Atrial Versus Ventricular Ectopy: The Ashman Phenomenon!

The above electrocardiogram (ECG) was obtained in a patient with near syncope and bradycardia. The rhythm was initially interpreted electronically as sinus bradycardia, left ventricular hypertrophy with strain pattern, left atrial enlargement and premature ventricular complexes (PVCs). The heart rate as evident from the rhythm strip was approximately 51 beats per minute with a cycle length of 1154 ms. Two early coupled premature wide complex beats are noted (red arrows) with right bundle branch block morphology. Closer examination of these premature beats reveals non-sinus P waves preceding each beat and fused with a prior T wave (green arrows). The cycle length spanning the sinus p wave preceding the ectopic beat till the sinus beat following it is 1659 ms, less than twice the sinus cycle length, indicating a non-compensatory pause. Both of these observations are highly suggestive of an atrial origin of the ectopic beats which conducted with aberration due to a long-short cycle length causing refractoriness of the right bundle (Ashman Phenomenon).