Proposal for contemporary screening strategies in families with hypertrophic cardiomyopathy

Screening families with hypertrophic cardiomyopathy (HCM) presents a common clinical problem to practicing cardiologists, internists, and pediatricians. The traditional recommended strategy for screening relatives in most HCM families calls for such evaluations with echocardiography (and electrocardiogram [ECG]) on a 12- to 18-month basis, usually beginning at about age 12 years. If such tests show no evidence of left ventricular hypertrophy, i.e., without one or more segments of abnormally increased wall thickness by the time full growth and maturation is achieved (at the age of about 18 to 21 years), it has been customary practice to conclude that HCM is probably absent and reassure family members accordingly that further echocardiographic testing is unnecessary. However, novel developments in the definition of the genetic causes of HCM have defined both substantial molecular diversity and heterogeneity of the disease expression including (in some relatives) incomplete phenotypic penetrance and delayed, late-onset left ventricular hypertrophy well into adulthood. These observations have unavoidably reshaped the customary practice of genetic counseling and established a new proposed paradigm for clinical family screening of HCM families. Therefore, in the absence of genetic testing, strong consideration should be given to extending diagnostic serial echocardiography past adolescence and into mid-life for those family members with a normal echocardiogram and ECG. Of note, recent developments in laboratory DNA-based diagnosis for HCM could potentially avoid the necessity for serial echocardiography in many such relatives.

Hypertrophic cardiomyopathy in childhood

Hypertrophic cardiomyopathy (HCM) is a heterogeneous and relatively common genetic cardiac disease that has been the subject of intense scrutiny and investigation for over 40 years. HCM is an important cause of disability and death in patients of all ages, although unexpected sudden death in the young is perhaps the most devastating component of the natural history. Therefore, while HCM is uncommon in pediatric cardiology practice, it is nevertheless a disease of great importance to young people and those clinicians charged with their care. Due to marked heterogeneity in clinical expression, natural history and prognosis, diagnostic and management strategies often represent a dilemma (and even the source of controversy) to both primary care clinicians and cardiovascular specialists. Consequently, it is timely to place perspective and clarify many of these relevant clinical issues, and profile the rapidly evolving concepts regarding HCM, especially as they may impact on this disease in childhood.

Impact of physical deconditioning on ventricular tachyarrhythmias in trained athletes

OBJECTIVES

The purpose of this research was to evaluate the impact of athletic training and, in particular, physical deconditioning, on frequent and/or complex ventricular tachyarrhythmias assessed by 24-h ambulatory (Holter) electrocardiogram (ECG).

BACKGROUND

Sudden deaths in athletes are usually mediated by ventricular tachyarrhythmias.

METHODS

Twenty-four hour ambulatory ECGs were recorded at peak training and after a deconditioning period of 19 +/- 6 weeks (range, 12 to 24 weeks) in a population of 70 trained athletes selected on the basis of frequent and/or complex ventricular tachyarrhythmias (i.e., > or =2,000 premature ventricular depolarization [PVD] and/or > or =1 burst of non-sustained ventricular tachycardia [NSVT]/24 h).

RESULTS

A significant decrease in the frequency and complexity of ventricular arrhythmias was evident after deconditioning: PVDs/24 h: 10,611 +/- 10,078 to 2,165 +/- 4,877 (80% reduction; p < 0.001) and NSVT/24 h: 6 +/- 22 to 0.5 +/- 2, (90% reduction; p = 0.04). In 50 of the 70 athletes (71%), ventricular arrhythmias decreased substantially after detraining (to <500 PVDs/24 h and no NSVT). Most of these athletes with reduced arrhythmias did not have structural cardiovascular abnormalities (37 of 50; 74%). Over the 8 +/- 4-year follow-up period, each of the 70 athletes survived without cardiac symptoms.

CONCLUSIONS

Frequent and/or complex ventricular tachyarrhythmias in trained athletes (with and without cardiovascular abnormalities) are sensitive to brief periods of deconditioning. In athletes with heart disease, the resolution of such arrhythmias with detraining may represent a mechanism by which risk for sudden death is reduced. Conversely, in athletes without cardiovascular abnormalities, reduction in frequency of ventricular tachyarrhythmias and the absence of cardiac events in the follow-up support the benign clinical nature of these rhythm disturbances as another expression of athlete's heart.

Prevalence of hypertrophic cardiomyopathy in a population-based sample of American Indians aged 51 to 77 years (the Strong Heart Study)

