Conditions: Mitral Regurgitation
Keywords: Chronic MR Volume Overload Beta-1 receptor blocker LV remodelling, LV dimensions LV systolic function LV diastolic dysfunction Cardiac MRI
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 38
Healthy volunteers: yes

Brief summary:
The investigators hypothesize that beta-1 receptor blockade (ß1-RB) attenuates extracellular matrix (ECM) degradation and progressive adverse Left Ventricular (LV) remodeling and failure in the volume overload of mitral regurgitation (MR). Patients without coronary artery disease and moderate MR, as assessed by color/flow Doppler echocardiography, will be randomized to ß1-RB vs. placebo to address the following aims:

\*Aim 1: Establish whether ß1-RB attenuates adverse LV remodeling compared to placebo in patients with non-surgical, chronic MR. Using 3-dimensional magnetic resonance imaging (MRI) and tissue tagging, LV function and geometry will be assessed at baseline and every 6 months for up to 2 years.

Aim 2: Determine whether indices of inflammation correlate with degree of LV remodeling and whether ß1-RB decrease indices of inflammation and collagen turnover. At the time of MRI, blood samples for collagen breakdown products, matrix metalloproteinase (MMP) activity, and markers of excess production of reactive inflammatory species (RIS) will be obtained and related to changes in LV remodeling defined by serial 3-dimensional MRI and tissue tagging.

Detailed description:
In Western society, the most common causes of chronic mitral regurgitation (MR) are ischemic heart disease and myxomatous degeneration of the valve, resulting in prolapse, ruptured chordae or partial flail leaflet. Current indications for surgery are only for patients with severe MR and either notable symptoms or overt Left Ventricular (LV) dysfunction (ejection fraction \< 60%, end-systolic diameter \> 40 mm). Therefore, despite the availability of surgery, most patients with MR of moderate severity are not immediate candidates for surgery, warranting analysis of potential beneficial effects of medical treatment. Chronic therapy with vasodilators reduces LV wall stress and thereby delays the need for valve replacement in aortic regurgitation; however, no such data are currently available in patients with chronic MR using standard vasodilators or agents that block the renin angiotensin system (RAS).

In a clinically-relevant dog model of MR, the investigators have shown increased LV ACE and chymase expression, increased LV angiotensin II but, as opposed to pressure overload, there was an absence of fibrosis with net extracellular matrix (ECM) degradation and activation of matrix metalloproteinases (MMPs). However, blockade of the RAS does not improve (and may actually exacerbate) LV remodeling in MR. Interestingly, the investigators and others have shown that ß1-receptor blockade (ß1-RB) is more effective than RAS blockade in attenuating progressive LV remodeling and ECM degradation in MR. Moreover, increased sympathetic drive and inflammation has been identified in patients with chronic MR. ß1-RB reduced plasma markers of inflammation in patients with heart failure and resulted in substantial reverse LV remodeling in patients with heart failure. Taken together, activation of the adrenergic nervous system early in the course of volume overload contributes to increased production of reactive inflammatory species (RIS) and that one mechanism underlying the salutary effects of ß1-blockade may relate to attenuation of myocardial formation of RIS with subsequent beneficial effects on MMP activation and ECM and LV remodeling and function.

Arms:
arm 1: beta 1 receptor blockade; generic name metoprolol succinate arm 2: Pill that looks like Toprol XL but does not have the active ingredients

Interventions: intervention 1: metoprolol succinate (Toprol XL) intervention 2: Placebo
Intervention descriptions: intervention 1: Toprol XL 100 mg once a day for 2 years intervention 2: Placebo 100 mg once a day for 2 years

Protocol document: