Intrahisian Conduction Disease and Junctional Ectopic Tachycardia VALENTINO DUCCESCHI, M.D., LUCA OTTAVIANO, M.D., MICHELE SANTORO, M.D., RODOLFO CITRO, M.D., RAFFAELE VITALE, and GIOVANNI GREGORIO From the Department of Cardiology and Intensive Care Unit, Vallo della Lucania, Salerno, Italy
Junctional ectopic tachycardia (JET) is an uncommon arrhythmia that mainly affects pediatric patients. However, its clinical presentation may rarely occur in adulthood. Owing to its incessant nature, limited responsiveness to antiarrhythmic agents and poor prognosis, catheter ablation of the junctional focus is often required, even though this may be accompanied by the occurrence of complete atrioventricular block. We report the case of a 68-year-old man with episodes of sustained ventricular tachycardia and repetitive JET whose initiation was often anticipated by a sudden intrahisian conduction delay in the immediately preceding sinus beats. (PACE 2008; 31:378–381) ablation, electrophysiology, clinical Introduction Junctional ectopic tachycardia (JET) is an uncommon arrhythmia mostly observed in pediatric patients, presenting as a congenital or postoperative form.1–13 Its incessant nature is responsible for a poor prognosis even when JET is occasionally observed in adulthood.14–16 We report a peculiar case of an “in vivo” evidence of JET occurrence often preceded by a sudden onset of first-degree intrahisian atrioventricular (AV) block. Case Presentation A 68-year-old man was admitted to our Department in order to perform an electrophysiological evaluation of a wide complex tachycardia. The patient had a history and electrocardiographic evidence of a previous inferior myocardial infarction and complained of palpitations and dizziness. Transthoracic echocardiography revealed inferior wall and posterior septum Acinesia and mildly reduced ejection fraction (42%). Late potentials resulted were present at the signal averaged ECG. Coronary angiography showed total occlusion of the right coronary artery that was distally supplied by a collateral homo- and heterocoronary flow. The first electrophysiological study was performed through the right femoral vein in a drugfree state with the insertion of two quadripolar catheters that were positioned in the high right atrium, His bundle region and subsequently in the right ventricular apex. Sinus node function, AH, and HV intervals were within normal limits and the Wenckebach point was >140 beats/min. Atrial Address for reprints: Valentino Ducceschi, M.D., U.O. UTIC—Cardiologia, Ospedale San Luca—ASL SA 3, Via F. Cammarota, Vallo Della Lucania, Salerno, Italy; e-mail:
[email protected];
[email protected] Received April 4, 2007; revised May 4, 2007; accepted June 10, 2007.
programmed electrical stimulation did not show any induction of supraventricular tachyarrhythmias, while pacing from the ventricle at the drive cycle length of 600 ms with double extra stimuli repetitively initiated three different forms of sustained ventricular tachycardia (VT) with a cycle length ranging from 340 to 310 ms. The patient initially refused AICD implantation and was then discharged under amiodarone treatment (200 mg o.d.) and readmitted to our Department three months later in order to test the efficacy of the antiarrhythmic therapy prescribed. On the day of readmission the patient underwent a 24hour ECG Holter monitoring that revealed several episodes of recurrent sustained narrow QRS tachycardia with a morphology that resembled that in sinus rhythm. The patient was then readmitted in an electrophysiological study that demonstrated the persistent inducibility of the three different VTs in spite of the amiodarone regimen. The study also confirmed the observation of spontaneously occurring frequent repetitive sustained runs of the same narrow QRS tachycardia that had been recorded at the 24-hour ECG Holter monitoring. Several electrophysiological features suggested the diagnosis of JET (Figs. 1–3): • tachycardia initiation caused by a His bundle extra systole (Fig. 1); • QRS morphology resembling that in sinus rhythm, with a tachycardia-dependent mild right bundle branch block aberration (Figs. 1–3); • evidence of AV dissociation (Figs. 1–3); • His bundle electrograms always anticipating the ventricular electrogram with an HV interval were compatible with an ante grade conduction (>35 ms), in spite of being 15 ms shorter to that observed in sinus rhythm (Fig. 1). In our opinion the tachycardia focus was located distally in the His bundle and this was also supported by the occurrence of His bundle potentials split during
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Figure 1. JET is initiated with a His bundle extrasystole (fourth complex) with the two immediately preceding sinus beats exhibiting a His bundle potential split, with a progressive lengthening of the H-H’ interval. The HV interval during tachycardia (35 – 38 ms) is consistent with an antegrade His bundle activation (paper speed = 50 mm/sec, see text for abbreviations).
tachycardia as well as in sinus rhythm (Fig. 1). A diseased His bundle exhibits a delayed conduction, so it would be difficult to admit a retrograde His bundle depolarization during the arrhythmia
Figure 2. The diagnosis of JET is confirmed by the observation of a sustained narrow-complex tachycardia with a His bundle deflection always preceding ventricular activation, with dissociated atrial electrograms (paper speed 50 mm/sec, see text for abbreviations).
