Scintigraphic quantification of asynchronous myocardial motion during the left ventricular isovolumic relaxation period: A study in the dog during acute ischemia

Asynchronous motion of left ventricular myocardium during the period of left ventricular isovolumic relaxation has often been observed in patients with coronary artery disease. Detection and quantitation of this abnormality with noninvasive nuclear tracer methods, however, have not yet been reported. Thus, functional images of regional left ventricular time to minimum counts (or volume), computed from gated blood pool image sequences, were analyzed to detect and quantitate myocardial asynchrony during this interval. The method was tested by comparing regional with global time to minimum counts before and after coronary artery occlusion in the awake dog.After occlusion, minimum counts in the ischemic region occurred later in the cardiac cycle than did global minimum counts (average difference 69 ± 37 ms, p < 0.001). Before occlusion, however, minimum counts in the same region occurred at the same moment as global minimum counts (average difference 4 ± 12 ms, NS). Thus, acute ischemia in dogs produces a pronounced asynchrony in myocardial motion during the earliest moments of diastole. The magnitude of this asynchrony (69 ms) probably corresponds to the length of the global isovolumic relaxation period in these animals after occlusion. This method might be useful in detecting and quantitating isovolumic asynchrony in ischemia and changes in this asynchrony with therapy (verapamil therapy, for example)