What does an inability to measure pulmonary artery systolic pressure (PASP) due to an insufficient tricuspid regurgitant (TR) jet on echocardiogram (echo) indicate?

Understanding Insufficient Tricuspid Regurgitation Jet on Echocardiography

The inability to measure pulmonary artery systolic pressure (PASP) due to insufficient tricuspid regurgitation (TR) jet on echocardiography does not rule out pulmonary hypertension and requires alternative assessment methods.

Clinical Significance

When an echocardiogram report indicates "inability to measure PASP due to insufficient TR jet," this means:

• The tricuspid regurgitation jet is too small or inadequately visualized to allow accurate measurement of the peak velocity
• PASP cannot be calculated using the modified Bernoulli equation (PASP = 4 × [TR velocity]² + estimated right atrial pressure) 1
• This finding is common, occurring in approximately 36% of patients referred for echocardiography 2

Implications for Pulmonary Hypertension Assessment

This finding has important clinical implications:

• Does not exclude pulmonary hypertension: Studies show that 47% of patients without a measurable TR jet who undergo right heart catheterization have pulmonary hypertension 2
• Reduced sensitivity: The absence of a measurable TR jet has a negative predictive value of only 53% for excluding pulmonary hypertension 2
• Technical limitations: Factors such as pulmonary hyperinflation, altered thoracic anatomy, and body habitus can impair TR jet visualization 1

Alternative Assessment Methods

When TR jet is insufficient, guidelines recommend using alternative echocardiographic parameters to assess for possible pulmonary hypertension:

1. Right ventricular outflow tract (RVOT) assessment:

   • Pulmonary acceleration time (PAT) <105 ms
   • Mid-systolic notching in the RVOT Doppler flow pattern 1

2. Right heart chamber evaluation:

   • Right ventricular hypertrophy or dilation
   • Right atrial enlargement (area >18 cm² in end-systole)
   • Flattening of the interventricular septum (eccentricity index >1.1) 1

3. Inferior vena cava assessment:

   • Diameter >21 mm with decreased inspiratory collapse (<50% with sniff or <20% with quiet inspiration) 1

4. Other indicators:

   • Pulmonary artery diameter >25 mm
   • Early diastolic pulmonary regurgitation velocity >2.2 m/s 1

Clinical Approach

When faced with an insufficient TR jet:

1. Evaluate alternative echocardiographic signs as listed above
2. Consider contrast enhancement with agitated saline to improve Doppler signal and potentially allow TR jet measurement 1
3. Assess clinical risk factors for pulmonary hypertension, particularly in patients with:
   • Right ventricular dysfunction
   • Enlarged left atrium
   • Elevated BMI
   • Elevated BNP
   • History of heart failure or diabetes 2
4. Consider right heart catheterization if clinical suspicion remains high despite inconclusive echocardiography 1

Common Pitfalls

• False reassurance: Assuming normal pulmonary pressures due to absence of measurable TR jet 2
• Overlooking alternative signs: Failing to assess other echocardiographic indicators of pulmonary hypertension 1
• Underestimating severity: In severe TR, the jet velocity may be underestimated, potentially masking elevated pulmonary pressures 1
• Technical limitations: Obesity, lung hyperinflation, and altered cardiac position can all limit TR jet assessment 1

Remember that echocardiographic probability of pulmonary hypertension should be assessed using multiple parameters, not just TR jet velocity, especially when the latter is unavailable 1.