Sue Jones

The right ventricular outflow tract as an alternative permanent pacing site : long-term follow-up

The long‐term characteristics of the right ventricular outflow tract have been assessed as an alternative permanent pacing site to the right ventricular apex. Thirty‐three consecutive patients requiring ventricular pacing were randomized to be paced from one of the two sites. Pacing was performed using a screw‐in lead, and a programmable pacemaker was used to facilitate threshold testing. There was no significant difference in the lead positioning time or any acute implant measurement (e.g., threshold at 0.5 msec 0.4 ± 0.2 V for both sites, P = 0.99). Chronic measurements were also comparable during follow‐up (mean 73 months) with a mean threshold at most recent follow‐up of 0.15 ± 0.2 msec (apex) and 0.13 ± 0.21 msec (outflow tract) at 5 V, P = 0,81, There was only one pacing related complication, a lead dislodgment (outflow tract) in a pacemaker twiddler. Overall, both sites were highly satisfactory.

Performance of Basic Ventricular Tachycardia Detection Algorithms in Implantable Cardioverter Defibrillators; Implications for Device Programming

Around 20% of patients with third generation implantable cardioverter defibrillators receive inappropriate therapy, usually triggered by atrial fibrillation. This is because the criteria used for ventricular tachycardia detection by current implantable cardioverter defibrillators are based on the analysis of a sequence of RR intervals and may be inappropriately satisfied by supraventricular tachyarrhythmias. Algorithms for ventricular tachycardia detection were challenged against the full RR interval sequences from 482 spontaneous episodes of atrial fibrillation and 260 spontaneous episodes of ventricular tachycardia to determine their ability to discriminate between the arrhythmias. The sensitivities and specificities of the algorithms were calculated over a wide range of programmable parameters. For a given window length and detection interval, the most stringent algorithms, that required all beats to be classified as “fast”, were more specific than those allowing a proportion of “normal” intervals, even after adjustment for differing sensitivity. These differences were less marked for faster tachycardias. Specificity increased with the detection window length to a limit of approximately 18 beats. We conclude that ventricular tachycardia is detected with the highest specificity if all beats in an analyzed sequence are required to be “fast” even after lengthening of the tachycardia detection interval to maintain sensitivity. Further improvement in algorithm performance may require the incorporation of criteria such as tachycardia onset and stability.

When Life-Saving Devices Terminate Life

This report describes proarrhythmia, a rare but in this case fatal complication of ICD therapy due to lead failure.

Transtelephonic Interrogation of the Implantable Cardioverter Defibrillator

Third generation implantable Cardioverter defibrillators (ICDs) have extensive memory capability to store data about the patients arrhythmias and the effect of therapies delivered by the ICD. However, this data has so far been accessible only when the patient attends the pacing clinic. Two Medtronic 9421 PCD(tm) TeletraceR transmitters have been used to interrogate Medtronic 7216A and 7217B PCD(tm)s at distances of up to 300 miles from our hospital and transmit the data to a 9420 PCD(tm) TeletraceR receiver. Successful transmission of data has been obtained on 50 occasions with 100% data concordance with repeat transmission. The system can reduce the number of unscheduled clinic visits, reduce delay in making a diagnosis following unexpected delivery of a shock therapy, and reassure patients about to be discharged following ICD implantation. The benefits are magnified where patients reside far away from the implanting center.

Day Case Permanent Pacing

We have previously reported our preliminary experience of day‐case permanent pacing in the United Kingdom. The study has now been extended to 50 patients with follow‐up of 22 ± 4 months. During the study period, all patients referred for permanent pacing, either to the senior author, or as in‐hospital transfers, were considered for the study. Forty two percent of patients considered fulfilled inclusion and exclusion criteria, resulting in a total of 50 patients being randomized either to day case or conventional in‐patient management. In the first month postimplantation, one patient in each group developed a complication requiring revision of system. Only one further pacing related complication occurred over the follow‐up period, percutaneous extrusion of a fixation sleeve with spontaneously healing of the wound. This was in a day‐case patient. Mean duration of in‐patient stay was 5.7 hours in day‐case patients, compared with 70.0 hours in those managed conventionally. Postimplantation local physician consultation rates were equal in both groups. Questionnaires were used to determine the relative acceptability to patients of the two management protocols; on a ten point score of acceptability, the mean score for both groups was 8.8. The difference in cost per patient using day‐case management was approximately £430 (

Rate-adaptive AV delay and exercise performance following cardiac resynchronization therapy

817). We conclude that day‐case permanent pacing in the United Kingdom is feasible, acceptable to patients, and has considerable economic benefits.

