Biological pacemaker created by percutaneous gene delivery via venous catheters in a porcine model of complete heart block.

BACKGROUND

Pacemaker-dependent patients with device infection require temporary pacing while the infection is treated. External transthoracic pacing is painful and variably effective, while temporary pacing leads are susceptible to superinfection.

OBJECTIVE

To create a biological pacemaker delivered via venous catheters in a porcine model of complete heart block, providing a temporary alternative/adjunct to external pacing devices without additional indwelling hardware.

METHODS

Complete atrioventricular (AV) nodal block was induced in pigs by radiofrequency ablation after the implantation of a single-chamber electronic pacemaker to maintain a ventricular backup rate of 50 beats/min. An adenoviral vector cocktail (K(AAA) + H2), expressing dominant-negative inward rectifier potassium channel (Kir2.1AAA) and hyperpolarization-activated cation channel (HCN2) genes, was injected into the AV junctional region via a NOGA Myostar catheter advanced through the femoral vein.

RESULTS

Animals injected with K(AAA) + H2 maintained a physiologically relevant ventricular rate of 93.5 ± 7 beats/min (n = 4) compared with control animals (average rate, 59.4 ± 4 beats/min; n = 6 at day 7 postinjection; P <.05). Backup electronic pacemaker utilization decreased by almost 4-fold in the K(AAA) + H2 group compared with the control (P <.05), an effect maintained for the entire 14-day window. In contrast to the efficacy of gene delivery into the AV junctional region, open-chest, direct injection of K(AAA) + H2 (or its individual vectors) into the ventricular myocardium failed to elicit significant pacemaker activity.

CONCLUSIONS

The right-sided delivery of K(AAA) + H2 to the AV junctional region provided physiologically relevant biological pacing over a 14-day period. Our approach may provide temporary, bridge-to-device pacing for the effective clearance of infection prior to the reimplantation of a definitive electronic pacemaker.