Inhaled Beta-adrenergic Agonists to Treat Pulmonary Vascular Disease in Heart Failure With Preserved EF (BEAT HFpEF): A Randomized Controlled Trial

Overview

The enormous and rapidly growing burden of Heart Failure with Preserved Ejection Fraction (HFpEF) has led to a need to understand the pathogenesis and treatment options for this morbid disease. Recent research from the investigator's group and others have shown that pulmonary hypertension (PH) is highly prevalent in HFpEF, and right ventricular (RV) dysfunction is present in both early and advanced stages of HFpEF. These abnormalities in the RV and pulmonary vasculature are coupled with limitations in pulmonary vasodilation during exercise. There are no therapies directly targeted at the pulmonary vasculature that have been clearly shown to be effective in HFpEF. A recent study by Mayo Clinic Investigators has demonstrated pulmonary vasodilation with dobutamine (a beta 2 agonist) in HFpEF. As an intravenous therapy, this is not feasible for outpatient use. In the proposed randomized, placebo-controlled double blinded trial, the investigators seek to evaluate whether the commonly used inhaled bronchodilator albuterol (a beta 2 agonist), administered through a high-efficiency nebulizer device that achieves true alveolar drug delivery, improves pulmonary vascular resistance (PVR) at rest and during exercise in patients with HFpEF as compared to placebo. This has the potential to lead to a simple cost effective intervention to improve symptoms in HFpEF, and potentially be tested in other World Health Organization (WHO) Pulmonary Hypertension groups. PVR is an excellent surrogate marker for pulmonary vasodilation and has been used in previous early trials of PH therapy.

Preliminary studies to support feasibility: Recent research from the investigator's group has shown that right ventricular (RV) dysfunction is present in a third of patients with HFpEF and the presence of pulmonary vascular disease and pulmonary hypertension (PH) is very high (related to both pulmonary venous hypertension as well as pulmonary vascular disease). Both of these have been associated with adverse outcomes and exercise intolerance but no therapy is currently available directly targeted at the pulmonary vasculature in HFpEF. The investigators recently demonstrated significant improvements in pulmonary vascular function with dobutamine (a β2 agonist) administered acutely in HFpEF. As an intravenous therapy, this is not suitable for chronic outpatient use. Hospitalized patients with heart failure often demonstrate symptomatic improvement with inhaled β2 agonist therapy, even in the absence of pulmonary disease, and animal studies have also shown improved resolution of pulmonary edema with albuterol. In the proposed randomized, double blinded placebo-controlled trial, the investigators seek to evaluate whether the commonly used inhaled bronchodilator albuterol, administered through a high-efficiency nebulizer device, improves pulmonary vascular function in patients with HFpEF-PH as compared to placebo. This has the potential to lead to a simple cost effective intervention to improve symptoms in HFpEF-PH, and potentially be tested in other WHO PH groups. In the absence of frank signs of congestive heart failure, patients with early HFpEF can only be reliably diagnosed by exercise right heart catheterization, which is routinely performed at Mayo Clinic as part of the evaluation of patients with unexplained dyspnea. The presence of elevated pulmonary capillary wedge pressures (PCWP) at rest (\>15 mmHg) or with exercise (\>25 mmHg); and elevated mean pulmonary artery pressures at rest (\>25 mm Hg) and with exercise (\>40 mmHg) has been used to invasively diagnose HFpEF with exercise pulmonary hypertension with a high degree of validity and reliability. Just as exercise stress unmasks abnormalities in left ventricular (LV) diastolic function in early stage HFpEF, the investigators have very recently shown that exercise stress reveals early abnormalities in pulmonary artery vascular function as compared to controls without HF that are not apparent from resting data alone. Using objective diagnoses of HFpEF and exercise induced PH, the investigators seek to evaluate the hemodynamic changes with exercise in pulmonary vascular resistance, peak cardiac output and subjective dyspnea before and after inhaled albuterol therapy for pulmonary vasodilation. Study design: This study will be performed in a randomized, double blind placebo-controlled fashion using inhaled albuterol or inhaled saline (prepared by research pharmacy) administered through a novel high-efficiency nebulizer in a 1:1 fashion. Patients will undergo right heart catheterization (RHC) with expired-gas analysis using high Fidelity micromanometer catheters at rest and with exercise, at baseline and following treatment with study drug, using a novel study design that the investigators have previously utilized and reported. Rest and exercise measurements will be repeated after receiving inhaled albuterol or control therapy. Patients referred to the cardiac catheterization laboratory for invasive exercise stress testing will be prospectively recruited. Standard RHC using high fidelity micromanometers (Millar Instruments) will be performed at rest and during supine exercise with simultaneous expired gas analysis (MedGraphics) as is our current practice. The protocol is rest-20 Watts exercise x 5 minutes, and then graded workload increases in 10-20 Watt increments (3 minute stages) to exhaustion. Hemodynamic, arterial and mixed venous blood gas and expired gas data are acquired at rest, during each exercise stage and at peak exercise. Venous blood samples will be obtained at rest and at peak exercise. Perceived symptoms of dyspnea and fatigue will be quantified using the Borg dyspnea and effort scores at each stage of exercise. Limited echocardiography will be performed by a cardiologist skilled in imaging focused on measures of RV morphology and function. After the initial exercise study and hemodynamics have returned to baseline, study drug (normal saline placebo or albuterol 2.5 mg) will be inhaled through a high efficiency nebulizer over 5 minutes. After a 10 minute observation period, resting hemodynamic and expired gas data will be acquired exactly as in the initial run. Subjects will then repeat the 20 Watt x 5 minutes exercise phase. Subjects will repeat exercise only at the 20 Watt stage, rather repeating the entire study. This is done to increase the feasibility and shorten the time of the case. The investigators have previously observed that the vast majority (\>85%) of the elevation in cardiac filling pressures and reduction in venous oxygen content in people with HFpEF occurs at the low 20 Watt workload, so repeating exercise hemodynamic assessment at this load should be sufficient to detect any clinically meaningful treatment effect from albuterol.