Document Detail


The zone of vulnerability to T wave shocks in humans.
MedLine Citation:
PMID:  9147699     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
INTRODUCTION: Shocks during the vulnerable period of the cardiac cycle induce ventricular fibrillation (VF) if their strength is above the VF threshold (VFT) and less than the upper limit of vulnerability (ULV). However, the range of shock strengths that constitutes the vulnerable zone and the corresponding range of coupling intervals have not been defined in humans. The ULV has been proposed as a measure of defibrillation because it correlates with the defibrillation threshold (DFT), but the optimal coupling interval for identifying it is unknown. METHODS AND RESULTS: We studied 14 patients at implants of transvenous cardioverter defibrillators. The DFT was defined as the weakest shock that defibrillated after 10 seconds of VF. The ULV was defined as the weakest shock that did not induce VF when given at 0, 20, and 40 msec before the peak of the T wave or 20 msec after the peak in ventricular paced rhythm at a cycle length of 500 msec. The VFT was defined as the weakest shock that induced VF at any of the same four intervals. To identify the upper and lower boundaries of the vulnerable zone, we determined the shock strengths required to induce VF at all four intervals for weak shocks near the VFT and strong shocks near the ULV. The VFT was 72 +/- 42 V, and the ULV was 411 +/- V. In all patients, a shock strength of 200 V exceeded the VFT and was less than the ULV. The coupling interval at the ULV was 19+/- 11 msec shorter than the coupling interval at the VFT (P < 0.001). The vulnerable zone showed a sharp peak at the ULV and a less distinct nadir at the VFT. A 20-msec error in the interval at which the ULV was measured could have resulted in underestimating it by a maximum of 95 +/- 31 V. The weakest shock that did not induce VF was greater for the shortest interval tested than for the longest interval at both the upper boundary (356 +/- 108 V vs 280 +/- 78 V; P < 0.01) and lower boundary (136 +/- 68 msec vs 100 +/- 65 msec; P < 0.05). CONCLUSIONS: The human vulnerable zone is not symmetric with respect to a single coupling interval, but slants from the upper left to lower right. Small differences in the coupling interval at which the ULV is determined or use of the coupling interval at the VFT to determine the ULV may result in significant variations in its measured value. An efficient strategy for inducing VF would begin by delivering a 200-V shock at a coupling interval 10 msec before the peak of the T wave.
Authors:
C D Swerdlow; D J Martin; R M Kass; S Davie; W J Mandel; E S Gang; P S Chen
Related Documents :
3661619 - 5-fluorouracil cardiotoxicity: left ventricular dysfunction and effect of coronary vaso...
17667459 - Complications of myocardial infarction.
1891019 - Cardiogenic shock after acute myocardial infarction. incidence and mortality from a com...
7249259 - Beneficial actions of a free radical scavenger in traumatic shock and myocardial ischemia.
10576949 - Shock-induced figure-of-eight reentry in the isolated rabbit heart.
8848389 - A critical period of ventricular fibrillation more susceptible to defibrillation: real-...
10362689 - No modulates myocardial o2 consumption in the nonhuman primate: an additional mechanism...
11336849 - Using postoperative cardiac troponin-i (cti) levels to detect myocardial ischaemia in p...
15182599 - Markers to define ischemia: are they ready for prime time use in patients with acute co...
Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  8     ISSN:  1045-3873     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  1997 Feb 
Date Detail:
Created Date:  1997-05-15     Completed Date:  1997-05-15     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  145-54     Citation Subset:  IM    
Affiliation:
Division of Cardiology, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:
Aged
Data Collection
Electric Countershock*
Electrodes
Electroshock
Female
Humans
Male
Middle Aged
Ventricular Fibrillation / physiopathology*,  therapy*
Grant Support
ID/Acronym/Agency:
HL-50259/HL/NHLBI NIH HHS; HL-F52319/HL/NHLBI NIH HHS

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


Previous Document:  Electrocardiographic and electrophysiologic characterization of atypical atrial flutter in man: use ...
Next Document:  Induction of autologous tumor-specific cytotoxic T-lymphocyte activity against a human renal carcino...