Microvascular dysfunction common in patients referred for stress testing

CHICAGO — Men and women who had been referred for stress testing had similar rates of impaired coronary flow reserve, with microvascular dysfunction affecting more than 40% of both sexes, researchers found.

Venkatesh L. Murthy, MD, PhD, of the Cardiovascular Medicine and Cardiovascular Imaging Program at Brigham and Women’s Hospital, conducted a study to determine whether coronary microvascular dysfunction is uniquely common in women compared with men and to identify risk factors for microvascular dysfunction. Murthy presented the findings at the American College of Cardiology’s 61st Scientific Sessions.

Analysis focused on 307 women and 97 men, for a total of 404 consecutive patients. Eligible participants had been referred for rest or stress Rb-82 positron emission tomography (PET) scan to evaluate for suspected coronary artery disease, and had normal myocardial perfusion imaging and no evidence of coronary artery calcifications.

The primary outcome measure was coronary flow reserve ,2, which was evaluated between sex difference/equivalence. Secondary outcomes included death or MI.

Women had higher myocardial blood flow than men after adjusting for differences in cardiac work (1.2 [interquartile range 0.8-1.7] vs. 0.9 [IQR 0.7-1.2] ml/min/g, P<.0001). Peak stress myocardial blood flow also was higher in women (2.4 [IQR 1.8-3.3] vs. 1.9 [1.4-2.5] ml/min/g, P<.0001).

Both sexes demonstrated impaired coronary flow reserve, with women at 48% and men at 44% (P=.56).

Patients referred for evaluation for chest pain were most likely to have impaired coronary flow reserve (58% of women and 68% of men; P=.25).

Median coronary flow reserve was 2.05 for women (IQR, 1.64-2.57) and 2.04 for men (IQR, 1.58-2.49; P=0.98).

The only univariate and multivariate predictors of impaired coronary flow reserve were diabetes (OR=1.6; P=.04) and tobacco use (OR=2.5; P=.01).

“Impaired coronary flow reserve is extremely common among patients who are referred for stress testing, even if they have a normal stress test and a normal coronary artery calcium score,” Murthy told Cardiology Today. “This means that many patients who come to the clinic with symptoms but have two normal tests (stress PET and calcium score), could still have a cardiac reason for their symptoms.”

Murthy added that low coronary flow reserve carries adverse prognosis, even with normal perfusion and zero coronary artery calcification. – by Rob Volansky

For more information:

Murthy V. 910-3. Presented at: the American College of Cardiology 61st Scientific Session & Expo; March 24-27, 2012; Chicago.

Disclosure: Dr. Murthy reports commercial and CME relationships with multiple institutions.