Association Between Primary Coronary Slow-Flow Phenomenon and Epicardial Fat Tissue

Primary coronary slow-flow phenomenon (CSFP) is defined as delayed opacification of contrast media in at least 1 coronary vessel in the absence of obstructive epicardial coronary artery disease (CAD) during coronary angiography. Epicardial fat tissue (EFT) surrounding coronary vessels provides paracrine effects. Released cytokines diffusing in the vessel wall may induce local inflammatory reactions that potentially result in endothelial dysfunction. The latter is thought to be the underlying cause of primary CSFP. However, to date, there are no data describing an association between EFT and CSFP. Therefore, the aim of the present study was to compare EFT thickness, clinical parameters, and outcomes in patients with and without CSFP.

Coronary angiograms with primary CSFP obtained during a 10-year period were included in the analysis. EFT was measured in the 2-dimensional echocardiographic records. Clinical and diagnostic data were compared with non-CSFP patients who were matched for age, sex, and body mass index. Long-term follow-up was conducted by telephone interview.

A total of 48 CSFP patients (90% male; mean age, 64 ± 11.4 years) were identified, resulting in a prevalence of 0.13%. CSFP was observed in 87.5% in the left anterior descending artery, 50% in the right coronary artery, and 20.8% in the circumflex artery. Almost half of all patients showed CSFP in >1 vessel. There were no differences in baseline characteristics between CSFP patients and matched controls except for smoking history (31% vs 13%; P=.03). Median EFT thickness was significantly different between patients with and without CSFP (4.9 mm [interquartile range, 4.0-6.1 mm] vs 3.9 mm [interquartile range, 3.1-4.9 mm], respectively; P<.01). No differences in outcomes were observed.

EFT is thicker in CSFP patients than in matched controls, but this appears to have no impact on long-term outcomes. Further studies are needed to elucidate the role of EFT in CSFP.