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Figure 3. Despite repetitive His bundle capture during ventricular pacing, JET prompt resumption after a noncompensatory pause is observed (paper speed = 50 mm/sec).
with such a quick activation time to result in a positive HV interval (Figs. 1–3). In our opinion, this explanation virtually ruled out the diagnosis of fascicular tachycardia; • tachycardia cycle length variations accompanying H-H’ interval variations, with an effectcause relationship. Concerning the pathogenesis, the arrhythmia onset was not dependent on atrial and/or ventricular programmed electrical stimulation, but rather on an enhanced automaticity of a His bundle focus. This was suggested by its presentation in frequent recurrent sustained runs, its initiation by a His bundle extrasystole, and its inconstant sensitivity to ventricular overdrive pacing in spite of repetitive and consecutive His bundle potential captures (Fig. 3). Besides, the arrhythmia onset was sometimes preceded by sinus beats with an impaired AV conduction due to the sudden occurrence of firstdegree intrahisian AV block (Fig. 1). The dysrhythmia did not respond to i.v. lidocaine, magnesium sulphate, amiodarone, and procainamide, whose only effects were a slight prolongation of JET cycle (400 ms → 420 ms). Given the incessant nature of the dysrhythmia and the high ventricular electrical vulnerability, the only reasonable therapeutic option was to ablate the His bundle inducing a complete infrahisian AV block and implant a dual chamber AICD.
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Since then, the patient has been asymptomatic and after a two-year follow-up several 24-hour ECG Holter neither showed resumption of AV conduction nor JET recurrence despite its previously incessant nature. Finally, the therapeutic efficacy of His bundle ablation with the consequent induction of third-degree infrahisian AV block excludes the possibility of an interfascicular reentrant tachycardia, given that in this arrhythmia the His bundle appears to play only a bystander role.17 Discussion JET is considered a rare arrhythmia presenting at the ECG with narrow ventricular complexes, AV dissociation, and QRS morphology resembling that of sinus beats.1–18 Invasive electrophysiology has demonstrated that each ventricular electrogram is preceded by a “leading” His bundle deflection with an HV interval that has to be compatible with ante grade conduction (> 35 ms).1–3,14,15 The electrical and histopathological genesis of JET is still unclear. Some authors underlined the importance of His bundle fibers extensive disruption or focal degeneration and split,3,19 while others described structural abnormalities of the whole AV junction.20 A recent report of a congenital JET evolving into complete AV block supported the idea of a progressive disease involving the AV junction that had manifested in different ways.11 Whatever the pathological background, JET may be more commonly encountered in pediatric patients, occurring as a postoperative complications of surgical interventions that involve interventricular septum manipulation or cause damage to the AV conduction system.6 However, there is also a purely congenital type that affects infants with otherwise normal hearts.3,13 Only few papers reported JET onset in adulthood and regarded very small group of patients.14–16 As for the clinical presentation, JET appears more often incessant than paroxysmal and as a result it frequently causes hemodynamic impairment.1–20 Most of the collected evidence relates JET electrophysiological mechanism to enhanced automaticity due to a focus located on the AV junction and this might also explain JET sensitivity to cathecolamines.1–20 Class IC antiarrhythmic agents, amiodarone, and β-blockers may be re-
garded as possible therapeutic options, although a decrease in ventricular rate rather than a complete resolution of the arrhythmia should be expected, since sinus rhythm restoration may not be accomplished in several cases.2,4–7,9,13 Radiofrequency ablation represents a valid alternative to medical therapy, although in most cases it has to be followed by a pacemaker implantation, given the difficulties to abolish the JET focus without impairing AV conduction.1,10,15,16 Platt et al. tried a more conservative strategy and ablated JET targeting the right bundle in a patient with third-degree AV block. This approach generated a complete infrahissian AV block and allowed the persistence of the His bundle focus automaticity, finally resulting in mutually independent atrial, His bundle, and ventricular rhythms.21 In this paper we describe a peculiar case of JET associated with an “in vivo” evidence of a coexisting His bundle disease. JET initiation by His bundle extrasystoles was often immediately preceded by a His bundle deflection split that otherwise could not be recorded, so we might infer that in a diseased His fascicle a mild impairment of conduction would warm an otherwise silent automatic focus and favor its abnormal discharge. Such a situation may have been facilitated by the chronic amiodarone therapy that can potentially affect His bundle conduction.22,23 In fact, since the first electrophysiological study the patient did not experience any acute inflammatory or ischemic condition, nor suffered from any metabolic and/or electrolytic derangement that could explain the new arrhythmia occurrence. Therefore amiodarone, which is also a mild sodiumchannel blocking agent, might have caused the intrahisian conduction impairment that was often recorded immediately preceding JET onset. Amiodarone relation with His bundle enhanced automaticity, however, appeared less clear given its capability of inhibiting depolarization-induced automaticity.22,23
Acknowledgment We are indebted to Mr. Antonio Isabella, Mr. Alessandro Laurito, Mr. Giuseppe Peduto, and Miss Antonietta Sacco for the precious support they provided to our EP Lab.
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