Effects of Acute Coronary Occlusion and Previous Ischaemic Injury on Left Ventricular Wall Motion in Humans

Objective: To assess the acute effects of single and repeated coronary artery occlusions, during percutaneous transluminal coronary angioplasty (PTCA), on left ventricular long axis function in patients with stable and unstable angina.

Design: Prospective examination of ventricular systolic and diastolic long axis function using M mode echocardiography and transmitral Doppler in patients with significant coronary artery stenosis and either stable or unstable angina, during routine PTCA.

Setting: A tertiary referral centre for heart disease with cardiac catheterisation and echocardiographic facilities.

Subjects: 36 patients, age (SD) 60 (8) years, with significant coronary artery disease undergoing PTCA (mean duration 100-130 seconds) to the left anterior descending coronary artery (LAD) in 18 patients, native LAD or its vein graft in eight, and right coronary artery in 10. Controls were 21 normal subjects, age 58 (11) years. RESULTS-AT BASELINE: in systole, total long axis excursion was reduced at septal, posterior, and right sites in patients with LAD disease, at right site in those with vein grafts, and at septal and right sites in patients with right coronary artery disease. Peak shortening rate was often reduced in all patients and onset of shortening delayed with respect to the Q wave in patients with LAD disease. In diastole, onset of lengthening was always delayed, peak lengthening rate reduced, and relative A wave amplitude increased in all patients. There was a consistent abnormal shortening of the long axis during the isovolumic relaxation period in the 14 patients with unstable angina, not seen in the others. Transmitral A wave velocity was also increased and the onset of E wave delayed with respect to A2. At first balloon inflation: the extent of pre-existing systolic and particularly diastolic abnormalities consistently increased in patients with LAD or right coronary artery occlusion. This was associated with further delay in the onset of the transmitral Doppler E wave as its peak velocity fell and E/A ratio increased. In unstable angina, balloon inflation caused minor changes only in systolic function and no change in diastolic function. At second balloon inflation: systolic changes were the same as with the first inflation, while diastolic changes were attenuated by 10-15%.

Conclusions: In stable angina intracoronary balloon inflation aggravated pre-existing systolic and diastolic abnormalities in the territory of the occluded vessel, indicating the dependence of both on coronary flow. In unstable angina balloon inflation caused only minor deterioration in systolic function, and diastolic changes-including the characteristic abnormal shortening during isovolumic relaxation-were unaffected. Thus resting abnormalities of left ventricular function in unstable angina are effectively dissociated from acute changes in coronary flow. Overall, the severity of systolic disturbances was unaltered by a second balloon inflation, but diastolic disturbances were attenuated by 10-15%, compatible with ischaemic preconditioning or recruitment of collaterals.