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Exercise-Stress CMR Imaging for HFpEF
Quick Take
- In this study of 68 patients, real-time exercise CMR, including assessment of LA function, shows promise as a means of noninvasively identifying patients with HFpEF.
Study Questions:
Can exercise cardiac magnetic resonance (CMR) identify patients with heart failure with preserved ejection fraction (HFpEF), using exercise right heart catheterization (RHC) as the diagnostic standard?
Methods:
The HFpEF Stress Trial was a single-center German study that recruited patients with exertional dyspnea (New York Heart Association class ≥II) and echocardiographic evidence of left ventricular (LV) diastolic dysfunction (E/e’ ≥8) and LVEF fraction ≥50%. Key exclusion criteria were: contraindications to CMR (such as an implanted cardiac device or allergy to gadolinium-based contrast), abnormal pulmonary function tests, nonsinus rhythm at the time of testing, moderate to severe valvular disease, and evidence of coronary artery disease. Patients underwent RHC at rest and during supine bicycle exercise. The CMR protocol included assessment of biventricular EF and strain, as well as evaluation of atrial function, tissue characterization with T1 mapping and late gadolinium enhancement imaging, and real-time, free-breathing imaging during exercise on a supine CMR-compatible ergometer. HFpEF was defined as pulmonary capillary wedge pressure ≥15 mm Hg at rest or ≥25 mm Hg during exercise.
Results:
The cohort of 68 patients was divided into HFpEF and noncardiac dyspnea groups, with 34 patients in each group. HFpEF patients were older (median age 69 vs. 66 years, p = 0.034), more commonly had a history of atrial fibrillation (47% vs. 15%, p = 0.004), and had higher N-terminal B-type natriuretic peptide levels (median 255 vs. 75, p < 0.001). Cardiac index values at rest were similar in the two groups (median 2.9 L/min/m2), but during exercise, the HFpEF group had lower values (median 5.2 vs. 5.8 L/min/m2, p = 0.022). Rest CMR yielded similar results for LVEF and global longitudinal strain, as well as myocardial T1 mapping, between the two groups, but left atrial (LA) reservoir, conduit, and booster pump function were higher in the noncardiac dyspnea group (p < 0.001 for all). Comparing stress CMR to rest CMR, the noncardiac dyspnea group exhibited increased LA EF (median 44.9% vs. 39.9%, p < 0.001), while the HFpEF group did not (median 32.2% vs. 34.2%, p = 0.142). LA long-axis strain was independently associated with HFpEF. LA long-axis strain was the best predictor of HFpEF, with areas under the curve (AUCs) of 0.82 at rest and 0.93 at stress (p = 0.029 for difference), compared with 0.55 for LV long-axis strain at rest and 0.76 for LV long-axis strain at stress.
Conclusions:
Real-time exercise CMR, including assessment of LA function, shows promise as a means of noninvasively identifying patients with HFpEF.
Perspective:
These findings emphasize the role of the left atrium in augmenting cardiac output during exercise. Multicenter studies will be needed to corroborate these results. Real-life barriers to exercise CMR may include obesity or excessive abdominal girth, claustrophobia (which can be overcome with sedation for rest CMR but not for exercise studies), and orthopedic problems precluding bicycle exercise.
Clinical Topics: Arrhythmias and Clinical EP, Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Atherosclerotic Disease (CAD/PAD), Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Exercise
Keywords: Atrial Fibrillation, Cardiac Catheterization, Contrast Media, Coronary Artery Disease, Diagnostic Imaging, Dyspnea, Echocardiography, Exercise, Gadolinium, Heart Failure, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Natriuretic Peptide, Brain, Respiratory Function Tests, Stroke Volume, Ventricular Dysfunction, Left
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