premature ventricular contraction
A premature ventricular contraction is an early, off-schedule beat that fires from somewhere in the ventricles instead of from the heart's normal pacemaker. It jumps the queue, arriving sooner than the next expected beat and usually followed by a slightly longer pause. People often feel it not as the extra beat itself but as the forceful “thump” of the next normal beat after the pause, or as a fleeting skipped sensation.
Because the impulse starts in the ventricle and spreads the slow way through muscle rather than the fast conduction system, the resulting QRS complex on the ECG is wide and oddly shaped. PVCs are extremely common, occurring in most healthy people at least occasionally, and are frequently triggered by caffeine, stress, tiredness or stimulants.
Isolated PVCs in a structurally normal heart are usually harmless and need only reassurance. They warrant a closer look when they are very frequent, occur in runs, or appear alongside heart disease, since in those settings they may signal a higher arrhythmia risk or, rarely, drive a weakening of the heart that can improve once the PVCs are suppressed.
A healthy office worker who drinks several strong coffees reports occasional “skipped beats”; a monitor shows isolated PVCs with a normal echocardiogram, and cutting back on caffeine is all that is advised.
In a structurally normal heart, occasional PVCs are benign and need no drugs.
A very high burden of PVCs — roughly above 10 to 15 percent of all beats over a day — can in some people weaken the left ventricle, a reversible cause of cardiomyopathy worth seeking out.