Gregory A. Kidwell

Is hospital admission for initiation of antiarrhythmic therapy with sotalol for atrial arrhythmias required?: yield of in-hospital monitoring and prediction of risk for significant arrhythmia complications

OBJECTIVES We sought to determine the yield of in-hospital monitoring for detection of significant arrhythmia complications in patients starting sotalol therapy for atrial arrhythmias and to identify factors that might predict safe outpatient initiation. BACKGROUND The need for hospital admission during initiation of antiarrhythmic therapy has been questioned, particularly for sotalol, with which proarrhythmia may be dose related. METHODS The records of 120 patients admitted to the hospital for initiation of sotalol therapy were retrospectively reviewed to determine the incidence of significant arrhythmia complications, defined as new or increased ventricular arrhythmias, significant bradycardia or excessive corrected QT (QTc) interval prolongation. RESULTS Twenty-five patients (20.8%) experienced 35 complications, triggering therapy changes during the hospital period in 21 (17.5%). New or increased ventricular arrhythmias developed in 7 patients (5.8%) (torsade de pointes in 2), significant bradycardia in 20 (16.7%) (rate <40 beats/min in 13, pause >3.0 s in 4, third-degree atrioventricular block in 1, permanent pacemaker implantation in 3) and excessively prolonged QTc intervals in 8 (6.7%) (dosage reduced or discontinued in 6). Time to the earliest detection of complications was 2.1 +/- 2.5 (mean +/- SD) days after initiation of sotalol, with 22 of 25 patients meeting criteria for complications within 3 days of monitoring. Baseline electrocardiographic intervals or absence of heart disease failed to distinguish a low risk group. Multivariate analysis identified absence of a pacemaker as the only significant predictor of arrhythmia complications (p = 0.022). CONCLUSIONS Because clinically significant complications can be detected with in-hospital monitoring in one of five patients starting sotalol therapy, hospital admission is warranted for initiation of sotalol. Patients without pacemakers are at higher risk for these complications.

Nonthoracotomy- versus thoracotomy-implantable defibrillators. Intention-to-treat comparison of clinical outcomes.

BackgroundNonthoracotomy-implantable cardioverter/defibrillator (ICD) systems may represent a significant advance in the treatment of patients with life-threatening ventricular arrhythmias, but their merits relative to those of the well-established thoracotomy systems remain largely unknown. The objective of this study was to compare the short- and long-term clinical outcomes after attempted ICD implantation via a nonthoracotomy versus thoracotomy approach in similar groups of patients. Methods and ResultsBetween September 1990 and December 1992, 212 consecutive patients underwent attempted ICD system implantation without concomitant cardiac surgery at a single institution. Approach selection was not randomized but rather was based primarily on hardware availability. Primary comparisons of short- and long-term outcome were performed according to the “intention-to-treat” principle. Implantation was attempted via a nonthoracotomy approach in 120 patients (57%) and via a thoracotomy approach in 92 patients (43%). Prior cardiac surgery was more prevalent in the nonthoracotomy patients; otherwise, groups did not differ significantly in terms of prognostically relevant clinical characteristics. Nonthoracotomy implantation was successful in 101 patients (84%). After crossover to thoracotomy implantation (14 patients), the eventual success rate for ICD system implantation was 96% in the nonthoracotomy group. Thoracotomy implantation was successful in 89 patients (97%). Operative mortality was 3.3% in the nonthoracotomy and 4.3% in the thoracotomy groups (P = .73). Nonthoracotomy group patients were less likely to experience postoperative congestive heart failure (6% versus 16%; P = .02) or supraventricular arrhythmia (6% versus 18%; P = .004) and had significantly shorter postoperative intensive care and total hospitalization. Total hospital costs were significantly lower in the nonthoracotomy group (

Influence of amiodarone on QT dispersion in patients with life-threatening ventricular arrhythmias and clinical outcome

32,205 versus

Evolving concepts in radiofrequency catheter ablation of atrioventricular nodal reentry tachycardia

37,265; P = .001). After a follow-up of 16 ± 9 months, there were 17 deaths in the nonthoracotomy group (none sudden) and 12 deaths in the thoracotomy group (1 sudden). One- and 2-year Kaplan-Meier survival probabilities were .87 (95% CI, .78 to .91) and .80 (95% CI, .68 to .88) in the nonthoracotomy group and .90 (95% CI, .82 to .95) and .87 (95% CI, .77 to .93) in the thoracotomy group (P = .56; log-rank test). ConclusionsNonthoracotomy ICD implantation is associated with reduced surgical morbidity, postoperative hospital care requirement, and hospital costs and has similar efficacy in preventing sudden death relative to the thoracotomy approach. From these nonrandomized data, it appears that a nonthoracotomy approach should be considered preferable in most patients requiring ICD therapy.

Characterization of left atrial appendage Doppler flow in atrial fibrillation and flutter by Fourier analysis.

