Assessment of quantitative hypertrophy scores in hypertrophic cardiomyopathy: magnetic resonance imaging versus echocardiography

Maximal Wall Thickness Measurement in Hypertrophic Cardiomyopathy: Biomarker Variability and its Impact on Clinical Care

OBJECTIVES

The aim of this study was to define the variability of maximal wall thickness (MWT) measurements across modalities and predict its impact on care in patients with hypertrophic cardiomyopathy (HCM).

BACKGROUND

Left ventricular MWT measured by echocardiography or cardiovascular magnetic resonance (CMR) contributes to the diagnosis of HCM, stratifies risk, and guides key decisions, including whether to place an implantable cardioverter-defibrillator (ICD).

METHODS

A 20-center global network provided paired echocardiographic and CMR data sets from patients with HCM, from which 17 paired data sets of the highest quality were selected. These were presented as 7 randomly ordered pairs (at 6 cardiac conferences) to experienced readers who report HCM imaging in their daily practice, and their MWT caliper measurements were captured. The impact of measurement variability on ICD insertion decisions was estimated in 769 separately recruited multicenter patients with HCM using the European Society of Cardiology algorithm for 5-year risk for sudden cardiac death.

RESULTS

MWT analysis was completed by 70 readers (from 6 continents; 91% with >5 years' experience). Seventy-nine percent and 68% scored echocardiographic and CMR image quality as excellent. For both modalities (echocardiographic and then CMR results), intramodality inter-reader MWT percentage variability was large (range -59% to 117% [SD ±20%] and -61% to 52% [SD ±11%], respectively). Agreement between modalities was low (SE of measurement 4.8 mm; 95% CI 4.3 mm-5.2 mm; r = 0.56 [modest correlation]). In the multicenter HCM cohort, this estimated echocardiographic MWT percentage variability (±20%) applied to the European Society of Cardiology algorithm reclassified risk in 19.5% of patients, which would have led to inappropriate ICD decision making in 1 in 7 patients with HCM (8.7% would have had ICD placement recommended despite potential low risk, and 6.8% would not have had ICD placement recommended despite intermediate or high risk).

CONCLUSIONS

Using the best available images and experienced readers, MWT as a biomarker in HCM has a high degree of inter-reader variability and should be applied with caution as part of decision making for ICD insertion. Better standardization efforts in HCM recommendations by current governing societies are needed to improve clinical decision making in patients with HCM.

The follow-up of progressive hypertrophic cardiomyopathy using magnetic resonance rotating frame relaxation times

Magnetic resonance rotating frame relaxation times are an alternative non-contrast agent choice for the diagnosis of chronic myocardial infarct. Fibrosis typically occurs in progressive hypertrophic cardiomyopathy. Fibrosis has been imaged in myocardial infarcted tissue using rotating frame relaxation times, which provides the possibility to follow up progressive cardiomyopathy without contrast agents. Mild and severe left ventricular hypertrophy were induced in mice by transverse aortic constriction, and the longitudinal rotating frame relaxation times (T_1ρ ) and relaxation along the fictitious field (T_RAFF2 , T_RAFF3 ) were measured at 5, 10, 24, 62 and 89 days after transverse aortic constriction in vivo. Myocardial fibrosis was verified using Masson's trichrome staining. Increases in the relative relaxation time differences of T_1ρ , together with T_RAFF2 and T_RAFF3 , between fibrotic and remote tissues over time were observed. Furthermore, T_RAFF2 and T_RAFF3 showed higher relaxation times overall in fibrotic tissue than T_1ρ . Relaxation time differences were highly correlated with an excess of histologically verified fibrosis. We found that T_RAFF2 and T_RAFF3 are more sensitive than T_1ρ to hypertrophic cardiomyopathy-related tissue changes and can serve as non-invasive diagnostic magnetic resonance imaging markers to follow up the mouse model of progressive hypertrophic cardiomyopathy.

