Blog | Friday, September 23, 2011

QD: News Every Day--No evidence for ECG screening in low-risk patients

Electrocardiograms (ECG) aren't effective as a general screening tool in low-risk patients, despite their prevalent use, according to updated recommendations from the U.S. Preventive Services Task Force (USPSTF).

While some cardiac abnormalities found on resting or exercise ECG were independent predictors of future cardiovascular events, there's still no evidence that ECG findings better classified patients into meaningful risk groups than did traditional risk factor assessments. No studies have compared clinical outcomes or use of risk-reducing therapies between persons who did and did not receive screening.

The USPSTF updated recommendations from 2004, this time around, focusing on studies that adjusted for traditional cardiovascular risk factors, performed meta-analyses, and evaluated whether screening with ECG in improved risk reclassification. Their findings appeared in the Sept. 20 issue of the Annals of Internal Medicine.

The Task Force reviewed 63 prospective cohort studies that evaluated the clinical significance of abnormalities found by resting or exercise ECG. Abnormalities on resting ECG (ST-segment or T-wave abnormalities, left ventricular hypertrophy, bundle branch block, or left-axis deviation) or exercise ECG (ST-segment depression with exercise, chronotropic incompetence, abnormal heart rate recovery, or decreased exercise capacity) were associated with increased risk (pooled hazard ratio estimates, 1.4 to 2.1).

But, no randomized, controlled trials or prospective cohort study evaluated clinical outcomes or use of risk-reducing therapies after screening versus no screening, nor did any study estimate how accurately resting or exercise electrocardiography classified participants into high-, intermediate-, or low-risk groups. No studies evaluated how screening affects use of lipid-lowering therapy or aspirin.

Evidence on harms was limited, but direct harms seemed minimal (for resting ECG) or small (for exercise ECG), the researchers wrote. There were no direct studies on the harms found from testing or from follow-up testing, although researchers noted the general estimated complications associated with angiography or revascularization procedures (rates of angiography after exercise ECG ranged from 0.6% to 2.9%), as well as the possible cancer risks of exposure to coronary angiography, computed tomography angiography, and myocardial perfusion imaging.

ACP Member Michael S. Lauer, MD, of the National Heart, Lung, and Blood Institute, told Reuters that, "There's a general belief that prediction means prevention. But we see, over and over again, that this is not necessarily true."

If an electrocardiogram isn't in your immediate future, you could consider this as a preventive measure, albeit one that the U.S. Preventive Services Task Force hasn't considered. As Sean Khozin, MD, points out, this is the shirt you want to wear if you ever need CPR.