Parallel to significant functional improvement and echocardiographic reverse remodeling and resynchronization, our data indicate that CRT induces favorable changes in the neurohumoral system.

We describe a case of potentially fatal undersensing of VF by a third generation ICD with predetermined automatic gain control. In this patient, ventricular sensing was optimal, as R wave amplitudes during sinus rhythm were at least 16 mV. Cyclical, high amplitude signals during VF elevated the sensing floor to such an extent that complete undersensing of subsequent lower amplitude local electrograms occurred. This led to bradypacing and complete ICD therapy failure. Therefore, high R wave amplitudes during sinus rhythm do not warrant flawless sensing during VF.

No abstract

After 1 month of individual optimization of rate response pacemakers, exercise capacity was improved and maximum HR increased, although QOL remained unchanged. Accessible pacemaker sensor algorithms are mandatory for individual optimization.

The occasionally observed progressive heart failure after right ventricular pacing following His-bundle ablation can be reversed by upgrading to VVIR biventricular pacing and under these circumstances upgrading should be considered.