Determinants of Time in Therapeutic Range in Patients Receiving Oral Anticoagulants (A Substudy of IMPACT).

Implanted cardiac arrhythmia devices can detect atrial tachyarrhythmias (atrial high-rate episodes [AHREs]) that are considered to correlate with atrial fibrillation and risk of stroke. In the IMPACT trial, oral anticoagulation was initiated when AHREs were detected by implanted cardioverter-defibrillators and withdrawn when they abated, according to a protocol accounting both for AHRE duration as detected by remote device monitoring and stroke risk assessment. In this analysis, we ascertained determinants of time in therapeutic range (TTR) among protocol-determined vitamin K antagonist-treated patients during the trial. We enrolled 2,718 patients with at least 1 additional stroke risk factor (CHADS2 score ≥1) at 104 arrhythmia centers. The sex, age <60, medical history, treatments interacting with VKA, tobacco use (2 points) and race (2 points for non-Caucasian) (SAMe-TT2R2) score is a simple clinical-derived score designed to aid decision-making on whether a patient is likely to achieve good anticoagulation control on vitamin K antagonist (e.g., warfarin), which was calculated and related to TTR achieved using the Rosendaal method. We analyzed 229 patients (mean age 66.7 years; mean CHADS2 score 2.85 [SD 1.1]) with mean TTR of 0.536 (SD 0.23) overall. Univariate analysis identified 5 variables associated with differences in mean TTR. Mean TTR was lower in those who were women (p = 0.031), of black race (p = 0.005) and in New York Heart Association class IV (p = 0.014), whereas hemoglobin >13.5 g/dl (p = 0.010) and New York Heart Association class I (p = 0.037) were associated with higher mean TTR. There was a significant difference in mean TTR value between US and non-US sites (Canada and Germany) (mean TTR for US: 0.513 vs non-US: 0.686; p <0.0001). Mean TTR was significantly lower (Δ = 0.1382, 95% CI 0.0382 to 0.2382) for patients with SAMe-TT2R2 scores of 4 (p = 0.007) and higher (Δ = 0.0612, 95% CI 0.0005 to 0.1219) for patients with SAMe-TT2R2 scores of 1 (p = 0.048). Linear regression confirmed a significant association between lower SAMe-TT2R2 score and improved anticoagulation control (p = 0.0021) with a 1-unit decrease in SAMe-TT2R2 score associated with an increase in TTR of 0.0404 (95% CI 0.0149 to 0.0659). In conclusion, clinical, geographical, and demographic factors were associated with the quality of anticoagulation control as reflected by TTR. Although overall TTR in this population was poor, lower SAMe-TT2R2 scores were associated with better TTR.

Randomized trial of atrial arrhythmia monitoring to guide anticoagulation in patients with implanted defibrillator and cardiac resynchronization devices.

AIMS: Atrial tachyarrhythmias (ATs) detected by implanted devices are often atrial fibrillation or flutter (AF) associated with stroke. We hypothesized that introduction and termination of anticoagulation based upon AT monitoring would reduce both stroke and bleeding. METHODS AND RESULTS: We randomized 2718 patients with dual-chamber and biventricular defibrillators to start and stop anticoagulation based on remote rhythm monitoring vs. usual office-based follow-up with anticoagulation determined by standard clinical criteria. The primary analysis compared the composite endpoint of stroke, systemic embolism, and major bleeding with the two strategies. The trial was stopped after 2 years median follow-up based on futility of finding a difference in primary endpoints between groups. A total of 945 patients (34.8%) developed AT, 264 meeting study anticoagulation criteria. Adjudicated atrial electrograms confirmed AF in 91%; median time to initiate anticoagulation was 3 vs. 54 days in the intervention and control groups, respectively (P < 0.001). Primary events (2.4 vs. 2.3 per 100 patient-years) did not differ between groups (HR 1.06; 95% CI 0.75-1.51; P = 0.732). Major bleeding occurred at 1.6 vs. 1.2 per 100 patient-years (HR 1.39; 95% CI 0.89-2.17; P = 0.145). In patients with AT, thromboembolism rates were 1.0 vs. 1.6 per 100 patient-years (relative risk -35.3%; 95% CI -70.8 to 35.3%; P = 0.251). Although AT burden was associated with thromboembolism, there was no temporal relationship between AT and stroke. CONCLUSION: In patients with implanted defibrillators, the strategy of early initiation and interruption of anticoagulation based on remotely detected AT did not prevent thromboembolism and bleeding. CLINICAL TRIAL REGISTRATION: IMPACT ClinicalTrials.gov identifier: NCT00559988 ( http://clinicaltrials.gov/ct2/show/NCT00559988?term=NCT00559988&rank=1 ).

