Sino-Atrial Wenckebach

Report:

Sinus rhythm

Sino-atrial exit block, Möbitz 1

Left atrial abnormality (LAA)

AV block, Möbitz 1, incomplete sequences

Prolonged QT interval

Comment:

This is an example of one form of block preventing the full expression of another: the AV nodal Wenckebach sequences are interrupted by the sino-atrial Wenckebach pauses. The latter makes the entire P-QRS-T sequence accelerate before the pause. Like in AV nodal Wenckebach, the pause is less than two cycles in length.

The patient was on digoxin and quinidine for paroxysmal atrial fibrillation, but asymptomatic and with low-therapeutic drug levels. He may well have had idiopathic sick sinus syndrome15,16. This was in 1974, when no better drugs were available to keep him in sinus rhythm. Two decades later, drugs safer but not significantly more effective than quinidine are available. The problem remains17.

Note the QT interval dependency on the preceding cycle length.

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