The principal types of premature contractions are premature atrial complexes (PACs), premature junctional complexes (PJCs), and premature ventricular complexes (PVCs). These complexes result from ectopic premature depolarization arising from the atria (PACs), the AV node or proximal His-Purkinje system (PJCs), or the ventricles (PVCs). Often, patients have no symptoms, or they may have a sensation of “skipped beats.” In many cases, no treatment is needed, but β-blockers or calcium channel blockers can be helpful in symptomatic patients. The correction of underlying abnormalities (eg, drug toxicity, electrolyte imbalance, hyperthyroidism) is often curative.
Premature ventricular complexes typically require no therapy. However, frequent or complex PVCs in the presence of cardiac disease are markers of an increased risk of SCD. Symptomatic patients requiring treatment are best managed with class II drugs (β-blockers) because class I drugs (sodium channel blockers) and class III drugs (potassium channel blockers) appear to worsen the arrhythmia in 5%–20% of patients. Although it is clinically useful, the Vaughan Williams classification of antiarrhythmic drugs (Table 5-3) represents an oversimplification, because many of these medications may have multiple mechanisms of action.
Table 5-3 Vaughan Williams Classification of Antiarrhythmic Drugs
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.