Differential Diagnosis for Sinus Rhythm with Abnormal QRS(T) Contour

Single Most Likely Diagnosis

• Anteroseptal Myocardial Infarction (MI): The presence of a sinus rhythm with a normal electrical axis and an R/S transition shift to the right, along with a QRS(T) contour abnormality, strongly suggests an anteroseptal MI. This condition is characterized by damage to the heart muscle in the anteroseptal region, often due to a blockage in the left anterior descending (LAD) coronary artery.

Other Likely Diagnoses

• Left Ventricular Hypertrophy (LVH): LVH can cause abnormal QRS(T) contours due to the thickening of the left ventricular wall, which can lead to altered electrical conduction patterns.
• Bundle Branch Blocks: Both left and right bundle branch blocks can result in abnormal QRS(T) contours. The shift in R/S transition and the contour abnormality might be indicative of a conduction delay or block in one of the bundle branches.
• Ventricular Septal Defect (VSD): A VSD, especially if large, can lead to abnormal QRS patterns due to the altered hemodynamics and potential for septal hypertrophy or fibrosis.

Do Not Miss Diagnoses

• Acute Coronary Syndrome (ACS): It is crucial not to miss ACS, as it requires immediate intervention. The symptoms and ECG findings could be indicative of an evolving MI or unstable angina.
• Cardiac Sarcoidosis: This condition can cause various ECG abnormalities, including those mimicking MI or bundle branch blocks, due to granulomatous infiltration of the heart.
• Hypertrophic Cardiomyopathy (HCM): HCM can lead to abnormal ECG findings, including QRS(T) abnormalities, due to the asymmetric septal hypertrophy and potential for outflow tract obstruction.

Rare Diagnoses

• Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): Although more commonly associated with right ventricular abnormalities, ARVC can occasionally present with left ventricular involvement, leading to ECG changes that might mimic those of anteroseptal MI.
• Myocardial Fibrosis: Focal or diffuse myocardial fibrosis, which can be due to various causes including previous MI, can lead to abnormal QRS(T) contours due to the scarring of the heart muscle.
• Cardiac Amyloidosis: This condition, characterized by the deposition of amyloid proteins in the heart, can cause a variety of ECG abnormalities, including those that might be confused with MI or other structural heart diseases.