Abstract
We investigated the properties which affect the capture thresholds in order to improve selective pacing. We performed biophysically detailed, computer simulations of a His fibre running through a septal wedge preparation to compute capture thresholds under various configurations of electrode polarity and orientation. The myocardial capture threshold was close to that of the His bundle. The His fibre needed to intersect with the electrode tip to favor its activation. Inserting the electrode fully within the septum increased the myocardial capture threshold. Reversing polarity, to rely on anode break excitation, also increased the ease of selective pacing. Model results were consistent with clinical observations. For selective pacing, the tip needs to be in contact with the His fibre and anodal stimulation is preferable. This study provides insight into helping establish electrode and stimulation parameters for selective His bundle pacing in patients.
Highlights
T HE His-Purkinje system (HPS) is responsible for rapid activation of the heart
The pacing threshold is in the range 1–2 V with non-selective His Bundle Pacing (HBP) (NS-HBP), that is, recruiting surrounding myocardium in addition to the His bundle, occurring more frequently than selective-HBP (S-HBP) [4], exciting only the His bundle
Capture thresholds for myocardium (CT M ) and His fibre (CT H ) were computed, with the capture threshold defined as the minimum voltage between the tip and ring required to elicit an action potential in the appropriate tissue
Summary
In a population of patients, the HPS may be healthy, but conduction block may occur within the atrioventricular node or very proximal to it. This has provided a rationale for His Bundle Pacing (HBP), which. Attempts to restore sinus activation by directly stimulating the His bundle through an electrode introduced into the right ventricular septum. This is applicable to a number of conditions [1], with the resulting improvement in activation has been shown to be superior to traditional right ventricular apical pacing [2] Recently, pacing of the left bundle branch has been proposed, which involves advancing the pacing lead further into the septum to reach the left bundle branch region [3]. The exact mechanisms and their importance remain to be elucidated
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