ABSTRACT
BACKGROUND: Diminished functional capacity is common in hypertrophic cardiomyopathy (HCM), although the underlying mechanisms are complicated. We studied the prevalence of chronotropic incompetence and its relation to exercise intolerance in patients with HCM. METHODS: Cardiopulmonary exercise testing was performed in 68 patients with HCM (age 44.8 ± 14.6 years, 45 males). Chronotropic incompetence was defined by chronotropic index (heart rate reserve)/(220-age-resting heart rate) and exercise capacity was assessed by peak oxygen consumption (peak Vo(2)). RESULTS: Chronotropic incompetence was present in 50% of the patients and was associated with higher NYHA class, history of atrial fibrillation, higher fibrosis burden on cardiac MRI, and treatment with ß-blockers, amiodarone and warfarin. On univariate analysis, male gender, age, NYHA class, maximal wall thickness, left atrial diameter, peak early diastolic myocardial velocity of the lateral mitral annulus, history of atrial fibrillation, presence of left ventricular outflow tract obstruction (LVOTO) at rest, and treatment with beta-blockers were related to peak Vo(2). Peak heart rate during exercise, heart rate reserve, chronotropic index, and peak systolic blood pressure were also related to peak Vo(2). On multivariate analysis male gender, atrial fibrillation, presence of LVOTO and heart rate reserve were independent predictors of exercise capacity (R(2) = 76.7%). A cutoff of 62 bpm for the heart rate reserve showed a negative predictive value of 100% in predicting patients with a peak Vo(2) <80%. CONCLUSIONS: Blunted heart rate response to exercise is common in HCM and represents an important determinant of exercise capacity.
Subject(s)
Cardiomyopathy, Hypertrophic/diagnosis , Cardiomyopathy, Hypertrophic/physiopathology , Exercise Test/methods , Exercise Tolerance/physiology , Heart Rate/physiology , Adult , Female , Humans , Male , Middle Aged , Prospective StudiesABSTRACT
The purpose of the present study was to evaluate the prevalence and prognosis of patients incidentally diagnosed with hypertrophic cardiomyopathy (HC). We studied 380 consecutive patients with HC (49.3 +/- 17.2 years; 65% men) for a median of 58 months (range 6 to 454). The patients were divided into 2 groups: those incidentally diagnosed from routine examination findings (precordial murmur and/or abnormal electrocardiographic findings) and those diagnosed either because of symptomatic status or by screening because of a family history of HC. Those patients who had been incidentally diagnosed constituted 29.2% of our study cohort. Although overall mortality did not differ between the 2 groups (p = 0.12), the patients diagnosed either because of symptoms or a family history tended to have at least a 4.5-fold greater risk of cardiovascular death (relative risk 4.5, 95% confidence interval 1.04 to 19.6, p = 0.04) and a 4.22 greater risk of sudden death (relative risk 4.22, 95% confidence interval 1.0 to 18.22, p = 0.04). Despite the greater sudden death mortality among the nonincidentally diagnosed patients, no statistically significant difference was found concerning the sudden death risk factor frequency (p = 0.96) between the 2 groups. In conclusion, the discrepancy between the low numbers of patients reported by published registries and the relatively high prevalence of the disease in the general population can be attributed to the large number of patients who remain asymptomatic, even throughout their life, awaiting an accidental diagnosis. Those patients with an incidental diagnosis have a more benign course, as shown by the total cardiovascular and composite sudden death mortality. A high level of awareness and suspicion for HC among physicians is essential for clinical recognition of such patients.
Subject(s)
Cardiomyopathy, Hypertrophic/diagnosis , Cardiomyopathy, Hypertrophic/epidemiology , Death, Sudden/epidemiology , Incidental Findings , Adult , Age Distribution , Cardiomyopathy, Hypertrophic/therapy , Cause of Death , Chi-Square Distribution , Cohort Studies , Echocardiography, Doppler, Color , Echocardiography, Doppler, Pulsed , Electrocardiography , Exercise Test , Female , Humans , Kaplan-Meier Estimate , Male , Middle Aged , Physical Examination/methods , Prevalence , Prognosis , Proportional Hazards Models , Retrospective Studies , Severity of Illness Index , Sex Distribution , Statistics, Nonparametric , Survival AnalysisABSTRACT
Hypertrophic cardiomyopathy (HC) may transition to a phase characterized by systolic impairment resembling dilated cardiomyopathy. This study retrospectively assessed the incidence of left ventricular (LV) systolic impairment at initial clinical evaluation in 248 consecutive patients with HC (mean age 53 +/- 16 years). HC with systolic impairment was diagnosed if the LV ejection fraction was <50%, calculated by echocardiography. Twenty patients (8%) had HC with LV systolic impairment at initial evaluation. Patients with systolic impairment had a greater incidence of family histories of sudden cardiac death (SCD) than patients with preserved systolic function (25% vs 5.3%, p = 0.006) and more severe functional limitations (New York Heart Association class >or=III, p <0.001). All-cause mortality and cardiovascular mortality did not differ between the 2 groups. The incidence of SCD was 1.7% in patients with normal LV ejection fractions, and no SCD was observed in patients with systolic impairment. The latter group had more frequent major cardiac events (SCD, ventricular fibrillation, aborted cardiac arrest, and first implantable cardioverter-defibrillator discharge; p = 0.03). During follow-up, 2 patients progressed to HC with systolic impairment (annual incidence 0.85%). In conclusion, systolic impairment is not exceptional in patients with HC at initial evaluation and is associated with functional deterioration and major cardiac events.
