Hypertrophic cardiomyopathy

Hypertrophic Cardiomyopathy: Current Treatment and Future Options

Hypertrophic cardiomyopathy (HCM) is a disease involving the cardiac sarcomere. It is associated with various disease-causing gene mutations and phenotypic expressions, managed with different therapies with variable prognoses. The heterogeneity of the disease is evident in the fact that it burdens patients of all ages. HCM is the most prevalent cause of sudden death in athletes. However, several technological advancements and therapeutic options have reduced mortality in patients with HCM to 0.5% per year. In addition, rapid advances in our knowledge of the molecular defects accountable for HCM have strengthened our awareness of the disorder and recommended new approaches to the assessment of prognosis. Despite all these evolutions, a small subgroup of patients with HCM will experience sudden cardiac death, and risk stratification remains a critical challenge. This review provides a practical guide to the updated recommendations for patients with HCM, including clinical updates for diagnosis, family screening, clinical imaging, risk stratification, and management.

Lifestyle Modification and Medical Management of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is a heterogenous condition associated with a myriad of symptoms. Just as in other disease states, the aim of medical therapy is the alleviation of suffering, improvement of longevity, and the prevention of complications. This article focuses on the associated comorbidities seen in patients with hypertrophic cardiomyopathy, potential lifestyle interventions, and conventional medical treatments for symptomatic hypertrophic cardiomyopathy.

Left ventricular outflow tract obstruction-be prepared!

The current trend to treat hypotension in critically ill patients is to place a greater emphasis on inotropic support and less on fluid resuscitation in order to limit the potential harm from fluid overload. This combination may trigger left ventricular outflow tract obstruction (LVOTO) in susceptible patients. Although LVOTO is classically described in patients with hypertrophic cardiomyopathy it has been reported in other conditions including septic shock, apical ballooning syndrome, myocardial infarction, respiratory failure, and post valvular surgery. It is more common in the elderly, females, and in patients with hypertension, diabetes, and chronic vascular disease because of predisposing anatomical conditions such as left ventricular hypertrophy, small left ventricle size, sigmoid septum and alterations in the positions of the aortic and mitral valve annular planes. The onset of LVOTO is largely unpredictable due to a complex interplay between preload, afterload, heart rhythm and rate in susceptible patients. The consequences of missing this treatable condition may lead to life-threatening hypotension refractory to, or exacerbated by, a further increase in inotropic support. Dynamic LVOTO should be considered in any hypotensive intensive care patient. Echocardiography is perhaps the best tool to assess LVOTO and its underlying pathophysiology in the critically ill. Detection of LVOTO is a relatively simple task using a combination of two-dimensional, M-mode and spectral Doppler imaging by an operator alert to the possible diagnosis.

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

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

The progression of left ventricular systolic and diastolic dysfunctions in hypertrophic cardiomyopathy: clinical and prognostic significance

OBJECTIVES

The significance of the progression of systolic and diastolic dysfunctions in hypertrophic cardiomyopathy (HCM) is still an open issue. We sought to evaluate the clinical and prognostic implications of the progression of left ventricular systolic and diastolic dysfunction in HCM.

METHODS

One hundred one HCM patients were studied by echo-Doppler at baseline and during follow-up.

RESULTS

During a follow-up of 109 + or - 67 months, 28% of patients showed a progression to left ventricular diastolic dysfunction, defined as restrictive filling pattern (RFP), and 16% to left ventricular systolic dysfunction (left ventricular ejection fraction <50%). The 10-year heart transplant-free survival rate was 45% in patients with RFP at follow-up vs. 82% in the patients without RFP (P < 0.001), and 52% in patients with left ventricular systolic dysfunction at follow-up vs. 75% in the patients with left ventricular ejection fraction of at least 50% (P = 0.001). Baseline predictors of death/transplantation were New York Heart Association class III-IV, indexed left atrial diameter, and RFP. When RFP and left ventricular systolic dysfunction were added at follow-up, both emerged as prognostic predictors (RFP: hazard ratio 8.92, 95% confidence interval 2.5-31.86; systolic dysfunction: hazard ratio 25.35, 95% confidence interval 3.57-179.88) with a significant increase of area under the receiver-operating characteristic curves (0.81 vs. 0.70, P = 0.03) with respect to the baseline model.

CONCLUSION

Left ventricular diastolic and/or systolic dysfunction at follow-up are relatively frequent in HCM and are associated with a poor prognosis.

