Resynchronization therapy optimization by intracardiac impedance.

Aims: For successful cardiac resynchronization therapy (CRT), an optimization of left ventricular (LV) lead position and stimulation timing is required. The feasibility of optimizing LV lead position, atrioventricular delay (AVd), and interventricular delay (VVd) in CRT using intracardiac impedance measurement was evaluated.

Methods And Results: Heart failure patients (n = 14, NYHA 13×III, 1×II, ejection fraction: 26 ± 6%, QRS: 165 ± 30 ms) were stimulated by AAI and biventricular (DDD-BiV) pacing in turn. Left ventricular lead site, AVd, and VVd were varied. An external pacemaker measured impedance, and a micromanometer catheter measured LV and aortic pressure. Left ventricular dP/dt(max), pulse pressure (PP), stroke volume (SV), end-systolic impedance (ESZ), and stroke impedance (SZ) were determined. Optimization results achieved by maximum increase in PP, SV, SZ, or ESZ were compared with the reference method (dP/dt(max) increase). Left ventricular lead site variation resulted in a mean optimal dP/dt(max) benefit of 18.2%. Lead site selection by SZ/PP/SV showed benefits of 17.4/17.9/17.2%, respectively. Atrioventricular delay optimization increased the optimal benefit to 22.1%, the methods ESZ/PP/SV achieved 20.1/20.8/19.4%. Interventricular delay optimization resulted in a benefit of 19.1/19.4/19.9% (SZ/PP/SV) with an optimum of 21.8%. The achieved benefit did not differ significantly between impedance, SV, and PP methods. A significant correlation between AVd values selected by dP/dt(max) and by the other methods was observed (r = 0.75/0.67/0.60 for ESZ/PP/SV).

Conclusion: The feasibility of optimizing LV lead site, AVd, and VVd by intracardiac impedance has been demonstrated for CRT patients with a similar performance as using SV and PP. Application of intracardiac impedance for automatic implant-based CRT optimization appears to be within reach.