Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group.

BACKGROUND: The purpose of this study was to evaluate the safety and efficacy of a temperature-controlled radiofrequency catheter ablation system. METHODS AND RESULTS: The patient population included 1050 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia (AVNRT), an accessory pathway (AP), or the atrioventricular junction (AVJ). Ablation was successful in 996 patients. The probability of success was highest among patients who had undergone ablation of the AVJ, lowest in patients who had undergone ablation of an AP, and in between for patients who had undergone ablation of AVNRT. A major complication occurred in 32 patients. Four variables predicted ablation success (AVJ, AVNRT, or left free wall AP ablation and an experienced center). Four factors predicted arrhythmia recurrence (right free wall, posteroseptal, septal, and multiple APs). Two variables predicted development of a complication (structural heart disease and the presence of multiple targets), and 3 variables predicted an increased risk of death (heart disease, lower ejection fraction, and AVJ ablation). CONCLUSIONS: These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

Antitachycardia devices: realities and promises.

Nonpharmacologic therapy for ventricular arrhythmias has gained growing attention with the development of the implantable cardioverter-defibrillator. In addition, the reports of adverse effects of drug therapy from several studies, including the Cardiac Arrhythmia Suppression Trial (CAST), have supported the need for these devices. The development of new implantable cardioverter-defibrillators that have the capability of antitachycardia pacing, bradycardia pacing, cardioversion and defibrillation has enhanced their clinical utility. The currently available implantable cardioverter-defibrillators have been shown to significantly improve survival after sudden cardiac arrest in patients with life-threatening ventricular arrhythmias. Newer devices with expanded capabilities may reduce mortality even further. In this report the features of currently available antitachycardia devices and implantable cardioverter-defibrillators are reviewed and the features and current implant data on newer antitachycardia devices are discussed.

Radiofrequency ablation for atrioventricular node reentrant tachycardia: comparison between fast (anterior) and slow (posterior) pathway ablation.

OBJECTIVES: We compared the electrophysiologic effects on atrioventricular (AV) node physiology of selective "fast" versus selective "slow" pathway radiofrequency ablation in 42 patients with drug-resistant AV node reentrant tachycardia who underwent 51 ablation attempts to prevent tachycardia recurrence while preserving AV conduction. BACKGROUND: The recent introduction of radiofrequency ablation to treat AV node reentrant tachycardia allows the opportunity to study the effects of selective elimination of the different limbs involved in AV node reentrant tachycardia. METHODS: Selective fast pathway ablation was attempted in 13 patients by delivering radiofrequency energy anteriorly across the tricuspid valve anulus. Selective slow pathway ablation was attempted in 29 patients by delivering radiofrequency energy posteriorly across the tricuspid valve anulus at sites where putative slow pathway potentials were recorded. RESULTS: Selective fast pathway ablation eliminated AV node reentrant tachycardia without AV block in 6 (46%) of 13 patients after one ablation session and in an additional 3 patients (69% of total) after repeat ablation sessions. Slow pathway ablation eliminated AV node reentrant tachycardia without AV block in 26 (90%) of 29 patients after one radiofrequency ablation session and in an additional 2 patients (97% of total) after repeat ablation sessions. Selective fast pathway ablation increased the PR interval (140 to 220 ms, p = 0.0001) and AH interval (66 to 153 ms, p = 0.0001), whereas slow pathway ablation did not change these intervals. Fast pathway radiofrequency ablation caused retrograde block in 7 (64%) of 11 patients, whereas no patients undergoing slow pathway ablation developed selective retrograde block. Single AV node echo beats were commonly induced after slow but not fast pathway ablation (17 of 29 patients vs. 1 of 11 patients, respectively, p = 0.01) and did not predict recurrence of AV node reentrant tachycardia. CONCLUSIONS: Successful selective radiofrequency ablation of fast or slow pathways in patients with AV node reentrant tachycardia resulted in different electrophysiologic properties after ablation. Slow pathway ablation produced more successful outcomes, with a decreased prevalence of recurrent AV node reentrant tachycardia or AV block.

Regional cardiac sympathetic denervation in patients with ventricular tachycardia in the absence of coronary artery disease.