Sudden cardiac death in a 20-year-old male swimmer

In young adults, hypertrophic obstructive cardiomyopathy (HOCM) is an acknowledged risk factor for sudden cardiac death (SCD) in an otherwise healthy and active patient. While the incidence of SCD in young people is not high enough for extensive, wide-scale examinations, the potential for prevention of some deaths via pre-exercise imaging may be beneficial in certain patient populations, such as those with a family history of SCD or professional athletes. We present the case of a healthy 20-year-old man with no past medical history who died while swimming in a river, likely secondary to cardiac arrest in the setting of HOCM.

Pre-participation Cardiovascular Screening of Elderly Wrestlers

Purpose

Sudden death of a competitive athlete is a tragedy that is usually caused by a previously unsuspected cardiovascular disease. The aim of this study was to clarify the role of noninvasive testing in pre-participation cardiovascular evaluation of elderly wrestlers.

Methods

We included 63 Iranian elderly wrestlers who participated in Tehran international elderly wrestlers’ preparation camping by census method. A questionnaire including past medical and family history as well as coronary risk factors was filled out and then a complete physical examination of the cardiovascular system was done by an internist for all wrestlers. Electrocardiogram (ECG), complete echocardiographic examination and then symptom limited exercise test were performed and reported by the cardiologists who did not know the other examinations results.

Results

Exertional dyspnea and typical chest pain (FC=I or II) were present in 5% and 1.7% of the examinees, respectively. There were one or more risk factors in 64.5% of the cases. Cardiovascular examination revealed abnormal heart sounds in 27.1%. ECG showed ischemic changes in 13.6% and premature atrial contractions and premature ventricular contractions in 11.4%. Echocardiography showed mild left ventricular systolic dysfunction in 3.4%, regional wall motion abnormality in 8.5%, valvular disease in 32.3%, diastolic dysfunction in 45.7%, and left ventricular hypertrophy in 16.9% of the cases. Exercise test results were negative, equivocal, positive and highly positive in 70.4%, 15.8%, 5.2%, and 8.6% of cases, respectively.

Conclusion

Beside physical examination, pre-participation screening of elderly wrestling athletes with ECG and exercise testing is feasible and recommended in the presence of coronary risk factors or cardiac symptoms. Echocardiography can also be recommended to detect other relevant abnormalities when there is a clue in the standard history, physical examination or ECG.

Rare clinical presentation of nonobstructive hypertrophic cardiomyopathy: Apical aneurysm with thrombus

Hypertrophic cardiomyopathy patients rarely have left ventricular apical aneurysms without coronary artery disease and the pathophysiological processes responsible for apical wall thinning and aneurysm formation are not known exactly today. Here we present a rare nonobstructive hypertrophic cardiomyopathy case with an apical thrombotic aneurysm.

Prognosis and prognostic factors in patients with hypertrophic cardiomyopathy in Japan: results from a nationwide study

OBJECTIVE

To investigate prognosis and prognostic factors in patients with hypertrophic cardiomyopathy (HCM) in Japan.

DESIGN

A nationwide epidemiological study.

SETTING

Hospitals selected randomly from among all hospitals in Japan.

PATIENTS

Clinical and epidemiological information for 2155 patients with HCM were collected in 1999.

MAIN OUTCOME MEASURES

Patients were classified on the basis of baseline prognostic factors. Survival rates up to 5 years were calculated by Cox's proportional hazard model for 1605 patients.

RESULTS

During the follow-up period, 241 deaths were recorded. The crude 5-year survival rate for the entire cohort was 86% (95% CI 84 to 88), and annual mortality ranged from 2.2% to 3.0%. A higher cardiothoracic ratio on chest x ray (HR 1.61; 95% CI 1.26 to 2.05, with 1 SD (6.2%) increase), a lower left ventricular ejection fraction (HR 1.42; 95% CI 1.20 to 1.69, with 1 SD (13%) decrease) and the presence of left bundle branch block (HR 3.14; 95% CI 1.28 to 7.71) were independently associated with a poorer prognosis, whereas the presence of apical hypertrophy at baseline (HR 0.58; 95%CI 0.36 to 0.92) predicted a better chance of survival.

CONCLUSIONS

The nationwide survey of patients with hypertrophic cardiomyopathy yielded important information on its prognosis and prognostic factors. These observations afford, for the first time, a measure of risk stratification in patients with HCM in Japan.