Advanced Imaging of Athletes: Added Value of Coronary Computed Tomography and Cardiac Magnetic Resonance Imaging

Cardiac magnetic resonance imaging and cardiac computed tomographic angiography have become important parts of the armamentarium for noninvasive diagnosis of cardiovascular disease. Emerging technologies have produced faster imaging, lower radiation dose, improved spatial and temporal resolution, as well as a wealth of prognostic data to support usage. Investigating true pathologic disease as well as distinguishing normal from potentially dangerous is now increasingly more routine for the cardiologist in practice. This article investigates how advanced imaging technologies can assist the clinician when evaluating all athletes for pathologic disease that may put them at risk.

Spirito-Maron echocardiographic score: a marker for morphological and physiological assessment of patients with hypertrophic cardiomyopathy

AIMS

The heterogeneous distribution of hypertrophy in hypertrophic cardiomyopathy (HCM) limits the echocardiographic conventional measurements accuracy in the evaluation of left ventricular hypertrophy (LVH). The aim of this study was to assess the correlation of the echocardiographic Spirito-Maron score (SMS) with left ventricle (LV) mass quantification by cardiac magnetic resonance (CMR) and with LV diastolic function.

METHODS AND RESULTS

Left ventricle diastolic function parameters, SMS, LV mass (American Society of Echocardiography formula), and maximal wall thickness (MWT) were evaluated by two-dimensional (2D) transthoracic echocardiography. The SMS was obtained by adding the MWT of 4 LV segments, at the mitral valve or papillary muscles short-axis views. Echocardiographic parameters of LVH, including SMS, were correlated with LV mass obtained by CMR and with E/e' ratio. We included 45 patients (60% male, mean age 48 ± 18 years), who underwent 2D echocardiography. Twenty-two of them performed a CMR study. A positive correlation was found between SMS and CMR LV mass (r = 0.80; P < 0.001), whereas MWT (r = 0.62; P = 0.002) and the 2D LV mass (r = 0.60; P = 0.011) presented a lower correlation with CMR LV mass. The SMS was significantly correlated with E/e' ratio (r = 0.60; P = 0.007), whereas a nonsignificant correlation was found with MWT (r = 0.41; P = 0.081) and 2D LV mass (r = 0.22; P = 0.400).

CONCLUSION

Spirito-Maron score presents a highly positive correlation with CMR LV mass and with diastolic dysfunction severity in HCM patients. SMS is a reliable quantitative LVH measurement method and seems to provide more comprehensive morphological and physiological information than 2D echocardiographic conventional parameters used to estimate LVH.

The diagnosis of hypertrophic cardiomyopathy by cardiovascular magnetic resonance

Hypertrophic cardiomyopathy (HCM) is the most common genetic disease of the heart. HCM is characterized by a wide range of clinical expression, ranging from asymptomatic mutation carriers to sudden cardiac death as the first manifestation of the disease. Over 1000 mutations have been identified, classically in genes encoding sarcomeric proteins. Noninvasive imaging is central to the diagnosis of HCM and cardiovascular magnetic resonance (CMR) is increasingly used to characterize morphologic, functional and tissue abnormalities associated with HCM. The purpose of this review is to provide an overview of the clinical, pathological and imaging features relevant to understanding the diagnosis of HCM. The early and overt phenotypic expression of disease that may be identified by CMR is reviewed. Diastolic dysfunction may be an early marker of the disease, present in mutation carriers prior to the development of left ventricular hypertrophy (LVH). Late gadolinium enhancement by CMR is present in approximately 60% of HCM patients with LVH and may provide novel information regarding risk stratification in HCM. It is likely that integrating genetic advances with enhanced phenotypic characterization of HCM with novel CMR techniques will importantly improve our understanding of this complex disease.