Recognition of the frequency with which hypertrophic cardiomyopathy (HC) occurs in the general population is critical to understanding its demographics and public health implications. However, few data are available for estimating HC prevalence in large populations of different age strata and ethnic or racial groups. The Strong Heart Study is a prospective, population-based epidemiologic survey of cardiovascular disease in residents of 13 geographically diverse American Indian communities. The study population was comprised of 3,501 subjects with echocardiograms performed in 1993 and 1995 to determine the prevalence of HC in middle-aged and older adult populations. Evidence of the HC phenotype was present in 8 previously undiagnosed patients (0.23%; 2 of 1,000) based on a left ventricular (LV) wall thickness >/=15 mm and a nondilated cavity that was not associated with another cardiac disease and was sufficient to produce the magnitude of hypertrophy evident. Ages were 51 to 77 years (mean 64 +/- 9). Four subjects were men and 4 were women, with prevalences by gender of 0.3% (3 of 1,000) and 0.18% (1.8 of 1,000), respectively. Maximum LV thicknesses were 19 to 29 mm (mean 21 +/- 3). Two subjects had mitral valve systolic anterior motion, which was sufficient to produce LV outflow obstruction at rest in 1 patient. Different electrocardiographic abnormalities were present in 5 subjects. In conclusion, clinically unrecognized HC was present in 1:500 of an aging American Indian cohort. This prevalence was similar to that reported in other general populations comprised of younger subjects of other races, offering evidence that HC is a relatively common genetic disease with widespread occurrence within the United States.

Arrhythmogenic Right Ventricular Cardiomyopathy Causing Sudden Cardiac Death in Boxer Dogs

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a primary familial heart muscle disease associated with substantial cardiovascular morbidity and risk of sudden death. Efforts to discern relevant pathophysiological mechanisms have been impaired by lack of a suitable animal model.

METHODS AND RESULTS

ARVC was diagnosed in 23 boxer dogs (12 male; 9.1+/-2.3 years old). Clinical events alone or in combination included sudden death (n=9; 39%), ventricular arrhythmias of suspected right ventricular (RV) origin (n=19; 83%), syncope (n=12, 52%), and heart failure (n=3; 13%). Right ventricular enlargement or aneurysms occurred in 10 (43%). Striking histopathological abnormalities were present in each boxer dog but not in controls, including severe RV myocyte loss with replacement by fatty (n=15, 65%) or fibrofatty (n=8, 35%) tissue. Focal fibrofatty lesions were also present in both atria (n=8) and the left ventricle (LV) (n=11). Fatty replacement occupied substantially greater RV wall area in ARVC dogs than controls (40.4+/-18.8% versus 13.8+/-3.4%, respectively) (P<0.001); residual myocardium was correspondingly reduced (56.6+/-19.2% versus 84.8+/-3.8% in controls) (P<0.001). MRI demonstrated bright anterolateral and/or infundibular RV myocardial signals, confirmed as fat by histopathology. Myocarditis appeared in the RV (n=14, 61%) and LV (n=16, 70%) and in each dog with sudden death, but not in controls. Familial transmission was evident in 10 of the 23.

CONCLUSIONS

We describe a novel, spontaneous, and genetically transmitted animal model of ARVC associated with sudden death in the boxer dog, closely resembling the human disease. This model may aid in understanding the pathogenic mechanisms of ARVC.

Usefulness of B-Type Natriuretic Peptide Assay in the Assessment of Symptomatic State in Hypertrophic Cardiomyopathy

Background— Hypertrophic cardiomyopathy (HCM) has a diverse clinical spectrum that often includes progressive heart failure symptoms and disability. Assessment of symptom severity may be highly subjective, encumbered by the heterogeneous clinical presentation. Plasma B-type natriuretic peptide (BNP) has been used widely as an objective marker for heart failure severity and outcome, predominantly in coronary heart disease with ventricular dilatation and systolic dysfunction.

Methods and Results— We prospectively assessed plasma BNP as a quantitative clinical marker of heart failure severity in 107 consecutive HCM patients. BNP showed a statistically significant relationship to magnitude of functional limitation, assessed by New York Heart Association (NYHA) functional class: I, 136±159 pg/mL; II, 338±439 pg/mL; and III/IV, 481±334 pg/mL ( P <0.001). Multivariable analysis showed that BNP was independently related to NYHA class as well as age and left ventricular wall thickness (each with a value of P =0.0001). BNP ≥200 pg/mL was the most reliable predictor of heart failure symptoms, with positive and negative predictive values of 63% and 79%, respectively. BNP power in distinguishing patients with or without heart failure symptoms was less than that for differentiating between no (or only mild) and severe symptoms (area under receiver operating characteristic curve=0.75 and 0.83, respectively).

Conclusions— Plasma BNP is independently related to the presence and magnitude of heart failure symptoms in patients with HCM. As a clinical marker for heart failure, BNP is limited by considerable overlap in values between categories of heart failure severity as well as confounding variables of left ventricular wall thickness and age.

Electrocardiographic changes associated with training and discontinuation of training in an athlete with hypertrophic cardiomyopathy

The 12-lead electrocardiogram of a 17-year-old African professional soccer player had signs of left ventricular (LV) hypertrophy and deeply inverted T waves in the inferior and precordial leads. Two-dimensional echocardiography showed mild LV hypertrophy with normal cavity size consistent with nonobstructive hypertrophic cardiomyopathy. After 5 months of complete discontinuation of training, the electrocardiogram normalized; however, the echocardiogram was unchanged. Subsequently, and contrary to our advice, the athlete resumed training and professional soccer. One year later the electrocardiogram again showed a similar and markedly abnormal pattern without cardiac dimensional changes.

