Article Abstract

Integrated use of cardiac MRI and the CardioMEMS™ HF system in PAH: the utility of coincident pressure and volume in RV failure—the NHLBI-VITA trial

Authors: Robert W. W. Biederman, Mark Doyle, Priscilla Correa-Jaque, Geetha Rayarao, Raymond L. Benza


Background: This study aims to study the feasibility and safety of measuring volumetric and pressure parameters noninvasively using simultaneous cardiovascular magnetic resonance (cMR) volumetric data and time-resolved pressure waveforms from previously implanted CardioMEMS devices in pulmonary arterial hypertension (PAH) patients. Opportunities to intervene during clinically occult phases in PAH promise to herald a key transformation in our current practice for treating this complex population. Currently, it is possible and convenient to monitor daily pulmonary arterial (PA) pressures in PAH patients using the CardioMEMS device to determine clinically silent progression. Supplementation of these pressures with other prognostic measurements of right ventricular (RV) contractility, PA resistance and RV/PA coupling could add further predictive capabilities.
Methods: PAH patients (n=17) with New York Hospital Association (NYHA) class III or IV heart failure (HF) and recent HF related hospitalizations were implanted with the CardioMEMS device as part of a NHLBI sponsored Trial. Implanted patients were then assessed using cMR imaging of the right ventricle (RV) along with measurement of pulmonary artery flow. Patients were imaged at one-month post implant (baseline) and at 4-month follow-up time (n=12). At baseline, patients were studied at rest and then under three different physiologic conditions: inhaled nitric oxide (INO), dobutamine (Dob) stress and volumetric stress (Vol), using a multiple slice short-axis imaging and a rapid imaging protocol.
Results: All patients were safely imaged, with no artifacts obscuring the cMR images. RV volumes were measured successfully at rest and under each stress condition using a reduced scan approach that required calibration for each patient which achieved a correlation r2 of 0.98. Variables measured included the maximal pulmonary artery elastance (Ea), maximal RV myocardial elastance (Emax) and ventricular-vascular coupling ratio (VVC). The response to stressors was determined on a patient basis. No complications occurred during the cMRI examination.
Conclusions: It is safe and feasible to perform cMR imaging with simultaneous pulmonary artery pressure readings from the CardioMEMS device. A reduced scan approach was developed to allowed measurement of RV volumes during stress conditions. Volumetric and pressure measurements can be combined to assess fundamental myocardial properties (e.g., Emax, Ea and VVC) in PAH patients serially over time. In the future, these parameters can be tested as serial predictors of outcome and response to therapies in PAH.