Abstract 13250: LV SV Using Admittance for Hemodynamically Unstable Arrhythmia Detection
Intro: Implantable cardioverter defibrillators (ICDs) currently use only intra-cardiac ECG to decide when to prevent sudden cardiac death. This is incomplete information since 1/3 of patients experience an “inappropriate” shock within the first 1-3 years of receiving the implant. Receiving a shock is associated with increased mortality. In contrast, physicians determine whether to shock a patient by determining if the arrhythmia is hemodynamically unstable or stable. An unstable arrhythmia is identified by decreased forward stroke volume (SV) and resultant low blood pressure. It would be ideal to have SV available to the generator to assist in the determination of hemodynamic stability.
Method: Canines (n=12) were implanted with LV endocardial crystals that determined instantaneous LV volume. Pacing leads were inserted through the right jugular vein into the posterolateral left coronary vein (LCV) and RV septum. A complex admittance measurement was determined that spanned from the RV to the LCV (Figure A). Real and imaginary components of impedance were used to separate the myocardial and blood components using a series circuit model of the LV. SV was altered with pacing and dopamine infusion.
Results: Simulated ventricular tachycardia measurements show that instantaneous blood conductance (Gb) tracks acute changes in LV volume more consistently than admittance magnitude ([[Unable to Display Character: |]]Y[[Unable to Display Character: |]], without removal of muscle signal) as shown in Figure B. Results for RV to LCV measurements show that SV and ΔGb have a significant relation (p < 0.001) with a mean slope of 6.54 ± 0.87 mL / mS. Using a linear fixed-effects model, [[Unable to Display Character: ▵]]Gb was more significant than Δ|Y| (p < 0.001 vs. p < 0.067 resp.).
Conclusion: Monitoring of LV SV is possible using the admittance method with Bi-V pacing leads. The technique could be piggybacked onto existing pacemaker technology to help determine if shocking is necessary during rapid arrhythmias and inappropriate double sensing to reduce false positive shocks.
- Implantable cardioconvert defibrillator
- Arrhythmias, treatment of
- Stroke volume
- Ventricular tachycardia
- Bi-ventricular pacing
- © 2012 by American Heart Association, Inc.