Infective endocarditis in hypertrophic cardiomyopathy - Prevalence, incidence, and indications for antibiotic prophylaxis

Background-The literature on infective endocarditis in hypertrophic cardiom yopathy (HCM) is virtually confined to case reports. Consequently, the risk of endocarditis in HCM remains undefined. Methods and Results-We assessed the occurrence, of endocarditis in 810 HCM patients evaluated between 1970 and 1997. Endocarditis. was diagnosed in 10 patients, 2 of whom were excluded from analysis of prevalence and incidenc e because they were referred for acute endocarditis. At first evaluation, e chocardiographic features consistent with prior endocarditis were identifie d in 3 of 808 patients, a prevalence of 3.7 per 1000 patients (95% CI, 0.8 to 11), Of 681 patients who were followed, 5 developed endocarditis, an inc idence of 1.4 per 1000 person-years (95% CI, 0.5 to 3.2); outflow obstructi on was present in each of these 5 patients and was associated with: the ris k of endocarditis (P = 0.006). in the 224 obstructive patients, incidence o f endocarditis was 3.8 per 1000 person-years (95% CI, 1.6 to 8.9) and proba bility of endocarditis 4.3% at 10 years. Left atrial size was also associat ed with the risk of endocarditis (P=0.007). In patients with both obstructi on and atrial dilatation(greater than or equal to 50 mm), incidence of endo carditis increased to 9.2 per 1000 person-years (95% CI,2.5 to 23.5). Analy sis of all 10 patients with endocarditis identified outflow obstruction in each and atrial dilatation in 7. Conclusions-Endocarditis in HCM is virtually confined to patients with outf low obstruction and is more common in those with both obstruction and atria l dilatation, These results indicate that antibiotic prophylaxis is require d only in patients with obstructive HCM.