NEW ORLEANS — Mortality is extraordinarily high in the year after acute MI in patients with renal failure—and the explanation may lie largely in their strikingly different clinical characteristics as compared with the general MI population.
In this regard, dialysis patients and those with non-dialysis-dependent chronic renal insufficiency look much more alike as a group, and distinctly different from acute MI patients without a history of renal impairment, Charles A. Herzog, M.D., said at the annual scientific sessions of the American Heart Association.
Dialysis patients have a “dismal” 60% 1-year mortality following acute MI, noted Dr. Herzog, a cardiologist with the U.S. Renal Data System and Minneapolis Medical Foundation.
In an effort to understand why patients with renal failure fare so poorly after an MI, he and his coinvestigators constructed a unique database by cross matching the records of the U.S. Renal Data System and the National Registry of Myocardial Infarction-3, a large Genentech-sponsored registry of MI patients. This yielded a study population consisting of 2,720 renal dialysis patients with MI; 35,950 MI patients with non-dialysis-dependent renal insufficiency; and 384,415 MI patients with no history of chronic renal disease. None of the study participants was transferred for MI care.
Many statistically and clinically significant differences were apparent between the renal patients and those in the general population. (See box.)
Among the differences that may have had the greatest bearing on the poor long-term prognosis of patients with renal disease were their lesser likelihood of presenting with chest pain, in Killip class I, or with ST-elevation MI, as well as the lower diagnostic suspicion of MI upon presentation. By ECG criteria, a much lower percentage of renal failure patients were eligible for any sort of reperfusion therapy, Dr. Herzog said.
There was no major difference between the groups in terms of prehospital delay, which averaged about 5.5 hours from symptom onset to hospital presentation, so an educational campaign aimed at increasing renal patients' awareness of MI signs and symptoms isn't likely to yield major improvements in long-term outcome, Dr. Herzog said.
In response to audience expressions of surprise that the patients with non-dialysis-dependent renal insufficiency fared as poorly post MI as patients requiring dialysis, Dr. Herzog replied that this appeared to be largely an age-driven phenomenon.
Advanced age has long been recognized as an important predictor of worse outcome after an MI, he noted, and in this study the non-dialysis-dependent renal patients were significantly older than the other two groups, with a mean age of 75 years, compared with 68 years in the dialysis patients and 69 years in MI patients without renal disease.