Biomedical subjects
Publications and source records attributed to B M van Gelder.
This case report describes a patient with heart failure in whom a biventricular pacing system was successfully implanted. During control of the pacing system, three morphologies of the paced QRS complex could be elucidated. Right ventricular stimulation, biventricular stimulation, and biventricular pacing with additional stimulation from the anodal electrode of the right ventricular lead determined the morphologies.
A 45-year-old male had a VVI pacemaker implanted 20 years ago because of complete heart block. Because of perforation of the lead the pulse generator was removed after 4 weeks and a second lead was implanted from the contralateral side. Recently, the patient presented with symptoms of lightheadedness and syncope associated with prolonged pauses in the electrocardiogram. From the ECG, the ECG interpretation channel, and intracardiac electrogram telemetry, it was concluded that the VVI pacemaker was inhibited by P waves. The most likely explanation for this phenomenon was an insulation defect in the functioning lead caused by friction with the abandoned lead at the level of the high right atrium.
In patients with intermittent AV block and dual chamber pacemakers, a long paced AV interval of 200 msec or more can be selected to prolong pulse generator life (by avoiding the ventricular pace output) and to enable a more physiological and hemodynamically superior activation sequence. This case report describes the potential risks of programming a long paced AV interval in a patient with a DDDR pacemaker. T wave pacing, as described here, can occur if the conducted QRS complex is not sensed because it occurs during the ventricular blanking period (delivery of the atrial stimulus). This can be initiated by the mechanisms that induce apparent and actual P wave undersensing of the conducted QRS complex. In this case report apparent P wave undersensing and subsequent T wave pacing with ventricular capture (in a patient with intermittent AV block) occurred frequently during an exercise test done in the DDDR mode with a paced AV interval of 200 msec, according to the clinical evaluation protocol.
A 58-year-old man with an implanted minute ventilation rate adaptive DDD pacemaker underwent RF ablation of the AV junction because of symptomatic supraventricular tachyarrhythmias. Immediately after ablation, while the pacemaker was programmed in the DDDR mode, AV sequential pacing at upper rate was observed. After programming the pacing system to the DDD mode and repeated ablation, no abnormalities were observed. It was concluded that AV sequential upper rate pacing was caused by false interpretation of the RF current by the sensor measuring transthoracic impedance as an indicator for minute ventilation.
Two patients are described in whom an undeployed stent (1 Wiktor and 1 Palmaz-Schatz) was retained in the proximal segment of the right coronary artery during coronary angioplasty. In both cases the stent was caught by a technique using a second guidewire. The stent was removed in the first patient during bypass surgery; in the second patient it was removed from the femoral sheath.
The incidence of atrioventricular (AV) block and chronic atrial flutter/fibrillation was determined in 41 patients, mean age 62.2 years (22 to 88 years) who received atrial pacemakers before October 1980. The mean follow-up period was 12.3 years, range 11-14.4 years. Twenty-five patients suffered from bradycardia-tachycardia syndrome, 13 symptomatic bradycardia, and 3 bradycardia related ventricular tachycardia. At follow-up: 18 patients (44%) had permanent I-AV block; 11 patients had II-AV block, 9 patients (22%) transient Wenckebach block and 2 patients (5%) transient Mobitz block, all asymptomatic. The cumulative incidence of III-AV block was 1 (2.5%). Chronic atrial flutter/fibrillation occurred in 6 patients (15%), 5 were not pacemaker-dependent; 1 received a ventricular pacemaker. Seventeen patients died after a mean of 7 years (0.6-12.2 years). Cumulative survival rate of 58% for 14.4 years, did not differ from a matched cohort of the normal population. There were no pacemaker related deaths. We conclude that long-term atrial pacing was safe and effective. The incidence of III-AV block and chronic atrial flutter/fibrillation was low.
Two patients who had recently undergone pulse generator replacement in which an adapter had been used to connect a preexisting lead to a VS1 and IS1 3.2-mm connector presented with noncapture. The adapter set-screw was found to be protruding from the insulation sleeve to short-circuit with the pulse generator can. During episodes of noncapture the telementered impedance was < 100 ohms.
Wenckebach behavior of DDD pacemakers occurring when the P-P interval varies between the programmed upper rate interval and the total atrial refractory period is symmetrical in a sense that the pacemaker response during atrial rate acceleration is similar to the pacemaker response during atrial rate deceleration. This phenomenon can be observed in all patients with persistent AV block in whom a DDD pacemaker is implanted, during exercise testing when the spontaneous atrial rate exceeds the selected upper rate, i.e., the programmed upper rate interval. However, this phenomenon will not be observed in all patients with intermittent intact AV conduction during exercise. In this case report we describe a patient who showed an asymmetrical response during a bicycle exercise test. There was 1:1 atrial sensing ventricular pacing until the atrial rate exceeded the upper rate of 140 ppm, while atrial sensing was restored during recovery when the conducted sinus rhythm had decreased to 105 beats/min.