UNLABELLED Increased QT dispersion, defined as the difference between the maximum and minimum QT interval on the standard 12-lead electrocardiogram is assumed to reflect regional inhomogeneity of ventricular repolarization and has been shown to be associated with an increased risk of arrhythmic events. The purpose of the present study is to examine the influence of amiodarone on QT dispersion in patients with life-threatening ventricular arrhythmias and to evaluate the predictive value of QT dispersion after amiodarone therapy for further arrhythmic events. ECGs were obtained in 47 patients 1-2 days before and 6-8 weeks after amiodarone was started. All patients had coronary artery disease with a mean EF of 34 +/- 14%. The QT interval was measured in each lead of a digitized ECG displayed on a high resolution monitor (250 mm s-1). Amiodarone therapy resulted in a significant increase in the maximal QTc interval (476 +/- 44 to 505 +/- 44 ms, p < 0.001). However, measurement of QT dispersion (70 +/- 34 vs 73 +/- 29 ms) and Qtc dispersion (78 +/- 37 vs 77 +/- 31 ms) revealed no significant difference before and after amiodarone. During a one year follow-up period 26 patients were free of arrhythmic events and 7 patients developed further arrhythmic events. The remaining 14 patients were excluded from the one year follow-up analysis because of drug discontinuation (n = 8), death due to heart failure (n = 1), medical intervention (n = 3) and incomplete follow-up (n = 2). No measure of QT dispersion was predictive of recurrent arrhythmic events during treatment with amiodarone. CONCLUSION Treatment with amiodarone results in significant QT prolongation without altering QT dispersion. Measurements of QT dispersion were not predictive of amiodarone efficacy in this patient population.

A Technique for Rapid Transfemoral Catheterization of the Coronary Sinus with Multielectrode Catheters

Our results and those of others (Table I) suggest that both anatomic and electrogram (potential) approaches are highly successful in eliminating AVNRT. The use of slow-pathway potentials appears to minimize lesion delivery and to be associated with a very small likelihood of complete AV block. Approaches aimed directly at the midseptum also appear to reduce lesion delivery. It is important, however, to understand that the fast and slow AV-nodal pathways are not always confined to anterosuperior (fast) and posteroinferior (slow) locations (at least as they are determined fluoroscopically). On occasion, the slow pathway may be ablated anteriorly and the fast pathway posteriorly. Our three inadvertent successful fast-pathway ablations support these findings. We prefer to conceptualize the AV node as having three ablation zones. Ablation in the anterosuperior zone most often affects fast-pathway conduction; ablation in the posteroinferior zone most often affects slow pathway conduction; and ablation in the midseptal region predominantly affects slow-pathway conduction. Lesions applied to the midseptum do, however, appear more likely to affect inadvertently the fast (or both) pathway(s), probably because of the anatomic convergence of the posteroinferior and anterosuperior AV-nodal approaches in this region. A preliminary report by Wu et al. supports this three-zone concept. The subsequent larger series reported by this group has raised concern that midseptal approaches may be associated with too great a risk of complete AV block. On the other hand, approaches guided exclusively by potentials may be associated with much longer procedure times. Controversy exists over the acceptable end point for ablation procedures. We have not found it necessary routinely to eliminate dual-nodal conduction to maintain a low (3.2%) overall recurrence rate. Aggressive attempts to eliminate all evidence of slow-pathway conduction must be balanced against the risk of inadvertent complete AV block. In conclusion, cumulative data and our clinical experience with ablation of AVNRT suggest that it is possible to be both pragmatic and highly successful. The key components of our approach are (1) an anatomically based, systematic, time-limited search for potentials; (2) elimination of unnecessary lesions that are too atrial or too ventricular to involve the reentrant circuit; (3) a caudocephalad approach that avoids excessively anterior initial lesions, which may result in inadvertent complete AV block; and (4) avoidance of unnecessary lesions in the most inferoposterior sector, which results in patient discomfort and low clinical efficacy. This approach is safe (with minimal risk of AV block), reproducible, and efficacious.

901-58 Slow Fragmented Intraatrial Conduction Post Maze Procedure: A Substrate for Intraatrial Reentrant Tachycardia and Marker for Effective Radiofrequency Ablation

