Oxygen is essential for the heart to function properly. Heart attacks occur when coronary arteries are blocked, depriving heart muscles of oxygen and causing them to fail. Heart failure, although less sudden, results from the heart’s reduced ability to pump blood due to insufficient oxygen consumption.
Assessing the heart’s oxygen usage is crucial for identifying heart failure and developing early-stage treatments for a condition that affects 1 in 4 Americans during their lifetime. Diagnosis can also be achieved through various methods, including blood tests, electrocardiograms, echocardiograms, stress tests, chest X-rays, CT scans, coronary angiograms, and heart muscle biopsies.
Focusing on oxygen measurement is challenging yet vital. Current tests involve inserting a catheter into the coronary sinus or using PET scans to trace radioactivity. However, new research published Wednesday in Science Translational Medicine suggests a faster, less invasive approach to measuring heart oxygen usage during a cardiac MRI.
Interest in this testing is rising, especially with promising outcomes in heart failure patients benefiting from obesity medications.
Initially tested on pigs and then on 22 heart attack patients, this new method employs a specialized MRI to assess oxygen levels without using needles, catheters, radiotracer injections, or exposing patients to radiation. It also eliminates the need for breath-holding during scans. Researchers faced challenges capturing blood oxygen levels due to imaging difficulties, signal noise, and heart movement.
The team managed to calibrate oxygen consumption in just three minutes, with their results standing up against more invasive, traditional methods. Inspired by neuroimaging techniques that track brain oxygen levels, this innovative approach was developed.
“A cardiac MRI scan is a routine clinical procedure that people can order,” said study co-author Hsin-Jung Yang. “This is a three-minute add-on, without contrast agent, without breath-holding.”
Yang and his team envisage their method as part of a comprehensive cardiac MRI that evaluates heart function and structure. During the scan, patients lie inside a tube where magnets and radio waves generate images to detect heart damage or valve disease. Oxygen usage would be one of the outputs.
Yang, an associate professor of biomedical sciences at Cedars-Sinai Medical Center and a part of the Biomedical Imaging Research Institute at Cedars-Sinai, discussed the development with STAT. The conversation has been edited for brevity and clarity.
Why is measuring oxygen so important?
The heart operates continuously, relying on oxygen and nutrients. Monitoring its oxygen use is crucial in assessing health, particularly in heart failure, diabetes, and hypertension. These conditions increase the risk of cardiometabolic diseases when the heart struggles to pump sufficient blood.
How is oxygen use estimated now?
Currently, oxygen usage is measured by inserting a catheter into the heart, a procedure not widely available. MRI machines, present in major hospitals, offer an alternative. They don’t require contrast agents, making them suitable for lower-risk populations and allowing repeated measurements for therapy monitoring.
You make it sound so easy. What were some of the challenges to overcome?
The heart’s constant movement presents technical challenges. We developed motion-insensitive or motion-resolved imaging techniques and applied a quantification model, allowing us to measure oxygenation levels. More oxygenated blood appears darker, and we have color-coded it to reflect this.
How do you hope to help people with heart failure?
There are two types of heart failure: with reduced ejection fraction (HFrEF) and with preserved ejection fraction (HFpEF). Ejection fraction measures the percentage of blood the heart pumps out of the ventricles. Below 50% is considered reduced and can cause symptoms like fatigue and difficulty climbing stairs.
The population with preserved ejection fraction is growing rapidly. Understanding and treating this condition is a priority. GLP-1 and SGLT2 drugs show promising results for HFpEF, now included in clinical guidelines for managing metabolic issues like diabetes. This inspired our research into heart metabolism.
Is anyone else exploring this question?
Another avenue is metabolite imaging. Various metabolites in mitochondria can indicate metabolic issues. A lab at Cedars-Sinai is working on this, and we’re collaborating closely.
Who are the patients you think might benefit?
Metabolic syndrome is prevalent in the country. Those with obesity, diabetes, or hypertension are key groups for early identification, where our impact could be most significant.
STAT’s coverage of chronic health issues is supported by a grant from Bloomberg Philanthropies. Our financial supporters are not involved in any decisions about our journalism.
