Radiofrequency catheter ablation in patients with symptomatic atrial flutter/tachycardia after

Background  Atrial tachycardia or flutter is common in patients after orthotopic heart transplantation. Radiofrequency catheter ablation to treat this arrhythmia has not been well defined in this setting. This study was conducted to assess the incidence of various symptomatic atrial arrhythmias and the efficacy and safety of radiofrequency catheter ablation in these patients.
Methods  Electrophysiological study and catheter ablation were performed in patients with symptomatic tachyarrhythmia. One Halo catheter with 20 poles was positioned around the tricuspid annulus of the donor right atrium, or positioned around the surgical anastomosis when it is necessary. Three quadripolar electrode catheters were inserted via the right or left femoral vein and positioned in the recipient atrium, the bundle of His position, the coronary sinus. Programmed atrial stimulation and burst pacing were performed to prove electrical conduction between the recipient and the donor atria and to induce atrial arrhythmias.
Results  Out of 55 consecutive heart transplantation patients, 6 males [(58±12) years] developed symptomatic tachycardias at a mean of (5±4) years after heart transplantation. Electrical propagation through the suture line between the recipient and the donor atrium was demonstrated during atrial flutter or during recipient atrium and donor atrium pacing in 2 patients. By mapping around the suture line, the earliest fragmented electrogram of donor atrium was assessed. This electrical connection was successfully ablated in the anterior lateral atrium in both patients.  There was no electrical propagation through the suture line in the other 4 patients. Two had typical atrial flutter in the donor atrium which was successfully ablated by completing a linear ablation between the tricuspid annulus and the inferior vena cava. Two patients had atrial tachycardia which was ablated in the anterior septal and lateral donor atrium. There were no procedure-related complications. Patients were free of recurrent atrial tachyarrhythmias after a follow-up of (8±7) months.
Conclusions  Four electrophysiological mechanisms have been found to contribute to the occurrence of symptomatic supraventricular arrhythmias following heart transplantation. Radiofrequency catheter ablation in patients with atrial flutter/tachycardia is feasible and safe after heart transplantation.

     

Rhythm or rate control in atrial fibrillation: insights from the randomized controlled trials

Pharmacologic treatment remains the mainstay of therapy in patients with atrial fibrillation for the maintenance of normal sinus rhythm. Initial therapy of atrial fibrillation is often directed toward the maintenance of sinus rhythm by means of cardioversion and the use of antiarrhythmic drugs. Heart rate control is often only pursued when rhythm control fails. Four randomized controlled trials have carefully evaluated the yield of these two treatment strategies as the initial approach to patients with paroxysmal or persistent atrial fibrillation. In essence, all four trials demonstrated that an initial strategy of rate control is equally effective compared to the rhythm control approach in terms of clinically important outcome measures including mortality, stroke prevention, or quality of life. Accordingly, rate control can be considered as an initial approach to therapy in patients with paroxysmal or persistent atrial fibrillation. The four randomized trials clearly demonstrate that continuous anticoagulation is mandatory in all patients with atrial fibrillation and risk factors for stroke, irrespective of the initial therapeutic approach of rhythm or rate control.     

Heart Rate Variability to Assess Changes in Cardiac Vagal Modulation Prior to the Onset of Paroxysmal Atrial Fibrillation in Patients With and Without Structural Heart Disease

Background and Objectives: In patients with paroxysmal lone AF, clinical data indicate a predominance of vagal modulation preceding attacks of the arryhthmia. Systematic data derived from time-domain analysis of HRV evaluating changes in autonomic modulation prior to AF onset are sparse, both in patients without and with evidence for structural heart disease. This study evaluated changes in autonomic modulation prior to the onset of AF in patients with and without structural heart disease. Methods and Results: In 26 consecutive patients with at least one episode of paroxysmal AF preceded by a period of sinus rhythm of at least 8 hours duration documented on Holter monitoring, the time-domain parameters SDNN, rMSSD, and pNN5O were analyzed at different time points between 8 hours and 10 minutes prior to the onset of AF. Fourteen patients had AF associated with structural heart disease, whereas 12 patients had paroxysmal lone AF. Analysis of HRV changes before onset of AF revealed significant differences between the two patient groups: In patients without heart disease, pNN5O and rMSSD increased from 10 ± 3 to 15 ± 4% (P=0.003) and from 38 ± 7 to 53 ± 9 ms (P=0.035). No significant change in HRV was observed in patients with structural heart disease (pNN5O 5 ± 3 vs. 6 ± 2 % and rMSSD 25 ± 4 vs. 28 ± 6 ms). Conclusions: In patients with lone AF, there is a significant shift of autonomic modulation towards a vagal predominance prior to the onset of paroxysmal AF as compared to patients with structural heart disease. Analysis of HRV prior to attacks of AF is useful in determining these triggering mechanisms.     

