Hypertrophic cardiomyopathy. Interrelations of clinical manifestations, pathophysiology, and therapy (1)

Effect of left ventricular outflow tract obstruction on clinical outcome in hypertrophic cardiomyopathy

BACKGROUND

The influence of left ventricular outflow tract obstruction on the clinical outcome of hypertrophic cardiomyopathy remains unresolved.

METHODS

We assessed the effect of outflow tract obstruction on morbidity and mortality in a large cohort of patients with hypertrophic cardiomyopathy who were followed for a mean (+/-SD) of 6.3+/-6.2 years.

RESULTS

Of the 1101 consecutive patients, 273 (25 percent) had obstruction of left ventricular outflow under basal (resting) conditions with a peak instantaneous gradient of at least 30 mm Hg. A total of 127 patients (12 percent) died of hypertrophic cardiomyopathy, and 216 surviving patients (20 percent) had severe, disabling symptoms of progressive heart failure (New York Heart Association [NYHA] functional class III or IV). The overall probability of death related to hypertrophic cardiomyopathy was significantly greater among patients with outflow tract obstruction than among those without obstruction (relative risk, 2.0; P=0.001). The risk of progression to NYHA class III or IV or death specifically from heart failure or stroke was also greater among patients with obstruction (relative risk, 4.4; P<0.001), particularly among patients 40 years of age or older (P<0.001). Age-adjusted multivariate analysis confirmed that outflow tract obstruction was independently associated with an increased risk of both death related to hypertrophic cardiomyopathy (relative risk, 1.6; P=0.02) and progression to NYHA class III or IV or death from heart failure or stroke (relative risk, 2.7; P<0.001). The likelihood of severe symptoms and death related to outflow tract obstruction did not increase as the gradient increased above the threshold of 30 mm Hg.

CONCLUSIONS

In patients with hypertrophic cardiomyopathy, left ventricular outflow tract obstruction at rest is a strong, independent predictor of progression to severe symptoms of heart failure and of death.

Sudden cardiac death

Sudden cardiac death is a rare but devastating event. The majority of cases in young athletes are caused by congenital cardiac abnormalities that are routinely clinically silent before causing sudden death. An optimal screening practice to help identify underlying asymptomatic cardiac abnormalities has met with much debate. Beyond the American Heart Association's recommendations for cardiovascular screening guidelines for the preparticipation physical examination [47], there are conflicting views regarding the use of more advanced diagnostic screening tests. Athletes in whom a potentially life-threatening cardiovascular abnormality is found face the probability of being restricted from participating in certain types of athletic activity. Participation guidelines for athletes with cardiovascular disease are detailed in the recommendations of the 26th Bethesda Conference [36]. Future goals should continue to focus on the prevention of SCD. The development of a cost-effective screening process that incorporates the use of echocardiography, although having its own set of inherent limitations, may prove to be the most viable option.

Prevalence and severity of "benign" mutations in the beta-myosin heavy chain, cardiac troponin T, and alpha-tropomyosin genes in hypertrophic cardiomyopathy

BACKGROUND

Genotype-phenotype correlative studies have implicated 8 particular mutations that cause hypertrophic cardiomyopathy (HCM) as "benign defects," associated with near-normal survival: N232S, G256E, F513C, V606M, R719Q, and L908V of beta-myosin heavy chain (MYH7); S179F of troponin T (TNNT2); and D175N of alpha-tropomyosin (TPM1). Routine genetic screening of HCM patients for specific mutations is anticipated to provide important diagnostic and prognostic information. The frequency and associated phenotype of these mutations in a large, unselected cohort of HCM is unknown.

METHODS AND RESULTS

A total of 293 unrelated HCM patients were genotyped for the presence of a benign mutation. DNA was obtained after informed consent; specific MHY7, TNNT2, and TPM1 fragments were amplified by polymerase chain reaction; and the mutations were detected by denaturing high-performance liquid chromatography and automated DNA sequencing. Only 5 (1.7%) of the 293 patients possessed a benign mutation. Moreover, all 5 subjects with an ascribed benign mutation had already manifested clinically severe expression of HCM, with all 5 requiring surgical myectomy, 3 of the 5 having a family history of sudden cardiac death, and 1 adolescent requiring an orthotopic heart transplant.

CONCLUSIONS

These findings demonstrate the rarity of specific mutations in HCM and challenge the notion of mutation-specific clinical outcomes. Fewer than 2% of the subjects harbored a benign mutation, and those patients with a benign mutation experienced a very serious clinical course.

Coronary artery myogenic response in a genetic model of hypertrophic cardiomyopathy

Hypertrophic cardiac myopathy (HCM) is the leading cause of mortality in young athletes. Abnormalities in small intramural coronary arteries have been observed at autopsy in such subjects. The walls of these intramural vessels, especially in the ventricular septum, are thickened, and the lumen frequently appears narrowed. Whether these morphological characteristics have functional correlates is unknown. We studied coronary myogenic tone in a transgenic mouse model of HCM that has mutations in the cardiac alpha-myosin heavy chain gene. This transgenic mouse has a cardiac phenotype that resembles that occurring in humans. We examined the possible vascular contributions to the pathology of HCM. Septal arteries from 3- and 11-mo-old wild-type (WT) and transgenic (TG) mice were studied on a pressure myograph. The myogenic response to increased intravascular pressure in older animals was significantly reduced [maximal constriction: 32 +/- 4% (TG) and 46 +/- 4% (WT), P < 0.05]. After inhibition of endothelin receptors with bosentan, both WT and TG mice had similar increases in myogenic constriction. The sensitivity to exogenous endothelin was significantly reduced in TG mice, suggesting that the reduced myogenic constriction in HCM was due to reduced receptor sensitivity. In conclusion, we show for the first time that 1) myogenic tone in the coronary septal artery of the mouse is regulated by a basal release of endothelin, and 2) pressure-induced myogenic activation is attenuated in HCM, possibly consequent to a reduction in endothelin responsiveness. The associated reduction in coronary vasodilatory reserve may increase susceptibility to ischemia and arrhythmias.

A novel TPM1 mutation in a family with hypertrophic cardiomyopathy and sudden cardiac death in childhood

We sought to define the pathogenic mutation in a family with hypertrophic cardiomyopathy (HC) and a markedly arrhythmogenic phenotype. The proband was an 8-year-old female with a sentinel event of sudden death. Screening echocardiograms revealed HC in 2 of her 3 siblings and her father. Her youngest male sibling was diagnosed with HC at age 2 years and died suddenly at age 6 years from ventricular fibrillation despite an implanted cardioverter defibrillator. Using DNA extracted from peripheral lymphocytes, linkage exclusion was performed by haplotype analysis of polymorphic markers for the HC genes. Genes not excluded by linkage were analyzed for mutations using denaturing high-performance liquid chromatography (DHPLC) and direct DNA sequencing. Using this strategy, a 610 T>G nucleotide substitution in the alpha-tropomyosin gene (TPM1) was identified resulting in a novel L185R (Leucine [L] to Arginine [R]) missense mutation. This mutation was a spontaneous germ-line mutation originating in the proband's father. L185R-TPM1 cosegregated with family members having clinical evidence of HC, including the proband as confirmed by molecular autopsy. The mutation was not present in 400 reference alleles. Thus, a novel missense mutation in TPM1 was discovered in a family with HC and sudden death in childhood. Unlike previously defined mutations that may disrupt the interactions between alpha-tropomyosin monomers, the L185R mutation may affect troponin-T binding. Defining the pathogenic mutation enabled definitive molecular diagnosis of 2 surviving children.

