Increased TIMI frame counts in cocaine users: A case for increased microvascular resistance in the absence of epicardial coronary disease or spasm

Background: Cocaine produces adverse cardiovascular effects, some of which cannot be explained by epicardial coronary artery disease (CAD) or spasm. Hypothesis: The hypothesis of this study was that cocaine users would have increased coronary microvascular resistance, even in the absence of, recent myocardial infarction (MI), CAD, or spasm. Methods: Microvascular resistance was assessed by the corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (cTFC) method in a consecutive series of 59 cocaine users without acute or recent MI or angiographically significant epicardial stenosis (>50%) or spasm. The cTFCs in these patients were compared with 21 normal controls and with published normal cTFC values. Results: The cTFC was significantly elevated (by 26-54%) in cocaine users. The cTFCs in the left anterior descending (LAD), circumflex (LCx), and right coronary (RCA) arteries in cocaine users were 30.0+/-10.9, 34.1+/-11.5, and 28.6+/-11.8, respectively, compared with values in normal controls of 21.3+/-4.3 (p = 0.001), 24.4+/-7.2 (p = 0.001), and 22.7+/-5.1 (p = 0.04), respectively, and published normal cTFC Values (all p<0.01). An abnormally high cTFC was present in 61% of patients in the LAD, 69% in the LCx, and 47% in the RCA. Conclusions: Markedly decreased coronary blood flow velocity, indicating increased microvascular resistance, is present in cocaine users, even in the absence of acute or recent MI, or significant epicardial CAD or spasm. Increased microvascular resistance may explain many important cardiovascular manifestations of cocaine use and has therapeutic implications. Slow coronary filling may also suggest the possibility of cocaine use in patients in whom it was not otherwise suspected.