Phantom study of stereotactic radioablation for ventricular tachycardia (STRA-MI-VT) using Cyberknife Synchrony Respiratory Tracking System with a single fiducial marker.

PURPOSE: Within the STRA-MI-VT phase Ib/II trial (NCT04066517), the aim of this phantom study was to explore the feasibility of Cyberknife treatments on cardiac lesions by tracking as a single marker the lead tip of an implantable cardioverter defibrillator. The residual displacement of the lesion during the tracking was studied, planning margins were found and the dosimetric accuracy of the treatment was checked. MATERIALS AND METHODS: A lead was inserted into a phantom (EasyCube phantom, Sun Nuclear Co, USA) and then placed on the translating ExacTrac Gating System (BrainLAB AG, Germany). The phantom was rotated, a virtual lesion was identified and its displacement during the tracking was studied. Two plans were compared, calculated on the unrotated volume and on the envelope of the unrotated and the rotated volumes. The plans were delivered using the Cyberknife System (Accuray Inc, USA) and their dosimetric accuracy verified by gamma analysis with gafchromic films. RESULTS: The residual margin increases enhancing the distance between the lead and the lesion. It is 4 mm for distance 0 cm and 5 mm for distance 5 cm. The coverage is reduced by 3.8% (interquartile range 2.5%-4.7%) when the dose is prescribed on the unrotated volume. All treatment plans are accurate and 3% 3 mm gamma analysis results are greater than 94%. CONCLUSIONS: Results showed that tracking with a single marker is feasible considering adequate residual planning margins. The volumes could be further reduced by using additional markers, for example by placing them on the patient's skin.

STRA-MI-VT (STereotactic RadioAblation by Multimodal Imaging for Ventricular Tachycardia): rationale and design of an Italian experimental prospective study.

BACKGROUND: Ventricular tachycardia (VT) is a life-threatening condition, which usually implies the need of an implantable cardioverter defibrillator in combination with antiarrhythmic drugs and catheter ablation. Stereotactic body radiotherapy (SBRT) represents a common form of therapy in oncology, which has emerged as a well-tolerated and promising alternative option for the treatment of refractory VT in patients with structural heart disease. OBJECTIVE: In the STRA-MI-VT trial, we will investigate as primary endpoints safety and efficacy of SBRT for the treatment of recurrent VT in patients not eligible for catheter ablation. Secondary aim will be to evaluate SBRT effects on global mortality, changes in heart function, and in the quality of life during follow-up. METHODS: This is a spontaneous, prospective, experimental (phase Ib/II), open-label study (NCT04066517); 15 patients with structural heart disease and intractable VT will be enrolled within a 2-year period. Advanced multimodal cardiac imaging preceding chest CT-simulation will serve to elaborate the treatment plan on different linear accelerators with target and organs-at-risk definition. SBRT will consist in a single radioablation session of 25 Gy. Follow-up will last up to 12 months. CONCLUSIONS: We test the hypothesis that SBRT reduces the VT burden in a safe and effective way, leading to an improvement in quality of life and survival. If the results will be favorable, radioablation will turn into a potential alternative option for selected patients with an indication to VT ablation, based on the opportunity to treat ventricular arrhythmogenic substrates in a convenient and less-invasive manner.

Cardiac mesenchymal stromal cells are a source of adipocytes in arrhythmogenic cardiomyopathy.

