Right ventricular internal dimensions
RVID (basal, mid, length) · RV-focused apical 4-chamber, end-diastole; the 2025 guideline redefined where basal and mid are measured
Normal range & thresholds
2025 ASE graded severity, basal RV diameter:
Supporting limits: mid RVID ≤3.5 cm; RV longitudinal (base–apex) ≤8.3 cm; proximal RVOT (PLAX) ≤3.5 cm; distal RVOT ≤2.7 cm; RV free wall thickness ≤5 mm (subcostal, end-diastole) — above this is RV hypertrophy and implies chronic pressure load. RV end-diastolic area indexed and 3D RV volumes are more accurate than any linear dimension.[1,3]
2025 change: basal diameter is measured just below the tricuspid valve and mid diameter at ≈50% of RV inflow length, both parallel to the inflow axis — a redefinition from 2010, so old and new measurements are not interchangeable.[3]
| Basal RVID | Grade |
|---|---|
| ≤4.1 cm | Normal |
| 4.1–4.4 cm | Mildly dilated |
| >4.4–4.9 cm | Moderately dilated |
| >4.9 cm | Severely dilated |
2025 change: basal diameter is measured just below the tricuspid valve and mid diameter at ≈50% of RV inflow length, both parallel to the inflow axis — a redefinition from 2010, so old and new measurements are not interchangeable.[3]
Pathophysiology
The right ventricle is a thin-walled, crescentic, highly compliant volume pump built for a low-impedance circuit. It tolerates volume load remarkably well and pressure load remarkably badly: an acute rise in afterload above about 40 mmHg systolic causes it to dilate and fail within hours (acute cor pulmonale), while the same pressure applied over years produces hypertrophy first and dilatation only later. Dilatation shifts the septum leftward, which impairs LV filling by ventricular interdependence, reduces LV output and therefore RV coronary perfusion — the spiral that makes established RV failure so hard to reverse.[3,8]
Raised by
- Pressure load: pulmonary hypertension of any group, chronic thromboembolic disease, pulmonary stenosis, acute massive pulmonary embolism (acute dilatation with a thin wall)
- Volume load: severe tricuspid or pulmonary regurgitation (including late after tetralogy repair), atrial septal defect, anomalous pulmonary venous return, high-output states
- Myocardial: RV infarction, arrhythmogenic right ventricular cardiomyopathy, myocarditis, sarcoid, Uhl anomaly
- Ebstein anomaly (atrialised RV), carcinoid heart disease
- Endurance athlete’s heart — proportionate dilatation with normal function and normal strain
- Chronic lung disease with cor pulmonale; obstructive sleep apnoea; left heart disease (group 2, by far the commonest cause overall)
Lowered by
- Small body habitus — index to BSA
- Hypovolaemia; cardiac tamponade (RV diastolic collapse)
- Constrictive pericarditis
- Extrinsic compression, large pericardial or pleural effusion
- RV hypoplasia (congenital)
Technique & pitfalls
- Use a dedicated RV-focused apical 4-chamber view: rotate and angle to maximise RV size without foreshortening. A standard LV-focused 4-chamber view routinely under-measures the RV, and this is the commonest reason RV dilatation is missed.[3]
- Measure at end-diastole, parallel to the inflow axis, using the new 2025 landmarks.
- Always report the qualitative RV:LV area ratio as well — RV area > LV area in the 4-chamber view is severe dilatation and is quickly reproducible.
- Measure RV wall thickness subcostally in end-diastole, excluding trabeculae and the moderator band.
- Where the question is prognostic or surgical, move to 3D RV volumes or CMR — linear dimensions of a crescentic chamber are a crude surrogate.
Pseudo-change & artefact
- Off-axis and foreshortened views — both directions of error, and the RV is far more sensitive to plane than the LV.
- Rotation of the heart by chest deformity, pneumonectomy or a large left pleural effusion.
- Volume status: the RV is the more compliant chamber and its dimensions swing more with loading than the LV’s.
- Positive-pressure ventilation increases RV afterload and dimensions.
- Including the moderator band or trabeculae in the wall thickness measurement — a frequent cause of spurious RV hypertrophy.
- Comparing a 2025-definition measurement with a pre-2025 report.[3]
Treatment thresholds
- Atrial septal defect: right heart volume overload (dilated RA and RV) with Qp:Qs ≥1.5 is itself the class I indication for closure, irrespective of symptoms, provided PVR is not prohibitive.[25]
- Pulmonary regurgitation after tetralogy of Fallot repair: pulmonary valve replacement is indicated for symptoms, and considered in asymptomatic patients with progressive RV dilatation — the widely used CMR-derived thresholds are RV end-diastolic volume index ≥160 mL/m² or end-systolic volume index ≥80 mL/m², with echo used for surveillance and CMR for the decision.[25]
- Tricuspid regurgitation: progressive RV dilatation with preserved function supports intervening before the RV fails; severe RV dysfunction is an exclusion for transcatheter tricuspid therapy in the 2025 ESC/EACTS guidelines.[6]
- Acute pulmonary embolism: RV dilatation (RV/LV ratio >0.9–1.0) upgrades a normotensive patient to intermediate risk and, with a positive troponin, to intermediate-high risk — changing monitoring and the threshold for rescue reperfusion.[8]
- ARVC: RVOT dimensions and regional wall motion abnormality are formal major/minor criteria in the diagnostic Task Force criteria and feed the ICD decision.[14,38]
Next step
- Next: quantify RV function (TAPSE, S′, FAC, free-wall strain) — a dilated RV with normal function is a different clinical problem from a dilated failing RV.
- Then: estimate pulmonary pressures and pulmonary vascular resistance; look for the septal shift and the D-shaped LV that distinguish pressure from volume overload (systolic flattening = pressure; diastolic flattening = volume).
- Then: agitated saline for shunt, CT pulmonary angiography or V/Q for embolic disease, and CMR for RV volumes, ARVC and infiltration.
- Then: right heart catheterisation if pulmonary hypertension is suspected — echo cannot make the haemodynamic diagnosis, and the 2022 ESC/ERS definition (mean PAP >20 mmHg, PVR >2 WU) is invasive.[8]
Drugs
- Diuretics reduce RV volume load and are first-line in right heart failure.
- Pulmonary vasodilators (endothelin receptor antagonists, PDE-5 inhibitors, riociguat, prostacyclin analogues) reduce RV size over months in group 1 pulmonary hypertension — and are harmful in group 2 and much of group 3.[8]
- Anticoagulation and reperfusion in acute and chronic thromboembolic disease.
- Optimising left-sided filling pressures is the treatment of group 2 disease; treat the left heart, not the pulmonary artery.
- Avoid excessive fluid loading, which worsens interdependence and lowers LV output.
Reversibility
Substantially reversible if the load is relieved before the RV myocardium fails. After ASD closure the RV regresses markedly within 3–12 months, most completely in the young. After pulmonary endarterectomy for CTEPH, and after successful pulmonary vasodilator therapy in responders, RV dimensions and function improve substantially. After pulmonary valve replacement, RV volumes fall but normalise only when the pre-operative RVEDVi was below roughly 160 mL/m² — the reason that threshold exists. Once RV free-wall fibrosis and severe dysfunction are established, dilatation is essentially fixed.[8,25]