventricular Diastolic Filling Dynamics in Patients With Hypertrophic Cardiomyopathy as Assessed by Color Kinesis

BACKGROUND

The effect of calcium antagonists on regional left ventricular (LV) filling dynamics in patients with hypertrophic cardiomyopathy (HCM) is not well known, so the present study evaluated the results of echocardiography with color kinesis (CK) analysis during diltiazem infusion.

METHODS AND RESULTS

Nineteen patients (16 men, 3 women; mean age 55+/-15 years) underwent echocardiography with CK analysis during intravenous diltiazem (10 mg/2 min). Using the quantitative CK software the LV short-axis image was divided into 6 segments and the percent endocardial expansion at the early, mid- and late-diastolic filling time was averaged for all segments, with the standard deviation of the mean used as an index of diastolic asynchrony (asynchrony index). The regional mean filling time was also measured for the corresponding segments. As global diastolic parameters, the global filling time, peak filling rate, and the time-to-peak filling were calculated. After the administration of diltiazem, the asynchrony index was decreased for all three diastolic filling times. Diltiazem shortened the mean filling time overall, especially in the posterior and lateral wall segments. These findings were associated with significant improvement in the CK-derived global diastolic parameters.

CONCLUSIONS

Diltiazam has a favorable effect on LV diastolic asynchrony, which may account for the acute changes in global LV relaxation.

Aetiology and pathogenesis of hypertrophic cardiomyopathy

The term hypertrophic cardiomyopathy is used to describe an autosomal dominant cardiac disorder, characterized by myocyte hypertrophy and disarray, interstitial fibrosis and small vessel disease, with or without macroscopic hypertrophy. More than 100 mutations in ten genes, all encoding sarcomeric proteins, have been identified as responsible for this disease. Mutations in the genes for beta-myosin heavy chain, myosin binding protein-C, and cardiac troponin T are the most common. Other genes involved are alpha-tropomyosin, cardiac troponin-I, essential and regulatory light chains, alpha-cardiac actin, titin, and alpha-myosin heavy chain. Some mutations are more frequently associated with a given phenotype, but no particular phenotype is mutation specific; in fact, some mutations exhibit highly variable clinical, electrocardiographic and echocardiographic manifestations. This variability in the phenotypic manifestations is probably due to the influence of environmental factors and/or modifier genes. While the aetiology of hypertrophic cardiomyopathy has been extensively elucidated, its pathogenesis is not completely understood. Mutated proteins are incorporated in the sarcomere and impair myocyte contractility. This probably triggers the compensatory local release of trophic factors, which influence the development of the typical anatomical features of the disease, with a pathway similar to that observed in secondary, pressure overload hypertrophy.

CONCLUSIONS

The various pathological cardiac changes seen in hypertrophic cardiomyopathy are probably due to a compensatory response to impaired myocyte function resulting from mutations in the genes encoding sarcomeric proteins.

Original report. Late myocardial enhancement in hypertrophic cardiomyopathy with contrast-enhanced MR imaging

OBJECTIVE

Contrast-enhanced MR imaging has great clinical value as a means of characterizing myocardial tissue in patients with ischemic heart disease. The purpose of our study was to evaluate use of this technique in the assessment of patients with hypertrophic cardiomyopathy.

CONCLUSION

On late-enhancement MR imaging, the various types or patterns of enhancement found in patients with hypertrophic cardiomyopathy are related to differences in morphology and regional function. Enhancement in hypertrophied areas likely reflects the presence of abundant connective tissue, foci of myocardial necrosis, or a combination of both.

