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DALLAS -- CT imaging of coronary calcification by electron beam or multidetector devices is appropriate for patients at an intermediate risk, according to an American Heart Association statement. It represents an about face for the organization.
DALLAS, Oct. 12 -- CT imaging of coronary calcification by electron beam or multidetector devices is appropriate for patients at an intermediate risk, according to an American Heart Association statement. It represents an about face for the organization.
The AHA maintained its position that imaging plaque calcification may not give additional useful information about patients known to be at high or low coronary risk. But the statement acknowledged that EBCT imaging may be helpful in making the difficult treatment decisions for the millions of intermediate-risk patients, defined as having a 10% to 20% 10-year Framingham risk score.
"If you know they are high risk, it's easy -- they get treated," said Matthew J. Budoff, M.D., of the Harbor-University of California Los Angeles Medical Center. "If they are low risk, it's easy -- you just tell them to stay healthy But it's all those people in the middle where guidelines tend to fall out. This is where coronary artery calcification is going to play a huge role."
For these patients, "elevated calcium scores may trigger more vigorous application of both lifestyle and/or pharmacological therapies targeted to lower cardiovascular risk," Dr. Budoff and colleagues wrote in the Oct. 17 issue of Circulation, Journal of the American heart Association.
The AHA statement cited rapidly evolving technology and literature for its change of heart regarding EBCT and multidetector CT (MDCT). The AHA's prior statements in 1994 and 2000 acknowledged CT's potential but because of conflicting data did not recommend routine scanning. Yet by 2005 the AHA had given CT the partial go-ahead in a statement targeted at women.
"I think this definitely represents a recognition that the science is getting better in this regard," Dr. Budoff said.
EBCT is a fast x-ray imaging modality that can detect and measure calcium deposits in the coronary arteries. MDCT, also called multirow or multislice CT, is more commonly available.
The recommendations suggested that cardiac CT in asymptomatic patients has:
Because calcified plaque can be present in nonobstructive coronary plaque lesions but is not highly specific for obstructive lesions, a positive finding in asymptomatic patients "does not provide a rationale for revascularization but rather for risk factor modification and possible further functional assessment," the authors wrote.
"Clinicians must understand that a positive calcium scan indicates atherosclerosis but most often no significant stenosis," they added.
The recommendations said that cardiac CT in symptomatic patients is:
Noninvasive CT angiography performed by either EBCT or MDCT "may develop into a clinically useful tool" to evaluate the lumen and wall of the coronary artery, especially in the context of ruling out stenosis in patients with low to intermediate likelihood of disease. The recommendations said that CT coronary angiography is:
Though the clinical relevance of the radiation dose from cardiac CT remains unknown, higher radiation doses are generally associated with a small increase in cancer risk.
Other recommendations included:
For coronary artery calcified plaque assessment, the authors "strongly" recommended using a low radiation-dose cardiac CT technique with prospective cardiac gating (starting data acquisition based on a signal from the electrocardiogram to avoid blurring of the image as the heart pumps). MDCT may be preferable for larger patients since EBCT's lower power may cause image quality to suffer from noise, the authors noted.
The statement acknowledged that "EBCT is one of many contenders in a crowded field of emerging [coronary artery disease] risk-assessment tools," such as carotid intima-media thickness and blood tests like homocysteine and C-reactive protein.
It also noted that there is not evidence that screening with EBCT improves clinical outcomes by reducing mortality or morbidity from coronary artery disease.
The recommendations came out just ahead of the American College of Cardiology's appropriateness statement on the same topic and within a month of the expected November arrival of the ACC's similar guidelines.
The authors disclosed various conflicts with companies including: Merck, Pfizer, Wyeth, AstraZeneca, KOS, General Electric, Siemens Medical Systems, Novartis, and Toshiba.