Difference in coronary blood flow dynamics between patients with hypertension and those with hypertrophic cardiomyopathy

We studied twelve patients with hypertensive left ventricular hypertrophy (LVH), 10 patients with hypertrophic cardiomyopathy (HCM) and 10 control subjects to examine the differences in coronary blood flow (CBF) dynamics between patients with hypertensive LVH and those with HCM. All subjects had normal coronary arteriograms. Measurements of CBF using Doppler Flo-Wire were performed at rest, and after infusions of acetylcholine and papaverine. The baseline CBF was significantly increased in both hypertensive LVH patients and HCM patients compared to that noted in control subjects (64.1+/-36.9, 80.0+/-38.1, 32.3+/-8.0 ml/min, respectively, p<0.01). Coronary flow reserve and endothelium-dependent vasodilatation were significantly lower in hypertensive LVH patients and HCM patients than in control subjects, but there was no significant difference between the hypertensive LVH and HCM patients themselves. In contrast, the diastolic/systolic velocity ratio at baseline was significantly lower in hypertensive LVH patients than in HCM patients (1.53+/-0.40, 6.31+/-7.50, p<0.05). Although CBF and coronary flow reserve correlated positively and negatively, respectively, with left ventricular mass index (r=0.51, -0.59, respectively), the diastolic/systolic velocity ratio at baseline did not show a significant correlation to left ventricular mass index. In conclusion, the diastolic/systolic velocity ratio differed between hypertensive LVH and HCM patients, independent of left ventricular mass. These results suggest that the difference of phasic pattern of CBF may be essential for coronary circulation in patients with hypertensive LVH and in those with HCM.

Scintigraphic assessment of patients with electrocardiographic left ventricular hypertrophy with ST-T changes without apparent cause

PURPOSE

Some patients who show electrocardiographic left ventricular hypertrophy with ST-T changes (ECG-LVH) are difficult to evaluate using routine examinations. To clarify the pathologic process in these patients, the authors performed several scintigraphic examinations.

MATERIALS AND METHODS

Twenty-nine patients with ECG-LVH, without apparent cause, such as left ventricular (LV) systolic overloading or increased LV mass, were examined by myocardial I-123 MIBG imaging, I-123 BMIPP imaging, and exercise-induced stress perfusion imaging. In addition to the visual assessment of each image, we calculated global and regional myocardial washout of I-123 MIBG (%washout). The LV was assessed using conventional echocardiography.

RESULTS

Visually observed abnormalities were located exclusively at the LV apex with all imaging methods and were detected in 76%, 52%, and 17% of patients by I-123 MIBG, I-123 BMIPP, and perfusion imaging, respectively. A follow-up study revealed that the apical defects of I-123 MIBG were subsequently followed by defects of I-123 BMIPP and then perfusion abnormalities. In patients with an apical defect revealed by I-123 MIBG imaging, apical %washout was high. In nine patients who underwent myocardial biopsy, myocardial disarray was observed at the apical regions.

CONCLUSIONS

In many patients with ECG-LVH without apparent cause, sympathetic abnormalities are observed at the apex, similar to pathologic changes in hypertrophic cardiomyopathy. These abnormalities may lead to changes in fatty acid metabolism and perfusion.

Relation between QT duration and maximal wall thickness in familial hypertrophic cardiomyopathy

BACKGROUND

QT abnormalities have been reported in left ventricular hypertrophy and hypertrophic cardiomyopathy.

OBJECTIVE

To determine the relation between left ventricular hypertrophy and increased QT interval in familial hypertrophic cardiomyopathy.

METHODS

The QT interval was measured in 206 genotyped adult subjects with familial hypertrophic cardiomyopathy from 15 unrelated families carrying mutations in the beta myosin heavy chain (beta-MHC) gene (five families, n = 68) or the cardiac myosin binding protein C (MyBPC) gene (10 families, n = 138). Subjects were classified as genetically unaffected (controls, n = 112), affected with left ventricular hypertrophy (penetrants, n = 58), or affected without left ventricular hypertrophy (non-penetrants, n = 36).

RESULTS

There was a significant increase in QTmax and QTmin from controls to non-penetrants and penetrants for both the MyBPC group (p < or = 0.001 and p < or = 0.001, respectively) and the beta-MHC group (p < or = 0.001 and p < or = 0.001, respectively). In the MyBPC group, the increase in the QT interval could be explained by increased left ventricular hypertrophy. In the beta-MHC group, non-penetrants had a significantly longer QTmax than controls despite the absence of left ventricular hypertrophy, and a similar QT interval to penetrants despite a lesser degree of left ventricular hypertrophy.

CONCLUSIONS

In familial hypertrophic cardiomyopathy, genetically affected subjects without left ventricular hypertrophy may have a prolonged QT duration, which depends not only on the degree of left ventricular hypertrophy, when present, but also on the causative mutation.

Role of transcoronary ablation of septal hypertrophy in patients with hypertrophic cardiomyopathy, New York Heart Association functional class III or IV, and outflow obstruction only under provocable conditions

BACKGROUND

Transcoronary ablation of septal hypertrophy (TASH) for hypertrophic cardiomyopathy seems to be an effective alternative to surgical myectomy. It remains a point of debate whether an outflow obstruction at rest is a necessary criterion for interventional therapy.

METHODS AND RESULTS

TASH was compared in 45 consecutive patients with no resting gradient and a provocable gradient of > or =30 mm Hg (group I) and in 84 consecutive patients with a resting gradient of > or =30 mm Hg (80+/-33 mm Hg) (group II). At baseline, all patients were in NYHA functional class (FC) III or IV, unresponsive to medical treatment. Patients in group I were older (63+/-12 versus 55+/-17 years, P=0.005) and had a lower postextrasystolic gradient (110+/-44 versus 171+/-40 mm Hg, P<0.001). The groups were similar with respect to NYHA FC (3.1+/-0.3 versus 3.1+/-0.3), basal septal thickness (22+/-4 versus 23+/-3 mm), maximal oxygen consumption (13.1+/-4.6 versus 14.5+/-5.0 mL/kg per minute), and pulmonary artery mean pressure at workload (42+/-9 versus 42+/-10 mm Hg) (P>0.05). Median follow-up was 7 months after TASH. The 2 groups showed a significant and similar improvement in provocable obstruction (to 24+/-24 and 56+/-51 mm Hg, respectively), basal septal thickness (to 12+/-3 and 12+/-4 mm, respectively), NYHA FC (to 1.7+/-0.6 and 1.5+/-0.6, respectively), maximal oxygen consumption (to 16.0+/-5.3 and 16.6+/-6.0 mL/kg per minute, respectively), and pulmonary artery mean pressure at workload (to 36+/-9 and 34+/-9 mm Hg, respectively) (P>0.05).

CONCLUSIONS

TASH seems to have beneficial clinical and hemodynamic effects in patients with either provocable or resting outflow obstruction.

Prevalence and age-dependence of malignant mutations in the beta-myosin heavy chain and troponin T genes in hypertrophic cardiomyopathy: a comprehensive outpatient perspective

OBJECTIVES

The goal of this study was to determine the prevalence of "malignant" mutations in hypertrophic cardiomyopathy (HCM).

BACKGROUND

Previous genotype-phenotype studies have implicated four mutations (R403Q, R453C, G716R and R719W) as highly malignant defects in the beta-myosin heavy chain (MYH7). In the cardiac troponin T gene (TNNT2), a specific mutation (R92W) has been associated with high risk of sudden death. Routine clinical screening for these malignant mutations has been suggested to identify high-risk individuals.

