“Under the Bridge”: Looking for Ischemia in a Patient with Intramyocardial Coronary Artery Course - The Role of the Cardiopulmonary Exercise Test

Many variables obtained during cardiopulmonary exercise test (CPET), including O₂ uptake (VO₂) versus heart rate (HR, O₂-pulse) and work rate (VO₂/Watt), provide quantitative patterns of responses to exercise when left ventricular dysfunction is an effect of myocardial ischemia (MI). Therefore, CPET offers a unique approach to evaluate exercise-induced MI in the presence of fixed or dynamic coronary arteries stenosis. 

In this paper, is examined the case of a 74-year-old sportsman (ski mountaineering) presenting with an ischemic CPET and a normal stress cardiac magnetic resonance (CMR) with dipyridamole. A coronary angiography demonstrated the presence of myocardial bridging (MB), a well-known congenital coronary anomaly that is able to generate myocardial ischemia during exercise (but not in provocative testing using coronary artery vasodilators, such as dipyridamole). 

Even if stress CMR is an accurate method to assess MI in patients with known or suspected CAD (Coronary Artery Disease), only a few MB patients have been systematically evaluated with this technique. In these subjects, due to a pure “steal-flow” vasodilator effect without a fixed obstruction, the use of dipyridamole during stress testing may result in an underestimation of MI compared with exercise. CPET provides a unique approach to assess MI due to the direct observation of functional changes during strong physiological exercise.

Despite the good diagnostic accuracy of the imaging methods (i.e., stress CMR) in MI detection, this case shows that exercise should be the method of choice in elicit ischemia in specific cases, like myocardial bridging.