Class 1C Antiarrhythmics do they affect action potential duration? - USMLE Forums
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Old 02-16-2011
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Drug Class 1C Antiarrhythmics do they affect action potential duration?

From Kaplan I learned that class 1C do not change Action Potential duration.
BUT I just read this q in UW which says class 1A, 1C and class 3 all increase QT interval.

Any comments?
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Old 02-16-2011
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Class 1A there is increase of both (QT & AP).

Class 1B there is decreased AP only.

Class 1C there is no effect on AP.

Kaplan is right (FA Agrees), what UW is saying is that AP will not correlate with QT intervals..
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Old 02-17-2011
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Quote:
Originally Posted by patelMD View Post
Class 1A there is increase of both (QT & AP).

Class 1B there is decreased AP only.

Class 1C there is no effect on AP.

Kaplan is right (FA Agrees), what UW is saying is that AP will not correlate with QT intervals..
i do not understand how APD do not correlates with QT interval.
what is QT interval exactly? it is ventricular contraction .what does action potential durartion mean? is not QT INTERVAL a part of APD?
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Old 02-17-2011
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Quote:
Originally Posted by hana View Post
i do not understand how APD do not correlates with QT interval.
what is QT interval exactly? it is ventricular contraction .what does action potential durartion mean? is not QT INTERVAL a part of APD?
When its not alike / part of it.. then its called an arrhythmia! You got it
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Old 03-23-2011
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QT interval means ventricular refractoriness. i think it corresponds to ERP ( effective refractory period) and action potion duration is 'approximately' equal to ERP..
APD= ERP+ RRP

I hope i am right...
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Cardiovascular-, Pharmacology-

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