The presence of right heart strain in an acutely dyspneic and hemodynamically unstable patient is suggestive of (albeit non-specific for) an acute pulmonary embolism. Echocardiographic signs of right heart strain include ⁵:

• right ventricular dilation
  • an end-diastolic RV:LV diameter ratio > 1 defines severe
• right ventricular systolic dysfunction
  • a pattern of right ventricular free wall hypokinesis with apical sparing is often found, referred to as the McConnell's Sign
• paradoxical septal motion
  • an abrupt rise in pulmonary arterial pressures prolong right ventricular contraction
  • persistence of elevated RV pressures as the LV begins to relax results in reversal of the normal interventricular septal curvature
• right atrial dilation
  • leftward bowing of the interatrial septum may be seen, as with the interventricular septum
• tricuspid regurgitation
  • often secondary to annular dilation resulting in valvular incompetence
• dilation of the inferior vena cava
  • with loss of its usual phasic variation throughout the respiratory cycle
  • a sonographic correlate of elevated right atrial/central venous pressures

Given the superior test characteristics of CT and VQ scanning, echocardiography is not considered a first-line diagnostic test for the exclusion of pulmonary embolism in the majority of patients. However, it remains useful in the critically ill and/or unstable patient due to its portability, speed, ability to assess for emergent diagnoses presenting in a similar manner (e.g. pericardial tamponade, tension pneumothorax, acute left ventricular failure), and lack of need for potentially nephrotoxic contrast use. Furthermore, in massive pulmonary embolism or peri-arrest situations which preclude further imaging, it may be used to empirically administer thrombolysis or anticoagulation ².