Effect of Beta Blockade on Left Ventricular Remodeling and Function in Moderate to Severe Asymptomatic Aortic Regurgitation
Effect of Beta Blockade on Left Ventricular Remodeling and Function in Moderate to Severe Asymptomatic Aortic Regurgitation
The primary objective of this study is to evaluate the effect of beta-blocker on left
 ventricular (LV) remodeling in asymptomatic patients with moderate to severe aortic
 regurgitation.
The left ventricle responds to the volume load of chronic aortic regurgitation (AR) with a
 series of compensatory mechanisms, including an increase in end-diastolic volume, an increase
 in chamber compliance that accommodates the increased volume without an increase in filling
 pressures, and a combination of eccentric and concentric hypertrophy. The greater diastolic
 volume permits the ventricle to eject a large total stroke volume to maintain forward stroke
 volume in the normal range. This is accomplished through rearrangement of myocardial fibers
 with the addition of new sarcomeres and development of eccentric LV hypertrophy. As a
 consequence left ventricular ejection fraction will remain in the normal range.

 The clinical course of chronic aortic regurgitation is characterized by a prolonged phase of
 stability during which the left ventricle adapts to the volume overload. Eventually
 myocardial failure ensues through a series of complex events that include changes in myocyte
 phenotype due to re-expression of fetal genes, cellular apoptosis alteration in the
 expression and function of contractile proteins and changes in the extracellular matrix.

 The role of long-term vasodilator therapy in the care of asymptomatic patients with severe
 aortic regurgitation is controversial. Vasodilator therapy has been used to reduce the
 regurgitant volume, afterload, left ventricular volumes, and wall stress in an effort to
 preserve left ventricular function and reduce left ventricular mass. Thus time to surgical
 intervention has been found to be delayed by calcium antagonists, ACE-inhibitors and
 hydralazine, while a more recent study did not find any effect of nifedipine or enalapril on
 time to surgery or left ventricular volume and function.

 The decision to recommend operative intervention to the asymptomatic patient with chronic,
 severe aortic regurgitation (AR) is very difficult because aortic valve replacement (AVR)
 continues to entail immediate risk, and biologic and mechanical valves still have problems
 resulting in significant morbidity and mortality. On the other hand, the mortality rate in
 asymptomatic patients with AR is very low, and surgery does not improve the quality of life.
 Thus, the indication in asymptomatic patients must be delayed until changes occur that will
 predict an increased risk of operative or long-term death after AVR. At present indication
 for aortic valve replacement is development of symptoms, an increase in left ventricular
 volume or a decline in left ventricular function.
Inclusion Criteria:

 -  Moderate to severe aortic valve insufficiency

 -  Asymptomatic

 Exclusion Criteria:

 -  Arrhythmia

 -  Other severe valve disease