Pulmonary Hypertension And Exercise Intolerance: A Novel Use Of Cardiomems To Measure Hemodynamic Changes In Exercise

Abstract

Pulmonary hypertension (PH) occurs in up to 80% of heart failure (HF) patients and is associated with exercise intolerance and mortality. CardioMEMs is a wireless hemodynamic pulmonary artery pressure (PAP) sensor that reduces HF hospitalizations in highly symptomatic patients. Six minute walk test distance (6MWTD) correlates well with mortality and hospitalizations in HF patients. We sought to identify hemodynamic variables that are predictive of 6MWTD in HF patients with a CardioMEMS device. Patients were recruited from 7 sites from 5/2019 to 2/2021. PAP was measured in the supine and seated position at rest and in the seated position post-exercise. Baseline characteristics were summarized as means and standard deviations for continuous variables and as frequencies and percentages for categorical variables. Associations between variables were tested in independent, univariable linear regression models. Due to multiple testing, false discovery rate p-value corrections were applied. Sixty-six patients with a mean age of 70±12 were enrolled. The majority were male (67%), NYHA class III (61%), with an EF < 50% (53%). Mean 6MWTD was 277±95 meters. Mean resting supine PAPs were PASP 36±17 mmHg, PADP 16±9 mmHg, and mPAP 24±12 mmHg. Mean resting seated PAPs were PASP 31±15 mmHg, PADP 13±8 mmHg, and mPAP 20±11 mmHg. Mean seated, post exercise PAPs were PASP 37±19 mmHg, PADP 15±10 mmHg, and mPAP 24±13 mmHg. Mean increases after exercise were PASP 6±11 mmHg, PADP 2±6 mmHg and mPAP 4±8 mmHg. Of the variables tested, none were predictive of 6MWTD. Furthermore, the mean PAP difference of 6 mmHg before and after exercise is low compared to prior studies. Given the less controlled and self-paced nature of the 6MWT compared to other standardized exercise studies, these findings indicate that HF patients may not be functionally limited by pulmonary hypertension during 6MWT. This is supported by the minimal difference in pre and post 6MWT pressures indicating minimal augmentation of cardiac output. These findings together indicate that non-cardiac variables may play a significant role in limiting exercise tolerance. The identification and treatment of such variables may lead to increased functional capacity, and therefore improved morbidity and mortality.