Conversion between B-type natriuretic peptide and N-terminal pro B-type natriuretic peptide in perioperative risk assessment: protocol for a prospective cohort study.

INTRODUCTION: Both B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-pro-BNP) are used to identify patients at risk of perioperative vascular events, but prognostic thresholds have been established in a large prospective cohort for NT-pro-BNP only. We designed this study to inform perioperative risk interpretation of BNP values. Our primary objective is to validate a formula to convert BNP to NT-pro-BNP concentrations before non-cardiac surgery. The secondary objective is to determine the association between BNP categories (established based on conversion from NT-pro-BNP categories) and a composite outcome of myocardial injury after non-cardiac surgery (MINS) and vascular death. METHODS AND ANALYSIS: This is a single-centre, prospective cohort study in patients undergoing non-cardiac surgery who are >65 years old, Revised Cardiac Risk Index ≥1 or >45 years old with significant cardiovascular disease. BNP and NT-pro-BNP will be measured preoperatively, and troponin measurements will be analysed on postoperative days 1, 2 and 3. MINS and vascular death will be ascertained up to 30 days after surgery. The primary analyses will compare measured NT-pro-BNP values to those predicted by an existing formula (from a non-surgical population) based on BNP concentrations and patient characteristics, and recalibrate and update the formula with additional variables. Secondary analyses will estimate the relationship between categories of measured BNP (corresponding to established NT-pro-BNP thresholds) and the composite of MINS and vascular death. The target sample size of 431 patients is based on our primary analysis (assessing the conversion formula). ETHICS AND DISSEMINATION: Ethics approval has been obtained by the Queen's University Health Sciences Research Ethics Board, and all participants will provide informed consent for participation in the study. The results will be submitted for publication in conferences and in a peer-reviewed journal, and will inform perioperative vascular risk interpretation of preoperative BNP. TRIAL REGISTRATION NUMBER: NCT05352698.

Cardiorespiratory fitness versus physical activity as predictors of all-cause mortality in men.

BACKGROUND: Although both cardiorespiratory fitness (CRF) and physical activity (PA) are associated with mortality, whether they are associated with all-cause mortality independent of each other is unclear. METHODS: CRF was assessed by a maximal exercise test and PA was measured by self-report in 8,171 male veterans. The predictive power of CRF and PA, along with clinical variables, was assessed for all-cause mortality during a mean (±SD) follow-up 8.7 (4.4) years during which there were 1,349 deaths. RESULTS: CRF was associated with mortality after adjusting for clinical variables and remained a strong predictor of mortality after further adjusting for PA (hazard ratio 0.85, 95% CI 0.83-0.87). PA was a significant predictor of mortality after controlling for clinical variables; however, the association was eliminated after further adjusting for CRF (hazard ratio 0.98, 95% CI 0.88-1.10). In CRF-stratified analysis, being active (≥150 min/wk) was not associated with mortality within the unfit or fit categories (P>.4). However, in PA-stratified analysis, subjects categorized as fit (≥7 metabolic equivalents [METS]) had a lower risk of mortality regardless of PA status (P<.001). CONCLUSIONS: In adult men, PA was associated with mortality independent of established risk factors, but not CRF. Conversely, CRF remained a strong predictor of mortality independent of PA status and established risk factors.