The value and correlates of left ventricular cavity assessment in dipyridamole 201Tl SPET studies

Left ventricular cavity (LVC) enlargement during SPET dipyridamole 201Tl myocardial perfusion imaging studies is a proven marker of severity of coronary artery disease. Nevertheless, the influence of the extent of myocardial infarct and ischaemia on the degree of LVC enlargement both at rest and with dipyridamole has not been clearly analysed. One hundred and one patients were studied by both dipyridamole myocardial perfusion imaging and radionuclide ventriculography within 1 week. The left ventricular ejection fraction (LVEF) was 57 +/- 9 in normal resting LVC patients (group I), 43 +/- 8 in mild LVC enlargement patients (group II) and 28 +/- 5 in moderate-to-severe LVC enlargement patients (group III). The number of fixed defects was increased in patients in group II and group III, but there was no significant differences in the number of ischaemic segments among groups. The number of ischaemic segments was much higher in patients with transient cavity dilatation than those without cavity change; nonetheless, both LVEF and the numbers of fixed segments were unchanged. The degree of LVC enlargement at rest strongly reflects the resting left ventricular systolic function as well as the extent of previous myocardial infarct. On the other hand, transient cavity dilatation during dipyridamole infusion can only reflect the extent of viable myocardium at risk.