Graeme Sloman

Prediction of sudden death by electrophysiologic studies in high risk patients surviving acute myocardial infarction.

Seventy patients surviving a myocardial infarction complicated by heart failure or arrhythmias, or both, were studied 7 to 20 days after the infarction. Twenty-four hour electrocardiographic ambulatory monitoring and intracardiac electrophysiologic studies were performed in each patient. Electrophysiologic studies included introduction of single right ventricular premature stimuli during sinus rhythm (70 patients), atrial pacing (35 patients) and ventricular pacing (70 patients) at a stimulating voltage of 2 V, with the use of higher stimulating voltages (up to 10 V), and double right ventricular premature stimuli in 33 patients and pacing at a second right ventricular site in 50 patients. A repetitive response was defined as two or more spontaneous ventricular depolarizations in response to the premature stimuli, with His bundle reentry and aberrant conduction of supraventricular impulses excluded by a His bundle recording. Repetitive responses were initiated in 20 patients, and 12 patients had responses that were either sustained ventricular tachycardia or self-terminating ventricular tachycardia of more than five complexes in duration. The finding of a repetitive response was not related to the occurrence of complex ventricular arrhythmias during ambulatory monitoring or in the coronary care unit. Five of the 12 patients with sustained or self-terminating responses of more than five complexes died during the 12 month follow-up period, 4 suddenly, and these responses were significantly associated with late sudden death (p less than 0.05), because only 1 of 25 patients with responses of fewer than five complexes or no response to maximal provocation died suddenly. It is concluded that induced responses of more than five complexes in duration may be an important indicator of a potentially reversible risk of sudden death after myocardial infarction.

PROPRANOLOL (INDERAL) IN PERSISTENT VENTRICULAR FIBRILLATION.

Pronethalol, a beta-adrenergic-blocking agent, has been used successfully in the treatment of supraventricular and ventricular arrhythmias (Stock and Dale, 1963; Grandjean and Rivier, 1963; Johnstone, 1964; Payne and Senfield, 1964). Vaughan Williams and Sekiya (1963) demonstrated that ventricular fibrillation produced in guinea-pigs by the infusion of ouabain could be prevented and controlled by beta-sympathetic blockade. This finding raised the possibility of the use of beta-adrenergicblocking agents in the treatment of the arrhythmias accompanying digitalis intoxication and in the prevention and control of ventricular fibrillation. Pronethalol was associated with the occurrence of thymic tumours in experimental animals, and it has since been replaced by propranolol (Inderal; 1-isopropylamino-3-(l-naphthyloxy)propan-2-ol hydrochloride), which has the same beta-sympathetic-blocking action but a greatly increased therapeutic ratio (Hamer et al., 1964; Srivastava et al., 1964; Prichard and Gillam, 1964; Chamberlain and Howard, 1964). We here report our experience in treating three patients with recurrent ventricular fibrillation, using propranolol.

Arrhythmias on exercise in patients with abnormalities of the posterior leaflet of the mitral valve

Abstract Twenty patients with the late systolic murmur-non-ejection click syndrome were exercised on a treadmill with continuous monitoring of the ECG. Eight patients exhibited ectopic activity at rest; exercise increased the abnormalities in 16 during or after exercise. Ventricular ectopic beats were frequent during exercise in 7 patients, atrial fibrillation occurred in 1, while flat ST segment depression of 1 mm. or more developed in 12 of the patients. These changes associated with exercise may indicate a cardiomyopathy associated with the prolapsed valve leaflet which may be linked with the occurrence of sudden death reported in this syndrome. Exercise stress appears to unmask myocardial irritability and should be considered in all patients presenting with this syndrome. Therapy may then be prescribed for those patients developing significant arrhythmias or conduction changes.

Mortality Reduction in a Coronary Care Unit

reveals an overall mortality rate of 5.7%. Two hundred and fifty patients are in normal health leading active lives. Con version to total ileostomy has been necessary in 14 cases (5% of operative survivors), because of the development of carcinoma of the rectum, stricture, incontinence, or other complications. The indications for this type of operation in acute and chronic diseases are discussed. It is suggested that the best results in the surgical management of patients with ulcerative colitis can be achieved only in special centres. Acknowledgement is due to Lille Chirurgical for permission to publish Figs. 2 and 3.

Effect on survival after myocardial infarction of long-term treatment with phenytoin.

A prospective, randomised, open trial was performed in 150 patients to test for any beneficial effects on 2-year mortality of long-term antiarrhythmic therapy with phenytoin in patients with acute myocardial infarction. Patients were stratified according to age, sex, past history of myocardial infarction, and the presence of absence of electrical or mechanical complications in the course of acute infarction. They were then randomised to treatment or control groups (74 v. 76). The former received phenytoin in doses aimed at maintaining plasma phenytoin levels between 40 and 80 mumol/litre. All patients entered the study before discharge from the coronary care ward. Plasma phenytoin levels were in the therapeutic range in between 51 and 75 per cent of subjects at any follow up visit. There were 19 withdrawals from the treatment group, 10 of which were the result of side effects. There were 5 withdrawals from the control group. According to the original intention to treat, there were 18 deaths at 2 years in the treatment group and 14 deaths in the control group. There was no reduction in the incidence of instantaneous or sudden deaths. Deaths on treatment were not associated with a low phenytoin plasma level. Phenytoin treatment showed no beneficial effects on mortality and was associated with a high incidence of side effects.