METHODS

We screened 293 unrelated individuals with HCM seen at the Mayo Clinic in Rochester, Minnesota, between April 1997 and October 2000. Deoxyribonucleic acid (DNA) was obtained after informed consent; amplification of MYH7 exons 13 (R403Q), 14 (R453C) and 19 (G716R and R719W), and TNNT2 exon 9 (R92W) was performed by polymerase chain reaction. The mutations were detected using denaturing high-performance liquid chromatography and automated DNA sequencing.

RESULTS

The mean age at diagnosis was 42 years with 53 patients diagnosed before age 25. The mean maximal left ventricular wall thickness was 21 mm. Nearly one-third of cases were familial and one-fourth had a family history of sudden cardiac death. Only 3 of the 293 patients possessed one of the five "malignant" mutations, and all 3 patients were <25 years of age at presentation (p < 0.006).

CONCLUSIONS

This finding underscores the profound genetic heterogeneity in HCM. Only 1% of unrelated individuals seen at a tertiary referral center for HCM possessed one of the five "malignant" mutations that were examined. Routine clinical testing for these specific mutations is of low yield.

No variants in the cardiac actin gene in Finnish patients with dilated or hypertrophic cardiomyopathy

BACKGROUND

Dilated and hypertrophic cardiomyopathies are primary myocardial diseases that cause considerable morbidity and mortality. Although these cardiomyopathies are clinically heterogeneous, genetic factors play an important role in their etiology and pathogenesis. The defects in the cardiac actin (ACTC) gene can cause both cardiomyopathies. The aim of our study was to screen for variants in the ACTC gene in patients with dilated or hypertrophic cardiomyopathy from Eastern Finland.

MATERIALS AND METHODS

Altogether, 32 patients with dilated and 40 patients with hypertrophic cardiomyopathy were included in the study. Commonly approved diagnostic criteria were applied, and secondary cardiomyopathies were carefully excluded. All 6 exons of the ACTC gene were amplified with polymerase chain reaction and screened for variants with single-strand conformation polymorphism analysis.

RESULTS AND CONCLUSION

We did not find any new or previously reported variants. Our results indicate that defects in the ACTC gene do not explain dilated cardiomyopathy or hypertrophic cardiomyopathy in subjects from Eastern Finland and confirm earlier results that the ACTC gene does not play an important role in the genetics of dilated or hypertrophic cardiomyopathies.

Low-density DNA microarrays are versatile tools to screen for known mutations in hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy (HCM or CMH) is a myocardial disorder caused by mutations that affect the contractile machinery of heart muscle cells. Genetic testing of HCM patients is hampered by the fact that mutations in at least eight different genes contribute to the disease. An affordable high-throughput mutation detection method is as yet not available. Since a significant number of mutations have been repeatedly found in unrelated families, we consider it feasible to pre-screen patients for known mutations, before more laborious techniques capable of detecting new mutations are applied. Here we demonstrate that the principle of hybridization of DNA to oligonucleotide probes immobilized on chips (glass slides) can be applied for this purpose. We have developed a low-density oligonucleotide probe array capable of detecting 12 different heterozygous mutations (in four different genes), among them single- and double-base exchanges, a single nucleotide insertion, and a trinucleotide deletion. The assay is simple and may be amenable to automation. Detection is achieved with a CCD camera-based fluorescence biochip reader. The technique turned out to be robust: Variations in either the relative position of a mutation, or the amount and size of target-DNA were compatible with mutation detection. Mutations could even be detected in amplicons as long as 800 bp, allowing the screening of more than one exon in one amplicon. Our data suggest that the development of a chip that covers all or most of known HCM-associated mutations is feasible and useful.

Risk stratification and prevention of sudden death in hypertrophic cardiomyopathy

Sudden unexpected death, often occurring in young, asymptomatic patients, is the most devastating facet of the natural history of hypertrophic cardiomyopathy, and appears to be the consequence of primary ventricular tachyarrhythmias arising in an electrically unstable myocardial substrate characterized by disorganized cellular architecture, ischemia, cell death, and replacement scarring. Although precise identification of all hypertrophic cardiomyopathy patients at high risk for a catastrophic event is a clinical challenge, effective treatment strategies for the prevention of sudden death with the implantable cardioverter-defibrillator are now available.

B-type natriuretic peptide after percutaneous transluminal septal myocardial ablation

BACKGROUND

Plasma level of B-type natriuretic peptide is a sensitive marker of left ventricular dysfunction and the level is markedly elevated in patients with hypertrophic obstructive cardiomyopathy. Percutaneous transluminal septal myocardial ablation, a catheter-based treatment of hypertrophic obstructive cardiomyopathy, has been widely used as a new therapeutic option for the disease. This study was designed to evaluate clinical implications of natriuretic peptides after the new treatment.

METHODS

Seven consecutive patients with hypertrophic obstructive cardiomyopathy unresponsive to usual medical treatments (age: 57.9+/-22.0 years) were enrolled in the study. Serial changes in atrial and B-type natriuretic peptide in plasma were examined after percutaneous transluminal septal myocardial ablation.

RESULTS

Atrial and B-type natriuretic peptides levels (pg/ml, mean+/-S.D.) at baseline were higher in hypertrophic obstructive cardiomyopathy than in control (80.0+/-43.0 vs. 12.8+/-5.2, P<0.0001; 858.0+/-458.4 vs. 12.4+/-7.0, P<0.0001; respectively). Left ventricular outflow-tract pressure gradient (mmHg) immediately decreased from 115.3+/-23.3 to 30.6+/-12.4 (P<0.0001) after the treatment and concomitantly B-type natriuretic peptide level decreased (858.0+/-458.4 to 264.1+/-137.7, P=0.0084). The level re-increased and peaked at the 2nd day (634.4+/-429.6) and gradually decreased again until 4 weeks. Reduction rate of left ventricular outflow-tract pressure gradient between before and 4 weeks after percutaneous transluminal septal myocardial ablation positively correlated with that of B-type natriuretic peptide (r(2)=0.817, P=0.0053). Changes in atrial natriuretic peptide were not significant in contrast to those of B-type natriuretic peptide.

CONCLUSIONS

Plasma B-type natriuretic peptide level could be useful to predict the effects of percutaneous transluminal septal myocardial ablation in patients with hypertrophic obstructive cardiomyopathy.

New molecular insights into heart failure and cardiomyopathy: potential strategies and therapies

BACKGROUND

In the most severely affected patients the mortality for congestive heart failure exceeds that of many cancers. While therapies are largely aimed at attenuating neurohumoral responses recent molecular insights reveal other potential targets for therapy.

AIMS

To summarise some of the recent developments in the management of heart failure and provide the clinician who treats heart failure with new insights into emerging approaches.

METHODS

A literature review was conducted of the recent literature together with personal research data.

RESULTS

Large randomised trials will provide a more comprehensive understanding of the interaction of beta-blockers and other heart failure therapies with gene polymorphisms. Cytokines are important in the progression of heart failure, yet therapy aimed at blocking cytokine effects has not been successful. More selective use of anti-cytokine therapy may have beneficial effects. Gene therapy to improve heart failure has not yet reached clinical trials. The molecular genetics of hypertrophic and dilated cardiomyopathy is rapidly improving our understanding so that genetic diagnostics and counselling may soon be performed for patients and families.

CONCLUSIONS

The emergence of a molecular based understanding of heart failure will hopefully improve therapy of this common condition.

Sarcomere protein gene mutations in hypertrophic cardiomyopathy of the elderly

BACKGROUND

Hypertrophic cardiomyopathy, a familial myocardial condition caused by sarcomere protein mutations, is usually recognized by early adulthood. Hypertrophic cardiomyopathy of the elderly has similar clinical features but, notably, a later age of onset and noncontributory family history. Causes of elderly-onset hypertrophic cardiomyopathy are unknown.

