Imaging of Pulmonary Hypertension
2019; Elsevier BV; Volume: 156; Issue: 2 Linguagem: Inglês
10.1016/j.chest.2019.04.003
ISSN1931-3543
AutoresErica Altschul, Martine Rémy-Jardin, Stephen Machnicki, Roxana Sulica, Jonathan Moore, Anup Singh, Suhail Raoof,
Tópico(s)Cardiovascular Function and Risk Factors
ResumoPulmonary hypertension (PH) is an end result of a diverse array of complex clinical conditions that invoke hemodynamic and pathophysiological changes in the pulmonary vasculature. Many patients' symptoms begin with dyspnea on exertion for which screening tests such as chest roentgenograms and more definitive noninvasive tests such as CT scans are ordered initially. It is imperative that clinicians are cognizant of subtle clues on these imaging modalities that alert them to the possibility of PH. These clues may serve as a stepping stone towards more advanced noninvasive (echocardiogram) and invasive (right heart catheterization) testing. On the CT scan, the signs are classified into mediastinal and lung parenchymal abnormalities. In addition to suspecting the diagnosis of PH, this paper provides a pictorial essay to guide health care professionals in identifying the etiology of PH. This paper also provides concrete definitions, wherever possible, of what constitutes abnormalities in PH, such as dilated pulmonary arteries, pruning of vessels, and increased thickness of free wall of the right ventricle. The sensitivities and specificities of each sign are enumerated. The common radiographic and clinical features of many different etiologies of PH are tabulated for the convenience of the readers. Some newer imaging modalities such as dual-energy CT of the chest that hold promise for the future are also described. Pulmonary hypertension (PH) is an end result of a diverse array of complex clinical conditions that invoke hemodynamic and pathophysiological changes in the pulmonary vasculature. Many patients' symptoms begin with dyspnea on exertion for which screening tests such as chest roentgenograms and more definitive noninvasive tests such as CT scans are ordered initially. It is imperative that clinicians are cognizant of subtle clues on these imaging modalities that alert them to the possibility of PH. These clues may serve as a stepping stone towards more advanced noninvasive (echocardiogram) and invasive (right heart catheterization) testing. On the CT scan, the signs are classified into mediastinal and lung parenchymal abnormalities. In addition to suspecting the diagnosis of PH, this paper provides a pictorial essay to guide health care professionals in identifying the etiology of PH. This paper also provides concrete definitions, wherever possible, of what constitutes abnormalities in PH, such as dilated pulmonary arteries, pruning of vessels, and increased thickness of free wall of the right ventricle. The sensitivities and specificities of each sign are enumerated. The common radiographic and clinical features of many different etiologies of PH are tabulated for the convenience of the readers. Some newer imaging modalities such as dual-energy CT of the chest that hold promise for the future are also described. Pulmonary hypertension (PH) encompasses a composite of pulmonary and cardiac diseases that affect the pulmonary vasculature. It is defined by the European Society of Cardiology/European Respiratory Society guidelines as an elevation in the mean pulmonary artery pressure (mPAP) ≥25 mm Hg measured by right heart catheterization (RHC)1Galie N. Humbert M. Vachiery J.L. et al.2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: the Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS): Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC), International Society for Heart and Lung Transplantation (ISHLT).Eur Heart J. 2016; 37: 67-119Crossref PubMed Scopus (2944) Google Scholar; however, this well-known definition is thought to inadequately capture patients with PH, specifically those with early PH. Additionally, it includes patients that may have postcapillary PH. The