Beta-blocker therapy combined with low-dose pimobendan in patients with idiopathic dilated cardiomyopathy and chronic obstructive pulmonary disease: report on two cases.

Pimobendan is an inotropic and vasodilating drug with phosphodiesterase (PDE) III-inhibiting and calcium-sensitizing effects. It may also have a bronchodilatory effect by inhibiting PDE III in airway smooth muscle. We tried a beta-blocker combined with low-dose pimobendan in 2 patients who had refractory heart failure of NYHA functional class III or IV with idiopathic dilated cardiomyopathy (DCM) and chronic obstructive pulmonary disease (COPD). Both of them had previously failed to tolerate beta-blocking drugs because of the exacerbation of bronchospasm. After pimobendan was administered at 1.25 to 2.5 mg daily, metoprolol could be successfully introduced from a low dose of 1.25 mg daily without decreasing the peak expiratory flow rate. Over the next 1 to 2 years, they have continued beta-blocker therapy. One is currently receiving 10 mg daily of bisoprolol and another is taking 15 mg daily of metoprolol, and both are in NYHA functional class II without worsening heart failure or COPD. The combination of beta-blocker with low-dose pimobendan may be helpful for patients with DCM and COPD, but further clinical investigation is required.