Heart failure complicated by atrial fibrillation: mechanistic,prognostic, and therapeutic implications

Atrial fibrillation and congestive heart failure are two distinct clinical entities that are responsible for significant morbidity and mortality in the Western world. Hypertension, coronary artery disease, and nonischemic cardiomyopathy represent the most prevalent underlying pathologies of both diseases, implying a coincidence of both in many patients. The prevalence of atrial fibrillation with a progressive degree of congestive heart failure is increasing, as judged by New York Heart Association functional class. Moreover, the presence of congestive heart failure has been identified as one of the most powerful independent predictors of atrial fibrillation, with a sixfold increase in relative risk of its development. On the other hand, atrial fibrillation can cause or significantly aggravate symptoms of congestive heart failure in previously asymptomatic or well-compensated patients. In some patients, symptomatic dilated cardiomyopathy may develop over time entirely due to atrial fibrillation with rapid ventricular rates. Upon restoration of sinus rhythm, this type of "tachymyopathy" has been shown to be often reversible. Recent investigations of the physiologic and structural changes of the atrial myocardium ("electrical and structural remodeling") have shown that neurohumoral activation, fibrosis, and apoptosis are demonstrable with both diseases. On the other hand, experimental data suggest that the substrates of atrial fibrillation in congestive heart failure are different from those of pure atrial tachycardia-related forms of atrial fibrillation. This review highlights the clinical and pathophysiologic similarities and differences of atrial fibrillation and congestive heart failure relevant to the understanding, treatment, and prevention of these diseases in the population at risk.     

Long-term risk of recurrent atrial fibrillation as documented by an implantable monitoring device: implications for optimal patient care

OBJECTIVES: The present study determined the incidence and time course of atrial fibrillation (AF) recurrences in patients with a history of AF and fitted with an implantable monitoring device. BACKGROUND: The long-term risk of undetected recurrence of AF in patients receiving stable antiarrhythmic therapy remains uncertain. METHODS: In 110 patients with a class I indication for physiologic pacing and a history of AF, a pacemaker with dedicated functions for AF detection and electrogram storage was implanted, and antiarrhythmic drug treatment was optimized. Patients were regularly followed up with evaluation of AF-related symptoms, a resting electrocardiogram (ECG), and interrogation of device memory. The incidence of AF recurrences lasting >48 h in asymptomatic patients presenting in sinus rhythm (SR) at the respective follow-up visit constituted the primary end point of this prospective study. RESULTS: During 19 +/- 11 months, 678 follow-up visits were performed. Atrial fibrillation was documented in 51 patients (46%) by ECG recording and in 97 patients (88%) by a review of stored electrograms (p < 0.0001). Device interrogation revealed AF recurrences lasting >48 h in 50 patients, 19 of whom (38%) were completely asymptomatic and in SR at subsequent follow-up. In 11 (16%) of 67 patients with device-confirmed freedom from AF for > or =3 months, AF lasting >48 h recurred subsequently. CONCLUSIONS: This prospective study demonstrates a high incidence of recurrent AF despite optimized antiarrhythmic therapy. Of particular note, AF relapses >48 h remained totally asymptomatic in a significant proportion of patients. Freedom from AF for > or =3 months did not preclude subsequent long-lasting AF recurrence.     

The quick-implantable-defibrillator trial.

AIMS: Earlier ICD therapy included an electrophysiological study (EPS), an extensive defibrillation threshold test (DFT), and a pre-discharge test. Now that ICD-therapy is widely accepted, an EPS is no longer performed in most patients, extensive DFT-tests have been reduced to a minimum of two effective shocks and discharge tests have been discarded in most centres. However, it has never been demonstrated prospectively that this simplification is safe. METHODS AND RESULTS: The Quick-Implantable-Defibrillator (Quick-ICD) Trial was a prospective multi-centre trial, which randomized patients, who had survived a cardiac arrest (SCD) or an unstable ventricular tachycardia (VT), to two different clinical strategies: (a) The extensive strategy included an EPS, an extensive DFT-test, and a pre-discharge test; (b) In the simplified approach (quick strategy) the ICD was implanted without an EPS and a pre-discharge test. Two effective shocks during implantation at 21 J were sufficient. The primary endpoint of this trial was a cluster of adverse events related to the diagnostic approach and to ICD-therapy. One hundred and ninety patients were included, 97 randomized to the extensive-, 93 to the quick strategy. Mean follow-up was 12 +/- 7 months. Twenty-seven patients reached the endpoint in the quick group and 32 in the extensive group. During follow-up, the event-free survival was equal in the two study arms (test for equivalence, P = 0.0044). The initial hospital stay was significantly shorter in the quick population (8.4 +/- 4.7 vs. 11.2 +/- 7.4 days, P = 0.004) CONCLUSION: It is safe and cost-effective to implant an ICD without an EPS, an extensive DFT-, and a pre-discharge test in carefully selected patients after survived SCD or unstable VTs.     

