Myocardial Infarction in an Ironman Triathlete: A Case for Advanced Lipid Testing in Cardiovascular Risk Assessment.

Atherosclerotic cardiovascular disease (ASCVD) risk assessment relies heavily on low-density lipoprotein cholesterol (LDL-C), arterial blood pressure, and population-based risk calculators. Although effective for population screening, these approaches may underestimate risk in individuals with discordant lipid profiles when atherogenic particle burden is not captured by conventional testing. We report a 55-year-old male Ironman triathlete who suffered an acute myocardial infarction during competition. Evaluation showed posterior ST-segment changes, metabolic acidosis, transient hyperglycemia, and acute kidney injury. Coronary angiography revealed chronic total occlusion of the right coronary artery, complete occlusion of the left circumflex artery, and severe distal left anterior descending artery stenosis requiring multivessel percutaneous coronary intervention. Longitudinal outpatient testing demonstrated unremarkable risk factors, including mildly elevated total cholesterol and LDL-C, normal apolipoprotein B (apoB), and normal glycemic markers suggestive of low 10-year ASCVD risk. Advanced lipid testing after discharge showed markedly elevated LDL particle number (LDL-P) and increased small dense LDL (sdLDL), consistent with LDL pattern B. This case highlights how particle-based abnormalities may contribute to accelerated atherosclerosis despite reassuring conventional risk assessment and absence of guideline-defined lipid risk-enhancing factors.