OBJECTIVES: The aim of this study was to determine whether patients with ventricular arrhythmias in the absence of coronary artery disease also have abnormalities in sympathetic innervation. BACKGROUND: We have previously shown by cardiac sympathetic scintigraphy using iodine-123-metaiodobenzylguanidine (I-123-MIBG) that patients with ventricular tachycardia after myocardial infarction have regional cardiac sympathetic denervation. It is not known whether patients with ventricular tachycardia in the absence of coronary artery disease also have regional cardiac sympathetic denervation. METHODS: We performed cardiac I-123-MIBG and thallium-201 single-photon emission computed tomographic (SPECT) scans at rest in 18 patients (mean age 47 +/- 18 years) with cardiomyopathy (n = 6), left ventricular hypertrophy (n = 1), valvular disease (n = 2) or a structurally normal heart (n = 9) who presented with monomorphic (n = 15) or polymorphic (n = 3) ventricular tachycardia. These scans were compared with scans in 12 control patients without ventricular tachycardia (mean age 30 +/- 17 years) who had cardiomyopathy (n = 3) or a structurally normal heart (n = 9). Cardiac sympathetic denervation was defined as myocardial areas having thallium uptake with reduced or absent I-123-MIBG uptake. RESULTS: Twelve (67%) of 18 patients with ventricular tachycardia had regional cardiac sympathetic denervation compared with 1 (8%) of 12 patients who did not have ventricular tachycardia (p = 0.002). In the nine patients with a structurally normal heart and ventricular tachycardia, five (55%) patients had regional cardiac sympathetic denervation compared with zero of nine control patients with a structurally normal heart (p = 0.029). Five patients underwent right ventricular radiofrequency ablation for ventricular tachycardia, and sympathetic denervation was adjacent to the ablation site in one of these patients. CONCLUSIONS: Patients with ventricular tachycardia in the absence of coronary artery disease have abnormal cardiac sympathetic innervation detectable by cardiac sympathetic scintigraphy. The role of regional cardiac sympathetic denervation in arrhythmogenesis remains to be determined.

Multiple accessory pathways in the permanent form of junctional reciprocating tachycardia.

The permanent form of junctional reciprocating tachycardia (PJRT) has been successfully eliminated by ablation of the accessory pathway responsible for the tachycardia. The coexistence of multiple accessory pathways responsible for different, long RP-interval tachycardias was not documented previously. Five patients with PJRT underwent radiofrequency catheter ablation of accessory pathways. Three of 5 patients had 2 accessory pathways each: 1 had 2 left free wall accessory pathways, another had a right posterior free wall and right posteroseptal pathway, whereas the third had 2 right posteroseptal pathways approximately 1 cm apart. The remaining 2 patients each had 1 right posteroseptal accessory pathway. Seven of 8 pathways were successfully ablated with a median of 3 radiofrequency pulses. No patient developed complications. Peak serum creatine kinase ranged from 131 to 311 IU/liter, with peak MB fraction 7 to 17 IU/liter, or 5 to 11%. Follow-up electrophysiologic study, 29 to 70 days after ablation, revealed no inducible tachycardia and no evidence of accessory pathway conduction, except for the 1 pathway not ablated. All patients remained asymptomatic 17 to 29 months after ablation. Thus, patients with PJRT can have several accessory pathways that can be safely and effectively eliminated with radiofrequency catheter ablation.

Prospective evaluation of a discriminant function for prediction of recurrent symptomatic ventricular tachycardia or ventricular fibrillation in coronary artery disease patients receiving amiodarone and having inducible ventricular tachycardia at electrophysiologic study.

Induction of ventricular tachycardia (VT) at electrophysiologic study in patients taking amiodarone poorly predicts recurrence of VT. Consequently, a discriminant function was developed (using parameters based on retrospective data) that appeared to identify high-risk patients. These parameters included ventricular effective refractory period, corrected QT interval, initiation of a repetitive ventricular response and the mode of VT induction. In the present study these parameters were prospectively evaluated in 60 patients with coronary artery disease and sustained VT or ventricular fibrillation (VF), in whom VT was still induced at electrophysiologic study during amiodarone therapy. Thirteen patients had recurrent events (sudden death in 8 and sustained VT in 5) and 47 patients had no symptomatic arrhythmia recurrence (follow-up for 16 +/- 2 months, mean +/- standard error of the mean). The ventricular effective refractory period, corrected QT interval and presence of a repetitive ventricular response did not discriminate between patients with and without symptomatic arrhythmia recurrence. However, an easier mode of VT induction during amiodarone therapy versus control was highly predictive of arrhythmia recurrence: 9 of 13 (69%) recurrences were in this group. In contrast, only 4 of 44 (9%) patients who had either the same or harder mode of VT induction had a recurrent event. Overall, 9 of 16 (56%) patients with an easier mode of VT induction had a recurrence, including 6 of the 8 patients with subsequent sudden cardiac death. It is concluded that electrophysiologic testing during amiodarone therapy is useful to identify high-risk patients.

