Computed tomography and magnetic resonance imaging of pulmonary hypertension: Pulmonary vessels and right ventricle

Use of small pulmonary vascular alterations to identify different types of pulmonary hypertension: a quantitative computed tomography analysis

BACKGROUND

The morphological alterations of small pulmonary vessels measured by computed tomography (CT) is increasingly used in evaluation of suspected pulmonary hypertension (PH).

OBJECTIVE

To investigate the significance alterations of quantitative assessment of small pulmonary vessels on chest CT in distinguishing different types of PH and their severity.

METHODS

We retrospectively analyzed a dataset of 120 healthy controls (HCs) and 91 PH patients, including 34 patients with connective tissue diseases-related PH (CTD-PH), 26 patients with idiopathic pulmonary arterial hypertension (iPAH), and 31 patients with chronic obstructive pulmonary disease-related PH (COPD-PH). The CTD-PH patients were divided into mild to moderate PH (CTD-LM-PH) group (n = 17) and severe PH (CTD-S-PH) group (n = 17). A total of 53 CTD patients without PH (CTD-nPH) were enrolled for comparison with the CTD-PH. We measured the cross-sectional area of small pulmonary vessels < 5 mm2 (%CSA <5) and between 5-10 mm2 (%CSA5-10) as a percentage of total lung area among the populations included above and compared %CSA in different types of PH groups and HCs group. The mean pulmonary arterial pressure (mPAP) was measured by right heart catheterization.

RESULTS

The %CSA5-10 of COPD-PH, CTD-PH, and iPAH patients increased (0.21±0.09, 0.49±0.20 and 0.61±0.20, p < 0.02) sequentially, while the %CSA <5 of CTD-PH, iPAH, and COPD-PH patients decreased (0.79±0.65, 0.65±0.38 and 0.52±0.27, p < 0.05) sequentially. The %CSA5-10 was significantly higher in CTD-S-PH patients than CTD-LM-PH patients and CTD-nPH patients (0.51±0.21, 0.31±0.15 and 0.28±0.12, p < 0.01). The %CSA5-10 was positively correlated with mPAP in the CTD-PH group.

CONCLUSIONS

The quantitative parameters %CSA <5 and %CSA5-10 assessed by chest CT are useful for distinguishing different types of PH. In addition, the %CSA5-10 can provide information for identification of CTD-PH severity.

Pulmonary Artery Size Measurements: A Comparison Study Between Electrocardiogram-Gated and Nonelectrocardiogram-Gated Computed Tomography

OBJECTIVES

The aim of this study was to determine the difference and correlation in pulmonary artery (PA) size when measured from the electrocardiogram (ECG)-gated computed tomography (CT) and non-ECG-gated CT.

METHODS

In the retrospective study, 279 patients who underwent both ECG-gated CT and non-ECG-gated CT were enrolled. Maximum and minimum diameters of main pulmonary artery (MPA), right pulmonary artery (RPA), and ascending aorta (AAO) were measured, whereas mean diameters of MPA and RPA were obtained. The same PA size parameters were also measured on non-ECG-gated CT.

RESULTS

There was a significant difference in maximum and minimum PA diameters between ECG-gated CT and non-ECG-gated CT, whereas mean PA diameters showed no statistically difference. The PA parameters showed a strong positive correlation between these 2 examinations.

CONCLUSIONS

The PA size was different between ECG-gated CT and non-ECG-gated CT, whereas the PA size parameters on non-ECG-gated CT could be used to predict those with ECG-gated CT, which allow for confident prediction of pulmonary hypertension and guide further surgical intervention.

Renal protective effect of sodium ferulate on pulmonary hypertension patients undergoing computed tomography pulmonary angiography

This study aimed to explore the correlation of sodium ferulate and the renal protective effect on computed tomography pulmonary angiography in patients suffering from pulmonary hypertension. This prospective study enrolled 92 consecutive patients with pulmonary hypertension diagnosed by echocardiography, and all included patients underwent computed tomography pulmonary angiography after admission. The participants were randomized, divided into sodium ferulate group (n = 49) and control group (n = 43), of which patients in the sodium ferulate group received intravenous sodium ferulate 3.0 g per day from 12 h before computed tomography pulmonary angiography examination to 72 h after that, and patients in the control group were provided with routine treatment. Renal function was assessed by measuring serum creatinine, estimated glomerular filtration rate, Cystatin-C as well as 24 h, 48 h, and 72 h after computed tomography pulmonary angiography, followed by the calculation of the incidence of contrast-induced nephropathy for contrast-induced nephropathy and non-contrast-induced nephropathy grouping. Besides, renal resistive index was determined via Doppler ultrasound examination before, after 1 h and 24 h after computed tomography pulmonary angiography. There were no significant differences between the two groups in serum creatinine at baseline and 24 h after computed tomography pulmonary angiography (P > 0.05, respectively), but at 48 h and 72 h, it was lower in the sodium ferulate group (P < 0.05). There were no significant differences of estimated glomerular filtration rate between the two groups (P > 0.05). The level of Cystatin-C at 48 h and 72 h after computed tomography pulmonary angiography was lower than in the sodium ferulate group (P < 0.05). Contrast-induced nephropathy was identified in nine patients (9.78%). Sodium ferulate was associated with a decline in the incidence of contrast-induced nephropathy (4.08 vs. 16.28 %, P < 0.05). Compared to patients with contrast-induced nephropathy, lower renal resistive index were observed at 1 h and 24 h after computed tomography pulmonary angiography in patients without contrast-induced nephropathy (P < 0.05). Infusion of sodium ferulate before and after computed tomography pulmonary angiography was associated with a decline in incidence of contrast-induced nephropathy.

