Right ventricular function (point of care ultrasound)

Right ventricular function is often measured in point-of-care ultrasonography as a composite of the right ventricular size, wall measurements, and contractile efforts. 

Terminology

The right ventricle (RV) can be anatomically divided into an inflow portion, an outflow portion, and an apex. Contraction of the right heart primarily occurs in a longitudinal manner, with radial and circumferential thickening playing a less important role than on the left. The right ventricular free wall accounts for most of the contractile power, and may be insonated most directly in the subcostal window. ⁵

Epidemiology

A dysfunctional right ventricle may be found in the following:

• chronic obstructive lung disease
• pulmonary hypertension
• chronic congestive heart failure

Pathology

Etiology

Common precipitants of right ventricular dysfunction include pressure overload, volume overload, ischemia, or a combination of all three. Examples include:

• acute pulmonary embolism
• right ventricular myocardial infarction
• pericardial tamponade

Radiographic features

The geometry of the right ventricle is more complex than that of the left ventricle (LV), anterior to and wrapping around the left ventricle. A global visual assessment of right ventricular function and size precede quantitative measurement ³. A normal right ventricle is two-thirds the size of the left ventricle, as measured in diastole.

Ultrasound

RV enlargement can be estimated using the “rule of thirds” in the parasternal long-axis view, or by comparing its size relative to that of the LV in the apical four-chamber view. The RV diameter does not normally exceed one-third the total ventricular width in the apical four-chamber view. Quantification of RV volumes and systolic function by echocardiography include the following indices:

• tricuspid annular plane systolic excursion (TAPSE, normal >1.6 cm) ¹
  • the anteroposterior excursion of the tricuspid free annulus during systole
  • obtained from the apical 4 chamber window, with an M-mode pick directed through the lateral tricuspid annulus
  • a peak excursion of 1.5 cm or less is pathologic ⁶
• right ventricular fractional area change (normal range 32-60%) ⁶
  • assessed in a right ventricular optimized apical 4 chamber view at end diastole (RVEDA) and end-systole (RVESA) ²
  • calculate the percentage of change with the equation (RVEDA-RVESA) / RVESA 
  • most cumbersome method to perform, but most accurate when compared to MRI measurements ⁴
• systolic excursion velocity (normal S' >10 cm/s)
  • from an apical window, the tissue Doppler gate is placed on the lateral right ventricular wall, 1-2 cm above the tricuspid annulus
  • S' corresponds to the peak of the positive inflection

Differential diagnosis

General imaging differential considerations for right ventricular dysfunction include:

• regional wall motion abnormalities ⁵
  • the presence of regional wall motion abnormalities favors ischemia as the etiology
  • global depression usually implies a non-ischemic mechanism
• free wall thickening
  • right ventricular free wall thickness should never exceed 5 mm, as measured at end diastole
  • wall thickening implies the presence of a chronic pressure overload, while a thin wall favors an acute process
• hyperdynamic apex
  • previously thought to be specific for pulmonary embolism, McConnell's sign refers to the presence of akinesia of the mid free wall but normal motion at the apex ⁷
  • present in other states of right ventricular strain, including right ventricular myocardial infarction ⁸