Tachycardia-Mediated Cardiomyopathy and the Permanent Form of Junctional Reciprocating Tachycardia

Abstract

Permanent junctional reciprocating tachycardia, or atrioventricular reentrant tachycardia utilizing a slowly conducting posteroseptal accessory pathway, is a rare form of reentrant supraventricular tachycardia in children and adults. The characteristic features of this narrow complex tachycardia are a long RP interval and inverted P waves in the inferior leads. This form of accessory-pathway-mediated tachycardia, which is usually incessant, can lead to a tachycardia-induced cardiomyopathy and congestive heart failure if left untreated. Radiofrequency ablation of the accessory pathway in permanent junctional reciprocating tachycardia is the definitive treatment in these patients, and in many instances the effects of prolonged tachycardia on ventricular function are reversible after successful ablation. We present an illustrative case.

Atrioventricular (AV) reentrant tachycardia utilizing a slowly conducting posteroseptal accessory pathway—also known as the permanent form of junctional reciprocating tachycardia (PJRT)—is a unique reentrant supraventricular tachycardia (SVT) in children and adults. Features of this narrow complex tachycardia include a long RP interval with inverted P waves in the inferior leads on the surface electrocardiogram (ECG). This type of accessory-pathway-mediated tachycardia is usually incessant and can lead to tachycardia-induced cardiomyopathy. Radiofrequency ablation of the accessory pathway in PJRT is curative in these patients, and the effects of prolonged tachycardia (including depressed ventricular function in many instances) are reversible after successful ablation. We present the case of a patient whose PJRT, over the course of 2 years, resulted in tachycardia-mediated cardiomyopathy.

Case Report

A 35-year-old woman presented with a history of asthma and persistent tachycardia. The tachycardia had been discovered in August 2007, when she had presented in labor. She had remained in tachycardia during the immediate postpartum state, and a surface echocardiogram obtained at that time revealed a severely depressed left ventricular ejection fraction of approximately 0.25. She was given a diagnosis of peripartum cardiomyopathy and treated medically with a regimen of carvedilol, olmesartan, and digoxin for 1 month, after which she discontinued all of her medications without following up with her physician. After becoming pregnant again in November 2007, she developed dyspnea on exertion and progressive fatigue. Repeat echocardiography again revealed depressed left ventricular function with an ejection fraction of 0.25. Due to the diagnosis of peripartum cardiomyopathy, the patient underwent elective termination of her pregnancy on the advice of her treating physician.

The patient was seen in consultation for a 2nd opinion, at which time the medical regimen for a suspected diagnosis of peripartum cardiomyopathy was resumed. It was noted, however, that she had evidence of an incessant narrow complex SVT on her ECG. There was a long RP narrow complex SVT with inverted P waves in leads II, III, and aVF (Fig. 1). Within a month, she was referred to our institution for evaluation of cardiomyopathy. Upon initial evaluation in the office, the patient was noted to be persistently in supraventricular tachycardia at a rate of 106 beats/min; her physical examination was otherwise unremarkable. Due to the incessant nature of her tachycardia and history of congestive heart failure, an electrophysiology study was recommended.

Fig. 1 The 12-lead electrocardiogram at presentation indicates tachycardia. Note the presence of inverted P waves in the inferior leads, in the setting of a long RP tachycardia.

In the electrophysiology laboratory, the patient's baseline ECG revealed a long RP narrow complex tachycardia with inverted P waves in the inferior leads, which matched her previous, outpatient ECGs. Spontaneous ventricular premature depolarizations were observed to terminate the tachycardia without reaching the atrium. Re-initiation of the tachycardia occurred after approximately 2 consecutive beats of sinus rhythm. The initial P wave of the tachycardia was identical to all subsequent P waves. The earliest retrograde atrial activation during tachycardia was present at the proximal-to-mid coronary sinus (Fig. 2). An intravenous adenosine bolus terminated the tachycardia, which spontaneously initiated again after 2 beats of sinus rhythm. Overdrive ventricular pacing during tachycardia revealed a ventricular–atrial–ventricular response. These features were consistent with an AV nodal dependent tachycardia. Paced ventricular extrastimuli, timed to His bundle refractoriness, were administered from the right ventricular apex. These advanced the atrial electrogram approximately 27 ms and reset the tachycardia to an identical retrograde atrial activation pattern (Fig. 3). On the basis of these findings, a diagnosis of orthodromic reciprocating tachycardia utilizing a slowly conducting posteroseptal accessory pathway, or PJRT, was made. Radiofrequency ablation of the posteroseptal pathway, delivered briefly (20 sec) and at relatively low power (30 W) within the proximal coronary sinus during tachycardia, resulted in tachycardia termination and resumption of sinus rhythm (Fig. 4). Atrial and ventricular extrastimuli testing was performed after ablation, and no tachyarrhythmias were induced. The patient had normal AV and ventriculoatrial Wenckebach conduction after the procedure, with no evidence of accessory pathway conduction. She was discharged from the hospital after overnight observation. Repeat ECG and echocardiography, performed 1 month after ablation, revealed (respectively) sinus rhythm and improved left ventricular function, with a left ventricular ejection fraction of 0.45.

