An increase in troponin or creatine kinase-MB, even slight, during the first three days after major vascular surgery predicts lower survival rates in both short and long term, according to an article in the November 5th issue of the Journal of the American College of Cardiology.

"Even minor troponin elevation, below the conventional cut-off levels usually used to define heart attacks, significantly predicts long-term mortality. CK-MB also predicts long-term survival, independent of the cardiac troponin," said Giora Landesberg, MD, lead author of the study.

"In cases of post-surgical patients, in whom skeletal muscle is almost always damaged by the surgical intervention itself, there is even greater importance to differentiate between skeletal muscle injury and myocardial injury, which is equivalent to myocardial infarction, in particular if the myocardial infarct is otherwise silent, that is, without clinical signs or symptoms," Landesberg noted.

The Israeli researchers studied 447 consecutive patients who underwent 501 major vascular procedures. During the first three postoperative days, patients were continuously monitored with 12-lead electrocardiogram monitoring and their cardiac troponin-I, cardiac troponin-T (or both troponins), and creatine kinase-MB levels were recorded. During a follow-up period of up to five years (average follow-up, 32.3 months), an elevated troponin or creatine kinase-MB level was associated with higher death rates, even when low cutoff levels were used. In addition, the researchers reported that most of the patients with elevated biochemical marker levels did not show obvious clinical signs of acute myocardial infarction during the postoperative period.

"These markers are indicative of myocardial ischemia and myocardial damage. The mechanism of linkage with long-term mortality may be double: 1) postoperative infarction itself may lead to reduced left ventricular function and myocardial reserve; 2) postoperative ischemia and myocardial damage reflect worse coronary artery disease and therefore greater likelihood for additional cardiac events in the future," Landesberg said.

Landesberg added that troponin measurements could become an important addition to postoperative monitoring of patients, helping to guide treatment including possible use of beta-blocker therapy: "I personally believe in routine surveillance of both electrocardiogram monitoring for ischemia and daily troponin measurements in high-risk vascular patients. However, the cost-effectiveness of such an approach has not been proven yet. Therefore much clinical judgment and sensitivity must be applied by the treating physicians to the most at-risk patients."

In an editorial, Allan S. Jaffe, MD, wrote that the study by Landesberg et al. is "a large baby step in the right direction. It documents that patients with troponin increases after vascular surgery are at increased risk for subsequent events. It remains to be seen if those events can be prevented but it may be that they can."

Jaffe also noted that the study findings help support the use of troponin levels to define when a myocardial infarction has occurred. Both the European Society of Cardiology and the American College of Cardiology have moved to a troponin standard in recent years. Jaffe is a consultant to some companies that make troponin tests.

Thomas H. Lee, MD, who was not connected to the study, said physicians should heed the warnings of biochemical marker elevations: "This study has direct and important implications for physicians who care for patients undergoing vascular surgery. No one should feel comfortable dismissing troponin or creatine kinase-MB elevations of this magnitude as one-time events that were provoked by the stress of surgery. They are important warning signs that patients have a high risk of future complications. These patients deserve aggressive risk factor reduction, consideration of noninvasive testing for risk stratification, and close follow-up."