Combining shock reduction strategies to enhance ICD therapy: a role for computer modeling.

OBJECTIVES: To develop a computer model to test shock reduction strategies such as antitachycardia pacing and shock withholding for supraventricular rhythms, oversensing, and nonsustained ventricular tachycardia. BACKGROUND: While the implantable cardioverter defibrillator (ICD) can reduce mortality, inappropriate ICD shocks remain a limitation. Randomized trials provide evidence of efficacy, but they are not always practical. Computer models provide an alternative approach, and are particularly useful when evaluating multiple interventions. METHODS: A computer model was developed using clinical data and validated in a large ICD data set (EMPIRIC). After validation, the model was applied to 736 adjudicated clinical episodes from the ICD arm of Sudden Cardiac Death Heart Failure Trial (SCD-HeFT). RESULTS: The shock reduction strategies hypothetically reduced the number of VT/VF shocked episodes in SCD-HeFT by an estimated 59% (from 952 observed to 395 modeled shocks, probability of >0.999) at detection duration settings (18 of 24 intervals). The percentage of patients experiencing inappropriate shocks over 5 years was decreased by 15% (23.5-8.4%), and the number of shocks for non-VT/VF episodes was decreased from 423 to 77 (82% reduction). The percentage of patients receiving shocks for VT/VF was reduced from 30.7% (SCD-HeFT) to 26.1% with the addition of ATP. Extended detection (24 of 32 or 30 of 40 intervals) showed modest additional improvement compared to 18 of 24 intervals. CONCLUSION: Computer modeling is able to predict the results of a known clinical trial and demonstrate that shock reduction strategies have the potential to significantly reduce inappropriate and unnecessary ICD shocks versus the mandated programming used in SCD-HeFT.

Differences in effects of electrical therapy type for ventricular arrhythmias on mortality in implantable cardioverter-defibrillator patients.

BACKGROUND: Implantable cardioverter-defibrillator (ICD) shocks have been associated with an increased risk of death. It is unknown whether this is due to the ventricular arrhythmia (VA) or shocks and whether antitachycardia pacing (ATP) termination can reduce this risk. OBJECTIVE: The purpose of this study was to determine whether mortality in ICD patients is influenced by the type of therapy (shocks of ATP) delivered. METHODS: Cox models evaluated effects of baseline characteristics, ventricular tachycardia (VT; <188 bpm), fast VT (FVT; 188-250 bpm), ventricular fibrillation (VF; >250 bpm), and therapy type (shocks or ATP) on mortality among 2135 patients in four trials of ATP to reduce shocks. RESULTS: Over 10.8 +/- 3.3 months, 24.3% patients received appropriate shocks (50.6%) or ATP only (49.4%), and 6.6% died. Mortality predictors were age (hazard ratio 1.07, 95% confidence interval 1.04-1.08, P <.0001), New York Heart Association class III/IV (3.50 [2.27-5.41]; P <.0001), coronary disease (3.08 [1.31-7.25]; P = .01), and cumulative VA (VT + FVT + VF) episodes shocked (1.20 [1.13, 1.29]; P <.0001). Beta-blockers (0.65, 0.46-0.92; P <.0001) and remote myocardial infarction (0.53, [0.38-0.76] P = .0004) predicted reduced risk. Since 92% of VT and all VF received a single therapy type (ATP and shocks, respectively), the effect of therapy on episode risk could not be established. For FVT (32% shocked, 68% ATP), episode and therapy effects could be uncoupled; ATP-terminated FVT did not increase episode mortality risk, whereas shocked FVT increased risk by 32%. Survival rates were highest among patients with no VA (93.8%) of ATP-only (94.7%) and lowest for shocked patients (88.4%). Monthly episode rates were 80% higher among shocked versus ATP-only patients. CONCLUSIONS: Shocked VA episodes are associated with increased mortality risk. Shocked patients have substantially higher VA episode burden and poorer survival compared with ATP-only-treated patients.

The relationship between pacing site and induction or termination of sustained monomorphic ventricular tachycardia by antitachycardia pacing.

