In patients not undergoing beta-blocker therapy, large AAA expand at a significantly greater rate than smaller AAA. Large aneurysms that rupture show more rapid expansion than those AAA that do not rupture. We have demonstrated a significantly reduced rate of expansion of large AAA in patients receiving beta-blockade.
Propranolol has been suggested to slow aortic aneurysm (AAA) expansion by a mechanism independent of simple blood pressure (BP) reduction. To investigate this hypothesis, we designed a series of experiments to examine the effects of hypertension and propranolol upon AAA expansion. Using an established animal model, we induced AAA in normotensive and genetically hypertensive rats by perfusion of the isolated infrarenal aorta with elastase for two hours. Systolic tail BP was monitored with a plethysmograph. AAA size was measured directly with a micrometer on postoperative days 7 and 14. All data are expressed as the mean +/- standard deviation (SD). BP (mmHg) was significantly higher in hypertensive rats: 164 +/- 15 versus 119 +/- 7 (p < 0.001). AAA were also significantly larger in hypertensive rats with a mean expansion rate (mm/day) nearly twice that of normotensive animals: 0.13 +/- 0.09 versus 0.07 +/- 0.03. In a second series of animals, propranolol treatment was compared to placebo. In those animals, hypertensive propranolol-treated rats had significantly smaller AAA than placebo-treated controls (p < 0.05). There was no difference in normotensive animals but these rats had an unexplained paradoxical rise in BP with treatment. In this model, hypertension increases the expansion rate of AAA. Propranolol reduced the size of AAA in hypertensive animals, at least in part because of a decrease in BP. Other possible mechanisms of propranolol's action may be operative and require further study.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.