Effect of dobutamine on regional diastolic left ventricular asynchrony in patients with left ventricular hypertrophy

Dobutamine improves systolic as well as diastolic function, but its effect on left ventricular (LV) asynchrony is unknown. An on-line automated segmental motion analysis (A-SMA) system was developed, based on an automatic border detection technique, to evaluate the effect of dobutamine on LV asynchrony in patients with LV hypertrophy (LVH). Low dose (5 microg x kg (-1) x min(-1)) dobutamine stress echocardiography was performed in 15 patients with LVH and in 15 healthy subjects. Short-axis LV views were obtained and divided into 4 wedge-shaped segments using A-SMA. The time - area curve and its first derivative curve in each segment were displayed. Total normalized peak filling rates (nPFR) were obtained. Systolic and diastolic asynchronies were assessed from the coefficient of variation (CV) of the regional time intervals from end diastole to the peak ejection rate (T-PER), and from end systole to the peak filling rate (T-PFR), respectively. At baseline, the CV of T-PER and T-PFR in patients with LVH were greater than those in healthy subjects (CV-T-PER: 18.8+/-9.2 vs 9.6+/-4.3%, CV-T-PFR: 19.5+/-7 vs 8.1+/-4.1%, both p<0.01). During dobutamine infusion, differences among groups at baseline disappeared and systolic and diastolic asynchronies improved (CV-T-PER: 7.3+/-4.8 vs 5.7+/-2.1%, CV-T-PFR: 6.8+/-3.5 vs 5.1+/-1.3%, both p>0.05). Total nPFR increased (from 3.2+/-1.0 /s to 5.6+/-1.3 /s, p<0.01) with dobutamine infusion in patients with LVH. Dobutamine improved LV diastolic asynchrony, as evaluated by A-SMA, in patients with LVH demonstrating that the lusitropic effect of dobutamine improved LV regional diastolic asynchrony, playing an important role in the improvement of global LV diastolic filling.

Echocardiographic assessment of patients with hypertrophic and restrictive cardiomyopathy: imaging and echocardiography

Echocardiography has evolved to be an important tool in the assessment of patients with hypertrophic and restrictive cardiomyopathy. In this article, the authors review the use of echocardiography in diagnosis, differentiation from disease mimics, assessment of prognosis, and the assistance of specific therapies. A pathophysiologic understanding of restrictive cardiomyopathy and constrictive pericarditis will be reviewed along with echocardiographic and Doppler features that help to distinguish these two entities.

Systolic and diastolic performance late after the Fontan procedure for a single ventricle and comparison of those undergoing operation at <12 months of age and at >12 months of age

To evaluate whether surgical history can influence systolic and diastolic properties of a functional single left ventricle after Fontan operation, we echocardiographically investigated 31 patients (mean age 93.7 months; range 21 to 276); 21 patients were >12 months of age (group A) and 10 were <12 months of age (group B) at the time of the Fontan and/or cavopulmonary procedure. In group A we found persistent abnormalities of left ventricular mass index (95.9 vs 64.1 g/m(2), p <0.05) at long-term follow-up, whereas group B had normal left ventricular mass (61.9 vs 64.1 g/m2, p = NS). In contrast, a diastolic pattern characterized by augmented late diastolic filling was present in both patient groups regardless of age at operation and length of follow-up (E/A in group A 1.3 +/- 0.4, E/A in group B 1.6 +/- 1.5, E/A in controls 1.7 +/- 0.6; A vs B, p = NS; A vs controls, p <0.05). We concluded that patients with a single left ventricle who undergo an unloading procedure performed within the first year of life have complete normalization of left ventricular mass, although a diastolic filling pattern suggestive of augmented compliance persists, regardless of the age at operation.

Use of angiotensin II stress pulsed tissue Doppler imaging to evaluate regional left ventricular contractility in patients with hypertrophic cardiomyopathy

