|Year : 2015 | Volume
| Issue : 2 | Page : 85-88
Review of Outcomes of Eighty-two cases of Typical AVNRT after Radiofrequency Ablation at Madras Medical Mission, India
Kelechukwu Uwanuruochi1, Sabari Saravanan2, Anita Ganasekar3, Benjamin Solomon4, Ravikumar Murugesan4, Ruchit A Shah5, Jaishankar Krishnamoorthy6, Ulhas Pandurangi6
1 Department of Medicine, Federal Medical Centre, Umuahia, Nigeria; Department of Cardiac Electrophysiology, Institute of Cardio-Vascular Diseases, Chennai, India
2 Clinical Engineer, Electrophysiology and Biomedical Engineering, St. Jude Medical, Chennai, Tamil Nadu, India
3 Department of Cardiac Electrophysiology, Institute of Cardio-Vascular Diseases, Chennai, India
4 Laboratory Technology, Institute of Cardio-Vascular Diseases, Chennai, India
5 Department of Medicine, Madras Medical Mission, Chennai, India
6 Department of Cardiology, Institute of Cardio-Vascular Diseases, Chennai, India
|Date of Web Publication||30-Jul-2015|
Department of Medicine, Federal Medical Centre, Umuahia, Abia, Nigeria
Source of Support: None, Conflict of Interest: None
Context: Diagnoses of supraventricular arrhythmias often depend on combination of varied features of baseline electrophysiology, tachycardia and responses to pacing manoeuvres. These investigations are carried out regularly at the Cardiac Catheterization Laboratory of Madras Medical Mission, India.
Aims: The purpose of this study was to describe the initial outcome following cardiac electrophysiologic studies and radiofrequency ablation of typical atrio-ventricular nodal re-entrant tachycardia (AVNRT).
Settings and Design: This retrospective study was carried out in the Cardiac Electrophysiology Department, of the Institute of Cardiovascular Diseases, Madras Medical Mission, India.
Subjects and Methods: Records of consecutive cases of typical AVNRT following cardiac electrophysiologic studies and radiofrequency ablation carried out between May 2013 to April 2014 were reviewed. Eighty-two cases were chosen for analysis.
Statistical analysis used: The data obtained were analysed using SPSS statistical software version 15.
Results: The 82 patients comprised 24 males and 58 females. Dual nodal physiology was documented in 79 (96.3%), A simultaneous V and A (VA interval <20 ms) was documented in 66 (80.5%). The presence of ventricular-atrial dissociation (VAD) during ventricular overdrive pacing (VOP), post-VOP V-A-V response, termination of tachycardia by VOP without advancing A, absence of VA linking and failure of His-refractory premature ventricular complex (PVC) to advance A were other characteristics used in differential diagnosis. The slow pathway was successfully ablated in 52 (63.4%), successfully modified in 29 (35.4%). The overall success rate was 98.8% while radiofrequency ablation was unsuccessful in 1 (1.2%). There was a very low incidence of complications.
Conclusions: Treatment of typical AVNRT by radiofrequency cardiac catheter ablation at the Madras Medical Mission is highly effective and safe.
Keywords: Initial outcome, madras medical mission, review, typical AVNRT
|How to cite this article:|
Uwanuruochi K, Saravanan S, Ganasekar A, Solomon B, Murugesan R, Shah RA, Krishnamoorthy J, Pandurangi U. Review of Outcomes of Eighty-two cases of Typical AVNRT after Radiofrequency Ablation at Madras Medical Mission, India. Nig J Cardiol 2015;12:85-8
|How to cite this URL:|
Uwanuruochi K, Saravanan S, Ganasekar A, Solomon B, Murugesan R, Shah RA, Krishnamoorthy J, Pandurangi U. Review of Outcomes of Eighty-two cases of Typical AVNRT after Radiofrequency Ablation at Madras Medical Mission, India. Nig J Cardiol [serial online] 2015 [cited 2021 Jan 15];12:85-8. Available from: https://www.nigjcardiol.org/text.asp?2015/12/2/85/152015
| Introduction|| |
The field of clinical cardiac electrophysiology has evolved dramatically over the last 30 years, beginning with description of the first His bundle recording in 1969, use to diagnose and guide drug treatment of arrhythmias in the early 1970s, electrically mapping and surgical ablation of arrhythmias during the late 1970s and 1980s to radiofrequency catheter ablation (RFCA) for treatment of most forms of supraventricular tachycardia and idiopathic ventricular tachycardia in 1990s. ,, The field is still evolving, and requires appreciation of variety of protocols applied in its investigations.