METHODS AND RESULTS

Eighteen women and 13 men diagnosed with late-onset hypertrophic cardiomyopathy were studied. Initial symptoms occurred at 59.3 (+/-12.3) years, and diagnosis was made at 62.8 (+/-10.8) years. None had family histories of cardiomyopathy. Echocardiography demonstrated maximal left ventricular wall thickness of 19.9+/-3.8 mm, systolic anterior motion of the mitral valve (58%), and, in 11 individuals, left ventricular outflow tract gradients (average, 63+/-42.8 mm). Sarcomere protein gene analyses revealed 8 sequence variants in cardiac myosin binding protein-C (1 nonsense, 1 splice acceptor site, and 3 missense), cardiac troponin I (2 missense), and alpha-cardiac myosin heavy chain (1 missense). Seven variants were not found in over 170 normal chromosomes; 1 variant (cardiac myosin binding protein-C Arg326Gln) also occurred in a healthy adult.

CONCLUSIONS

Hypertrophic cardiomyopathy of the elderly can be a genetic disorder caused by dominant sarcomere protein mutations. The distribution of mutations in elderly-onset disease is strikingly different (P<0.00001) from that of familial, early onset hypertrophic cardiomyopathy. Whereas defects in beta-cardiac myosin heavy chain, cardiac troponin T, and alpha-tropomyosin account for > 45% of familial hypertrophic cardiomyopathy, none were found here. Rather, mutations in cardiac myosin binding protein-C, troponin I, and alpha-cardiac myosin heavy chain caused elderly-onset hypertrophic cardiomyopathy.

Impact of left ventricular outflow tract area on systolic outflow velocity in hypertrophic cardiomyopathy: a real-time three-dimensional echocardiographic study

OBJECTIVES

The aim of this study was to use real-time three-dimensional echocardiography (3DE) to investigate the quantitative relation between minimal left ventricular (LV) outflow tract area (A(LVOT)) and maximal LV outflow tract (LVOT) velocity in patients with hypertrophic obstructive cardiomyopathy (HCM).

BACKGROUND

In patients with HCM, LVOT velocity should change inversely with minimal A(LVOT) unless LVOT obstruction reduces the pumping capacity of the ventricle.

METHODS

A total of 25 patients with HCM with systolic anterior motion (SAM) of the mitral valve leaflets underwent real-time 3DE. The smallest A(LVOT) during systole was measured using anatomically oriented two-dimensional "C-planes" within the pyramidal 3DE volume. Maximal velocity across LVOT was evaluated by two-dimensional Doppler echocardiography (2DE). For comparison with 3DE A(LVOT), the SAM-septal distance was determined by 2DE.

RESULTS

Real-time 3DE provided unique information about the dynamic SAM-septal relation during systole, with A(LVOT) ranging from 0.6 to 5.2 cm(2) (mean: 2.2 +/- 1.4 cm(2)). Maximal velocity (v) correlated inversely with A(LVOT) (v = 496 A(LVOT)(-0.80), r = -0.95, p < 0.001), but the exponent (-0.80) was significantly different from -1.0 (95% confidence interval: -0.67 to -0.92), indicating a significant impact of small A(LVOT) on the peak LVOT flow rate. By comparison, the best correlation between velocity and 2DE SAM-septal distance was significantly (p < 0.01) poorer at -0.83, indicating the superiority of 3DE for assessing A(LVOT).

CONCLUSIONS

Three-dimensional echocardiography-measured A(LVOT) provides an assessment of HCM geometry that is superior to 2DE methods. These data indicate that the peak LVOT flow rate appears to be significantly decreased by reduced A(LVOT). Real-time 3DE is a potentially valuable clinical tool for assessing patients with HCM.

Vascular mechanisms of sudden death in hypertrophic cardiomyopathy, including blood pressure responses to exercise

Approximately a third of patients with hypertrophic cardiomyopathy fail to increase blood pressure appropriately during exercise, a consequence of an inappropriate vasodilator response in nonexercising beds, leading to an exaggerated fall in systemic vascular resistance. The precise mechanism responsible for this abnormal vascular control in hypertrophic cardiomyopathy is still unclear, but is thought to be secondary to enhanced cardiac baroreceptor activity. However, alternate or synergistic mechanisms, including enhanced release of brain natriuretic peptide, may be involved. Normal exercise blood pressure responses have been shown to have a high (97%) negative predictive accuracy for sudden death during an average follow-up of approximately 3 years, providing considerable reassurance. Patients with abnormal blood pressure responses on exercise were at markedly increased risk of sudden cardiac death, although the positive predictive accuracy during this brief follow-up period was low (15%). It is likely that vascular instability may act as a trigger for sudden cardiac death in patients with an underlying electrophysiologic substrate. Recent evidence suggests that this vascular instability may also result in hypotension during ordinary daily activity, or even at rest, and may be an important cause of syncope in hypertrophic cardiomyopathy. Further studies are required to identify mechanisms of attenuating or reversing this vascular instability. Such measures might have the potential to improve symptoms of recurrent syncope and perhaps reduce the risk of sudden cardiac death.

Performing a complete transesophageal echocardiographic examination

Transesophageal echocardiographic (TEE) examination is a powerful and informative cardiac monitor and an important diagnostic tool for use during cardiac surgery. This article reviews how to perform a comprehensive TEE examination on a patient in the operating room and the important clinical uses of TEE during critical events.

[Therapeutic approaches in symptomatic hypertrophic obstructive cardiomyopathy]

Hypertrophic cardiomyopathy is a complex and heterogeneous disease. Although most patients experience just a few symptoms, and have a good prognosis, there are others whose symptoms are severe and progressive, determined by different pathophysiological elements such as diastolic dysfunction, myocardial ischemia, arrhythmias and subaortic obstruction. Approximately 20-30% of hypertrophic cardiomyopathy patients develop an intraventricular dynamic gradient, which in some cases, is responsible for severe symptoms which are ameliorated once the obstruction is reduced. In many cases the symptoms can be controlled with medical treatment which includes betablockers, calcium-channel antagonists and dysopiramide, but some patients will still experience severe and refractory symptoms. This subgroup of patients, which represent approximately 5-10% of patients with hypertrophic cardiomyopathy, can be problematic from a management perspective. For many years, septal myectomy and/or mitral valve replacement offered the only effective alternative therapy for these patients. However, the high rates of morbidity and mortality associated with these procedures have necessitated the search for new and less invasive procedures such as ventricular pacing and percutaneous septal ablation. Although the initial results with sequential pacing were encouraging, further studies have suggested a significant placebo effect, which makes its application controversial. In the last 5 years selective embolization of the septal artery precipitating a localized myocardial infarction has been utilized to reduce the subaortic gradient. The potential indications and efficacy of these new forms of treatment, like ventricular pacing and percutaneous septal ablation, are presently under evaluation and are the main subject of this review. Medical treatment, with either beta-blockers, calcium channel antagonists or dysopiramide constitutes the first therapeutic step. Surgery, while alleviating the subaortic obstruction and reducing the intraventicular pressure and mitral insufficiency, produces important and long-lasting symptomatic and functional improvement in most of these patients, and it continues to be an important therapeutic alternative in these cases. If the first results with sequential pacemaker implants were encouraging, today it is alluded to an important placebo effect that causes its application to be controversial. In the last 5 years the path has been made in the creation of a septal infarction located through the embolization of the septal branches to reduce the gradient.

Does the progression of myocardial fibrosis lead to atrial fibrillation in patients with hypertrophic cardiomyopathy?

