The evolution of myocardial ischaemia during percutaneous transluminal coronary angioplasty

Balloon inflation during percutaneous transluminal coronary angioplasty is a useful human model of acute coronary occlusion and regional myocardial ischaemia. We assessed the prevalence and duration of ischaemia during successive sixty-second balloon inflations in sixteen patients undergoing routine single vessel angioplasty by continuous six lead electrocardiography and cross-sectional echocardiography. The influence of rate-pressure product on the evolution of ischaemia was also evaluated. ST segment elevation developed in fourteen of the patients within 19 +/- 12 seconds and returned to baseline within 20 +/- 9 seconds of deflation. Reciprocal ST segment depression occurred in four patients, only one of whom had multivessel disease. Wall motion abnormalities on echocardiography occurred in all sixteen patients and were seen significantly earlier than electrocardiographic changes. Thus, dyskinesis developed 15 +/- 5 seconds after balloon inflation and disappeared 13 +/- 3 seconds following balloon deflation. Time to onset of ischaemia by both methods remained constant during successive balloon inflations. Rate pressure product prior to balloon inflation correlated inversely with time to onset of ischaemia detected by either technique: r = -0.73, P less than 0.05 (ECG), r = -0.65, P less than 0.05 (echocardiography). Nevertheless, evidence of ischaemia developed within 30 seconds in all patients regardless of rate-pressure product. This investigation indicates that electrocardiography and cross-sectional echocardiography have similar sensitivity for the detection of acute ischaemia during coronary angioplasty although echocardiographic change is seen significantly earlier. Resting myocardial oxygen consumption, as reflected by rate-pressure product, is an important determinant of time to onset of ischaemia following balloon inflation.