Systemic levels of trimethylamine N-oxide (TMAO), a pro-atherogenic and pro-thrombotic metabolite produced from gut microbiota metabolism of dietary trimethylamine (TMA)-containing nutrients such as choline or carnitine, predict incident cardiovascular event risks in stable primary and secondary prevention subjects. However, the prognostic value of TMAO in the setting of acute coronary syndromes (ACS) remains unknown.

We investigated the relationship of TMAO levels with incident cardiovascular risks among sequential patients presenting with ACS in two independent cohorts. In the Cleveland Cohort, comprised of sequential subjects (n = 530) presenting to the Emergency Department (ED) with chest pain of suspected cardiac origin, an elevated plasma TMAO level at presentation was independently associated with risk of major adverse cardiac events (MACE, including myocardial infarction, stroke, need for revascularization, or death) over the ensuing 30-day (4th quartile (Q4) adjusted odds ratio (OR) 6.30, 95% confidence interval (CI), 1.89–21.0, P < 0.01) and 6-month (Q4 adjusted OR 5.65, 95%CI, 1.91–16.7; P < 0.01) intervals. TMAO levels were also a significant predictor of the long term (7-year) mortality (Q4 adjusted HR 1.81, 95%CI, 1.04–3.15; P < 0.05). Interestingly, TMAO level at initial presentation predicted risk of incident MACE over the near-term (30 days and 6 months) even among subjects who were initially negative for troponin T (< 0.1 ng/mL) (30 days, Q4 adjusted OR 5.83, 95%CI, 1.79–19.03; P < 0.01). The prognostic value of TMAO was also assessed in an independent multicentre Swiss Cohort of ACS patients (n = 1683) who underwent coronary angiography. Trimethylamine N-oxide again predicted enhanced MACE risk (1-year) (adjusted Q4 hazard ratios: 1.57, 95% CI, 1.03–2.41; P <0.05).

Plasma TMAO levels among patients presenting with chest pain predict both near- and long-term risks of incident cardiovascular events, and may thus provide clinical utility in risk stratification among subjects presenting with suspected ACS.