BACKGROUND: With the development of left ventricular pacing for cardiac resynchronization, there is an interest in the possibility of improving ventricular antitachycardia pacing (ATP) efficacy by pacing from the LV electrode(s). OBJECTIVE: This study assessed the efficacy of pacing delivered from the left coronary vein (LCV) compared to that delivered from the right ventricular apex (RVA) upon ventricular tachycardia (VT) induction and termination. METHODS: Sixty patients undergoing provocative ventricular electrophysiology (EP) studies in three centers were enrolled. Multipolar EP catheters were placed in the atrium, the RVA, and LCV. VT induction was attempted from the RVA and LCV in random order. Upon detection of monomorphic VT, burst ATP for up to 10 pulses at 88% VT cycle length was delivered from the RVA or LCV, in a random order, and crossed over when possible. Identical VT morphologies were reinduced to allow paired comparison of RVA versus LCV ATP. RESULTS: Data from 55 patients were analyzed. Thirty-four morphologically distinct monomorphic VT types were induced in 22 patients. ATP succeeded in 18 (55%) and VTs in 13 patients. RVA ATP terminated 15 of 23 (65%) VTs, and LCV ATP terminated 10 of 23 (43%) VTs (P = 0.14). ATP delivered ipsilateral to the earliest activation site required 5.0 + or - 2.6 pulses to terminate compared to 4.8 + or - 1.7 pulses when delivered from the contralateral site (P = 0.90). Paired comparison was possible for 13 VT morphologies in 11 patients. Paired RVA and LCV ATP efficacy was identical (54%vs 54%, P = 1.0). CONCLUSION: ATP delivered from a LCV lead offers no efficacy advantage over pacing from the RVA.

Multicenter randomized study of anticoagulation guided by remote rhythm monitoring in patients with implantable cardioverter-defibrillator and CRT-D devices: Rationale, design, and clinical characteristics of the initially enrolled cohort The IMPACT study.

Atrial fibrillation and atrial flutter are common cardiac arrhythmias associated with an increased risk of stroke in patients with additional risk factors. Anticoagulation ameliorates stroke risk, but because these arrhythmias may occur intermittently without symptoms, initiation of prophylactic therapy is often delayed until electrocardiographic documentation is obtained. The IMPACT study is a multicenter, randomized trial of remote surveillance technology in patients with implanted dual-chamber cardiac resynchronization therapy defibrillator (CRT-D) devices designed to test the hypothesis that initiation and withdrawal of oral anticoagulant therapy guided by continuous ambulatory monitoring of the atrial electrogram improve clinical outcomes by reducing the combined rate of stroke, systemic embolism, and major bleeding compared with conventional clinical management. For those in the intervention group, early detection of atrial high-rate episodes (AHRE) generates an automatic alert to initiate anticoagulation based on patient-specific stroke risk stratification. Subsequently, freedom from AHRE for predefined periods prompts withdrawal of anticoagulation to avoid bleeding. Patients in the control arm are managed conventionally, the anticoagulation decision prompted by incidental detection of atrial fibrillation or atrial flutter during routine clinical follow-up. The results will help define the clinical utility of wireless remote cardiac rhythm surveillance and help establish the critical threshold of AHRE burden warranting anticoagulant therapy in patients at risk of stroke. In this report, we describe the study design and baseline demographic and clinical features of the initial cohort (227 patients).

Strategic programming of detection and therapy parameters in implantable cardioverter-defibrillators reduces shocks in primary prevention patients: results from the PREPARE (Primary Prevention Parameters Evaluation) study.

