Pulmonary arterial hypertension: the key role of echocardiography

Echocardiography is a key screening tool in the diagnostic algorithm of pulmonary arterial hypertension (PAH). It provides an estimate of right ventricular function and pulmonary artery pressure, either at rest or during exercise, and is useful in ruling out secondary causes of pulmonary hypertension (PH) such as left heart disease or congenital heart disease. Several studies have showed that echocardiography is insufficiently precise as single tool for the ultimate diagnosis of PH respect to the right heart catheterization, considered the gold standard technique. Echocardiography is valuable in assessing prognosis and treatment options, monitoring the efficacy of specific therapeutic interventions, and detecting the preclinical stages of disease. The ideal imaging modality for accurate noninvasive assessment of the right heart should be accurate and precise, not influenced by loading conditions, routinely practicable and easily repeatable. For all such reasons and considering that PAH is a rare and severe condition, a complete noninvasive assessment of right heart function requires a deep knowledge of the disease and a multimodality approach.

Right heart adaptation to pulmonary arterial hypertension: physiology and pathobiology

Survival in patients with pulmonary arterial hypertension (PAH) is closely related to right ventricular (RV) function. Although pulmonary load is an important determinant of RV systolic function in PAH, there remains a significant variability in RV adaptation to pulmonary hypertension. In this report, the authors discuss the emerging concepts of right heart pathobiology in PAH. More specifically, the discussion focuses on the following questions. 1) How is right heart failure syndrome best defined? 2) What are the underlying molecular mechanisms of the failing right ventricle in PAH? 3) How are RV contractility and function and their prognostic implications best assessed? 4) What is the role of targeted RV therapy? Throughout the report, the authors highlight differences between right and left heart failure and outline key areas of future investigation.

Exaggerated increase of exercise-induced pulmonary artery pressure in systemic sclerosis patients predominantly results from left ventricular diastolic dysfunction

OBJECTIVE

High prevalence of exaggerated pulmonary artery pressure response to exercise (EPAPR) was reported in patients with systemic sclerosis (SSc). However, pathophysiology of this phenomenon has not been well defined. Therefore, we evaluated the frequency and potential aetiology of EPAPR in SSc patients.

METHODS

We included 85 patients (79 female, 6 male, mean age 54.3 ± 13.9 years) with SSc. Transthoracic echocardiography followed by exercise Doppler echocardiography (EDE) were performed. A positive EDE was defined when at least 20 mmHg increase of tricuspid regurgitation peak gradient (TRPG) was recorded. Right heart catheterization (RHC) with exercise was performed in positive EDE patients and in subjects with resting TRPG >31 mmHg.

RESULTS

Resting TRPG >31 mmHg and/or positive EDE was found in 30 patients and they were referred to RHC. Finally, RHC was performed in 20 patients (16 pts resting TRPG >31 mmHg and 4 others normal resting TRPG and positive EDE). In 12 (60 %) of them an EPAPR with elevated pulmonary capillary wedge pressure (PCWP) was observed. Interestingly, mean left atrium (LA) diameter was greater in an EPAPR with elevated PCWP patients than in subjects with normal exercise response (39.36 ± 5.6 vs. 35.53 ± 3.48, p = 0.03). In EPAPR with elevated PCWP group greater mean value of E/E' of mitral lateral annulus was observed (7.98 ± 3.35 vs. 6.27 ± 1.94, p = 0.03). In the univariate logistic regression analysis increased LA diameter was significant predictor of EPAPR with elevated PCWP (OR 1.199, 95 % CI 1.029-1.396, p = 0.019).

CONCLUSIONS

Despite very well-known risk of PAH in systemic sclerosis patients, the excessive increase of PAP during exercise is more commonly caused by left ventricular diastolic dysfunction than pulmonary arterial vasculopathy.