Imaging spectrum of sudden athlete cardiac death

Sudden athlete death (SAD) is a widely publicized and increasingly reported phenomenon. For many, the athlete population epitomize human physical endeavour and achievement and their unexpected death comes with a significant emotional impact on the public. Sudden deaths within this group are often without prior warning. Preceding symptoms of exertional syncope and chest pain do, however, occur and warrant investigation. Similarly, a positive family history of sudden death in a young person or a known family history of a condition associated with SAD necessitates further tests. Screening programmes aimed at detecting those at risk individuals also exist with the aim of reducing fatalities. In this paper we review the topic of SAD and discuss the epidemiology, aetiology, and clinical presentations. We then proceed to discuss each underlying cause, in turn discussing the pathophysiology of each condition. This is followed by a discussion of useful imaging methods with an emphasis on cardiac magnetic resonance and cardiac computed tomography and how these address the various issues raised by the pathophysiology of each entity. We conclude by proposing imaging algorithms for the investigation of patients considered at risk for these conditions and discuss the various issues raised in screening.

Diagnostic, prognostic, and therapeutic implications of genetic testing for hypertrophic cardiomyopathy

Over the last 2 decades, the pathogenic basis for the most common heritable cardiovascular disease, hypertrophic cardiomyopathy (HCM), has been investigated extensively. Affecting approximately 1 in 500 individuals, HCM is the most common cause of sudden death in young athletes. In recent years, genomic medicine has been moving from the bench to the bedside throughout all medical disciplines including cardiology. Now, genomic medicine has entered clinical practice as it pertains to the evaluation and management of patients with HCM. The continuous research and discoveries of new HCM susceptibility genes, the growing amount of data from genotype-phenotype correlation studies, and the introduction of commercially available genetic tests for HCM make it essential that the modern-day cardiologist understand the diagnostic, prognostic, and therapeutic implications of HCM genetic testing.

Utility of cardiac magnetic resonance imaging in the diagnosis of hypertrophic cardiomyopathy

BACKGROUND

Two-dimensional echocardiography is currently the standard test for the clinical diagnosis of hypertrophic cardiomyopathy (HCM). The present study was undertaken to determine whether cardiac MRI (CMR) affords greater accuracy than echocardiography in establishing the diagnosis and assessing the magnitude of left ventricular (LV) hypertrophy in HCM.

METHODS AND RESULTS

Forty-eight patients (age 34+/-16 years) suspected of having HCM (or with a confirmed diagnosis) were imaged by both echocardiography and CMR to assess LV wall thickness in 8 anatomic segments (total n=384 segments) and compared in a blinded fashion. Maximum LV thickness was similar by echocardiography (21.7+/-9.1 mm) and CMR (22.5+/-9.6 mm; P=0.21). However, in 3 (6%) of the 48 patients, echocardiography did not demonstrate LV hypertrophy, and CMR identified otherwise undetected areas of wall thickening in the anterolateral LV free wall (17 to 20 mm), which resulted in a new diagnosis of HCM. In the overall study group, compared with CMR, echocardiography also underestimated the magnitude of hypertrophy in the basal anterolateral free wall (by 20+/-6%; P=0.001), as well as the presence of extreme LV wall thickness (> or =30 mm) in 10% of patients (P<0.05).

CONCLUSIONS

CMR is capable of identifying regions of LV hypertrophy not readily recognized by echocardiography and was solely responsible for diagnosis of the HCM phenotype in an important minority of patients. CMR enhances the assessment of LV hypertrophy, particularly in the anterolateral LV free wall, and represents a powerful supplemental imaging test with distinct diagnostic advantages for selected HCM patients.

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.

Diagnostic accuracy of a 2D left ventricle hypertrophy score for familial hypertrophic cardiomyopathy

AIMS

To study the diagnostic value of a new 2D left ventricle hypertrophy (2D LVH) score in families with hypertrophic cardiomyopathy (HCM) in comparison with the conventional maximal wall thickness (MWT) measurement (>13 mm in adults), which is limited by a low sensitivity in relatives.

