Functional significance of recruitable collaterals during temporary coronary occlusion evaluated by Tc-99m-sestamibi single-photon emission computerized tomography

Objectives. The present study evaluated the impact of recruitable collatera ls on regional myocardial perfusion measured by (99m)technetium (Tc)-sestam ibi single-photon emission computerized tomography (SPECT) during temporary coronary occlusion and related these estimates to the coronary wedge press ure and electrocardiographic (ECG) ST-segment changes. Background. Clinical variables (angina and ECG changes) and intracoronary f low and pressure recordings have indicated a protective role of recruitable collaterals on myocardial perfusion during percutaneous transluminal coron ary angioplasty (PTCA). Methods. Thirty patients (mean age 55 years, SD 9; 20 men) with stable angi na pectoris and proximal nonoccluding single-vessel left anterior descendin g coronary artery (LAD)-stenosis scheduled for PTCA were included. Visualiz ation of recruitable collaterals by ipsilateral and contralateral contrast injection, registration of coronary wedge pressure and injection of Tc-99m- sestamibi during 90-s LAD occlusions were undertaken. A rest perfusion stud y was performed within four days before PTCA. As an estimate of the severit y of regional hypoperfusion during occlusion, an occlusion/rest count ratio was calculated (mean defect pixel count during occlusion divided by mean p ixel count in identical regions at rest). Results. The scintigraphic occlusion/rest count ratio was higher in patient s with recruitable collaterals (n = 16), 67 +/- 11%, compared to patients w ithout collaterals (n = 14), 60 +/- 6% (p < 0.05). The occlusion/rest count ratio correlated with the coronary wedge pressure (R-2 = 0.34; p < 0.001). The occlusion/rest count ratio was lower, 61 +/- 6%, in patients with ST-s egment elevation (n = 23) versus 74 +/- 9% in patients without ST-segment e levation (n = 7) (p < 0.0001). Conclusions. Using Tc-99m-sestamibi SPECT imaging during brief episodes of coronary occlusion, the severity of regional myocardial hypoperfusion was r educed by the presence of recruitable collaterals in a selected patient pop ulation with proximal LAD stenoses. Our results demonstrate a protective ef fect of recruitable collaterals on myocardial perfusion during temporary co ronary occlusion. (C) 2000 by the American College of Cardiology.