Noninvasive assessment of right heart function and hemodynamics during exercise in patients with pulmonary arterial hypertension

OBJECTIVES

Noninvasive assessment of right heart function and hemodynamics in patients with pulmonary arterial hypertension (PAH) is most often performed at rest, whereas the symptoms, in general, present with exertion. Assessment during exertion is limited to symptom assessment and the 6-minute walk distance. We investigated the feasibility of obtaining echocardiographic data that could accurately reflect pulmonary artery pressures (PAP), particularly mean PAP and right ventricular function during exercise in patients with PAH.

METHODS

We investigated right ventricular function and hemodynamics using echocardiography during symptom-limited exercise in 10 consecutive patients undergoing right heart catheterization (RHC) as part of their clinical evaluation for PAH. We further assessed these measurements for correlation with known predictors of outcome in PAH in an exploratory analysis.

RESULTS

We were able to successfully obtain complete right heart measurements by echocardiography, including mean PAP, in the majority (9 of 10) of the subjects. One patient had an incomplete tricuspid regurgitation jet at rest and with exercise. Echocardiographic pulmonary vascular resistance correlated with RHC cardiac output and brain natriuretic peptide level, whereas tricuspid annular plane systolic excursion during exercise correlated with right atrial pressure on RHC, brain natriuretic peptide, and 6-minute walk distance. Tricuspid regurgitation velocity and mean PAP with exercise correlated moderately with mean PAP and cardiac output by RHC.

CONCLUSIONS

Exercise echocardiography can provide meaningful data in patients with PAH, including measuring mean PAP. The presence of correlations in this small number of patients indicates promising targets for future investigation.

Exercise-induced pulmonary hypertension: physiological basis and methodological concerns

Exercise stresses the pulmonary circulation through increases in cardiac output (.Q) and left atrial pressure. Invasive as well as noninvasive studies in healthy volunteers show that the slope of mean pulmonary artery pressure (mPAP)-flow relationships ranges from 0.5 to 3 mm Hg.min.L(-1). The upper limit of normal mPAP at exercise thus approximates 30 mm Hg at a .Q of less than 10 L.min(-1) or a total pulmonary vascular resistance at exercise of less than 3 Wood units. Left atrial pressure increases at exercise with an average upstream transmission to PAP in a close to one-for-one mm Hg fashion. Multipoint PAP-flow relationships are usually described by a linear approximation, but present with a slight curvilinearity, which is explained by resistive vessel distensibility. When mPAP is expressed as a function of oxygen uptake or workload, plateau patterns may be observed in patients with systolic heart failure who cannot further increase .Q at the highest levels of exercise. Exercise has to be dynamic to avoid the increase in systemic vascular resistance and abrupt changes in intrathoracic pressure that occur with resistive exercise and can lead to unpredictable effects on the pulmonary circulation. Postexercise measurements are unreliable because of the rapid return of pulmonary vascular pressures and flows to the baseline resting state. Recent studies suggest that exercise-induced increase in PAP to a mean higher than 30 mm Hg may be associated with dyspnea-fatigue symptomatology.

Exercise in Pulmonary Hypertension

In healthy subjects, exercise causes a complex cardiovascular and ventilatory response that allows for a 20-fold increase of oxygen consumption as compared to rest. In pulmonary hypertension (PH) this response is very much limited by a restriction of the maximum cardiac output (CO). This restriction is caused by a massively increased afterload of the right ventricle (RV) despite an adaptation that doubles right ventricular contractility as compared to normal controls.1

Echocardiography in pulmonary arterial hypertension: from diagnosis to prognosis

Pulmonary arterial hypertension is most often diagnosed in its advanced stages because of the nonspecific nature of early symptoms and signs. Although clinical assessment is essential when evaluating patients with suspected pulmonary arterial hypertension, echocardiography is a key screening tool in the diagnostic algorithm. It provides an estimate of pulmonary artery pressure, either at rest or during exercise, and is useful in ruling out secondary causes of pulmonary hypertension. In addition, echocardiography is valuable in assessing prognosis and treatment options, monitoring the efficacy of specific therapeutic interventions, and detecting the preclinical stages of disease.