AIM: Arrhythmogenic cardiomyopathy (ACM) is a genetic disorder mainly due to mutations in desmosomal genes, characterized by progressive fibro-adipose replacement of the myocardium, arrhythmias, and sudden death. It is still unclear which cell type is responsible for fibro-adipose substitution and which molecular mechanisms lead to this structural change. Cardiac mesenchymal stromal cells (C-MSC) are the most abundant cells in the heart, with propensity to differentiate into several cell types, including adipocytes, and their role in ACM is unknown. The aim of the present study was to investigate whether C-MSC contributed to excess adipocytes in patients with ACM. METHODS AND RESULTS: We found that, in ACM patients' explanted heart sections, cells actively differentiating into adipocytes are of mesenchymal origin. Therefore, we isolated C-MSC from endomyocardial biopsies of ACM and from not affected by arrhythmogenic cardiomyopathy (NON-ACM) (control) patients. We found that both ACM and control C-MSC express desmosomal genes, with ACM C-MSC showing lower expression of plakophilin (PKP2) protein vs. CONTROLS: Arrhythmogenic cardiomyopathy C-MSC cultured in adipogenic medium accumulated more lipid droplets than controls. Accordingly, the expression of adipogenic genes was higher in ACM vs. NON-ACM C-MSC, while expression of cell cycle and anti-adipogenic genes was lower. Both lipid accumulation and transcription reprogramming were dependent on PKP2 deficiency. CONCLUSIONS: Cardiac mesenchymal stromal cells contribute to the adipogenic substitution observed in ACM patients' hearts. Moreover, C-MSC from ACM patients recapitulate the features of ACM adipogenesis, representing a novel, scalable, patient-specific in vitro tool for future mechanistic studies.

Intracardiac echocardiography in electrophysiology.

Intracardiac echocardiography (ICE) is a recent, invaluable tool which can provide real-time anatomical guidance in electrophysiological procedures. By inserting intravenously an ultrasound probe and advancing it into the heart, various different views can be obtained which allow to better visualize patient anatomy, to guide the placement of electrophysiological catheters, and to detect immediately procedural complications as they occur. In atrial fibrillation ablation, ICE proves particularly useful to achieve a safer trans-septal puncture (especially in the presence of anatomical anomalies of the interatrial septum) and to help to monitor the visualization of the mapping catheters (circular, high density), or the monitoring of the balloons catheter (Cryo, Laser) position. In ventricular tachycardia ablation, on the other hand, ICE allows for continuous correlation between electrophysiological and structural findings (such as wall motion anomalies or changes in echodensity), and helps to ensure correct catheter contact and to position it, particularly around delicate structures such as the aortic cusps. In any procedure, ICE is also useful to immediately detect procedural complications, such as thrombus formation along catheters, or pericardial effusion. Thanks to its real-time morphological information, ICE provides an ideal complement to simple fluoroscopy or to more complex electroanatomic mapping techniques and is set to gain a wider role in a broad range of electrophysiological procedures.

Non-contact left ventricular endocardial mapping for cardiac resynchronisation therapy: a "slow conduction" towards the fast solution.

Cardiac resynchronisation therapy can help to improve left ventricular function in patients with heart failure, but only if those regions of myocardium which are mostly compromised by electromechanical desynchronisation can be identified and effectively stimulated.

Atypical atrial flutter: clinical features, electrophysiological characteristics and response to radiofrequency catheter ablation.

AIMS: To evaluate the clinical and electrophysiological features of atypical atrial flutter (AAF) and its response to radiofrequency catheter ablation. METHODS AND RESULTS: In 90 consecutive patients referred for sustained atrial flutter, bipolar recordings were obtained from the tricuspid annulus, coronary sinus, interatrial septum and left atrium. AAF was defined by the absence of concealed entrainment from the inferior vena cava--tricuspid annulus isthmus. Target sites were identified by early, fragmented or double potentials and by concealed entrainment. Linear lesions were created between target sites and nearby anatomical barriers in a temperature-controlled mode: 20 episodes of AAFs were documented in 19/90 (21%) patients. Mitral valve disease and surgery were significantly more frequent in patients with AAF. Target sites were identified in the right atrial free wall (n=8), interatrial septum (n=6), left atrium (n=4) and coronary sinus (n=2). Effective ablation was obtained in 15/19 patients (79%). After a 15.7 +/- 10.7 month follow-up, AAF recurred in 0/15 patients with a successful and 3/4 (75%) with a failed procedure (P<0.05). CONCLUSIONS: Conventional mapping techniques enable identification of critical sites of AAF and allow successful ablation in the majority of cases.

Catheter ablation and antiarrhythmic drugs for haemodynamically tolerated post-infarction ventricular tachycardia; long-term outcome in relation to acute electrophysiological findings.

