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.