Differential Diagnosis for Dilated Right Ventricle and Right Atrium
The most critical first step is to systematically exclude life-threatening and treatable causes: congenital heart disease with RV volume overload (particularly atrial septal defect), pulmonary hypertension causing RV pressure overload, and arrhythmogenic cardiomyopathy (AC), as these have vastly different prognoses and management strategies that directly impact mortality. 1
Algorithmic Approach to Diagnosis
Step 1: Assess for Volume Overload Causes
Congenital heart disease is a critical consideration that must be ruled out first:
- Atrial septal defect (ASD) and anomalous venous drainage are the primary culprits 1
- Look for: left-to-right shunt on color Doppler, paradoxical septal motion, dilated pulmonary arteries
- Key distinguishing feature: In congenital lesions, RV dilatation typically involves the inflow tract with balanced biventricular enlargement 1
- Transoesophageal echocardiography or right heart catheterization may be necessary to detect shunts 1
Step 2: Evaluate for Pressure Overload
Pulmonary hypertension presents with specific patterns:
- Initially: RV hypertrophy predominates
- Advanced disease: RV dilatation becomes more prominent than hypertrophy (maladaptive remodeling) 2
- Ominous sign: Declining pulmonary artery pressure despite persistently elevated pulmonary vascular resistance indicates decompensation 3
- Measure TAPSE (tricuspid annular plane systolic excursion): <16 mm suggests RV dysfunction 3
Step 3: Consider Primary RV Myocardial Disease
Arrhythmogenic cardiomyopathy (AC) is the most important primary RV disease to identify due to sudden death risk:
Hallmark features that distinguish AC 1:
- Regional RV wall motion abnormalities (hypokinesia, dyskinesia, aneurysms)
- RV thinning and bulging, particularly at the RVOT, apex, or inferior wall
- Fibro-fatty replacement on cardiac MRI (subepicardial distribution)
- T-wave inversions in precordial leads (V1-V3)
- Ventricular arrhythmias with LBBB morphology
Critical distinction from benign conditions:
- Athlete's heart: RV dilatation involves inflow tract with balanced LV enlargement, normal TAPSE, normal strain values, no regional wall motion abnormalities 1
- RVOT-VT: Structurally normal ventricles (though frequent PVCs can cause remodeling), no fibro-fatty replacement, no T-wave inversions, >9000 PVCs/24h without severe structural changes 1
Step 4: Exclude Mimics of AC
Several conditions can present similarly and must be differentiated:
Cardiac sarcoidosis 1:
- Mediastinal lymphadenopathy
- LV septal scar (late gadolinium enhancement)
- Significant LV dysfunction
- Intense PET-FDG uptake in myocardium
- Conduction disturbances
Right ventricular endomyocardial fibrosis 4, 5:
- Obliteration of RV apex
- Restrictive physiology with prominent 'y-descent' in JVP
- May present with "caterpillar-like" RV aneurysm 5
- No eosinophilia required
Myocarditis 1:
- Endomyocardial biopsy remains gold standard (though low sensitivity)
- Acute presentation with inflammatory markers
Systemic sclerosis 1:
- Multiorgan involvement differentiates from AC
- Regional wall motion abnormalities can occur independent of pulmonary hypertension
Step 5: Consider Biventricular Involvement
Left ventricular involvement changes the differential 3, 6:
- HF with reduced EF: RV dilatation occurs in 48% of HFrEF patients, associated with 2.4-fold increased mortality 3
- Biventricular AC: Left-dominant or biventricular forms exist with posterolateral LV involvement, subepicardial fibro-fatty replacement on CMR 1
- Idiopathic isolated RV cardiomyopathy: Diagnosis of exclusion after ruling out all other causes 7
Essential Diagnostic Workup
Mandatory investigations:
- ECG: T-wave inversions V1-V3, epsilon waves, conduction abnormalities
- Echocardiography with strain imaging: TAPSE, RV free wall strain, regional wall motion abnormalities
- Cardiac MRI: Tissue characterization for fibro-fatty replacement, late gadolinium enhancement pattern (subepicardial favors AC) 1
- Holter monitoring: Arrhythmia burden and morphology
- Family history: Critical for AC diagnosis
Additional tests when indicated:
- PET-FDG if sarcoidosis suspected 1
- Right heart catheterization for shunt detection or hemodynamic assessment 1
- Genetic testing for AC-related mutations 1
- Endomyocardial biopsy in selected cases 1
Critical Pitfalls to Avoid
- Do not dismiss RV dilatation in athletes without CMR: CMR alterations alone without ECG/Holter abnormalities favor physiologic adaptation, but AC must be excluded 1
- Do not overlook congenital heart disease in adults: ASD can present late and is easily treatable 1
- Declining pulmonary pressures are not reassuring: This indicates decompensation in pulmonary hypertension 3
- Biventricular involvement does not exclude AC: Left-dominant forms exist and carry similar sudden death risk 1