Permanent pacing

Prevalence, circumstances, mechanisms, and risk stratification of sudden cardiac death in unipolar single-chamber ventricular pacing

BACKGROUND

Permanent cardiac pacing is well established for the improvement of prognosis and quality of life in patients with severe bradycardia. However, sudden cardiac death still remains an unresolved problem, as it occurs in approximately 20-30% of paced patients. This 2-year follow-up study was directed at prospectively assessing prevalence, circumstances, and mechanisms of sudden death in 2,021 permanently paced patients.

METHODS AND RESULTS

During the observation period, 220 patients (11%) died (mean pacing interval, 50.5 +/- 7 months). Lethal cerebrovascular events in 66 of 220 patients (30%) and sudden death in 49 of 220 patients (23%) were the two most frequently reported modes of death. Nonsudden (first year, 20%; subsequent years, 6.9%; p less than 0.01) and sudden death mortality rate (4% versus 1.8%, p less than 0.05) were highest during the first year. Mortality was unrelated to the patient's activity status at the time of death. Sudden cardiac death occurred more often in male patients (increased risk, 1.7 versus female patients; p less than 0.001) and patients younger than 60 years of age (5.2 versus patients older than 60 years, p less than 0.001). Patients with severe bradycardia (sudden death rate, 28%), severe atrioventricular block (25%), or atrial fibrillation with low ventricular rate (25%) before pacemaker implantation were more likely to suffer from sudden cardiac death than patients with previous syncopal attacks (sudden death rate, 15%) or sick sinus syndrome (17%). The highest incidence of sudden death was observed in patients with bifascicular and trifascicular bundle branch block. In this group, 35% of patients died suddenly during the follow-up period compared with 18% of patients without bundle branch block. In a subsequent study in 90 consecutive patients with various types of bundle branch block, undersensing of up to 13% of ectopic ventricular beats occurred in patients with bifascicular block. Pacing-induced tachyarrhythmias and ventricular fibrillation were documented in 10% of undersensed ectopic ventricular beats as well as in the setting of atrial fibrillation associated with ventricular arrhythmias.

CONCLUSIONS

Young age, male sex, and a severely diseased heart indicated by the presence of bifascicular and trifascicular bundle branch block are the strongest predictive clinical parameters for sudden cardiac death, especially in the first year after pacemaker implantation.

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

Dual chamber pacing aborts vasovagal syncope induced by head-up 60 degrees tilt

To determine if pacing might prevent syncope in cardioinhibitory 'Malignant Vasovagal Syndrome' (also known as 'Neurally-Mediated Bradycardia/Hypotension'), a study of dual chamber pacing during head-up 60 degrees tilt was undertaken. Paired invasive tilts were performed in 10 patients who had a history of recurrent syncope, normal routine investigations including electrophysiological study and prior tilt-induced vasovagal syncope. Vasovagal reactions of identical severity were produced by prolonged 60 degrees head-up tilt on consecutive days in seven out of 10 patients. On day 2, without pacing, seven patients had tilt-induced vasovagal reactions and six became syncopal during the reaction. On day 3, with temporary DVI pacing with rate hysteresis, seven patients had tilt-induced vasovagal reactions and 1 patient was syncopal. Syncope was aborted in the other five patients. DVI pacing significantly improved cardiac index (CI) (one +/- 0.2 to 1.6 +/- 0.3 L/min/m2, P less than 0.01) and mean arterial blood pressure (MABP) (30 +/- 11 to 48 +/- 12 mmHg, P less than 0.01) during vasovagal reactions on day 3 compared with day 2. The mean period of time that patients could tolerate in the tilted position after the onset of the tilt-induced vasovagal reaction was significantly prolonged by pacing from 0.9 +/- 1.2 to 3.2 +/- 1.6 min (P less than 0.01). Dual chamber pacing may abort syncope in 85% of patients with cardioinhibitory malignant vasovagal syndrome. Pacing may prolong consciousness sufficiently during a vasovagal reaction to allow injury to be avoided.

Clinical problems in patients with prosthetic heart valves

Information from the UK Heart Valve Registry, which was established in 1986 and receives data from all centres in the National Health Service, shows that more than 5,000 artificial heart valves are implanted each year in Britain and that almost two-thirds of these are mechanical. This article is intended as a practical outline of the clinical problems and complications which may occur.

Recurrent symptoms after ventricular pacing in unexplained syncope

We report clinical and hemodynamic data in two cases of recurrent syncope. Both patients received permanent demand ventricular pacing (VVI) for unexplained syncope. Both patients experienced recurrent syncope after pacemaker implantation. They later underwent 60 degrees head-up tilt testing, initially noninvasively and then with hemodynamic profile. A vasovagal response to tilt occurred with bradycardia and was complicated by the onset of ventricular pacing and retrograde atrioventricular conduction (RAVC) with hemodynamic deterioration and rapid reproduction of syncope. Limited intracardiac electrophysiological study (EPS) excluded atrioventricular (AV) conduction disease, sinus node disease, and carotid sinus syndrome, and confirmed RAVC. Both patients were upgraded to dual chamber pacing, DDI mode, with 50/80 rate hysteresis. One patient was asymptomatic at repeat tilt testing; the other experienced continued symptoms due to the vasodepressor component of vasovagal syncope. Cardiac pacing alone is ineffective treatment for this phenomenon, and no proven therapy is presently available. Ventricular pacing applied to patients with unexplained syncope may lead to an increase in or continuation of symptoms rather than an amelioration. There is a need for full investigation of such patients, which must include tilt testing, to allow for the most accurate diagnosis possible and guide the most appropriate therapy.

Anaesthetic management of the patient with a permanent pacemaker

Over 25,000 people in Britain now have pacemakers, and the number is increasing steadily. Anaesthetists encounter patients with pacemakers regularly. Knowledge about the increasingly wide range of pacemakers available is necessary to ensure safe management of these patients, many of whom are frail and elderly. This review outlines the indications for permanent pacing, the types of pacemaker used and the assessment and management of pacemaker patients for anaesthesia.