The Tricuspid Valve: An Unusual Site of Endocardial Pacemaker Lead Fracture

BACKGROUND Physiological shortening of the atrioventricular (AV) interval with increasing heart rate is well documented in normal human beings and is an established component of dual-chamber pacing for bradycardia. OBJECTIVES To assess the effect of exercise on optimal AV delay and the impact of a patient-specific rate-adaptive AV delay (RAAVD) on exercise capacity in patients with heart failure following cardiac resynchronization therapy. METHODS Phase 1: We performed iterative AV optimization at rest and exercise in 52 cardiac resynchronization therapy patients in atrial-sensed mode (mean age 71.6 ± 9.2 years, 25% females). Phase 2: Subsequently, 20 consecutive volunteers from this group (mean age 69.2 ± 9.6 years, 15% females) underwent cardiopulmonary exercise testing with RAAVD individually programmed ON (RAAVD-ON) or OFF (RAAVD-OFF). RESULTS Phase 1: In 94% of the patients, there was a marked reduction (mean 50%) in optimal AV delay with exercise. The optimal resting vs exercise AV delay was 114.2 ± 29 ms at a heart rate of 64.4 ± 7.1 beats/min vs 57 ± 31 ms at a heart rate of 103 ± 13 beats/min (P < .001). No patients required an increase in AV delay with exercise, and 3 (6%) showed no change. Phase 2: With RAAVD-ON, significantly better exercise times were achieved (8.7 ± 3.2 minutes) compared with RAAVD-OFF (7.9 ± 3.2 minutes; P = .003), and there was a significant improvement in Vo(2)max (RAAVD-ON 16.1 ± 4.0 vs RAAVD-OFF 14.9 ± 3.7 mL/(kg · min); P = .024). CONCLUSIONS There was a dramatic reduction in optimal AV delay with physiological exercise in the majority of this heart failure cardiac resynchronization therapy cohort. Replicating this physiological response with a programmable RAAVD translated into a 10% improvement in exercise capacity.

New Algorithms to Increase the Initial Rate Response in a Minute Volume Rate Adaptive Pacemaker

Two patients are described in this article who developed fractures of transvenous endocardial pacing leads at the point of passage across the tricuspid valve. In one case life‐threatening asystole occurred, emphasizing the potential seriousness of this complication.

Effect of atrioventricular optimization on circulating N-terminal pro brain natriuretic peptide following cardiac resynchronization therapy.

Background: Minute volume is a truly physiological sensor for rate adaptive pacing that correlates with metabolic expenditure throughout the range of physical activity. Criticism has centered on the slow initial response compared to less physiological sensors. A new algorithm, consisting of rate augmentation factor and programmable speed of response, has been incorporated in the 1206 META III pacemaker generator and was designed to improve the rate response at lower levels of exertions. Rate augmentation factor increases the programmed rate response factor by 3, 6, or 10 when set to low, medium, or high, respectively; this augmentation lasting to 50% of the maximum programmed rate. Response time can be programmed to medium or fast. Methods: Nine patients were studied during the first 3 minutes of an exercise test (Bruce protocol) in a single blind manner. The pacemaker generator was randomly programmed with rate augmentation factor at off, low, or high and speed of response to medium or fast, giving six possible combinations. Heart rates were recorded continuously for the duration of the test and until resting heart rate was achieved during recovery. The test was repeated until all six combinations had been tested. Results: During exercise significant differences appeared in response time from 30 seconds onward. Fast response and rate augmentation factor contributed to an improved rate response with greatest speed of response seen with fast response time and high rate augmentation factor. During recovery decreases in recovery time were seen with fast response time but rate augmentation factor prolonged recovery. Conclusions: Rate augmentation factor improves initial rate response in the early stages of exercise. Fast response gives an improved time to initial rate increase and shortens the duration of inappropriate postexercise tachycardia. These features improve the pattern of response of the minute ventilation sensor.

Signal averaged electrocardiography in infants and children with congenital heart disease

Following CRT, atrioventricular (AV) optimization is not routinely practised. To evaluate its clinical utility, we examined the effect of AV delay optimization on the prognostic biomarker NT‐proBNP.