Atrial Quadrigeminy
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Patient: Woman, 76 y/o. Admitted to the ER for palpitations. Medical history not available.
ECG description:
- Sinus rhythm
- Every fourth sinus beat is followed by a premature atrial contraction (PAC)
- PACs have fixed coupling interval, are preceded by an ectopic P wave and a short PR interval. P’ wave is upright in inferior leads.
- Normal, horizontal cardiac axis at ca. 10°
ECG interpretation:
Every fourth sinus beat is followed by a supraventricular extrasystole with a fixed coupling interval. This pattern is called quadrigeminy. The coupling interval is the interval between the sinus P wave and the ectopic P wave. While varying coupling intervals are often seen in parasystolia, a fixed coupling interval suggests the presence of an ectopic focus that due to increased automaticity decides to fire during normal sinus rhythm. The P wave preceding each premature beat is partially hidden in the preceding P wave, but the PR interval is clearly shorter than in the sinus cycles. This suggest that the PAC origins from a site nearby the sinus node, but closer to the AV junction. The PR interval exceeds 100ms, which suggests an atrial focus rather than a junctional, in which the PR interval would be expected to be shorter. In AV junctional extrasystolia, the atria is often depolarized in a retrograde fashion as the ectopic impulse starts around the AV junction and spreads upwards through the atrium. This normally produces inverted P waves in the inferior leads. Here however, the P wave is upright in the inferior leads, which also indicates an atrial focus.
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