Response to Atrial Extrastimulus During Supraventricular Tachycardia: What Is the Mechanism?

Arrhythmia Rounds . We describe a case illustrating the potential challenges in distinguishing AV nodal reentry tachycardia (AVNRT) from automatic junctional tachycardia (JT). While an early atrial extrastimulus advanced the next His and ventricular depolarization without tachycardia termination, suggesting JT, other features indicated the correct diagnosis of AVNRT. This teaching case demonstrates a novel exception to a recently reported diagnostic pacing maneuver and illustrates the importance of considering response to multiple maneuvers in reaching a diagnosis of SVT mechanism. (J Cardiovasc Electrophysiol, Vol. 24, pp. 359‐363, March 2013)     

Observations From Intraatrial Recordings on the Termination of Electrically Induced Atrial Fibrillation in Humans

Background: The circulating wavelet hypothesis suggests that atrial fibrillation could terminate by either progressive fusion or simultaneous block of all wavelets. Methods: Intraatrial recordings from the right atrial free wall were made during procainamide induced (n = 8) or spontaneous (n = 7) termination of electrically induced atrial fibrillation in 14 patients. Atrial rate, mean magnitude squared coherence, and direction of activation during sequential electrograms were measured. Rate and coherence were calculated from the earliest point within 5 minutes prior to termination as well as from the 4-second interval just prior to termination. Results: Termination was directly to sinus rhythm (13 episodes) or to atrial flutter (2 episodes). For the eight procainamide induced terminations, rate decreased between the first measurement and the measurement just prior to termination, from 443 ±127 beats/ min to 322 ± 119 beats/min. For the seven spontaneous terminations, rate also decreased from 373 ± 119 beats/min to 323 ± 88 beats/min; however, a slight increase in atrial rate prior to termination was observed in three episodes. No specific patterns of atrial cycle lengths were seen during the final few seconds of fibrillation. No increase in coherence was observed. In seven episodes, recordings were made using orthogonal bipoles in the x, y, and z directions, allowing direction of activation of wavefronts to be measured. Three episodes showed multiple instances where direction of activation remained similar over several electrograms as we have previously reported for chronic fibrillation. However, no such instances precipitated termination in any of the seven episodes. Conclusions: Atrial fibrillation usually terminates directly to sinus rhythm and does so abruptly and without forewarning. While we and others have previously reported that the rate of atrial fibrillation decreases with procainamide infusion, a decrease in the rate of atrial fibrillation is not required for the rhythm to terminate and consequently may not be a part of the termination process at all. Coherence does not demonstrate a progressive increase in the organization of atrial fibrillation prior to termination. Lack of stabilization in the direction of activation of wavefronts in the final few seconds also fails to support fusion of wavefronts as the mechanism of termination of atrial fibrillation. Simultaneous block of all wavelets is consistent with, but not proven by our observations.     

Outcomes in Patients Requiring Cardioversion Following Catheter Ablation of Atrial Fibrillation

Outcomes of Cardioversion Post AF Ablation.   Introduction: Early recurrence of atrial tachyarrhythmias is commonly noted after catheter ablation of atrial fibrillation (AF). The long-term outcomes of patients who require cardioversion for persistent AF after AF ablation is not known. This study reports the outcomes of patients who underwent cardioversion for persistent AF or atrial flutter following an AF ablation procedure.
Methods: The patient population comprised 55 patients (mean age 58 ± 10 years, 35% paroxysmal) who underwent catheter ablation of AF and subsequently required electrical cardioversion for persistent AF (45 patients) or atrial flutter (10 patients). Cardioversion was defined as early (within 90 days of the ablation procedure) or late (between 90 and 180 days following ablation).
Results: The mean follow-up duration was 15 ± 8 months. Forty-six of the 55 patients (84%) patients experienced recurrence during follow-up. The average time to recurrence after cardioversion was 37 days. Of the 55 patients, 8 (15%) patients had a complete success, 11 (20%) patients had a partial success and 36 patients (65%) had a failed outcome. Seven of the 43 patients (16%) who underwent early cardioversion had a complete success as opposed to one of 12 patients (8%) who underwent late cardioversion (P = 0.49).
Conclusions: This study shows that >80% of patients who undergo cardioversion for persistent AF or atrial flutter after AF ablation have recurrence. The timing of cardioversion did not affect the outcome. These findings allow clinicians to provide realistic expectations to patients regarding the long-term outcome and/or requirement for a second ablation procedure. (J Cardiovasc Electrophysiol, Vol. 21, pp. 27–32, January 2010)     

