Assessment of Intracardiac Pressures

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Definition

According to the modified Bernoulli equation (that correlates directly the velocity recorded across an orifice with the pressure difference between the proximal and distal portion of the orifice, see even Basic principles of non-invasive hemodynamics), one important application of echo-Doppler technique is the assessment of intracardiac pressures. Whenever an intracardiac jet velocity can be captured as in valve stenosis/ regurgitation or intracardiac shunt, then a corresponding instantaneous pressure gradient can be obtained. A non-invasive measurement of intracardiac pressure results from the addition of that gradient to other measurable parameters such as the omeral arterial pressure or the estimated central venous pressure (or mean right atrial pressure). Moreover, an estimation of left ventricular filling pressure derives from the combination of spectral- color- and tissue-Doppler data.[1]

Right ventricular systolic pressure

Right ventricular systolic pressure (RVSP) can be easily assessed in most subjects who present some degree of tricuspid regurgitation. The velocity recorded across the regurgitant jet corresponds to the right ventricular-right atrial gradient (RV-RA ΔP), so that, this value added to mean right atrial pressure (RAP) represents the right ventricular systolic pressure[2](figure 1): RVSP = RV-RA ΔP + RAP

Fig1 pressure.jpg
Figure 1. CW Doppler recording of tricupidal regurgitation, obtained from apical view of right ventricle in a patient affected by severe pulmonary artery hypertension. The peak velocity, 4.7 m/sec (marker 1), confirms the augmented gradient between right ventricle and right atrium.

calculation of right ventricular systolic pressure in VSD

RVSP can also be calculated in presence of a ventricular septal defect as the difference between cuff-measured systolic blood pressure (in the absence of any obstacle at the left ventricular outflow tract) and the interventricular gradient (estimated across the ventricular septal defect) (figure 2).[1].

Fig2 pressure.jpg
Figure 2. Systolic velocity pattern recorded across a small ventricular septal defect by a long axis parasternal view in a young patient. The CW Doppler spectrum is displayed above the baseline because the jet is directed toward the right ventricle. The difference between the omeral systolic artery during the exam (115 mmHg) and the measured peak gradient (95 mmHg) is consistent with a normal right ventricular systolic pressure (20 mmHg).

Right atrial pressure

The right atrial pressure (RAP) can be estimated from the end-expiratory diameter and respiratory changes of the inferior vena cava (IVC) as follows (figure 3)[2]:

  • Normal diameter (≤2,1 cm) and inspiratory collapse (>50%), RAP 3 mmHg (range, 0-5 mmHg)
  • Dilated IVC (≥ 2,1 cm) with reduced respiratory variation (<50%), RAP 15 mmHg (range, 10-20 mmHg)
  • IVC diameter and respiratory variation unfitting the previous paradigm, without resolving hepatic flow pattern (absence of prevalent systolic or diastolic flow component) or tricuspid E/e’ wave ratio, RAP 8 mmHg (range, 5-10 mmHg)
Fig3 pressure.jpg
Figure 3. M-mode trace of inferior vena cava (IVC) recorded from subcostal view just proximal to hepatic vein. A normal diameter (<2,1 cm) of IVC with significant respiratory variation (>50%) suggest a normal right atrial pressure (0-5 mmHg).

Pulmonary artery systolic pressure

If there is no obstruction at the right ventricular outflow tract, RVSP equals the pulmonary artery systolic pressure (PASP).[2]


Pulmonary artery diastolic pressure

Pulmonary artery end-diastolic pressure (PADP) can be estimated in the presence of a well-distinct pulmonary regurgitation flow as follows:

Indented line

PADP = EDP ΔP + RAP

Where EDP ΔP indicates the end-diastolic pulmonary regurgitation gradient[3] (figure 4).

Fig4 pressure.jpg
Figure 4. PW-Doppler of a well defined pulmonary regurgitant jet obtained from the short axis view at the level of great vessels. The mean pulmonary artery pressure can be assessed by peak protodiastolic gradient (marker 1) added to right atrial pressure (RAP); likewise, diastolic pulmonary pressure derives from end-diastolic gradient (marker 2) added to RAP.