The majority of left ventricular (LV) inflow volumes in hypertrophic cardiomyopathy (HCM) depend on atrial contraction because of impaired LV relaxation. If HCM is complicated by atrial fibrillation (AF), heart failure can develop because of the loss of atrial contraction. The purpose of this study was to determine the relationship between the development of AF and myocardial fibrosis or intramyocardial small artery (IMSA) stenosis in autopsied hearts with HCM. Studies were performed in five HCM hearts with AF (AF group) and five HCM hearts without AF (non-AF group). LV specimens were divided into the inner (IT), middle (MT), and outer (OT) thirds. We selected at random 120 fields and 20 IMSAs from each layer and assessed them quantitatively using an image analyzer. We determined the extent of fibrosis (%F) and the degree of stenosis of each IMSA (%L). The %F in the AF group was greater than in the non-AF group (P<.01). In the AF group, the %F of the IT was greater than in the MT and the OT (P<.01). In the non-AF group, the %F of the IT was greater than in the MT (P<.05), and the %F of the MT was greater than in the OT (P<.01). The %L was similar in the AF and non-AF groups. In both groups, the %L of the IT was lower than in the MT (P<.01), which was lower than that of the OT (P<.05). LV fibrosis is more severe in patients with HCM and AF than in those without AF. Therefore, myocardial fibrosis might impair LV relaxation, resulting in hemodynamic intolerance to AF.

Hypertrophic cardiomyopathy with midventricular obstruction and apical aneurysm: a case report

A 71-year-old woman had hypertrophic cardiomyopathy associated with midventricular obstruction and an apical aneurysm in the left ventricle. She had had abnormal electrocardiograms for more than 30 years and for the past year had been suffering from occasional attacks of dizziness and low systemic blood pressure. Holter 24-h electrocardiographic monitoring revealed ventricular paroxysmal contractions (676/day) with nonsustained ventricular tachycardia. Doppler echocardiography revealed paradoxical jet flow from the apical aneurysm to the left ventricular outflow during early diastole. Magnetic resonance imaging depicted midventricular hypertrophy and a dyskinetic thin apical wall, which were confirmed by angiography. Coronary angiograms showed no narrowing of the major extramural coronary arteries, but there was compression of aberrant coronary arteries apparently feeding the hypertrophic portion of the left ventricular wall. Stress thallium-201 myocardial imaging showed a persistent severe defect in the left ventricular apex. A hemodynamic study revealed low cardiac output and an intraventricular pressure gradient (approximately 90 mmHg) between the left ventricular apical high-pressure chamber and the subaortic low-pressure chamber. The present case represents a rare combination of hypertrophic cardiomyopathy, midventricular obstruction, and an apical aneurysm in an elderly woman. Myocardial ischemia may have played an important role in the genesis of the apical aneurysm.

Pressure-guided nonsurgical myocardial reduction induced by small septal infarctions in hypertrophic obstructive cardiomyopathy

OBJECTIVES

We sought to assess the safety and efficacy of pressure-guided nonsurgical myocardial reduction (NSMR) with the induction of small septal infarctions in patients with hypertrophic obstructive cardiomyopathy (HOCM).

BACKGROUND

Nonsurgical myocardial reduction has been shown to decrease left ventricular outflow tract (LVOT) obstruction and to improve symptoms in patients with HOCM. Infarct sizes differ considerably among studies published so far.

METHODS

In 50 patients, the LVOT gradient was invasively determined at the time of the intervention, four to six months (n = 49) and 12 to 18 months (n = 25) after NSMR. New York Heart Association functional class and quality of life were assessed by using a standard questionnaire. Exercise capacity was tested by spiro-ergometry. Left ventricular (LV) mass was determined by electron beam computed tomography.

RESULTS

Small septal infarctions (mean creatine kinase value 413 +/- 193 U/l) resulted in a sustained decrease in LVOT gradients, from 80 +/- 33 to 18 +/- 17 mm Hg after four to six months (p < 0.001, n = 49) and to 17 +/- 15 mm Hg (p < 0.001, n = 25) after 12 to 18 months. Nonsurgical myocardial reduction was followed by a decrease in LV hypertrophy, which was associated with a sustained increase in exercise capacity, as well as improvement in quality of life.

CONCLUSIONS

Pressure-guided NSMR inducing small septal infarctions was sufficient to result in a sustained decrease in LVOT obstruction and to improve symptoms. The incidence of complications, such as complete heart block with necessary permanent pacemaker implantation (<10%), seems to be diminished by minimizing the infarct size.

Stress-induced changes in subendocardial tissue texture in hypertrophic cardiomyopathy: an echocardiographic videodensitometric study

BACKGROUND

Myocardial ischemia changes myocardial acoustic properties, inducing increase of integrated backscatter and blunting of cyclic variation of backscatter. Stress-induced subendocardial underperfusion has been demonstrated in patients with hypertrophic cardiomyopathy (HCM).

AIM

To evaluate the potential of a videodensitometric approach in assessing transmural ultrasonic tissue changes in HCM during dipyridamole infusion.

METHODS

Twenty-two patients (13 males, 50+/-12 years) with HCM underwent dipyridamole echo testing (DET). Myocardial gray levels amplitude was calculated off-line on digitized images in the left subendocardial (LV-endo), right subendocardial (RV-endo) region of the interventricular septum and posterior wall (long axis parasternal view).

RESULTS

The thickness of the interventricular septum and posterior wall was 1.9+/-0.3 and 1.17+/-2.1 cm, respectively. In the LV-endo layer, the cyclic variation was blunted during DET (rest = 37+/-14 vs. DET 27+/-20%, p < 0.02). In the RV-endo layer and posterior wall, no changes occurred. In the LV-endo layer of the septum, blunting of cyclic variation was more pronounced in the 10 patients with than in the 12 without ST-segment depression during DET (21.2+/-14.7% vs. 43.8+/-15.8, p < 0.01).

CONCLUSIONS

In HCM patients, DET induced blunting of cyclic variation without the evidence of wall motion abnormalities. This reduction was more pronounced when electrocardiographic signs of ischemia were simultaneously elicited by DET.

Evaluation of the athlete who 'goes to ground'

The athlete represents the healthiest segment of our society. Yet, there are still reports of sudden death occurring while on the athletic field. Any athlete who 'goes to ground' temporarily (syncope) warrants an immediate investigation. The differential diagnosis of syncope is wide-ranging. However, if a cardiac cause is the underlying etiology of an athlete with syncope, and that athlete participates and has another syncopal episode the likelihood of resuscitation may be quite low. This article reviews the most common causes of sudden death in athletes (hypertrophic cardiomyopathy, anomalous coronary arteries, arrhythmogenic right ventricular cardiomyopathy, myocarditis, and dilated cardiomyopathy). Important attention will be centered on the pathophysiology of each abnormality and how it contributes to symptoms of syncope and sudden death. Also, the ideal evaluation of each will be reviewed. Recommendations regarding eligibility for competition in sports with each underlying abnormality will be reviewed. In addition, this article will review the evaluation of children and young adults who wish to participate in athletics.

Evaluation of septal hypertrophy and systolic function in diseases that cause left ventricular hypertrophy: a 3-dimensional echocardiography study

OBJECTIVES

The goals of this study were to determine regional systolic function of the septum and to relate it to regional wall thickness and wall stress.

BACKGROUND

Wall thickening, a parameter of systolic function, is determined by wall thickness and wall stress. In patients with hypertrophic obstructive cardiomyopathy (HOCM), hypertrophic nonobstructive cardiomyopathy (HNCM), and hypertensive heart disease (HHD), regional systolic function of normal and hypertrophic septal regions has been incompletely characterized by 2-dimensional echocardiography. Thus, multiplane transesophageal echocardiography with 3-dimensional reconstruction of the septum was used.