OBJECTIVES: Our purpose was to demonstrate that strategically chosen implantable cardioverter-defibrillator (ICD) ventricular tachycardia (VT) or ventricular fibrillation (VF) detection and therapy parameters can reduce the combined incidence of device-delivered shocks, arrhythmic syncope, and untreated sustained symptomatic VT/VF (morbidity index). BACKGROUND: Strategically chosen ICD VT/VF detection and therapy parameters have been shown in previous studies to reduce the number of shocked episodes. In the PREPARE (Primary Prevention Parameters Evaluation) study, these prior strategies were combined with additional strategies specific to primary prevention patients. METHODS: The PREPARE study was a prospective, cohort-controlled study that analyzed 700 patients (biventricular [Bi-V] ICD and non-Bi-V ICD) with primary prevention indications for an ICD from 38 centers followed for 1 year. VT/VF was detected for rates > or =182 beats/min that were maintained for at least 30 of 40 beats. Antitachycardia pacing was programmed as the first therapy for regular rhythms with rates of 182 to 250 beats/min, and supraventricular tachycardia discriminators were used for rhythms < or =200 beats/min. The control cohort consisted of 689 primary prevention patients from the EMPIRIC (Comparison of Empiric to Physician-Tailored Programming of Implantable Cardioverter Defibrillators Trial) (non-Bi-V ICD, physician arm only) and MIRACLE ICD (Multicenter InSync Implantable Cardioversion Defibrillation Randomized Clinical Evaluation) (Bi-V ICD) trials for whom VT/VF detection and therapy programming were not controlled. RESULTS: The PREPARE programming significantly reduced the morbidity index incidence density (0.26 events/patient-year for PREPARE study patients vs. 0.69 control cohort, p = 0.003). The PREPARE study patients were less likely to receive a shock in the first year compared with control patients (9% vs. 17%, p < 0.01). The incidence of untreated VT and arrhythmic syncope was similar between the PREPARE study patients and the control cohort. CONCLUSIONS: Strategically chosen VT/VF detection and therapy parameters can safely reduce shocks and other morbidities associated with ICD therapy in patients receiving an ICD for primary prevention indications. (PREPARE-Primary Prevention Parameters Evaluation; NCT00279279).

Implantable cardioverter defibrillator shock reduction using new antitachycardia pacing therapies.

The main purpose of ICDs is to abort sudden death by delivering therapy at the moment of tachycardia. Shocks accomplish this goal but are painful. Alternatively antitachycardia pacing is painless and if deemed safe may be reasonable substitute. Multiple trials show a high efficacy rate by ATP (78-94%) for treating VTs below 200 bpm. ATP has had less efficacy for faster VTs (41-79%) and have higher probability of accelerating tachycardia (5-55%). The PainFREE trials address these issues. The first pilot study PainFREE Rx applied standardized VT detection and ATP regimen to 220 patients with 1100 spontaneous episodes of VT. ATP success for slow VT success was 92% and fast VT > 188 bpm raw success rate was 89%. None of these trials randomize shock versus ATP so comparative safety data was missing. Thus, the PainFREE Rx II trial was designed to make direct safety comparison between shock and ATP therapies for fast VT > 188 bpm. It included 634 patients with either ischemic or nonischemic cardiomyopathy followed for 1 year yielding 1760 episodes of slow VT, fast VT plus VF. The results of the PainFREE Rx II trial showed that a single regimen of ATP, burst pace 8 pulses at 88% VT cycle length could safely terminate 77% of fast VT and 90% of slow VT. Consequently, shocks were reduced by 70% compared to the shock group. Furthermore, ATP was proven safe because there was no increase in sudden death, syncope or even arrhythmia acceleration compared to shock. The quality of life of the ATP group was found to be superior to the shock group validating ATP's intent. Secondary yet important findings also included the fact that by programming the ICD to wait for 18 beats in PainFREE Rx II before treating an episode reduced markedly the number of episodes treated when compared to 12 beat detection as done in PainFREE Rx I. Since syncope occurred in only 1% of episodes, the authors suggested that a longer wait for ICD detection needs to be evaluated.

Design of the Primary Prevention Parameters Evaluation (PREPARE) trial of implantable cardioverter defibrillators to reduce patient morbidity [NCT00279279].

BACKGROUND: Implantable Cardioverter Defibrillator (ICD) therapy has been proven to be beneficial and efficacious for the treatment of serious ventricular tachyarrhythmias in primary prevention patients. However, primary prevention patients appear to have a lower incidence of ventricular arrhythmias in comparison to secondary prevention patients and consequently likely experience a higher proportion of detections due to supraventricular arrhythmias. Recent trials have demonstrated that strategic and specific programming choices reduce the number of inappropriate shocks and that anti-tachycardia pacing (ATP) is an effective alternative to shock therapy for many sustained ventricular arrhythmias. METHODS: The Primary Prevention Parameters Evaluation (PREPARE) study is a multi-center cohort study, evaluating the efficacy of a pre-specified strategic profile of VT/VF detection and therapy settings in 700 primary prevention patients in an effort to safely reduce the number of shock therapies delivered. The patients, both with and without cardiac resynchronization therapy, are compared to a well-qualified set (n = 691) of historical controls derived from the MIRACLE ICD and EMPIRIC trials. This manuscript describes the design of the PREPARE study. The study results, to be presented separately, will characterize the efficacy of this programming set (PREPARE) compared with physician-tailored programming (MIRACLE ICD and EMPIRIC).