World Symposium on Pulmonary Hypertension Task Force recently proposed changing the definition of precapillary PH to an mPAP >20 mm Hg and pulmonary vascular resistance ≥3 Woods unit.2Simonneau G. Montani D. Celermajer D.S. et al.Haemodynamic definitions and updated clinical classification of pulmonary hypertension.Eur Respir J. 2019; 53 (pii: 1801913)Crossref Scopus (948) Google Scholar The etiology of PH can be categorized into five groups (Table 1). Dividing PH into precapillary and postcapillary with RHC measurements can guide a clinician to pulmonary, systemic, or cardiac causes, but overlap between groups is common. The incidence of PH differs per group and the combined incidence is unknown. Approximately 200,000 hospitalizations occur annually with a diagnosis of primary or secondary PH.3Graham B.B. Bandeira A.P. Morrell N.W. Butrous G. Tuder R.M. Schistosomiasis-associated pulmonary hypertension: pulmonary vascular disease: the global perspective.Chest. 2010; 137: 20S-29SAbstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar It is widely accepted that left heart disease (group 2) is the most common cause of elevated pulmonary artery pressures in the United States,1Galie N. Humbert M. Vachiery J.L. et al.2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: the Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS): Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC), International Society for Heart and Lung Transplantation (ISHLT).Eur Heart J. 2016; 37: 67-119Crossref PubMed Scopus (2944) Google Scholar whereas schistosomiasis is the most common cause of PH in the developing world.3Graham B.B. Bandeira A.P. Morrell N.W. Butrous G. Tuder R.M. Schistosomiasis-associated pulmonary hypertension: pulmonary vascular disease: the global perspective.Chest. 2010; 137: 20S-29SAbstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar Although the definitive diagnosis of PH is made with RHC, there are imaging clues to suggest PH and its causes. Although findings may be nonspecific, 90% of patients with idiopathic PAH (IPAH) will have an abnormal chest radiograph at the time of diagnosis.1Galie N. Humbert M. Vachiery J.L. et al.2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: the Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS): Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC), International Society for Heart and Lung Transplantation (ISHLT).Eur Heart J. 2016; 37: 67-119Crossref PubMed Scopus (2944) Google Scholar CT imaging of the chest can not only suggest the diagnosis of PH, but also can evaluate vascular, cardiac, parenchymal, and mediastinal abnormalities that can help determine the etiology. The aim of this paper is to help provide a pictorial essay to guide pulmonologists when to suspect PH and to look for clues on imaging studies that may shed light on the underlying etiologies. In this approach, a close collaboration between clinicians and radiologists is imperative for optimal extraction and analysis of the data.Table 1Updated Clinical Classification of PHAdapted From ERS (2018).2Simonneau G. Montani D. Celermajer D.S. et al.Haemodynamic definitions and updated clinical classification of pulmonary hypertension.Eur Respir J. 2019; 53 (pii: 1801913)Crossref Scopus (948) Google Scholar Reproduced with permission of the © ERS 2019: European Respiratory Journal 53(1): 1801913; https://doi.org/10.1183/13993003.01913-2018. Published 24 January 2019.1.PAHa.Idiopathic PAHb.Heritable PAHc.Drug- and toxin-induced PAHd.PAH associated with:i.CTDii.HIV infectioniii.Portal hypertensioniv.Congenital heart diseasev.Schistosomiasise.PAH long-term responders to calcium channel blockersf.PAH with overt features of venous/capillaries (PVOD/PCH) involvementg.Persistent PH of the newborn syndrome2.PH resulting from left heart diseasea.PH from heart failure with preserved LVEFb.PH from heart failure with reduced LVEFc.Valvular heart diseased.Congenital/acquired cardiovascular conditions leading to postcapillary PH3.PH from lung diseases and/or hypoxiaa.Obstructive lung