16. Valvular Heart Diseases, Arrhythmic Mitral Valve Prolapse, and MAD Syndrome
Valvular lesions generate chronic chamber loading patterns, but specific valvular pathologies—particularly Arrhythmic Mitral Valve Prolapse—constitute under-recognized triggers for malignant ventricular arrhythmias.
1. Arrhythmic Mitral Valve Prolapse (MVP) & Mitral Annular Disjunction (MAD)
| Clinical Entity | Pathophysiology & Structural Hallmark | Electrocardiographic Signatures | Malignant Arrhythmia Substrate |
|---|---|---|---|
| Arrhythmic MVP Syndrome (Barlow's Disease) | Myxomatous degeneration of bileaflet mitral valve with systolic billowing into left atrium. | T-Wave Inversions in Inferior Leads (II, III, aVF); frequent polymorphic PVCs with papillary muscle / fascicular morphology. | Mechanical traction on papillary muscles and inferobasal myocardium generating stretch-induced automaticity and reentry. |
| Mitral Annular Disjunction (MAD) | Detachment of the mitral annulus from the basal LV myocardium ($>5-10\text{ mm}$ during systole). | High PVC burden; T-wave alternans; prolonged $QTc$. | "Pickelhaube Sign" on tissue Doppler (high-velocity systolic spike $>16\text{ cm/s}$ at lateral annulus); late gadolinium enhancement (LGE) at papillary muscles. |
2. Electrocardiographic Manifestations of Classic Valvular Lesions
- Severe Aortic Stenosis: Severe LVH with strain (ST depression and T-wave inversion in $V_5-V_6$), Left Atrial Enlargement.
- Post-TAVR Conduction Monitoring: New-onset Left Bundle Branch Block (LBBB) occurs in $10-30\%$ of patients due to direct mechanical compression of the His bundle/left bundle by the prosthetic frame $\to$ high risk of progression to Complete Heart Block.
- Severe Mitral Stenosis: P-mitrale (Left Atrial Enlargement), Right Axis Deviation, Right Ventricular Hypertrophy (from secondary reactive pulmonary hypertension).
3. Evidence-Based Management Protocols
- Arrhythmic MVP & MAD:
- Medical Therapy: Beta-Blockers (first-line for suppressing ventricular ectopy).
- Risk Stratification: Patients with unexplained syncope, bileaflet MVP, MAD, inferobasal LGE on CMR, and complex ventricular arrhythmias warrant ICD Implantation.
- Catheter Ablation: RF ablation of trigger PVCs originating from the anterolateral or posteromedial papillary muscles.