QRS duration does not predict occurrence of ventricular tachyarrhythmias in patients with implanted cardioverter-defibrillators.

OBJECTIVES: The aim of this study was to determine whether QRS duration (QRSd) correlates with occurrence of ventricular arrhythmia in patients with coronary disease (CAD) receiving implantable cardioverter-defibrillators (ICDs). BACKGROUND: A QRSd measured on a standard electrocardiograph (ECG) correlates with total mortality risk in CAD patients at high risk for sudden death; however, the relationship between QRSd and risk of ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]) is unclear. METHODS: PainFREE Rx II was a randomized trial, comparing efficacy of antitachycardia pacing versus shock therapy for VT/VF in patients receiving ICDs. We retrospectively correlated the QRSd and specific ECG conduction abnormalities on the 12-lead ECG at study entry with occurrence of VT/VF in 431 patients with CAD enrolled in the trial. RESULTS: The QRSd was < or =120 ms in 291 of 431 (68%) patients. Left bundle branch block (LBBB) was present in 65 patients, right bundle branch block (RBBB) in 48 patients, and nonspecific intraventricular conduction delay (IVCD) was present in 124 patients. Over 12 months' follow-up, VT/VF occurred in 95 (22%) patients (22% of patients with QRSd < or =120 ms vs. 23% of patients with QRSd >120 ms, p = NS). Patients with LBBB were less likely to experience at least one VT/VF episode than patients with QRSd <120 ms. Patients with RBBB and nonspecific IVCD did not differ from patients with narrow QRS complexes with regard to occurrence of tachycardias. CONCLUSIONS: The QRSd and ECG conduction abnormalities are not useful to predict ICD benefit in patients having the characteristics of our study population. The utility of QRSd to predict VT/VF events in patients with CAD requires further prospective evaluation.

Appropriate and inappropriate ventricular therapies, quality of life, and mortality among primary and secondary prevention implantable cardioverter defibrillator patients: results from the Pacing Fast VT REduces Shock ThErapies (PainFREE Rx II) trial.

BACKGROUND: Implantable cardioverter defibrillators (ICDs) reduce mortality in primary and secondary prevention. Quality of life, mortality, appropriate therapies for specific ventricular rhythms, and inappropriate therapies for supraventricular tachycardia (SVT) were compared among 582 patients (primary prevention=248; secondary prevention=334) in PainFREE Rx II, a 634-patient prospective, randomized study of antitachycardia pacing or shocks for fast ventricular tachycardia (FVT). METHODS AND RESULTS: ICDs were programmed identically with 3 zones (ventricular tachycardia [VT] <188 bpm; FVT=188 to 250 bpm; ventricular fibrillation [VF] >250 bpm) but randomized to antitachycardia pacing or shock as initial therapy for FVT. All treated episodes with electrograms were adjudicated. Primary prevention patients had lower ejection fractions and more coronary artery disease. beta-Blocker use, antiarrhythmic drug use, and follow-up duration were similar. Over 11+/-3 months, 1563 treated episodes were classified as VT (n=740), FVT (n=350), VF (n=77), and SVT (n=396). The distribution of VT, FVT, and VF was not different between primary and secondary prevention patients (respectively, VT 52% versus 54%, FVT 35% versus 35%, and VF 14% versus 10%). More secondary prevention patients had appropriate therapies (26% versus 18%, P=0.02), but among these patients, the median number of episodes per patient was similar. Inappropriate therapies occurred in 15% of both groups and accounted for similar proportions of all detected and treated episodes (46% in primary prevention patients versus 34% in secondary prevention patients, P=0.09). Quality of life improved modestly in both groups, and mortality was similar. CONCLUSIONS: Primary prevention patients are slightly less likely to have appropriate therapies than secondary prevention patients, but episode density is similar among patients with appropriate therapies. SVT resulted in more than one third of therapies in both groups, but quality of life and mortality were similar.