AIMS: Radiofrequency catheter ablation is effective at terminating ventricular tachycardia, but the overall clinical role of the technique in patients with a prior myocardial infarction is still debated, due to the uncertainties of the long-term reliability of the procedure. The purpose of this study was to prospectively investigate the relationship between acute results obtained by catheter ablation and long-term outcome in a homogeneous population of patients with post-myocardial infarction ventricular tachycardia. METHODS AND RESULTS: One hundred and twenty-four consecutive patients with recurrent, drug-refractory, haemodynamically tolerated ventricular tachycardia were included in the study. This population accounted for 30% of the patients with post-myocardial infarction ventricular tachycardia admitted between April 1992 and September 1997 to the investigating centres. The ablation was successful in eliminating sustained ventricular tachycardia in 91 of them (73%); a partial result was obtained in 21 (17%) and failure in 12 (10%). Low dose amiodarone and/or beta-blockers were maintained in 86% of the patients. Over a median follow-up of 41.5 months (interquartile range 30.5-59.5 months), there were 15 deaths (12%), three of which were sudden (2.4%); the 12 remaining patients died of heart failure. Event-free survival analysis showed a significantly lower ventricular tachycardia recurrence rate in patients with a successful procedure as compared to those with failure or a partial result (19% vs 53% at one year and 27% vs 60% at 3 years, P=0.003). A repeat procedure was performed in 15 patients with early recurrences and was followed in all by long-term success. Of those who submitted to a second procedure, 93/124 patients (75%) are free of ventricular tachycardia recurrences. An implantable cardioverter-defibrillator (ICD), following procedure failure, was implanted in 13 patients (11%) of the study population. CONCLUSIONS: Radiofrequency catheter ablation is effective in a wide population of patients with recurrent tolerated ventricular tachycardia, with very low sudden death and cardiac mortality rates over the long-term. Persistent ventricular tachycardia inducibility after catheter ablation requires an ICD implant and/or repeat ablation.

Electrophysiological characteristics and outcome in patients with idiopathic right ventricular arrhythmia compared with arrhythmogenic right ventricular dysplasia.

BACKGROUND: Idiopathic right ventricular arrhythmias (IRVA) are responsive to medical and ablative treatment and have a benign prognosis. Arrhythmias caused by right ventricular dysplasia (ARVD) are refractory to treatment and may cause sudden death. It is difficult to distinguish between these two types of arrhythmia. OBJECTIVE: To differentiate patients with IRVA and ARVD by a conventional electrophysiological study. METHODS: 56 patients with a right ventricular arrhythmia were studied. They had no history or signs of any cardiac disease other than right ventricular dysplasia. They were classified as having IRVA (n = 41) or ARVD (n = 15) on the basis of family history, ECG characteristics, and various imaging techniques. They were further investigated by standard diagnostic electrophysiology. RESULTS: The two groups were clearly distinguished by the electrophysiological study in the following ways: inducibility of ventricular tachycardia by programmed electrical stimulation with ventricular extrastimuli (IRVA 3% v ARVD 93%, p < 0.0001); presence of more than one ECG morphology during tachycardia (IRVA 0% v ARVD 73%, p < 0.0001); and fragmented diastolic potentials during ventricular arrhythmia (IRVA 0% v ARVD 93%, p < 0.0001). Data from the clinical follow up in these patients supported the diagnosis derived from the electrophysiological study. CONCLUSIONS: Patients with IRVA or ARVD can be distinguished by specific electrophysiological criteria. A diagnosis of ARVD can be made reliably on the basis of clinical presentation, imaging techniques, and an electrophysiological study.

Indications for dual-chamber cardioverter defibrillators at implant and at 1 year follow-up: a retrospective analysis in the single-chamber defibrillator era.

AIM: This retrospective four-centre study assessed the current indications for dual-chamber implantable cardioverter defibrillators (ICDs) at implant and during a medium-term follow-up period in a group of patients treated by single-chamber ICD in the pre dual-chamber ICD era. METHODS AND RESULTS: The study population consisted of 153 consecutive patients (127 males, mean age 58 +/- 6 years) treated by single-chamber ICD for ventricular tachycardia and/or ventricular fibrillation. Definite indications for having a dual-chamber ICD included the presence of sinus node dysfunction and of second- or third-degree atrioventricular (AV) block, while possible indications were represented by paroxysmal atrial fibrillation or flutter and first-degree AV block. At implant, dual-chamber ICD would appear definitely indicated in 10.5% of cases, and possibly indicated in an additional 17.5% of cases. During 12 +/- 10 months follow-up, such percentages remained stable (11 and 19.5%, respectively). Inappropriate ICD intervention was documented in five of 13 patients (38%), with episodes of paroxysmal atrial fibrillation or flutter. CONCLUSION: In this non-selected study population, a dual-chamber ICD would have potentially benefited approximately 30% of the patients. During medium-term follow-up, there was no progression towards increasing dual-chamber ICD indications. The 15% cumulative incidence of paroxysmal atrial tachyarrhythmias justifies the activation of dedicated detection algorithms.

