New Function of Nuclear Stress Test

When the left heart chamber, or ventricle, fails to properly fill with blood because it is stiff and unable to relax, this is called diastolic dysfunction. When it occurs, the left side of the heart pumps too little blood while the right side continues to pump normally, and the lungs fill up with blood. By using the nuclear stress test to look at how fast blood flows into the heart's pumping chamber, the scientists can determine if a patient's left ventricle is having trouble.

During a nuclear stress test, radioactive thallium is injected into the bloodstream. Scans are taken shortly after an exercise test to show blood flow when the heart is stressed and two or three hours later to show blood flow during rest. "This test is usually used to identify blockages in the heart," Doctor Dineshkumar Patel of the research team explains. "But we have demonstrated that it also shows the left ventricle filling pressure."

The scientists looked at 52 consecutive patients who underwent cardiac catheterisation, a more invasive test to diagnose diastolic dysfunction, within 15 days of a nuclear stress test to test the efficacy in diagnosing diastolic dysfunction. They compared the diastolic filling pressure from catheterisation and from the nuclear stress test and found that the latter had a 94 percent specificity in detecting diastolic dysfunction.

The nuclear stress test plots out a heartbeat in 16 frames, and that represents the diastolic filling curve at 16 points, the scientists explain. The slope of the filling portion of the curve is a representation of the left ventricle filling pressure used as a marker of diastolic dysfunction.

Previously, the nuclear stress test was only detecting diastolic dysfunction in patients who were already sick, whose hearts were weak and barely pumping. That means, the test only picked up those who had both diastolic and systolic dysfunction, the researchers sum up. Now, they can use the diastolic filling curve to diagnose patients with diastolic dysfunction who have normally squeezing hearts.; Source: Medical College of Georgia