Louis Lemberg

His bundle electrograms in two cases of Wolff-Parkinson-White (pre-excitation) syndrome.

The catheter technic for recording the electrical activity of the specialized conducting system in the human heart showed in two patients studied that ventricular pre-excitation was apparently due to a bypass of the His bundle. Intermediate forms of WPW complexes appeared to be combination beats resulting from the activation of the ventricles through impulses traversing both the His bundle and accessory communications. Preferential iatrogenic activation of an intra-atrial (and perhaps even of an atrioventricular) tract appeared to occur in one of the patients. The patients with the WPW (pre-excitation) syndrome and long histories of paroxysmal arrhythmias were successfully treated with a combination of oral propranolol and implanted (transvenous) demand pacemaker.

Arrhythmias Related to Cardioversion

DC countershock abolished 92 of 101 episodes of atrial fibrillation in 86 patients, an incidence of 91 per cent. Supraventricular arrhythmias were not infrequent immediately after countershock. These were transient and did not complicate the procedure nor were they hazardous to the patient. On two occasions a slow atrioventricular nodal rhythm appeared followed by recurrence of atrial fibrillation a few hours later. Sinus node activity did not return in these patients. Ventricular tachycardia, fibrillation, or standstill did not occur in this series.The following arrhythmias were observed immediately after countershock but prior to the establishment of a regular sinus rhythm: atrioventricular dissociation, 12 times; passive atrioventricular nodal rhythm, five times; atrioventricular nodal tachycardia, five times; atrial flutter or tachycardia, four times.The conversion of fibrillation to flutter by countershock implies that the effect of the electric current was merely to shorten the length of the circulating wave, a phenomenon that can also be observed in the treatment of atrial fibrillation with quinidine.Disorders of rhythm, probably having a different mechanism, were also observed after countershock had established a regular sinus pacemaker. In the group not treated with quinidine prior to countershock (74 episodes) atrial extrasystoles were seen 26 times (35 per cent); atrioventricular nodal extrasystoles or escapes, 18 times (24.3 per cent); atrial flutter or tachycardia, six times (8.1 per cent); atrial fibrillation, eight times (18 per cent); atrioventricular nodal tachycardias, twice (2.6 per cent); and a bizarre, multifocal atrial arrhythmia, once (1.3 per cent). The arrhythmias considered to be responsible for the recurrence of atrial fibrillation and also the possible mechanisms involved were discussed.Pretreatment with quinidine was effective in reducing the incidence of arrhythmias occurringafter conversion (27 episodes), atrial extrasystoles six times (22 per cent), atrioventricular nodal extrasystoles or escapes six times (22 per cent); atrial flutter or tachycardia three times (11 per cent); atrial fibrillation once (3.7 per cent); and atrioventricular nodal tachycardia once (3.7 per cent).

The use of propranolol in arrhythmias complicating acute myocardial infarction

Abstract Propranolol was found to be a useful drug in the treatment of acute tachyarrhythmias. Forty-three episodes in 34 patients were successfully treated and sinus rhythm restored by using intravenous propranolol. All patients had recent myocardial infarctions complicated by mild, moderate, or severe left ventricular failure. It was judged that the net balance between the negative inotropic and chronotropic properties of propranolol on the myocardium resulted in a clinical improvement. A side effect in a few patients was sinus bradycardia which responded promptly to atropine sulfate or isoproterenol.

Significance of complete right bundle-branch block with right axis deviation in absence of right ventricular hypertrophy.

Complete right bundle-branch block with right axis deviation was seen in nine patients who did not have right ventricular hypertrophy, pulmonary disease, or extensive lateral myocardial infarction. Four patients had chronic block and five had acute myocardial infarction. This pattern was attributed to a coexisting block in the right branch and in the inferior division of the left branch. It frequently alternated with other significant intraventricular conduction defects, namely, complete left bundle-branch block, complete right bundle-branch block, and complete right bundle-branch block with block in the superior division of the left branch. A type II Mobitz block, evolving from a prolonged, or normal, PR interval, appeared in eight patients. The latter was probably due to a simultaneous conduction disturbance in the right branch and in both divisions of the left branch (trifascicular bloch). All patients required intracardiac pacing. The prognosis was not good due to the extensive involvement of the conducting system.

The electrocardiogram and vectorcardiogram in Wolff-Parkinson-White syndrome associated with bundle branch block

Abstract Five cases of WPW syndrome associated with bundle branch block were presented. In 3 cases the block affected the right and in 2 cases the left branch. Although tracings taken before and after pre-excitation were shown in several cases, they were not considered indispensable to the correct diagnosis, because it could be definitely ascertained by inspection of a single vectorcardiogram and electrocardiogram, provided that the premature ventricular depolarization occurred in the chamber with the intact bundle branch. Both methods of registering the electrical activity of the heart were accurate, although in one case, the changes in the vectorcardiogram were clearer than those in the scalar electrocardiogram.

