Use of IV (Conscious) Sedation/Analgesia by Nonanesthesia Personnel in Patients Undergoing Arrhythmia Specific Diagnostic, Therapeutic, and Surgical Procedures. This article is intended to inform practitioners, payers, and other interested parties of the opinion of the North American Society of Pacing and Electrophysiology (NASPE) concerning evolving areas of clinical practice or technologies or both, that are widely available or are new to the practice community. Expert, consensus documents are so designated because the evidence base and experience with the technology or clinical practice are not yet sufficiently well developed, or rigorously controlled trials are not yet available that would support a more definitive statement. This article has been endorsed by the American College of Cardiology, October 1997.

Radiofrequency current was used recently to ablate accessory connections in patients with supraventricular tachycardia.1–5 After locating the accessory connection by electrophysiologic mapping, ablation is achieved by positioning a 7Fr catheter (with 4 mm electrode at distal tip) within the ipsilateral cardiac chamber and adjacent to the accessory connection. Radiofrequency current is then delivered at the point of earliest electrical activation along the atrioventricular valve annulus. For a left-sided accessory connection, the catheter is usually passed retrograde across the aortic valve into the left ventricle and under the posterior mitral valve leaflet. For a right-sided accessory connection, the catheter is passed anterograde into the right atrium or ventricle.1–5 Systematic evaluation of the effects of this technique on the function of all cardiac valves has not been reported. This study evaluates the effects of catheter manipulation and radiofrequency current delivery on valve competence.

C.S. Mott Children's Hospital and Department of Pediatrics, University of Michigan, Ann Arbor, Michigan, USA

To determine the thresholds for transesophageal atrial capture, as well as factors that might influence the thresholds, the authors measured the minimal current and pulse duration required to pace the atrium through transesophageal bipolar lead systems in 32 patients during 42 trials. Mathematical modeling suggested that the current density at the posterior atrial wall was dependent upon the current delivered, the electrode distance, and, most importantly, the esophageal-atrial geometry, expressed as the distance from the esophagus to the excitable tissue. To examine this esophageal-atrial distance, 17 different patients, aged 11 months to 44 years, were studied concurrently with either computerized tomography or magnetic resonance imaging of the chest. The thresholds needed to capture the atrium from the esophagus were 13.2 +/- 3.7 mA at a pulse duration of 5.8 +/- 3.1 msec. Further, the data demonstrated that the threshold for transesophageal atrial pacing was poorly related to the patient's age or size. The fit between these data and the mathematical model suggested that the distance between the left atrial posterior wall and the esophagus was approximately 5-6 mm. Likewise, the minimal esophageal-atrial distance as measured by the two imaging techniques was equal to or less than 3.3 mm. These observations suggest that the distance (anterior-posterior dimension) between left atrial posterior wall and the esophagus is small and remains constant despite obvious changes in somatic and linear growth.

To determine right ventricular (RV) endocardial activation (surface ECG to fast deflection of intracardiac electrogram) we measured activation of (a) right ventricular apex (RVA) (N=34), (b) right ventricular outflow (RVO) (N=6) and (c) right ventricular inflow (RVI) (N=3) using closely spaced (2mm) bipolar electrode catheter. Catheter positions were verified by biplane fluoroscopy with a C-arm rotated in the horizontal plane. Median age of children studied was 10 yrs (range 0.5-20.8). None had right bundle branch block (RBBB) on surface ECG. Using frequency band pass (15-300 Hz) RVA was 25.9±8.2 msec (10-42) and did not correlate with either age or RV pressure. RVI was 44.7±9.8 msec (39-56) and was 68% longer than RVA. RVO was 50.7±11.0 msec (33-66) and was 89% longer than RVA. The influence of high (150-1000 Hz) and low (15-300 Hz) filters on RVA was evaluated in 13 of these patients and 6 others with RBBB. RVA at high frequency band was on the average 1.2 msec shorter than and correlated well (r=.96) with RVA at the low frequency range. We conclude that RV endocardial activation, measured at cardiad catheterization, proceeds in the expected manner and time course, with no clinically important difference between RVA recorded at high and low frequencies. Thus the method may be useful in defining RV endocardial activation disturbances prior to and after intracardiac surgery for congenital heart disease.