PVCs, Couplets, and Bigeminy

A premature ventricular complex — an early beat from an irritable focus in ventricular muscle, below the bundle branches, producing a wide, bizarre QRS with no preceding related P wave.

The impulse starts below the bundle branches and spreads slowly muscle-cell-to-muscle-cell instead of using the fast His–Purkinje highway, so QRS ≥ 0.12 s (≥3 small boxes).

The T wave points opposite the main QRS deflection — tall upright PVC has an inverted T; deep negative PVC has an upright T. This is normal for ectopy.

The PVC doesn't reset the sinus node, so the R-R interval spanning the PVC (beat before to beat after) equals two normal R-R intervals.

A PAC has a narrow QRS, usually has a P wave (often abnormal), and resets the sinus node producing a non-compensatory (shorter) pause.

Unifocal PVCs all look identical (one irritable focus); multifocal (multiform) PVCs have different shapes, implying multiple sites — more concerning.

Couplet = 2 PVCs back-to-back; triplet/salvo = 3 in a row; 3 or more consecutive PVCs at a rate >100 = ventricular tachycardia (non-sustained if <30 s).

Bigeminy = every other beat is a PVC; trigeminy = every third beat; quadrigeminy = every fourth beat.

A PVC landing on the previous beat's T wave during the vulnerable repolarization window; it can trigger VT or ventricular fibrillation — the most worrisome pattern to flag.

PVCs come so early the ventricle hasn't filled, so stroke volume is tiny and often produces no palpable pulse — a monitor rate of 80 may mean a perfusing rate near 40 (pulse deficit).

Name the underlying rhythm first, then the ectopy — e.g., "Sinus rhythm at 72 with ventricular bigeminy."

Hypoxia, ischemia, electrolyte disturbance (low potassium or magnesium), stimulants (caffeine, nicotine, cocaine), digoxin toxicity, and cardiac catheters.