Document Detail


Effect of sustained load on dispersion of ventricular repolarization and conduction time in the isolated intact rabbit heart.
MedLine Citation:
PMID:  8718979     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
INTRODUCTION: It is well known that myocardial stretch can elicit ventricular arrhythmias in experimental models. However, previous reports have predominantly documented stretch-induced arrhythmias during short, pulsatile stretch. The arrhythmogenic mechanism of sustained static stretch is incompletely understood. METHODS AND RESULTS: To examine the influence of sustained load on several electrophysiologic parameters, a latex balloon was placed into the left ventricle of ten isolated Langendorff-perfused rabbit hearts and filled with a neutral volume of fluid. The heart was paced from a catheter inside the right ventricle (apicoseptal endocardial position), and the following parameters were studied during steady-state pacing with a cycle length of 500 msec (S1) and during extrastimulation (S2, base drive of 8 beats): monophasic action potential (MAP) durations at 90% repolarization (APD90) from 5 to 6 epicardial electrodes located on both ventricles and one right ventricular endocardial contact electrode; dispersion of APD90 (range of MAP durations from all electrodes); effective refractory period (ERP) and longest activation time (pacing stimulus to MAP upstroke). After baseline recordings, the balloon inside the left ventricle was filled with a volume of 1.0 mL of fluid by means of a servo-controlled pump. The ERP was significantly shortened from 198 +/- 9 msec at baseline to 183 +/- 8 msec during sustained load (P < 0.03). Similarly, the average APD90 was shortened from 180 +/- 5 msec at baseline to 175 +/- 6 msec during sustained load (P < 0.006) with steady-state pacing and from 178 +/- 6 msec to 170 +/- 8 msec during premature extrastimulation (P < 0.03). At the same time, dispersion of APD90 was increased from 27 +/- 5 msec to 38 +/- 6 msec (P < 0.002) during steady-state pacing and from 28 +/- 4 msec to 38 +/- 6 msec (P = 0.013) during premature extrastimulation. The longest activation time among all MAP recordings was increased from 39 +/- 2 msec to 43 +/- 3 msec (P = 0.003) during steady-state pacing and from 56 +/- 6 msec to 69 +/- 6 msec during premature extrastimulation (P < 0.003). CONCLUSIONS: Sustained load shortens the ERP and the mean APD90, and at the same time increases dispersion of APD90 and prolongs activation times. These findings provide additional insight into the arrhythmogenic mechanisms of sustained mechanical load.
Authors:
M Zabel; S Portnoy; M R Franz
Related Documents :
2457459 - Time-dependent increase in left ventricular contractility following acute volume loadin...
23334909 - Nutraceuticals for treatment of high blood pressure values in patients with metabolic s...
6695779 - Left ventricular volumes and function during atrial pacing in coronary artery disease: ...
3578059 - Cardiac response to daily activities and exercise in normal subjects assessed by an amb...
7571389 - The effects of medetomidine on cardiac contractility in autonomically blocked dogs.
998479 - Effect of dextran loading on left ventricular performance in chronic obstructive pulmon...
10607179 - Non-invasive measurement of haemodynamics during sleep apnoea.
6940689 - Performance of neonatal ventilators: the effects of changes in resistance and compliance.
9639349 - Gas handling in the caecum of the horse.
Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  7     ISSN:  1045-3873     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  1996 Jan 
Date Detail:
Created Date:  1996-10-23     Completed Date:  1996-10-23     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  9-16     Citation Subset:  IM; S    
Affiliation:
Division of Clinical Pharmacology, Georgetown University Medical Center, Washington, DC, USA.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:
Action Potentials
Animals
Arrhythmias, Cardiac / etiology
Blood Pressure
Heart Conduction System / physiology*
Rabbits
Refractory Period, Electrophysiological
Stress, Mechanical
Ventricular Function*

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


Previous Document:  Diagnostic clues from the surface ECG to identify idiopathic (fascicular) ventricular tachycardia: c...
Next Document:  Altered pharmacologic responsiveness of reduced L-type calcium currents in myocytes surviving in the...