Cardiovascular collapse caused by electrocardiographically silent 60-Hz intracardiac leakage current : Implications for electrical safety

The national standard for safe 60-Hz intracardiac leakage current under a single-fault condition is 50 microA. This standard is intended to protect patients from alternating current (AC) at levels below the threshold for sensation, but the minimum unsafe level for AC in closed-chest humans is not kn...

Full description

Saved in:
Bibliographic Details
Published in:Circulation (New York, N.Y.) N.Y.), 1999-05, Vol.99 (19), p.2559-2564
Main Authors: SWERDLOW, C. D, OLSON, W. H, O'CONNOR, M. E, GALLIK, D. M, MALKIN, R. A, LAKS, M
Format: Article
Language:English
Subjects:
Biological and medical sciences
Diseases of the cardiovascular system
Electric Stimulation - adverse effects
Electrocardiography
Heart - physiopathology
Humans
Medical sciences
Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects)
Ventricular Fibrillation - physiopathology
Ventricular Fibrillation - therapy
Citations: Items that this one cites
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The national standard for safe 60-Hz intracardiac leakage current under a single-fault condition is 50 microA. This standard is intended to protect patients from alternating current (AC) at levels below the threshold for sensation, but the minimum unsafe level for AC in closed-chest humans is not known. To determine this value, we studied 40 patients at testing of implantable cardioverter-defibrillators using a programmable source of 60-Hz AC. We applied AC for 5-second test periods in increasing strengths until ventricular fibrillation (VF) was induced or 1 mA was reached. Two current paths were tested: bipolar, between tip and ring electrodes of a right ventricular pacing catheter, and unipolar, from tip to a remote electrode. We observed a characteristic sequence of 3 responses as AC was increased: (1) intermittent ventricular capture with QRS morphology identical to pacing through the electrodes (minimum value, 20 microA); (2) continuous capture at cycle length 282+/-88 ms (minimum value, 32 microA); and (3) VF persisting after AC termination (minimum value, 49 microA). Continuous capture caused loss of pulsatile arterial pressure and cardiovascular collapse (mean arterial pressure, 32+/-8 mm Hg) for the duration of AC with no ECG evidence of AC stimulation. Thus, the clinical picture was that of hypotensive ventricular tachycardia (VT). The continuous-capture threshold was /=5 seconds should be
ISSN:0009-7322
1524-4539
DOI:10.1161/01.CIR.99.19.2559