METHODS AND RESULTS

The study was performed in 237 adults from genotyped families with HCM. Population A (derivation sample) comprised 109 adults and population B (validation sample) comprised 128 adults. MWT and 2D LVH scores (sum of thicknesses of four segments) were determined by echocardiography. Genotyping was the gold standard for diagnosis. In population A, a theoretical value for LVH score was determined in the healthy population by a multiple linear regression model including age, sex, and body surface area. An abnormal cut-off value was defined as an LVH score above a maximum theoretical value according to receiver operating characteristic analysis. Sensitivity and specificity were, respectively, 73 and 96% for 2D LVH score and 62.5 and 100% for MWT. Improvement of sensitivity was particularly important in adults <50 years of age (69 vs. 54%, respectively, P<0.04). These results were validated in population B: sensitivity and specificity of LVH score were, respectively, 75 and 96% in this sample and 67 and 97%, in the subgroup <50 years. In the latter, sensitivity of LVH score increased when compared with that of MWT (67 vs. 53%, P<0.03).

CONCLUSIONS

The LVH score has a higher diagnostic value for HCM than the conventional criterion of MWT, particularly in young adults. This echographic parameter may be proposed as an alternative diagnostic criterion for familial screening.

Differences in regional systolic and diastolic function by Doppler tissue imaging in patients with hypertrophic cardiomyopathy and hypertrophy caused by hypertension

OBJECTIVE

Doppler tissue (DT) velocity abnormalities have been described in patients with pathologic left ventricular hypertrophy (LVH). Impaired myocardial function has been suggested as a primary disorder in hypertrophic cardiomyopathy (HCM) and differences in DT parameters have been reported to be distinguishable from other LVH causes. We evaluated DT differences for patients with LVH caused by hypertension and patients with HCM, assessing regional systolic and diastolic function.

METHODS

A total of 62 participants were studied: 21 with HCM; 22 with LVH secondary to hypertension; and 19 control subjects. DT was used to record mitral annulobasal segment motion in the longitudinal axis. Systolic and diastolic velocities were measured at lateral and septal sites, and well-known ratios were obtained for diastolic assessment. A new global function index (GFI) that evaluates both systole and diastole was also calculated (GFI = [Emi/E(DT)]/S(DT) [s x cm(-1)], where mi is mitral inflow, E is E wave, and S is systolic wave).

RESULTS

Comparison showed significant differences in all parameters evaluated at the septal-basal segment and a GFI value of 1.77 showed 85% sensitivity and 75% specificity for detecting HCM when interventricular septum thickness was increased.

CONCLUSIONS

In the presence of unexplained LVH, markedly decreased DT velocities at basal septum efficiently detect myocardial dysfunction at this segment, and a calculated GFI > 1.77 strongly supports the diagnosis of HCM.

First-pass MR imaging in the assessment of perfusion impairment in patients with hypertrophic cardiomyopathy and the Asp175Asn mutation of the alpha-tropomyosin gene

PURPOSE

To assess first-pass magnetic resonance (MR) imaging in the evaluation of perfusion impairment in a genetically homogeneous population of patients with hypertrophic cardiomyopathy (HCM) and the Asp175Asn mutation of the alpha-tropomyosin gene and to evaluate the association between hypertrophy and perfusion.

MATERIALS AND METHODS

Rest-stress first-pass MR imaging with gadopentetate dimeglumine was performed in 17 patients with HCM and the Asp175Asn substitution in the alpha-tropomyosin gene and in five control subjects. Global and segmental first-pass reserve index (FPR) measurements were derived from signal intensity versus time curves. Left ventricular (LV) wall thickness and LV mass index were measured on cine MR images. The Mann-Whitney test was used to evaluate the difference in FPR between the patient group and the control group. The Spearman correlation was used to evaluate the association between LV hypertrophy and FPR.