The increasing prevalence of cardiovascular disease driven by socio-economic factors implies that more patients will develop cardiac arrhythmias.
There is need for physicians to appreciate the success rate and outcome following radiofrequency ablation of various arrhythmias. This will result affect referral by physicians of patients that require these studies, especially as facilities are not available in most centers in Sub-Saharan Africa.
In this study, we described the initial outcome in terms of success rate as well as early complications following diagnosis and treatment of typical atrio-ventricular nodal re-entrant tachycardia (AVNRT) by radiofrequency ablation as seen at a Cardiac Electrophysiology Department in Madras Medical Mission, Chennai, India.
| Subjects and methods|| |
The study was carried out at the Cardiac Electrophysiology department, of the Institute of Cardiovascular diseases, Madras Medical Mission, India. Ethical approval was obtained. The study was entirely retrospective and consisted of review of the database the records of the Cardiac Electrophysiology department. We studied the database of consecutive Typical AVNRT diagnosed following cardiac electrophysiology studies carried out between 29 th May 2013 to 17 th March 2014 with respect to clinical, demographic and procedural parameters.
In our study, we described the demographic characteristics of the patients, the indications for the procedure, the prevalence of associated cardiovascular morbidity in the patients, the proportion of the patients with documented tachycardia on electrocardiograph (ECG) tracings, dual atrio-ventricular (AV) nodal physiology and inducible tachycardia. We also observed the baseline characteristics on electrophysiology study, tachycardia features, response to radiofrequency ablation, changes post-ablation, and outcome of ablation. Where utilized, the responses to Adenosine, as well as to pacing maneuvers were documented.
The diagnosis of AVNRT was based on the presence of jump and echo initiating tachycardia during programmed atrial stimulation and/or during incremental atrial pacing close to the Wenckebach point, supplemented as needed by discrimination pacing maneuvers. These maneuvers include ventricular overdrive pacing (VOP), delivery of His-synchronous ventricular premature complex, delivery of premature ventricular extrastimuli during tachycardia, adenosine infusion to exclude accessory pathway and atial tachycardia (AT) and observation for ventriculo-atrial (VA) linkage during tachycardia.
The percentage of cases needing repeat radiofrequency ablations and the frequency of the early complications of radiofrequency ablation were documented. Catheters used were quadripolar 6F for the high right atrium, his bundle, and the right ventricular apex, and THR CURVE STD 7F EPT BLAZER for the ablator. Three-dimensional (3D) electro anatomical mapping (ST JUDE ENSITE VELOCITY) was used in 20 of the 80 cases, while the standard electroanatomical mapping was used in the rest. No fluoroscopy was used in 14 cases. The mean fluoroscopy time was 11.43 ± 5.86 minutes.
Ablation was performed using 6F with power set at 50 Watts and temperature at 60°. The mean fluoroscopy was 11.52 ± 5.89 minutes. The primary endpoint of ablation procedure was non-inducibility of the arrhythmia, ablation or modification of slow pathway which included the presence of a jump, echo or both. Acute success of RFA was defined as non-induscibility of AVNRT without the presence of jump and echo (ablation), or the presence of a single jump and/or echo (modification). The data was analyzed using SPSS statistical software version 15 (SPSS, Inc. Chicago Illinois).
| Results|| |
Eighty-two consecutive cases of typical AVNRT diagnosed following electrophysiologic studies were selected for reviewed. They consisted of 24 males and 58 females with mean age of 46.34 years (±15.46). The minimum age was 11, while the maximum was 80 years.
