Non-invasive algorithms for the diagnosis of pulmonary hypertension

Prevalence of pulmonary hypertension in chronic simple silicosis patients and its correlation with smoking history, occupation type, age and duration of silica exposure

Silicosis is a preventable occupational health hazard with potential for permanent physical disability and increased socio-economic burden. Pulmonary hypertension (PH) secondary to chronic respiratory diseases signifies poorer prognosis and transthoracic echocardiography (TTE) has proven its usefulness as a screening tool for PH diagnosis. The objectives were to determine PH prevalence in chronic simple silicosis patients through TTE screening and correlate PH prevalence with smoking status, occupation type, age and duration of silica exposure (DSE). We enrolled 104 patients in the study based on occupational exposure to silica dust and radiologic confirmation of chronic simple silicosis. The study sample was divided into significant smokers (SS group) and insignificant smokers (InS group) on the basis of ≥10 pack years smoking history, and into drillers and dressers based on occupation type. TTE examination was performed to measure resting mean pulmonary artery pressure (mPAP) and the patients were classified into: no PH (mPAP≤20 mm Hg), borderline PH (mPAP>20 and <25 mmHg), and PH (mPAP≥25). PH prevalence was 25% in study subjects (26/104); 29.6% (16/54) among SS group versus 20% (10/50) among InS group (.52) ; and 34.2% (14/41) among drillers versus 19.1% (12/63) among dressers (p=.024). Mean age and mean duration of silica exposure among SS and InS groups were comparatively similar, while they had lower values among dressers against dressers with no statistical significance. Logistic regression analysis established a significant association of PH prevalence with higher age in the study sample, SS group and drillers group, while a significant association of PH prevalence with longer DSE was only seen in the study sample. PH prevalence was significantly associated (p=.007) with SS-driller group on comparing TTE findings with combined smoking and occupation type based groups. This study has shown PH prevalence in chronic simple silicosis patients at alarming levels, having associations with driller occupation, older age and longer DSE with varying results among groups and complex interplay with smoking exposure, suggesting the need for large sample-based molecular and genetic studies. Including TTE in the initial work-up of silicosis patients will promote timely intervention and reduce morbidity and mortality with a high benefit-cost ratio.

Pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare and progressive disease characterised by remodelling of the pulmonary arteries and progressive narrowing of the pulmonary vasculature. This leads to a progressive increase in pulmonary vascular resistance and pulmonary arterial pressure and, if left untreated, to right ventricular failure and death. A correct diagnosis requires a complete work-up including right heart catheterisation performed in a specialised centre. Although our knowledge of the epidemiology, pathology and pathophysiology of the disease, as well as the development of innovative therapies, has progressed in recent decades, PAH remains a serious clinical condition. Current treatments for the disease target the three specific pathways of endothelial dysfunction that characterise PAH: the endothelin, nitric oxide and prostacyclin pathways. The current treatment algorithm is based on the assessment of severity using a multiparametric risk stratification approach at the time of diagnosis (baseline) and at regular follow-up visits. It recommends the initiation of combination therapy in PAH patients without cardiopulmonary comorbidities. The choice of therapy (dual or triple) depends on the initial severity of the condition. The main treatment goal is to achieve low-risk status. Further escalation of treatment is required if low-risk status is not achieved at subsequent follow-up assessments. In the most severe patients, who are already on maximal medical therapy, lung transplantation may be indicated. Recent advances in understanding the pathophysiology of the disease have led to the development of promising emerging therapies targeting dysfunctional pathways beyond endothelial dysfunction, including the TGF-β and PDGF pathways.

Improving on the diagnostic characteristics of echocardiography for pulmonary hypertension

