I’m guessing if I turned in an open-book qualifier response based entirely on about.com and wikipedia I’d probably fail, but I think these sorts of sites have an important role in the research: somewhere to start from. I’m using Freemind to organize what I find.
I’ve begun by searching wikipedia (found nothing) and then moved rapidly straight to Google, where I found a few appropriate results:
Cardiac resynchronization therapy (CRT) is a proven treatment for selected patients with heart failure-induced conduction disturbances and ventricular dyssynchrony. When used in combination with stable, optimal medical therapy, CRT is designed to reduce symptoms and improve cardiac function by restoring the mechanical sequence of ventricular activation and contraction.
Medtronic’s very brief and heavily product-focused page nevertheless has a neat animation of a failing heart before and after resynchronization therapy. Dr. Richard Fogoros gets a little more in-depth on About.com:
CRT uses uses a specialized pacemaker to re-coordinate the action of the right and left ventricles in patients with heart failure.
In approximately 30% of patients with heart failure, an abnormality in the heart’s electrical conducting system (called an “intraventricular conduction delay” or bundle branch block) causes the two ventricles to beat in an asynchronous fashion. That is, instead of beating simultaneously, the two ventricles beat slightly out of phase. This asynchrony greatly reduces the efficiency of the ventricles in patients with heart failure, whose hearts are already damaged.
CRT re-coordinates the beating of the two ventricles by pacing both ventricles simultaneously. This differs from typical pacemakers, which pace only the right ventricle.
I was looking for information on clinical indications for administration of CRT. Apparently the roots of the problem are in bundle branch block. I’d say I’m off to a pretty good start!