The Defibrillator in Acute Myocardial Infarction Trial (DINAMIT): Rationale, Design and Specific Aims

The implantable defibrillator (ICD) effectively palliates arrhythmogenic events and thereby reduces total mortality in patients after a first episode of cardiac arrest. At present, four randomized controlled trials have addressed the issue of primary prevention by the ICD in patients with coronary artery disease and two small studies are available dealing with patients suffering from nonischemic cardiomyopathy. Importantly, none of the randomized studies in patients suffering from coronary artery disease has examined the potential role of the ICD in patients early after myocardial infarction. Within the next 12 months, important additional data is expected from several studies which have completed patient enrollment and follow-up. All studies are prospective randomized trials investigating the effects of ICD compared to optimal medical therapy. This paper summarizes the rationale, design and specific contributions of the Defibrillator in Myocardial infarction trial (DINAMIT) in comparison to other relevant studies on primary prevention of sudden cardiac death.     

Stepwise approach to substrate modification of ventricular tachycardia after myocardial infarction

Background Recently, substrate mapping (SM) has been described to facilitate catheter ablation of stable and unstable ventricular tachycardia (VT) after myocardial infarction. However, SM is time consuming with potential disadvantages of multiple ablation lines such as impairment of ventricular function or proarrhythmia. The aim of the present study was to delineate a stepwise approach to SM to shorten procedure time and limit the possibility of complications. Methods SM was performed in 14 infarct survivors referred for VT ablation using an electroanatomical mapping system (CARTO) to define infarct regions. A new stepwise approach for SM was designed as follows. The initial ablation site was identified by pace- and entrainment mapping in case of stable VT and by pace mapping only in case of unstable VT. Based on the CARTO voltage mapping, linear ablation was done from this site to the center of the scar and perpendicular to the boundary of the scar or to the mitral annulus. Additional lines were performed only when VT remained inducible. A maximum of 3 ablation lines were created during one procedure. Results A total of 57 VTs (21 stable, 36 unstable) were induced during the procedures. VT was no longer inducible after the first linear ablation in 2 patients, after the second linear ablation in 6 patients and after the third linear ablation in 3 patients. Either VT or ventricular fibrillation was still inducible at the end of the procedure in 3 patients. Procedure time averaged (291 + 85) minutes, fluoroscopy time (10+7) minutes. VT recurred in 3 patients. Following a second procedure in 2 patients, there were no further VT recurrences. Overall, there was a significant reduction in VT episodes 3 months after [median: 0, interquartile ranges (IQR): 0-1] compared with 3 months before ablation (median: 25, IQR: 16-105, P<0.01). Conclusions This stepwise approach to SM is effective in facilitating ablation of stable and unstable VT. It reduces procedure and fluoroscopy time, and may help to improve the risk-benefit ratio of VT ablation.     

Bundle branch reentrant tachycardia in patients with apparent normal His-Purkinje conduction: the role of functional conduction impairment

INTRODUCTION: His-Purkinje conduction delay, manifested by bundle branch block QRS complex configuration or by HV interval prolongation, is considered an essential condition for maintenance of bundle branch reentrant tachycardia (BBRT). METHODS AND RESULTS: Of 178 patients with different types of ventricular tachycardia (VT), 13 were found to have BBRT as the underlying electrophysiologic mechanism. Of these 13 patients (9 men and 4 women; mean age 64 +/- 13 years), 6 had an HV interval < or = 55 msec (group A), and 7 had a prolonged HV interval (> 55 msec; group B) during sinus rhythm (SR). PR interval (169 +/- 32 vs 339 +/- 138 msec, P = 0.01) and QRS duration (116 +/- 17 vs 167 +/- 29 msec, P = 0.003) during SR were significantly shorter in group A than in group B. In group A, the HV interval was significantly longer during VT than during SR (73 +/- 18 vs 47 +/- 7 msec, P = 0.007). There were more patients with functional His-Purkinje block (split His potentials, a jump of HV interval induced by programmed atrial stimulation or burst pacing) or phase 3 block in group A than group B (6/6 patients vs 0/7 patients, P < 0.001). Successful ablation of the right bundle branch was performed in all 13 patients without deteriorating AV block. Two patients died in each group, and VTs (other than BBRT) or ventricular fibrillation were documented by ICD electrogram storages in 4 patients during follow-up of 27 +/- 17 months. CONCLUSION: A prolonged HV interval during SR is not a prerequisite for BBRT. Functional His-Purkinje system abnormalities appear to be the electrophysiologic substrate for this specific type of BBRT.