RESULTS

Global FPR was significantly lower in the patients with HCM than in the control subjects (1.12 +/- 0.35 vs 1.80 +/- 0.58, P =.015). In patients with HCM, maximal LV wall thickness and LV mass index correlated negatively with global FPR (r = -0.723, P =.001 and r = -0.598, P =.011, respectively). At the regional level, segmental FPR correlated inversely with LV wall thickness (r = -0.389; P <.001) in patients with HCM.

CONCLUSION

First-pass MR imaging facilitates global and regional evaluation of perfusion impairment in patients with HCM. The severity of perfusion impairment is associated with the degree of LV hypertrophy.

Different beta-adrenergic regulation of myocardial contraction and relaxation between apical and nonobstructive hypertrophic cardiomyopathy

BACKGROUND

The impaired adrenergic control of both inotropic and lusitropic reserves has been evaluated in patients with hypertrophic cardiomyopathy (HCM) but not in those with apical HCM (APH).

OBJECTIVES

We examined the influence of increases in heart rate and adrenergic stimulation on inotropic and lusitropic reserves in HCM and APH with normal resting left ventricular (LV) systolic function.

METHODS

We evaluated LV isovolumic contraction and relaxation during atrial pacing and during supine leg exercise in 7 patients with APH and in 8 patients with HCM.

RESULTS

Heart rate was significantly correlated with LV isovolumic contraction and relaxation during pacing and exercise in all patients. In all patients with APH, the increase in LV isovolumic contraction was greater during exercise (101%) than pacing alone (27%) for similar increase in heart rate. In 5 patients with HCM, the increase in LV isovolumic contraction was greater during exercise (83%) than pacing alone (24%), whereas in 3 patients with HCM the increase in LV isovolumic contraction was similar between during exercise (25%) and during pacing alone (22%). In all patients with APH, relaxation was shorter during exercise (39%) than pacing alone (16%). Conversely, in patients with HCM relaxation was similarly shortened between during pacing alone (20%) and during exercise (19%).

CONCLUSIONS

The force-frequency and the relaxation-frequency relations were well-preserved in all patients. In patients with HCM, the adrenergic enhancement of force-frequency relation and/or relaxation-frequency relation was impaired. In patients with APH, however, adrenergic control of both force-frequency and relaxation-frequency relations was well-preserved, which may indicate a preserved beta-adrenergic signaling pathway.

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.

Quantitative assessment of the operative results after extended myectomy and surgical reconstruction of the subvalvular mitral apparatus in hypertrophic obstructive cardiomyopathy using dynamic three-dimensional transesophageal echocardiography

OBJECTIVES

The aim of this study was to examine the value of dynamic three-dimensional (3D) transesophageal echocardiography (TEE) for the postoperative evaluation after extended myectomy and surgical reconstruction of the subvalvular mitral valve apparatus in patients with hypertrophic obstructive cardiomyopathy (HOCM).

BACKGROUND

Two-dimensional imaging techniques such as echocardiography, computed tomography and magnetic resonance imaging have not been able to precisely quantify the effects of surgical therapy on the morphology of the left ventricular outflow tract (LVOT).

METHODS

Multiplane TEE with 3D reconstruction was performed in 11 patients before and after the operation and in 16 normal control subjects for comparison. The preoperative maximal systolic pressure gradient in the LVOT was 69 +/- 59 mm Hg. The following variables were measured within the dynamic 3D data set: depth, width, length and cross-sectional area (CSA) gain caused by the myectomy trough, minimal CSA of the LVOT at each time point and its cyclic changes and maximal mitral leaflet deviation during systole.

