Complete atrioventricular block due to myocardial infarction

ECG:Sinus rhythm with ST segment elevation in the inferior territory with reciprocity in leads I, aVL, V2 and V3;

ECG 2:Second tracing obtained a few minutes later;

ECG 2: atrioventricular dissociation with persistence of ST segment elevation; complete AV block due to inferior infarction;

Comments: The incidence of complete atrioventricular block in the setting of an acute infarction has considerably decreased since the use of reperfusion techniques (thrombolysis or emergency angioplasty) although remains nonetheless non-negligible (approximately 3 to 5%). Depending on the location of the infarction (anterior or inferior/posterior), the evolving and anatomical morphological characteristics of the block differ from one another.

There is a sub-section in the new European recommendations for post-infarction AV block. There is no indication for definitive pacing (class III) if an AV block occurring in the aftermath of an infarction regresses spontaneously. In the rare cases where the complete AV block becomes permanent (after several weeks), a pacemaker should be implanted.

This patient underwent an angioplasty of the first segment of the right coronary artery with good results and the placement of a temporary pacing catheter; the conduction disorder regressed after 2 days, after which the catheter was removed.

Take-home message: Depending on the location of the infarction (anterior or inferior/posterior), the anatomical and evolving morphological characteristics of the AV block are opposite. The prognosis is often highly altered in the setting of a post-infarction anterior AV block, with very high mortality. Conversely, the conduction disorder is most often spontaneously resolved within a few days in the setting of an inferior infarction. The indications for definitive pacemaker implantation are therefore very rare.