How do you calculate Right Ventricle (RV) fractional area change, Myocardial Performance Index (MPI) of the Right Ventricle (RV), and what is the normal value of S' (velocity of the tricuspid annulus during systole) of the Right Ventricle (RV) on a 2D echocardiogram?

Right Ventricular Assessment on 2D Echocardiography: Calculation Methods and Normal Values

The right ventricular fractional area change (RV FAC), myocardial performance index (MPI), and tricuspid annular systolic velocity (S') are essential parameters for comprehensive assessment of right ventricular function, with specific calculation methods and established normal values that should be routinely measured during echocardiographic evaluation. 1

RV Fractional Area Change (FAC) Calculation

RV FAC is a key measure of global RV systolic function that correlates strongly with RV ejection fraction by cardiac MRI (r = 0.80) 2.

Calculation Method:

• Obtain RV-focused apical four-chamber view
• Trace the RV endocardial border at end-diastole to measure RV end-diastolic area (RVEDA)
• Trace the RV endocardial border at end-systole to measure RV end-systolic area (RVESA)
• Calculate using the formula: RV FAC (%) = [(RVEDA - RVESA)/RVEDA] × 100 1

Normal Values:

• Normal RV FAC: 49 ± 7% (abnormal if <35%) 1
• Advantages: Established prognostic value, reflects both longitudinal and radial components of RV contraction
• Limitations: Neglects RV outflow tract contribution, moderate inter-observer reproducibility 1

Right Ventricular Myocardial Performance Index (RIMP/Tei Index)

RIMP is an index of global RV performance that combines systolic and diastolic function.

Calculation Methods:

1. Pulsed Doppler Method:

   • Measure tricuspid valve closure-to-opening time (TCO)
   • Measure RV ejection time (ET)
   • Calculate: RIMP = (TCO - ET)/ET 1

2. Tissue Doppler Method:

   • Measure isovolumic contraction time (IVCT)
   • Measure isovolumic relaxation time (IVRT)
   • Measure ejection time (ET)
   • Calculate: RIMP = (IVCT + IVRT)/ET 1

Normal Values:

• Pulsed Doppler RIMP: 0.26 ± 0.085 (abnormal if >0.43)
• Tissue Doppler RIMP: 0.38 ± 0.08 (abnormal if >0.54) 1
• Advantages: Prognostic value, less affected by heart rate
• Limitations: Unreliable when right atrial pressure is elevated; pulsed Doppler method requires matching R-R intervals 1

Tricuspid Annular Systolic Velocity (S')

S' measures the longitudinal systolic function of the RV.

Measurement Method:

• Obtain apical four-chamber view
• Position pulsed-wave tissue Doppler sample volume at lateral tricuspid annulus
• Align Doppler beam parallel to RV free wall longitudinal excursion
• Measure peak systolic velocity (S') 1

Normal Values:

• Pulsed Doppler S': 14.1 ± 2.3 cm/sec (abnormal if <9.5 cm/sec)
• Color Doppler S': 9.7 ± 1.85 cm/sec (abnormal if <6.0 cm/sec) 1
• A value of S' >17.25 cm/sec strongly suggests normal RV function 3

Clinical Application and Pitfalls

Key Considerations:

1. Optimal RV Imaging:

   • Use RV-focused apical four-chamber view with maximal RV diameter in the transverse plane 4
   • Unfocused views can lead to approximately 10% underestimation of RV areas 4

2. Integration of Multiple Parameters:

   • RV FAC correlates best with MRI-derived RV ejection fraction 2
   • MPI correlates significantly with RV ejection fraction (r = -0.55) 3
   • S' provides complementary information about longitudinal RV function 1

3. Common Pitfalls:

   • Inadequate endocardial definition: Use zoomed imaging with focus on RV mid-wall and respiratory maneuvers to improve border definition 1
   • Improper alignment: Ensure proper alignment of M-mode cursor or Doppler beam with direction of RV longitudinal excursion 1
   • Neglecting RV outflow tract: RV FAC only assesses the body of the RV, not the outflow tract 1

Advanced Techniques:

• 3D echocardiography provides more accurate volume measurements and overcomes geometric assumptions of 2D methods 5
• RV free wall longitudinal strain offers angle-independent assessment with prognostic value 1

By systematically measuring these parameters, clinicians can comprehensively evaluate RV function, which is crucial for management decisions in various cardiac conditions.