A Prospective Study Evaluating the Role of Obesity and Obstructive Sleep Apnea for Outcomes After Catheter Ablation of Atrial Fibrillation

Effect of Obesity and OSA on Outcomes Post AF Ablation . Background: Obesity and obstructive sleep apnea (OSA) have a strong association with atrial fibrillation (AF). The purpose of this study was to prospectively determine the effects of obesity, assessed by the body mass index (BMI) and OSA on the efficacy of catheter ablation of AF. Methods: The patient population consisted of 109 patients (mean age: 60 ± 10 years, 79% male, 67% paroxysmal, mean BMI 28 ± 5 kg/m²) who underwent catheter ablation of AF. Based on BMI, patients were classified as normal (<25 kg/m²), overweight (≥25 and <30 kg/m²), or obese (≥30 kg/m²). OSA was assessed by the Berlin questionnaire. Clinical success was defined as at least 90% reduction in AF burden after 3‐month blanking period. Mean duration of follow‐up was 11 ± 4 months. Results: Of the 75 patients with clinical success, 25 (33%) had normal BMI, 29 (39%) were overweight, and 21 (28%) were obese. Among the 34 patients with failed outcome, 5 (15%) had normal BMI, 14 (41%) were overweight, and 15 (44%) were obese (P = 0.04). Twenty‐eight of the 48 patients with OSA (58%) had clinical success as opposed to 47 of the 61 patients (77%) without OSA (P = 0.036). On multivariate analysis, only BMI emerged as an independent predictor of procedural failure ((OR 1.11, CI: 1.00–1.21, P = 0.03). Conclusions: The results of this prospective study show that obesity, a modifiable risk factor, is an independent predictor of procedural failure after catheter ablation of AF. Whether treating obesity may improve the results of catheter ablation of AF warrants further investigation. (J Cardiovasc Electrophysiol, Vol. 21, pp. 521‐525, May 2010)     

CAN FRONTOTEMPORAL DEMENTIA AND ALZHEIMER'S DISEASE BE DIFFERENTIATED USING A BRIEF BATTERY OF TESTS?

Objective. To compare the performance of patients with frontotemporal dementia (FTD) and Alzheimer's disease (AD) on a range of simple neuropsychological tests. Design. A battery of neuropsychological tests easily applied at the bedside, consisting of traditional tests of memory, attention and executive function, were given together with tests of motor sequencing and examination of frontal release signs. In addition, we devised a theoretically motivated test of dual attention—a story with distraction which also contained a ‘social dilemma’. Setting. Specialist memory and cognitive disorders clinic. Patients. 12 patients with FTD and 12 patients with AD, matched for overall level of dementia on the Mini-Mental State Examination, were selected. Results. In general, the difference in results between FTD and AD patients was small. However, a composite score derived from the presence of a grasp and pout reflex, the number of perseverations during category fluency for animals and response to the social dilemma within the two stories produced a sensitivity of 83.3% and specificity of 91.6%. There was also a highly significant difference between patients with FTD and AD in scores achieved on the Clinical Dementia Rating Scale reflecting the marked change in behaviour that patients with FTD suffer, even at a stage when memory functions are well preserved. Conclusion. Traditional neuropsychological tests were poor at differentiating cases of FTD and AD; however, a composite (SIFTD) score appears potentially useful but requires prospective validation. Better methods of assessing the changes in comportment that characterize the early stages of FTD are required. © 1997 by John Wiley & Sons, Ltd.     

Interferon-α is a Potent Inhibitor of Basic Fibroblast Growth Factor-Stimulated Cell Proliferation in Human Uterine Cells

PROBLEM: Abnormal uterine bleeding is a significant health problem for many women and is the number-one reason for performing hysterectomy in the United States. Leiomyomas (uterine fibroids) are benign neoplams that are a frequent cause of abnormal uterine bleeding. The goal of this study was to assess the effects of the anti-angiogenic cytokine, interferon (INF)-α, on the proliferation of both leiomyoma and normal uterine cells. METHOD OF STUDY: Primary cultures of leiomyoma, myometrial, and endometrial stromal cells were established for in vitro study. The effects of INF-α (10, 100, and 1000 U/ml) were tested on serum-stimulated and basic fibroblast growth factor-stimulated cell proliferation using the [³H]thymidine incorporation assay. RESULTS: INF-α was a potent inhibitor of cell proliferation for all three cell types, with endometrial stromal cells showing the greatest sensitivity. The antiproliferative effect did not appear to result from toxic effects on the cells. CONCLUSION: INFs may prove to be useful therapeutic agents for the treatment of leiomyoma-related abnormal uterine bleeding.