METHODS AND RESULTS

In 49 patients (15 controls, 11 with HOCM, 8 with HNCM, and 15 with HHD) 4 parallel (2 basal and 2 apical) equidistant short-axis cross sections from base to apex were obtained from the reconstructed septum. In each short-axis cross section, 6 wall-thickness measurements were made in 15 degrees intervals at end diastole and end systole, for a total of 48 measurements in each patient. Fractional thickening was calculated as wall thickening divided by end-diastolic wall thickness. Wall thickness of the basal cross sections was significantly thicker (P < .001) in HOCM and HNCM than in HHD. However, circumferential wall thickness was more evenly distributed in HNCM and HHD when compared with HOCM. In the basal cross sections, fractional thickening was similarly reduced in all hearts, though basal wall stress was significantly different in all groups (P < .001). In the apical cross sections, wall thickness was similar in all diseased hearts, but fractional thickening was better (P < .001) and wall stress lower (P < .001) in HNCM than in HOCM and HHD.

CONCLUSIONS

In septal regions without or with only mild hypertrophy, regional systolic function is preserved and appears to be determined by hemodynamic factors such as wall stress. However, in regions with moderate to severe hypertrophy, systolic function is markedly and uniformly impaired in all groups, which seems not to be caused by differences in wall thickness and wall stress but by the degree of the myocardial disease process.

Cardiac troponin T Arg92Trp mutation and progression from hypertrophic to dilated cardiomyopathy

BACKGROUND

Mutations in the cardiac troponin T gene causing familial hypertrophic cardiomyopathy (HCM) are associated with a very poor prognosis but only mild hypertrophy. To date, the serial morphologic changes in patients with HCM linked to cardiac troponin T gene mutations have not been reported.

HYPOTHESIS

The aim of this study was to determine the long-term course of patients with familial HCM caused by the cardiac troponin T gene mutation, Arg92Trp.

METHODS

In all, 140 probands with familial HCM were screened for mutations in the cardiac troponin T gene.

RESULTS

The Arg92Trp missense mutation was present in 10 individuals from two unrelated pedigrees. They exhibited different cardiac morphologies: three had dilated cardiomyopathy-like features, five had asymmetric septal hypertrophy with normal left ventricular systolic function, one had electrocardiographic abnormalities without hypertrophy, and one had the disease-causing mutation but did not fulfill the clinical criteria for the disease. The mean maximum wall thickness was 14.1 +/- 6.0 mm. The three patients with dilated cardiomyopathy-like features had progressive left ventricular dilation. Three individuals underwent right ventricular endomyocardial biopsy. There was a modest degree of myocardial hypertrophy (myocyte diameter: 18.9 +/- 5.2 microm), and minimal myocardial disarray and mild fibrosis were noted.

CONCLUSION

The Arg92Trp substitution in the cardiac troponin T gene shows a high degree of penetrance, moderate hypertrophy, and early progression to dilated cardiomyopathy in Japanese patients. Early identification of individuals with this mutation may provide the opportunity to evaluate the efficacy of early therapeutic interventions.

Clinical significance of atrial fibrillation in hypertrophic cardiomyopathy

Atrial fibrillation (AF) is the most common sustained arrhythmia in patients with hypertrophic cardiomyopathy (HCM), and it bears numerous pathophysiologic consequences that potentially affect patient outcome and symptoms. However, studies regarding the impact of AF on the long-term prognosis of HCM patients have been limited in number, with sometimes conflicting results. Recently, studies on community-based patient populations showed that AF is associated with long-term clinical deterioration, embolic complications, and increased cardiovascular mortality due to heart failure and stroke. The consequences of AF on the long-term prognosis of HCM patients are not uniformly unfavorable, however, and in about one third of patients the arrhythmia is compatible with an uneventful course.

Value of exercise testing in assessing clinical state and prognosis in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the sarcomeric contractile proteins. A majority of patients with HCM are limited in terms of functional capacity, and a minority of these patients die suddenly. The main aims of management are symptom alleviation and prevention of sudden cardiac death. In patients with HCM, cardiopulmonary exercise testing provides a much more accurate index of functional capacity than New York Heart Association classification status, and it is useful in assessing symptoms after various therapeutic strategies have been implemented. Exercise testing is also valuable in identifying patients with HCM who are at high risk of sudden cardiac death and is an integral part of the algorithm in risk stratification and delivery of prophylactic therapy. Also, cardiopulmonary exercise testing plays an important role in differentiating HCM from other conditions associated with left ventricular hypertrophy, such as physiologic athlete's heart. Therefore, during the last few years, cardiopulmonary exercise testing has provided insights into the diagnosis, determinants, and mechanisms of exercise limitation in HCM. This understanding aids physicians in targeting therapy and developing new treatment modalities.

The role of exercise testing in the evaluation of the patient with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the sarcomeric contractile proteins that is characterized by left ventricular hypertrophy and myocyte disarray. The majority of patients are limited in terms of functional capacity and a minority die suddenly. The main aims of management are symptom alleviation and prevention of sudden cardiac death. In patients with HCM, cardiopulmonary exercise testing provides a more accurate index of functional capacity than New York Heart Association classification status and is useful in assessing symptoms following various therapeutic interventions. Cardiopulmonary exercise testing plays an important role in differentiating HCM from other conditions associated with left ventricular hypertrophy. Cardiopulmonary exercise testing is also valuable in identifying individuals at high risk of sudden cardiac death and is an integral part of the algorithm in risk stratification and delivery of prophylactic therapy. Over the past few years, cardiopulmonary exercise testing has provided insight into the determinants and mechanisms of exercise limitation. This understanding helps in targeting therapy and the development of new treatment modalities.

Gender and aging in a transgenic mouse model of hypertrophic cardiomyopathy

Mutations in the cardiac myosin heavy chain (MHC) can cause familial hypertrophic cardiomyopathy (FHC). A transgenic mouse model has been developed in which a missense (R403Q) allele and an actin-binding deletion in the alpha-MHC are expressed in the heart. We used an isovolumic left heart preparation to study the contractile characteristics of hearts from transgenic (TG) mice and their wild-type (WT) littermates. Both male and female TG mice developed left ventricular (LV) hypertrophy at 4 mo of age. LV hypertrophy was accompanied by LV diastolic dysfunction, but LV systolic function was normal and supranormal in the young TG females and males, respectively. At 10 mo of age, the females continued to present with LV concentric hypertrophy, whereas the males began to display LV dilation. In female TG mice at 10 mo of age, impaired LV diastolic function persisted without evidence of systolic dysfunction. In contrast, in 10-mo-old male TG mice, LV diastolic function worsened and systolic performance was impaired. Diminished coronary flow was observed in both 10-mo-old TG groups. These types of changes may contribute to the functional decompensation typically seen in hypertrophic cardiomyopathy. Collectively, these results further underscore the potential utility of this transgenic mouse model in elucidating pathogenesis of FHC.

Current management of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is a familial cardiac disorder with heterogeneous expression and a diversity of morphological, functional and clinical features. Some individuals with hypertrophic cardiomyopathy may be asymptomatic while others are disabled by symptoms of angina and breathlessness. This article summarizes the genetics, pathophysiology and present management of this important condition.

Clinical and echocardiographic features of hypertrophic cardiomyopathy in the elderly

Hypertrophic cardiomyopathy is a familial cardiac disease with exceptionally diverse clinical and morphologic presentations. The influence of age on the disease manifestation has become increasingly clear over the last decade. Most initial reports concentrated on characterization and treatment of the disease in younger individuals, but a better appreciation of hypertrophic cardiomyopathy in elderly patients has yielded important information regarding clinical presentation, morphologic appearance on echocardiography, prognosis, and management. This paper reviews the literature focusing on the age-related differences in hypertrophic cardiomyopathy.

