Frequency of Isolated Posterior Wall Myocardial Infarction in Patients Presenting with ST-Elevation Myocardial Infarction

Background: Isolated posterior-wall myocardial infarction may be overlooked on a standard 12-lead electrocardiogram because it commonly produces reciprocal anterior changes rather than direct ST-segment elevation. Objective: To determine the frequency of isolated posterior-wall myocardial infarction among patients presenting with ST-elevation myocardial infarction. Methods: This hospital-based cross-sectional study included 120 patients presenting with ST-elevation myocardial infarction at the Department of Cardiology, Lady Reading Hospital, Peshawar, from 13 January 2025 to 13 April 2025. Standard 12-lead electrocardiography and posterior leads V7–V9 were used to identify reciprocal ST-segment depression in V1–V3 and direct posterior ST-segment elevation. Categorical variables were summarized as frequencies and percentages, and exploratory subgroup comparisons were performed using Fisher’s exact test. Results: Isolated posterior-wall myocardial infarction was identified in 6 of 120 patients, giving a frequency of 5.0% (95% CI: 2.3%–10.5%). The sample included 79 men (65.8%), and 75 participants (62.5%) were older than 50 years. No statistically significant associations were found with age, sex, body mass index, socioeconomic status, education, residence, or occupational status. Conclusion: Isolated posterior-wall myocardial infarction occurred in a small but clinically relevant proportion of patients presenting with ST-elevation myocardial infarction. Posterior leads may support timely diagnosis when reciprocal anterior changes raise suspicion of posterior involvement.