Mitral Regurgitation and Dyspnea

Pathophysiology

Mitral regurgitation creates volume overload on the left ventricle, leading to left atrial enlargement and pulmonary hypertension even when LVEF remains normal (>60%) 1
The regurgitant flow into the left atrium increases left atrial pressure, leading to pulmonary venous congestion and symptoms of dyspnea 2
Chronic severe MR imposes a pure volume overload on the left ventricle, resulting in eccentric hypertrophy and LV dilation, which can occur before LVEF decreases 1
In patients with MR, LVEF may appear "normal" or even supranormal due to the reduced afterload, masking early myocardial dysfunction 1

The American College of Cardiology and American Heart Association recognize that patients with severe MR can be symptomatic, including dyspnea, despite having preserved LVEF (>60%) 3, 4
The American College of Cardiology and American Heart Association recommend surgery for symptomatic patients with chronic severe MR even when LVEF is preserved (>60%), acknowledging that symptoms like dyspnea can occur before LVEF declines 4
The American College of Cardiology and American Heart Association suggest that mitral valve repair is reasonable for asymptomatic patients with chronic severe MR and preserved LV function who have pulmonary hypertension 3
The European Society of Cardiology recommends surgery for symptomatic patients with severe primary MR who have LVEF >30%, recognizing that symptoms can occur at any LVEF level 5

The American College of Cardiology and American Heart Association recommend mitral valve surgery for symptomatic patients with chronic severe MR and LVEF >30%, acknowledging that symptoms like dyspnea warrant intervention regardless of LVEF 4
The American Heart Association states that the presence of symptoms, including dyspnea, in patients with severe MR is a Class I indication for surgical intervention, regardless of LVEF 6
The American College of Cardiology and American Heart Association suggest echocardiographic follow-up every 6-12 months for asymptomatic patients with severe MR to monitor for development of symptoms or LV dysfunction 5

LVEF may be misleading in MR as it represents a load-dependent measure that can mask early myocardial dysfunction 1
A "normal" LVEF in the setting of MR may actually represent early dysfunction; guidelines suggest that LVEF should ideally be >64% in severe MR 7
The severity of MR can be dynamic and change with loading conditions, exercise, or ischemia, so symptoms may worsen during physical activity even when resting LVEF is preserved 1
The concept of "mitral regurgitation begets mitral regurgitation" suggests that even with preserved LVEF, ongoing MR can lead to progressive LV dilation and worsening MR in a perpetual cycle 7