Echocardiographic Prognostic Factors in Pulmonary Hypertension

*Gabriela Silvia Gheorghe, Andrei Cristian Dan Gheorghe, Ana Ciobanu and Andreea Simona Hodorogea*

## **Abstract**

Pulmonary hypertension (PH) is defined as an increase in mean pulmonary arterial pressure of ≥25 mmHg at rest by right heart catheterization. Echocardiography estimates systolic pulmonary arterial pressure on the tricuspid regurgitation jet velocity, mean and diastolic pressure based on the pulmonary regurgitation jet, and data regarding the function of the right ventricle. ESC guidelines propose an echocardiographic risk assessment in PH according to right atrial area > 26 cm2 and pericardial effusion. Other risk factors correlated with the severity of the PH include right atrial pressure > 15 mmHg, tricuspid regurgitation more than moderate, TAPSE <18 mm, tricuspid S<sup>0</sup> < 11.5 cm/s assessed by TDI, right ventricle ejection fraction <45% using 3D imaging, fractional area change of the right ventricle <35%, dP/dt < 400 mmHg/s on the tricuspid regurgitation flow, reduced strain of the right ventricle, diastolic dysfunction. Left ventricular eccentricity index (EI) >1.7 combined with TAPSE <15 mm was associated with a higher death rate compared to patients with normal values. However, each of these parameters used in the assessment of the right ventricle has technical limitations, and it is necessary to use multiple tests for a correct evaluation of the prognosis of PH.

**Keywords:** pulmonary hypertension, tricuspid regurgitation, right ventricle, right atrium, global strain

### **1. Introduction**

Pulmonary hypertension (PH) is defined as an increase in mean pulmonary arterial pressure (mPAP) of ≥25 mmHg at rest as assessed by right heart catheterization. Current data have shown that the normal mPAP at rest is 14 � 3 mmHg with the upper limit of normal of approximately 20 mmHg. The clinical significance of mPAP between 21 and 24 mmHg is unclear [1]. There are also unclear data regarding the normal versus exaggerated elevation of mPAP at physical effort, making it difficult to put the diagnosis of exercise-induced PH. Pulmonary vascular resistance (PVR) with a cut-off of ≥3 Wood units has been included in the hemodynamic diagnosis of PH, and pulmonary artery wedge pressure (PAWP) with a cut-off of ≥15 mmHg is used for the classification of PH in pre-capillary, post-capillary, or combined pre- and postcapillary PH [1]. PH is classified into five groups, depending on the underlying disease [1].

Not all patients with PH perform right heart catheterization, and, in practice, the diagnosis of PH is based on the echocardiographic evaluation of the pulmonary artery pressure. Also, echocardiography can detect the underlying disease and the consequences of the PH on the right and left ventricles (**Table 1**), [2–8]. Nevertheless, the echocardiographic evaluation of the right heart is more difficult than that of the left heart because of the complex shape of the right ventricle (RV) and its load-dependent physiology. Its shape in apical 4-chamber view is more triangular, in contrast to the left ventricle more conical. In the parasternal short axis view, it is like a crescent. The cavity of the RV has three parts: inlet, apical trabeculae, and outlet segments. The outlet segment is not trabeculated and is separated from the inlet segment by the supraventricular crest. The subepicardial myofibrils have a circumferential orientation, and the subendocardial myofibrils have predominantly a longitudinal orientation [9, 10]. The interventricular septum separates the right and left ventricles and bulges into RV during the ventricular systole. From the three leaflets of the tricuspid valve, the septal leaflet is usually visible by echocardiography. The 2D echography has a low sensitivity for defining the RV endocardial border contour of the free wall and of the apex. The complex morphology of the RV makes the correct echocardiographic evaluation difficult and implies great variation in the 2D measurement results of the RV diameters and area. In a study that included 900 patients, Tamborini G. et al. [11] demonstrated high inter- and intraobserver variabilities in the measurements of RV fractional area change (FAC), a parameter of RV systolic function. There are also difficulties in the echocardiographic examination of the right atria (RA). RA has an ellipsoid shape and includes crista terminalis, RA appendage, cavotricuspid isthmus, Eustachian valve, the orifice of the coronary sinus, and Thebesian valve. Echographic data include RA indexed major and minor axis length and systolic RA volume. The values are different in men and women, and the indexed RA volume using the single-plane method of disks has lower values than those obtained by the area-length method [12]. RA becomes dilated, and a process of RA remodeling occurs in longstanding PH. The RA pressure (RAP) increases, and its evaluation according to the diameter and inspiratory changes of the inferior vena cava (IVC) is an important parameter for the evaluation of RV systolic pressure in the absence of significant RV outflow tract obstruction. The RAP estimated non-invasively is the main source of errors in the assessment of both sPAP and mPAP. sPAP is calculated using the maximal velocity of tricuspid regurgitation flow (**Figure 1**) and mPAP by formulas that use pulmonary regurgitation flow velocity at the beginning of the diastole or pulmonary velocity acceleration time. Both can underestimate the PH in case of RV failure. RV failure can impede the left ventricle (LV) function by many mechanisms. So assessing the RV and LV morphology and function is essential for the correct diagnosis and prognostic of PH. The echocardiographic evaluation of the right heart can be improved through other methods, such as agitated saline study, echocardiographic contrast agents, speckle tracking, and 3D echocardiography [13]. 2D RV longitudinal strain of the free wall (RV-FWS) and 2D RV global longitudinal strain (RV-GLS), which includes in the analysis of the interventricular septum, can demonstrate subclinical impairment of the longitudinal contraction in patients with PH. The method is less angle and load-dependent and less influenced by the complex geometry of RV, but it depends on image quality that can be poor because of many artifacts [14, 15]. The analysis of segmental contractility of the RV walls by strain technique offers information about the pattern of RV remodeling in PH. The cut-off value proposed for RV-FWS is 23% and 20% for RV-GLS. For now, there is no consensus on which method to use, but it seems that RV-FWS is more useful. The 3D technique is more accurate than the 2D technique in the evaluation of RV strain.




