Heart Scans Disclose Truths About Future Risk
Better than Cholesterol Tests, Scans Show the Big Picture
Tuesday, August 26, 2003
Many individuals believe that if their cholesterol drops, they are less vulnerable to a heart attack. But a University of Rochester pilot study confirms that monitoring patients with a standard heart imaging scan can explain why some patients with normal cholesterol are still at high risk for serious heart problems.
The study was published in the current issue of the Journal of the American College of Cardiology. Of 23 patients who took the well-known cholesterol drug pravastatin, all lowered their total cholesterol in about six weeks. However, even with a lipid profile that met national risk guidelines, the heart function of many patients did not improve until six months later – and in two patients it actually worsened, the imaging scans showed.
The research underscores the need to look beyond routine blood cholesterol tests as the most reliable way to predict heart disease, the nation’s leading killer, says lead author Ronald Schwartz, M.D., director of Nuclear Cardiology at Strong Memorial Hospital and an associate professor of Medicine and Radiology.
“If I’m spending $1,500 a year on cholesterol medication, I’d want to know if it’s actually working to prevent a heart attack or other serious coronary problem,” Schwartz says. “Individuals vary greatly in their response to medication, and we found that improvement in cholesterol doesn’t always correlate with improved heart function.”
The drug company Bristol Meyers Squibb, which makes pravastatin, funded the research. The study focused on the value of a common noninvasive test called a thallium stress test, to measure a patient’s response to the drug. The test is administered in conjunction with an imaging technique called single photon emission computed tomography, (SPECT), or myocardial perfusion imaging (MPI). A patient either walks on a treadmill or rests after a slightly radioactive tracing solution has been injected into a vein. The tracer emits a signal that amplifies small changes in blood flow in and around the heart muscle. A camera picks up three-dimensional images of the heart, allowing doctors to view on a computer screen blood-flow changes that may be indicative of heart disease.
Schwartz says the imaging tests (average price: $1,200) are cost effective, as they help sort out the complexities of heart disease. For example, if a SPECT test identifies a patient as having a low risk of a future heart attack, it will have saved that patient money on costly medications, when he or she could safely make healthy lifestyle changes. Conversely, the imaging scans help inform high-risk patients whether they are responding to existing medications and what other treatments may work best for them.
An accompanying journal editorial by Johns Hopkins University physicians agrees that as more Americans use cholesterol drugs, more investigation is needed to understand why people respond differently and exactly how the medications exert their benefits. The editorial calls for larger studies of how imaging tests can predict heart attacks.