Natural History of Mitral Regurgitation

In this section, I shall be covering unmodified natural history of rheumatic and flail mitral leaflet regurgitation. Modified natural history of MR( after surgery/percutaneous intervention)and MR secondary to mitral valve prolapse shall be discussed later.

A. Stages of Chronic Primary Mitral Regurgitation

B. Natural History of Primary MR

(i) Untreated severe primary MR

Clinical Outcome of Severe MR

1. 90% of patients with severe MR due to flail leaflet were dead or required surgery at 10 years follow up
2. 30 % incidence of atrial fibrillation which was associated with poor survival
3. 63 % incidence of heart failure associated with poor survival
4. Mortality rate was 6.3 %
5. 20 % patients receiving medical management died
6. 69 % deaths were from cardiac causes

7. Patients with severe MR and NYHA I or II who did not undergo surgery had a mortality rate of 4.1 % compared to 34 % with those with NYHA III/IV symptoms

8. Once the heart failure developed, prognosis was worse and 5 year survival less than 20 %

9. Outcomes depends on initial symptoms and presence or absence of LV dysfunction

10. When stratified according to Ejection fraction, patients with EF < 60 percent had markedly lower survival compared to EF > 60 %

11. Sudden death, a catastrophic event, accounts for approximately one quarter
of deaths during medical treatment

12. The determinants of higher rates of sudden death include severe symptoms and subnormal LVEF, but most sudden deaths occur in patients with no or minimal symptoms and normal LV function

13. The rate of sudden death is 1.8% per year overall and even in patients without risk
factors, is 0.8% per year.

Progression of MR

1. MR is a progressive disease with an average increase of 7.5 ml/year in regurgitant volume and of 5.9mm2/year for the effective regurgitant orifice.

2. The determinants of progression are anatomic changes, with more rapid progression in patients with MVP (particularly with development of new flail leaflet) and with enlarging mitral annulus.

3. Half of patients manifest notable progression, but 11% evidence spontaneous regression of MR related to improved loading conditions.

LV Dysfunction

1. LV dysfunction is a major source of poor outcome under conservative management or post-operatively. LV dysfunction is the most potent predictor of late death after surgery.

2. The LVEF decreases significantly, by approximately 10%, immediately after
surgical correction of MR. Therefore, despite symptomatic improvement, postoperative
LV dysfunction (LVEF < 50%) is frequent, occurring in close to one third of the patients successfully operated for organic MR.

3. Pre-operative LVEF is the best predictor of long-term mortality under conservative
management and after surgery , of congestive heart failure and of post-operative residual LV function. The end-systolic dimension is also a significant predictor of the post-operative LV function

(ii) Natural History of asymptomatic moderate to severe MR

1. In asymptomatic patients with severe MR, rate of progression to symptoms , PAH, LV dysfunction or AF is 30-40 % at 5 years
2. Regurgitation tends to progress more rapidly in patients with connective tissue diseases such as marfans than those with severe MR of rheumatic/myxomatous origin.
3. Annual mortality less than 1 %( 5 % mortality at 7 years)

Determinants of outcomes in unoperated patients

Age

Symptoms(NYHA class)

Pulmonary hypertension

LV filling pressures

AV-O2 difference

LV ejection fraction

LV end diastolic volume

C. Natural History of Secondary MR

1. Associated with poor outcomes compared with primary MR
2. Both forms of secondary MR, ischemic and non-ischemic are associated with adverse prognosis
3. Poor outcomes in ischemic MR occur at smaller ERO(0.2 cm 2) compared with primary MR
4. In non-ischemic secondary MR, any degree of MR is a poor prognostic sign likely because it reflects poor underlying ventricular remodeling.
5. The severity of tricuspid regurgitation was also a predictor of mortality and often occurred with severe MR
6. Right ventricular (RV) dysfunction may be a predictor of poor outcome among patients with secondary MR
7. Ischemic MR following MI is associated with increased mortality as well as risk of development of HF. Ischemic MR is also an important predictor of the development of HF, even in patients with a normal LVEF at the time of the MI.