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Rapid Fire Abstracts

Rapid Fire 07- Heart Failure II

Non-invasive CMR oximetry for quantification of myocardial oxygen consumption in heart failure with reduced ejection fraction(HFrEF) patients (RF_FR_367)

Friday, January 31, 2025
1:30 PM – 1:40 PM East Coast USA Time
Location: Blue Room PreFunction
Background: Heart failure (HF) is the leading cause of hospitalization among Medicare beneficiaries1. As survival rates from acute myocardial infarction (MI) improve, post-myocardial infarction chronic heart failure has become a significant contributor to the growing HF prevalence2. A failing heart is energy-starving, and early detection of cardiac metabolism abnormalities can facilitate patient management. Recently, our team developed a free-running high-resolution cardiac blood oximetry sequence that noninvasively quantifies myocardial oxygen consumption (MVO₂) and myocardial exertional efficiency (MEE) without special MRI hardware and exogenous contrast agents. This study aims to evaluate the ability of this technique to detect impaired myocardial metabolism in patients with heart failure and reduced ejection fraction (HFrEF) resulting from chronic MI.

Methods: A prospective study was conducted under IRB approval. Patients were included in the disease group if they had a history of MI complicated with LV EF≤ 40% and a history of symptomatic HF (NYHA functional class II or greater). Volunteers were included in the control group by excluding any known cardiovascular diseases. A 2D cine phase contrast gradient echo sequence with retrospective cardiac gating was used for the through-plan coronary sinus (CS) flow imaging acquisition. Whole-heart 2D cine short-axis images covering the left ventricle (LV) were used to analyze the LV mass, ejection fraction (EF), cardiac output (CO), and stroke volume (SV). Mean blood pressure (MBP) and heart rate (HR) were collected during the scan. CS flow, LV mass, and LV function were measured by Cvi42 (Circle Cardiovascular Imaging Inc., Calgary, Canada). A recently developed high-resolution, non-ECG gated, and free-breathing T2-based MR oximetry sequence was utilized to measure blood oxygen saturation (SbO2) levels in the CS and LV. The arterial-venous oxygen difference (a-vΔSbO2) was calculated by subtracting the SbO2 levels between LVand CS. MVO2 was calculated (MVO2=1.39 x hemoglobin x ΔSbO2 x MBF). MEE was calculated using the equation of [cardiac output (CO = SV x HR) x MBP x 1.33 x 10-4 / (LV mass x MVO2 x 20)] x100. Continuous variables between the two groups were compared using the Mann-Whitney U test.

Results: Representative images of a patient and a healthy volunteer in Fig. 1 show measured SbO₂ in CS and LV. Table 1 summarizes the physiological parameters of the study subjects. CO, SV, and EF were significantly lower in the disease group compared to the control group, while LV mass was significantly higher in the failing hearts (all Ps < 0.05). Oxygenation-sensitive parameters are further compared in Fig. 2. While not statistically significant, whole-heart MVO₂ was higher in the disease group (7.16±2.22 mL/min) compared to controls (6.60±3.89 mL/min, P=0.304, Fig. 2A). MVO₂ per gram of myocardium (MVO₂/g) was reduced following LV remodeling (Diseased=0.06±0.04 mL/g/min vs. Control= 0.11±0.05 mL/g/min, P=0.289, Fig. 2B). Importantly, MEE was significantly reduced in the disease group compared to the control group (20.01±4.90vs.50.72±23.56, P=0.039, Fig. 2C).

Conclusion: Noninvasive coronary sinus CMR oximetry allows for the quantitative assessment of myocardial oxygen metabolism and myocardial efficiency in HFrEF patients. It has the potential to serve as a biomarker for myocardial aerobic metabolism in various heart diseases.