Biomedical subjects
Publications and source records attributed to C Luca.
In 3 patients with the long QT syndrome, one caused by quinidine and 2 of congenital origin, right ventricular monophasic action potentials were excessively prolonged and of varying shapes in different recording sites. In addition, effective refractory periods of the ventricular muscle were abnormally long.
The paper presents a report on the clinical and electrographic spectrum of nine patients with the sick sinus syndrome with severe symptoms of clinical disturbances and serious disorders of impulse formation and conduction. Seven patients had syncope associated with sinus bradycardia, sinoatrial block or atrial fibrillation with slow ventricular rate. Prolonged episodes of atrial and ventricular asystole occurred and were interrupted by junctional escape beats. Paroxysmal atrial fibrillation and flutter were foun in three patients and infrahisian block in four. Atropine induced a slight acceleration of the heart rate in all the patients studied while the post-suppression S-A node recovery time was prolonged in four.
Three cases are described in which accelerated atrioventricular conduction occurred during an acute myocardial infarction. The first patient, an 82-year-old woman, developed a WPW syndrome suggesting posterior right ventricular preexcitation, a pattern which persisted for four months until her death. An accessory bundle was found on autopsy. Fibrotic changes, associated with acute lesions (hemorrhage, polymorphonuclear infiltrates) were present in the atrioventricular node and His-Purkinje system. Two men, of 47 and 74 years, developed a short PR interval associated with supraventricular tachycardia during the course of an acute myocardial infarction. The PR interval returned to its initial value in one case and remained unchanged for three months in the other. Accessory atrioventricular connections which became functional during myocardial ischemia may explain the various electrocardiographic patterns of preexcitation.
An unusual case with quinidine induced marked T and U waves abnormalities of giant size and alternans occuring in sinus rhythm is reported. Right ventricular monophasic action potential recorded during bizzare T and U waves abnormalities showed a marked prolongation of its duration and regressed after the drug was withdrawn.
In 5 patients ventricular parasystole and fixed coupling ectopic beats were recorded. In two cases ventricular parasystole and bigeminism acted intermittently. In one case the spontaneous transition from ventricular parasystole into parasystolic tachycardia with "reverse coupling" and finally to ventricular bigeminy could be illustrated. In all these cases ventricular parasystole and fixed coupling extrasystolic activity seems to be a close related mechanism. In other two cases there was a mathematical relationship between the sinus and parasystolic discharge rate which explained the periodic fixed coupling of ectopic beats. In one of these cases His bundle electrography was helpful in documenting the ventricular origin of ectopic beats.
In 12 patients with manifest hypothyroidism right atrial monophasic action potentials showed a significant prolongation in comparison with data from normal or euthyroid patients. Atrial effective refractory periods were also significantly prolonged. After thyroid treatment the monophasic action potential duration and the effective refractory period of the right atrium were within normal ranges. In 6 hypothyroid patients studies of AV conduction with the aid of His bundle electrography and atrial pacing showed a supraHisian conduction delay which was manifest in one case and latent in another two. InfraHisian conduction delay was encountered in 2 cases.
His bundle electrograms were recorded in 12 patients with atrial fibrillation. In all cases but one, the dominant rhythm was atrial fibrillation. In 1 case the dominant rhythm was fascicular tachycardia due probably to digitalis overdosage. However ventricular, fascicular and junctional beats could be often recognized on His bundle tracings, even when QRS configuration was similar to supraventricular conducted beats due to atrial fibrillation. In the patients in whom sinus rhythm occurred, the H-V interval was unchanged. Although it is admitted that during atrial fibrillation the zone of concealment of A-V conduction is in the A-V nodal area, concealed penetration of atrial impulses in the fascicular system may be encountered in patients not treated with digitalis.
A case of recurrent ventricular paroxysmal tachycardia in a young man without obvious heart disease is described. Posttachycardiac T-wave inversion followed the arrhythmic episodes. Programmed stimulation of the heart in association with intracardiac recordings showed evidence in favor of reentry within the bundle branches and its divisions during tachycardia. A critical prolongation of the H2-V3 interval preceded each paroxysm of tachycardia.
Using Lidocaine intravenously in 99 patients with atrial arrhythmias, it was observed that the drug has a regularising effect in 41 from 45 atrial arrhythmia, atrial tachycardia with block and accelerated ectopic supraventricular tachycardia, where the enhanced focal activity should be taken into account. No effect was observed in functional supraventricular tachycardia, paroxysmal atrial flutter and fibrillation and tachyarrhythmia in WPW syndrome, where the re-entry mechanism plays the major role. The effect of the drug is short lived, but may be prolonged by using the drug in perfusion or repeatedly with an intramuscular method. Lidocaine acts by depressing the enhanced atrial focal activity, and therefore may be of value in the treatment of these kinds of arrhythmias.
In 28 patients with established atrial fibrillation [AF], right atrial monophasic action potentials [MAP] were recorded before DC shock. A close correlation was found between the atrial rate and MAP duration of the fibrillatory waves [FW]. The duration of MAPs ranged between 1 and 6 mV. The atrial rate ranged between 311 and 578 per minute, the highest rates were found during lone AF. In two patients in whom cardioversion failed, a prolongation of right atrial MAP duration of the FW was noted. The efficacy of DC shock and the maintenance of sinus rhythm after cardioversion was greater in patients with AF having a slower rate and a longer MAP.
Five patients with bidirectional tachycardia due to digitalis toxicity associated with severe organic heart disease were studied. The origin of the abnormal rhythm was established with the aid of His bundle recordings in three cases and by indirect clues in the others two. In three cases the origin of bidirectional tachycardia was suprahisian while in two patients it was infrahisian. In one patient the transition from junctional to ventricular tachycardia could be observed. Bidirectional tachycardia appears to be a complex arrhythmia in which similar electrocardiographic configuration can be due to different mechanism. Digitalis toxicity was often a causal factor.
A case with complete A-V heart block in whom retrograde P- waves following some of the ventricular complexes were due to an ectopic junctional activity with the characteristics of parasystole is reported. His bundle electrogram showed an infrahisian block. After administration of 1 mg atropine intravenously the retrograde P- waves were detached from the ventricular automatic complexes and an H' deflection preceded each inverted P- wave with an H'-A' interval of 40 msec.
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Monophasic action potentials recorded in two patients with atrial flutter and one patient with atrial fibrillation showed a nonuniform depolarization of the right atrial wall. In each of the two patients with atrial flutter, there was a site where two separate action potential deflections were recorded for each flutter wave. It was supposed that this was the site of re-entry for a cycling wavelet subsidiary to the main flutter wave. In the patient with atrial fibrillation, three types of electric atrial activity were found: regular activity at 180 per minute similar to that found in flutter, small irregular activity at a rate of 400 per minute, and a mixed type of the former two. The significance of these findings for the mechanism of atrial flutter and fibrillation is discussed.
The case is reported of a 66-year-old woman with bidirectional tachycardia caused by digitalis intoxication. His bundle records demonstrated the presence of two foci, one junctional and the other a fascicular one.
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In a group of eight patients with ventricular premature beats, ventriculoatrial conduction, with retrograde activation of the His bundle and the atria could be demonstrated by His bundle electrograms in four subjects. All had early ventricular premature beats with coupling indices between 210 and 350 msec. In the other four cases, concealed retrograde conduction could be demonstrated in the A-V nodal area. The ventricular ectopic beats were late, and depending upon the refractory period of the A-V node these extrasystoles were interpolated or followed by compensatory pauses.
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