Steroid-eluting epicardial leads have the same longevity as the conventional endocardial leads. Pacing and sensing thresholds were similar and did not change during follow-up. Therefore steroid-eluting epicardial pacing leads are a good alternative for endocardial leads in small children and in children with congenital heart disease.

Accurate detection of the spontaneous far-field ventricular signal may be used to determine the ventricular activation, and hence, the interval from atrial stimulus to the ventricular R wave (AR interval) using a standard atrial pacing lead. This can be useful in developing a physiological atrial rate responsive (AAIR) pacemaker and in further improving DDD(R) pacing algorithms. In order to better characterize the atrial sensed far-field ventricular signal, 200 consecutive patients undergoing pacemaker implantation were studied. The amplitude of the far-field ventricular signal was significantly smaller than that of the atrial deflection. In all recordings, the slew rate of the atrial deflection was larger than that of the far-field ventricular signal. Subdivision of the recordings by electrode position, pocket location, or QRS duration on the surface ECG resulted in significantly different signal characteristics. The amplitude and slew rate of the far-field ventricular signal were significantly smaller in bipolar versus unipolar sensing. Atrial sensed far-field ventricular recordings could also be obtained in the case of ventricular pacing. Our results indicate that accurate sensing of the far-field ventricular signal from an atrial pacing lead is conceivable in most patients. The different signal characteristics in relation to parameters, such as electrode position, sensing mode, and pocket location, may be useful in determining the optimal conditions for signal sensing.

During a 1-year follow-up, the stimulation parameters did not change significantly in the 16 patients without lead dislocations. Our standardized method appears to be feasible for follow-up of SCS. Moreover, SCS seems to be an effective adjuvant therapy for intractable angina, despite a relatively frequent dislocation of the electrode.

In a retrospective study we analyzed the unipolar endocardial evoked response signal (ERS) of 103 patients prior to pacemaker implantation. The objective of this study was to give a complete description of the ERS morphology and to evaluate influences on this morphology of both various electrode characteristics and pacing rate. In addition, spontaneous endocardial signals were studied. The results demonstrate that acute leads had both higher R wave and T wave amplitudes and a faster downslope of the T wave. In the acute leads those with porous titanium carbon coated tips showed a more pronounced T wave. Pacing rate influences the R wave amplitude and the stimulus to T wave interval. Both stimulus to maximum and stimulus to minimum T wave interval show an exponential correlation with the stimulus interval. The interval between maximum and minimum of the T wave and the absolute amplitude of T wave are not influenced by rate. Although there were significant correlations of the spontaneous endocardial signal with the ERS, the predictive value of the spontaneous signal for the ERS morphology is low. Prospective studies will be necessary to confirm the findings in this study.

At the age of 4 years, a total cavopulmonary connection was performed in a boy with a complex congenital heart defect. On addition, a DDDR pacemaker was implanted for sick sinus syndrome. Atrial and ventricular leads were epicardially placed at the left atrium and left ventricle. At the age of 10 years, a new epicardial ventricular lead was placed because of malfunction of the existing lead. At the same operation the pulse generator was replaced by a Medtronic Kappa DR 731. After replacement, the boy experienced episodes of phrenic nerve stimulation associated with feelings of discomfort. Holter recordings revealed ventricular stimulation from the atrial stimulus for 2 consecutive beats. This phenomenon repeated exactly every 3 hours and was caused by the automatic lead impedance measurement that used a 5-V, 1-ms stimulus output.