diseaseb.Restrictive lung diseasec.Other lung disease with mixed restrictive/obstructive patternd.Hypoxia without lung diseasee.Developmental lung disorders4.PH from pulmonary artery obstructiona.CTEPHb.Other pulmonary artery obstructions5.PH with unclear and/or multifactorial mechanismsa.Hematological disordersb.Systemic and metabolic disordersc.Othersd.Complex congenital heart diseaseCTD = connective tissue disease; CTEPH = chronic thromboembolic pulmonary hypertension; ERS = European Respiratory Society; LVEF = left ventricular ejection fraction; PAH = pulmonary arterial hypertension; PCH = pulmonary capillary hemangiomatosis; PH = pulmonary hypertension; PVOD = pulmonary veno-occlusive disease. Open table in a new tab CTD = connective tissue disease; CTEPH = chronic thromboembolic pulmonary hypertension; ERS = European Respiratory Society; LVEF = left ventricular ejection fraction; PAH = pulmonary arterial hypertension; PCH = pulmonary capillary hemangiomatosis; PH = pulmonary hypertension; PVOD = pulmonary veno-occlusive disease. The chest radiograph is an easy and often overlooked investigation in the assessment of PH. The American College of Chest Physicians recommends obtaining a chest radiograph for the assessment of patients suspected of having PAH because of the clinical clues it can provide.4McGoon M. Gutterman D. Steen V. et al.Screening, early detection, and diagnosis of pulmonary arterial hypertension: ACCP evidence-based clinical practice guidelines.Chest. 2004; 126: 14S-34SAbstract Full Text Full Text PDF PubMed Scopus (688) Google Scholar An enlarged right ventricle (RV) and right atrium are commonly associated with elevated pulmonary artery (PA) pressures and can be evaluated on chest radiography. The cardiothoracic ratio, defined as the ratio of the maximum transverse diameter of the heart to the maximal internal diameter of the thoracic cavity on a PA film, has long been used to assess cardiomegaly,5Mensah Y.B. Mensah K. Asiamah S. et al.Establishing the cardiothoracic ratio using chest radiographs in an indigenous Ghanaian population: a simple tool for cardiomegaly screening.Ghana Med J. 2015; 49: 159-164Crossref PubMed Scopus (14) Google Scholar but it is important to understand which chambers form the border of the heart. The right heart border is formed by the right atrium6Boyars M. Chest roentgenography for pulmonary evaluation. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd ed. Boston: Butterworths; 1990.Google Scholar and, therefore, its enlargement will manifest as more than 44 mm from the midline to the prominent right heart border (Fig 1A).7Mirsadraee M. Nazemi S. Hamedanchi A. Naghibi S. Simple screening of pulmonary artery hypertension using standard chest x ray: an old technique, new landmark.Tanaffos. 2013; 12: 17-22PubMed Google Scholar, 8Murphy J.G. Lloyd M.A. Clinic Mayo Mayo Clinic Cardiology: Concise Textbook.4th ed. Mayo Clinic Scientific Press/Oxford University Press, Oxford2013Google Scholar The RV is better visualized on a lateral film; its dilation is suggested when there is filling of the retrosternal space (Fig 2).6Boyars M. Chest roentgenography for pulmonary evaluation. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd ed. Boston: Butterworths; 1990.Google Scholar A boot-shaped heart with upward tilt of the cardiac apex can represent RVH.9Ferguson E.C. Krishnamurthy R. Oldham S.A. Classic imaging signs of congenital cardiovascular abnormalities.Radiographics. 2007; 27: 1323-1334Crossref PubMed Scopus (49) Google ScholarFigure 2A, Lateral chest radiograph demonstrating fullness of the retrosternal space (arrow) commonly seen in right ventricular enlargement on the left. B, Normal lateral chest radiograph provided on the right for comparison.View Large Image Figure ViewerDownload Hi-res image Download (PPT) A prominent main pulmonary artery, found just below and to the left of the aortic knob, is commonly seen in patients with PH.10Raoof S. Feigin D. Sung A. Raoof S. Irugulpati L. Rosenow III, E.C. Interpretation of plain chest roentgenogram.Chest. 