The Relation between Serum Phosphorus Levels and Clinical Outcomes after Acute Myocardial Infarction

BACKGROUND Elevated serum phosphorus levels have been linked with cardiovascular disease and mortality with conflicting results, especially in the presence of normal renal function. METHODS We studied the association between serum phosphorus levels and clinical outcomes in 1663 patients with acute myocardial infarction (AMI). Patients were categorized into 4 groups based on serum phosphorus levels (<2.50, 2.51-3.5, 3.51-4.50 and >4.50 mg/dL). Cox proportional-hazards models were used to examine the association between serum phosphorus and clinical outcomes after adjustment for potential confounders. RESULTS The mean follow up was 45 months. The lowest mortality occurred in patients with serum phosphorus between 2.5-3.5 mg/dL, with a multivariable-adjusted hazard ratio of 1.24 (95% CI 0.85-1.80), 1.35 (95% CI 1.05-1.74), and 1.75 (95% CI 1.27-2.40) in patients with serum phosphorus of <2.50, 3.51-4.50 and >4.50 mg/dL, respectively. Higher phosphorus levels were also associated with increased risk of heart failure, but not the risk of myocardial infarction or stroke. The effect of elevated phosphorus was more pronounced in patients with chronic kidney disease (CKD). The hazard ratio for mortality in patients with serum phosphorus >4.5 mg/dL compared to patients with serum phosphorus 2.50-3.50 mg/dL was 2.34 (95% CI 1.55-3.54) with CKD and 1.53 (95% CI 0.87-2.69) without CKD. CONCLUSION We found a graded, independent association between serum phosphorus and all-cause mortality and heart failure in patients after AMI. The risk for mortality appears to increase with serum phosphorus levels within the normal range and is more prominent in the presence of CKD.