Causes of Ruptured Mitral Valve Chordae Tendineae
Myxomatous degeneration (including mitral valve prolapse) is the most common cause of ruptured chordae tendineae in contemporary practice, accounting for approximately 44-56% of cases, followed by infective endocarditis (37%), with rheumatic heart disease now representing only 25% of cases. 1
Primary (Degenerative) Causes
Myxomatous degeneration represents the dominant etiology and is likely underestimated since microscopic evaluation is not routinely performed 1. This includes:
- Mitral valve prolapse (MVP) - accounts for 44.5% of cases since 1985, though may be overestimated due to detection criteria and misinterpretation of leaflet override versus true prolapse 1
- Primary myxomatous degeneration - 11.7% when identified separately, but is the underlying substrate for most MVP cases 1
- "Primary" or spontaneous rupture - remains significant at 51.2% overall, occurring in apparently healthy subjects with no identifiable predisposing factors 1. This may represent undetected myxomatous changes or mechanical fatigue failure 2
The guideline evidence confirms that flail leaflets with torn chords are associated with adverse prognosis and represent Type II (excessive) leaflet motion in Carpentier's classification 3.
Infectious Causes
Infective endocarditis - particularly subacute bacterial endocarditis (SBE):
- Dropped from 54.4% pre-1985 to 37.4% since 1985 1
- More common in younger patients (mean age 57 years) 4
- Frequently coexists with underlying MVP, suggesting MVP predisposes to both endocarditis and subsequent rupture 4
- May be overestimated as it can be a consequence rather than primary cause of rupture 1
Rheumatic and Inflammatory
Rheumatic heart disease (RHD):
- Declined sharply from 42.1% pre-1985 to 24.8% since 1985 1
- Expected to continue declining following decreased rheumatic fever incidence 1
- Typically causes Type IIIA leaflet restriction (both systolic and diastolic) rather than rupture, but can occur 3
Other inflammatory conditions mentioned in guidelines include radiation-induced or drug-induced valvular injury 3, 5.
Structural Heart Disease Associations
Hypertrophic cardiomyopathy (HCM):
- Occurs in approximately 1% of HCM patients 6
- Affects older patients (68-71 years) with obstructive disease 6
- Almost exclusively involves the posterior leaflet 6, 7
- Associated with systolic anterior motion and anterior leaflet elongation 6
- Histology shows extensive myxomatous degeneration as the substrate 6
- Resting LVOT obstruction typically disappears after rupture 6
Calcific aortic stenosis:
- Represents 8% of surgical chordal rupture cases 8
- Mean age 68 years, often with extensive mitral annular calcification 8
- Ventricular anatomic and hemodynamic alterations in aortic stenosis may contribute to rupture 8
Ischemic heart disease - previously considered significant but proved episodic or non-causative 1. However, patients with long-standing secondary MR from ischemic disease can subsequently rupture a chord 3.
Traumatic
Blunt chest trauma:
- Rare cause, previously considered significant but now recognized as episodic 1
- Can occur days to weeks after injury 9
- Difficult to diagnose as physical exam, ECG, and cardiac enzymes are neither sensitive nor specific 9
Rare and Miscellaneous Causes
The following have been described but are not significant contributors to overall incidence 1:
- Generalized connective tissue disorders (Marfan syndrome, Ehlers-Danlos)
- Iatrogenic valve damage (including from pacemaker leads) 5
- Carcinoid syndrome 5
- Endomyocardial fibrosis 5
- Congenital abnormalities 5
Important Clinical Pitfalls
Do not confuse anterior leaflet override with prolapse - in Type IIIB motion with severe posterior leaflet tethering, the anterior leaflet may override but does not move above the annular plane; this is not prolapse or mixed-etiology MR 3.
Mixed pathology occurs frequently - untreated primary MR can cause LV dilation where both prolapse and tethering coexist; patients with secondary MR from AF or ischemia can subsequently rupture a chord 3.
Age matters for differential diagnosis - primary rupture patients are significantly older (mean 67 years) than endocarditis patients (mean 57 years) 4.
Posterior leaflet involvement predominates - 75% of cases involve the posterior cusp, with atrial fibrillation frequently present 4.