Relevant Findings: View Tony’s annotated electrocardiogram (the black bar represents one second).  The reason for Tony’s irregular heart rhythm on auscultation is sinus tachycardia with ventricular ectopic complexes. There is shiver artifact present (marked with blue brackets) which causes some “noise” in the baseline.  The underlying sinus tachycardia was diagnosed based on an approximate heart rate of 240 bpm and the reliable presence of P waves (red arrows) preceding most narrow QRS complexes.  Paired, uniform ventricular ectopic complexes (green arrows) are present throughout the ECG recording and are identified as ventricular in origin based on their wide and bizarre appearance, and the lack of associated P waves. Tony’s increased R wave height of 1.0 mV (normal up to 0.9 mV) is consistent with a left ventricular enlargement pattern.  Right or left atrial enlargement is usually reflected in changes in the P wave height or width.  Right ventricular enlargement/hypertrophy may change the polarity of the QRS complex (making the major deflection negative) or cause a sinus complex to have a wide QRS deflection.