Electrocardiogram Pathology Quiz

See Ectopic Beats. A ventricular ectopic beat, also called a premature ventricular complex, occurs before the next expected sinus beat. The combination in B is typical: an early broad QRS without a preceding P wave that caused it. Activation starts in ventricular tissue and usually spreads through muscle in an abnormal sequence, rather than arriving through the usual coordinated route. This takes longer and broadens the QRS. A sinus P wave may happen to appear nearby without being responsible for that ventricular beat, so look at timing as well as shape. Width alone is not conclusive because a supraventricular impulse conducted abnormally can also produce a broad complex.

An early abnormal P followed by a normally conducted QRS (D) indicates atrial ectopy. An inverted P hidden in or close to a narrow QRS (C) suggests activation from the AV junction, travelling backwards into the atria. The sustained irregular rhythm in E suggests AF rather than one isolated premature ventricular beat. A prolonged PR with otherwise conducted beats (A) is first-degree AV delay and does not itself generate an early beat.