Mohan Nair

Radiofrequency Catheter Ablation of Type 1 Atrial Flutter Prediction of Late Success by Electrophysiological Criteria

BACKGROUNDnRadiofrequency energy has demonstrated its efficacy in catheter ablation of atrial flutter (AFl). However, long-term recurrences of AFl have been reported frequently after initial, apparently successful ablation. To date, criteria for prediction of late recurrences are lacking.nnnMETHODS AND RESULTSnTwelve patients (10 men; mean age, 53.6 years; range, 26 to 69 years) were referred for AFl ablation. Duodecapolar and decapolar catheters were used for detailed mapping of the tricuspid ring, the inferior vena cavatricuspid annulus (IVC-TA) isthmus, and the coronary sinus ostium (CSOs) area. Additional multipolar catheters were used for recording activation of the coronary sinus and the CSOs-TA isthmus. AFl was present at baseline in 9 patients and was induced by proximal coronary sinus (PCS) pacing in 3. Counterclockwise right atrial activation was recorded in all patients. Primary success of ablation was defined as when AFl was no longer inducible even during isoproterenol infusion. AFl was successfully ablated in all 12 patients, with a median of 4 pulses delivered at the IVC-TA isthmus. In the 3 patients in whom AFl was induced, during PCS pacing in sinus rhythm before ablation, a collision of descending and ascending wave fronts was observed at the middle lateral right atrium (LRA). This activation pattern of the LRA also was noted after unsuccessful radiofrequency applications. Noninducibility of AFl after radiofrequency applications was associated with a change of activation pattern at the LRA and with an inversion of the activation sequence of the IVC-TA isthmus (from clockwise to counterclockwise) in 9 patients when pacing from the PCS. In 2 of 3 patients, despite noninducibility of atrial flutter, ablation was pursued to obtain evidence of permanent block of conduction at the IVC-TA isthmus. Finally, a completely descending LRA wave front was observed when pacing from the PCS in all patients except one. Low LRA pacing was also performed in 4 patients and showed evidence for block in the counterclockwise direction at the isthmus. During a follow-up of 9 +/- 3 months, AFl recurred in 1 patient; this was the only patient who showed no conduction block at the isthmus after the procedure.nnnCONCLUSIONSnDirection of impulse propagation at LRA and block of propagation at the IVC-TA isthmus during PCS and low LRA pacing appear to be of interest in predicting long-term success of AFl ablation.

Radiofrequency Catheter Ablation of Atrial Flutter Further Insights Into the Various Types of Isthmus Block: Application to Ablation During Sinus Rhythm

BACKGROUNDnRadiofrequency ablation of type 1 atrial flutter (AF1) has recently evolved toward an anatomically guided procedure directed to isthmuses at the lower part of the right atrium (RA). However, different types of block at these isthmuses may be observed and potentially correlated with different late outcomes. In addition, because the ablation is anatomically guided, ablation should be possible during sinus rhythm.nnnMETHODS AND RESULTSnForty-four patients underwent ablation of type 1 AF1 performed during ongoing tachycardia (33 patients) or sinus rhythm (11 patients). Evidence of inferior vena cava-tricuspid annulus isthmus block was assessed by changes in RA impulse propagation while pacing from both sides of the ablation site. Apparent complete isthmus block was achieved in 43 of 44 patients with 9 +/- 7 pulses. However, incomplete block mimicking complete block because of intra-atrial conduction delay but leading to a different low RA activation pattern was individualized. At the end of the procedure, isthmus block was complete in 35 patients and incomplete in 8, but since AF1 reinduction was no longer possible, patients were discharged. During a follow-up period of 12.1 +/- 5.5 months, 4 patients experienced AF1 recurrence; all had shown incomplete or no block.nnnCONCLUSIONSnDetailed multiple-point low RA mapping is necessary to differentiate incomplete from complete isthmus block. Complete block is the best marker for long-term success of AF1 ablation, although incomplete block may be sufficient to prevent recurrence in a significant number of cases. Isthmus block is achievable during sinus rhythm, and AF1 induction is not mandatory.

