['The implantable cardioverter-defibrillator (ICD) is the most effective treatment for preventing arrhythmic deaths in patients with heart failure, but periprocedural complications, including in-hospital mortality or cardiac arrest, may occur, and little is known about risk factors. We asked whether elevated B-type natriuretic peptide (BNP) level is associated with increased risk of in-hospital mortality or cardiac arrest in patients undergoing ICD implantation.', 'From the National Cardiovascular Data Registry ICD Registry, we identified 53 198 patients who received ICD implants and underwent preoperative BNP measurement from 2006 to 2008. The patients were categorized into 4 groups by BNP levels (<100, 100 to <300, 300 to <1000, and ≥1000 pg/mL). Complication rates were compared among groups, and odds ratios for in-hospital mortality or cardiac arrest were estimated by multiple hierarchical logistic regressions. There were 2952 complications reported, including 510 in-hospital deaths and 365 cardiac arrests. The rate of in-hospital mortality or cardiac arrest significantly increased with elevated BNP level (P<0.001). The adjusted odds ratios of in-hospital mortality or cardiac arrest were statistically significant in all 3 higher BNP groups [odds ratio (95% CI), 1.99 (1.17 to 3.39), 2.49 (1.50 to 4.13), and 4.25 (2.57 to 7.06) in the second, third, and fourth groups using <100 as reference]. Among subgroups, the association was more significant in men, patients with renal dysfunction, and patients undergoing biventricular ICD implantation.'] Is elevated B-type natriuretic peptide associated with increased in-hospital mortality or cardiac arrest in patients undergoing implantable cardioverter-defibrillator implantation?