2012; 141: 545-558Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar Elevated PA pressures have also been associated with enlargement of the right descending pulmonary artery (RDPA) and left descending pulmonary artery (LDPA). Matthay et al12Matthay R.A. Schwarz M.I. Ellis Jr., J.H. et al.Pulmonary artery hypertension in chronic obstructive pulmonary disease: determination by chest radiography.Invest Radiol. 1981; 16: 95-100Crossref PubMed Scopus (67) Google Scholar assessed patients with severe COPD and PH, comparing the RDPA and LDPA size with measurement of mPAP. There is a statistically significant correlation with a RDPA ≥16 mm and LDPA ≥18 mm and the presence of PH. If both the LDPA and RDPA were enlarged on chest radiography, the positive predictive value of detecting PH was 93% (Fig 3). The RDPA and LDPA are not always visualized easily on frontal and lateral films, but measurement of the hilum and the hilum to chest ratio may be more easily obtainable. An absolute measurement of the hilum ≥112 mm was associated with a sensitivity of 82% in detecting elevated pulmonary artery systolic pressure. A ratio of hilum to chest diameter ≥0.44 had an even greater sensitivity of 86% (Fig 1B).7Mirsadraee M. Nazemi S. Hamedanchi A. Naghibi S. Simple screening of pulmonary artery hypertension using standard chest x ray: an old technique, new landmark.Tanaffos. 2013; 12: 17-22PubMed Google Scholar The thinning out of vascular markings on a chest film also suggests elevation of pulmonary pressures and vascular remodeling, referred to as vascular pruning.13Kasper D.L. Harrison's Principles of Internal Medicine. 19th ed.. McGraw Hill Education, New York2015Google Scholar This is thought to be due to vascular remodeling of the pulmonary arteries (Fig 4). Although chest radiograph can be useful for clinicians to pick up clues and suspect PH, there are many limitations and findings may be nonspecific. Clues to PH are better delineated on chest CT scan; chest CT scans should be evaluated in all patients suspected of having PH. Similar to chest radiograph, a dilated PA can be a clue to elevated PA pressures and is more easily measured on a CT scan. It is important to note that there are many causes for a dilated PA, and its presence does not confirm PH. For example, a dilated PA can be seen in conditions other than PH, such as high altitude, vasculitis, or idiopathic.14Ascha M. Renapurkar R.D. Tonelli A.R. A review of imaging modalities in pulmonary hypertension.Ann Thorac Med. 2017; 12: 61-73Crossref PubMed Scopus (23) Google Scholar, 15Raymond T.E. Khabbaza J.E. Yadav R. Tonelli A.R. Significance of main pulmonary artery dilation on imaging studies.Ann Am Thorac Soc. 2014; 11: 1623-1632Crossref PubMed Scopus (39) Google Scholar, 16Lewis G. Hoey E.T. Reynolds J.H. Ganeshan A. Ment J. Multi-detector CT assessment in pulmonary hypertension: techniques, systematic approach to interpretation and key findings.Quant Imaging Med Surg. 2015; 5: 423-432PubMed Google Scholar The best location to measure the PA is at the level of the PA bifurcation perpendicular to its long axis.15Raymond T.E. Khabbaza J.E. Yadav R. Tonelli A.R. Significance of main pulmonary artery dilation on imaging studies.Ann Am Thorac Soc. 2014; 11: 1623-1632Crossref PubMed Scopus (39) Google Scholar, 16Lewis G. Hoey E.T. Reynolds J.H. Ganeshan A. Ment J. Multi-detector CT assessment in pulmonary hypertension: techniques, systematic approach to interpretation and key findings.Quant Imaging Med Surg. 2015; 5: 423-432PubMed Google Scholar On CT angiograph, it is the vascular lumen that should be measured; on non-contrast CT scans the vessel wall is included.15Raymond T.E. Khabbaza J.E. Yadav R. Tonelli A.R. Significance of main pulmonary artery dilation on imaging studies.Ann Am Thorac Soc. 2014; 11: 1623-1632Crossref PubMed Scopus (39) Google Scholar Many studies have assessed what a normal PA diameter is on chest CT.15Raymond T.E. Khabbaza J.E. Yadav R. Tonelli A.R. Significance of main pulmonary artery dilation