Helping Heart Patients Avoid Invasive Testing to Assess Blockages
Date: October 30, 2012
Since it turns out that about 30 percent of patients undergoing angiography for chest pain do not need revascularization, cardiologist Joao Lima and his colleagues wondered if there could be a simpler, noninvasive method to accurately evaluate blockages and assess whether they are limiting perfusion to the heart.
They embarked on a prospective study involving 381 patients at 16 hospitals in eight countries to see if an ultra-fast, 320-detector CT scanner might be effective at sorting out which people with chest pain need—or don’t need—an invasive procedure such as cardiac angioplasty or bypass surgery to restore blood flow.
“The 320-detector CT scanner allowed us to see the anatomy of the blockages as well as determine whether the blockages were causing a lack of perfusion to the heart. Therefore, we were able to correctly identify the patients who needed revascularization within 30 days of their evaluation,” says Lima.
Patients in the study had traditional SPECT tests and invasive angiography. They also had two types of tests with a noninvasive 320-detector CT scanner. In the first CT test, the scanner was used to see the anatomy of vessels to assess whether and where there were blockages. That test is known as CTA, in which the “A” stands for angiography. Then, in a second CT test with the same machine, patients were given a vasodilator medication to simulate a stress test. That second test is called CTP, with the “P” standing for perfusion.
“Our ultimate goal is to have more certainty about which patients having chest pain—without evidence of a heart attack—need an invasive procedure to open an arterial blockage,” says Johns Hopkins cardiologist Richard George, a co-author of the study.
“The CTP test added significant information about the patients’ conditions and boosted our ability to identify those whose blockages were severe enough to reduce blood flow to the heart,” adds George, who developed the CTP method with Lima.
The 320-detector CT provides a complete picture of the heart by making just one revolution around the body. The researchers say the two tests combined—CTA and CTP—still produce less radiation than a scan with the 64-detector in widespread use today.
“In our study, the amount of radiation exposure to patients from the two 320-detector CT scanner tests was half the amount they received as a result of the traditional evaluation methods—the angiogram and nuclear medicine stress test combined,” says Lima.
The researchers will continue to follow the patients in the study for up to five years, looking for any heart-related events, hospital admissions, procedures or surgeries.