This retrospective study evaluated the diagnostic characteristics of a combination of echocardiographic parameters for pulmonary hypertension (PH). Right ventricular systolic pressure (RVSP) estimation by echocardiography (echo) is used to screen for PH. However, the sensitivity of this method is suboptimal. We hypothesized that RVSP estimation in conjunction with other echo parameters would improve the value of echo for PH. The Duke Echo database was queried for adult patients with known or suspected PH who had undergone both echo and right heart catheterization (RHC) within a 24 h period between 1/1/2008 and 12/31/2013. Patients with complex congenital heart disease, heart transplantation, ventricular assist device, or on mechanical ventilation at time of study were excluded. Diagnostic characteristics of several echo parameters (right atrial enlargement, pulmonary artery (PA) enlargement, RV enlargement, RV dysfunction, and RVSP) for PH (mean PA pressure 25 mmHg on RHC) were evaluated among 1007 patients. RVSP ≥40 had a sensitivity of 77% (accuracy 77), while RVSP ≥35 had the highest sensitivity at 88% (81% accuracy). PA enlargement had the lowest sensitivity at 17%. The area under the curve (AUC) for RVSP was 0.844. A model including RVSP, RA, PA, RV enlargement and RV dysfunction had a higher AUC (AUC = 0.87) than RVSP alone. The value of echo as a screening test for PH is improved by a model incorporating a lower RVSP in addition to other right heart parameters. These findings need to be validated in prospective cohorts.

Pulmonary hypertension associated with left-sided heart disease

Pulmonary hypertension associated with left-sided heart disease (PH-LHD) is the most common type of pulmonary hypertension. In patients with left-sided heart disease, the presence of pulmonary hypertension is typically a marker of more advanced disease, more severe symptoms, and worse prognosis. In contrast to pulmonary arterial hypertension, PH-LHD is characterised by an elevated pulmonary artery wedge pressure (postcapillary pulmonary hypertension) without or with an additional precapillary component (isolated postcapillary vs combined postcapillary and precapillary pulmonary hypertension). Transthoracic echocardiography is the primary noninvasive imaging tool to estimate the probability of pulmonary hypertension and to establish a working diagnosis on the mechanism of pulmonary hypertension. However, right heart catheterisation is always required if significant pulmonary hypertension is suspected and exact knowledge of the haemodynamic constellation is necessary. The haemodynamic constellation (mean pulmonary artery pressure, mean pulmonary artery wedge pressure, left ventricular end-diastolic pressure) in combination with clinical information and imaging findings (mainly echocardiography, coronary angiography and cardiac magnetic resonance imaging) will usually allow the exact mechanism underlying PH-LHD to be defined, which is a prerequisite for appropriate treatment. The general principle for the management of PH-LHD is to treat the underlying left-sided heart disease in an optimal manner using drugs and/or interventional or surgical therapy. There is currently no established indication for pulmonary arterial hypertension-specific therapies in PH-LHD, and specific therapies may even cause harm in patients with PH-LHD.

The Role of Echocardiography in the Evaluation of Pulmonary Arterial Hypertension

The evaluation of pulmonary arterial hypertension (PAH) requires a multimodality approach that combines invasive and noninvasive imaging studies to ensure accurate diagnosis and classification. Given the complexity of the hemodynamic relationships between the left heart, pulmonary circulation, and right heart, the diagnosis of PAH is often a challenging task. Right heart catheterization is the gold standard for diagnosis, providing the hemodynamic information that defines the disease. Nonetheless, echocardiography continues to be a valuable tool in the approach to the patient with suspected PAH. Echocardiographic assessment generates a wealth of information about the response of the right heart to elevated pulmonary pressures and provides essential diagnostic and prognostic data to the clinician. Numerous measurements can be used to identify alterations in right heart morphology, pressure, and function; although each variable in isolation may have little utility, meaningful information is revealed when multiple parameters are considered together. In this article, we will review the echocardiographic measurements employed in assessment of the right heart and seek to clarify the role of echocardiography in the diagnostic workup of PAH.

Advanced imaging tools rather than hemodynamics should be the primary approach for diagnosing, following, and managing pulmonary arterial hypertension

Pulmonary hypertension (PH) is currently defined based on invasive measurements: a resting pulmonary artery pressure ≥ 25 mm Hg. For pulmonary arterial hypertension, a pulmonary arterial wedge pressure ≤ 15 mm Hg and pulmonary vascular resistance > 3 Wood units are also required. Thus, right heart catheterization is inevitable at present. However, the diagnosis, follow-up, and management of PH by noninvasive techniques is progressing. Significant advances have been achieved in the imaging of pulmonary vascular disease and the right ventricle. We review the current sensitivities and specificities of noninvasive imaging of PH and discuss its role and future potential to replace hemodynamics as the primary approach to screening, diagnosing, and following/managing PH.