What is a normal right ventricular internal diameter at diastole (RVIDd) on a Transthoracic Echocardiogram (TTE)?

Normal Right Ventricular Internal Diameter at Diastole (RVIDd) on Transthoracic Echocardiogram

The normal right ventricular internal diameter at end-diastole (RVIDd) should be less than 4.1 cm when measured at the base and less than 3.5 cm at the mid-level in the RV-focused view. 1

Measurement Technique and Normal Values

• RVIDd is defined as the size of the minor-axis cross-sectional diameter measurement of the right ventricular chamber just below the tricuspid valve at end-diastole, reported in centimeters 1
• The measurement should be taken from the RV-focused apical four-chamber view 1
• Two standard measurements are recommended:
  • Basal RV linear dimension (RVD1): maximal transversal diameter in the basal one-third of RV inflow at end-diastole 1
  • Mid-cavity RV linear dimension (RVD2): transversal RV diameter in the middle third of RV inflow, approximately halfway between the maximal basal diameter and the apex 1

Clinical Significance and Interpretation

• RV size assessment is critical for evaluating conditions such as:

  • Tricuspid regurgitation (TR) - chronic severe TR typically leads to RV dilation 1
  • Pulmonary hypertension - often associated with RV enlargement 2
  • Arrhythmogenic right ventricular cardiomyopathy (ARVC) 1

• Qualitative assessment of RV size should be reported as:

  • Normal
  • Reduced
  • Mildly enlarged
  • Moderately enlarged
  • Severely enlarged 1

Advantages and Limitations of RVIDd Measurement

Advantages:

• Easily obtainable measurement 1
• Simple and fast to perform 1
• Extensive published normative data available 1

Limitations:

• RV size may be underestimated due to the crescent RV shape 1
• Measurements are dependent on probe rotation and different RV views 1
• For accurate inter-study comparison, the echocardiography report should specify the window from which the measurement was performed 1

Additional RV Assessment Parameters

For comprehensive RV evaluation, consider these additional measurements:

• RV area at end-diastole: measured by planimetry of a single longitudinal RV image (usually apical 4-chamber view), reported in cm² 1
• RV volume at end-diastole: reported in mL, ideally using 3D echocardiography for more accurate assessment 1
• RV fractional area change: normal is >32% 1
• Tricuspid annular plane systolic excursion (TAPSE): important for assessing RV function 2

Clinical Pearls

• In patients with severe tricuspid regurgitation, an end-systolic RV eccentricity index >2 suggests severe TR 1
• For non-significant right-sided chamber enlargement, accepted cut-off values include:
  • Mid-RV dimension ≤33 mm
  • RV end-diastolic area ≤28 cm²
  • RV end-systolic area ≤16 cm²
  • RV fractional area change >32% 1
• Early detection of RV enlargement is important as RV dysfunction may be seen in both left-sided and right-sided valvular heart disease 1
• Progressive RV dysfunction may result from chronic TR, with flail tricuspid valve being associated with decreased survival and increased risk of heart failure 1