on imaging studies.Ann Am Thorac Soc. 2014; 11: 1623-1632Crossref PubMed Scopus (39) Google Scholar It is generally accepted that a PA ≥29 mm in males and ≥27 mm in females is considered to represent abnormal dilation based on the results of the Framingham study.16Lewis G. Hoey E.T. Reynolds J.H. Ganeshan A. Ment J. Multi-detector CT assessment in pulmonary hypertension: techniques, systematic approach to interpretation and key findings.Quant Imaging Med Surg. 2015; 5: 423-432PubMed Google Scholar, 17Tan R.T. Kuzo R. Goodman L.R. Siegel R. Haasler G.B. Presberg K.W. Utility of CT scan evaluation for predicting pulmonary hypertension in patients with parenchymal lung disease. Medical College of Wisconsin Lung Transplant Group.Chest. 1998; 113: 1250-1256Abstract Full Text Full Text PDF PubMed Scopus (278) Google Scholar, 18Grosse C. Grosse A. CT findings in diseases associated with pulmonary hypertension: a current review.Radiographics. 2010; 30: 1753-1777Crossref PubMed Scopus (100) Google Scholar, 19Pena E. Dennie C. Veinot J. Muniz S.H. Pulmonary hypertension: how the radiologist can help.Radiographics. 2012; 32: 9-32Crossref PubMed Scopus (78) Google Scholar Although the correlation may vary depending on the etiology of PH, there remains a moderate to strong correlation of PA diameter with PH20Shin S. King C.S. Brown A.W. et al.Pulmonary artery size as a predictor of pulmonary hypertension and outcomes in patients with chronic obstructive pulmonary disease.Respir Med. 2014; 108: 1626-1632Abstract Full Text Full Text PDF PubMed Scopus (44) Google Scholar; however, the ability to determine a "cutoff" mark has been more difficult.21Haimovici J.B. Trotman-Dickenson B. Halpern E.F. et al.Relationship between pulmonary artery diameter at computed tomography and pulmonary artery pressures at right-sided heart catheterization. Massachusetts General Hospital Lung Transplantation Program.Acad Radiol. 1997; 4: 327-334Abstract Full Text PDF PubMed Scopus (87) Google Scholar According to the Framingham study, a ratio of PA/aorta (PA/Ao) of 0.91 is found to be within the 90th percentile of healthy subjects. This suggests a ratio >.90 is associated with PH,15Raymond T.E. Khabbaza J.E. Yadav R. Tonelli A.R. Significance of main pulmonary artery dilation on imaging studies.Ann Am Thorac Soc. 2014; 11: 1623-1632Crossref PubMed Scopus (39) Google Scholar which was also confirmed by a retrospective study that found a ratio >1 correlated with mPAP >20 mm Hg, with a specificity of 96%14Ascha M. Renapurkar R.D. Tonelli A.R. A review of imaging modalities in pulmonary hypertension.Ann Thorac Med. 2017; 12: 61-73Crossref PubMed Scopus (23) Google Scholar, 15Raymond T.E. Khabbaza J.E. Yadav R. Tonelli A.R. Significance of main pulmonary artery dilation on imaging studies.Ann Am Thorac Soc. 2014; 11: 1623-1632Crossref PubMed Scopus (39) Google Scholar (Fig 5) and a positive predictive value of >95%.18Grosse C. Grosse A. CT findings in diseases associated with pulmonary hypertension: a current review.Radiographics. 2010; 30: 1753-1777Crossref PubMed Scopus (100) Google Scholar For patients younger than age 50 years, the ratio of PA/Ao correlated more strongly with mean PA pressure than the diameter of the main PA, and vice versa for patients older than 50 years.22Truong Q.A. Massaro J.M. Rogers I.S. et al.Reference values for normal pulmonary artery dimensions by noncontrast cardiac computed tomography: the Framingham Heart Study.Circ Cardiovasc Imaging. 