Julio O. Lázzari

Clinical efficacy of amiodarone as an antiarrhythmic agent.

Amiodarone, administered orally in doses of 200 to 600 mg/day, was remarkably effective in the treatment and prevention of a wide variety of atrial and ventricular arrhythmias. Total suppression and control was provided in 98 (92.4 percent) of 106 patients with supraventricular arrhythmias and in 119 (82 percent) of 145 patients with ventricular arrhythmias. The rates of total control of the arrhythmia were: 96.6 percent in 30 patients with recurrent atrial flutter or fibrillation, 96.6 percent in 59 patients with repetitive supraventricular tachycardia, 100 percent in 27 patients with Wolff-Parkinson-White syndrome and 77.2 percent in 44 patients with recurrent ventricular tachycardia unsuccessfully treated with other drugs. Excellent results were obtained in 6 to 8 patients with repetitive ventricular tachycardia and ventricular fibrillation related to postinfarction ventricular aneurysm and in 12 of 14 patients with ventricular extrasystoles and ventricular tachycardia related to Chagasic myocarditis. Amiodarone proved safe in patients with severe congestive heart failure and severe myocardial damage. Its clinical efficacy was related to its electrophysiologic properties and to two unique properties: its wide safety margin and its cumulative effect. The latter liberates patients from a rigid hourly schedule and provides for continuous antiarrhythmic control, days and even weeks after treatment is discontinued.

Intraventricular trifascicular blocks. Review of the literature and classification

Abstract The right bundle branch and the two divisions—anterior and posterior—of the left constitute the three main terminal fascicles of the intraventricular conduction system. Depending on whether conduction is permanently or only intermittently interrupted in these three fascicles, eight different possibilities or combinations of intraventricular and atrioventricular conduction disturbances may occur. A theoretical design covering all those possibilities is suggested, and clinical examples are bestowed for each of them. The existence of these syndromes, which we have termed altogether “trifascicular blocks”, provides one of the most valuable evidences of the anatomical and functional “trilaterality” of the human intraventricular conduction system.

Intraventricular trifascicular blocks. The syndrome of right bundle branch block with intermittent left anterior and posterior hemiblock

Abstract When conduction is interrupted in the right bundle branch and only intermittently in the two divisions, anterior and posterior, of the left, a very peculiar and as yet undescribed electrocardiographic syndrome occurs. Its main feature is the presence of two different right bundle branch block patterns, with completely opposite directions of the ÂQRS (superiorly and to the left in one; inferiorly and to the right, in the other); together with severe A-V conduction disturbances. Four cases of this singular syndrome are here described and analyzed. Such cases can be considered exceptional experiments of nature, providing most invaluable evidence for the existence of block within the anterior and posterior divisions of the left bundle branch. However, the syndrome of “right bundle branch block with intermittent left anterior and posterior hemiblock” is only one of the several possibilities of what we have named “intraventricular trifascicular blocks,” which will be considered in the second part of this paper.

Superior vena cava occlusion and/or syndrome related to pacemaker leads

Four cases of pacemaker-related SVC obstruction or syndrome are reported. While two of them lacked any symptom suggestive of SVC obstruction, the other two presented with mild symptoms. None of them received any treatment. One died from a cause unrelated to SVC obstruction, while the others presented no change in their clinical status. A review of the literature suggests that neither thrombotic nor fibrotic obstruction in patients with pacemaker leads is strictly related to the number of abandoned leads, the presence of severed leads, or the time elapsing from pacemaker implant. The diagnosis is clinically made and is confirmed by venography. Only one of the reported deaths is attributable to SVC obstruction. The remaining cases from the literature responded to treatment with heparin, thrombolytic agents, angioplasty, or surgery.

Five cases of intermittent left anterior hemiblock

Abstract The first 5 cases of intermittent left anterior hemiblock (block in the anterior division of the left bundle branch) are reported. These cases can be considered exceptional experiments of nature, providing both invaluable evidence for the existence of left anterior hemiblock and useful material for studying, with great accuracy, the changes that this conduction disturbance produces on the previously normal or abnormal electrocardiogram in man. The three major electrocardiographic features of left anterior hemiblock are found to be: (1) An ÂQRS directed at approximately −60 °; (2) the presence of a Q 1 S 3 pattern, simulating a counterclockwise rotation of the heart; and (3) a QRS widening of not greater than 0.02 sec.

Wenckebach Periods in the Bundle Branches

Two cases of intermittent bundle-branch block in which Wenckebach periods could be directly visualized are reported. The conduction ratios were either 3:2 or 4:3, as are commonly seen in cases of the Wenckebach phenomenon of atrioventricular (A-V) conduction. Other groups of beats apparently showing 3:1 and 4:1 bundle-branch block were interpreted as indicating incompletely concealed Wenckebach periods in the bundle branches, with actual conduction ratios of 3:2 and 4:3, respectively.Three prerequisites are necessary for the occurrence of either direct or incompletely concealed Wenckebach periods in the bundle branches: (1) The opening beat should be normally conducted (in the affected bundle branch); (2) the second beat should be conducted with a delay of no more than 0.04 to 0.06 sec; (3) the damaged bundle branch should not be activated retrogradely in the closure beat.Wenckebach periods in the bundle branches may be completely concealed if the conduction delay lasts more than 0.04 to 0.06 sec in the opening beat. In cases of bilateral bundle-branch block, Wenckebach periods in the bundle branches may be indirectly visualized through changes in the A-V conduction.