Multimodality cardiovascular imaging in pulmonary embolism

Acute pulmonary embolism (APE) is one of the leading causes of cardiovascular (CV) morbidity and mortality. To select appropriate therapeutic strategy and/or to minimize the mortality and morbidity, rapid and correct identification of life-threatening APE is very important. Also, right ventricular (RV) failure usually precedes acute hemodynamic compromise or death, and thus the identification of RV failure is another important step in risk stratification or treatment of APE. With advances in diagnosis and treatment, the prognosis of APE has been dramatically improving in most cases, but inadequate therapy or recurrent episodes of pulmonary embolism (PE) may result in negative outcomes or, so called, chronic thromboembolic pulmonary hypertension (CTEPH). CTEPH is a condition characterized by remaining chronic thromboembolic material in the pulmonary vasculature and subsequent chronic pulmonary hypertension. Various imaging modalities include chest computed tomography pulmonary angiography (CTPA), echocardiography, magnetic resonance imaging, and nuclear imaging and each are used for the assessment of varying status of PE. Assessment of thromboembolic burden by chest CTPA is the first step in the diagnosis of PE. Hemodynamic assessment can be achieved by echocardiography and also by chest CTPA. Nuclear imaging is useful in discriminating CTEPH from APE. Better perspectives on diagnosis, risk stratification and decision making in PE can be provided by combining multimodality CV imaging. Here, the advantages or pitfalls of each imaging modality in diagnosis, risk stratification, or management of PE will be discussed.

Imaging of acute pulmonary embolism: an update

Imaging plays an important role in the evaluation and management of acute pulmonary embolism (PE). Computed tomography (CT) pulmonary angiography (CTPA) is the current standard of care and provides accurate diagnosis with rapid turnaround time. CT also provides information on other potential causes of acute chest pain. With dual-energy CT, lung perfusion abnormalities can also be detected and quantified. Chest radiograph has limited utility, occasionally showing findings of PE or infarction, but is useful in evaluating other potential causes of chest pain. Ventilation-perfusion (VQ) scan demonstrates ventilation-perfusion mismatches in these patients, with several classification schemes, typically ranging from normal to high. Magnetic resonance imaging (MRI) also provides accurate diagnosis, but is available in only specialized centers and requires higher levels of expertise. Catheter pulmonary angiography is no longer used for diagnosis and is used only for interventional management. Echocardiography is used for risk stratification of these patients. In this article, we review the role of imaging in the evaluation of acute PE.

Diagnostic Evaluation of Chronic Thromboembolic Pulmonary Hypertension

Pulmonary hypertension is defined by a mean pulmonary artery pressure greater than 25 mm Hg. Chronic thromboembolic pulmonary hypertension (CTEPH) is defined as pulmonary hypertension in the presence of an organized thrombus within the pulmonary vascular bed that persists at least 3 months after the onset of anticoagulant therapy. Because CTEPH is potentially curable by surgical endarterectomy, correct identification of patients with this form of pulmonary hypertension and an accurate assessment of surgical candidacy are essential to provide optimal care. Patients most commonly present with symptoms of exertional dyspnea and otherwise unexplained decline in exercise capacity. Atypical chest pain, a nonproductive cough, and episodic hemoptysis are observed less frequently. With more advanced disease, patients often develop symptoms suggestive of right ventricular compromise. Physical examination findings are minimal early in the course of this disease, but as pulmonary hypertension progresses, may include nonspecific finding of right ventricular failure, such as a tricuspid regurgitation murmur, pedal edema, and jugular venous distention. Chest radiographs may suggest pulmonary hypertension, but are neither sensitive nor specific for the diagnosis. Radioisotopic ventilation-perfusion scanning is sensitive for detecting CTEPH, making it a valuable screening study. Conventional catheter-based pulmonary angiography retains an important role in establishing the presence and extent of chronic thromboembolic disease. However, computed tomographic and magnetic resonance imaging are playing a growing diagnostic role. Innovative technologies such as dual-energy computed tomography, dynamic contrast-enhanced magnetic resonance imaging, and optical coherence tomography show promise for contributing diagnostic information and assisting in the preoperative characterization of patients with CTEPH.