Spatial and temporal heterogeneity of depolarization and repolarization may complicate implantable cardioverter defibrillator therapy in Brugada syndrome.

INTRODUCTION: Dynamic variations in electrophysiologic phenomena inherent to the Brugada syndrome may complicate therapy with implantable cardioverter defibrillators (ICDs). METHODS AND RESULTS: Between 1997 and 1999, 3 of 7 patients with Brugada syndrome (1 man and 2 women, mean age 42 years) received an ICD. During follow-up, 2 patients experienced multiple inappropriate shocks. Simultaneously with dynamic changes in the surface ECG, endocardial ECGs revealed a dynamic decrease in the right ventricular R wave and an increase in the corresponding T wave, resulting in T wave oversensing. With ajmaline administration, these dynamic changes in endocardial signals were reproducible at different right ventricular sites, whereas left ventricular epicardial signals remained stable. Incremental AAI pacing and exercise stress testing resulted in similar changes in right ventricular endocardial signals, but normalization of the surface ECG apart from progressively increasing S waves in leads II, V5, and V6. Orciprenaline administration had no effect on ECG phenomena. After implantation of a left ventricular epicardial lead for sensing and pacing, no inappropriate tachycardia detection recurred. CONCLUSION: These findings demonstrate that, in Brugada syndrome, spontaneous or ajmaline-induced changes in the surface ECG may be paralleled by significant variations in the right ventricular endocardial electrogram that may result in ICD malfunction. Implantation of a left ventricular epicardial lead for sensing and pacing may be the ultimate successful approach in certain patients. To assure proper ICD function, ajmaline testing during ICD implantation appears to be helpful.

Radiofrequency ablation of atrioventricular junction and pacemaker implantation versus modulation of atrioventricular conduction in drug refractory atrial fibrillation.

Modulation of atrioventricular (AV) node conduction and radiofrequency ablation of AV junction are alternative approaches to control ventricular rate in drug refractory atrial fibrillation (AF). In 2 centers, 120 patients were treated either with AV junction ablation (center 1, group 1, 60 patients [30 men, aged 64 +/- 11 years], paroxysmal AF in 24 patients) or with modulation (group 2, 60 patients [32 men, aged 58 +/- 12 years], paroxysmal AF in 43 patients). In group 1, complete AV block was achieved in all patients. In group 2, the procedure was performed in sinus rhythm (30 patients), prolonging the Wenckebach cycle length from 328 +/- 85 to 466 +/- 80 ms (p <0.01) or during AF (30 patients), decreasing ventricular rate from 178 +/- 35 to 96 +/- 35 beats/min (p <0.01), and to <100 beats/min in 17 patients (61%). Complete AV block was induced in 9 of 60 patients (15%). In groups 1 and 2, at a follow-up of 27 +/- 7 and 26 +/- 6 months, there were 2 deaths (1 cardiac, 1 sudden death) and 1 death for end-stage heart failure, respectively. Hospital readmissions decreased from 3.2 to 0.2 and from 4.2 to 0.2/year; late AF recurrences at of >120 beats/min were documented in 6% and 12%, respectively. Symptom score analysis including effort and rest dyspnea, exercise intolerance, weakness, and palpitation showed a significant improvement in both treatment groups, when acutely effective, in patients with paroxysmal and/or chronic AF. In conclusion, ablation of the AV junction shows a higher acute success rate compared with modulation of the AV node conduction in patients with drug refractory AF. Depending on the acute success, both approaches therefore were similarly effective in achieving long-term ventricular rate control and symptom score improvement.

