Voltage dependent conduction abnormalities in His bundle pacing in patients without His Purkinje system disease
Rehan Mahmud1, Shakeel Jamal1, Mohamed Musheinesh1
1Bay Heart and Vascular, 1900 Columbus Ave, Bay City, MI 48708, United States of America.
Insights
His bundle pacing can cause conduction delays, particularly at lower voltages. Increasing pacing voltage resolves these delays, improving His Purkinje system conduction during His bundle pacing.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Pacing
Background:
- His bundle (HB) pacing involves active fixation of the HB lead, which can disrupt conduction fibers and lead to delays.
- Pre-existing His Purkinje conduction delays have been observed to normalize with increased pacing voltage.
Purpose of the Study:
- To investigate if conduction delays observed during penetrative His bundle pacing are voltage-dependent.
- To determine if higher stimulus voltages can resolve these conduction delays.
Main Methods:
- Evaluated the effect of pacing voltage on His Purkinje system-ventricular activation time (hVAT) in 17 patients undergoing His bundle pacing.
- Assessed electrocardiographic (ECG) evidence of conduction delay in relation to pacing voltage.
Main Results:
- Significant prolongation of hVAT, indicating conduction delay, was found in 13 out of 17 patients at lower voltages.
- ECG changes consistent with rightward delay were observed in 9 patients.
- Both hVAT prolongation and ECG delays resolved with higher stimulation voltages.
- A pre-excitation-like abnormality was noted in 15 patients, primarily at higher voltages, without hVAT prolongation.
Conclusions:
- His bundle pacing is associated with significant conduction delays at low voltages, which are reversible with higher stimulation.
- The observed pre-excitation-like abnormality appears at high voltage and does not inherently prolong hVAT.
Background:
During His bundle (HB) pacing, the active fixation of HB lead may cause disruption of the enclosed conduction fibers and cause conduction delay. His Purkinje conduction delays have been shown to revert to normal with higher voltage pacing.
Objective:
To determine if conduction delays seen with penetrative HB pacing are voltage dependent and can resolve with higher stimulus voltage.
Methods:
In 17 patients undergoing HBP, the effect of voltage on a composite His Purkinje system-ventricular activation time (hVAT) as well as electrocardiographic (ECG) evidence of conduction delay, was systematically evaluated.
Results:
There was highly significant prolongation of hVAT indicative of conduction delay in 13/17 patients. ECG changes of rightward delay were also seen in 9/13 patients. Both types of delays we manifest at lower voltages and we uniquely resolved by higher stimulation voltage. A pre-excitation like abnormality was also seen in 15/17 patients. This conduction abnormality was manifest at higher voltage without prolongation of hVAT. In 6/15 patients the pre-excitation like abnormality ceased at lower voltage.
Conclusion:
HB pacing is associated with evidence of significant conduction delay noted at low voltage, which resolves with higher stimulation voltage. The more common pre-excitation like abnormality appears to occur at high voltage and, in of itself, does not appear to prolong hVAT.
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