Is Mobitz type I atrioventricular block benign in adults?

OBJECTIVE: To assess the need for pacing in adults with chronic Mobitz type I second degree atrioventricular block (Mobitz I). DESIGN: Prospective study. SETTING: District general hospital. PATIENTS: 147 subjects aged > or = 20 years (age cohorts 20-44, 45-64, 65-79, and > or = 80) with chronic Mobitz I without second degree Mobitz II or third degree (higher degree) block on entry, seen from 1968 to 1993 and followed up to 30 June 1997. Sixty four had organic heart disease. The presence of symptomatic bradycardia was defined as highly likely in 47 patients (class 1); probable in 14 (class 2); and absent in 86 (class 3). INTERVENTIONS: Pacemakers were implanted in 90 patients for the following indications: symptoms in 74 and prophylaxis in 16. MAIN OUTCOME MEASURES: The main outcome measure was death, with conduction deterioration to higher degree block or symptomatic bradycardia the alternative measure. RESULTS: Five year survival to death was reduced in unpaced patients relative to that expected for the normal population (overall mean (SD) 53.5 (6.7)% v 68.6%, p < 0.001; class 3, 54.4 (7.3)% v 70.1%, p < 0.001). Paced patients fared better than unpaced (overall (mean (SD) five year survival 76.3 (4.5)% v 53.5 (6.7)%, p = 0.0014; class 3, 87.2 (5.4)% v 54.4 (7.3)%, p = 0.020; and organic heart disease, 68.2 (7.6)% v 44.0 (9.9)%, p < or = 0.0014). There were no deaths in the < 45 cohort. Survival to first outcome (main or alternative) was further reduced to 31.7 (5.0)% in 102 patients unpaced initially and 34.2 (5.7)% in class 3. Only the 20-44 cohort and patients with sinus arrhythmia had > 50% survival. CONCLUSION: Mobitz I block is not usually benign in patients > or = 45 years of age. Pacemaker implantation should be considered, even in the absence of symptomatic bradycardia or organic heart disease.

Assessment of QT dispersion in symptomatic patients with congenital long QT syndromes.

It has been suggested that QT dispersion recorded on the surface electrocardiogram may be a predictor of arrhythmic events in patients with congenital QT prolongation. To evaluate this, 9 patients (6 female, mean age 17.6 years) with congenital long QT syndromes, all of whom had syncope and documented torsades de pointes, were studied. Patients were studied off treatment and during therapy with beta-blocking agents. Three patients were also studied after left stellate ganglionectomy. An age-matched control group was also studied. Good quality 12-lead electrocardiograms were recorded from all patients. For each lead, QT and RR intervals were measured, and QTc value was calculated. QT and QTc dispersions were calculated for each patient. Patients had a significantly longer mean QT interval compared with that of the control group (450 +/- 100 vs 359 +/- 63 ms; p = 0.015) at similar mean RR intervals (736 +/- 231 vs 783 +/- 289 ms), with a longer mean QTc value (0.53 +/- 0.08 vs 0.41 +/- 0.02 s1/2; p = 0.004). Patients also had longer QT and QTc dispersions compared with those of the control group (110 +/- 45 vs 43 +/- 12 ms [p = 0.004], and 0.108 +/- 0.03 vs 0.05 +/- 0.02 s1/2 [p = 0.002], respectively). QT and QTc dispersions on and off beta-blocking agents were not significantly different. Comparing patients with frequent and those with infrequent symptoms, there was no difference in QT or QTc dispersion either off treatment or during therapy with beta-blocking agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical trials of a dual-sensor diagnostic pacemaker.

The results of clinical trials of a dual-sensor diagnostic pacemaker are described. The system monitors and records intraventricular electrical and pressure waveforms using a special lead incorporating bipolar electrodes together with a piezoelectric pressure transducer. The recorded waveforms, which are shown in conjunction with Holter recordings made simultaneously, demonstrate the value of pressure measurements and illustrate several cardiac events, including an ECG pause, bradycardia, a pressure pause, ectopic beats and tachycardia. The pacing function of the device is shown and capture is demonstrated.

A dual-sensor diagnostic pacemaker for ambulatory cardiac monitoring.

Unexplained blackouts are a very common medical problem. Some patients presenting themselves at hospital with such symptoms have underlying bradycardia or extreme tachycardia with a profound decrease in cardiac output. Modern treatment of these patients may be highly effective but accurate diagnosis of their exact condition may be needed. A novel ambulatory dual-sensor diagnostic pacemaker has been developed to meet this requirement. The device monitors intracardiac ECG and intraventricular pressure through a special lead introduced perveneously into the right ventricle and detects and counts events such as bradycardia, tachycardia, pauses in the electrical or pressure signals and electrical interference. Analogue recordings of the electrical and pressure waveforms of 16 of these events can be made during the operating period of 3 weeks and pacing is incorporated via a specially-adapted commercial pacemaker if a prolonged episode of bradycardia or a pause is sensed. The device forms part of a complete diagnostic system also incorporating a computer which is used to set up the parameters of the diagnostic pacemaker and to display and analyse the recorded data.

Survival in second degree atrioventricular block.

Two hundred and 14 patients with chronic second degree heart block were seen and followed up in the Devon Heart Block and Bradycardia Survey between 1968 and 1982. The patients were divided into three groups according to the type of block. In group 1 there were 77 patients with Mobitz type I block (mean age 69 years), in group 2, 86 patients with Mobitz type II block (mean age 74 years), and in group 3, 51 with 2:1 or 3:1 block (mean age 75 years). The five year survival was similar in all groups, being 57%, 61%, and 53% in groups 1, 2, and 3 respectively. The presence or absence of bundle branch block did not appear to influence prognosis. In particular, patients in group 1 without bundle branch block did not fare any better than those in group 2 both with and without bundle branch block. One hundred and three of the patients were fitted with pacemakers, the proportion being greatest in group 2. In each group a significantly larger number of paced patients survived than unpaced. The five year survival for all the paced patients in the study was 78% compared with 41% for the unpaced. Since the paced patients were slightly younger than the unpaced two age matched groups of 74 patients each were selected from the paced and unpaced patients, but the five year survival of those paced was still significantly better. It is concluded that in the patients in the present study chronic Mobitz type I block has a similar prognosis to that of Mobitz type II block. Unpaced patients with both types did very badly, whereas those fitted with pacemakers had a five year survival similar to that expected for the normal population. These results refute the benign reputation of chronic Mobitz type I block and imply that patients with this condition should be considered for pacemaker implantation on similar criteria to those adopted for patients with higher degrees of block.

Unexplained syncope--a diagnostic pacemaker?

We describe our initial experience with a pacemaker which performs the dual function of registering episodes of cardiac arrest and pacing the heart when necessary. The apparatus has a prolonged escape interval (2.30-2.65 seconds) and is capable of counting up to 128 "events." Twenty-five patients complaining of infrequent episodes of loss of consciousness have been studied. Blackouts ceased and episodes of ventricular standstill were recorded in 14 cases; the unit helped to establish a non-cardiac etiology for the attacks in two cases. It is suggested that a bradycardia-recording facility incorporated into a programmable pacemaker would provide a much needed tool in the diagnosis and management of patients with infrequent episodes of loss of consciousness in whom a cardiac mechanism is suspected but unproven.