Primary Prophylaxis of Sudden Death in Hypertrophic Cardiomyopathy, Arrhythmogenic Right Ventricular Cardiomyopathy, and Dilated Cardiomyopathy

We present an evidence-based overview of primary prevention of sudden cardiac death. Several recent studies have provided important data regarding pharmacologic and device-based therapy for patients with conditions that confer high risk for sudden death. A rational approach to these therapies, with emphasis on implanted cardiovertor defibrillators, is discussed.

Prognostic value of heart rate variability in patients with hypertrophic cardiomyopathy

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

Risk of sudden cardiac death in young athletes: which screening strategies are appropriate?

Resources are not available to comprehensively evaluate all young athletes before participation in competitive sports. Therefore, the cardiovascular evaluation of young athletes needs to be targeted at high-risk areas and focus on the individuals who are at greatest possible risk: those who have suggestive, even if minor, symptoms, and those who have a family history of sudden death or premature cardiac disease.

Hypertrophic cardiomyopathy: state-of-the-art review, with focus on the management of outflow obstruction

Significant advances in our understanding and management of hypertrophic cardiomyopathy have been made in the last decade, as the complex genetics and phenotype-genotype correlations that characterize the disease are gradually unravelled. The well-described clinical heterogeneity of hypertrophic cardiomyopathy is now understood to be based on profound genetic variability, with at least 10 genes and over 150 mutations implicated. Several new therapeutic tools have entered clinical practice. The implantable cardioverter-defibrillator is now strongly indicated in those at high risk of sudden arrhythmic death. Our ability to abort sudden death in this subgroup has placed added emphasis on risk stratification in newly diagnosed patients. New procedures have also been developed for the relief of outflow obstruction in patients with refractory symptoms and a significant subaortic outflow gradient. Although not as efficacious as the 'gold-standard' surgical myectomy-myotomy, dual-chamber pacemaker implantation can be of modest benefit in select patients. Percutaneous transluminal septal myocardial ablation is an emerging catheter-based procedure for the relief of left ventricular outflow obstruction. Long-term follow-up data are still awaited. However, intermediate-term results suggest equivalent efficacy to surgical myectomy-myotomy.

Experimental study of relationship between intracoronary alcohol injection and the size of resultant myocardial infarct

BACKGROUND

Hypertrophic obstructive cardiomyopathy (HOCM) is a complex disease with unique pathophysiologic characteristics and a great diversity of morphologic,functional and clinical features. Percutaneous transluminal septal myocardial ablation (PTSMA) using alcohol injection via a catheter into the septal branch of the left anterior descending coronary artery has been recently introduced as a promising nonsurgical therapy for HOCM. However, the relationship between the volume and velocity of intracoronary injection of absolute alcohol and the size of the resultant myocardial infarct has not been investigated. We therefore studied such a relationship in piglets.

OBJECTIVES

To investigate the relationship between the volume and velocity of selective intracoronary alcohol injection by means of a catheter and the size of the resultant myocardial infarction.

METHODS

Twenty piglets were equally divided at random into four groups (n=5 in each) according to the volume and the velocity of intracoronary absolute alcohol injection and the coronary arteries injected. Group I: the volume and velocity of injection of alcohol into the left circumflex coronary artery (LCX) were 0.5 ml and 0.2 ml/s, respectively. Group II: the volume and velocity of injection into LCX were 2.0 ml and 0.2 ml/s, respectively. Group III: the volume and velocity of injection of alcohol into the left anterior descending coronary artery (LAD) were 1.2 ml and 0.06 ml/s, respectively. Group IV: the volume and velocity of injection into the LAD were 1.2 ml and 1.2 ml/s, respectively. The resultant myocardial infarcts were then quantitatively measured 6 h after myocardial ablation.

RESULTS

The myocardial infarct size for group I was 4.26+/-2.71(%), for group II was 10.12+/-4.55(%), for group III was 5.84+/-1.21(%) and for group IV was 7.11+/-1.63(%). There were significant differences in myocardial infarct size with different volumes of intracoronary absolute alcohol injection (0.02<P<0.05). but there were no apparent differences found in myocardial infarct size with different velocities of intracoronary alcohol injection (0.05<P<0.2).

CONCLUSIONS

The myocardial infarct size is directly related to the volume of intracoronary absolute alcohol injection during myocardial ablation by a catheter, but has no relation to the injection velocity.

