Sequence of mechanical, electrocardiographic and clinical effects of repeated coronary artery occlusion in human beings: Echocardiographic observations during coronary angioplasty

The direct manipulation of coronary blood flow to induce regional myocardial ischemia has been almost entirely limited to experimental animal models. Thus, the detection of ischemia-induced left ventricular dysfunction in human subjects has been generally limited to observations made under conditions of diagnostic loading or during spontaneous clinical events. Percutaneous coronary angioplasty requires repeated interruptions of coronary blood flow for periods as long as 1 minute. The resulting appearance of or increase in ischemia-produced changes in myocardial function were detected by two-dimensional echocardiography in 18 patients undergoing angioplasty of 22 coronary stenoses. Accordingly, left ventricular contraction was studied during 52 episodes of regional coronary blood flow interruption and reperfusion in the process of inflating and deflating the angioplasty balloon. Before angioplasty, left ventricular wall motion was normal in 14 patients. There was mild anteroapical hypokinesia in two patients, anteroapical akinesia in one and mild inferior hypokinesia in one. Balloon inflations repeatedly produced new or increased wall motion abnormalities in the distribution of the instrumented coronary artery in 19 (86.4%) of the 22 procedures, but did not alter wall motion during angioplasty of one left circumflex artery lesion, one highly collateralized left anterior descending artery stenosis and one left anterior descending stenosis that had already caused severe anteroapical dyssynergy. Hypokinesia, usually rapidly progressing to dyskinesia, began 19 ± 8 seconds (mean ± SD) after coronary occlusion. Wall motion began to normalize 17 ± 8 seconds after reperfusion. Electrocardiographic monitoring displayed ST segment shifts in eight procedures occurring 30 ± 5 seconds after coronary artery occlusion. These changes invariably occurred only after the onset of wall motion abnormalities and preceded or accompanied the onset of chest pain, which occurred at 39 ± 10 seconds in nine procedures. Two-dimensional echocardiography performed during coronary angioplasty provides a sensitive method for studying the myocardial mechanics of transient ischemia and reperfusion in patients. With this technique, left ventricular wall motion abnormalities are observed to invariably precede electrocardiographic changes and frequently occur without symptoms, which are the most delayed manifestation of ischemia.