International Journal of Heart Rhythm

: 2021  |  Volume : 6  |  Issue : 2  |  Page : 90--92

A decremental response seen to a his refractory premature ventricular complex in a patient with short ventriculoatrial interval: A case report

Khalil Kanjwal1, Asim Kichloo2, Muzaffar Ali3, Abdul Qadir Haji4,  
1 Department of Electrophysiology, McLaren Greater Lansing Hospital, Lansing, MI, USA
2 Department of Internal Medicine, Samaritan Medical Center, Watertown, NY, USA
3 Department of Electrophysiology, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India
4 Department of Electrophysiology, Walter Reed National Medical Center, Bethesda, MD, USA

Correspondence Address:
Dr. Khalil Kanjwal
Department of Electrophysiology, McLaren Greater Lansing Hospital, Lansing, MI 48901


We report on a patient with supraventricular tachycardia, mediated through a left posterior concealed accessory pathway (AP). During an electrophysiology study, the His refractory premature ventricular complex (PVC) delayed in the next atrial signal and was suggestive of the decremental pathway; however, further maneuvers and tachycardia features were suggestive of a nondecremental AP. In this paper, we discuss possible mechanisms of this interesting observation of decremental response to PVC in an otherwise nondecremental AP.

How to cite this article:
Kanjwal K, Kichloo A, Ali M, Haji AQ. A decremental response seen to a his refractory premature ventricular complex in a patient with short ventriculoatrial interval: A case report.Int J Heart Rhythm 2021;6:90-92

How to cite this URL:
Kanjwal K, Kichloo A, Ali M, Haji AQ. A decremental response seen to a his refractory premature ventricular complex in a patient with short ventriculoatrial interval: A case report. Int J Heart Rhythm [serial online] 2021 [cited 2022 Jul 2 ];6:90-92
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Full Text


A deep knowledge of various maneuvers performed during the electrophysiology study (EPS) for supraventricular tachycardia (SVT) is important for establishing the correct mechanism of the tachycardia before the ablation is performed. His refractory premature ventricular complex (PVC) usually is used to ascertain the participation of the pathway in the tachycardia mechanism. In our patient, the His refractory PVC delayed the next atrial signal, which was suggestive of the decremental accessory pathway (AP). However, there were other tachycardia features which would argue against the mechanism of the tachycardia being decremental AP. This case is unique as we saw a very unusual response to His refractory PVC.

 Case Report

A 30-year-old male with no significant past history came to the arrhythmia clinic for recurrent palpitations. These episodes of palpitations were sudden in onset and would terminate with vagal maneuvers. The patient had three emergency room visits in last few months, but these episodes would terminate before he would arrive in the emergency room. His baseline electrocardiogram was without any preexcitation. Given the history of recurrent palpitations, the patient was offered EPS.

The patient arrived in the EP laboratory in postabsorptive state. Bilateral femoral vein access was obtained using ultrasound guidance. Three venous sheaths were inserted in the right femoral vein and two in the left femoral vein. EP catheters were advanced to the high right atrium, right ventricle, His, and coronary sinus (CS). Electrocardiograms showed sinus rhythm without any preexcitation [Figure 1]. Tachycardia with a cycle length (CL) of 448 ms was easily induced during catheter manipulation. The ventriculoatrial (VA) interval was 140 ms, and there was eccentric retrograde activation noted on CS with the earliest retrograde atrial signal noted on CS 5,6 electrode [Figure 2]. These findings were suggestive of left-sided posterior concealed AP. During tachycardia, a His refractory PVC was delivered which delayed (postexcited) the next A and this response was suggestive of decremental AP [Figure 2]. This response was seen consistently and was reproducible. The ventricular entrainment revealed a VAHV response with the corrected postpacing interval − tachycardia cycle length <120 ms and the stimulus-atrial (SA) interval minus VA interval <80 ms [Figure 3], which suggested the AP-mediated tachycardia. Although the His refractory PVC suggested a decremental AP, a short local VA interval on CS 5,6 during tachycardia suggested a nondecremental pathway. In a retrogradely conducting decremental AP, the VA interval is long. A transseptal puncture was performed, and the retrograde limb of the tachycardia circuit was mapped during the tachycardia. A force-sensing irrigation catheter from Biosense was used and a 35-W burn was delivered with immediate termination of the tachycardia [Figure 4]. The area of successful ablation site was tagged on the CARTO 3D mapping system. Ablation was continued for 1 min followed by an insurance burn for 30 s. Ventricular pacing postablation revealed concentric retrograde conduction. The patient was started on Isuprel, and programmed stimulation using extrastimuli failed to induce any tachycardia. The patient was seen in the clinic at 2 and 6 months after the procedure and did not have any palpitations.{Figure 1}{Figure 2}{Figure 3}{Figure 4}

The ethical approval was waived by the Ethical Review Board for presenting a case or case series. A signed consent form was obtained from the patient before the study as per the institutional regulations.


