Microvascular Dysfunction Prevalent in Patients with Chest Pain, Non-Obstructive CAD

Patients with chest pain and non-obstructive CAD frequently have coronary microvascular dysfunction, according to a study presented at TCT 2014. Those abnormalities, however, correlate poorly with conventional CV risk factors and with findings from noninvasive functional stress testing.

Jaskanwal D.S. Sara, MBChB, of the Mayo Clinic, Rochester, Minn., and colleagues examined microvascular function in 1,439 patients (mean age 51.1 years; 34.9% male) who presented with chest pain, had non-obstructive CAD and had measurements of both coronary blood flow and coronary flow reserve performed between 1993 and 2012. Functional assessment of coronary microcirculation was performed using a Doppler guidewire within an infusion catheter placed in the middle of the left anterior descending coronary artery.

Endothelial-dependent microvascular dysfunction was defined as an increase in coronary blood flow of no more than 50% in response to increasing doses of acetylcholine, whereas endothelial-independent microvascular dysfunction was defined as a coronary flow reserve ratio of 2.5 or lower in response to increasing doses of adenosine.

The researchers split the patients into four groups according to whether neither coronary blood flow nor coronary flow reserve were impaired, only one was abnormal and the other was normal, or both were dysfunctional. Overall, 63.9% of patients had impairment of at least one of the measures, with a slightly higher prevalence in women compared with men (65.7% vs. 60.4%).

Most traditional CV risk factors were not associated the presence of microvascular dysfunction. In a multivariate analysis only age was associated with a greater likelihood of any microvascular dysfunction.

Microvascular dysfunction also did not correlate well with rates of noninvasive functional stress testing (P=.13), positive, negative and inconclusive ECG (P=.61) or imaging findings on stress testing (P=.47).

“The current study supports a need for a comprehensive assessment of coronary microvascular function at coronary angiography in [these patients],” Sara said, noting that microvascular abnormalities are functionally meaningful in that they mediate ischemia, cause angina, and are associated with a greater risk of CV events.

In response to a question about which medications might be best to treat patients with impairments of microvascular function, Sara said studies addressing that issue using agents such as ACE inhibitors, calcium channel blockers, and nitrates are still in their infancy. The next step, he added, would be a randomized trial to assess the efficacy of some of those medications.