There is controversy concerning whether contract-ility in the nonhypertrophied region of the left ventricular (LV) wall is impaired or normal in patients with hypertrophic cardiomyopathy (HCM). Global LV systolic function decreases with increases in afterload in this disease. This study was performed to identify abnormalities in regional LV contractility along the long and short axes in the setting of HCM with the use of angiotensin II (AT-II) stress pulsed tissue Doppler imaging (PTDI). Angiotensin II was administered intravenously to patients with asymmetric septal hypertrophy (HCM group, n = 21) and age-matched normal volunteers (N group, n = 12). We then measured the percent LV fractional shortening (%FS) and end-systolic circumferential LV wall stress by M-mode echocardiography, LV ejection fraction (LVEF) by 2-dimensional echocardiography, and time-velocity integral (TVI) of LV outflow velocity by pulsed Doppler echocardiography. The peak first and second systolic LV wall motion velocities along the long (L-Sw(1) and L-Sw(2)) and short (S-Sw(1) and S-Sw(2)) axes were measured in the LV posterior wall and ventricular septum with the use of PTDI. The end-systolic circumferential LV wall stress at baseline was significantly lower in the HCM group. The L-Sw(1) and L-Sw(2) for the posterior wall were significantly lower in the HCM group, but the S-Sw(1) and S-Sw(2) for the posterior wall and ventricular septum were similar in the two groups. The %FS, LVEF, TVI, and systolic PTDI variables along both axes for the posterior wall decreased significantly, and end-systolic circumferential LV wall stress increased significantly at AT-II doses of 0.005 or 0.010 microg/kg per minute in the HCM group. No significant changes were found in either group in the systolic PTDI variables (except for L-Sw(1)) for the ventricular septum with AT-II infusion. Contractility along the long and short axes of the nonhypertrophied LV wall is easily impaired with increases in afterload in patients with HCM, resulting in a decrease in global LV systolic function. We found AT-II stress PTDI to be a safe and useful technique for evaluating the regional LV systolic function in this disease.

Usefulness of early diastolic flow propagation velocity measured by color M-mode Doppler technique for the assessment of left ventricular diastolic function in patients with hypertrophic cardiomyopathy

Flow propagation velocity (FPV) of left ventricular (LV) filling flow has been shown to be a useful index for the evaluation of LV diastolic function, which is relatively independent of preload in myocardial infarction and dilated cardiomyopathy, but the usefulness of FPV for hypertrophic cardiomyopathy (HCM) has not yet been determined. In 23 HCM patients and 26 control subjects, peak transmitral flow velocities in early diastole (E) and during atrial contraction (A), E/A ratio, deceleration time of E velocity, and isovolumic relaxation time were measured with the conventional Doppler technique, and FPV was measured from color M-mode Doppler images of LV filling flow. The time constant of LV isovolumic pressure decay (tau) was measured by a micro-manometer-tipped catheter in all HCM patients and 13 control subjects. Flow propagation velocity was significantly lower and deceleration time was significantly greater in HCM patients than in the control subjects, though no significant differences were observed in the other noninvasive indexes. Tau was significantly prolonged in HCM patients compared with that of control subjects (54+/-12 cm/s and 32 +/-7 cm/s, respectively; P<.0001). While the conventional indexes did not correlate with tau among the 36 patients in whom invasive studies were performed, FPV correlated well with tau (r = -0.76, P<.0001). Flow propagation velocity is a useful noninvasive index for the assessment of LV diastolic function in patients with HCM.

Relaxation in hypertrophic cardiomyopathy and hypertensive heart disease: relations between hypertrophy and diastolic function

AIM

To determine the relation between the extent and distribution of left ventricular hypertrophy and the degree of disturbance of regional relaxation and global left ventricular filling.

METHODS

Regional wall thickness (rWT) was measured in eight myocardial regions in 17 patients with hypertrophic cardiomyopathy, 12 patients with hypertensive heart disease, and 10 age matched normal subjects, and an asymmetry index calculated. Regional relaxation was assessed in these eight regions using regional isovolumetric relaxation time (rIVRT) and early to late peak filling velocity ratio (rE/A) derived from Doppler tissue imaging. Asynchrony of rIVRT was calculated. Doppler left ventricular filling indices were assessed using the isovolumetric relaxation time, the deceleration time of early diastolic filling (E-DT), and the E/A ratio.