SVT affects more than half a million people each year.[1] The disorder can present at any age.[1],[2] SVT can cause significant symptoms of palpitations and frequent unexpected hospital visits. Radiofrequency ablation is a safe and effective treatment for SVT.[3] SVT has three types including atrioventricular nodal reentrant tachycardia (responsible for approximately 65% of cases), atrioventricular reciprocating tachycardia (responsible for approximately 30% of cases), and atrial tachycardia (responsible for approximately 5% of cases).[1],[2],[3],[4] The cure rate from radiofrequency ablation ranges from >70% for atrial tachycardia to over 95% for atrioventricular nodal reentrant tachycardia and atrioventricular reciprocating tachycardia.[5] EP study establishes the diagnoses and mechanism of SVT before any radiofrequency ablation is attempted, and it is vital to acknowledge that no single observation or maneuver used during EP study is 100% sensitive or specific. Therefore, it is vital to collect data from multiple observations and maneuvers, to verify the diagnosis before proceeding with ablation.

Delivering a His refractory PVC during tachycardia is one of those maneuvers.[4],[5],[6] If a His refractory PVC advances the atrium, it can only do so through a retrogradely conducting AP, because a PVC cannot conduct to the atrium through the HPS when it is refractory. When the tachycardia continues and is reset, the maneuver proves the participation of AP in the tachycardia. A PVC that terminates the tachycardia without conducting to the atrium must be causing it by a block in the AP, thus proving the presence and participation of the AP in the tachycardia. When a His refractory PVC delays the next atrial signal, the maneuver proves the participation of the decremental AP.

In our case, a His refractory PVC resulted in postexcitation which suggests a decrement in the retrograde limb of the tachycardia. However, there were other tachycardia features which would argue against the retrogradely conducting decremental AP. The decremental pathways usually have a long VA interval because of the slow and decremental conduction through a retrogradely conducting decremental pathway. We also observed that the local VA interval was short which would strongly argue against the pathway being decremental. Thus, response to His refractory PVC was only maneuver that was suggestive of a decremental pathway while all other observations suggested a nondecremental pathway.

Diagnostic maneuvers used during the EP study have some pitfalls and the maneuver of His refractory period is with no exception, as it is a powerful maneuver but not 100% specific and sensitive. There are few explanations that could help understand the mechanism of this response, which was observed in our patient. If the site from which the PVC is delivered is away from the tachycardia circuit, the PVC may fail to entrain the tachycardia and thus cannot advance the atrial signal despite the presence of an AP. The other factors that may influence the response to this maneuver include the ability of the PVC to affect the tachycardia circuit which would further depend on the conduction time from the ventricular stimulation site to the AP and the local ventricular refractory period. In our patient during a His refractory PVC, the local VA interval remained short, and the delay could have occurred from stimulation to the local V (AP insertion site) or from local A (AP insertion site) to the atrial signal in the high right atrium and not necessarily in the AP itself. These observations would argue against the decremental nature of AP in our patient.

One should attempt multiple maneuvers and acknowledge various forms of tachycardia features rather than rely on one maneuver, and it is vital to establish the understanding of the tachycardia as all these maneuvers lack 100% sensitivity/specificity.


When a His refractory PVC delivered during the SVT delays the next atrial signal, the participation of the decremental pathway should be confirmed by other tachycardia features and maneuvers used during EP study. Thus, ablationists need to have a sound knowledge of the maneuvers and should not rely on a single response as none of these responses has 100% specificity and sensitivity. One must be aware of various pitfalls of these maneuvers.

Institutional review board statement

The ethical approval was waived by the institutional review board of our hospital because of this being a single case report.

Declaration of patient consent

The authors certify that they have obtained the appropriate consent form from the patient. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initial will not be published and due efforts will be made to conceal his identity.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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