A routine cardiac MRI scan may be comparable to right heart catheterization for determining the severity of heart failure, according to a study in JACC: Advances.

Researchers in England developed a method that uses a routine type of MRI measurement called T2 mapping to estimate mixed venous oxygen saturation (SvO₂), a key indicator of heart health that measures how much oxygen is left in the blood as it returns to the heart.

The team tested the technique in 30 patients and found that the MRI-derived estimates of SvO₂ closely matched those obtained through right heart catheterization, a safe but invasive procedure that is standard for assessing hemodynamics in heart failure. 

The researchers then analyzed people with newly diagnosed heart failure, following them for around 3 years. Those with healthier oxygen readings on MRI were significantly less likely to die or be hospitalized due to their condition. The MRI-based measurement remained accurate after controlling for age, other illnesses, and overall heart function.

“It was a really strong endpoint, completely independent of ejection fraction and all the traditional markers of risk in heart failure,” said senior author Peter Swoboda, PhD, a cardiologist at the University of Leeds in Leeds, England. “So I think it could be rolled out clinically very easily.”

‘Scalable and Generalizable’

T2 mapping is a standard MRI sequence, but it is not usually done for patients with heart failure, Swoboda said. However, because it only takes about 10 seconds to complete, including T2 mapping would have a negligible impact on an MRI session that usually lasts 45 minutes to an hour.

“It’s one of those interventions that is easily scalable and generalizable,” Swoboda said. “We already do a lot of cardiac MRI, and it is growing. If we add T2 mapping to the standard scan, there may be no need for right heart catheterization.”

The technique still needs to be evaluated with prospective, randomized trials using different scanners and populations, Swoboda said.

Srihari S. Naidu, MD, director of Cardiac Catheterization Labs at Westchester Medical Center and president of the Society for Cardiovascular Angiography & Interventions, said the study was an interesting use of imaging (which usually only looks at the structure of the heart) to measure its function as well.

Questions About T2 Mapping

But Naidu pointed out that the correlation between the MRI- and catheter-derived measurements of SvO₂ could differ by up to 15% in either direction in some patients. “It’s not as precise as what you get from right heart catheterization,” said Naidu, who was not involved in the study. 

He also noted that right heart catheterization measures several other factors besides SvO₂ to paint a more detailed picture of the heart and what interventions might help. For example, catheterization can identify cases of a problem in the lungs, rather than the heart, due to conditions such as chronic obstructive pulmonary disease. “Going down the pathway of trying to fix the heart makes no sense when it’s a lung problem,” he said.

Naidu said the MRI-derived measurements could serve as a useful early warning system to help identify patients who need further interventions or a referral for transplant.

“Once you have imaging of the heart, you can get a relatively loose guide of its overall functional status that can serve as a guide to stratify which patients are at higher risk of heart failure hospitalization,” he said. “That can trigger when we should be concerned and send patients for further evaluation.”

Swoboda and Naidu reported no relevant financial relationships.

Brian Owens is a freelance journalist based in New Brunswick, Canada.