Background: Septic shock (SS) has recently been identified as stimulus of N-terminal pro-brain natriuretic peptide (NT-proBNP) release. We tested whether SS mediates NT-proBNP release through cardiomyocyte necrosis. Moreover, the discriminative value of NT-proBNP for the distinction between SS and non-septic shock (NSS) was assessed.
Methods: The study included 50 ICU patients with SS (n=25) and NSS (n=25), 40 patients with acute coronary syndrome and elevated troponin-I (ACStrop+) and 16 patients with unstable angina and normal troponin-I (UAtrop-). Eleven subjects without inflammation or cardiac disease served as controls. NT-proBNP levels of coronary patients were measured on admission, those of ICU patients 48 h after onset of shock symptoms.
Results: ACStrop+ (1525 [25th-75th percentile: 790-3820] pg/L) and NSS (687 [254-1552]) patients showed increased NT-proBNP levels above those of UAtrop- patients (107 [43-450], p<0.001) and controls (52 [42-99], p<0.001), but SS patients exhibited still higher levels (11,335 [4716-25,769], p<0.001 vs all others). Among ICU patients with shock symptoms, NT-proBNP discriminated SS and NSS with high sensitivity and specificity (area under ROC curve: 0.946 [95% confidence interval, 0.872-1.019]). NT-proBNP correlated with troponin-I, as marker of cardiomyocyte damage, among ACStrop+ (p<0.001) and SS patients (p=0.013). But, whereas SS patients showed the greatest NT-proBNP values, ACStrop+ patients had higher troponin-I levels (p<0.001), suggesting different mechanisms by which myocardial ischemia and SS mediate NT-proBNP release.
Conclusions: SS is a more potent stimulus of NT-proBNP release than myocardial ischemia. NT-proBNP reliably distinguishes SS from other forms of shock. SS-related NT-proBNP release appears to involve cardiomyocyte damage but not genuine cardiomyocyte necrosis.