Slow Coronary Flow is Associated With Left Ventricular Diastolic Dysfunction and Left Atrial Dilation

Background:
Slow coronary flow (SCF) phenomenon is a coronary microvascular disorder characterized by the delayed passage of angiographic contrast in the absence of obstructive epicardial coronary artery disease. Many patients with SCF suffer from angina-like chest pain and present for angiography procedures after documented positive cardiac stress tests. Although the clinical and pathological features of SCF have been previously described, the effect of SCF on cardiac function remains an area of active investigation.

Methods:
We sought to investigate the effect of SCF on left ventricular systolic and diastolic function assessed by transthoracic echocardiography (TTE). A retrospective review of 99 coronary arteries with documented SCF as defined by high TIMI frame count (TFC) was performed. Clinical information was gathered from review of TTE data collected prior to coronary angiography.

Results:
Analysis of TTE parameters of 99 coronary arteries with SCF demonstrated no impairment of left ventricular systolic function in our study population (LVEF 57.3±1.9%). However, we found that a substantial percentage of patients with SCF demonstrated some degree of diastolic dysfunction (37.5%). SCF was also associated with significant left atrial dilation. The mean left atrial volume index (LAVI) was 35.01 ml/m2 for patients with SCF (normal LAVI≤28 ml/m2). The mean TFC for this population was 40.04±1.66. The mean TFC following administration of the vasodilator adenosine was 19.54±1.92. Multinominal logistic regression analysis revealed that hyperlipidemia (OR: 2.53, p-value:<0.0001) and diabetes (OR: 3.31; p-value:<0.0001) were independent predictors of SCF in our study population.

Conclusions:
Our demonstration that the TFC in patients with SCF improves upon the administration of adenosine suggests a microvascular component playing a role in the etiology of coronary artery disease and anginal chest pain. In our patient population, SCF is strongly associated with diabetes and hyperlipidemia. Although the microvascular dysfunction underlying SCF has no impact on left ventricular systolic function, it is associated with impaired diastology and left atrial dilation.