Dynamic obstruction of the left ventricular outflow tract in four young dogs

Four young dogs presented for evaluation of left-sided systolic heart murmurs all showed echocardiographic changes consistent with dynamic left ventricular outflow tract (LVOT) obstruction and subjective evidence of concentric left ventricular hypertrophy. In three of the dogs, abnormal mitral valve apparatus and systolic anterior motion of the anterior mitral valve leaflet with associated mitral insufficiency were also detected. All dogs were medicated with a beta1-adrenergic antagonist. Subsequent examinations showed that the dynamic LVOT obstruction and left ventricular concentric hypertrophy had almost completely resolved. Dynamic LVOT obstruction is a rare condition of young dogs of different breeds. The precise aetiology of the condition remains uncertain. Whether resolution of the outflow obstruction in these four cases was a consequence of treatment or due to changes in ventricular architecture brought about by ageing cannot be established.

Oestrogen protects FKBP12.6 null mice from cardiac hypertrophy

FK506 binding proteins 12 and 12.6 (FKBP12 and FKBP12.6) are intracellular receptors for the immunosuppressant drug FK506 (ref. 1). The skeletal muscle ryanodine receptor (RyR1) is isolated as a hetero-oligomer with FKBP12 (ref. 2), whereas the cardiac ryanodine receptor (RyR2) more selectively associates with FKBP12.6 (refs 3, 4, 5). FKBP12 modulates Ca2+ release from the sarcoplasmic reticulum in skeletal muscle and developmental cardiac defects have been reported in FKBP12-deficient mice, but the role of FKBP12.6 in cardiac excitation-contraction coupling remains unclear. Here we show that disruption of the FKBP12.6 gene in mice results in cardiac hypertrophy in male mice, but not in females. Female hearts are normal, despite the fact that male and female knockout mice display similar dysregulation of Ca2+ release, seen as increases in the amplitude and duration of Ca2+ sparks and calcium-induced calcium release gain. Female FKBP12.6-null mice treated with tamoxifen, an oestrogen receptor antagonist, develop cardiac hypertrophy similar to that of male mice. We conclude that FKBP12.6 modulates cardiac excitation-contraction coupling and that oestrogen plays a protective role in the hypertrophic response of the heart to Ca2+ dysregulation.

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.

[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.

Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy is a genetic disease associated with a risk of ventricular tachyarrhythmias and sudden death, especially in young patients.

METHODS

We conducted a retrospective multicenter study of the efficacy of implantable cardioverter-defibrillators in preventing sudden death in 128 patients with hypertrophic cardiomyopathy who were judged to be at high risk for sudden death.

RESULTS

At the time of the implantation of the defibrillator, the patients were 8 to 82 years old (mean [+/-SD], 40+/-16), and 69 patients (54 percent) were less than 41 years old. The average follow-up period was 3.1 years. Defibrillators were activated appropriately in 29 patients (23 percent), by providing defibrillation shocks or antitachycardia pacing, with the restoration of sinus rhythm; the average age at the time of the intervention was 41 years. The rate of appropriate defibrillator discharge was 7 percent per year. A total of 32 patients (25 percent) had episodes of inappropriate discharges. In the group of 43 patients who received defibrillators for secondary prevention (after cardiac arrest or sustained ventricular tachycardia), the devices were activated appropriately in 19 patients (11 percent per year). Of 85 patients who had prophylactic implants because of risk factors (i.e., for primary prevention), 10 had appropriate interventions (5 percent per year). The interval between implantation and the first appropriate discharge was highly variable but was substantially prolonged (four to nine years) in six patients. In all 21 patients with stored electrographic data and appropriate interventions, the interventions were triggered by ventricular tachycardia or fibrillation.

CONCLUSIONS

Ventricular tachycardia or fibrillation appears to be the principal mechanism of sudden death in patients with hypertrophic cardiomyopathy. In high-risk patients with hypertrophic cardiomyopathy, implantable defibrillators are highly effective in terminating such arrhythmias, indicating that these devices have a role in the primary and secondary prevention of sudden death.

