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Mechanisms by which AC leakage currents cause complete hemodynamic collapse without inducing fibrillation
1Joint Program in Biomedical Engineering at The University of Memphis and The University of Tennessee-Memphis, 38152-3210, USA. ramalkin@memphis.edu
Journal of Cardiovascular Electrophysiology
|November 9, 2001
Summary
Weak alternating current (AC) stimulation can cause hemodynamic collapse in humans below the ventricular fibrillation (VF) threshold. This occurs due to rapid, regular electrical excitation, a newly identified risk during cardiac procedures.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
- Medical Device Safety
Background:
- Previous studies identified a risk of hemodynamic collapse during weak alternating current (AC) stimulation in humans, occurring below the threshold for ventricular fibrillation (VF).
- The exact mechanisms underlying this previously unrecognized danger were not fully understood.
Purpose of the Study:
- To investigate the mechanisms responsible for hemodynamic collapse during weak AC stimulation.
- To determine the relationship between electrical stimulation parameters and cardiac mechanical response.
Main Methods:
- Six dogs underwent right ventricular (RV) pacing with a quadripolar catheter using AC stimulation (10–160 Hz, 10–1,000 microA).
- ECG, femoral artery pressure, and RV electrical activity were recorded.
- Hemodynamic response was categorized as VF, collapse without VF (COLLAPSE), extrasystolic without collapse (EFFECT), or no effect (NSR).
- Electrical activation intervals (ISI) were compared with mechanical activation intervals derived from ultrasound.
Main Results:
- Hemodynamic collapse (COLLAPSE) was associated with significantly shorter and more regular electrical activation intervals (ISI) compared to other conditions (P < 0.001).
- The minimum current for COLLAPSE (50 microA) was lower than the VF threshold (108+/-28 microA).
- Electrical and mechanical activation occurred at integer multiples of the AC stimulation period.
Conclusions:
- Hemodynamic collapse can be induced by rapid, regular electrical excitation at currents below the VF threshold.
- This finding highlights a critical safety concern for AC stimulation in cardiac interventions.
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