Discussion
Guidelines state that revascularization should be considered in late presenting MI’s with high grade AV blocks (1), but clear recommendations for PCI time in these situations are lacking. Studies focusing on outcomes in these situations are limited with complete heart block being a bad prognostic marker even in the primary PCI era (2). In a retrospective study looking at AV block recovery following late PCI in inferior wall MI with high grade AV blocks (82% of them had CAVB), a median time to PCI of 4 days resulted in complete recovery of 1:1 AV conduction for all patients at discharge (3).
A similar case report by Liang et al (4) suggested that late coronary intervention in a patient presenting with IWMI complicated by complete heart block avoided a potential permanent pacemaker implant. However, In this case the AV block developed after presenting late to the hospital and complete revascularization was achieved within a short span of developing the conduction block.
The AV node tissue has been described as resistant to permanent damage due to its high intracellular glycogen content (5), unique blood supply involving adjacent septal perforators, and ability to absorb oxygen and nutrients from the neighbouring venous sinusoids (6). Conduction system abnormalities in acute posterior-inferior infarction are hence usually transient. However, it has been observed that those with persistence of such disturbance have more extensive damage to the conduction system involving the proximal as well as distal areas (7). It is in this group of patients with persistent high-grade AV blocks that revascularization, even if late, may result in good outcomes.