Left Ventricular Pressure-Volume Relationships

It has been shown in man that myocardial ischemia, whether precipitated by exercise or pacinginduced tachycardia, is associated with abnormalities of left ventricular end-diastolic pressure. There has been controversy as to whether this relationship is due to decreased myocardial compliance or to an increase in left ventricular volume as a manifestation of left ventricular failure. Simultaneous measurements of left ventricular pressure and left ventricular volume using ultrasonic techniques were carried out in five normal subjects and 21 patients with coronary artery disease. In the normal subjects a decrease in left ventricular end-diastolic pressure during pacing was associated with a decrease in left ventricular end-diastolic volume, and during interruption of pacing, pressures and volumes returned to normal. In nine patients with coronary artery disease who did not develop angina, a similar response was seen. In 12 patients with coronary artery disease who developed angina during pacing, the reduction in left ventricular end-diastolic volume during pacing was less marked than the other groups and during periods of interruption the increase in diastolic pressure to 26 mm Hg was accompanied by an increase in left ventricular end-diastolic volume to 24% above control values. The end-systolic volume showed a similar increase during myocardial ischemia. These data suggest that the changes in left ventricular filling pressure seen during myocardial ischemia are related to increase in left ventricular volume but do not exclude the possibility that there may be accompanying changes in left ventricular diastolic compliance.