Coronary flow: clinical considerations

Pericardial fat volume is related to endothelial-mediated coronary blood flow in women with suspected coronary microvascular dysfunction. A report from the Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction (WISE-CVD) study

Background

Coronary microvascular dysfunction is prevalent in women with signs and symptoms of ischemia but no obstructive coronary artery disease (CAD) and is associated with an adverse prognosis. Elevated pericardial fat volume predicts adverse cardiac events, but mechanistic pathways of the association are not well understood.

Methods

118 women enrolled in the NHLBI-sponsored Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction study with suspected coronary microvascular dysfunction but no obstructive CAD underwent adenosine stress 1.5 T cardiovascular magnetic resonance imaging (CMR) imaging and invasive coronary reactivity testing. Semi-quantitative myocardial perfusion reserve index (MPR) index was derived from perfusion images. Pericardial fat volume was measured by manually contouring the cardiac margins and adjacent adipose tissue on a single trans-axial HASTE slice at the level of the left main coronary artery origin and indexed to body surface-area. Simple standard deviation analysis obtained for continuous variables and frequency (percent) for categorical variables. The relationships between pericardial fat volume and coronary reactivity testing parameters were examined by correlation and multivariable regression analyses.

Results

Women with suspected coronary microvascular dysfunction had a mean age of 55 ± 10 years, body mass index (BMI) of 28 ± 7 kg/m2, 44 % had a history of smoking, 63 % hypertension, 8 % diabetes, and 20 % dyslipidemia. CMR imaging-derived pericardial fat volume and coronary blood flow response to intracoronary acetylcholine (Δ CBF) were negatively correlated (r = -0.32, p = 0.0013). After adjustment for age, number of risk factors, high-density lipoprotein (HDL), and cold pressor diameter response, pericardial fat volume remained a significant predictor of Δ coronary blood flow (p = 0.04). There was no association with other coronary reactivity testing measures or CMRI derived MPR index.

Conclusions

Among women with suspected coronary microvascular dysfunction but no obstructive CAD, pericardial fat volume appears to be related in a hypothesized adverse direction to coronary microvascular endothelial function. These results support further work confirming and extending these results to investigate pericardial fat volume as mechanistic pathway and potential treatment target for coronary microvascular dysfunction-related adverse events.Trial registration: clinicaltrials.govNCT00832702.

The "slow coronary flow" phenomenon: evidence of preserved coronary flow reserve despite increased resting microvascular resistances

INTRODUCTION

The expression "slow coronary flow phenomenon" (SCFP) indicates a slow progression of the contrast seen at the coronary angiography in the absence of epicardial stenosis and/or of other conditions associated with decreased coronary flow velocity. While microvascular abnormalities are suspected to underlie the mechanism of SCFP, they have never been directly demonstrated.

METHODS AND RESULTS

Fifteen anginal patients with a positive stress test and no evidence of epicardial lesions (obstructive coronary artery disease, coronary ectasia, or coronary spasm) were enrolled. In eight patients, the diagnosis of SCFP was made (TIMI frame count>average +2SD). All subjects underwent measurement of the coronary flow reserve (CFR) and the index of microvascular resistance (IMR) using an intracoronary thermodilution method (RADI medical systems). There was no difference between groups in age, cardiovascular risk factors, blood pressure and heart rate, coronary artery diameter and fractional flow reserve (an index of the presence of epicardial stenosis). At rest, microvascular resistances (mean transit timexdistal pressure) were significantly higher in the SCFP group (SCFP: 104+/-31 versus 53+/-27, P<0.01). Showing normal responsiveness to vasodilators, this difference was abolished after induction of hyperemia (SCFP group: 34+/-22; control: 22+/-15, P=ns); coronary flow reserve was normal in the subjects with the SCFP (3.6+/-1.6).

CONCLUSIONS

We provide the first human in vivo evidence that resting microvascular resistances are increased in patients with the SCFP. At the same time, showing an intact capacity to vasodilate, microvascular resistances were normal during hyperemia, and coronary flow reserve was not impaired in SCFP patients.