Linked Life Data

9299203

Source:http://linkedlifedata.com/resource/pubmed/id/9299203

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
5
pubmed:dateCreated
1997-11-24
pubmed:abstractText
The inadequacy of the QT interval to shorten following heart rate increase is a feature of the inherited long QT syndrome and may have a role in the genesis of the typical arrhythmias associated with this syndrome (torsade des pointes). The aim of our study was to evaluate whether drugs that prolong the QT interval, such as amiodarone and D-sotalol, may also impair the ability of the QT interval to adapt to sudden heart rate changes. Experiments were carried out on isolated perfused guinea pig hearts (Langendorff preparation). Driving frequency was changed, in steps, every two minutes (Hz: 2.5-3-2.5-3.75-2.5-5-2.5), while epicardial ECG was continuously recorded on magnetic tape. QT interval was automatically measured by means of a beat-by-beat analysis program. D-sotalol was added to the perfusion medium at a concentration of 4 micrograms ml-1, while amiodarone was administered, before in vitro evaluation, for seven days (50 mg kg-1 per day, intraperitoneally). In control experiments two phases of QT adaptation were identified: an abrupt QT shortening at the first beat after frequency change (QT1), followed by a gradual, exponential QT shortening that reached a new steady state in about 1 min (half life: 13 sec). The electrical restitution curve (the relation between QT1 and the corresponding diastolic interval) had a rate constant of 57 +/- 8 ms. Neither drug changed the slow component of QT adaptation. However, both drugs increased the ability of QT to shorten upon premature stimulation: D-sotalol by increasing the rate constant of the restitution curve and amiodarone by decreasing the y-intercept. Our results indicate that D-sotalol and amiodarone do not impair QT shortening during tachycardia but, on the contrary, they may favour QT adaptation, thus reducing the likelihood of the potentially lethal 'R on T phenomenon'. This may be an additional mechanism by which these drugs can exert their antifibrillatory action.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
1043-6618
pubmed:author
pubmed:issnType
Print
pubmed:volume
35
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
409-16
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Adaptation of the QT interval to heart rate changes in isolated perfused guinea pig heart: influence of amiodarone and D-sotalol.
pubmed:affiliation
Department of Pharmacology, University of Padova, Italy.
pubmed:publicationType
Journal Article, In Vitro, Research Support, Non-U.S. Gov't