Pulmonary Hypertension Echocardiography

OVERVIEW

Pulmonary arterial hypertension (PAH) is traditionally defined as an increase in mean pulmonary arterial pressure (PAPm) ≥25 mmHg at rest as assessed by right heart catheterization (RHC) (Galie et al, 2019)

• Recently it has been proposed to include pulmonary vascular resistance (PVR) ≥3 Wood Units (WU) into the definition of pre-capillary pulmonary hypertension (PH) associated with mPAP >20 mmHg, irrespective of aetiology (Galie et al, 2019)
• normal PAPm at rest is 14+3 mmHg with an upper limit of normal of approximately 20 mmHg (97.5th percentile) (Simmonaeu et al, 2019)

Transthoracic echocardiogram (TTE) remains the most important non-invasive screening tool for PH

• Right heart catheterisation remains the gold standard and is considered mandatory for diagnosis of PH (Simmonaeu et al, 2019)

Severity of pulmonary hypertension (mPAP)

• Mild = 20-40mmHg
• Moderate = 41-55mmHg
• Severe = > 55mmHg

MEASUREMENT OF PULMONARY ARTERY PRESSURE

Calculation of PAP from Peak tricuspid regurgitation velocity (ms-1)

• Doppler Echo can approximate pulmonary artery systolic pressure (PASP) using
  • tricuspid valve velocity (4v2 = TV pressure gradient)
  • estimated CVP (=RA pressure)
  • Bernoulli equation
• PASP = RVSP (in the absence of RVOTO or pulmonic stenosis)
  • RVSP = 4v2 + CVP
• Mean PAP can be approximated because PAPm = 0.61•sPAP + 2.
  • A systolic PAP of 30 mm Hg typically implies a mean PAP more than 20 mm Hg, i.e. pulmonary hypertension

Echocardiographic probability of pulmonary hypertension (PH) in symptomatic patients with a suspicion of PH (from Frost et al, 2019)

Peak tricuspid regurgitation velocity ms-1	Other “PH echo signs” present	Echo probability of PH
<=2.8 or not measurable	No	Low
<=2.8 or not measurable 2.9-3.4	Yes No	Intermediate
2.9-3.4 >=3.4	Yes Not required	High

The mean and end diastolic pressures in the pulmonary artery are directly assessed by measuring peak and end-diastolic velocities of the pulmonary regurgitant (PR) jet

• Diastolic PA pressure (PAPd) = PR end diastolic pressure gradient + RA pressure
• Mean PA pressure (PAPm) = PR peak pressure gradient + RA pressure

Mean pulmonary arterial pressure (PAPm) can also be calculated from the acceleration time of the RVOT VTI.

OTHER ECHOCARGRAPHIC FINDINGS

Echocardiographic signs suggesting pulmonary hypertension (PH) used to assess the probability of PH in addition to tricuspid regurgitation velocity measurement (see above) (from Frost et al, 2019). Echocardiographic signs from at least two different categories (A/B/C) from the list should be present to alter the level of echocardiographic probability of PH.

A: The ventricles	B: Pulmonary artery	C: Inferior vena cava and right atrium
Right ventricle/left ventricle basal diameter ratio >1.0	Right ventricular outflow Doppler acceleration time <105 ms and/or mid-systolic notching	Inferior cava diameter >21 mm with decreased inspiratory collapse (<50% with a sniff or <20% with quiet inspiration)
Flattening of the interventricular septum (left ventricular eccentricity index >1.1 in systole and/or diastole)	Early diastolic pulmonary regurgitation velocity >2.2 m·s–1	Right atrial area (end-systole) >18 cm2
	Pulmonary artery diameter >25 mm

The underlying cause of PH may also be identified, such as:

• LV failure
• mitral or aortic valve disease
• shunts
• PE

REFERENCES

LITFL

• CCC – Pulmonary hypertension
• Wiesbauer F. Hypertension. Medmastery

Journal articles

• Frost A, Badesch D, Gibbs JSR, et al. Diagnosis of pulmonary hypertension. Eur Respir J 2019; 53: 1801904. [PMC free article] [PubMed]