Is Incessant “Asymptomatic” Supraventricular Tachycardia Worth Ablating?

Introduction

Permanent junctional reciprocating tachycardia (PJRT), a rare form of supraventricular tachycardia, is generally incessant and caused by atrioventricular (AV) reentry with the AV node as the antegrade limb and a slowly conducting, posteroseptal, accessory pathway as the retrograde limb. Described many years ago¹, this tachycardia has characteristic features of an apparent long RP tachycardia with inverted P waves in leads II, III, and aVF, and upright P waves in lead V1. PJRT predominantly occurs in infants and children, but can persist into adulthood and cause arrhythmia-induced cardiomyopathy (AIC) with left ventricular dysfunction and symptomatic, severe, systolic heart failure.^2,3 The process can be reversible if caught early enough and treated. 

In children, especially when symptomatic, catheter ablation is recommended due to the high likelihood of developing AIC.^3-6 In infancy, drug therapy is recommended until catheter ablation can be performed after reaching adequate size. However, antiarrhythmic drug therapy is frequently ineffective. For adults with PJRT who develop cardiomyopathy and/or heart failure, ablation is also indicated, but little is known about the clinical course of those older adults who have chronic tachycardia but do not present with ventricular dysfunction, heart failure, or overt symptoms. Not all patients with persistent, incessant tachycardia (even if due to PJRT) develop cardiomyopathy. Therefore, treatment with drugs or even ablation in older patients may only cause adverse effects. 

In this article, we address the question: for older patients with persistent tachycardia, no obvious symptoms, and normal ventricular function, is the best approach to treatment either catheter-based ablation, drugs, or no treatment at all? 

Case Description

A 78-year-old female without known medical problems presented with persistent tachycardia (Figure 1). She was suspected to have atrial flutter by her referring physician, and was anticoagulated and given large doses of metoprolol and digoxin, without effect. A cardioversion was scheduled, and she was seen at that time by the electrophysiology team, who recognized her supraventricular tachycardia. Repeated carotid sinus massage stopped the rhythm from reproducing, but it recurred immediately. She stated that her heart rate has always been above 100 bpm — it occasionally exceeds 150 bpm with minimal or no exertion. She had no obvious symptoms. An echocardiogram showed normal ventricular function and ventricular size. 

How would you manage this case? Would you stop the medications and leave her alone? Proceed to ablation? Although medications slightly slowed her rate, they were mostly ineffective. Without apparent symptoms, ablation might uncover severe sinus bradycardia requiring a pacemaker, or even cause AV block. However, ablation might also improve her long-term outcome and she may become more functional. In careful discussion with the patient, considering potential risks and benefits, a mutual decision was made to proceed with electrophysiology testing and ablation of what appeared to be PJRT. 

In the electrophysiology laboratory, during tachycardia, the earliest atrial activation was present at the roof of the ostium of the coronary sinus on the right posterior septum (Figures 2 and 3). Radiofrequency applications of low power and short duration terminated the tachycardia with no sinus pause (Figure 4). The tachycardia was no longer inducible, and no retrograde conduction was present. Sinus node and AV function were normal. The patient was discharged without any specific medical therapy. 

At two-month follow-up, she reported that she was glad to be off all medications. She remains symptom free and now has more energy. 

Discussion

The differential diagnosis of incessant “long RP” tachycardia includes atrial tachycardia, orthodromic atrioventricular reentrant tachycardia (AVRT) using a slowly conducting and decremental posteroseptal accessory pathway known as PJRT, and “atypical” AVNRT.⁷ As prior ventricular activation may not be linked to subsequent atrial activation, the term “long RP” may be a misnomer.

Classically, PJRT is recognized in children or young adults and characterized as an incessant (“permanent”) form of supraventricular tachycardia that often leads to AIC. However, PJRT may be diagnosed at any age and can sometimes express itself as a paroxysmal form of supraventricular tachycardia with a long RP interval.^8,9 Retrograde-only, slowly conducting, and “decremental” accessory AV pathways can present at any age.¹⁰

Diagnosing PJRT can be challenging in adults, especially when there are no symptoms and the rhythm is discovered by happenstance. PJRT is less well-recognized outside the electrophysiology community, but it presents with incessant tachycardia and a classic, almost unmistakable ECG pattern. However, it can also be confused with an incessant form of atypical AVNRT.¹⁰ 

Criteria favoring PJRT vs atypical AVNRT include obligatory 1:1 AV relationships during tachycardia and ventricular pacing, and His-refractory ventricular premature extrastimuli that reset the atria or stop tachycardia with VA block.¹¹ Criteria favoring incessant atrial tachycardia include presence of an AAV response after ventricular pacing.¹² Other criteria, including use of entrainment, may be helpful.¹³

Ablation is clearly indicated in those for whom systolic heart failure develops due to AIC, especially in children.^6,9,12,14 For these patients, ablation reverses heart failure and normalizes ventricular function. Medications are often tried, but are generally ineffective. However, based on present data, complete remodeling may not take place; therefore, it is best never to get to this point.³ Limited long-term follow-up data are available for those patients in whom ventricular function is intact and no overt symptoms are present, especially in the adult population, even though a suggestion has been made that ablation may not be needed for those with slow tachycardias, especially if not incessant.⁶ 

However, this begs the question: is it ever a good idea to allow an incessant tachycardia to persist if it can be treated? Epidemiologically, faster heart rates are associated with poorer prognosis,¹⁵ but any causal relationship remains unknown. We have even postulated that persistent rates in the upper normal range may be a problem for select individuals.¹⁶ 

As the patient improved with ablation, even though she reported no symptoms, this case highlights that it can be difficult to determine and quantitate symptoms in some patients with persistent tachycardia, especially when the rates are close to the normal range. This is also true in patients with other forms of tachycardia, including due to atrial fibrillation. Such patients may feel better in sinus rhythm due to rate control, but perhaps also due to normalization in appropriate AV synchrony. In such patients, if tachycardia recurs, symptoms become very apparent even though they were not so much before. 

In an older patient with persistent tachycardia, there is also the risk of exacerbating underlying coronary disease with subclinical ischemia caused by persistent tachycardia. Furthermore, the progression to developing cardiomyopathy may vary by age. Older patients may develop cardiomyopathy more rapidly, even if the rhythm is tolerated for years. 

Why some patients with tachycardia develop AIC and others do not remains unknown, but the problem of AIC may be greater than initially imagined when considering patients with atrial fibrillation and cardiomyopathy. It is unclear how many with persistent pathological tachycardia have no apparent problems for many years. This may be in part dependent on the rate, the AV relationship, ventricular dyssynchrony, and persistence of tachycardia. Much has yet to be learned about AIC. 

Alternatively, ablation is not risk free in patients with PJRT. There is risk of AV block with ablation of a posteroseptal pathway near the roof of the coronary sinus, risk of uncovering sinus node dysfunction, among others. In this case, both the EP team and the patient felt that the risks were worth taking. 

Disclosures: The authors have no conflicts of interest to report regarding the content herein. Outside the submitted work, Dr. Olshansky reports he is a speaker and consultant for Lundbeck, Chair of the REDUCE-IT DSMB for Amarin, consultant for Sanofi-Aventis and Respicardia, and U.S. co-coordinator of GLORIA-AF registry for Boehringer Ingelheim. 

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