Philadelphia, PA -- Researchers at the University of Pennsylvania Medical Center have designed a novel test that effectively predicts a patient's risk for developing a common life-threatening heart-rhythm abnormality following coronary-artery bypass surgery (CABS). The abnormality -- known as atrial fibrillation, or AF -- occurs in approximately one-third of all bypass surgery patients, and is associated with an increased risk of stroke, as well as an increase in the length and cost of hospitalization. According to the test's designers, pre-surgical identification of high-risk AF patients can be used by physicians to treat those patients prophylactically with anti-arrhythmic medications. The Penn investigators will report their findings today at the annual conference of the North American Society of Pacing and Electrophysiology (NASPE), being held in San Diego, California.
The test, called the "Prediction Rule," is a mathematically-derived assessment of post-operative AF risk based on a patient's age plus two pre-surgical clinical factors. The clinical factors -- both of which are exacting measurements of electrical-impulse activity within the heart muscle -- can be extrapolated from the results of a patient's diagnostic electrocardiogram, commonly known as an EKG. The electrical-impulse data include a PR interval measurement, which notes the time it takes an electrical impulse to travel from the top chambers of the heart to the bottom ones; and a P-wave duration, which identifies the time required for an impulse to move between the two upper chambers. Basically, the longer the travel time, the greater the risk.
"We determined that patients who are older than 65 and have specific elevated travel-time factors have a 74% chance of developing post-operative atrial fibrillation," notes lead author Rod S. Passman, MD, a fellow in the Division of Cardiology at the University of Pennsylvania Medical Cancer. "These high-risk patients should be considered for treatment prophylactically to prevent the onset of atrial fibrillation after open-heart surgery." On the other hand, Passman and his colleagues found that patients with no risk factors -- i.e., those under age 65 with low-level impulse travel-time factors -- have only a 12% chance of suffering AF post-surgically.
"Because of their side effects, anti-arrhythmic medications should not be given to all patients before surgery," explains Passman, who also holds a fellowship appointment in Penn's Center for Clinical Epidemiology and Biostatistics. "Instead, they should be given only to those patients who really need them -- which means those deemed at-risk of developing AF."
In addition to the test's clear clinical benefit to patients, the test is useful for managing healthcare costs. According to Passman, the development of AF post-surgically increases a patient's length-of-stay in the hospital by an average of two days -- which can add anywhere from $2,000 to $10,000 to the hospital bill.
The inexpensive, non-invasive test was developed from a retrospective study of the EKG-test results from 152 patients who received CABG surgery at the Hospital of the University of Pennsylvania in 1996. "Although we believe we've designed a useful tool for risk-stratifying patients for post-operative AF, more research needs to be done to assess the overall clinical effectiveness of our test," adds Passman. "Meanwhile, I predict that our test, or a similar predictive model, will eventually become a standard-of-care component in managing CABG patients in the future."
Co-authors of the Penn study included John F. Beshai, MD, Marc A. Scheiner, MD, Behzad B. Pavri, MD, Luis Siejo, MD, Eric Grubman, MD, and Stephen E. Kimmel, MD.