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It has been hypothesized that coronary microvascular dysfunction (CMD) may be associated with the development of myocardial abnormalities associated with heart failure with preserved ejective fraction (HFpEF). Making a diagnosis of HFpEF is aided by exercise right heart catheterization (RHC) based on an abnormal pulmonary artery wedge pressure (PAWP) response during exercise. An exercise-associated increase in PAWP adjusted for the change in cardiac output (ΔPAWP/ΔCO) greater than 2 mmHg/L/min is a clinical predictor for HF outcomes and predicts exercise capacity. Although there is speculation that CMD may play a role in the development of early HFpEF, there is limited evidence that directly links CMD as assessed by an invasive coronary physiology study (ICPS) with HFpEF as measured by an exercise RHC.
Methods and Results
This study was an exploratory, retrospective cohort analysis. The study population included patients experiencing unexplained cardiovascular symptoms including chest pain and dyspnea who were referred to our institution for a RHC with exercise who had also undergone an ICPS. Patients were classified hemodynamically based on a ΔPAWP/ΔCO ≤ or > 2 with exercise. Coronary physiology interventions included Doppler flow assessment after administration of intracoronary adenosine and acetylcholine, where coronary flow reserve (CFR) and the index of microvascular resistance (IMR) were quantified during hyperemia. To date, we identified a cohort of 20 patients who met the study’s inclusion criteria. Of these, 19 completed a RHC exercise study from which 9/19 (47%) had a ΔPAWP/ΔCO > 2. Characteristics of the patients are shown in Table 1. The mean index of microvascular resistance (IMR) for patients with abnormal exercise hemodynamics was 32.6 versus 20.9 (p=0.08).
Among patients undergoing an ICPS, a relatively high proportion of these patients exhibit a ΔPAWP/ΔCO > 2 mmHg/L/min. We have also observed that in patients with an abnormal PAWP response, the mean IMR values were higher compared with patients with a normal PAWP response. Our observations support the indication that CMD may play a role in the development of early HFpEF. This relationship needs to be further characterized in a larger cohort.