Serum potassium levels on admission and infarct size in patients with acute myocardial infarction.

BACKGROUND: Little data exist on the relationship between potassium level and infarct size after ST-segment elevation acute myocardial infarction (STEMI). We investigated the influence of potassium levels on infarct size measured with single photon emission computed tomography (SPECT) in patients with STEMI after mechanical reperfusion.

METHODS: The study included 598 patients. Potassium measurements at baseline and 2 SPECT examinations, at baseline and 7-14 days after intervention, were performed. Infarct size in the 7-14 days SPECT and salvage index were the primary outcome analyses.

RESULTS: Tertiles of baseline potassium were: <4.05 mEq/L (1st tertile), 4.05-4.37 mEq/L (2nd tertile) and >4.37 mEq/L (3rd tertile). In potassium 1st, 2nd and 3rd tertiles, the infarct size in the 7-14 days SPECT (median [25th-75th percentiles]) was 9.0% [2.0%-21.8%], 10.0% [3.5%-22.0%] and 12.0% [5.0%-25.5%] of left ventricle (p=0.026); salvage index was 0.50 [0.26-0.84], 0.56 [0.26-0.81] and 0.40 [0.23-0.75] (p=0.09). Patients with anterior infarction in upper potassium tertile had greater infarct size compared with patients in lower potassium tertile (p=0.049). After adjustment in multivariable analysis, potassium was an independent correlate of infarct size in the 7-14 days SPECT (p=0.05).

CONCLUSIONS: In patients with STEMI, higher baseline potassium levels are associated with a larger scintigraphic infarct size.