Modulation of the atrioventricular node conduction to achieve rate control in patients with atrial fibrillation: long-term results.

Modulation of the AV node reduces the ventricular rate during AF, without affecting AV conduction during sinus rhythm. Acute and long-term results of AV node modulation in 75 patients with AF and severe related symptoms of heart failure are presented in this study. The procedure involved, in all cases, the selective ablation of the posterior inputs to the AV node; in a subgroup of 15 patients with poor modification of AV conduction properties, a sequential approach involving subsequent anterior input ablation was performed. The procedure caused acutely a prolongation of the Wenckebach cycle length (38 patients in sinus rhythm) from 334 +/- 88 to 470 +/- 80 ms (P < 0.01), and a reduction of the average ventricular rate (37 patients in AF) from 154 +/- 31 to 88 +/- 40 beats/min (P < 0.01); permanent complete AV block was induced in 9 of 75 patients (12%). Considering the "sequential" approach, an increase of the Wenckebach cycle length from 362 +/- 50 to 530 +/- 45 ms (P < 0.01) and a reduction of the average heart rate in patients with AF from 158 +/- 16 to 81 +/- 20 beats/min (P < 0.01) was obtained in this subgroup of patients, in whom the AH interval prolonged from 93 +/- 12 to 175 +/- 27 ms, and no complete AV block was observed. At a mean follow-up of 23 +/- 9 months (range 2-48), the mean number of hospital admissions per patient per year decreased from 4.2 to 0.2. Five of 49 patients with paroxysmal AF and 3 of 26 patients with chronic AF had high rate recurrences (1 > 120 beats/min) that caused severe palpitations; these patients were considered as late clinical failures (8/75; 11%). All patients reported a substantial subjective improvement and an increased exercise tolerance, as documented by a semiquantitative questionnaire. There were no episodes of late AV block or sudden cardiac deaths. In conclusion, modulation of the AV node--either by slow pathway ablation, or by a "sequential" posterior and anterior approach in refractory patients--allows a long-term control of the ventricular rate and prevents the recurrence of severe clinical symptoms in more than 75% of patients with drug refractory AF.

Incidence and clinical significance of transformation of atrial fibrillation to atrial flutter in patients undergoing long-term antiarrhythmic drug treatment.

AIMS: To investigate the rate of transformation of atrial fibrillation to atrial flutter in patients taking antiarrhythmic drugs for the prophylaxis of atrial fibrillation, we retrospectively analysed data from 305 consecutive patients with paroxysmal atrial fibrillation (155 male; mean age 63 +/- 11 years) treated with ventricular rate controlling drugs, antiarrhythmic drugs, or without drugs. METHODS AND RESULTS: At a mean follow-up of 9 months (range 1-24) all patients experienced recurrence of arrhythmia: 48 (14.6%, Group A) suffered Type 1 atrial flutter, and 257 (85.4%, Group B) atrial fibrillation. The relative rate of recurrence of atrial flutter vs atrial fibrillation was similar in patients without treatment or with ventricular rate controlling drugs (from 6.8% to 14.6%, P=ns). However, recurrence was higher (25%) in patients administered antiarrhythmic drug therapy. The relative risk in these patients was 3.02 times greater, compared with patients without treatment, or treated with rate controlling drugs (P<0.001). There were no differences between groups concerning the baseline clinical characteristics and the clinical consequences of the recurrence; patients with atrial flutter had a lower rate of conversion to sinus rhythm (42% vs 64%) and a higher rate of hospital admission (69% vs 36%) compared with those with atrial fibrillation. Six patients (8.5%) experienced 1:1 atrioventricular conduction during atrial flutter with a ventricular rate of 240-280 beats x min(-1). CONCLUSION: Our data suggest that the use of antiarrhythmic drugs for the prophylaxis of atrial fibrillation is associated with a threefold increase in the probability of Type 1 atrial flutter recurrence, as opposed to atrial fibrillation, which may have important clinical consequences, but which did not in our study.

[Improvement of accessory pathways radiofrequency catheter ablation by arterial or venous epicardial mapping]. / Migliore successo dell'ablazione transcatetere di vie accessorie a difficile localizzazione grazie al mappaggio epicardico arterioso o venoso.

