An equation to predict the changes in peak left ventricular pressure in hypertrophic obstructive cardiomyopathy after treatment: application to the administration of disopyramide

A theoretical equation was derived based on the time-varying elastance mode l to predict theoretically the relationship between the delay in the onset of left ventricular outflow obstruction and the reduction in peak left vent ricular pressure (LVP) caused by treatment in hypertrophic obstructive card iomyopathy (HOCM). EGG, LVP, and other hemodynamic parameters were measured during catheterization at a constant heart rate with atrial pacing in 16 p atients with HOCM before and after intravenous administration of disopyrami de (1 mg/kg). After disopyramide administration. the duration between the R wave of the ECG and the onset of obstruction (T-1) was prolonged significa ntly (from 117 +/- 30 to 155 +/- 32 ms, P < 0.0001), and peak LVP was reduc ed significantly (from 222 +/- 42 to 177 +/- 39 mmHg, P < 0.0001). The rela tion between the prolongation of T-1 and the percent reduction in peak LVP was predicted well by the theoretical equation (coefficient of determinatio n R-2 = 0.926). Our model simplifies the therapeutic strategy for reducing the left ventricular outflow pressure gradient in patients with HOCM, which is to delay the time of onset of obstruction by some methods.