The presence of collaterals was shown to be associated with improved outcomes in patients with CAD. However, the magnitude of myocardial perfusion provided by collateral circulation during experimental balloon occlusion is described for the first time.
A retrospective substudy of a larger cohort, patients without a history of prior myocardial infarction, bypass surgery, or angiographically visible collaterals underwent elective percutaneous transluminal coronary angioplasty (PTCA) to a single coronary vessel between September 1995 and April 1996 are included. 1100 MBq of 99mTc-sestamibi was injected after 3 minutes of full intracoronary balloon inflation, and SPECT imaging of vessels occurred within 3 hours of injection (occlusion study). A second SPECT imaging study the day after PTCA with 1100 MBq of 99mTc-sestamibi was done (control study). The ratio of occlusion and extent of perfusion between the occlusion and control studies were calculated. Statistical analysis was done using software R, and between-group differences were tested using the Wilcoxon test. A P value < .05 was considered statistically significant.
PTCA was performed in 21 patients with a mean balloon occlusion time of 5 minutes. The size of perfusion defect was 16% of the left ventricle, and the collateral perfusion within the perfusion defect was 64% of normal perfusion within that region for the entire cohort. Collateral perfusion was negatively correlated with perfusion defect size (R2 = 0.85; P < .001). Smaller perfusion defects had greater collateral perfusion than larger perfusion defects but did not differ by age or sex.
On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provide 60% of the perfusion that reaches the jeopardized myocardium.