Predictors of fluoroscopy time and estimated radiation exposure during radiofrequency catheter ablation procedures.

The objective of this study was to identify factors that predict fluoroscopy duration and radiation exposure during catheter ablation procedures. The patient population included 859 patients who participated in the Atakr Ablation System clinical trial at 1 of 9 centers (398 male and 461 female patients, aged 36 +/- 21 years). Each patient underwent catheter ablation of an accessory pathway, the atrioventricular junction, or atrioventricular nodal reentrant tachycardia using standard techniques. The duration of fluoroscopy was 53 +/- 50 minutes. Factors identified as independent predictors of fluoroscopy duration included patient age and sex, the success or failure of the ablation procedure, and the institution at which the ablation was performed. Catheter ablation in adults required longer fluoroscopy exposure than it did in children. Men required longer durations of fluoroscopy exposure than did women. The mean estimated "entrance" radiation dose was 1.3 +/- 1.3 Sv. The dose needed to cause radiation skin injury was exceeded during 22% of procedures. The overall mean effective absorbed dose from catheter ablation procedures was 0.025 Sv for female patients and 0.017 Sv for male patients. This degree of radiation exposure would result in an estimated 1,400 excess fatal malignancies in female patients and 2,600 excess fatal malignancies in male patients per 1 million patients.

Surgery for atrioventricular node reentry tachycardia. Results with surgical skeletonization of the atrioventricular node and discrete perinodal cryosurgery.

Surgical treatment options for interruption of atrioventricular node reentrant tachycardia include (1) skeletonization of the atrioventricular node by dissecting it from most of its atrial inputs and (2) discrete cryosurgery of the perinodal tissues by applying a series of sequential cryolesions to the atrial tissues immediately adjacent to the atrioventricular node. Both these techniques attempt to interrupt one of the dual atrioventricular node conduction pathways while preserving the other. This report describes 17 consecutive patients who underwent surgical treatment, 10 patients with skeletonization of the atrioventricular node and seven patients with discrete perinodal cryosurgery. There were 10 female and seven male patients and their ages ranged from 28 to 56 years (mean 38). Two of the 17 patients had Wolff-Parkinson-White syndrome and their accessory pathways were interrupted before the atrioventricular nodal reentrant tachycardia was ablated. All the procedures were performed in a normothermic beating heart while atrioventricular conduction was monitored closely. In the skeletonization technique, the right atrial septum was mobilized and the atrioventricular node exposed anterior to the tendon of the Todaro. The perinodal cryosurgical procedure was also performed through a right atriotomy and a series of sequential 3 mm cryolesions were placed around the borders of the triangle of Koch on the inferior right atrial septum. There were no operative deaths. Two patients who underwent the skeletonization operation had heart block necessitating pacemaker therapy. At postoperative electrophysiologic study, no echoes or atrioventricular nodal reentrant tachycardia were inducible in any of the 17 patients. All patients have remained free of arrhythmia recurrence and have required no antiarrhythmic therapy after a follow-up of 5 to 28 months (mean 14). In conclusion, both atrioventricular node skeletonization and perinodal cryosurgery successfully ablate atrioventricular nodal reentrant tachycardia; however, perinodal cryosurgery appears to be safer in avoiding heart block, is more easily performed, and is our procedure of choice for the management of medically refractory atrioventricular nodal reentrant tachycardia.

Symbolic play in autistic, Down's, and normal children of equivalent mental age.

The study assessed free play and response to modeled symbolic play with animate toys and realistic and substitute accessories in 10 autistic children and 10 Down's syndrome and 10 normal preschooler controls. Groups were matched on Peabody Picture Vocabulary Test mental age (PPVT MA) range and Mdn (2.5 years). Autistic children played less than controls, imitated less well, and, on structured baseline trials, showed lower level play. Symbolic fluency differentiated all groups in structured play. Symbolic fluency for free and structured play was positively correlated with PPVT MA in autistic children; level of play was most highly correlated with PPVT MA in normal children. Findings suggested impaired imitative capacity and symbolic functioning in autism.

Methodological pluralism in clinical nursing research.

