This is the podcast Surgery I see rounds. My name's Jeff Guy. Today is Saturday, March the 9th, 2008.

The topic that I want to talk about today is something that gets mentioned frequently on rounds, and I'm not exactly sure that everyone who's rounding with us really has an understanding of the importance of this topic, and that is drug-induced QT prolongation.

You may also hear this sometimes called as prolonged QT syndrome.

Drug-induced long QT syndrome is typically characterized by an acquired QT interval prolongation,

which results in the increased likelihood

of a patient developing the cardiac arrhythmia Torsades-Depants. For those of you don't know

what Torsades is, Torsades is a wide complex arrhythmia that often looks like a coarse ventricular fibrillation.

And it appears that these wide QRs complexes twists around a central line, almost like in a sinusoidal type fashion.

This torsauze de Ponce is usually self-limited but can degenerate into ventricular fibrillation and obviously sudden cardiac death.

A variety of medications and many of these are common medications have been implicated in drug-induced long QT syndrome.

And in fact, QT prolongation and the development of torticodes are the most common reasons drugs are restricted or removed from the market within the United States.

And the reference for that is Lasser and colleagues in the Journal of the American Medical Association in the year 2002.

Let's start our discussion by actually detailing what is a QT interval and how is it measured.

When one looks at an EKG tracing, the QT interval is that interval that really measures

from the point where the ventricular is depolarized and through the point where the ventricle is repolarized.

And if you're looking at an EKG tracing, this is from the point of the start of the QRS complex

to the end of the T wave.

Now in the normal individual, the QT intervals will vary for a variety of reasons.

We can see variations throughout the day, secondary to diurninal effects.

Electrolite imbalances may cause changes in the QT interval, onomic fluctuations,

and even the way the EKG is acquired, the way and the technician places the leads.

QT intervals can be shortened with increasing heart rate and tachycardia and can be lengthened with predacardia.

...