PubMed · 2240926
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A Patel, D Goldman. 1990-12-15. Syncope and functional infranodal block.. https://doi.org/10.7326/0003-4819-113-12-994
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We report a case of an adult male in whom, one week after an anterior acute myocardial infarction, we documented nocturnal episodes of type II second degree atrio-ventricular heart block, including advanced heart block episodes (4:1). An electrophysiologic study did not show atrio-ventricular conduction abnormalities, so we suspected a possible sleep apnea syndrome, which was confirmed with a polysomnographic study. It was observed that advanced heart block episodes were preceded by significant decreases in arterial oxygen saturation. These episodes disappeared with continuous positive air pressure ventilation.
It is traditionally assumed that impulse propagation in cardiac muscle is determined by the combination of two factors: (1) the active properties of cardiac cell membranes and (2) the passive electrical characteristics of the network formed by cardiac cells. However, advances made recently in the theory of generic excitable media suggest that an additional factor-the geometry of excitation wavefronts -may play an important role. In particular, impulse propagation strongly depends on the wavefront curvature on a small spatial scale. In the heart, excitation wavefronts have pronounced curvatures in several situations including waves initiated by small electrodes, waves emerging from narrow tissue structures, and waves propagating around the sharp edges of anatomical obstacles or around a zone of functional conduction block during spiral wave rotation. In this short review we consider the theoretical background relating impulse propagation to wavefront curvature and we estimate the role of wavefront curvature in electrical stimulation, formation of conduction block, and the dynamic behavior of spiral waves.
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