Dual chamber pacing for patients with hypertrophic obstructive cardiomyopathy: a clinical perspective in 2000

In some patients with hypertrophic cardiomyopathy, the dynamic left ventricular outflow tract obstructive gradient results in exercise-limiting symptoms of dyspnea, angina, and syncope. Dual chamber pacing has been proposed as a widely available alternative treatment for a subset of patients with symptomatic hypertrophic obstructive cardiomyopathy. Initial studies showed a reduction in gradient and an improvement in symptoms in almost 90% of patients with severe symptoms. We report the Mayo Clinic experience with dual chamber pacing in 38 patients with hypertrophic obstructive cardiomyopathy who had permanent pacemakers implanted for limiting symptoms intractable to medical therapy. After a mean +/- SD follow-up of 24 +/- 14 months, subjective improvement was reported in 47% of patients. However, there was no statistical difference between the maximal oxygen consumption at last follow-up and AAI pacing (atrial sensing and atrial pacing) (18.6 +/- 1.1 mL.kg-1.min-1) (i.e., when the pacemaker was implanted but not pacing continuously). This article discusses the clinical perspective on the utility of dual chamber pacing for patients with hypertrophic obstructive cardiomyopathy.

Malalignment of the sarcomeric filaments in hypertrophic cardiomyopathy with cardiac myosin heavy chain gene mutation

OBJECTIVE

To investigate changes in the alignment of the sarcomeric filaments in hypertrophic cardiomyopathy and the effects of cardiac beta myosin heavy chain (beta-MHC) mutation on the sarcomeric ultrastructure.

DESIGN

A retrospective analysis.

PATIENTS

Endomyocardial biopsy samples were examined by transmission electron microscopy in seven patients with hypertrophic cardiomyopathy and beta-MHC mutation, six with hypertrophic cardiomyopathy but without the mutation, and five controls (with chest pain syndromes).

MAIN OUTCOME MEASURE

Alignment of the sarcomeric filaments and the distance between neighbouring thick myosin filaments.

RESULTS

In controls, cross sections of the sarcomere at the A band showed a highly organised orthohexagonal array with 6 thin actin filaments surrounding one thick myosin filament, whereas in hypertrophic cardiomyopathy the alignment of the sarcomeric filaments was sparse and disrupted. In hypertrophic cardiomyopathy with a mutation, the distance between neighbouring thick myosin filaments was greater than in controls (mean (SD) 45.3 (4.7) v 38.5 (3.5) nm, p < 0.05), and the variance of the distance was greater than in controls (8.0 (0.7) v 4.8 (1.0) nm, p < 0.001) or in patients with hypertrophic cardiomyopathy without a mutation (6.7 (0.6) nm, p < 0.05). In the latter, the variance of the distance was also greater than in the controls (p < 0.01). A significant correlation was found between the grade of the myocyte hypertrophy and the variance of the distance (r = 0.654; p < 0.01).

CONCLUSIONS

The alignment of the sarcomeric filaments is disrupted in hypertrophic cardiomyopathy, particularly when there is beta-MHC mutation.

Hypertrophic Cardiomyopathy

The degree of clinical expression of both obstructive and nonobstructive hypertrophic cardiomyopathy (HCM) is widely variable. Many patients with HCM are asymptomatic or minimally symptomatic. Most patients with mild or moderate HCM respond well to medical therapy, but medical therapy in patients with severe disease is only marginally beneficial. In some instances, medical therapy can even complicate management by producing significant conduction disturbances. Most symptomatic patients with a significant resting outflow tract gradient may respond to atrioventricular sequential electronic pacing. Most of these patients eventually become symptomatic again, however, because of progression of the disease process or other unknown factors. The outcome of myotomy-myectomy depends greatly on the surgeon's experience with this surgical procedure. In patients with very severe hypertrophy or evidence of left ventricular dilatation and systolic dysfunction, cardiac transplantation should be considered earlier than it would be on the basis of symptoms, functional capacity, and other factors.

Fixed left ventricular outflow tract obstruction in presumed hypertrophic obstructive cardiomyopathy: implications for therapy

BACKGROUND

A subset of patients presenting with a presumed diagnosis of hypertrophic obstructive cardiomyopathy (HOCM) have a fixed left ventricular outflow tract (LVOT) obstruction. Recognition of this pathophysiologic abnormality is important in choosing therapy.

METHODS

Of patients referred for treatment of HOCM, 4 had fixed LVOT obstruction. Clinical and echocardiographic data and surgical findings were reviewed.

RESULTS

In the 4 patients with clinical features consistent with HOCM or HOCM-like conditions, echocardiography showed fixed LVOT obstruction with an early-peaking LVOT Doppler signal or absence of severe systolic anterior motion of the mitral valve. The causes of fixed obstruction included accessory mitral tissue with associated fibrous ring (1 patient), fixed subaortic tunnel stenosis (2 patients), and a discreet subaortic ridge (1 patient). After surgical relief of the fixed LVOT obstruction, all patients had relief of the ventricular outflow tract gradient.