While all patients had typical AVNRT, the case of tachycardia was mixed in three patients, in combination with right posteroseptal atrioventricuar reentrant tachycardia (AVRT) in two, and with Sick Sinus Syndrome in one.
The frequency of associated cardiovascular diseases in the patients studied are coronary heart disease 11 (13.75%), hypertension 8 (10.00%), diabetes mellitus 9 (11.3%), hypothyroidism 2 (2.6%), sickle cell disease 1 (1.3%), atrial septal defect 1 (1.3%), and mitral valve prolapse 1 (1.3%).
The indications for radiofrequency ablation were drug refractory arrhythmias in all but two cases of recurrence following previous slow pathway ablation. Prior to electrophysiologic study, 78 patients had a narrow QRS tachycardia documented, 1 patient ECG showed both regular narrow QRS as well as regular wide QRS [left bundle branch block (LBBB)] pattern. There was no documented tachycardia in three cases.
Dual nodal physiology [Figure 1] was documented in 79 (96.3%), but absent in 3 (3.7%) of the patients.
A simultaneous V and A (VA interval <20 ms) was documented in 66 (80.5%) of the cases.
Both Ventricular-atrial dissociation (VAD) during ventricular overdrive pacing (VOP) and post-VOP V-A-V response was recorded in three (3.66%) patients, two of whom lacked dual nodal physiology.
The followings were all documented in only one patient: Termination of tachycardia by VOP without advancing A, absence of VA linking-the two in a patient whose ECG raised suspicion of atrial tachycardia (AT) and failure of His-refractory premature ventricular complex (PVC) to advance atrial depolarization (A).
A narrow QRS tachycardia was inducible in 76 (92.7%) of the patients. The six patients with no sustained tachycardia all had dual node physiology. Adenosine was used in two of them, wherein absence of AV/VA conduction excluded an accessory pathway.
The site of radiofrequency catheter ablation was the posterior-inferior region of Koch's triangle in all but one patient, in whom radiofrequency energies delivered in and around Coronary sinus (CS) ostial region resulted in junctional rhythm. Few radiofrequency energies were used (temperature 60°, 50 watts, 60-120 seconds).
Post-ablation, dual nodal physiology was still observable in 21 patients (25.6%), but non-sustained tachycardia on Isopril was noted in only one patient (1.2%), in which case the plan was to repeat radiofrequency ablation with or without permanent pacemaker implantation if symptoms recurred.
The slow pathway was successfully ablated in 52 (63.4%) patients, but deemed modified in 29 (35.4%). In one patient (1.2%) ablation was complicated by high grade AV block which converted to AV Wenckebach and subsequently to 1:1 AV conduction, sinus rhythm. In one patient, attempts to modify the slow pathway would result in atrial fibrillation/atrial flutter and the procedure was deferred to consider permanent pacemaker insertion with or without AV node ablation.
| Discussion|| |
This study describes cases of AVNRT at the Electrophysiology Department of Madras Medical Mission investigated between 29 th May 2013 and 17 th March 2014.
The mean fluoroscopy time of 11.43 ± 5.86 minutes compares favorable to a mean radiation times of 13 ± 12 minutes used by Klug et al.,  in single radiofrequency applications to AVNRT and 10 ± 5.4 minutes reported by Taheen et al. 
Ninety-six percent of the patients with AVNRT had dual nodal physiology. Dual AV nodal pathways have been defined as greater than 50 ms jump in atrio-hisian (AH) interval a 10 ms decrease in A1-A2.  This is explained on the ground that there are two pathways in the AVN. As the electrical extra-stimuli is introduced progressively, increasingly early, at a point conduction through the nodal fast pathway is blocked because it is refractory, but the conduction now travels through the slow pathway, leading to the sudden and significant increase in the AH interval. Dual nodal physiology was absent in 3.7% of our patients. It is known that not all patients with AVNRT show dual nodal physiology, and that it may also be present in non-AVNRT tachycardias. 
