Premature Ventricular Contractions (PVCs) Premature Ventricular Contractions (PVCs) are early heartbeats originating from the ventricles instead of the atria. PVCs are categorized based on their origin, morphology, frequency, and pattern. Here's a breakdown of the types of PVCs seen on ECG: 🔹 1. Based on Morphology: 》Unifocal PVCs ▪︎All PVCs look the same (same shape and axis). ▪︎Originate from a single ectopic focus in the ventricles. 》Multifocal PVCs ▪︎PVCs have different shapes (different morphologies). ▪︎Arise from multiple ectopic foci. ▪︎Often considered more concerning than unifocal. 🔹 2. Based on Frequency: 》Occasional: Few PVCs seen (e.g., <6 per minute). 》Frequent: More than 6 PVCs per minute. 》Bigeminy: Every normal beat is followed by a PVC (normal–PVC–normal–PVC). 》Trigeminy: Every third beat is a PVC 》Quadrigeminy: Every fourth beat is a PVC. 🔹 3. Based on Timing/Pattern 》Interpolated PVC ▪︎A PVC that occurs between two normal beats without a compensatory pause. ▪︎Often seen when the PVC doesn’t disrupt the SA node. 》Couplets ▪︎Two consecutive PVCs. 》Triplets ▪︎Three consecutive PVCs (can be a short run of ventricular tachycardia). 》Run of PVCs / Non-sustained Ventricular Tachycardia (NSVT) ▪︎Three or more PVCs in a row, lasting <30 seconds. 🔹 4. Based on QRS Morphology 》Left Bundle Branch Block (LBBB)–like morphology ▪︎Indicates the PVC arises from the right ventricle. 》Right Bundle Branch Block (RBBB)–like morphology ▪︎Indicates the PVC originates in the left ventricle. 🔹 5. R-on-T Phenomenon ▪︎PVC that falls on the T wave of the preceding beat. ▪︎Dangerous, as it can trigger ventricular fibrillation or torsades de pointes. PVC Characteristics on ECG: ▪︎Wide QRS complex (>120 ms) ▪︎No preceding P wave ▪︎ST-T discordance (T wave is in opposite direction of the QRS) ▪︎Compensatory pause typically follows (the SA node fires on time, but the PVC delays the next beat)