We have used DDD 60 bpm with AV stimulated interval of 150 msec. What is your common experience?
Tachy-programming: HCM patients are at risk of VF, therefore create a VF-detection interval of 250-280ms with long detection-time in order to avoid inappropriate shocks due to AF. A monitor-zone is possible to detect rare VT-episodes at 320ms.
Brady-programming: data are poor for treatment of HOCM with pacing in RVA. If drug-treatment failed of course it is an option. Dual chamber pacing is necessary for AV-synchronization. AV-intervals must be programmed shorter than intrinsic AV-conduction and rate-dependence of AV-intervals should be activated. E.g.: PAV 150ms, SAV 120ms or even shorter. It can be necessary to slow intrinsic AV-conduction with drugs (Ca-antagonists, beta blockers) so that pacing in RVA is possible. Perform echo with evaluation of e- and a-waves at transmitral doppler.
Lower rate limit should be programmed to 40 bpm to avoid stimulation at rest.
Agree with the above data, in patients with a restrictive component it is important to avoid too short AV intervals and high rates to allow proper filling of the ventricle.
Echocardiographic evaluation and an exercise test might help to set adequate values in patients individually.
How safe are we with DDD pacing in these patients ? I think there is possibility of pacing-induced cardiomyopathy maybe more so then patients with normal heart. We need to have some studies showing that AP VP is safe in these patients. But despite that I agree that in practice this is still an option.
In our hospital the preferred mode is DDD with AV delays, usually around 170 / 150 ms (selected with echo transmitral flow) to allow proper filling. Since the data of pacing to avoid obstruction is not very strong we prefer as little pacing as possible. VF/VT zone with long detection times since this patients experience a lot of AF. We feel that individualised approach in HCM patients is the best.
In our institution we attempt to have minimal ventricular pacing with reduced rates down to 40/min. DDD with Long AV delay and 1 zone for ventricular tachycardia / VF treatment with ATP in VF zone with a long detection.
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