The aim of this study was to characterize left atrial appendage mechanical function in atrial fibrillation and flutter by Fourier analysis to analyze frequency and regularity of flow. Left atrial appendage function is central to a patients risk for thromboembolism. Although the function of the appendage can be analyzed by Doppler echocardiography in sinus rhythm, its mechanical function in atrial fibrillation and flutter has not been well characterized. This lack of adequate definition is caused by the complexity and temporal variability of the Doppler flow profiles. We assessed left atrial appendage function in 21 cases of atrial fibrillation (n - 11) and flutter (n = 10) and five in sinus rhythm with transesophageal Doppler echocardiography. Doppler profiles were examined by Fourier analysis, and the power spectra compared and analyzed between patients with atrial fibrillation and flutter. Left atrial appendage Doppler flow in atrial fibrillation produced Fourier spectra over a narrow band of frequencies with a peak frequency of 6.2 +/- 1.0 Hz, significantly higher than in atrial flutter (3.9 +/- 0.6 Hz, p < 0.00001). Additionally, a significant difference in subharmonic modulation (spectral power below the peak frequency) was observed between atrial appendage flow in atrial fibrillation and flutter, because 37% +/- 16% of the total spectral power was achieved before the dominant frequency in atrial fibrillation compared with 20% +/- 14% in atrial flutter (p = 0.02). Conversely, patients in sinus rhythm exhibited broad-banded Fourier spectra with most of the power in discrete frequency spikes at harmonics above the fundamental frequency with very little subharmonic modulation (1% +/- 0.05%). Left atrial appendage function in atrial fibrillation and flutter can be well characterized by Fourier analysis of Doppler flow. Atrial fibrillation has higher dominant frequencies and greater subharmonic modulation compared with flutter. Moreover, atrial fibrillation demonstrated quasiperiodic contraction patterns typically found in chaotic systems. Fourier analysis of left atrial appendage contraction patterns may therefore have significant promise in providing insights into mechanisms of atrial fibrillation and thromboembolism.

Premature Ventricular Contraction-Induced Polymorphic Ventricular Tachycardia after Leadless Pacemaker Implantation: A Unique Adverse Effect of Leadless Pacing

To minimize procedural and fluoroscopic times and avoid the risks of vascular injury and pneumothorax, some investigators have advocated elimination of routine placement of a coronary sinus (CS) catheter during electrophysiological procedures. We hypothesized that expedient and reproducible CS catheterization could be performed with minimal patient risk by utilizing a femoral vein approach. Fifty consecutive patients referred for radiofrequency ablative procedures underwent attempted CS catheterization using a 6‐French steerable, quadripolar catheter via a femoral vein. Procedures were performed utilizing single‐plane fluoroscopy without contrast angiographic aid by operators experienced in the technique. Successful catheterization was defined by the attainment, in < 15 minutes, of a stable catheter position with the distal electrode at or beyond the lateral margin of the heart. Successful catheterization of the CS was achieved in 47 (94%) patients. Selective pacing of the left atrium without patient discomfort was possible in all, eliminating the need for a right atrial pacing catheter. The median time to successful catheterization was 1.4 minutes (range 0.3–14.7). Only six patients required > 5 minutes. The median fluoroscopic time required was 1.2 minutes (range 0.3–12.7). No clinical variable was predictive of catheterization failure or time to successful catheterization. No complications were observed as a result of this technique. This prospective evaluation demonstrates that catheterization of the CS via a femoral vein approach is highly successful, expedient, and safe. The ability to selectively pace the left atrium may eliminate the requirement for a right atrial catheter.

Internal cardioversion of atrial fibrillation using standard ventricular implantable cardioverter-defibrillators

The maze procedure is a surgical alternative for treating drug refractory atrial fibrillation. Although post-maze atrial fibrillation has been noted, slow intraatrial tachycardias have not been reported. Of 31 maze patients with a mean follow-up of 22 ± 9 months, 6 underwent electro physiologic (EP) testing (9 ± 6 months post-op) for symptoms suggestive of recurrent arrhythmia. Results Conduction was significantly prolonged through the right compared to the left atrium (167 ± 44 vs 57 ± 10 ms, p l 0.01). However, right atrial effective refractory periods were normal (237 ± 29 ms). Programmed atrial stimulation induced sustained slow intraatrial reentry in two patients (cycle lengths of 420 and 520 ms) and atrial flutter (cycle length 190 ms) in one patient. The slow reentrant tachycardias were successfully ablated with radiofrequency energy in both patients. Neither patient has experienced a clinical recurrence after 14 and 9 months. Electrograms at successful ablation sites were markedly fragmented during sinus rhythm, with an apparent reversal of near/far-field activation during tachycardia (see figure). Download : Download high-res image (50KB) Download : Download full-size image Conclusions Slow intraatrial tachycardias may be observed in symptomatic post-maze patients. Our findings are consistent with slow conduction and reentry along a line of conduction block. Radiofrequency catheter ablation can be curative for these tachycardias.

976-9 Effects of Facilitation on Human AV Nodal Fast and Slow Pathways

Introduction The MICRA transcatheter leadless pacing system (Medtronic, Minneapolis, MN) is a revolutionary shift in pacemaker technology. The leadless design allows pacing therapies to be offered through a minimally invasive transcatheter approach via the femoral vein to patients in whom traditional implants would have posed either excessive technical or excessive infection risks. As with any novel technology, the possibility of unique complications must be thoroughly described. We demonstrate a case of recurrent premature ventricular contraction (PVC)-induced polymorphic ventricular tachycardia (PMVT) after MICRA leadless pacemaker deployment, which resolved with extraction and reimplantation at a different right ventricular site.