Echocardiography in Chronic Thromboembolic Pulmonary Hypertension
Section snippets
Overview of Echocardiography in PHTN and CTEPH
PHTN results in increased right ventricular afterload and myriad of subsequent hemodynamic and structural changes, many of which can be assessed by echocardiography. These findings are not pathognomonic for CTEPH but can be seen in other causes of PHTN. The salient features of significant pulmonary hypertension include (Fig. 1) the following: right ventricle (RV) enlargement, RV hypertrophy followed by RV systolic dysfunction, tricuspid valve annular dilation and tricuspid regurgitation,
Diagnosis of PHTN
While some patients with significant chronic thromboembolic disease may have little to no PHTN, most present with significant elevations in pulmonary arterial pressures. Echocardiography provides a simple noninvasive technique to estimate pulmonary arterial pressure and therefore diagnose PHTN.
During systole, in the absence of significant pulmonary valve stenosis, the pressure in the RV and pulmonary artery are essentially identical. RV pressures can be easily estimated by echocardiography
Degree of Tricuspid Regurgitation
PHTN is associated with RV hypertrophy and ultimately RV enlargement, leading to a dilation of the tricuspid valve annulus. This along with chordal traction of the valve leaflets results in tricuspid regurgitation (Fig. 4). The tricuspid regurgitation does not correlate directly with the degree of PHTN per se but rather more directly with the degree of RV enlargement and changes in RV geometry. Here again echocardiography allows for the evaluation of the degree of tricuspid regurgitation both
RV Size and Function
As PHTN progresses, the RV enlarges and its function may become depressed. Echocardiography can provide helpful information on both RV size and function, although the assessment is often qualitative, given the complexity of RV geometry. The most helpful view to assess RV enlargement is the apical four-chamber view. In normal individuals (in the apical four-chamber view) the left ventricle (LV) is larger than the RV and fills the apex. In the presence of RV enlargement, the RV area exceeds the
Pericardium and Coronary Sinus
The marked elevations in RV and RA pressures in CTEPH may lead to impaired lympathic and venous drainage from the pericardium with resultant pericardial effusions, easily detected on echocardiography. The presence of pericardial effusion correlates with increased RA pressures.12
Similarly elevated RA pressure may impair coronary sinus drainage and lead to enlargement of the coronary sinus, again easily visualized with echocardiography.13
The LV and Septum in CTEPH
The overload on the right heart in CTEPH results in the septum being frequently distorted with flattening and even bulging into the LV cavity. This results in a characteristic D-shaped LV (Fig. 5), in contrast to a normally circular LV, in the parasternal short-axis view. By measuring the two axes of the LV in the parasternal short-axis view, an eccentricity index can be determined. Normally with a circular LV this index is 1 during both systole and diastole.14
The overload on the right heart in
Mitral Valve in CTEPH
The marked distortion of the LV caused by the pressure overload in CTEPH may lead to distortion of the mitral valve annulus and subsequent mitral valve prolapse and mitral regurgitation. Following PTE surgery this “pseudo” mitral valve prolapse often reverses.15
Diastolic Function in CTEPH
CTEPH has also been associated with abnormal LV diastolic falling. Initial studies demonstrated that abnormal LV diastolic function seen in RV pressure overload was largely mediated through the intraventricular septum. Subsequent more detailed analysis of echocardiographic diastolic filling parameters E and A revealed E/A reversal (E/A ratio <1.5) in CTEPH patients. Postsurgery and with the resolution of pulmonary hypertension there was a significant improvement in the ratio. In fact, following
Preoperative Assessment of Potential CTEPH Candidates
There have been preliminary reports that echocardiography can distinguish between CTEPH and primary pulmonary hypertension (PPH) as a cause of pulmonary hypertension.18, 19, 20 However, in a follow-up prospective study of 142 patients, echocardiography was not sufficiently accurate to differentiate between the two entities.21 At UCSD we have relied primarily on ventilation-perfusion (V/Q) scanning and pulmonary angiography/angioscopy to differentiate the two entities. However, routine
Postoperative Assessment of PTE Surgery
Following successful PTE surgery significant changes occur rapidly in cardiac morphology and function (Fig. 8). RV volumes and function improve rapidly, even before discharge, and continue to improve in the subsequent months. The eccentricity index may normalize immediately postoperatively in conjunction with the decrease in pulmonary pressures. Tricuspid regurgitation and cardiac output also improve. All of these parameters are easily evaluated by echocardiography.17 Furthermore patients who
Conclusions
Echocardiography plays an integral role in the diagnosis of CTEPH patients, and also in their preoperative as well as postoperative assessment. Further studies of newer echocardiography techniques such as tissue Doppler and 3D echo may continue to provide insight in the pathophysiology of this disease.
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