Effect of Electrode Length on Atrial Defibrillation Thresholds

Electrode Length for Atrial Defibrillation. Introduction: Catheter-based electrodes have been used previously to terminate episodes of atrial fibrillation in animals and man. Typically, these electrodes span 6 to 7 cm, and lowest energy requirements are achieved when these electrodes are positioned in the distal coronary sinus and in the right atrium. The purpose of this study was to evaluate the use of longer electrode lengths for atrial defibrillation. Methods and Results: In 15 patients, two decapolar catheters were inserted, one into the distal coronary sinus and one in the right atrium. To provide longer electrodes lengths, a third catheter was inserted and alternated positioned in the right atrium or coronary sinus. A 6-cm electrode span was obtained by using the distal 8 rings on the coronary sinus catheter or 8 consecutive electrodes on the right atrial catheter and increased from 6 to 11 cm by connecting consecutive, nonoverlapping rings of the third catheter with the 10 rings of the initial right atrial or coronary sinus catheter. Atrial defibrillation thresholds were determined twice, in a randomized order, in each patient for each of the three combinations of electrode lengths. All 15 patients could he successfully converted to sinus rhythm without complications; however, one patient could be converted reproducibly with only 2 of the 3 electrode combinations. Mean thresholds were 306 ± 102 V, 5.9 ± 4.0 J for the 6 cm/6 cm electrode length combination with an impedance of 72 ± 18 ω. For the electrode combination using the 11-cm electrode in the right atrium, the defibrillation threshold was 296 ± 107 V, 5.8 ± 3.9 J with an impedance of 61 ± 17 ω and was 294 ± 91 V, 5.6 ± 3.6 J with an impedance of 55 ± 11 ω for the 11-cm electrode in the coronary sinus. There were no significant differences in defibrillation voltage or energy (P > 0.05) associated with the longer electrode lengths; however, the longer electrode lengths did significantly lower shock impedance (P < 0.05). Conclusion: The use of longer electrodes, when using the right atrium to coronary sinus shock vector, does not lower the defibrillation requirements for restoration of sinus rhythm.     

Complications with Angio‐Seal™ Vascular Closure Devices Compared with Manual Compression after Diagnostic Cardiac Catheterization and Percutaneous Coronary Intervention

Objectives

This study assessed and compared vascular complications in CATHs and PCIs using an Angio‐Seal? vascular closure device (VCD) versus manual compression (MC).

Methods

Secondary data analysis of a population‐based multiyear cohort database was conducted to compare femoral access‐related vascular outcomes in cardiac procedures using VCD and MC between May 1, 2006 and December 31, 2010. The primary outcome was any vascular complication. Propensity score adjusted analysis was conducted to reduce bias associated with covariate imbalance between the groups compared.

Results

Of the 11,897 procedures, 7,063 (59.4%) used a VCD. Vascular complications occurred in 174/8,796 (2.0%) of CATHs and 82/3,004 (2.7%) of PCIs. In the CATH sample, the odds of vascular complication were 57% lower if a VCD was used (OR = 0.43, 95% CI 0.31–0.60). For the PCI sample, the risk was 49% lower if a VCD was used (OR = 0.51, 95% CI 0.31–0.81).

Conclusions

A low incidence of vascular complications was observed with the use of an Angio‐Seal VCD relative to MC for both procedures.

     

Substance use disorder: abuse, dependence and dyscontrol

The purpose of this paper is to review the diagnostic concepts of substance abuse and substance dependence provided in DSM-III, DSM-III-R, and the forthcoming DSM-IV. The review incorporates the principles that there are no infallible criteria for identifying taken a person lacks sufficient control over the usage of a drug, that dyscontrol exists on a continuum, that substance use dyscontrol shares many formal properties with behavioral dyscontrol within other domains, and that the diagnosis of a mental disorder should be free of moralistic connotations. We conclude the paper with an alternative proposal, wherein the DSM-IV diagnoses of abuse and dependence are collapsed within one diagnosis of substance dyscontrol disorder and physiological substance dependence is placed with the diagnoses of substance intoxication and substance withdrawal.     

Rapid Atrial Pacing Does Not Decrease the Atrial Defibrillation Threshold

The aim of the study was to evaluate the effect of preshock atrial pacing on the atrial defibrillation threshold (DFT) during internal cardioversion of AF. The implantable atrial defibrillator has been added to the therapeutic options for patients with recurrent episodes of persistent AF. Although the device is efficient in restoring sinus rhythm, patient discomfort is a limitation. Methods that lower the ADFT are needed. Eleven patients with AF underwent internal cardioversion. In a randomized, crossover design, ADFT testing was performed, applying a step-up protocol starting at 100 V. Rapid atrial pacing was performed with a right atrial catheter for 20 seconds at 90% of the average cycle length of the fibrillatory waves and was immediately followed by a biphasic defibrillation shock. At each energy level, pacing + shock was compared to shock only, until the level at which sinus rhythm was restored by both modes. The step-up protocol was thereafter repeated using the inverse sequence of the two modes. A total of 19 ADFTs were obtained. For 10 the ADFT was lower with pacing + shock, in 4 equal and in 5 higher, than with shock only. The ADFT (mean ± SD) with pacing + shock was   260 ± 84   V   (3.4 ± 2.9 J)   and did not differ from shock only:   268 ± 85   V   (3.8 ± 3.0 J) (P > 0.05)   . The coefficient of variation and the coefficient of reproducibility for pacing + shock was 16% and 60 V, respectively, and for shock only 17% and 61 V. Rapid atrial pacing did not influence the internal ADFT in AF. The randomized, crossover protocol used was reproducible between different modes, and seems useful when testing the impact of different interventions on the ADFT. (PACE 2003; 26[Pt. I]:1461–1466)     

REVIEWS

Book reviewed in this article: Self-advocacy skills training (report of two workshops held between April and September 1987) Alison Wertheimer Responding to adolescent needs. A pastoral care approach (Special needs in ordinary schools series) Polly Lowe The visually handicapped child in your classroom (Special needs in ordinary schools series) Elizabeth K. Chapman and Juliet M. Stone Behaviour problems in mental handicap: an annotated bibliography 1970–1985 Kenneth Day, Joyce Hamilton, and Paul Smith     

Using DISTAR Language in a unit for children with language disorders

DISTAR Language was used to teach half the children in a unit for language disordered children. Although some children in both groups received speech therapy from the speech therapist and general language work from the teacher, the greatest difference between the groups was in the use of DISTAR Language by the experimental group. The results show that the language of both groups improved to a similar degree, but only the experimental group (which included the most severely affected language and speech disordered children) improved significantly in intelligence. The results are compared with other studies of DISTAR Language and the conclusion is that further studies would be profitable.