B-type natriuretic peptide in high-risk major surgery patients
Graz, Austria
* E-mail: elisabeth.mahla{at}meduni-graz.at
Editor—We read with great interest the article by Cuthbertson and colleagues1 demonstrating the association of preoperative B-type natriuretic peptide (BNP) levels and adverse cardiac events. In 204 low to intermediate risk patients undergoing major non-cardiac surgery, moderately elevated preoperative BNP levels of 40 pg ml–1 predicted early postoperative death or myocardial injury (area under the ROC curve 0.72; 95% CI interval 0.59–0.86). This article underlines recent suggestions that the biochemical markers BNP and N-terminal pro-brain natriuretic peptide (NT-proBNP) outperform existing cardiac risk scores regarding prognostic importance.2 3 Unfortunately, the short in-hospital observation period of 72 h limits the significance and clinical importance of this hitherto largest blinded trial on the prognostic power of preoperative BNP. Although the majority of myocardial infarctions occurs within the first 48 h after surgery, delayed postoperative myocardial infarction is a well-known complication and may have been missed in this trial. Furthermore, as mentioned in the editorial4 accompanying this study, postoperative determination of NT-proBNP provides additional prognostic information to preoperative levels regarding in-hospital and long-term cardiac outcome.5 BNP and NT-proBNP are released from cardiac myocytes in response to ischaemia or myocardial stretch and plasma levels correlate well with the extent of inducible ischaemia.6 Preoperative ‘stable’ levels of natriuretic peptides therefore do not necessarily reflect the variable dynamic consequences of the intra- and postoperative stress response which culminates in adverse in-hospital7 and long-term cardiac outcome.8 Thus, although we recognize that the importance of postoperative NT-proBNP determination in non-cardiac surgery was just very recently published, the significance of the results of Cuthbertson and colleagues would have been further improved by a prolonged observation period and by additional postoperative BNP determinations.
Aberdeen, UK
* E-mail: b.h.cuthbertson{at}abdn.ac.uk
Editor—In reply to the interesting points made by Dr Mahla and colleagues, we agree with many of the statements made in their letter. However, the measurement of BNP in the postoperative period does not add any additional predictive power to preoperative BNP measurement in the prediction of these short-term outcomes such as early postoperative cardiac events (unpublished data from same cohort). Further, our work on the predictive power of BNP for medium term mortality is about to be published in the American Journal of Cardiology within the next 2 months. I am sure the respondents will find this paper interesting. Although we may have missed some of the postoperative cardiac events occurring in hospital in this cohort due to our timing of measurements, we feel that any significant events will be detected in medium term mortality analysis. As they state, other work suggests this is the case.
References
1 Cuthbertson BH, Amiri AR, Croal BL, et al. Utility of B-type natriuretic peptide in predicting perioperative cardiac events in patients undergoing major non-cardiac surgery. Br J Anaesth (2007) 99:170–6.
2 Dernellis JM, Panaretou MP. Assessment of cardiac risk before noncardiac surgery: brain natriuretic peptide in 1590 patients. Heart (2006) 92:1645–50.
3 Feringa HH, Schouten O, Dunkelgrun M, et al. Plasma N-terminal pro-B-type natriuretic peptide as long-term prognostic marker after major vascular surgery. Heart (2007) 93:226–31.
4 Sear JW, Howard-Alpe G. Preoperative plasma BNP concentrations: do they improve our care of high-risk non-cardiac surgical patients? Br J Anaesth (2007) 99:151–4.
5 Mahla E, Baumann A, Rehak P, et al. N-terminal pro-brain natriuretic peptide identifies patients at high risk for adverse cardiac outcome after vascular surgery. Anesthesiology (2007) 106:1088–95.[CrossRef][Medline]
6 Bibbins-Domingo K, Ansari M, Schiller NB, et al. B-type natriuretic peptide and ischemia in patients with stable coronary disease: data from the Heart and Soul study. Circulation (2003) 108:2987–92.
7 Landesberg G, Mosseri M, Zahger D, et al. Myocardial infarction after vascular surgery: the role of prolonged stress-induced, ST depression-type ischemia. J Am Coll Cardiol (2001) 37:1839–45.
8 Bursi F, Babuin L, Barbieri A, et al. Vascular surgery patients: perioperative and long-term risk according to the ACC/AHA guidelines, the additive role of post-operative troponin elevation. Eur Heart J (2005) 26:2448–56.
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