RESULTS

Functional class improved from 3.0 +/- 0.2 before the operation to 1.5 +/- 0.6 after it. The maximal systolic pressure gradient in the outflow tract decreased to 26 +/- 21 mm Hg postoperatively (p < 0.001). Minimal CSA of the outflow tract increased from 1.1 +/- 1.2 to 3.8 +/- 1.9 cm2 postoperatively (p < 0.001), similar to the value of the control group (4.2 +/- 1.5 cm2, p = NS). The area gain due to the myectomy trough was 1.3 +/- 1.0 cm2, corresponding to 48 +/- 12% of the total operative area difference. Maximal systolic depth of the myectomy was 7 +/- 2 mm, maximal width was 20 +/- 8 mm and length was 28 +/- 7 mm. Maximal deviation of the mitral leaflets fell from 15 +/- 7 to 6 +/- 7 mm postoperatively (p < 0.01). In five patients mass measurements of the intracavitary portion of the papillary muscle (PM) revealed an increase from 7.3 +/- 1.0 to 12.1 +/- 2.5 g due to surgical mobilization of PMs (p < 0.01).

CONCLUSIONS

3D TEE quantifies the differences in outflow tract morphology before and after surgery for HOCM. This technique may have an impact on the planning of operative interventions and allow for the evaluation of its results.

Adrenergic control of the force-frequency and relaxation-frequency relations in patients with hypertrophic cardiomyopathy

BACKGROUND

Exercise-induced enhancement of the force-frequency and relaxation-frequency relations has been studied in conscious animals but not in intact diseased human hearts.

METHODS AND RESULTS

We evaluated left ventricular (LV) isovolumic contraction (dP/dt(max)) and relaxation (tau) during atrial pacing and dynamic exercise in 13 patients with nonobstructive hypertrophic cardiomyopathy (HCM) and 7 control subjects to investigate the influence of exercise on the force-frequency and relaxation-frequency relations. Group A consisted of 6 patients in whom the heart rate (HR)-dP/dt(max) relation was markedly enhanced during exercise (88+/-30%) compared with during pacing (34+/-15%). Group B consisted of 7 patients in whom the HR-dP/dt(max) relation showed similar enhancement during exercise (28+/-7%) and atrial pacing (28+/-11%). There was no difference in the HR-tau (derivative method [TD] and pressure half-time method [T(1/2)]) relation between pacing and exercise in groups A and B. Both the mean maximal wall thickness and the hypertrophy score in group B were greater than in group A (27+/-5 versus 19+/-2 mm and 7+/-1 versus 5+/-1 points, respectively; both P<.01). There was no difference in the LV peak systolic pressure, end-diastolic pressure, or the plasma level of catecholamines at baseline, at 50 W of exercise, and at peak pacing between groups A and B. The HR-dP/dt(max) relation in the control group was markedly enhanced during exercise (80+/-27%) compared with during pacing (32+/-14%). The HR-tau relation in the control group was enhanced during exercise (TD, 35+/-9%; T(1/2), 34+/-8%) compared with during pacing (TD, 12+/-7%; T(1/2), 14+/-7%).

CONCLUSIONS

Exercise-induced enhancement of the relaxation-frequency relation was inhibited in all HCM patients, regardless of the degree of LV hypertrophy. The patients without exercise-induced enhancement of the force-frequency relation had more severe LV hypertrophy than the patients with the enhancement, indicating that the adrenergic control of the force-frequency relation may, at least in part, depend on the severity of LV hypertrophy or the stage of HCM.

New diagnostic options in hypertrophic cardiomyopathy

The pathophysiologic features and clinical manifestations of HCM have been elucidated by the introduction of several new diagnostic options. Knowledge of the molecular defects of HCM has advanced rapidly, and genetic screening studies have reemphasized the value of the standard electrocardiogram as an initial screening tool. Analysis of heart rate variability, late potentials, and QT dispersion were not found to be reliable prognostic markers in HCM. However, measurement of dispersion of conduction is probably a sensitive technique in identifying a high risk for sudden cardiac death. Significant developments include transthoracic and transesophageal echocardiography and their role in studying the mitral valve, early detection of left ventricular chamber dilatation, analysis of coronary flow, and intraoperative echocardiography. Finally, advances in the application of magnetic resonance imaging and positron-emission tomography are underway.