Determinants and prognostic significance of exercise pulmonary hypertension in asymptomatic severe aortic stenosis

BACKGROUND

Recent studies emphasized the usefulness of exercise stress echocardiography in asymptomatic patients with aortic stenosis. Nevertheless, the additive value of exercise pulmonary hypertension (Ex-PHT) in such patients remains unexplored. We therefore aimed to identify the determinants and to test the impact on outcome of Ex-PHT in asymptomatic patients with severe aortic stenosis.

METHOD AND RESULTS

Asymptomatic patients with severe aortic stenosis (n=105; aortic valve area <0.6 cm(2)/m(2); age, 71±9 years; male, 59%) and preserved left ventricular systolic function (ejection fraction ≥55%) were prospectively submitted to exercise stress echocardiography. Resting PHT and Ex-PHT were defined as a systolic pulmonary arterial pressure >50 and >60 mm Hg, respectively. Ex-PHT was more frequent than resting PHT (55% versus 6%; P<0.0001). On multivariable logistic regression, the independent predictors of Ex-PHT were male sex (odds ratio, 4.3; P=0.002), resting systolic pulmonary arterial pressure (odds ratio, 1.16; P=0.002), exercise indexed left ventricular end-diastolic volume (odds ratio, 1.04; P=0.026), exercise e'-wave velocity (odds ratio, 1.35; P=0.047), and exercise-induced changes in indexed left atrial area (odds ratio, 1.36; P=0.006). Ex-PHT was associated with reduced cardiac event-free survival (at 3 years, 22±7% versus 55±9%; P=0.014). In a multivariable Cox proportional hazards model, Ex-PHT was identified as an independent predictor of cardiac events (hazard ratio, 1.8; 95% confidence interval, 1.0-3.3; P=0.047). When exercise-induced changes in mean aortic pressure gradient were added to the multivariable model, Ex-PHT remained independently associated with reduced cardiac event-free survival (hazard ratio, 2.0; 95% confidence interval, 1.1-3.6; P=0.025).

CONCLUSIONS

In asymptomatic patients with severe aortic stenosis, the main determinants of Ex-PHT are male sex, resting systolic pulmonary arterial pressure, and exercise parameters of diastolic burden. Moreover, Ex-PHT is associated with a 2-fold increased risk of cardiac events. These results strongly support the use of exercise stress echocardiography in asymptomatic aortic stenosis.

Diagnostic dilemmas in pulmonary hypertension

Dilemmas persist in the screening, assessment, and follow-up of patients with pulmonary hypertension, relating to issues of whom and how to screen, how to resolve ambiguities in the clinical classification of patients with multiple potential substrates of pulmonary vascular disease, how to interpret test results, how to integrate multiple clinical parameters into a global diagnosis, how to use ambiguous test results, how to determine disease severity and prognosis, and how to monitor patients on treatment. This article describes how to incorporate available information into the diagnostic process, and where lack of concrete data should impose caution in patient management.

REVEAL Registry: correlation of right heart catheterization and echocardiography in patients with pulmonary arterial hypertension

Cardiopulmonary hemodynamics are estimated by Doppler echocardiogram (ECHO) and measured by right heart catheterization (RHC) in patients with pulmonary arterial hypertension (PAH). Whether there is a correlation between these measurements is controversial. The authors investigated ECHO and RHC in patients enrolled in the Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL), a multicenter, observational, US-based study designed to provide current information about patients with PAH. Patients with PAH who had an ECHO and RHC within 12 months of each other were included. Correlation between subsequent ECHO and RHC was also investigated. Of 2967 patients, 2838 were 18 years and older at enrollment and 1883 had an RHC within 12 months of an ECHO. Correlations between ECHO-estimated and RHC-measured pulmonary artery systolic pressures (PASPs) and mean right atrial pressures did not change based on temporal proximity of the two baseline studies, whether they occurred on the same day or were separated by up to 12 months. In contrast, there was little correlation of serial measurements between ECHO and RHC. Although there is good correlation in PASP between ECHO and RHC at baseline, repeat ECHO measurements alone are not sufficient to monitor change in PASP or progression of PAH.