Failure of radiofrequency catheter ablation for atrioventricular reciprocating tachycardia may be related to imprecise location of accessory pathways. We have tested the safety and efficacy in improving successful rate of the procedure of a new technique of epicardial mapping of the atrioventricular sulcus by means of a small diameter (2.5F) 16 polar electrode catheter with a soft tip and a minor interelectrode and intercouple distance (2-6-2). The catheter was advanced via a right femoral approach into the coronary sinus or its branches, and the right coronary artery. We report 5 patients who underwent epicardial mapping-guided radiofrequency catheter ablation who had been previously treated with 1 or more (range 1-4) unsuccessful traditional mapping of the atrioventricular sulcus. Epicardial mapping was performed by means of selective catheterization of the coronary sinus in 4 cases, and of the right coronary artery in 1. The accessory pathways was precisely localized and ablated in all patients (mean 8 +/- 1.5 radiofrequency pulses, and 32 +/- 6 min fluoroscopy duration). No procedure or catheterization-related complications were observed. In conclusion, the technique of epicardial mapping used in this study proved to be safe and effective in localizing accessory pathways in selected cases, thereby enhancing radiofrequency catheter ablation success rate. The main advantage of this atraumatic catheter as compared to the traditional ones are the femoral approach and the possibility to advance the catheter to the most anterior aspect of the great cardiac vein. The epicardial mapping is thus a feasible alternative to traditional mapping, particularly in cases in which previous procedures have failed due to a complex arrhythmogenic substrate and or congenital abnormalities.

[Analysis of changes in repolarization for the differential diagnosis of narrow QRS supraventricular tachycardia and the site of the accessory pathway]. / Analisi delle alterazioni della ripolarizzazione per la diagnosi differenziale delle tachicardie sopraventricolari a QRS stretto e della sede della via accessoria.

In view of the growing role of catheter ablation techniques for the treatment of supraventricular tachycardia, noninvasive determination of tachycardia mechanism and preliminary localization of the accessory pathway (AP) can simplify the cardiac catheterization procedure and reduce fluoroscopic exposure. The purpose of this study was to analyze the diagnostic value of repolarization changes during narrow QRS complex tachycardia (< 0.11 s). In 159 12-lead electrocardiograms during narrow QRS complex tachycardia (13 atrial tachycardias, 57 atrioventricular (AV) node reentrant tachycardias and 89 AV reciprocating tachycardias), the following were evaluated: 1) the tachycardia cycle length; 2) the presence of QRS alternans > or = 1 mm in at least 6 leads; 3) the presence of ST segment depression > or = 2 mm and/or T wave changes (inversion, notching); 4) the duration of retrograde atrial activation during tachycardia (right atrium-coronary sinus interval, in ms); the latter parameter, as well as tachycardia mechanism and accessory pathway location, were determined during an electrophysiologic study. There were no significant differences in mean cycle length among the groups. ST segment depression > or = 2 mm and/or T wave changes were present more often in AV reciprocating tachycardias (51/89) than in the other groups (AV node reentrant tachycardias: 14/57; atrial tachycardias: 1/13; p < 0.001), independently from the cycle length. Distinct patterns of repolarization changes during tachycardia were associated with different location of accessory pathway: ST segment depression from V3 to V6 in left lateral AP; T wave inversion in inferior leads in posterior-posteroseptal AP; T wave changes in V2 in all cases of anteroseptal AP location. The magnitude of ST segment depression, significantly more marked in the AV reciprocating tachycardias (1.3 +/- 1.6 mm) than in AV node reentrant tachycardias (0.7 +/- 0.8 mm, p < 0.005), was directly related to the duration of atrial activation time during tachycardia (80 +/- 20 ms, and 32 +/- 12 ms, p < 0.001, respectively). The finding of ST segment depression and/or T wave changes during narrow QRS tachycardia suggest the presence of an AV reciprocating tachycardia; this phenomenon may be related to a different pattern of retrograde atrial activation. In conclusion, analysis of repolarization changes during narrow QRS tachycardia constitutes an additional electrocardiographic criterion to differentiate the tachycardia mechanism and, furthermore, can guide preliminary location of the AP, even in the absence of ventricular preexcitation.