[Value of Doppler-echocardiography in the prognosis and follow up of hypertrophic myocardiopathy]

INTRODUCTION AND OBJECTIVES

The aim of this study was to assess the value of Doppler-echocardiogram for the prognosis and follow up of a hospital-based series of adult patients with hypertrophic cardiomyopathy (HC).

METHODS

One-hundred nineteen consecutive patients with HC (52 +/- 12 years, 60 women) were studied over a follow up period of 9.7 +/- 6.7 years. Echocardiographic evolution was analyzed in 104 patients (67 with dynamic obstruction) who had, at least, two echocardiograms performed within an interval of 3.7 +/- 3 years (1 to 7 years).

RESULTS

Seven patients died during follow up and 31 patients developed severe complications (7 deaths, 15 syncopes, 4 class IV angina, 3 class IV dyspnea and 2 acute myocardial infarctions). The presence of mitral insufficiency (p = 0.001) and dynamic gradient > 50 mmHg (p = 0.02) were predictive of mortality and a left atrial index > 25 mm/m2 was predictive (p = 0.028) of severe complications. Fifteen percent of the patients without dynamic obstruction in the first Doppler-echo showed a gradient > 25 mmHg in the last echo. A greater number of patients with mitral insufficiency (80% vs 66%; p = 0.01) and an increase in its severity (p = 0.038) was observed during follow up.

CONCLUSIONS

Mitral insufficiency, a dynamic gradient > 50 mmHg and a left atrial index > 25 mm/m2 are variables of a bad prognosis in adult patients with HC. An evolution to obstructive HC was observed in 15% of non obstructive HC, and a tendency to increased severity of mitral insufficiency was observed during follow up.

Molecular medicine in the 21st century

When Watson and Crick proposed the double helix model for DNA structure in a 2 page Nature article in 1953, no one could have predicted the enormous impact this finding would have on the study of human disease. Over the last decade in particular, major advances have been made in our understanding of both normal biological processes and basic molecular mechanisms underlying a variety of medical diseases. Knowledge obtained from basic cellular, molecular and genetic studies has enabled the development of strategies for the modification, prevention and potential cure of human diseases. This brief overview focuses on the enormous impact molecular studies have had on various aspects of medicine. The inherited cardiac disorder hypertrophic cardiomyopathy is used here as a model to illustrate how molecular studies have not only redefined 'gold standards' for diagnosis, but have also influenced management approaches, increased our understanding of fundamental disease-causing mechanisms and identified potential targets for therapeutic intervention. The near-completion of the Human Genome Project, which identifies the 3.2 billion base pairs that comprise the human genome (the so-called 'Book of Life'), has exponentially heightened the focus on the importance of molecular studies and how such studies will impact on various aspects of medicine in the 21st century.

Hemodynamic benefits of treatment modalities for hypertrophic cardiomyopathy: a case study

Hypertrophic cardiomyopathy is a primary disease of the cardiac muscle characterized by a hypertrophied and nondilated left ventricle in the absence of other cardiac or systemic disease. The disorder occurs twice as often in men than in women and is relatively more common in young adults. Early treatment of symptoms may improve hemodynamic benefits and prevent complications, including sudden death. This case illustrates various treatment modalities used to manage symptoms and describes the challenges in effectively maintaining hemodynamic stability.

An abnormal Ca(2+) response in mutant sarcomere protein-mediated familial hypertrophic cardiomyopathy

Dominant-negative sarcomere protein gene mutations cause familial hypertrophic cardiomyopathy (FHC), a disease characterized by left-ventricular hypertrophy, angina, and dyspnea that can result in sudden death. We report here that a murine model of FHC bearing a cardiac myosin heavy-chain gene missense mutation (alphaMHC(403/+)), when treated with calcineurin inhibitors or a K(+)-channel agonist, developed accentuated hypertrophy, worsened histopathology, and was at risk for early death. Despite distinct pharmacologic targets, each agent augmented diastolic Ca(2+) concentrations in wild-type cardiac myocytes; alphaMHC(403/+) myocytes failed to respond. Pretreatment with a Ca(2+)-channel antagonist abrogated diastolic Ca(2+) changes in wild-type myocytes and prevented the exaggerated hypertrophic response of treated alphaMHC(403/+) mice. We conclude that FHC-causing sarcomere protein gene mutations cause abnormal Ca(2+) responses that initiate a hypertrophic response. These data define an important Ca(2+)-dependent step in the pathway by which mutant sarcomere proteins trigger myocyte growth and remodel the heart, provide definitive evidence that environment influences progression of FHC, and suggest a rational therapeutic approach to this prevalent human disease.

Electromyographic evidence of subclinical myopathy in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is due to a number of mutations of contractile protein genes such as beta-cardiac myosin, myosin binding protein-C, and troponin-T. Unlike troponin-T, beta-myosin is a constituent of slow skeletal muscle and its mutations generally have a better prognosis. In order to investigate the usefulness of electromyography in detecting skeletal muscle involvement in HCM, 46 patients were examined using both conventional electromyography (EMG) and quantitative electromyography (QEMG) methods. The QEMG involved motor unit potential (MUP) analysis, turns/amplitude (TAA) analysis, and power spectrum analysis of the interference pattern. Using conventional EMG, myopathic findings were demonstrated in 13 patients (28%). Receiver operating characteristic (ROC) analysis of the results of a discriminant function extracted using QEMG values, identified correctly 10 out of 11 normal controls and all 9 myopathic control patients, and displayed a 15% presence of myopathy (7 patients) among the cardiomyopathy group. The duration of MUPs was the most sensitive among the quantitative parameters in differentiating normal from myopathic subjects. Since skeletal muscle involvement may be due to distinct gene mutations, normal and myopathic EMG findings may reflect HCM subpopulations with a different genetic substrate.

[Usefulness of contrast echocardiography with harmonic imaging in a patient with hypertrophic cardiomyopathy and midventricular obstruction]

Echocardiography is routinely used for the evaluation of cardiac function. Definition of the endocardial border is essential for the assessment of global and regional left ventricular contractility. This is sometimes difficult due to an inadequate acoustic window. New echocardiographic techniques may be useful to accurate and noninvasively diagnose certain conditions which may otherwise remain undiagnosed with traditional techniques. We present a case of a patient diagnosed with segmental wall motion abnormalities (lateral and apical hypokinesis) by conventional echocardiography. The use of harmonic imaging with contrast changed the initial diagnosis and the patient was diagnosed with severe hypertrophic cardiomyopathy with midventricular obstruction, without segmental wall motion abnormalities.

Ventricular arrhythmias, sudden death, and prevention in patients with hypertrophic cardiomyopathy

Sudden unexpected death, often occurring in young asymptomatic patients, is the most devastating facet of the natural history of hypertrophic cardiomyopathy (HCM). It appears to be the consequence of primary ventricular tachyarrhythmias arising in an electrically unstable myocardial substrate characterized by disorganized cellular architecture, ischemia, cell death, and replacement scarring. Although identification of the HCM patient subset at high risk for a catastrophic event with precision continues to present challenges, treatment strategies for the prevention of sudden death are now available. In particular, the implantable cardioverter-defibrillator has a high degree of efficacy in sensing and terminating potentially lethal ventricular tachyarrhythmias and a life-saving role in both the primary and secondary prevention of sudden cardiac death in HCM.

