Analysis and prediction of left ventricular performance under load changes during cardiac catheterization

The applicability of a computer model, which relates the transmural mechanical distribution in the left ventricle (LV) to its global function at different loading conditions, was evaluated in patients with normal to near normal LV function undergoing cardiac catheterization. Left ventriculography and measurements of aortic and LV pressures were performed at baseline conditions and repeated following rapid volume expansion with intravenous infusion of 250 to 300 ml of physiologic saline and also after sublingual isosorbide-dinitrate (ISDN) administration. Twenty patients (18 men and 2 women, average age = 53 years) underwent coronary angiography and left ventriculography. Sixteen patients had coronary artery disease with one- to three-vessel involvement and 4 had normal coronary arteries. The measured input data into the model included the end-diastolic LV volume and wall thickness, aortic pressure, heart rate, and the peripheral resistance. The model parameters of myocardial contractility and arterial system capacitance for the control baseline conditions were estimated so that an accurate match was obtained between the predicted and the measured end-systolic (ES) volume and pressure. Using these parameters, model predictions for the two load perturbations were compared to the measurements. An excellent correlation was found between the predicted and measured LV ES volumes and peak-systolic pressures (PSP) (R2 greater than 0.994). In four patients, who developed ischemic symptoms during saline injection, the prediction of end-systole volumes were lower than the measured values, suggesting an actual reduction in contractility during acute ischemia. Therefore, the model is sensitive to contractility changes. The model predicts global LV performance, under different loading conditions, including stroke work, peak developed wall stress, velocity of fiber shortening, and myocardial oxygen consumption.