Extended septal myectomy for hypertrophic obstructive cardiomyopathy with anomalous mitral papillary muscles or chordae

OBJECTIVES

Transaortic left ventricular septal myectomy yields excellent results for most severely symptomatic patients with hypertrophic obstructive cardiomyopathy. However, associated anomalies of the mitral subvalvular apparatus may prevent complete relief of obstruction, and mitral valve replacement has been advocated. We reviewed our results of procedures designed to relieve obstruction with preservation of the mitral valve.

METHODS

Among 291 patients undergoing septal myectomy from 1975 to 2002, 56 (ages 2-77 years) had anomalous mitral subvalvular apparatus including anomalous chordae (n = 28) and papillary muscles with direct insertion into mitral leaflets (n = 13) or fusion to septum (n = 31) or free wall (n = 12); 82% of patients were in New York Heart Association class III or IV. Operation included resection of anomalous chordae (28 patients), relief of papillary muscle fusion (36 patients), and extended septal myectomy, wider at the apex than the base.

RESULTS

There were no early deaths and no patients required mitral valve replacement. Mean peak pressure gradients decreased from 70 +/- 28 to 4.9 +/- 8.4 mm Hg and mean mitral regurgitation grade decreased from 2.3 to 1.0 (P <.001). Mean follow-up was 2.8 +/- 2.6 years. Freedom from reoperation at 4 years was 95%. There were 3 late noncardiac deaths; 98% of patients were in New York Heart Association class I or II.

CONCLUSIONS

Hypertrophic obstructive cardiomyopathy associated with anomalous mitral papillary muscles or chordae can be successfully treated without mitral valve replacement by surgical relief of the anomalies and an extended septal myectomy; early mortality is low, obstruction and mitral regurgitation are significantly reduced, and late results are excellent.

From malignant mutations to malignant domains: the continuing search for prognostic significance in the mutant genes causing hypertrophic cardiomyopathy

The genetic causes of hypertrophic cardiomyopathy are diverse and thus present challenges in the development of genetic tests to identify patients at risk

Comparison of prevalence of apical hypertrophic cardiomyopathy in Japan and the United States

The morphologic apical form of hypertrophic cardiomyopathy (HC), in which left ventricular (LV) wall thickening is confined to the most distal region at the apex, has been regarded as a phenotypic expression of nonobstructive HC largely unique to Japanese patients. To investigate this question further, we directly compared unselected and regional hospital-based cohorts of adult patients with HC ( > or =18 years of age) from Japan (Kochi; n=100) and from the United States (US) (Minneapolis; n=361). Japanese and American patients with HC had similar clinical features and did not differ significantly with regard to the severity of symptoms and frequency of outflow obstruction. Although Japanese and American patients also showed similar maximum LV thickness, they differed significantly with respect to the distribution of LV hypertrophy. In particular, the segmental form of HC, with hypertrophy confined to the LV apex, was more frequent in Japanese patients (i.e., apical HC, 15% in Japan vs 3% in US, p<0.0001). Giant negative T waves were also more common in Japanese patients with HC (26% vs 2%, p<0.001), including those with the apical form (64% vs. 30%, p<0.05). Each patient with apical HC had either no or only mild symptoms, and all survived. The morphologic form of nonobstructive HC with hypertrophy limited to the LV apex (apical form of HC) was 5 times more common in an unselected Japanese population. These findings document variability in the phenotypic expression of HC between countries and races, which may be due to differences in environmental factors or genetic background. Patients with the apical form of HC had a benign clinical course.

Clinical course of hypertrophic cardiomyopathy with survival to advanced age

OBJECTIVES

This study was designed to clarify and resolve the clinical profile of older patients with hypertrophic cardiomyopathy (HCM).

BACKGROUND

Adverse consequences of HCM such as sudden death and incapacitating symptoms have been emphasized for the young and middle-aged.

METHODS

Long-term outcome of HCM was assessed in a community-based cohort not subject to tertiary center referral bias.

RESULTS

Of 312 patients, 73 (23%) achieved normal life expectancy (> or =75 years; range to 96); 44 (14%) were > or =80 years old. Most patients > or =75 years (47; 64%) experienced no or only mild limiting symptoms and lived virtually their entire lives with few HCM-related clinical consequences; 26 patients (36%) experienced severe progressive symptoms. In elderly patients with HCM, diagnosis and symptom onset were considerably delayed to 74 +/- 8 and 70 +/- 11 years, respectively. For patients > or =50 years at diagnosis, the probability of survival for 5, 10, and 15 years was 85 +/- 3%, 74 +/- 4%, and 57 +/- 6%, respectively, and did not significantly differ from a matched general population (p = 0.20). Patients > or =75 years were predominantly women, and had less marked wall thickness and more frequently showed basal outflow obstruction > or =30 mm Hg (compared with those <75 years; p < 0.01 and 0.001, respectively).

CONCLUSIONS

Hypertrophic cardiomyopathy is frequently well tolerated and compatible with normal life expectancy, and may remain clinically dormant for long periods of time with symptoms and initial diagnosis deferred until late in life. These observations afford a measure of reassurance to many patients with HCM, a disease for which clinical course is often unfavorable and unpredictable.