Persistence of single echo beat inducibility after selective ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia: relationship to the functional properties of the atrioventricular node and clinical implications.

INTRODUCTION: Residual slow pathway conduction with or without reentrant echo beats has been reported in 25% to 30% of patients undergoing ablation for AV nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS: Fifty-eight consecutive patients (aged 45 +/- 12 years) with slow-fast AVNRT underwent radiofrequency catheter ablation of the slow AV nodal pathway (SP). Residual slow-fast echo beat was documented in 21 (36%) of 58 patients (group A). The pre- and postablation AH intervals triggering the echo beats were similar (346 +/- 8 msec vs 352 +/- 6 msec, P = NS), as were the pre- and postablation echo zones (55 +/- 6 msec vs 52 +/- 5 msec, P = NS) and functional refractory period of the SP. A consistent prolongation of the AV nodal effective refractory period (AVN-ERP; from 265 +/- 28 msec to 340 +/- 50 msec, P < 0.001) and the Wenckebach cycle length (WBCL; from 298 +/- 41 msec to 438 +/- 43 msec, P < 0.001) was observed in all patients with abolition of SP conduction (group B). In group A patients, the prolongation of WBCL was less (285 +/- 33 msec preablation, and 334 +/- 41 msec postablation, P < 0.001). Additional pulses abolished the residual echo in 16 of 21 patients, and further prolongation of the AVN-ERP and WBCL comparable to those found in patients without a residual echo beat was observed. During 19 +/- 8 months follow-up, no patient had clinical recurrence of AVNRT. CONCLUSION: Residual single echo beat after SP ablation for AVNRT reflects the persistence of some portion of the SP with unchanged functional conduction properties whose prognostic significance is uncertain. A consistent increase of WBCL can be a reliable marker of complete abolition of slow pathway conduction and termination of AVNRT.

Value of analysis of ST segment changes during tachycardia in determining type of narrow QRS complex tachycardia.

OBJECTIVES: Repolarization changes during narrow QRS complex tachycardia were analyzed to differentiate the tachycardia mechanism and to guide the preliminary location of the accessory pathway. BACKGROUND: Noninvasive determination of the mechanism of tachycardia is becoming increasingly important in view of the role of catheter ablation techniques for the cure of supraventricular tachycardia. METHODS: We analyzed 159 12-lead electrocardiograms during narrow QRS complex tachycardia to evaluate 1) the tachycardia cycle; and 2) ST segment depression or T wave inversion, or both. Each patient underwent a complete electrophysiologic evaluation. RESULTS: There were 13 atrial tachycardias, 57 atrioventricular (AV) node reentrant tachycardias and 89 AV reciprocating tachycardias. The mean RR cycle did not differ among types of tachycardia. ST segment depression >2 mm or T wave inversion, or both, was present more often in AV reciprocating tachycardia (57%) than in AV node tachycardia (25%). The magnitude of ST segment depression was greater in AV reciprocating tachycardia than in AV node tachycardia (mean +/- SD 1.3 +/- 1.6 vs. 0.7 +/- 0.8 mm, p < 0.005). In AV reciprocating tachycardia distinct patterns of repolarization changes and P wave configuration were associated with different sites of the accessory pathway. CONCLUSIONS: The presence of ST segment depression >2 mm or T wave inversion, or both, during narrow QRS complex tachycardia suggests that AV reentry using an accessory pathway is the mechanism of the tachycardia. The phenomenon may be the consequence of a distinct pattern of retrograde atrial activation. Analysis of repolarization changes can guide preliminary localization of the accessory pathway even in the absence of ventricular preexcitation.

[Modulation of atrioventricular conduction in patients with atrial fibrillation or flutter. Immediate and long-term results]. / Modulazione del nodo atrioventricolare in pazienti con fibrillazione e flutter atriale: risultati acuti e follow-up a lungo termine.

