Disopyramide and lignocaine. A comparison of cardiac effects using echocardiography

1 The cardiac effects of disopyramide (D) and lignocaine (L) were measured and compared in normal volunteers (D n=4; L n=3) following the establishment of a series of three steady-state drug plasma concentrations spanning the therapeutic range (1.5-5 micrograms base ml-1). 2 During control and steady-state periods multiple measurements were made of heart rate, blood pressure, drug concentrations and echocardiographic measurement of cardiac dimensions and estimated left ventricular function. 3 No change in heart size or estimated function occurred with L except for a small increase in estimated cardiac output (+0.5 1 min-1) secondary to a small rise in heart rate (maximum +7 beats min-1). Blood pressure rose slightly (maximum +11 mmHg). 4 D caused an increase in heart size, marked at end systole (+0.63 cm), and a decrease in echo indices of ventricular function (25-33%). These changes were related to plasma drug concentration but were not reflected in cardiac output estimation since heart rate rose (+15 beats min-1). Blood pressure also rose (+10 mmHg). 5 Significant differences were shown between D and L at similar plasma drug concentrations. The negative inotropic effect of D may be greater than previously suggested and clinically important.