The increased left ventricular end-diastolic pressure associated with myocardial ischemia was studied in 19 patients at cardiac catheterization. Single plane left ventriculograms were performed using high fedelity micromanometer tipped catheters before and immediately following rapid atrial pacing. Left ventricular diastolic properties were evaluated by constructing diastolic pressure-volume curves from the simultaneous pressure and volume data. In seven control patients, there was no significant change in left ventricular hemodynamics or the diastolic pressure-volume curve after atrial pacing. Twelve patients with significant coronary artery disease developed angina during pacing and had an increased left ventricular end-diastolic pressure (18 +/- 2 mm Hg, control, vs 30 +/- 2 mm Hg, angina, P less than .01) in the immediate post-pacing period. In these patients, the post-pacing ejection fraction was modestly decreased (0.63 +/- 0.03, control, vs 0.57 +/- 0.03, angina P less than 0.01), and left ventricular volumes at end systole (59 +/- 8 cc, control, vs 74 +/- 9 cc, angina, P less than 0.0125) were increased. The post-pacing diastolic pressure-volume curves in all 12 patients were shifted upward as compared with control so that for any given diastolic volume, pressure was higher during angina. The data indicate that the increased left ventricular diastolic pressure during myocardial ischemia is the result of both impaired left ventricular systolic performance and altered left ventricular diastolic properties.