ELECTROCARDIOGRAPHIC PATTERNS AND RESULTS OF RADIOFREQUENCY CATHETER ABLATION OF CLOCKWISE TYPE I ATRIAL FLUTTER

Clockwise Rotation of Atrial Flutter. Introduction: Counterclockwise right atrial propagation is usually observed in common atrial flutter, but little is known regarding flutter with clockwise right atrial rotation. The aim of this study is to describe the ECG characteristics and results of catheter ablation of atrial flutter with clockwise right atrial rotation.

Automatic Arrhythmia Identification Using Analysis of the Atrioventricular Association Application to a New Generation of Implantable Defibrillators

BACKGROUNDnAtrioventricular association is a key criterion for arrhythmia diagnosis. Its use in a defibrillator should significantly reduce the incidence of inappropriate shocks. Therefore, we evaluated the diagnostic accuracy of an algorithm that uses dual-chamber sensing and analysis of atrioventricular association to discriminate ventricular from supraventricular arrhythmias in a prototype of an implantable defibrillator.nnnMETHODS AND RESULTSnThe algorithm performed a stepwise analysis of arrhythmias. The rhythm was first classified on the basis of cycle lengths. Each episode was then classified as supraventricular or ventricular in origin on the basis of the stability of cycle lengths and atrioventricular association. This algorithm was evaluated in 156 episodes of induced sustained tachycardias. Eighty-nine tachycardias were taken from the Ann Arbor electrogram library; the others were recorded in 50 patients during electrophysiological studies. The atrial and ventricular signals were stored on an external recorder and then injected into an external prototype of a defibrillator system. The algorithm correctly diagnosed 96% of ventricular tachycardia episodes, 100% of ventricular fibrillation episodes, and 92% of double-tachycardia episodes. The mean detection time for ventricular tachycardia was 2.6 +/- 0.8 seconds, and for ventricular fibrillation, it was 2.1 +/- 0.4 seconds. The positive predictive values for the diagnoses of atrial fibrillation and atrial flutter were 92% and 86%, respectively. For ventricular tachycardia and ventricular fibrillation, the values were 95% and 100%, respectively.nnnCONCLUSIONSnAnalysis of atrioventricular association promotes reliable differentiation between ventricular and supraventricular tachycardias and should enhance the diagnostic capabilities of implantable defibrillators.

Results of Radiofrequency Ablation of Permanent Atrial Fibrillation of > 2 Years Duration and Left Atrial Size >5 cm Using 2-mm Irrigated Tip Ablation Catheter and Targeting Areas of Complex Fractionated Atrial Electrograms

Complex fractionated atrial electrograms (CFAEs) have shown promise as target sites for ablation of atrial fibrillation (AF); however, the data are limited with regard to patients with a large left atrium (LA) (>5 cm), and/or a permanent AF duration of >2 years. We tested the hypothesis that ablation of user-defined, computer-generated CFAE and pulmonary vein isolation, without additional lines would help long-term maintenance of sinus rhythm (SR). A total of 21 patients, 9 men and 12 women, aged 32 to 78 years (mean 44 +/- 3.3) were selected. All had chronic AF for >2 years (range 2 to 20; mean 3.8) and a LA of 5.3 to 11.3 cm (mean 6.4 cm). The underlying structural heart disease was rheumatic mitral valve disease in 18, aortic stenosis in 1, and hypertension in 2. Mapping and ablation was done using the NAVx Ensite system and a 2-mm-tip IBI Therapy Cool Path ablation catheter. The target included circumferential pulmonary vein ablation and elimination of areas in the LA and proximal coronary sinus showing CFAEs. During ablation, 3 patients converted to SR. In 15 others, significant organization of the atrial activity occurred. They then underwent successful electrical cardioversion. Three patients showed no change in atrial activity nor had electrical cardioversion. No procedural complications occurred. Patients took oral amiodarone for 3 months after the procedure. At 3 to 12 months (mean 9.8) of follow-up, 3 patients who were in AF at the end of the ablation procedure continued to be in AF. Of the rest, all but 3 were able to maintain SR without antiarrhythmic drugs. In conclusion, ablation using a 2-mm tip irrigation catheter, targeting user-defined CFAEs and pulmonary vein isolation facilitated maintenance of SR in most patients with a LA >5 cm and an AF duration of >2 years.