Clinical nursing research can benefit from an approach that blends discovery oriented qualitative methods with the objective, numerically based quantitative methods. This paper describes current approaches to clinical research in either the quantitative or qualitative paradigm. The strengths and weaknesses of each of these approaches are discussed. A rationale for methodological pluralism--the blending of the two methods--to understand clinical phenomena is presented.

Who filled first-year family medicine residency positions from 1991 to 2004?

Graduates of U.S. allopathic schools have filled less than one half of the family medicine positions offered in the National Resident Matching Program (NRMP) Match since 2001. Overall fill rates in July have been relatively stable at approximately 94 percent. Family medicine has become reliant on international medical graduates (IMGs), who in 2004 made up 38 percent of first-year residents.

Ablative therapy for ventricular arrhythmias.

Radiofrequency catheter ablation techniques have enjoyed successful applications in patients with a wide variety of supraventricular tachycardias, especially the Wolff-Parkinson-White syndrome and atrioventricular nodal reentry. More recent reports have shown successful applications in patients with atrial tachycardias and atrial flutter. In addition to these, there are now reports of success during attempts to use radiofrequency techniques to eliminate ventricular tachycardia (VT), both in patients without structural heart disease (idiopathic VT) and patients with structural heart disease (primarily coronary artery disease). Techniques to map sites for ablation in patients with idiopathic VT usually include identifying early endocardial activation and using pace mapping. Success rates for ablation of idiopathic VT have been very high (over 90%) in patients with VT arising from the right ventricular outflow tract. Success rates have not been quite as high when VTs arising from sites other than the right ventricular outflow tract are targeted in the patient with idiopathic VT. In patients with VT caused by coronary artery disease, early endocardial activation and pace mapping can be unreliable. In these patients, searching for mid-diastolic potentials or showing concealed entrainment have proved more reliable. When these latter techniques are applied, success rates in eliminating a single focus of VT in a patient with coronary artery disease has been reported to be as high as 60% to 80%. Future therapies will include new energy sources, new (larger and/or cooled) electrodes, and multipoint catheter mapping, possibly using body surface mapping techniques.

Effect of atrioventricular interval during pacing or reciprocating tachycardia on atrial size, pressure, and refractory period. Contraction-excitation feedback in human atrium.

To determine whether a contraction-excitation feedback mechanism exists in human atrium, we investigated the effects of varying the atrioventricular (AV) interval from 0 to 360 msec during AV pacing at a cycle length of 400 msec on atrial pressure, size, and refractoriness in 10 patients (group 1, without supraventricular tachycardia). The same parameters were determined in another 10 patients (group 2, with different spontaneous AV relations) during AV reciprocating tachycardia or AV nodal reciprocating tachycardia and during high right atrial (RA) pacing at the tachycardia cycle length. In group 1 patients, peak and mean RA pressure, RA effective refractory period (RA-ERP), and left atrial (LA) size all decreased to minimal values at an AV interval of 120 msec and remained low as the AV interval was increased and approached 400 msec. The increase in each of the variables from its lowest to greatest value was as follows: Mean systemic blood pressure, 20.9 +/- 3.1 mm Hg; LA size, 0.55 +/- 0.05 cm; RA peak pressure, 10.4 +/- 1.8 mm Hg; RA mean pressure, 3.5 +/- 0.6 mm Hg; and RA-ERP, 22.5 +/- 3.0 msec, p less than 0.001 for each. The weighted mean correlation coefficient with RA-ERP was significant for RA peak pressure and LA size (p less than 0.001 for each). These same relations were investigated in five patients with the Wolff-Parkinson-White syndrome and AV reciprocating tachycardia and five patients with AV nodal reciprocating tachycardia (group 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Catheter ablation for cardiac arrhythmias.

With the introduction of radiofrequency energy, catheter ablation has become an established technique for managing many cardiac rhythm disturbances. High efficacy and safety have been reported for accessory pathway ablation, selective fast and slow atrioventricular nodal pathway ablation to eliminate atrioventricular nodal reentrant tachycardia (while preserving atrioventricular conduction), atrioventricular junctional ablation to control the ventricular response to atrial tachyarrhythmias, ablation of the right bundle branch to eliminate bundle branch reentrant ventricular tachycardia, and ablation of the site of tachycardia origin in patients with ventricular tachycardia unassociated with structural heart disease. In addition, there has been active investigation into ablation techniques for more complex arrhythmias such as atrial tachycardia, atrial flutter, and ventricular tachycardia associated with structural heart disease.