Comparative study of vasodilators in an animal model of chronic volume overload caused by severe aortic regurgitation.
BACKGROUND
Aortic regurgitation (AR) is a disease of chronic left ventricular (LV) volume overload. Over time, AR will lead to LV dilatation, hypertrophy, and loss of function. There is currently no medical treatment proven effective to slow the evolution of this cardiomyopathy. Vasodilators were once thought to have protective effects, but recent publications have cast some doubts about their effectiveness. We hypothesized that drugs targeting the renin-angiotensin system should be more effective than those having no direct effect on the renin-angiotensin system.


RESULTS
We designed a protocol comparing the effects of 3 vasodilators in a rat AR model (n=9 to 11 animals per group). The effects of a 6-month treatment of (1) nifedipine, (2) captopril, or (3) losartan were compared in male AR rats. Sham-operated and untreated AR animals were used as controls. Nifedipine-treated animals displayed hemodynamics, LV dilatation, hypertrophy, and loss of function similar to those of the untreated group. Both captopril and losartan were effective in improving hemodynamics, slow LV dilatation, hypertrophy, and dysfunction. Gene expression analysis confirmed the lack of effects of the nifedipine treatment at the molecular level.


CONCLUSIONS
Using an animal model of severe AR, we found that vasodilators targeting the renin-angiotensin system were effective to slow the development of LV remodeling and to preserve LV function. As recently shown in the most recent human clinical trial, nifedipine was totally ineffective. Targeting the renin-angiotensin system seems a promising avenue in the treatment of this disease, and clinical trials should be carefully designed to re-evaluate the effectiveness of angiotensin I-converting enzyme inhibitors or angiotensin II receptor blockers in AR.
Plante
Eric
E
Groupe de Recherche sur les Valvulopathies, Centre de Recherche Hôpital Laval, Institut de cardiologie de Québec, Université Laval, Quebec, Canada.
Lachance
Dominic
D
Beaudoin
Jonathan
J
Champetier
Serge
S
Roussel
Elise
E
Arsenault
Marie
M
Couet
Jacques
J
D047228:Angiotensin II Type 1 Receptor Blockers / Q000008:administration & dosage / Q000627:therapeutic use; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use; D000818:Animals; D001022:Aortic Valve Insufficiency / Q000150:complications*; D002216:Captopril / Q000008:administration & dosage / Q000627:therapeutic use; D002311:Cardiomyopathy, Dilated / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D002908:Chronic Disease; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015150:Echocardiography, Doppler; D005500:Follow-Up Studies; D017379:Hypertrophy, Left Ventricular / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D019808:Losartan / Q000008:administration & dosage / Q000627:therapeutic use; D008297:Male; D009543:Nifedipine / Q000008:administration & dosage / Q000627:therapeutic use; D051381:Rats; D017208:Rats, Wistar; D012084:Renin-Angiotensin System / Q000187:drug effects; D016896:Treatment Outcome; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D016277:Ventricular Function, Left / Q000187:drug effects / Q000502:physiology*
D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D014665:Vasodilator Agents; D002216:Captopril; D009543:Nifedipine; D019808:Losartan