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

OBJECTIVES The present study evaluated the impact of recruitable collaterals on regional myocardial perfusion measured by 99mtechnetium (Tc)-sestamibi single-photon emission computerized tomography (SPECT) during temporary coronary occlusion and related these estimates to the coronary wedge pressure and electrocardiographic (ECG) ST-segment changes. BACKGROUND Clinical variables (angina and ECG changes) and intracoronary flow and pressure recordings have indicated a protective role of recruitable collaterals on myocardial perfusion during percutaneous transluminal coronary angioplasty (PTCA). METHODS Thirty patients (mean age 55 years, SD 9; 20 men) with stable angina pectoris and proximal nonoccluding single-vessel left anterior descending coronary artery (LAD)-stenosis scheduled for PTCA were included. Visualization of recruitable collaterals by ipsilateral and contralateral contrast injection, registration of coronary wedge pressure and injection of 99mTc-sestamibi during 90-s LAD occlusions were undertaken. A rest perfusion study was performed within four days before PTCA. As an estimate of the severity of regional hypoperfusion during occlusion, an occlusion/rest count ratio was calculated (mean defect pixel count during occlusion divided by mean pixel count in identical regions at rest). RESULTS The scintigraphic occlusion/rest count ratio was higher in patients with recruitable collaterals (n = 16), 67 ± 11%, compared to patients without collaterals (n = 14), 60 ± 6% (p < 0.05). The occlusion/rest count ratio correlated with the coronary wedge pressure (R2 = 0.34; p < 0.001). The occlusion/rest count ratio was lower, 61 ± 6%, in patients with ST-segment elevation (n = 23) versus 74 ± 9% in patients without ST-segment elevation (n = 7) (p < 0.0001). CONCLUSIONS Using 99mTc-sestamibi SPECT imaging during brief episodes of coronary occlusion, the severity of regional myocardial hypoperfusion was reduced by the presence of recruitable collaterals in a selected patient population with proximal LAD stenoses. Our results demonstrate a protective effect of recruitable collaterals on myocardial perfusion during temporary coronary occlusion.