CONCLUSIONS

Not all patients with a presumed diagnosis of HOCM have isolated dynamic LVOT obstruction but may have isolated or additional fixed obstruction. Careful two-dimensional and Doppler echocardiography are needed to identify this subset of patients who are best treated surgically.

Prognostic value of systemic blood pressure response during exercise in a community-based patient population with hypertrophic cardiomyopathy

OBJECTIVES

The present study was designed to prospectively evaluate the prognostic relevance of abnormal blood pressure response to exercise (ABPR), defined as hypotension or failed blood pressure increase (<20 mm Hg) with exercise, in a community-based hypertrophic cardiomyopathy (HCM) population representative of the overall disease spectrum.

BACKGROUND

Abnormal blood pressure response to exercise has been proposed as a marker for hemodynamic instability and increased risk for disease-related mortality in highly selected patient populations with HCM.

METHODS

The study population comprised 126 patients (aged 42+/-14 years) who underwent maximal symptom-limited cycloergometer exercise testing as part of the standard evaluation at our institution, and who were followed systematically for 4.7+/-3.7 years after testing.

RESULTS

Of the 126 study patients, 98 (78%) had a normal blood pressure response during exercise, whereas the other 28 (22%) had ABPR, including nine with hypotension and 19 with failed blood pressure rise. During the follow-up period, nine patients (7%) died of HCM-related causes (three suddenly and six heart failure-related), of whom four had ABPR. In those patients aged < or =50 years, survival analysis after exercise testing showed a significantly increased risk for cardiovascular mortality associated with ABPR compared with a normal exercise response (p = 0.04), with an odds ratio of 4.5 (95% confidence interval: 1.1, 20.1). However, ABPR showed low positive predictive accuracy for cardiovascular mortality (i.e., 14%), whereas negative predictive accuracy was high (i.e., 95%).

CONCLUSIONS

A hypotensive blood pressure response during exercise occurred in over 20% of a community-based patient cohort with HCM, and was associated with adverse long-term prognosis in patients <50 years old. However, the positive predictive accuracy of this blood pressure response is too low to justify modifications of clinical management or to allow identification of the high-risk patient based solely on an abnormal test result. By virtue of its high negative predictive accuracy for HCM-related mortality, the blood pressure response to exercise appears to be most valuable (in conjunction with the absence of other well recognized risk factors) as a screening test for the identification of low-risk subsets of patients.

[Appraisal of the state of the autonomic nervous system in hypertrophic cardiomyopathy by the analysis of heart rate variability]

INTRODUCTION

The analysis of heart rate variability has been accepted as a non-invasive method to evaluate the influence of the autonomic nervous system over the heart. Although heart rate variability has been used during the last decade in several illnesses the studies in hypertrophic cardiomyopathy are scarce.

OBJECTIVES

We report the activity of the autonomic nervous system in patients with hypertrophic cardiomyopathy using the analysis of heart rate variability.

PATIENTS AND METHODS

Heart rate variability was evaluate by the analyzing 24-h ambulatory electrocardiograms (Holter) in 20 patients with hypertrophic cardiomyopathy and in 15 controls. This method has been used to measure heart rate variability. Spectral analysis of the frequencies were calculated using fast Fourier transformation. Spectral heart rate variability was computed as high (0.15 to 0.40 Hz) low (0.04 to 0.15 Hz) and total (0.01 to 1.0 Hz). We compared the relation between low/high frequency as an index of the sympathetic/parasympathetic balance. All data are expressed as mean value +/- SD. The unpaired Student t-test was used. A two tailed p valued < 0.05 was considered statistically significant.

RESULTS

There were no differences in the mean heart rates among the patients with hypertrophic cardiomyopathy and normal subjects (mean +/- SD: 71 +/- 9 versus 74 +/- 11 beats/minute; p = NS) while there was a significant decline in total spectral (mean +/- SD: 7.14 +/- 1.1 versus 7.57 +/- 0.6 ln [ms2]; p = 0.02) and high (mean +/- SD: 5.22 +/- 0.8 versus 5.63 +/- 1.3 ln [ms2]; p = 0.04) as well as in low spectral frequency of heart rate variability (mean +/- SD: 22 +/- 0.8 versus 5.63 +/- 1.3 ln [ms2]; p = 0.04) in patients with hypertrophic cardiomyopathy. There were no differences in the low/high frequency component ratio in these patients (mean +/- SD: 1.1 +/- 0.1 versus 1.2 +/- 0.1 ln [ms2]; p = NS).

