Can Only Severe Mitral Regurgitation Be Due to Rheumatic Heart Disease?
No, rheumatic heart disease (RHD) can cause mitral regurgitation (MR) of any severity—mild, moderate, or severe—not just severe MR. 1
RHD Causes the Full Spectrum of MR Severity
RHD produces MR across all grades of severity, from mild regurgitation detected only by Doppler echocardiography to severe regurgitation requiring surgical intervention. 1, 2
In clinical populations with RHD, mitral regurgitation is the most common valve abnormality, often presenting as isolated MR without stenosis or combined with varying degrees of mitral stenosis. 2, 3
Studies of stable clinic populations with documented rheumatic fever show that 84% had MR detectable by Doppler examination, with severity ranging from mild to severe. 3
Mechanisms of MR in RHD Vary by Severity and Stage
Acute Rheumatic Carditis (Typically Severe MR)
In acute rheumatic carditis, severe MR is the predominant presentation, caused by excessive leaflet tip motion from chordal elongation or rupture combined with annular dilatation. 1, 4
Surgical series demonstrate that 94% of patients with severe MR from active rheumatic carditis have mitral valve prolapse (defined as failure of leaflet coaptation with systolic displacement toward the left atrium), and 96% have annular dilatation. 4
Chordal elongation occurs in 90% of acute rheumatic carditis cases with severe MR, representing the primary mechanism of regurgitation in young patients. 4
Chronic RHD (Variable MR Severity)
Chronic RHD produces MR of any severity through progressive leaflet thickening, chordal thickening, restricted leaflet motion, and annular changes that evolve over years. 1, 2
In surgical pathology studies, chordal thickening is identified in 100% of severe mitral stenosis cases, 35-44% of predominant MR cases requiring surgery, and 37% of outpatients with RHD, demonstrating the variable severity spectrum. 1
Non-severe MR (mild or moderate) associated with any degree of mitral stenosis is common in RHD, and these patients can experience progression of MR over time at a rate of 2.4 per 100 patient-years. 2
Age-Related Patterns in RHD-Associated MR
Excessive leaflet tip motion and pure MR are most common in young rheumatic patients (age <35 years), while mitral stenosis becomes predominant beyond the third decade of life. 1
The World Heart Federation criteria specify that excessive leaflet motion as a morphological feature of RHD applies primarily to individuals aged <35 years, as older patients rarely present with this mechanism without associated leaflet restriction and thickening. 1
In pediatric populations, chordal rupture causing severe MR occurs predominantly in rheumatic carditis (present in 7-17% of patients undergoing rheumatic MV repair), whereas in adults, myxomatous degeneration is the most common cause. 1
Progression of MR in RHD
MR in RHD can progress from mild/moderate to severe over time, with predictors including patient age and left atrial volume enlargement. 2
The mechanism involves both primary valve pathology from rheumatic inflammation and secondary MR from left atrial remodeling due to chronic volume overload, creating a cycle of progressive regurgitation. 2
New-onset atrial fibrillation is associated with MR progression in RHD patients (HR 2.682), likely mediated through left atrial enlargement. 2
Clinical Implications for Diagnosis
Do not assume that mild or moderate MR excludes RHD as the etiology; the diagnosis requires assessment of valve morphology (leaflet thickening ≥3-5 mm depending on age, chordal thickening, restricted motion) rather than MR severity alone. 1
In patients with documented rheumatic fever and isolated systolic murmurs, 67% have pure MR and 80% demonstrate mitral valve prolapse on echocardiography, with only 4% showing mitral stenosis. 3
The presence of any degree of MR in a patient with prior rheumatic fever warrants comprehensive echocardiographic assessment to characterize valve morphology and determine if RHD is the underlying cause. 1, 3
Common Pitfall to Avoid
The critical error is assuming that only severe MR can be rheumatic in origin. RHD causes the full spectrum of MR severity, and mild or moderate MR with characteristic rheumatic valve morphology (thickening, restricted motion, commissural fusion) is diagnostic of RHD. 1, 2 The severity of MR reflects the stage and progression of disease, not whether RHD is present or absent.