Apical Hypertrophic Cardiomyopathy Preserved Ejection Fraction Whose Symptom Improved by Treating with Low Doses of Pimobendan

A 74 year old man had received a follow up examination from us in regard to symptom of exertional dyspnea, high level of brain type natriuretic peptide(BNP), cardiac diastolic dysfunction. Electrocardiogram(ECG) showed giant negative T waves, but transthoracic echocardiography revealed left ventricular wall motion was normal and no obvious valvular disease existed. Pharmacotherapy with oral administration of cibenzoline and bisoprolol was initiated because ECG also showed premature atrial contraction(PAC), but it could not improve symptom and reduce BNP level. When his symptom worsened, we performed coronary angiography(CAG) and left ventriculography(LVG). LVG revealed apical hypertrophic cardiomyopathy, and coronary was intact. We started to treat with low doses of pimobendan in expectation of improve diastolic dysfunction, thefore his symptom and high level of BNP improved. Pimobendan is a calcium sensitizer and a PDE3 inhibitor. It has been termed an inodilator because of its dual action of positive inotropy and vasodilation. Pimobendan is a positive inotropic calcium sensitizer available in Japan functioning through a combination of cyclic adenosine monophosphate dependent action and calcium sensitizing properties. In addition, action of PDE3 inhibitor has the potential to improve left ventricular diastolic dysfunction. We experienced the case of apical hypertrophic cardiomyopathy preserved ejection fraction whose symptom improved by treating with low doses of pimobendan and review of the literature.