CONCLUSIONS

These facts suggest that the patients with hypertrophic cardiomyopathy have an alteration in the autonomic nervous system: sympathetic (low spectral frequencies) and parasympathetic activity (high spectral frequencies), although this does not reflect an imbalance between sympathetic and parasympathetic activities (relation of low to high spectral frequencies).

The importance of atrial contribution: a case study of dual-chamber pacing in hypertrophic obstructive cardiomyopathy

Beta blockers and calcium channel blockers are the mainstay of therapy for hypertrophic obstructive cardiomyopathy. Recent evidence suggests that dual-chamber pacing may also relieve symptoms in a subset of patients. Proper interval programming is critical to the success of this intervention-as well as maintenance of the atrial contribution to preserve left ventricular diastolic filling. This report illustrates the importance of atrial contribution, as well as the loss of atrial capture, which can lead to hemodynamic deterioration and recurrence of symptoms.

Risk profiles and cardiovascular preparticipation screening of competitive athletes

There has been heightened interest in the design and role of preparticipation screening for high school and college athletes. An American Heart Association consensus panel, composed of cardiovascular specialists and other physician experts having extensive clinical experience with athletes of all ages as well as a legal expert, assessed the benefits and limitations of preparticipation screening for early detection of cardiovascular abnormalities in competitive athletes. The panel addressed cost-efficiency and feasibility issues as well as the medicolegal implications of screening; and developed consensus recommendations and guidelines for the most prudent, practical, and effective screening procedures and strategies.

Effect of regional myocardial perfusion abnormalities on regional myocardial early diastolic function in patients with hypertrophic cardiomyopathy

Nonuniform hypertrophy of the left ventricle is an important factor in regional diastolic dysfunction in patients with hypertrophic cardiomyopathy (HCM). However, the effect of myocardial perfusion abnormalities on regional diastolic dysfunction has not been established in patients with HCM. We investigated the relationship between regional myocardial perfusion abnormalities and regional early diastolic function in 31 patients with HCM and 8 control patients. Short-axis images of the left ventricle recorded by cine magnetic resonance imaging were divided into ten blocks. The time-to-peak-wall-thickness-thinning rate (TPWR) and the wall thickness were measured in each block. Of the 310 blocks from the patients with HCM, 242 (78%) showed normal thallium-201 uptake (group 1), 40 (13%) showed slightly decreased uptake (group 2), and 28 (9%) showed markedly decreased uptake (group 3). There was no difference in the regional wall thickness among the three groups. The TPWR was longer in patients with HCM than in control patients. It was significantly longer in group 3 (190+/-45ms) than in group 1 (167+/-36 ms) and group 2 (160+/-31 ms). (P < 0.01). The linear regression slope of the relationship between the TPWR and the regional wall thickness was significantly steeper in group 3 than in groups 1 and 2 (P < 0.05). In conclusion, abnormalities in regional myocardial perfusion, in addition to regional hypertrophy, contributed to the regional early diastolic dysfunction in patients with HCM.

Dual-chamber pacing for cardiomyopathies: a 1996 clinical perspective

Implantation of a permanent pacemaker is an accepted mode of therapy for symptomatic bradyarrhythmias. Application of pacemaker technology for the treatment of cardiomyopathies has generated considerable interest and enthusiastic support in recent years. In both hypertrophic cardiomyopathy and dilated cardiomyopathy, dual-chamber pacing has been shown to decrease symptoms and improve hemodynamics; however, not all patients will benefit from dual-chamber pacing. Technical considerations must be acknowledged in order to obtain optimal benefit with dual-chamber pacing. In addition, other more accepted therapies are available for patients with symptomatic cardiomyopathies. The purposes of this article are to review critically the current literature on the use of dual-chamber pacemakers in patients with either hypertrophic or dilated cardiomyopathy and to provide a clinical perspective based on current knowledge.

Periodontal implications: medically compromised patients

The presence of systemic disease in patients requiring periodontal therapy creates challenges for management. Alteration of treatment plans, with emphasis on physician consultation and preventive periodontal care, is frequently needed to minimize the impact of periodontal disease on the systemic condition. Conversely, detection and treatment of systemic disorders may impact upon the status of the periodontium and the success of periodontal therapy. The goal of holistic patient management is facilitated by a free flow of information between the patients and their medical and dental health care providers.