The modulation of atrioventricular (AV) conduction by radiofrequency catheter ablation of the "slow" AV node pathway reduces the ventricular rate during atrial flutter (AFL) or fibrillation (AF), without affecting AV conduction during sinus rhythm. In this study the acute and long-term effects of AV node modulation in 41 patients with AFL-AF are presented. The arrhythmia was paroxysmal in 34 and chronic in 7 patients, and was responsible in all patients for severe symptoms of heart failure. The procedure was performed during sinus rhythm in 23, AFL in 8, AF in 10 patients, and caused respectively an increase in Wenckebach cycle from 330 +/- 64 to 452 +/- 91 ms (p < 0.001), and a reduction in ventricular rate from 182 +/- 53 to 95 +/- 40 b/min (p < 0.001) and from 170 +/- 40 to 90 +/- 27 b/min (p < 0.001). The arbitrary endpoint of the procedure (Wenckebach cycle > 500 ms during sinus rhythm, maximum heart rate < 100 b/min during AFL-AF) was achieved in 19/41 patients; permanent complete AV block was induced in 6 "non-responder" patients (15%). At a mean follow-up of 15 +/- 7 months (range 1-31) all patients reported a substantial subjective improvement and a better exercise tolerance--as documented by a quantitative questionnaire concerning quality of life--without any recurrence of acute pulmonary edema, syncope or severe hypotension. In 5 patients during paroxysmal AFL-AF, and in 1 patient with chronic AF, a heart rate higher than 120 b/min was documented, and in 3 cases it was associated with severe palpitations. No late AV block occurred. The mean number of hospital-emergency room admissions per patient per year decreased from 3.9 before to 0.2 after the modulation. Considering complete AV block (6 patients, 15%) and clinical failures (6 patients, 15%), the success of the procedure was 70%, and was independent of the rhythm at the time of the procedure; the percentage of AV block was nevertheless higher during AFL-AF (22 vs 9%). Both endpoints of the procedure (Wenckebach cycle > 500 ms; heart rate < 100 b/min) were confirmed to be good predictors of long-term efficacy; on the other hand, a Wenckebach cycle < 430 ms was demonstrated to represent a specific marker of late failure. In conclusion, the study confirms that modulation of AV conduction is feasible in 70% of patients with AFL-AF: in these patients the procedure allows the long-term control of ventricular rate and a substantial improvement in quality of life, avoiding the need for His ablation and pacemaker implantation. "Non-responder" patients can be acutely identified and should be therefore considered condidates for His ablation during the same session.

Modulation of atrioventricular conduction by ablation of the "slow" atrioventricular node pathway in patients with drug-refractory atrial fibrillation or flutter.

OBJECTIVES: We hypothesized that modulation of atrioventricular (AV) node conduction, allowing a reduction in ventricular rate during atrial fibrillation or flutter without affecting AV conduction during sinus rhythm, might be achieved through ablation of the "slow" AV node pathway. BACKGROUND: In patients with atrial fibrillation or flutter not amenable to a direct atrial approach, ablation of the His bundle is performed to induce complete AV block. This procedure causes pacemaker dependence. METHODS: Fourteen patients with drug-refractory paroxysmal atrial flutter or fibrillation underwent ablation of the slow AV node pathway. Radiofrequency current was delivered in six patients during sinus rhythm, in six during atrial flutter and in two during atrial fibrillation. RESULTS: The anterograde effective refractory period of the AV node was prolonged from 270 +/- 50 (mean +/- SD) to 390 +/- 87 ms (p = 0.005) and the Wenckebach cycle from 346 +/- 33 to 458 +/- 75 ms (p = 0.004) in six patients during sinus rhythm. Mean AV ratio increased from 1.6 +/- 0.5 to 3.0 +/- 0.6 (p = 0.02) in six patients with atrial flutter. Mean ventricular rate decreased from 157 +/- 38 to 67 +/- 10 beats/min in two patients with atrial fibrillation. Complete AV block was induced in two patients (transient in one, permanent in one). During a follow-up period of 5.8 +/- 3.5 months, 11 patients experienced a recurrence of atrial fibrillation at 60 to 95 beats/min. No patient had progression to any degree of AV block. CONCLUSIONS: Ablation of the slow AV node pathway allows reduction of ventricular rate during atrial fibrillation or flutter while maintaining intact AV conduction during sinus rhythm. Modulation of AV node conduction is effective in most patients as an alternative to His bundle ablation for control of ventricular rate in paroxysmal atrial fibrillation or flutter.