Marked ventricular repolarization abnormalities in highly trained athletes' electrocardiograms: clinical and prognostic implications

OBJECTIVE

We sought to study the functional, clinical and prognostic implications of marked repolarization abnormalities (MRA) sometimes seen in athletes' electrocardiograms (ECGs).

BACKGROUND

The clinical meaning of ECG MRA in athletes is unknown. No relationship has been drawn between either training intensity or any particular type of sport and MRA. Athletes are usually symptom free and do not show any decrease in their physical performance. It is as yet unclear whether MRA may have a negative effect on the performance of such athletes in competitive sports.

METHODS

We studied 26 athletes with MRA (negative T waves > or =2 mm in three or more ECG leads at rest). No athletes presented clinical symptoms of cardiac disease or decrease in their physical performance. Clinical and physical examinations, ECG at rest, exercise test and echocardiographic and antimyosin studies were performed in all athletes. Rest/exercise myocardial perfusion single-photon emission computed tomography studies were performed in 17 athletes. The follow-up ranged from 4 to 20 years (mean 6.7 years).

RESULTS

Four athletes were excluded due to hypertrophic cardiomyopathy. Echocardiographic studies showed right and left normal ventricular dimensions for highly conditioned athletes. In the exercise test, heart rate was 166 +/- 12.4 beats/min, and exercise tolerance was 15.2 +/- 2.7 metabolic equivalents of the task. All athletes had ECG at rest simulating myocardial ischemia or "pseudoischemia" with a tendency to normalize during exercise. Myocardial perfusion studies were normal in the studied athletes. Antimyosin studies showed mild and diffuse myocardial radiotracer uptake in 15 athletes (68%). No adverse clinical events were observed in the follow-up.

CONCLUSIONS

These results suggest that MRA have no clinical or pathological implications in athletes and should, therefore, not preclude physical training or participation in sporting events.

Noninvasive indexes of left atrial diastolic function in hypertrophic cardiomyopathy

OBJECTIVES

Our goal was to noninvasively assess left atrial diastolic function and its relation to the impaired left ventricular filling in patients with hypertrophic cardiomyopathy.

METHODS AND RESULTS

We studied 34 patients with hypertrophic cardiomyopathy, 26 patients with secondary forms of left ventricular hypertrophy (aortic stenosis, fixed subaortic stenosis, hypertension), and 21 control subjects. Left atrial diastolic function was assessed by measuring acceleration time (SAT), deceleration time (SDT), and the EF (mean deceleration rate) slope of the pulmonary venous flow systolic wave (SW). Left ventricular diastolic function assessed by transmitral Doppler included peak early left ventricular and peak atrial filling velocities, the ratio of early-to-late peak velocities, isovolumic relaxation time, deceleration time, and EF slope. In patients with hypertrophic cardiomyopathy, acceleration time was significantly reduced (P<.05), deceleration time was significantly prolonged (P<.0001), and EF slope was significantly reduced (P<.01). These indexes were similar among the other two groups. No statistically significant difference existed between the subgroups of hypertrophic cardiomyopathy in the above indexes. Patients with hypertrophic cardiomyopathy and secondary forms of left ventricular hypertrophy had evidence of left ventricular diastolic dysfunction. In patients with hypertrophic cardiomyopathy, no correlation existed between left atrial and left ventricular diastolic function indexes (r = -0.26 to 0.33).

CONCLUSIONS

Echocardiographic indexes of left atrial relaxation and filling are abnormal in patients with hypertrophic cardiomyopathy but not in secondary forms of left ventricular hypertrophy. These indexes are abnormal in all forms of hypertrophic cardiomyopathy irrespective of left ventricular outflow tract obstruction and distribution of hypertrophy; they are not solely attributable to left ventricular diastolic dysfunction. The above may imply that hypertrophic cardiomyopathy is a cardiac myopathic disease that involves the heart muscle as a whole, irrespective of distribution of hypertrophy and obstruction.

Utility of metabolic exercise testing in distinguishing hypertrophic cardiomyopathy from physiologic left ventricular hypertrophy in athletes

OBJECTIVES

This study evaluated the role of metabolic (cardiopulmonary gas exchange) exercise testing in differentiating physiologic LVH in athletes from HCM.

BACKGROUND

Regular intensive training may cause mild increases in left ventricular wall thickness (LVWT). Although the degree of left ventricular hypertrophy (LVH) is typically less than that seen in hypertrophic cardiomyopathy (HCM), genetic studies have shown that a substantial minority of patients with HCM have an LVWT in the same range. The differentiation of physiologic and pathologic LVH in this "gray zone" can be problematic using echocardiography and electrocardiography alone.

METHODS

Eight athletic men with genetically proven HCM and mild LVH (13.9 +/- 1.1 mm) and eight elite male athletes matched for age, size and LVWT (13.4 +/- 0.9 mm) underwent symptom limited metabolic exercise stress testing. Peak oxygen consumption (pVO2), anaerobic threshold, oxygen pulse and respiratory exchange ratios were measured in both groups and compared with those observed in 12 elite and 12 recreational age- and size-matched athletes without LVH.

RESULTS

Elite athletes with LVH had significantly greater pVO2 (66.2 +/- 4.1 ml/kg/min vs. 34.3 +/- 4.1 ml/kg/min; p < 0.0001), anaerobic threshold (61.6 +/- 1.8% of the predicted maximum VO2 vs. 41.4 +/- 4.9% of the predicted maximum VO2; p < 0.001) and oxygen pulse (27.1 +/- 3.2 ml/beat vs. 14.3 +/- 1.8 ml/beat; p < 0.0001) than individuals with HCM. A pVO2 >50 ml/kg/min or >20% above the predicted maximum VO2 differentiated athlete's heart from HCM.

CONCLUSIONS

Metabolic exercise testing facilitates the differentiation between physiologic LVH and HCM in individuals in the "gray zone."

Epidemiology of hypertrophic cardiomyopathy-related death: revisited in a large non-referral-based patient population

BACKGROUND

Death resulting from hypertrophic cardiomyopathy (HCM), particularly when sudden, has been reported to be largely confined to young persons. These data emanated from tertiary HCM centers with highly selected referral patterns skewed toward high-risk patients.

METHODS AND RESULTS

The present analysis was undertaken in an international population of 744 consecutively enrolled and largely unselected patients more representative of the overall HCM spectrum. HCM-related death occurred in 86 patients (12%) over 8+/-7 years (mean+/-SD). Three distinctive modes of death were as follows: (1) sudden and unexpected (51%; age, 45+/-20 years); (2) progressive heart failure (36%; age, 56+/-19 years); and (3) HCM-related stroke associated with atrial fibrillation (13%; age, 73+/-14 years). Sudden death was most common in young patients, whereas heart failure- and stroke-related deaths occurred more frequently in midlife and beyond. However, neither sudden nor heart failure-related death showed a statistically significant, disproportionate age distribution (P=0.06 and 0.5, respectively). Stroke-related deaths did occur disproportionately in older patients (P=0.002). Of the 45 patients who died suddenly, most (71%) had no or mild symptoms, and 7 (16%) participated in moderate to severe physical activities at the time of death.

CONCLUSIONS

HCM-related cardiovascular death occurred suddenly, or as a result of heart failure or stroke, largely during different phases of life in a prospectively assembled, regionally based, and predominantly unselected patient cohort. Although most sudden deaths occurred in adolescents and young adults, such catastrophes were not confined to patients of these ages and extended to later phases of life. This revised clinical profile suggests that generally held epidemiological tenants for HCM have been influenced considerably by skewed reporting from highly selected populations. These data are likely to importantly affect risk stratification and treatment strategies importantly for the prevention of sudden death in HCM.