OBJECTIVE To compare circulating concentrations of N terminal pro-brain natriuretic peptide (N-BNP) and cardiotrophin 1 in stable and unstable angina.

DESIGN AND SETTING Observational study in a teaching hospital.

PATIENTS 15 patients with unstable angina, 10 patients with stable angina, and 15 controls.

MAIN OUTCOME MEASURES Resting plasma N-BNP and cardiotrophin 1 concentrations.

RESULTS N-BNP concentration (median (range)) was 714 fmol/ml (177–3217 fmol/ml) in unstable angina, 169.5 fmol/ml (105.7–399.5 fmol/ml) in stable angina (p = 0.005v unstable angina), and 150.5 fmol/ml (104.7–236.9 fmol/ml) in controls (p < 0.0001v unstable angina; NSv stable angina). Cardiotrophin 1 concentration was 142.5 fmol/ml (42.2–527.4 fmol/ml) in unstable angina, 73.2 fmol/ml (41.5–102.1 fmol/ml) in stable angina (p < 0.05 v unstable angina), and 27 fmol/ml (6.9–54.1 fmol/ml) in controls (p < 0.0005v stable angina; p < 0.0001v unstable angina). Log cardiotrophin 1 correlated with log N-BNP in unstable angina (r = 0.93, p < 0.0001).

CONCLUSIONS Both circulating N-BNP and cardiotrophin 1 are raised in unstable angina, while cardiotrophin 1 alone is raised in stable angina. The role of cardiotrophin 1 and the relation between cardiotrophin 1 and N-BNP in myocardial ischaemia remain to be defined.