Histopathology of Heart Block Complicating Acute Myocardial Infarction Correlation with the His Bundle Electrogram

Histopathological studies of the conduction system were related to His bundle electrogram recordings in seven patients with acute myocardial infarction and atrioventricular (A-V) conduction disturbances. The three patients with inferior infarctions had normal width QRS complexes and delay or block of the impulses above the His bundle. Recent ischemic changes were present in the A-V node in two cases and in the distal conduction system in all three cases. In the four patients with antero-septal infarction and right bundle branch block (RBBB), either the H-V interval was prolonged or block was present below the H spike. The A-H interval was normal in each of these cases, and the A-V node was not affected by the recent infarction. The right bundle branch was involved in all four of these cases and two patients also had involvement of the left bundle branch. In general there was a good correlation between the sites of heart block as defined by the His bundle electrogram and the histopathological analysis of the cardiac conduction system.

Bundle-branch block in acute myocardial infarction.

Bundle-branch block was present in 41 out of 415 patients admitted to a coronary care unit with acute myocardial infarction and was associated with more severe clinical infarction and an overall mortality of 56%. It is probable that permanent bundle-branch block develops soon after infarction and that most of the patients with permanent block have had clinically severe infarction. Bundle-branch block developing during observation is usually transient, and the later it develops the sooner it resolves. Analysis of the arrhythmias and clinical course of the patients suggests that those with bundle-branch block and shock and those in whom bundle-branch block is present on admission may benefit from the use of a demand pacemaker attached to a transvenous pacemaker catheter, though the dividends of pacing may be small and the risks of the procedure significant. Post-mortem examination of 17 hearts showed extensive infarction, usually involving the septum, and severe coronary artery disease.

Survival after resuscitation from cardiac arrest in acute myocardial infarction

Abstract The results of attempted resuscitation of 38 patients who suffered cardiac arrest after acute myocardial infarction are presented. Resuscitation was successful in 17 patients, with limited survival in 9, and long-term survival in 8. Ventricular fibrillation was responsible for cardiac arrest in 24 patients, including the 8 long-term survivors. Asystole was responsible in 14 patients, with no long-term survivors. Of the 8 long-term survivors, 7 showed no evidence of circulatory embarrassment prior to cardiac arrest. The conclusion is that immediate resuscitation will usually lead to long-term survival in those patients with myocardial infarction in whom circulatory embarrassment is not evident prior to cardiac arrest. Failure of resuscitation can be predicted in most cases in which hypotension, cardiac failure, or cardiogenic shock precede cardiac arrest. Special units, to which patients with acute myocardial infarction should be admitted, for monitoring, management, and resuscitation are required in all large general hospitals.

Sudden Death in Hospital after Discharge from Coronary Care Unit

In a group of 339 patients with acute myocardial infarction treated in a coronary care unit, 273 left the unit while improving and were expected to leave hospital alive; 23 had a cardiac arrest or died suddenly while still in hospital—17 died immediately or after temporary resuscitation and six were resuscitated to leave hospital alive. Ventricular fibrillation was found in 13 of the 20 patients attended by the cardiac arrest team. The incidents were scattered from the 4th to the 24th day after the onset of infarction. Risk factors in these “late sudden death” patients were compared with the 250 patients who left the unit while improving and did not die or suffer cardiac arrest. The patients susceptible to late sudden death were characterized early in their hospital course by the findings of severe, predominantly anterior infarction, left ventricular failure, persistent sinus tachycardia, and frequent ventricular arrhythmias. It is suggested that such patients be chosen for prolonged observation in a second-stage coronary care unit.

The Small‐Tined Pacemaker Lead—Absence of Dislodgement

The Medtronic 6961 unipolar transvenous ventricular lead has four symmetrically placed, small tines that protrude backward just proximal to the tip, and are designed to become entrapped beneath or between right ventricular trabeculae. One hundred leads were implanted. Initially, the leads were more difficult to position at the right ventricular apex as the tines tended lo anchor on intracardiac structures. This was overcome by rotating the lead. The time of negotiating the Jead from right atrium to right ventricular apex averaged 3.1 minutes for all leads. The first 20 procedures averaged 4.2 minutes and the last 20 averaged 2.1 minutes. In this latter group, 11 of the 20 passages took 60 seconds or less. Once adequate positioning was obtained, the lead was retracted using slight tension to demonstrate tip entrapment. There were no lead dislodgements. Eight deaths occurred following institution of pacing and lead dislodgement was not detected in any of these cases. Four patients had complications associated with pacing, two transient diaphragmatic pacing not requiring reoperation, one right ventricular perforation and one raised threshold with intermittent failure of pacing without lead perforation or dislodgement. Because of the absence of dislodgement, this lead appears to have significant advantages over conventional leads.