Effect of Mitral Incompetence on Cardiac Ejection Fraction
In mitral incompetence (mitral regurgitation), the ejection fraction is typically decreased, not increased, making option (d) the correct answer.
Understanding Ejection Fraction in Mitral Regurgitation
- Normal ejection fraction ranges from 50-70%, not 45% as suggested in option (a) 1
- In mitral regurgitation (MR), the left ventricle ejects blood in two directions - forward into the aorta and backward into the left atrium, which affects the true ejection fraction 2
- The ACC/AHA guidelines specifically note that in patients with mitral regurgitation, an ejection fraction <60% is considered abnormal and indicates left ventricular systolic dysfunction 2
Pathophysiology of Decreased EF in Mitral Regurgitation
- Long-standing volume overload from mitral regurgitation leads to progressive left ventricular dilation and eventually to irreversible left ventricular dysfunction 2
- The concept of "mitral regurgitation begets mitral regurgitation" describes how initial MR causes LV dilatation, which increases stress on the mitral apparatus, causing further valve damage, more severe MR, and further LV dilatation 2
- This perpetual cycle eventually leads to decreased ejection fraction as the heart fails to maintain compensatory mechanisms 2
Clinical Significance and Management Implications
- In patients with mitral regurgitation, an ejection fraction ≤60% or LVESD ≥40 mm indicates that LV systolic dysfunction has already developed 2
- ACC/AHA guidelines recommend mitral valve surgery for asymptomatic patients with chronic severe primary MR and LV dysfunction (LVEF 30% to 60% and/or LVESD ≥40 mm) 2
- For LV function to return to normal after mitral valve repair, research suggests the LVEF should be >64% and LVESD <37 mm before surgery 2
Ejection Fraction Changes After Mitral Valve Intervention
- Surgical correction of mitral regurgitation typically results in an early decrease in ejection fraction, particularly in symptomatic patients with increased left heart dimensions 3
- The magnitude of early decline in ejection fraction is similar in patients who undergo either mitral valve repair or replacement 3
- Patterns of short and long-term changes in post-operative ejection fraction differ according to pre-operative ejection fraction and left ventricular end-systolic diameter values 4
Comparison with Other Valvular Conditions
- In mitral stenosis (option c), ejection fraction is typically preserved or normal, not increased 2
- In ventricular septal defect (option e), ejection fraction may appear increased due to left-to-right shunting, but this represents a different pathophysiology than valvular disease 2
Clinical Monitoring and Intervention Timing
- When longitudinal follow-up demonstrates a progressive decrease of ejection fraction toward 60% or a progressive increase in LVESD approaching 40 mm in patients with MR, intervention should be considered 2
- Patients with severe MR who develop an EF ≤60% have already developed LV systolic dysfunction, making early intervention critical before these thresholds are reached 2