Radio frequency ablation for VT--a cost-effective tool to combat SCD in developing countries.

The primary focus of ventricular tachycardia (VT) management is the assessment of subsequent risk of sudden death and its prevention, followed by management of symptomatic arrhythmias. n nAntiarrhythmic drugs usually do not provide sufficient protection from sudden death, but do have a role in reducing arrhythmias that cause symptoms. Role of catheter ablation for the management of VT comes in various clinical settings. Some patients might not need ICDs at all. Idiopathic VT generally has a benign prognosis and in the absence of structural heart disease, symptomatic patients can undergo stand-alone ablation without need for an ICD. n nCatheter ablation is a reasonable first-line therapy for many symptomatic idiopathic ventricular tachycardia.1 Patients with polymorphic VT and VF can have a triggering PVC originating from Purkinje fibers or from the right ventricular outflow. Perhaps those patients can have an excellent prognosis with focal catheter ablation and can be saved from the financial burden of ICD. n nIt is generally recognized that ablation of VT in the setting of structural heart disease is more difficult than ablation of idiopathic VT. In patients with structural heart disease, adequate tissue ablation is often difficult to achieve due to the presence of relatively large re-entrant circuits that they may be located deep in the myocardium and patients have multiple re-entrant circuits, which further complicate the procedure. n nCatheter ablation of VT in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy was shown to be associated with high acute procedural success and good intermediate-term outcomes with the use of non-contact electro anatomical mapping systems to guide the ablation.2 Better understanding of arrhythmia mechanism and demonstration of cardiac anatomy from use of electro anatomic mapping systems, intracardiac echocardiography, and pre acquired MRI or CT images incorporated into mapping systems are improving ablation therapy. n nPatients with a substantial risk of sudden death usually need an ICD. ICDs effectively treat most episodes of ventricular tachycardia or ventricular fibrillation and decrease mortality in patients who are at high risk of sudden cardiac death but they also have inherent risks and limitations.3 Approximately 20% of patients in primary prevention and 45% of patients in secondary prevention receive an appropriate ICD intervention within the 2 years following ICD implantation.4–6 n nAlthough ICDs have been shown to improve survival when placed for primary or secondary prevention in the presence of structural heart disease, ICDs are not a cure for VT and do not prevent recurrence of arrhythmias. Catheter ablation of ventricular arrhythmias plays a big role in some patients with ICD who are having recurrent shocks and may even be curative for some patients. Ablation can be life saving for patients with very frequent or incessant ventricular tachycardia. Electrical storm has been defined as three or more separate episodes of VT within a 24xa0h period and has been associated with increased mortality in patients with ICDs and may affect 4% and 20% of the patients in the primary and secondary prevention, respectively.7,8 These are usually scar-related re-entrant ventricular tachycardias that can cause hemodynamic collapse, which prevents extensive mapping during ventricular tachycardia. To avoid hemodynamic compromise, substrate mapping during stable sinus rhythm is often used to identify the area of scar and probable arrhythmia origin from electrogram characteristics. In patients presenting with electrical storm, catheter ablation may serve as the only viable treatment option if antiarrhythmic therapy fails. n nNow the question is whether catheter ablation can eliminate the need for an ICD? Cost of catheter ablation is much less than the cost of ICD and in a developing country like India, cost-effectiveness is extremely relevant. n nTo date, results of two randomized prospective multicentre studies have been published in patients with ischemic cardiomyopathy and VT undergoing prophylactic catheter ablation to prevent further VT. n nThe SMASH-VT study9 assessed the role of catheter ablation in 128 patients (64 patients in each group) with previous myocardial infarction and reduced LV ejection fraction undergoing ICD implantation for secondary prevention of sudden cardiac death. None of the patients received Class I or III antiarrhythmic drug therapy. The control arm underwent ICD implantation only. Importantly, catheter ablation was performed utilizing a substrate-guided approach. During an average follow-up period of 22.5xa0±xa05.5 months, there was a significant decrease in appropriate ICD therapy in the ablation group compared with the control arm (12 vs. 33%, pxa0=xa00.007). In addition, the number of appropriate shock deliveries was reduced and there was a trend to a reduction in the number of patients with electrical storm. The number of patients that needed to be treated with ablation (NNT) to avoid 1 appropriate ICD intervention was 5, resulting in a total of 200 appropriate ICD interventions prevented every 1000 patients treated with catheter ablation. n nThe other multicentre VTACH study,10 assessed the role of VT ablation in patients with prior myocardial infarction, reduced EFxa0≤xa050%, and haemodynamically stable VT. One hundred and ten patients were prospectively randomized to ICD only or VT ablation at the time of ICD implantation. Ablation was guided by a combination of substrate mapping, activation mapping, and pace mapping. The use of antiarrhythmic medication was at the discretion of the treating physician. The median time to first recurrence of ventricular arrhythmias was longer in the ablation group than the ICD only group (18.6 vs. 5.9 months). There was a significantly better rate of survival free from recurrent VT in the ablation group (47 vs. 29%, hazard ratioxa0=xa00.61, pxa0=xa00.045). Upon subgroup analysis, patients with an EF of ≤30% derived no benefit from catheter ablation, while patients with an EF of >30% demonstrated a statistically significant decrease in arrhythmia recurrence. Some recent studies demonstrated that a more extensive substrate ablation targeting local abnormal ventricular activities, late potential and also goingxa0xa0for epicardial ablation were associated with a very favorable outcome approaching around 85% freedom from any VT at 2 years follow up and with a more limited use of antiarrhythmics.11–13 n nExtensive endo-epicardial substrate based ablation concepts targeting all the potential VT circuits within the scar can increase the procedural success in patients with infarct-related VT. Study involving newer ablation techniques as first-line therapy can answer the question about the role of ICD implantation in these patients. n nThough not well established by randomized data, selected patients with stable VT, and relatively preserved LV function generally have a sufficiently good prognosis to undergo ablation as a stand-alone therapy without placing an ICD and two to three cases can be done with a single patch/catheter to bring the cost further down. Patient with sustained monomorphic scar-related VT may be treated with ablation early in its clinical course. Early referral for catheter ablation following ICD intervention has the potential to decrease arrhythmia recurrence and ICD intervention. Available data do not allow conclusion on the impact of primary VT ablation on mortality and further studies are required. n nThe concept of prophylactic catheter ablation before ICD implantation has special implications for countries such as India as a) it reduces device therapy therefore increasing quality of life and device longevity b) patients may require less costly and sophisticated device and c) with increasing experience and evidence, catheter ablation has the potential for being “stand alone” in selected patients with structural heart disease and risk of SCD.

