Pacing sequences
| Protocol | First 4 months | Second 4 months | Third 4 months |
|---|---|---|---|
| 1 | DDD | VVI | ODO |
| 2 | VVI | DDD | ODO |
| 3 | ODO | DDD | VVI |
| 4 | DDD | ODO | VVI |
| 5 | VVI | ODO | DDD |
| 6 | ODO | VVI | DDD |
DDD, dual chamber pacing with rate drop response; ODO, sensing only, no pacing; VVI, ventricular pacing with wide hysteresis.