Reported frequency rates for dual nodal pathways has varied in different studies. Jazayeri et al.,  found dual pathways 63.71% before and 24.77% after ablation, while Ibrahim et al.,  found jump presence of 54.2% in AVNRT patients before ablation and 11.4% after. Tai and colleagues  found 95.1% dual pathways in 474 patients with AVNRT. The use of multiple-drive cycle lengths, multiple catheters, rapid atrial pacing, and isoprenaline most likely explains the high frequencies reported in our study.
This study shows that radiofrequency ablation of AVNRT was highly effective, and also associated with low frequency of acute complications. It was successful in 98.8%. The slow pathway was completely ablated in 63.4% and successfully modified in 35.4%. It was unsuccessful in 1.2%. This compares favourably with 98% successful ablation recorded in Turkey by Ibrahim et al.,  in patients with AVNRT and 99.9% reported by Yu et al.,  Topilski et al.,  also achieved slow pathway ablation in 51.5% and slow pathway modification in 46.9% while in the remaining 14 patients (1.6%) various combinations of pathways were ablated. Ablation was unsuccessful in one patient (1.2%). This also compares to the rate of 1.1% reported by Topilski et al. 
There was also a low incidence of complications. None of the patients had major complications such as stroke, myocardial infarction, deep venous thrombosis with pulmonary embolus and pericardial effusionor cardiac tamponade. The only complication recorded was temporary high grade AV block and the frequency at 1.2% was low. Transients or permanent AV block has varied from 3.4-0.66% in various studies. ,
sOther characteristics that were used in a minority of the patients included ventriculo-atrial dissociation (VAD) during ventricular-overdrive pacing (VOP) (3.7%), termination of tachycardia without advancing A (1.2%) and VA linking during VOP (1.2%), post-VOP response (3.7%), and response to His-refractory PVC (1.2%) and adenosine infusion (2.4%). The role of these maneuvers in excluding differentials is important. VAD during VOP implies that the ventricle is not part of tachycardia circuit.  This excludes AVRT where the ventricle is an essential part of the circuit, tachycardia termination during VOP without depolarization of the atrium excludes AT because to terminate an AT, the atrium has to be depolarized as it is the site of origin of the tachycardia;  VA linking would not be expected in AT because atrial activation is not dependent on ventricular activation, as the reentry is wholly in atrium, so VA during AT will differ from that during overdrive pacing,  and so absence of VA linking excludes AT. In AVNRT or AVRT, after last paced V the ventricle and then the atrium are again activated by continuation through the re-entrant loop, hence a V-A-V. In AT, after the last paced V-A, while the AVN is still refractory an A from the AT focus follows before V, hence V-A-A-V response.  A His-refractory PVC is delivered within 40 ms of the His potential, when the His is still refractory. If the subsequent atrial signal arrives earlier than expected, the conduction to atria must be through an AP as the His was refractory. It is also advanced (arrives faster) because there is no delay in AVN. Thus failure of His-refractory premature ventricular complex (PVC) to advance A rules out AVRT.  Finally, Adenosine infusion was used in patients in whom arrhythmias was not inducible, to exclude an accessory pathway. By inducing AV block (AVB), adenosine can enhance pre-excitation owing to conduction down an accessory pathway. In tachycardias of atrial origin it can also slow the ventricular rate and revealing the unaffected atrial arrhythmia. 
The Wide QRS in a case of typical AVNRT was explained by the associated typical LBBB pattern to be catheter induced. Bundle branch block is a known complication of cardiac catheterization. 
In conclusion, radiofrequency ablation of AVNRT at the Madras Medical Mission is highly effective and associated with low risk of complications centers. Of the patients reviewed, the slow pathway was successfully ablated in 63.4%, successfully modified in 35.4%, and unsuccessful in 1.2%. Significant complication was seen also in 1.2%. This recommends development of cardiac electrophysiology in areas where this facility is not available.
The retrospective nature that made it difficult to fill up missing data, and to correct errors in documentations. The nationalities of the patients were not included in the data collected.
The Medical Director of Federal Medical Centre Umuahia, Dr. Abali Chuku and the Staff of the Electrophysiology clinical research office of Madras Medical Mission.
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