A supraventricular tachycardia with two atrial activation sequences: What is the mechanism?

Case presentation A 62-year-old woman presented with a history of paroxysmal regular palpitations. She did not have any structural heart disease. Treatment with antiarrhythmic drugs was stopped 5 half-lives before the electrophysiological study. Basic intervals were normal. On right ventricular (RV) apical pacing 500 ms in the basal state, the ventriculoatrial (VA) conduction pattern was distal to proximal in the coronary sinus (CS) and the earliest atrial signal (A) was in the His bundle electrogram (Figure 1A). The VA block cycle length was 410 ms. During isoprenaline infusion, the VA block cycle length was 300 ms, with the earliest A at the His and a CS atrial activation pattern that was proximal to distal (Figure 1B). During infusion of isoprenaline, a sustained narrow-QRS tachycardia with 1:1 VA relationship started spontaneously. The initiation was with a spontaneous atrial premature depolarization (Figure 2), and termination was with a ventricular signal (V). The tachycardia cycle length (VV) and HH interval were constant at 320 ms. However, the CS activation sequence was distal to proximal at times and proximal to distal at other times. The VA interval changed from 130 to 156 ms as the CS activation pattern switched from a distal-to-proximal pattern to a proximal-to-distal one (Figure 3). What is the tachycardia mechanism?