Beyond the Culprit Lesion: Interacting Ischemic and Catecholamine-Mediated Stress in STEMI

ST-elevation myocardial infarction (STEMI) is classically understood as the consequence of plaque disruption, thrombotic coronary obstruction, and downstream ischemic myocardial injury. This framework remains fundamentally correct and continues to justify urgent reperfusion as the cornerstone of treatment. In some patients, however, the acute STEMI phenotype may also reflect a sympathetic stress response that occurs alongside ischemia. We hypothesize that ischemia, pain, and distress can trigger this response and that catecholamine effects may amplify myocardial stress globally or within the ischemic territory. The word “parallel” therefore describes co-occurring and interacting processes, not a proven independent injury pathway. The magnitude and clinical importance of any catecholamine-mediated contribution remain uncertain. Takotsubo syndrome offers biological plausibility for catecholamine-related myocardial dysfunction, but it is a multifactorial syndrome and does not establish the same mechanism in STEMI. A previously published retrospective series of 21 hemodynamically stable STEMI patients reported rapid symptom improvement after intravenous metoprolol before transfer. This clinically striking signal motivates our hypothesis that early beta-blockade may be underused in carefully selected, stable STEMI patients before reperfusion. The uncontrolled series cannot establish treatment efficacy, mechanism, or the prevalence of underuse: symptom relief may reflect reduced myocardial oxygen demand or concomitant care, and angiography performed later cannot establish coronary flow when symptoms resolved. Current guidance permits intravenous beta-blockade in selected, hemodynamically stable STEMI patients without acute heart failure or other contraindications, but COMMIT found no overall mortality benefit and showed fewer reinfarctions and episodes of ventricular fibrillation alongside more cardiogenic shock. Later trials differ. These findings leave uncertainty about patient selection, timing, outcomes, and mechanisms; they do not establish that trial regimens were inadequate. Future studies should test this underuse hypothesis with contemporary utilization data and a carefully selected, guideline-bounded approach, not presume that individualized escalation improves outcomes.