2012; 5: 147-154Crossref PubMed Scopus (162) Google Scholar In fact, a ratio of PA/Ao diameter may be able to predict the mPAP by using the equation 3.7 + (24 × PA diameter/aortic diameter).15Raymond T.E. Khabbaza J.E. Yadav R. Tonelli A.R. Significance of main pulmonary artery dilation on imaging studies.Ann Am Thorac Soc. 2014; 11: 1623-1632Crossref PubMed Scopus (39) Google Scholar Average sensitivity and specificity for PH based on dilated PA is 71.9%.14Ascha M. Renapurkar R.D. Tonelli A.R. A review of imaging modalities in pulmonary hypertension.Ann Thorac Med. 2017; 12: 61-73Crossref PubMed Scopus (23) Google Scholar This improves to nearly 100% if the main pulmonary artery is ≥29 mm and the segmental artery to bronchus ratio is >1:1 in three of four pulmonary lobes (Fig 6).14Ascha M. Renapurkar R.D. Tonelli A.R. A review of imaging modalities in pulmonary hypertension.Ann Thorac Med. 2017; 12: 61-73Crossref PubMed Scopus (23) Google Scholar, 17Tan R.T. Kuzo R. Goodman L.R. Siegel R. Haasler G.B. Presberg K.W. Utility of CT scan evaluation for predicting pulmonary hypertension in patients with parenchymal lung disease. Medical College of Wisconsin Lung Transplant Group.Chest. 1998; 113: 1250-1256Abstract Full Text Full Text PDF PubMed Scopus (278) Google Scholar, 23Barbosa Jr., E.J. Gupta N.K. Torigian D.A. Gefter W.B. Current role of imaging in the diagnosis and management of pulmonary hypertension.AJR Am J Roentgenol. 2012; 198: 1320-1331Crossref PubMed Scopus (19) Google Scholar A normal PA diameter does not rule out the diagnosis of PH. The presence of PA/Ao ratio >1 on CT scan can also be helpful in patients who do not have adequate views on echocardiogram to screen for PA. For example, even patients with COPD, who not uncommonly have poor acoustic windows, have PH on RHC 83% of the time if they have a PA/Ao >1.24Iyer A.S. Wells J.M. Vishin S. Bhatt S.P. Wille K.M. Dransfield M.T. CT scan-measured pulmonary artery to aorta ratio and echocardiography for detecting pulmonary hypertension in severe COPD.Chest. 2014; 145: 824-832Abstract Full Text Full Text PDF PubMed Scopus (101) Google Scholar Although the size of the PA can be useful in diagnosing patients with PH, it has been found to continue increasing in size without relation to the pressure of the PA and should not be used for estimating PA pressure during routine follow-up.25Boerrigter B. Mauritz G.J. Marcus J.T. et al.Progressive dilatation of the main pulmonary artery is a characteristic of pulmonary arterial hypertension and is not related to changes in pressure.Chest. 2010; 138: 1395-1401Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar Whereas many studies have evaluated static findings on CT scan that suggest PH, some dynamic parameters are accessible on routine CT angiographic examinations. They are based on the fact that an elevated pulmonary pressure will lead to hemodynamic changes affecting IV contrast flow in central pulmonary arteries.26Siegel Y. Mirpuri T. Pulmonary hypertension detection using dynamic and static measurable parameters on CT angiography.J Comput Assist Tomogr. 2014; 38: 586-590Crossref PubMed Scopus (6) Google Scholar•As pressures rise in pulmonary artery, back pressure will cause increased pooling of IV contrast at the prearteriolar level of the pulmonary bed, increasing density in the main pulmonary artery (Fig 7). Additionally, this can cause increased IV transit time, leading to relatively late aortic opacification and an elevated pulmonary artery/thoracic aorta ratio. These findings are only accessible for injection protocols triggering data acquisition with a region of-interest positioned within the pulmonary trunk.•PA distensibility is reduced in patients with PH. This is calculated by the change in cross-sectional area of the right pulmonary artery during systole and diastole can but can only be measured using ECG-gated CT acquisitions.27Revel M.P. Faivre J.B. Remy-Jardin M. Delannoy-Deken V. Duhamel A. Remy J. Pulmonary hypertension: ECG-gated 64-section CT angiographic evaluation of new functional parameters as diagnostic criteria.Radiology. 2009; 250: 558-566Crossref PubMed Scopus (79) Google Scholar In normal subjects, the RV is a thin-walled chamber that has a smaller diameter than the left ventricle (LV). As pulmonary pressures increase, the RV begins to hypertrophy to maintain stroke volume and cardiac output.19Pena E. Dennie C. Veinot J. Muniz S.H. Pulmonary hypertension: how the radiologist can help.Radiographics. 