Drugs with negative inotropic effect are widely administered and have produced reduction of left ventricular pressure gradient (LVPG) in patients with hypertrophic obstructive cardiomyopathy (HOCM). However, it is difficult to select the most effective drug for each patient with HOCM. The aim of this study is to compare reduction of LVPG by pilsicainide, a pure Na channel blocker, with disopyramide, cibenzoline, beta blocker and Ca channel blocker.

Methods: LVPG and LV function were measured before and after intravenous administration of each drug. One group consisting of 12 patients with HOCM (A group; mean LVPG=84.5±28.5 mmHg) was evaluated with the effects of disopyramide, verapamil, and propranolol. Another group of 12 patients (B group; mean LVPG=92.5±40.3 mmHg) was evaluated with disopyramide, cibenzoline, and pilsicainide. LVPG, % fractional shortening (%FS), E/A ratio and deceleration time (DcT) were estimated by echocardiography (EC) before and after each drug.

Results: In A group (N=12), percent reduction of LVPG was -9.2±13.1% with verapamil (77.9 to 70.4 mmHg; p=0.07), -19.1±21.6% with propranolol (87.1 to 74.0 mmHg; p=0.06), and -63.6% with disopyramide (84.3 to 30.2 mmHg; p<0.0001). Disopyramide was the most effective compared with verapamil and propranolol (P<0.001 and P<0.001, respectively). In B group (N=12), percent reduction of LVPG were -55.5±28.0% with disopyramide (from 92.5 to 40.3 mmHg; P<0.001), -58.5±21.3% with cibenzoline (from 103.1 to 44.4 mmHg; P<0.001), -54.5±15.5% with pilsicainide (from 107 to 47.5 mmHg; P<0.001), suggesting in equal effects for reduction of LVPG among these class I drugs. %FS significantly decreased, E/A ratio significantly increased, and DcT significantly prolonged with these class I drugs compared with verapamil and propranolol. The difference in all parameters by EC between these class I drugs was statistically non-significant.

Conclusions: These results suggest that efficacy for reduction of LVPG by pilsicainide with Na channel blocking property alone was equal to disopyramide and cibenzoline with both Na and Ca channel blocking property, and Na channel blocking effect predominantly leads to attenuate LVPG in patients with HOCM, compared with Ca channel blocker or beta blocking agent.