Right Ventricular Infarct question

[AZ_Ogre]

Can someone give a good explanation of the reasoning behind maintaining or increasing preload in a patient in RVI. I know you shouldn't use nitro or morphine due to the decrease in preload and hypotensive factor in this type of MI. I just don't understand why. If you could tell me any other differences in treatment for this compared to other MIs I would appreciate it.

Thanks in advance.

[sirI, MSN, APRN, NP]

hello, az ogre,

good links here:

http://www.emedicine.com/med/topic2039.htm

http://patients.uptodate.com/topic.asp?file=chd/2454[/url]

[JiffyGriff]

Easy way to think of preload: think of a rubber band, the further you stretch it the harder and faster it snaps back. So: if you increase preload you increase the pressure exerted on the right ventricular walls which in turn increases the force with which the right ventricle contracts and causes it to eject more blood. In right sided heart failure blood is backed up into the right ventricle, right atrium, and the venous system before the right atrium.........so increasing the preload helps expel more of that fluid and decrease that congestion. Can't increase the preload too much though because of the Frank-Starling mechanism, the more you stretch something the less elasticity it will eventually have: the right ventricle will "stretch out" and be less effective in contracting and ejecting. According to that law, it's probably better idea to maintain the preload and use a positive inotropic drug (Dig), ACE Inhibitors and beta blockers to increase contractility of the heart causing more efficient ejection and reducing afterload and workload of the heart. Also would use a diuretic to manage complications of fluid retention.......remember the whole renin-angiotensin jargon?