Myocardial Ischemia in Patients with Slow Coronary Artery Flow Assessed by Coronary Sinus Blood Lactate Levels

Slow run-off dye in the coronary arteries during selective coronary angiography is known as slow coronary artery flow (SCAF). A few studies have been performed concerning its etiology and treatment since it was defined. It is accepted that abnormal increase of resistance at the microvascular level causes SCAF. In this study, the question whether coronary slow flow is associated with myocardial ischemia was analyzed by coronary sinus blood lactate screening under atrial pacing. Ten patients with slow coronary flow (7 males, 3 females; mean age 48±8 yrs. were included in the study. TIMI frame count method was used to determine the coronary slow flow. All patients had exercise testing with using Bruce protocol after coronary angiography. We have performed atrial pacing to all patients and coronary sinus, and aortic blood samples was collected for the measurement of lactate levels during rest and peak heart rates. Lactate extraction was calculated using a formula: (LAC ao- LAC cs) / (LAC ao). All exercise tests were negative by using standard criteria. Coronary sinus blood lactate level was 9.52±1.89 mg/dl at rest and 9.33±1.68 mg/dl at maximum heart rate (p>0.05). There was no difference between lactate extraction at rest and maximum heart rate (0.12±0.04 vs 0.12±0.04; p>0.05). In conclusion, there was no metabolic evidence of myocardial ischemia obtained in patients slow coronary flow. However, there is need for further large, studies concerning the relationship betwen myocardial ischemia and coronary slow flow and also to long-term prognosis.