2012; 32: 9-32Crossref PubMed Scopus (78) Google Scholar It can eventually dilate and fail. The changes in the RV on chest CT include the following. The RV muscle mass increase can be measured on CT scan. In general, the normal thickness of the RV free wall is 1:1. A ratio of ≥1.28 was associated with a sensitivity and specificity of 85.7% and 86.1%, respectively (Fig 8).29Chan A.L. Juarez M.M. Shelton D.K. et al.Novel computed tomographic chest metrics to detect pulmonary hypertension.BMC Med Imaging. 2011; 11: 7Crossref PubMed Scopus (66) Google Scholar •Straightening/bowing. In healthy patients, the interventricular septum (IVS) should have a convex shape with bowing into the RV. As the pressures on the right side of the heart rise, the IVS begins to flatten and even reverse its convexity (Fig 8).23Barbosa Jr., E.J. Gupta N.K. Torigian D.A. Gefter W.B. Current role of imaging in the diagnosis and management of pulmonary hypertension.AJR Am J Roentgenol. 2012; 198: 1320-1331Crossref PubMed Scopus (19) Google Scholar Once the IVS begins impeding on the LV, cardiac output is compromised. Patients with an mPAP ≥30 mm Hg have been found to have leftward deviation of the IVS into the LV (Fig 8).14Ascha M. Renapurkar R.D. Tonelli A.R. A review of imaging modalities in pulmonary hypertension.Ann Thorac Med. 2017; 12: 61-73Crossref PubMed Scopus (23) Google Scholar•Septal angle. The septal angle, defined as the angle between the IVS and a line drawn from the sternum midpoint to thoracic spinous process, increases with RV overload.14Ascha M. Renapurkar R.D. Tonelli A.R. A review of imaging modalities in pulmonary hypertension.Ann Thorac Med. 2017; 12: 61-73Crossref PubMed Scopus (23) Google Scholar In fact, a septal angle >135 can predict PH with a sensitivity of 100% and specificity of 79%.30Hussain N. Capener D. Elliot C. et al.Interventricular septal angle can be used to predict which patients have combined postcapillary or precapillary pulmonary hypertension in left heart disease. J Cardiovasc Magn Reson... 2015; 17: P338Google Scholar Pericardial effusions can also be seen with PH of any etiology, but remains a nonspecific finding.16Lewis G. Hoey E.T. Reynolds J.H. Ganeshan A. Ment J. Multi-detector CT assessment in pulmonary hypertension: techniques, systematic approach to interpretation and key findings.Quant Imaging Med Surg. 2015; 5: 423-432PubMed Google Scholar Presence of a pericardial effusion in the setting of PH has been associated with a worse prognosis.18Grosse C. Grosse A. CT findings in diseases associated with pulmonary hypertension: a current review.Radiographics. 2010; 30: 1753-1777Crossref PubMed Scopus (100) Google Scholar In patients with connective-tissue disease PAH, inflammatory etiology of pericardial effusion is also possible, as demonstrated by higher prevalence of moderately large pericardial effusions in this group of patients (Fig 9).31Fenstad E.R. Le R.J. Sinak L.J. et al.Pericardial effusions in pulmonary arterial hypertension: characteristics, prognosis, and role of drainage.Chest. 2013; 144: 1530-1538Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar In the context of suspected or confirmed PH, the clinician can begin to look for clues in an effort to suspect etiology of PH. Some of the common etiologies and their radiologic features are summarized (Table 2).Table 2Clinical Conditions Associated With PH and Their Corresponding Imaging FindingsClinical DiseasePH WHO ClassificationFindings on ImagingPulmonary arterial hypertensionGroup 1Patchy ill-defined nodules, RV dilation possible, deviated IVS, mosaic attenuationCollagen vascular disorderGroup 1Ill-defined micronodules, traction bronchiectasis, increased reticular markingsPortopulmonary hypertensionGroup 1Dilated pulmonary artery, esophageal varices, increased pulmonary to bronchus ratiosAtrial septal defect/ventricular septal defectGroup 1Direct visualization of septal defect, left to right intracardiac contrast shuntingPulmonary arteriovenous malformationsGroup 1Rounded pulmonary opacities, feeding artery, and draining veinPulmonary veno-occlusive
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