OBJECTIVES--To investigate the relation between diastolic aortic pressure response and left ventricular systolic dysfunction during percutaneous transluminal coronary angioplasty. BACKGROUND--The abnormal diastolic blood pressure rise during exercise in patients with coronary artery disease probably reflects left ventricular systolic dysfunction rather than the number of stenosed coronary arteries. METHODS--Aortic blood pressures and left ventricular systolic function indices were estimated in 26 patients with single proximal stenosis of the left anterior descending coronary artery both before and during angioplasty. RESULTS--During coronary angioplasty all patients presented an increase in diastolic aortic pressure (P << 0.001), 8-12s before intracoronary electrocardiographic changes. During acute ischaemia there was a decrease in left ventricular ejection fraction (P << 0.001) and stroke volume (P << 0.001) and an increase in end systolic volume (P << 0.001) and left ventricular end diastolic pressure (P << 0.001). No statistically significant changes were observed in systolic blood pressure or heart rate. The aortic diastolic pressure increase was correlated with the decrease in ejection fraction (r = -0.95, P << 0.001) and with the increases in end systolic volume (r = 0.86, P << 0.001) and left ventricular end diastolic pressure (r = 0.85, P << 0.001). CONCLUSIONS--The rise in diastolic aortic pressure during percutaneous transluminal coronary angioplasty occurs earlier than intracoronary electrocardiographic changes and is related to ischaemic left ventricular systolic dysfunction.