Fig. 2 Retrograde atrial activation pattern during tachycardia. The earliest site of retrograde atrial activation is the CS 5–6 bipole (within the proximal coronary sinus), which denotes an eccentric retrograde atrial activation pattern.

Fig. 3 The His-refractory premature ventricular contraction (PVC) advances and resets the tachycardia. This finding proves the presence of an accessory pathway that participates in the tachycardia circuit.

Fig. 4 The tachycardia terminates during radiofrequency ablation. After ablation has been delivered in the proximal coronary sinus, tachycardia ceases and sinus rhythm resumes.

Discussion

A narrow complex supraventricular tachycardia in which the RP interval is longer than the PR interval can be classified as a long RP tachycardia. The differential diagnosis of long RP tachycardia consists of atypical (fast–slow) atrioventricular nodal reentrant tachycardia (AVNRT), atrial tachycardia, junctional tachycardia, and PJRT. Although adenosine can be used to help differentiate AV nodal-dependent narrow complex SVTs from non-AV nodal-dependent SVTs among patients with short RP tachycardias, it is less useful in predicting the mechanism of a long RP tachycardia, because atypical forms of AVNRT, adenosine-sensitive atrial tachycardia, and PJRT can all be terminated with adenosine.¹ Definitive diagnosis of long RP tachycardia is best made during electrophysiologic study. The presence of an eccentric retrograde atrial activation sequence helps differentiate the various types of long RP tachycardia. However, atypical AVNRT, PJRT, and low right atrial tachycardias can all have earliest atrial activation present at the coronary sinus ostium. The response to a ventricular extrastimulus (VES) given at the time of His bundle refractoriness can help differentiate atypical AVNRT from PJRT. Termination of tachycardia from a His-refractory VES that does not conduct to the atrium—or post-excitation of the atrium due to a His-refractory VES during tachycardia—is diagnostic of an accessory-pathway-mediated tachycardia,² such as PJRT. Incremental ventricular pacing that produces a retrograde atrial activation sequence identical to that in tachycardia (in addition to manifest evidence of entrainment in tachycardia) is diagnostic of the presence of an accessory-pathway-mediated tachycardia, which can help exclude an atrial tachycardia.³ Permanent junctional reciprocating tachycardia is a rare form of incessant supraventricular tachycardia that is characterized by inverted P waves in the inferior leads (consistent with retrograde atrial activation) and a long RP interval during tachycardia on electrocardiography. It is a narrow complex tachycardia that uses the AV node for antegrade conduction and a slowly conducting accessory pathway for retrograde conduction. Permanent junctional reciprocating tachycardia is classically spontaneous in its initiation, with sinus node acceleration in the absence of a critical prolongation of the PR or AH interval⁴; the 1st beat of tachycardia has a P wave morphology identical to that of all subsequent beats of the tachycardia. The retrograde conduction properties of the accessory pathway involved in PJRT have been described to be slowly conducting and decremental,⁵ and frequently these tachycardias are susceptible to termination with adenosine in the AV node or accessory pathway.^6,7 In PJRT, the slowly conducting accessory pathway most often arises from the posteroseptal region of the atria, near the os of the coronary sinus.^7,8 A case series published by Ticho and colleagues⁹ reported that the location of the accessory pathway can be found in regions other than the coronary sinus os, but these cases are infrequent.

Permanent junctional reciprocating tachycardia is more common in the pediatric than in the adult population.¹⁰ It was first recognized by Gallavardin and Veil in 1927¹¹ but was originally described by Coumel and associates in 1967,¹² and that description was refined by Gallagher and Sealy in 1978.¹³ Since that time, several case series have been published.^7,8,14 An important feature of PJRT, shown in multiple case series, is that many patients with PJRT are susceptible to tachycardia-related cardiomyopathy that leads to congestive heart failure. Recognition of PJRT as a cause of nonischemic cardiomyopathy among pediatric and adult patients is crucial, because ablation can alleviate symptomatic palpitations and dramatically improve ventricular function in those with heart failure arising from incessant tachycardia. The prevalence of tachycardia-related cardiomyopathy is significantly higher among patients with PJRT, ranging between 20% and 50%.^7,8,14 Most, if not all, patients who receive successful ablation of their incessant accessory-pathway-mediated tachycardia show significant improvement in left ventricular function.^7,8 Medical therapy with antiarrhythmic or other rate-control agents is largely ineffective in controlling heart rate and symptoms.^7,8,14 The posteroseptal region of the heart, specifically within the coronary sinus, is a high-risk area for radiofrequency ablation because of the potential for coronary artery damage, as described in the case series by Schneider and colleagues.¹⁵ However, in our patient, radiofrequency ablation was delivered briefly and at relatively low power. These ablation settings lowered the risk of coronary artery damage and obviated the need for coronary angiography before ablation. Moreover, immediate cessation of accessory pathway conduction was observed during the onset of ablation. Alternatively, cryoablation of the accessory pathway is associated with almost no risk of coronary artery damage when delivered within the coronary sinus. The advantages of cryoablation within the coronary sinus are noted in a study by Aoyama and co-authors.¹⁶ However, a different study¹⁷ reported a higher recurrence rate of accessory pathway conduction after cryoablation. Therefore, we treated our patient with radiofrequency current for its higher efficacy in application to accessory-pathway-mediated tachycardias, such as PJRT.