Letter by Xue et al Regarding Article, “Myocardial Injury After Noncardiac Surgery and Its Association With Short-Term Mortality”
To the Editor:
We read with interest the article by van Waes and colleagues1 assessing the association between myocardial injury and 30-day postoperative mortality in intermediate- to high-risk noncardiac surgery patients aged ≥60 years. Strengths of this study include the large sample of patients at older ages and the adjustment for many known factors that can affect postoperative mortality. The authors used appropriate methods to assess the relationship between myocardial injury and postoperative mortality and openly discussed the limitations of their work.
However, we would like to know why the preoperative hemoglobin level and body mass index are not included in demographic data of patients. It has been shown that preoperative anemia is associated with increased risks of 30-day mortality and adverse cardiac events in elderly patients after noncardiac surgery.2 Furthermore, obesity is an independent predictor of perioperative cardiac adverse events.3 This study did not provide details on anesthesia and intraoperative management. In the patients undergoing noncardiac surgery, intraoperative hypotension, tachycardia, and hypertension are associated independently with postoperative myocardial injury and adverse cardiac outcomes.3 According to preoperative hemoglobin levels and operative blood loss, intraoperative blood transfusion may significantly increase or decrease the risk of 30-day postoperative mortality in elderly patients undergoing major noncardiac surgery.4 Thus, we cannot exclude the possibility that their results would have been biased by the above-mentioned potential confounders.
In this study, the authors did not mention the specific times that cardiac troponin was measured on the first 3 days after surgery. Luo and colleagues5 found that the greatest increase in cardiac troponin occurred between 30 minutes and 8 hours after myocardial ischemia, and then cardiac troponin decreased so that its level was >100% lower 24 hours after surgery. Thus, initiation of troponin measurement at the first 24 hours postoperatively to determine the cutoff value for the detection of significant myocardial injury does not seem accurate enough, given the substantial difference between its levels during this invaluable period for diagnosis and the prediction of major adverse cardiac events. We suggest that the first troponin measurement be performed as early as possible after surgery, especially in patients who are at a high risk of postoperative myocardial injury. For example, cardiac troponin could be measured immediately after surgery in the postanesthesia care unit, at 8 hours, and at 16 hours after surgery. This allows physicians to detect and treat potential myocardial injury earlier, modifying the perioperative prognosis of patients.
Finally, all-cause mortality was used as a primary end point of this study. Actually, perioperative deaths can be classified as inevitable or possibly preventable. This classification will help guide clinicians in avoiding and preventing the risk factors that are important causes of perioperative mortality. Thus, if this study further reported the detailed reasons for all deaths through an analysis of death certificates, medical records, and autopsy reports, we could differentiate which deaths reported by the authors were preventable and which were inevitable. This would immensely help us obtain useful information concerning the areas in which the operative and perioperative management of patients with noncardiac surgery can be improved.
Fu Shan Xue, MD
Yi Cheng, MD
Rui Ping Li, MD
Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, People’s Republic of China
- © 2014 American Heart Association, Inc.
- van Waes JA,
- Nathoe HM,
- de Graaff JC,
- Kemperman H,
- de Borst GJ,
- Peelen LM,
- van Klei WA
- Luo WJ,
- Qian JF,
- Jiang HH