Premature Ventricular Contraction
PVCs are characterized by the premature occurrence of strangely shaped QRS complexes, with the electrocardiographic wave (QRS) width usually greater than 120 msec. These complexes are not preceded by a P-wave, and the T-wave is usually large and opposite in direction to the major deflection of the QRS.
In other words, the left and right ventricals of the heart contract before they have time to fill with blood again. This has the potential to disrupt the rhythm of the heart.
In the United States, PVCs are one of the most common arrhythmias. They occur in patients with and without heart disease. In healthy, middle-aged males, more than 60% will show PVCs on routine Holter monitoring. In patients with prior myocardial infarction (MI), more than 80% will show evidence of PVCs on Holter.