Mean pulmonary artery pressure


Mean pulmonary artery pressure (MPAP) can be easily derived by systolic and diastolic pressure as: 1/3 PASP + 2/3 PADP. Alternatively, it can be estimated by pulmonary regurgitant jet as highest protodiastolic gradient added to estimated RAP (figure 4)[2] or, by pulmonary antegrade Doppler spectrum, through the measurement of acceleration time (AT), so that: MPAP = 90 – (0.62 x AT), if AT is <120 ms and heart rate range 60-100 bpm (figure 5).[4] Finally, MPAP can be calculated, according a recently validated method as tricuspidal regurgitant jet velocity-time integral added to RAP.[5]

Fig5 pressure.jpg
Figure 5 PW Doppler trace sampled on right ventricular outflow tract in a subject with severe pulmonary artery hypertension; the acceleration time (AT) is determined by the onset of systolic flow velocity to the systolic peak. The estimated mean pulmonary artery pressure (MPAP) was around 50 mmHg, according the formula MPAP = 90 – (0.62 x AT) (see text).


Left ventricular filling pressure

Left ventricular filling pressure and so atrial diastolic pressure can be estimated using a combination of Doppler parameters. Although mitral inflow Doppler pattern alone allows a first classification of diastolic dysfunction, especially in subjects with reduced systolic function, its dependence on load condition and other factors (i.e. age and heart rate), requires its integration with tissue-Doppler (TD) imaging assessment of left ventricular myocardial velocities, pulmonary venous flow (Figure 6), data obtained from mitral inflow pattern changes with Valsalva manouver or velocity inflow propagation and pulmonary artery pressure (in absence of lung disease).[6] In subjects with normal systolic function (left ventricular ejection fraction >55%) the E / e’ wave ratio and the isovolumic relaxation time/TE-e’ have shown a good correlation with left ventricular filling pressure.[1]

Fig6 pressure.jpg
Figure 6. Diastolic function assessment in an apparent healthy subject. The E/A wave ratio of transmitral velocity pattern is >1 (A); the mean E/e’ wave ratio obtained by integration of transmitral Doppler with PW-tissue Doppler of basal interventricular septum (C) and basal lateral wall (D) is around 4.5; the pulmonary vein velocity waveforms (B) display a diastolic component mildly higher than systolic and a small and short atrial reversal wave; All these parametrs are consistent with a normal left ventricular filling and so diastolic atrial pressure.

References

  1. 1.0 1.1 1.2 Galiuto L, Badano L, Fox K, Sicari R, Zamorano JL. The EAE Textbook of Echocardiography. Oxford University Press, London, 2011.
  2. 2.0 2.1 2.2 2.3 Rudsky LG, Lai WW, Afilalo J et al. Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and the Canadian Society of Echocardiography. J Am Soc Echocardiogr 2010;23(7):685-713.
  3. Masuyama T, Kodama K, Kitabatake A, Sato H, Nanto S, Inoue M. Continuous wave Doppler echocardiographic detection of pulmonary regurgitation and its application to noninvasive estimation of pulmonary artery pressure. Circulation 1986; 74:484–492.
  4. Dabestani A, Mahan G, Gardin JM et al. Evaluation of pulmonary artery pressure and resistance by pulsed Doppler echocardiography. Am J Cardiol 1987;59:662-8.
  5. Aduen JF, Castello R, Lozano MM et al. An alternative echocardiographic method to estimate mean pulmonary artery pressure: diagnostic and clinical implications. J Am Soc Echocardiogr 2009;22:814-9.
  6. Nagueh SF, Appleton CP, Gillebert TC, et al. Recommendations for the Evaluation of Left Ventricular Diastolic Function by Echocardiography. Eur J Echocardiogr. 2009;10(2):165-93.
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