Renal Dysfunction Adds to TIMI Score
The TIMI risk score is a validated risk-assessment tool used to predict outcomes in patients with unstable angina or non-ST-segment elevation MI (UA/NSTEMI). It was derived from clinical trial cohorts, however, that excluded patients with renal dysfunction, even though renal dysfunction has proven to be an independent risk predictor for adverse cardiovascular events in clinical trials and community-based studies.
“The TIMI score has some inherent limitations and may be less accurate in real-world settings,” said principal investigator Jason Go, MD, of Creighton University Medical Center, in Omaha. “The addition of renal status improves the accuracy of the TIMI score without detracting from its ease of use and simplicity.”
The study defined renal dysfunction as creatinine clearance less than 45 mL/min. The presence of renal dysfunction added one risk factor in the model revised by the investigators, so that the total number of possible points in a patient's TIMI risk score was 8.
Data for the study was obtained from a retrospective analysis of 798 consecutive patients admitted with UA/NSTEMI. The primary end point was cardiovascular death, MI, or persistent ischemia requiring urgent revascularization.
Both the classic seven-point TIMI score and the eight-point TIMI score correlated well with clinical events. A TIMI score of 8, however, was associated with almost double the incidence of the primary end point compared with a TIMI score of 7 and improved upon the predictive power of the TIMI score, Dr. Go reported.
Furthermore, the presence of renal dysfunction was associated with a near threefold increase in adverse outcomes and in fact, had a greater impact than to the other TIMI risk variables, he added.
The analysis also demonstrated the strong impact of renal dysfunction on revascularization procedures. Patients with renal dysfunction were significantly less likely to undergo angioplasty (60% vs. 40%), coronary artery bypass surgery (14.3% vs. 10.7%), or any form of intervention (53.5% vs. 37.3%).
In a comparison of the composite event rates for death or MI between patients with and without renal dysfunction stratified by revascularization status, renal dysfunction continued to be an independent predictor of adverse outcomes.
“Renal dysfunction is associated with fewer revascularization procedures being performed and its impact on adverse outcomes remains, despite revascularization,” Dr. Go noted.
The clinical implications of the findings are that including renal status in the TIMI risk factors can enhance the identification of patients at higher risk for death, MI, or ischemia requiring urgent revascularization, compared with predictions based on the classic seven-point TIMI variables alone.
James Ferguson, MD, a cardiologist formerly with the Texas Heart Institute in Houston and now vice president at The Medicines Company in Parsippany, N.J., commented to Renal & Urology News that “renal dysfunction is huge” in the setting of coronary artery disease and is an “important risk stratifier in virtually every patient.”
“Adding renal function status to TIMI risk makes a huge difference,” he observed. “It is as good as, or better than, any other factor you will find in a patient.”
Dr. Ferguson pointed out that while physicians do understand the importance of renal status, they “don't normally go to the trouble of calculating creatinine clearance.”
“Physicians look at creatinine, not creatinine clearance, as telling them all about renal function. They miss a lot of renal dysfunction because they assume that a creatinine of 1 mg/dL is fine, but in the elderly patient, for example, this may indicate significant renal dysfunction. Physicians need to do a better job of assessing renal function as a risk factor.”