Prospective randomized multicenter trial of empirical antitachycardia pacing versus shocks for spontaneous rapid ventricular tachycardia in patients with implantable cardioverter-defibrillators: Pacing Fast Ventricular Tachycardia Reduces Shock Therapies (PainFREE Rx II) trial results.

BACKGROUND: Successful antitachycardia pacing (ATP) terminates ventricular tachycardia (VT) up to 250 bpm without the need for painful shocks in implantable cardioverter-defibrillator (ICD) patients. Fast VT (FVT) >200 bpm is often treated by shock because of safety concerns, however. This prospective, randomized, multicenter trial compares the safety and utility of empirical ATP with shocks for FVT in a broad ICD population. METHODS AND RESULTS: We randomized 634 ICD patients to 2 arms-standardized empirical ATP (n=313) or shock (n=321)-for initial therapy of spontaneous FVT. ICDs were programmed to detect FVT when 18 of 24 intervals were 188 to 250 bpm and 0 of the last 8 intervals were >250 bpm. Initial FVT therapy was ATP (8 pulses, 88% of FVT cycle length) or shock at 10 J above the defibrillation threshold. Syncope and arrhythmic symptoms were collected through patient diaries and interviews. In 11+/-3 months of follow-up, 431 episodes of FVT occurred in 98 patients, representing 32% of ventricular tachyarrhythmias and 76% of those that would be detected as ventricular fibrillation and shocked with traditional ICD programming. ATP was effective in 229 of 284 episodes in the ATP arm (81%, 72% adjusted). Acceleration, episode duration, syncope, and sudden death were similar between arms. Quality of life, measured with the SF-36, improved in patients with FVT in both arms but more so in the ATP arm. CONCLUSIONS: Compared with shocks, empirical ATP for FVT is highly effective, is equally safe, and improves quality of life. ATP may be the preferred FVT therapy in most ICD patients.

Incidence and characteristics of type-2 breaks in response to antitachycardia pacing therapy in implantable cardioverter defibrillator patients.

INTRODUCTION: Antitachycardia pacing (ATP) effectively treats monomorphic ventricular tachycardia (VT). The VT may cease immediately upon ATP completion (type-1 break), or it may persist or change to another tachyarrhythmia for one or more beats before termination (type-2 break). We investigated the prevalence and characteristics of type-2 breaks in ICD patients. METHODS AND RESULTS: We analyzed VT episodes with stored electrograms that had at least one ATP therapy delivered in PainFREE Rx trial, a multicenter trial with 220 coronary artery disease patients. Further subanalysis was performed by classifying the VT as slow or fast based on the cycle length (CL); slow VT: CL >320 ms, fast VT: 240 < or =CL < or =320 ms. To assess the effect of ATP on VT, comparison was performed of pre-ATP and post-ATP CL variability, average CL, and morphology. A total of 514 episodes (264 slow VT and 250 fast VT) were analyzed. The burst ATP terminated 457 (89%; 239 slow VT and 218 fast VT) of 514 episodes. Forty five (10%) episodes in 18 (32%) patients had type-2 breaks. The mean number of beats during type-2 breaks was 5.4 +/- 3.1 (median 4). The mean time for episode termination measured from the end of ATP to return of first sinus/paced beat was 2.9 +/- 1.2 seconds (median 2.6). The VT CL variability increased by 150% after ATP delivery. The ATP affected either VT CL or morphology, or both of 36 (80%) type-2 breaks (9% accelerated, 47% decelerated, 22% changed in morphology only). Among the 9 (20%) episodes that remained unchanged in morphology and CL, four episodes (9%) were unaffected by ATP. CONCLUSION: Approximately 10% of VT episodes that were successfully terminated with burst ATP therapy had type-2 breaks. Type-2 breaks are associated with an increase in CL variability. Approximately 9% of all type-2 episodes may be spontaneously terminating nonsustained VT given that ATP did not affect these episodes in any way.

Frequency of late recurrence of intra-atrial reentry tachycardia after radiofrequency catheter ablation in patients with congenital heart disease.

Forty-seven catheter ablation procedures for intra-atrial reentry tachycardia were performed in 40 patients with palliated congenital heart disease. The acute success rate was 87% and the recurrence rate was 34% during an average follow-up of 36 months. Of those patients who had recurrence, 88% did so within 1 year of ablation. Of the 23 patients who were free of recurrence 1 year after ablation, 21 (91%) remain free from recurrence at an average of 45 months (median 39; range 15 to 88) after ablation.