Epicardial fat volume independently tied to coronary microvascular dysfunction
An association exists between epicardial fat volume (EFV) and coronary microvascular dysfunction (CMD), according to a study presented at the 21st Asia Pacific Society of Cardiology Congress held in Singapore.
This finding highlights the importance of identifying surrogate markers of CMD on computed tomography coronary angiogram (CRCA), which is commonly used to examine patients presenting with chest pain, according to researchers.
In this study, patients (n=134; mean age 59.2 years; 49.2 percent male) had a mean body mass index of 27.5 kg/m2. Of these participants, 7 percent were diabetic, 37 percent had hypertension and 43 percent were smokers. [APSC 2017, abstract MP-06]
Overall, patients had a mean EFV of 137.0 cm3 and a mean myocardial blood flow reserve (MBFR) of 2.18. A total of 54 patients (40 percent) presented with CMD, which is defined as MBFR <2.0. Moreover, 43 participants (32 percent) had coronary artery calcium score (CACS) of 0, with a mean CACS of 115. Their mean Framingham Risk Score (FRS) was 17.6.
Univariate analysis revealed that MBFR decreased with increasing age (β=‒0.0143; 95 percent CI, ‒0.0232 to ‒0.0055; p=0.002), EFV (β=‒0.0020; ‒0.0036 to ‒0.0005; p=0.012) and CACS (β=‒0.0004; ‒0.0007 to ‒0.0001; p=0.004). Based on multiple regression analysis, EFV (β=‒2.22; ‒4.02 to ‒0.41; p=0.016) and CACS (β=‒0.37; ‒0.64 to ‒0.10; p=0.008) remained significant and were independent predictors of MBFR.
Researchers recruited patients who were referred to a cardiology OPD clinic for assessment of chest pain and subsequently had a computed tomography coronary angiography (CTCA), which showed a luminal diameter stenosis <50 percent to examine the association of EFV, CACS and FRS with CMD, as measured by dipyridamole vasodilator myocardial contrast echocardiography in patients presenting with chest pain and unobstructed coronary arteries.
Patients who had ischaemic/valvular heart disease, left ventricular hypertrophy or ejection fraction <55 percent were excluded. There were 59 participants (44 percent) who had completely normal coronary arteries on CTCA.
EFV was measured through serial slices of parietal pericardium from bifurcation of the pulmonary artery to diaphragm with a range of -45 to -190 household unit. A measure of coronary microvascular function, MBFR was calculated using dipyridamole vasodilator myocardial contrast echocardiography.
“Epicardial fat is a biologically active fat depot around the heart, constrained by visceral pericardium and directly surrounds major epicardial arteries,” according to researchers.
“EFV has been previously correlated with the presence of coronary artery disease, CACS and FRV. More recently, a single study has shown that epicardial fat thickness but not volume, is associated with CMD. However, the relationships between CACS, FRV and EFV with CMD is unknown,” they added.
In a systematic review of therapies, researchers noted the absence of a standardized approach to defining CMD, which made the evaluation of treatment strategies for microvascular angina challenging. [JACC Cardiovasc Imaging 2015;8:210–220]
“There is still considerable work that needs to be done to definitively address optimal therapy for CMD,” researchers said. “Once common definitions are adopted and CMD is routinely assessed in patients with chest pain without obstructive CAD, traditional and novel treatment strategies can be assessed to reduce symptoms, improve quality of life and reduce risk in this prevalent and morbid disease.”