*RVOT = right ventricle outflow tract; VTIRVOT = velocity time integral in the right ventricle outflow tract; PR = pulmonary regurgitation; TDE = E wave deceleration time; V = velocity; TDI = tissue Doppler imaging; LV = left ventricle; PW = pulse wave; CW = continuous wave; and IVC = inferior vena cava.*

#### **Table 1.**

*Echocardiographic parameters used for the diagnosis of pulmonary hypertension.*

Also, right ventricular ejection fraction (RVEF) calculated by the 3D technique (3D-RVEF) is far more accurate than that calculated by the 2D technique (2D-RVEF) because it is independent of geometric assumptions. 3D-RVEF but not 2D-RVEF is validated in relation to cardiac magnetic resonance (CMR) imaging, the "gold standard" for assessing RVEF.

Also, 3D speckle–tracking technique provides a more accurate assessment of ventricular myocardial dynamics than 2D speckle-tracking, which is limited by the outof-plane motion of different frames. At the same time, measurement of RVEF by 3D echocardiography is not possible in all patients because it requires good image quality [15]. Evaluation of RV shape by 3D technique is not currently used in clinical practice. In patients with a good image of tricuspid regurgitation Doppler signal, one can calculate other parameters with prognostic values, such as right ventricle-pulmonary artery coupling (RV-PA) and myocardial work.

Each technique has its limits, and one must use a multimodal evaluation of the anatomy and function of RV. Furthermore, these new echographic techniques are not standardized between different vendors. Indeed, the gold standard for RVEF evaluation remains for now cardiac magnetic resonance imaging. **Table 1** includes the echocardiographic parameters used in the evaluation of PH and RV.

**Table 1** includes the echocardiographic parameters used in the evaluation of PH and RV (**Figures 1**–**4**).

#### **Figure 1.**

*Parasternal four chamber view. Tricuspid regurgitation (continuous Doppler examination). Right atrial dilation.*

#### **Figure 2.**

*Example of measurement of mPAP and dPAP in a case with pulmonary hypertension (left) versus a case without pulmonary hypertension (right). Left image: In this case, there was a dilated inferior vena cava with a diameter of 36 mm without respiratory variations. mPAP = 4 V<sup>2</sup> PR early diastolic + RAP = 4x3.14<sup>2</sup> + 20 = 54.43 mm Hg; dPAP = 4 V<sup>2</sup> PRenddiastolic + RAP = 4x1.88<sup>2</sup> + 20 = 34.13 mm Hg. Right image: In this case, there was an inferior* vena cava *with a diameter of 16 mm with inspiratory collapse. mPAP = 4 V<sup>2</sup> PR early*

*diastolic + RAP = 4x1.66<sup>2</sup> + 3 = 14 mm Hg; dPAP = 4 V2 PRenddiastolic + RAP = 4x1.06<sup>2</sup> + 3 = 7.5 mm Hg.* *Echocardiographic Prognostic Factors in Pulmonary Hypertension DOI: http://dx.doi.org/10.5772/intechopen.107420*

#### **Figure 3.**

*Apical 4-chamber view. Dilation of the right ventricle (RV) and right atrium (RA). Displacement of the interventricular septum toward the left ventricle (LV) and interatrial septum toward the left atrium (LA).*

**Figure 4.** *3D quantification of the right ventricular ejection fraction.*