RESULTS

There was a correlation between rWT and both rIVRT and rE/A in the two types of heart disease (hypertrophic cardiomyopathy: r = 0.47, p < 0.0001 for rIVRT; r = -0.20, p < 0.05 for rE/A; hypertensive heart disease: r = 0.21, p < 0.05 for rIVRT; r = -0.30, p = 0.003 for rE/A). The degree of left ventricular asymmetry was related to prolonged E-DT (r = 0. 50, p = 0.001) and increased asynchrony (r = 0.42, p = 0.002) in all patients combined, but not within individual groups. Asynchrony itself was associated with decreased E/A (r = -0.39, p = 0.01) and protracted E-DT (r = 0.69, p < 0.0001) and isovolumetric relaxation time (r = 0.51, p = 0.001) in all patients. These correlations were still significant for E-DT in hypertrophic cardiomyopathy (r = 0.56, p = 0.02) and hypertensive heart disease (r = 0.59, p < 0.05) and for isovolumetric relaxation time in non-obstructive hypertrophic cardiomyopathy (n = 8, r = 0.87, p = 0.005).

CONCLUSIONS

Non-invasive ultrasonographic examination of the left ventricle shows that in both hypertrophic cardiomyopathy and hypertensive heart disease, the local extent of left ventricular hypertrophy is associated with regional left ventricular relaxation abnormalities. Asymmetrical distribution of left ventricular hypertrophy is indirectly related to global left ventricular early filling abnormalities through regional asynchrony of left ventricular relaxation.

Regional dysfunction correlates with myofiber disarray in transgenic mice with ventricular expression of ras

A hallmark of certain cardiac diseases such as familial hypertrophic cardiomyopathy is focal myofiber disarray. Regional ventricular dysfunction occurs in human subjects with hypertrophic cardiomyopathy; however, no direct evidence exists to correlate regional dysfunction with myofiber disarray. We used a transgenic mouse, which exhibits regional myofiber disarray via ventricular expression of the human oncogene ras, to investigate the relationship between myofiber disarray and septal surface strain. An isolated ejecting mouse heart preparation was used to record deformation of markers on the septal surface and to determine nonhomogeneous septal surface strain maps. Myofiber disarray made in histological tissue sections was correlated with gradients in surface systolic shortening. Significantly smaller maximum principal shortening was associated with disarray located near the right ventricle (RV) septal surface. There was also significantly smaller surface shear strain associated with disarray located either near the RV surface or at the midwall. Because surface shear is a local indicator of torsion, we conclude that myofiber disarray is associated with reduced septal torsion and reduced surface shortening.

Detection of left ventricular regional relaxation abnormalities and asynchrony in patients with hypertrophic cardiomyopathy with the use of tissue Doppler imaging

BACKGROUND

It is well known that the distribution and magnitude of left ventricular (LV) hypertrophy are not uniform in patients with hypertrophic cardiomyopathy (HCM), which results in regional heterogeneity of LV early diastolic function. The advent of tissue Doppler imaging (TDI) has allowed the noninvasive evaluation of regional LV wall motion velocities. The aim of this study was to evaluate regional LV relaxation abnormalities and asynchrony noninvasively in patients with HCM by using pulsed and color-coded TDI.

METHODS AND RESULTS

We studied 20 patients with asymmetric septal hypertrophy (HCM group) and 18 age-matched normal patients (control group). The peak early diastolic motion velocity (Ew) and time from the aortic component of the second heart sound to the peak of the Ew (II(A)-Ew) were measured by pulsed TDI. The myocardial velocity gradient during early diastole (MVG-Ew) also was measured by color-coded TDI. Mean values for these parameters were determined on the basis of measurements made at 2 sites of the ventricular septum or posterior wall at the levels of chordae tendineae and papillary muscles. The mean Ew and mean MVG-Ew for the ventricular septum and posterior wall were significantly lower, and mean II(A)-Ew was significantly prolonged in the HCM group compared with the control group. This difference was most pronounced in the hypertrophied ventricular septum of the HCM group. The standard deviations of II(A)-Ew for the ventricular septum and posterior wall were significantly greater in the HCM group than in the control group. The time constant of LV pressure decay during isovolumic diastole (tau) correlated inversely with Ew and MVG-Ew and correlated directly with II(A)-Ew. Furthermore, tau correlated directly with the standard deviation of the II(A)-Ew.

