Demo takes CMR’s pulse as sleuth for microvascular disease

Quantitative cardiac magnetic resonance (CMR) imaging can assess variations in myocardial blood flow throughout the cardiac cycle, making it a potential tool for spotting microvascular diseases.

Manish Motwani, MB ChB, of the Leeds Institute of Cardiovascular and Metabolic Medicine at the University of Leeds in the UK, and colleagues proposed that cyclic variations in CMR myocardial blood flow might serve as a useful diagnostic tool for diseases such as atherosclerosis and hypertension, if changes throughout the entire cardiac cycle can be tracked. To test this idea as a proof of principle, they enrolled 30 healthy volunteers to undergo a single stress and rest perfusion CMR study on a 1.5 T scanner (Intera, Philips Healthcare).  

They obtained perfusion data on each volunteer at five different times points: early-systole, mid-systole, end-systole, early-diastole and end-diastole. They performed rest CMR 15 minutes after the stress test, applying the same imaging parameters. Their overall image quality was rated as excellent with negligible artifacts.

There was significant variation in stress myocardial blood flow, with maximum and minimum values at end-diastole and end-systole and a mean maximal cyclical variation of 26 percent. In all the volunteers, they tracked significant cyclic variation that became successively reduced throughout systole and increased in diastole. At rest, they found no significant cyclical variation in myocardial blood flow.

Those findings were consistent with other imaging research on microcirculation and CMR, but none of that work has examined changes throughput the cardiac cycle, according to Motwani et al.  

“Considering the nature of coronary hemodynamics, cyclic MBF [myocardial blood flow] changes may reveal new physiological information because they are a function of coronary flow, myocardial contraction and microvascular condition,” they wrote.

They added that increased maximal cyclical variation might prove to be a marker for microvascular disease in patients with diabetes, hypertension or preclinical coronary artery disease. “Therefore, using CMR to assess MBF throughout the cardiac cycle and determine parameters such as MCV [maximal cyclical variation] may be useful in the future assessment of diseases known to alter microvascular function—but further studies in these disease states are clearly needed.”

The study was published online Jan. 29 in the Journal of Cardiovascular Magnetic Resonance.