Digitalis intoxication: Junctional tachycardia with and without AV block

In a patient with longstanding atrial fibrillation being treated with digoxin, a regular tachycardia, as seen in A, with a RBBB suggests a junctional or supraventricular tachycardia. Group beating, in B, is likely due to a 2nd degree, Type 1, exit block below the ectopic junctional focus. This is highly suggestive of digitalis intoxication