CONCLUSIONS

LV early diastolic function in patients with HCM may be mediated by an augmentation of regional LV relaxation abnormalities and asynchrony.

Subendocardial motion in hypertrophic cardiomyopathy: assessment from long- and short-axis views by pulsed tissue Doppler imaging

BACKGROUND

Tissue Doppler imaging (TDI) is a recently developed technique that allows the instantaneous measurement of intrinsic regional myocardial motion velocity. Pulsed TDI is capable of separately assessing left ventricular (LV) regional motion velocity caused by circumferential and longitudinal fiber contraction. This particular feature of function is still controversial in patients with hypertrophic cardiomyopathy (HC).

METHODS

To better characterize intrinsic circumferential and longitudinal LV systolic myocardial function in HC, we used pulsed TDI to measure short- and long-axis LV motion velocities, respectively. The subendocardial motion velocity patterns at the middle of the LV posterior wall (PW) and ventricular septum (IVS) in LV parasternal and apical long-axis views were recorded by pulsed TDI in 19 patients with nonobstructive HC and in 21 normal controls (NC).

RESULTS

Peak short- and long-axis systolic subendocardial velocities in both the LV PW and IVS were significantly smaller in the HC group than in the NC group, and the time to peak velocity was significantly delayed. Furthermore, peak PW systolic velocity was significantly greater along the long axis than along the short axis in the NC group (8.8 +/- 1.5 cm/s vs 8.2 +/- 1.4 cm/s, P <.05), whereas the opposite was observed in the HC group (6.1 +/- 1.2 cm/s vs 7.5 +/- 1.0 cm/s, P <.0001). No significant differences were found in either group between the long- and short-axis IVS velocities (HC: 5.9 +/- 1.4 cm/s vs 5.5 +/- 1.3 cm/s; NC: 7.8 +/- 1.3 cm/s vs 7.9 +/- 1.6 cm/s).

CONCLUSIONS

By using the capability of pulsed TDI for the evaluation of intrinsic myocardial velocity instantaneously in a specific region and direction, we found impairment of LV myocardial systolic function in patients with HC not only in the hypertrophied IVS but also in the nonhypertrophied LV PW. We also found a greater decrease in LV PW velocities along the long axis than the short axis, suggesting greater impairment of long-axis contraction in patients with HC. Because our HC patients did not appear to have excessive intracavitary pressure, these results suggest that the relatively normal-appearing PW is directly affected by the HC pathologic process.

Right ventricular diastolic function in patients with hypertrophic cardiomyopathy--an invasive study

To assess diastolic function of the right ventricle (RV) in patients with hypertrophic cardiomyopathy (HCM), biplane RV angiograms and RV pressures were analyzed in 19 HCM patients and in 13 normal subjects. RV and left ventricle (LV) pressures were measured using catheter-tip manometers. RV volumes were obtained from frame-by-frame tracings of angiograms. Ventricular relaxation was assessed by the time constant of isovolumic pressure decay (T). The peak filling rate (PFR) and the time to PFR (TPFR) were used as parameters of early diastolic filling, and the right atrial contribution to RV filling (%AF) was used as a parameter of late diastolic filling. The T for the RV was significantly prolonged in HCM patients. However, there was no significant correlation between the T for the RV and LV, nor did the T for the RV correlate with the RV ejection fraction or interventricular septal wall thickness. The TPFR, but not PFR, was significantly greater in HCM patients, and the %AF tended to be increased in HCM, but not significantly. The RV diastolic pressure-volume relations in the HCM patients shifted upward. In conclusion, impaired isovolumic relaxation and delayed diastolic filling and decreased diastolic distensibility are present in the RV of HCM patients.