Objectives The co-transmitter neuropeptide Y (NPY) is released during high levels of sympathetic stimulation and is a potent vasoconstrictor. We defined the release profile of plasma NPY during acute ST elevation myocardial infarction, and tested the hypothesis that levels correlate with reperfusion measures after treatment with primary percutaneous coronary intervention (PPCI).

Design Prospective observational study.

Setting University hospital heart centre.

Patients 64 patients (62.6±11.7 years-old, 73% male) presenting throughout the 24-h cycle of clinical activity with ST elevation myocardial infarction.

Interventions PPCI.

Main outcome measures NPY was measured (ELISA) in peripheral blood taken before and immediately after PPCI and at 6, 24 and 48 h post-PPCI. Reperfusion was assessed by angiographic criteria, ST segment resolution, invasive measurement of coronary flow reserve and the index of microcirculatory resistance.

Results Plasma NPY levels were highest before PPCI (17.4 (8.8–42.2) pg/ml, median (IQR)) and dropped significantly post-PPCI (12.4 (6.5–26.7) pg/ml, p<0.0001) and after 6 h (9.0 (2.6–21.5) pg/ml, p=0.008). Patients with admission NPY levels above the median were significantly more hypertensive and tachycardic and were more likely to have diabetes mellitus. Patients with angiographic no-reflow (less than thrombolysis in myocardial infarction 3 flow and myocardial blush grade >2, n=16) or no electrocardiographic ST resolution (<70%, n=30) following PPCI had significantly higher plasma NPY levels. Patients with a coronary flow reserve <1.5 or index of microcirculatory resistance >33 also had significantly higher plasma NPY levels pre-PPCI and post-PPCI.

Conclusions Plasma NPY levels correlate with indices of reperfusion and coronary microvascular resistance.