Clinical approach to genetic cardiomyopathy in children

BACKGROUND

Cardiomyopathy (CM) remains one of the leading cardiac causes of death in children, although in the majority of cases, the cause is unknown. To have an impact on morbidity and mortality, attention must shift to etiology-specific treatments. The diagnostic evaluation of children with CM of genetic origin is complicated by the large number of rare genetic causes, the broad range of clinical presentations, and the array of specialized diagnostic tests and biochemical assays.

METHODS AND RESULTS

We present a multidisciplinary diagnostic approach to pediatric CM of genetic etiology. We specify criteria for abnormal left ventricular systolic performance and structure that suggest CM based on established normal echocardiographic measurements and list other indications to consider an evaluation for CM. We provide a differential diagnosis of genetic conditions associated with CM, classified as inborn errors of metabolism, malformation syndromes, neuromuscular diseases, and familial isolated CM disorders. A diagnostic strategy is offered that is based on the clinical presentation: biochemical abnormalities, encephalopathy, dysmorphic features or multiple malformations, neuromuscular disease, apparently isolated CM, and pathological specimen findings. Adjunctive treatment measures are recommended for severely ill patients in whom a metabolic cause of CM is suspected. A protocol is provided for the evaluation of moribund patients.

CONCLUSIONS

In summary, we hope to assist pediatric cardiologists and other subspecialists in the evaluation of children with CM for a possible genetic cause using a presentation-based approach. This should increase the percentage of children with CM for whom a diagnosis can be established, with important implications for treatment, prognosis, and genetic counseling.

Case report: lysosomal glycogen storage disease with normal acid maltase: an unusual form of hypertrophic cardiomyopathy with rapidly progressive heart failure

A 14-year-old boy with mild mental retardation, myopathy, and nonobstructive hypertrophic cardiomyopathy (HCM) with clinical and histopathologic features consistent with lysosomal glycogen storage disease with normal acid maltase is described. The case illustrates the aggressive nature of the cardiomyopathy of this syndrome. This condition is associated with malignant ventricular arrhythmias, relentlessly progressive ventricular dilatation, dysfunction, and sudden death. It is important to recognize this unusual and malignant form of HCM to precipitate low early diagnosis by muscle biopsy. Patients with this condition would be excellent candidates for life-saving heart transplant as the myopathy and mental retardation are mild and nonprogressive. The underlying biochemical defect and mode of inheritance of this syndrome are unclear. However, a significant proportion are genetically related and thus, relatives may benefit from family screening.

Resting echocardiographic features of latent left ventricular outflow obstruction in hypertrophic cardiomyopathy

We determined resting echocardiographic features predictive of latent left ventricular (LV) outflow obstruction in 50 consecutive patients with nonobstructive hypertrophic cardiomyopathy (26 provocable, 24 nonprovocable with amyl nitrite inhalation) to have a better understanding of the pathophysiology of this condition and to identify such patients without pharmacologic provocation. Measurements included wall thickness, type of hypertrophy, LV outflow tract diameter, degree of mitral systolic anterior motion, outflow pressure gradient, and ventricular volume. The direction of the ejection streamline was measured to assess the magnitude of the drag force acting on the mitral valve. Thirteen of 16 patients (81%) with proximal septal bulge were provocable, whereas only 3 of 8 patients (38%) with asymmetric septal hypertrophy and 10 of 26 (38%) with concentric hypertrophy were provocable (p < 0.05). LV outflow tract was significantly narrower and the angle between the ejection flow and the mitral valve was larger in provocable patients. The sensitivity for predicting provocable patients by a combination of a narrow outflow tract (< or = 2 cm) and a large angle (> or = 35 degrees) was 65%, with a specificity of 80% and a positive predictive value of 79%. When these criteria were combined with the presence of septal bulge, the sensitivity was 35%, but the specificity and the positive predictive value were both 100%. Patients with nonobstructive hypertrophic cardiomyopathy with proximal septal bulge, a narrow LV outflow tract, and an oblique angle between the ejection flow and the mitral valve appeared to be predisposed for latent outflow obstruction. These features are consistent with the presence of the large Venturi and drag forces. Thus, the left ventricle, which is capable of increasing both the Venturi and the drog forces on the basis of the morphologic change, contributes to the development of outflow obstruction with amyl nitrite inhalation.