Harold Siddons

Septicemia in patients with an endocardial pacemaker

The records of 1,235 consecutive patients treated with long-term pacing by the endocardial route between 1964 and 1977 were analyzed to determine the incidence, mechanism, course and treatment of septicemia. Septicemia developed in 12 patients (1 percent), and Staphylococcus aureus was isolated from the blood culture in 10. All patients were treated with the usual prolonged course of bactericidal drugs. Treatment was successful in only two of the seven patients whose endocardial pacing system was left in place; in three of the seven the septicemia recurred, necessitating removal of the endocardial system, and two of these patients died. In the remaining four patients the endocardial wire was promptly withdrawn, with use of a thoracotomy when necessary, and an epicardial system inserted; all of these patients survived. This is the treatment of choice.

Aetiology of chronic heart block. A clinico-pathological correlation in 65 cases.

The cause of chronic heart block is often obscure on clinical grounds alone. Consequently there is considerable difficulty in deciding the prognosis of a patient with complete heart block even with successful artificial pacing. Coronary artery disease has been generally accepted in the past as the predominant cause of heart block, and Penton, Miller, and Levine (1956) estimated an incidence of 43 per *cent, Wright et al. (1956) one of 69 per cent, and Friedberg, Donoso, and Stein (1964) one of 48 per cent. These estimates were based on clinical and electrocardiographic evidence. Other studies suggested that areas of fibrosis involving the conducting system, either alone or in association with scattered areas offibrosis in the myocardium, were responsible for heart block (Lenegre and Moreau, 1963; Lev, 1964; Zoob and Smith, 1963). In one of our earlier patients, the only cardiac abnormality was fibrotic lesions confined to the conducting tissue, a surprising finding as severe coronary disease had been suspected, and this made us realize the importance of developing techniques for long-term artificial pacing (Portal et al., 1962). With the continuing improvement of these techniques, the prognosis of a patient will become more dependent on the cause of the heart block. In an effort to improve the clinical diagnosis of the underlying cause of heart block, a retrospective survey was carried out in 65 consecutive patients with chronic heart block who had come to necropsy during the past 3 years.

THE MANAGEMENT OF HEART BLOCK

In 1952, Zoll described a technique for artificial pacing of the heart. The method employed electrodes placed on the chest wall and electrical impulses of 2 msec. duration at 25-150 volts. Although this indirect technique proved successful in resuscitating and temporarily maintaining life in patients with Stokes-Adams attacks due to asystole, the high voltage required produced skin burns and painful contractions of the muscles of the thorax. Other methods were developed for the direct stimulation of the myocardium with low voltages, and permanent pacing of the heart with small pacemakers is now routinely performed (Bellet et al., 1960; Chardack, Gage, and Greatbatch, 1961; Elmqvist and Senning, 1960; Davies, 1962; Kahn et al., 1960; Landegren, 1962; Lillehei et al., 1960; Stephenson et al., 1959; Weirich et al., 1958; Zoll et al., 1961). Reports on the success of long-term pacing by many different systems have now appeared (Furman et al., 1961; Levitsky et al., 1962; Siddons, 1963). While artificial pacemaking is life saving and permits a return to a normal way of life in most cases, numerous problems have arisen in the maintenance of this artificial system. It is for this reason that we propose to describe our experiences in the management of heart block over the past four years at St. Georges Hospital, of which some have been previously reported by Portal et al. (1962) and Siddons (1963).

Prognosis of patients paced for chronic atrioventricular block.

Between the years 1960 and 1974, 839 patients were paced for chronic complete atrioventricular block. Analysis of survival compared with the general population showed that 170 deaths were expected according to standard mortality tables and 288 actually occurred, giving a ratio of actual to expected deaths of 1.7:1. Patients with a definite history of myocardial infarction showed a higher than average mortality when paced. Mortality was not influenced whether heart was constant or intermittent, whether the ventricular rate was below or above 40/minutes, or whether QRS duration was greater or less than 0.1 second. Analysis of the age groups paced disclosed the most important correlations. Between the ages of 80 and 89 years paced patients could expect to survive as long as other of the same age without heart block. There was, however, a very high ratio of 4.5:1 for 90 patients in the age group 50 to 59 years. The reason for the high mortality ratio was uncertain but it may have been the result of a greater incidence of underlying coronary artery disease.

Unsuspected coronary artery disease as cause of chronic atrioventricular block in middle age.

Attention has recently been drawn to the relatively poor prognosis of middle aged patients paced for chronic atrioventricular block when age-linked expectation of life is taken into account, and it has been suggested that this may be the result of underlying coronary artery disease, despite the absence of symptoms to suggest this. It was the purpose of this study to determine the incidence of unsuspected coronary artery disease in middle aged patients presenting with chronic atrioventricular block. Studies were made on a consecutive series of 30 patients aged 45 to 65 (mean age 56 years) with chronic atrioventricular disease who had been referred for pacing. Patients presenting with acute myocardial infarction or angina or with sinuatrial disease without atrioventricular disease were excluded. Coronary arteriography disclosed the presence of severe coronary artery disease in 13 patients. Of the remaining 17 patients, four had congestive cardiomyopathy, two had hypertrophic cardiomyopathy, one had aortic stenosis, and in 10 patients the aetiology of the heart block was unknown. Myocardial revascularisation was undertaken in six patients with paroxysmal atrioventricular block caused by coronary artery disease. Operation did not result in any sustained improvement in atrioventricular conduction.

Transvenous long-term pacing with an external pacemaker. What are the risks?

Externalized endocardial electrodes were used for pacing 138 patients for periods of one month to 12 years. In the 416 patient/years of pacing by this method, 13 septicemias occurred.

Prediction of battery depletion in implanted pacemakers

By the use of a measuring oscilloscope and the standard electrocardiogram limb leads the degree of battery depletion in an implanted pacemaker can be estimated. A formula based on readings obtained by this means has been used to determine when Devices fixed rate pacemakers should be removed. Laboratory tests show that 90% of their useful life is obtained by this means and it proved possible to extend the period of implantation from an arbitrary 24 months to 25 to 34 months without failure from battery depletion.

MANAGEMENT OF HEART-BLOCK

Syncope or dizzy spells with near syncope are common in the elderly. Whether or not there is gross bradycardia, such symptoms require, among other investigations, an ECG. If the ECG taken between attacks shows complete block, the likelihood is that the syncope (Stokes-Adams attack) is due to a temporary cessation of the cardiac rhythm. Asystole, ventricular tachycardia, or ventricular fibrillation may each occur. Such attacks can be reliably prevented only by artificial pacing. Although long-acting isoprenaline has often been used, there is little or no evidence that any drug therapy is effective. If the ECG taken between syncopal attacks shows lesser degrees of block or bundle branch block, it is highly probable that the syncope is cardiogenic, although many of these rhythms without syncope are relatively benign. Syncope from cessation of the heartbeat is exceptional when the ECG between attacks shows no conduction defect. Syncopal attacks associated with block are usually both infrequent and unpredictable; thus, continuous monitoring to determine the rhythm during an attack is usually impractical.