Clinical strategy for coronary microvascular dysfunction in patients with chest pain of unknown cause - The role of treadmill exercise testing

Coronary microvascular dysfunction might contribute to myocardial test (TET) was proposed for its clinical role in detecting myocardial ischemia in this heterogeneous patient group. We use a two-step strategy to assess whether the results of TET could be related to coronary microvascular dysfunction in such patients. A total of 112 patients with recurrent chest pain and normal coronary angiograms were evaluated. In 68 (61%) of them, cardiac or non-cardiac causes of chest pain were first identified by serial cardiac, gastroenterological, psychological, and neurological evaluations. Among them, 4 patients (1 anxiety disorder, 1 esophageal motility disorder and 2 esophageal reflux) failed to respond to the given treatment. These 4 patients and another 44 patients who had no identifiable cause for chest pain were then admitted and undertook coronary angiograms for further evaluation. Great cardiac venous flow (GCVF) was measured both before and after dipyridamole infusion. Baseline hemodynamics did not differ between the 22 patients with and the 21 without exercise-induced myocardial ischemia. After dipyridamole infusion, maximum GCVF was significantly lower, minimum coronary vascular resistance higher, and coronary flow reserve lower in the former than the latter group. In these patients with chest pain of unknown cause, the sensitivity of TET to detect a reduced CFR < 2.5 was 100%, specificity 84%, positive predictive rate 82%, and negative rate 100%. The results suggest that ischemic-like ECG during exercise was related to coronary microvascular dysfunction in patients with recurrent angina, while other causes of chest pain were unlikely.