The mechanism of bidirectional tachycardia.

T he human intraventricular conduction system has always been considered bifascicular. However, this system also is and operates as trifascicular, its three main terminal fascicles being the right bundle branch and the two divisions, anterior and posterior, of the left bundle branch. Evidence for the trifascicularily of the conduction system has appeared extensively in the literature34-3g and this fact has shed new light on many aspects of everyday electrocardiography. This is especially true for the left anterior (LAH) and left posterior (LPH) hemiblocks (blocks in the anterior and posterior divisions, respectively, of the left bundle branch), either alone or combined with right bundle branch block (RBBB). Furthermore, the trifascicularity of the conduction system has also led to the discovery of: (1) the existence of a new family of electrocardiographic syndromes, the “intraventricular trifascicular blocks”34~35,38,3g; (2) the existence of a new type of “divisional” left bundle branch block (LBBB)34*3e; (3) the different manifestations of aberrant ventricular conduction of supraventricular premature beats.34-36 (4) In addition, it has rendered possible a new approach to the old problem of the determination of the place of origin of ventricular extrasystoles, and in this field, it permitted to predict and then substantiate that left ventricular extrasystoles must necessarily furnish two main, very definite and diametrically opponent AQRS directions.34l37 In this paper we shall try to show how the trifascicularity of the intraventricular conduction system also enables us to explain a curious cardiac arrhythmia, the so-called “bidirectional tachycardia” (BT), which has so far resisted every attempt at accurate interpretation. As we shall see, BT is nothing but a syndrome of paroxysmal trifascicular block, occurring during some episodes of supraventricular tachycardia.

Efficacy of amiodarone during long-term treatment of malignant ventricular arrhythmias in patients with chronic chagasic myocarditis

Oral amiodarone was administered to 24 patients with chronic chagasic myocarditis (CCM) and malignant ventricular arrhythmias. Control 24-hour Holter recordings revealed frequent ventricular premature beats (VPBs) (157 to 2572/hr; mean 714 +/- 125), multiform VPBs, and countless numbers of ventricular couplets in all patients, R-on-T phenomenon in 17 patients, and ventricular tachycardia in 21 patients. Amiodarone caused total and persistent suppression of ventricular couplets and tachycardia and greater than 93% reduction of VPB number in 22 patients, during a follow-up of 26.6 months (range 2 to 55 months). In 1 patient, ventricular couplets and tachycardia persisted despite the fact that a 98.2% reduction of VPB number was achieved. This latter patient was the only one in the whole group who experienced sudden death. The maximal antiarrhythmic effect was attained gradually after 3 to 26 weeks (mean 7.4). In four patients in whom treatment was discontinued after 3 to 12 months, the antiarrhythmic protection lasted 4 to 9 weeks. In nine patients the dose of amiodarone was 600 to 800 mg/day. In 15 patients the dose had to be increased to 800 to 1000 mg/day. Despite the presence of congestive heart failure in seven patients and intraventricular block in 17 patients, no limiting side effects were observed. Amiodarone proved to be extremely effective and safe against the most malignant ventricular arrhythmias of CCM.

Transarterial Permanent Pacing of the Left Ventricle

Clinical evaluation of a 64‐year‐old male patient with a permanent pacemaker showed a right bundle branch block in his EGG that led to the suspicion of catheter misplacement. A two‐dimensional echocardiogram and bilateral venogram demonstrated that the pacemaker lead was not in the venous system and that its course was from the axillary artery to the left ventricle passing through the aortic valve. Thirty‐three days after implant, replacement of the pacemaker lead through the venous system to stimulate the right ventricular endocardium was performed. At 7 month follow‐up the patient has had no complication from his previous arterial pacemaker implantation.

Malignant Ventricular Arrhythmias in Chronic Chagasic Myocarditis

We studied 28 cases of chronic chagasic myocarditis (CCM) with frequent ventricular arrhythmias. Two‐hundred and three conventional ECGs recorded during 3 months showed ventricular extrasystoles (VE) ranging between 0.2 and 6 per ten beats in 100%; multiform VE in 97.04%; couplets in 79.31%; ventricular tachycardia (VT) in 42.85%; and R on T in 21.67%. A 24‐hour continuous recording showed that VE ranged between 3780 and 61733 (mean 16618 ± 2627); muitiform VE and couplets were present in 100% of patients, and VT was present in 78.5%. In 16 patients (group I) the frequency of VE was persistently high, without diurnal variation; 11 patients showed sustained reduction during sieeping hours and only one showed an increase during night sleep (group II). Even in group II, VE never disappeared for periods longer than 10 minutes. In five patients, four 24‐hour recordings were obtained at weekly intervals, and in five other patients a second 24‐hour recording was performed 10 to 24 months later. The remarkable frequency, persistence and low variability of ventricular arrhythmias in CCM suggest that such arrhythmias can be used as a most stable, reliable, but highly demanding model for testing the efficacy of antiarrhythmic drugs. (PACE, Vol. 5, March‐April, 1982)