Assessment of risk factors and left ventricular function in patients with slow coronary flow

Slow coronary flow (SCF) is characterized by delayed distal vessel opacification in the absence of significant epicardial coronary disease. Life-threatening arrhythmias and sudden cardiac death can occur; however, the pathological mechanism and influence on left ventricular function remain undetermined. We aimed to assess the risk factors and left ventricular (LV) function in SCF and evaluate the relationships between thrombolysis in myocardial infarction frame count (TFC) and the number of involved coronary arteries with LV function in patients with SCF. We included 124 patients who underwent coronary angiography because of symptoms of angina; 71 patients with angiographically proven SCF and 53 cases with normal coronary flow pattern. SCF was diagnosed as TFC >27 in at least one coronary artery. Complete blood count and biochemical parameters were compared between the two groups. Conventional echocardiography and tissue Doppler imaging were used to assess LV systolic and diastolic function. Platelet aggregation rate induced by ADP was an independent predictor of SCF and positively correlated with coronary artery mean TFC (mTFC) (r = 0.514, P < 0.001) and the number of coronary arteries with SCF (r = 0.628, P < 0.001). Early diastolic mitral inflow velocity (E) (0.66 ± 0.15 vs. 0.74 ± 0.17, P = 0.008), ratio of early to late diastolic mitral inflow velocity (E/A) (0.95 ± 0.29 vs. 1.15 ± 0.35, P = 0.002), global myocardial peak early diastolic velocity (gVe) (4.41 ± 1.25 vs. 4.96 ± 1.45, P = 0.037), and ratio of global myocardial peak early to late diastolic velocity (gVe/gVa: 1.09 ± 0.45 vs. 1.36 ± 0.58, P = 0.006) were decreased in patients with SCF compared with controls. gVe (3 vs. 0 branches, 4.08 ± 1.14 vs. 4.97 ± 1.45, respectively, P = 0.008) deteriorated significantly in patients with SCF involving three coronary arteries. mTFC negatively correlated with E and E/A (r = -0.22, P = 0.02; r = -0.20, P = 0.04, respectively). The number of coronary arteries with SCF negatively correlated with E, E/A, gVe and gVe/gVa (r = -0.23, P = 0.02; r = -0.25, P = 0.009; r = -0.25, P = 0.008; r = -0.21, P = 0.03, respectively). Platelet aggregation rate induced by ADP was an independent predictor of SCF and positively correlated with coronary artery TFC and the number of affected coronary arteries. Left ventricular global and regional diastolic function was impaired in SCF patients. Furthermore, the number of coronary arteries involved rather than coronary artery TFC determined the severity of left ventricular dysfunction in patients with SCF.