Coronary Microvascular Dysfunction in Patients with Elevated Filling Pressures During Exercise

Introduction: Ischemia due to coronary microvascular dysfunction (CMD) may cause a loss of lusitropy and resultant elevated filling pressures which can worsen with exercise. CMD is prevalent in patients with heart failure with preserved ejection fraction (HFpEF) and exercise studies are useful in diagnosing early HFpEF. The relationship between CMD and early HFpEF is not well characterized. Hypothesis: CMD is prevalent in patients with elevated pulmonary capillary wedge pressure (PCWP) at rest and those with normal resting PCWP but elevated post-exercise PCWP. Methods: All patients without obstructive CAD who underwent cardiac catheterization with coronary physiology and exercise bicycle studies at the University of Chicago Medical Center between 2015-2021 were included. Elevated resting PCWP was defined as > 15 and elevated post-exercise PCWP was defined as > 25. Patients were separated into three groups: elevated resting PCWP (group 1), normal resting & elevated exercise PCWP (group 2), and normal resting and exercise PCWP (group 3). Results: A total of 22 patients (mean age 56 + 10 years, 77% female) were studied. There were 9 patients in group 1, 8 patients in group 2, and 5 patients in group 3. A diagnosis of HFpEF was present in all patients in groups 1 and 2 and no patients in group 3. There was a nonsignificant trend towards lower median CFR in groups 1 (2.1 IQR 1.6-2.8) and 2 (2.3 IQR 1.75-3.65) compared to group 3 (3.8 IQR 1.8-5.5; Figure 1). Similarly, there was a nonsignificant trend towards higher median IMR in groups 1 (23.2 IQR 16.9-41.3) and 2 (25.9 IQR 19.0-35.2) compared to group 3 (14.4 IQR 11-25; Figure 1). Conclusion: Like patients with elevated resting PCWP, patients with normal resting and elevated post-exercise PCWP tend to have lower CFR and higher IMR than those patients with normal pre and post-exercise PCWP. This may indicate that CMD plays a role in the development of early HFpEF though more patients are needed to further characterize this relationship.