DISORDERS OF RHYTHM APPEARING AFTER IMPLANTATION OF SYNCHRONIZED PACEMAKERS

Analysis of clinical arrhythmias has resulted in a closer understanding of the basic electrophysiology of the human heart (Scherf and Schott, 1953; Katz and Pick, 1956; Scherf and Cohen, 1964). The experimental animal has not been the only source of knowledge in the broad field of disorders of impulse formation and impulse conduction (Linenthal and Zoll, 1962; Katz and Pick, 1963). The recent introduction of implantable cardiac pacemakers for the treatment of complete and high-grade atrio-ventricular (A-V) block has made it possible to increase our knowledge of those arrhythmias resulting from the simultaneous activities of several spontaneous pacemakers, by comparing them with those due to interaction of a spontaneous with an artificial pacemaker (Soloff, 1962; Burchell, 1963). Of the several types available we have been interested mainly in the synchronized pacemaker of Nathan et al. (1963), since the cardiac rhythm induced by this instrument approximates to a normal sinus rhythm. The artificial ventricular pacemaker is triggered by an amplified atrial action potential which is then fed into the ventricular pacemaker with a delay simulating that of the A-V interval in normal sinus rhythm. As a safety precaution a standby device is also incorporated, activating the ventricular pacemaker after an adjustable interval should activation from the atria fail. Prevention of a rapid ventricular response to atrial tachycardias, flutter, or fibrillation is similarly controlled through a refractory delay in the pacer of a little over 0 5 second. This allows the ventricles to respond at a rate not exceeding 110 a minute. At atrial rates of 111 to 220 a 2: 1 block is induced, and above 221 the ventricular response is in the order of 3: 1. Nathan et al. developed this type of artificial pacemaker on the assumption that the efficacy of a pacemaker is greater the more it resembles the normal cardiac mechanism. Thus, in instances where normal A-V conduction is impaired, the introduction of a system providing synchronized conduction with physiological A-V delay results in enhanced cardiac output when compared with unsynchronized ventricular pacing (Braunwald and Frahm, 1961). A detailed description of this synchronized pacemaker has been fully reported elsewhere and will, therefore, not be considered in this communication (Nathan et al., 1963). This report is mainly concerned with the description of arrhythmias, heretofore not described in man, which have been observed following implantation of this pacemaker. In addition, the resemblance between the behaviour of man-induced and spontaneous pacemakers will be stressed.

Use of alprenolol in acute cardiac arrhythmias

Abstract Alprenolol, a new beta adrenergic receptor blocking agent, was evaluated as an antiarrhythmic drug in 49 patients with 78 episodes of premature contractions or tachyarrhythmias of supraventricular or ventricular origin. A clinically and statistically significant reduction in frequency of premature contractions was obtained. In addition, a clinically and statistically significant reduction in ventricular rate occurred in those patients with tachyarrhythmias. No severe adverse effects were noted during the study. The results indicate that alprenolol can be used safely and effectively in the treatment of cardiac arrhythmias occurring during acute myocardial infarction. Congestive heart failure was not considered a contraindication when it was judged clinically that the arrhythmia aggravated the heart failure.

Concealed digitalis-induced arrhythmias unmasked by electrical stimulation of the heart

Abstract The relationship between the action of acetyl strophanthidin and pacemaker stimuli was studied experimentally. In all animals, single pacemaker impulses were able to induce repetitive firing immediately before the appearance of the glycoside-induced tachycardia, as well as up to 30 minutes after its disappearance. This phenomenon was seen with impulses falling in any part of diastole, as well as in the responsive portion of systole. Hence, vulnerability could be ruled out as the underlying mechanism. The intensities required for repetition were as low as control threshold values. It appears that electrical stimuli with intensities in the range of those used in commercially available pacemakers can unmask concealed digitalis toxicity. It is possible that this peculiar type of sensitivity to pacemaker stimuli in digitalized animals could be due to a loss of cellular potassium induced by the electrical discharge.

THE SELECTIVE USE OF ANTICOAGULANTS IN ACUTE MYOCARDIAL INFARCTION BASED ON INITIAL PROGNOSIS

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Pacemaker Arrhythmias and Electrocardiographic Recognition of Pacemakers

Adequate interpretation of pacemaker arrhythmias requires a thorough knowledge of the clinical situation in which they appear, the type of pacemaker, and modality of stimulation used, as well as knowledge of the corresponding electronic specifications. At times, this information is essential to reach the correct diagnosis. The significant features of the various (atrial, ventricular, or sequential atrioventricular) pacemakers were stressed placing special emphasis on the most used pacing system, namely, the transvenous QRS-inhibited (demand) ventricular pacemaker. Arrhythmias specific to the latter which could be seen during its normal or abnormal function included magnet-induced vagaries and significant shortening or lengthening of automatic (spike-to-spike) and escape (natural-to-QRS) intervals. Obtaining the maximal efficiency from artificial pacemakers requires the cooperation of patient, manufacturer, cardiovascular surgeon, and clinical cardiologist.