Synchronized Low Energy Transvenous Cardioversion

Summary

In this study, we present one data on the use of trans venous cardioversion with synchronized shocks of low energies via a catheter electrode.

Animal studies: After a two hour occlusion of the LAD 35 dogs underwent programmed electrical stimulation. The induced VT was terminated with transvenous cardioversion using 10 F electrode catheters (Medtronic 6880) connected to a Medtronic 2316 cardioverter. This delivered a truncated exponential wave form, approximately 6 msec in duration with. increasing energy levels from 0.0005–2.5 J.

Of the 30 sustained VT, cycle length ⋝ 200 msec, 83% were terminated reproducibly by shocks of ⋜ 1.0 and 67% ⋜ 0.5 J.

For shocks introduced within the first 80% of the QRS, RVRs were rare and acceleration or degeneration to fibrillation never occurred. For shocks introduced within the vulnerable period (ST -T) energies of 0.008 J accelerated the VT or produced ventricular fibrillation.

Human studies were performed in 13 pts with coronary artery disease (55–72 y old). In II patients on one or more occasions the transvenous cardioversion terminated VT with energies of 0.025 to 2.0 J.

Including subthreshold attempts, a total of 196 shocks was delivered. Awake unsedated patients tolerated shocks of > 0.5 J without difficulty. Shocks< 0.5 J produced moderate skeletal muscle stimulation.

In the future the ideal implantable device will be capable of transvenous cardioversion and, if that fails or if ventricular fibrillation is precipitated, it will then deliver automatically a defibrillating shock.