Baseline Serum Potassium Within the Normal Range Is Independently Associated With One-Year Myocardial Strain Recovery in Patients With ST-Segment Elevation Myocardial Infarction Treated With Primary Percutaneous Coronary Intervention: A Cardiac Magnetic Resonance Study.

BACKGROUND: While serum potassium abnormalities predict mortality in acute myocardial infarction, whether potassium levels within the normal range influence long-term myocardial functional recovery remains unknown. Therefore, this study aimed to investigate the association between baseline potassium levels and 1-year cardiac magnetic resonance (CMR)-derived global longitudinal strain in patients with ST-segment elevation myocardial infarction (STEMI). METHODS: This retrospective cohort study enrolled 120 consecutive patients with STEMI (mean age 52.4 ± 12.6 years, 94.2% male) who underwent primary percutaneous coronary intervention (PCI) and completed 1-year CMR follow-up. Baseline electrolyte levels, including potassium, sodium, chloride, magnesium, ionized calcium, and phosphorus, were measured before the intervention. The primary outcome was 1-year absolute global longitudinal strain (abs_GLS) assessed by CMR feature tracking. Analysis of covariance (ANCOVA) was used to evaluate associations between electrolyte levels and myocardial strain after adjustment for baseline abs_GLS and 16 clinical covariates, including discharge medications. RESULTS: Baseline potassium averaged 3.92 ± 0.26 mmol/L, with 90% of values ranging from 3.42 to 4.39 mmol/L. After adjustment for baseline abs_GLS and 16 clinical covariates, potassium was the only electrolyte significantly associated with 1-year abs_GLS in the prespecified primary model. Each 1-SD increase in potassium (0.26 mmol/L) was associated with a 0.782 percentage-point higher 1-year abs_GLS (95% CI: 0.042-1.521, p = 0.041). Categorical analysis showed a nonsignificant trend across potassium tertiles (T1 [<3.82 mmol/L]: 10.3%; T2 [3.82-4.02 mmol/L]: 11.6%; T3 [>4.02 mmol/L]: 12.0%; p for trend = 0.159), with the highest tertile exhibiting a 1.7-percentage-point higher adjusted abs_GLS than the lowest tertile. CONCLUSIONS: Among patients with STEMI treated with primary PCI, baseline serum potassium, even within the normal range, is independently associated with 1-year myocardial strain recovery, with a trend toward superior outcomes at higher-normal levels. These findings suggest that potassium may serve as a readily available prognostic biomarker for risk stratification; nonetheless, randomized trials are warranted to investigate whether targeted optimization of potassium can improve post-infarction cardiac recovery.