Left Atrium Measurements via Computed Tomography Pulmonary Angiogram as a Predictor of Diastolic Dysfunction

PURPOSE

Left atrium (LA) enlargement on echocardiography may be an indicator of diastolic dysfunction (DD). It is not well known if computed tomography pulmonary angiography (CTPA) can detect DD.

METHODS

A total of 127 patients who underwent both CTPA and echo within 48 hours were analyzed retrospectively. Left atrium diameters from CTPA were correlated with echo and evaluated against degrees of DD. Computed tomography pulmonary angiography pulmonary artery (PA)/aorta ratio was analyzed as a tool to detect pulmonary hypertension.

RESULTS

There were 42% of patients who had DD. There was a strong correlation between LA size on CTPA and echo (r = 0.78). An LA greater than 4.0 cm gave a sensitivity of 68.1% and specificity of 73.9% for DD detection. A PA/aorta cutoff greater than 0.84 yielded a sensitivity of 84% and specificity of 33% for pulmonary hypertension.

CONCLUSIONS

Computed tomography pulmonary angiography measurements of LA and PA/aorta ratio correlate strongly with equivalent findings on echo. We suggest that LA and PA/aorta measurements be included on chest CTPA reports.

Contrast-enhanced CT- and MRI-based perfusion assessment for pulmonary diseases: basics and clinical applications

Assessment of regional pulmonary perfusion as well as nodule and tumor perfusions in various pulmonary diseases are currently performed by means of nuclear medicine studies requiring radioactive macroaggregates, dual-energy computed tomography (CT), and dynamic first-pass contrast-enhanced perfusion CT techniques and unenhanced and dynamic first-pass contrast enhanced perfusion magnetic resonance imaging (MRI), as well as time-resolved three-dimensional or four-dimensional contrast-enhanced magnetic resonance angiography (MRA). Perfusion scintigraphy, single-photon emission tomography (SPECT) and SPECT fused with CT have been established as clinically available scintigraphic methods; however, they are limited by perfusion information with poor spatial resolution and other shortcomings. Although positron emission tomography with 15O water can measure absolute pulmonary perfusion, it requires a cyclotron for generation of a tracer with an extremely short half-life (2 min), and can only be performed for academic purposes. Therefore, clinicians are concentrating their efforts on the application of CT-based and MRI-based quantitative and qualitative perfusion assessment to various pulmonary diseases. This review article covers 1) the basics of dual-energy CT and dynamic first-pass contrast-enhanced perfusion CT techniques, 2) the basics of time-resolved contrast-enhanced MRA and dynamic first-pass contrast-enhanced perfusion MRI, and 3) clinical applications of contrast-enhanced CT- and MRI-based perfusion assessment for patients with pulmonary nodule, lung cancer, and pulmonary vascular diseases. We believe that these new techniques can be useful in routine clinical practice for not only thoracic oncology patients, but also patients with different pulmonary vascular diseases.

Imaging of acute and chronic thromboembolic disease: state of the art

Acute pulmonary embolism (PE) is a life-threatening condition that requires prompt diagnosis and treatment. Recent advances in imaging allow acute and rapid recognition even by the non-specialist radiologist. Most acute emboli resolve on anticoagulation without sequelae; however, some emboli fail to fully resolve becoming endothelialised with the development of chronic thromboembolic disease (CTED). Increased pulmonary vascular resistance arising from CTED may lead to chronic thromboembolic pulmonary hypertension (CTEPH) a debilitating disease affecting up to 5% of survivors of acute PE. Diagnostic evaluation is more complex in CTEPH/CTED than acute PE with subtle imaging features often being overlooked or misinterpreted. Differentiation of acute from chronic PE and from other forms of pulmonary hypertension has profound therapeutic implications. Diverse imaging techniques are available to diagnose and monitor PEs both in the acute and chronic setting. Broadly they include techniques that provide data on lung parenchymal perfusion (ventilation-perfusion [VQ] scintigraphy), angiographic techniques (computed tomography [CT], magnetic resonance imaging [MRI], and invasive angiography) or a combination of both (MR angiography and time-resolved angiography or dual-energy CT angiography). This review aims to describe state of the art imaging highlighting the strength and weaknesses of individual techniques in the diagnosis of acute and chronic PE.

Pulmonary perfusion MRI using interleaved variable density sampling and HighlY constrained cartesian reconstruction (HYCR)

PURPOSE

To demonstrate the feasibility of performing single breathhold, noncardiac gated, ultrafast, high spatial-temporal resolution whole chest MR pulmonary perfusion imaging in humans.

MATERIALS AND METHODS

Eight subjects (five male, three female) were scanned with the proposed method on a 3 Tesla clinical scanner using a 32-channel phased-array coil. Seven (88%) were healthy volunteers, and one was a patient volunteer with sarcoidosis. The peak lung enhancement phase for each subject was scored for gravitational effect, peak parenchymal enhancement and severity of artifacts by three cardiothoracic radiologists independently.

RESULTS

All studies were successfully performed by MR technologists without any additional training. Mean parenchymal signal was very good, measuring 0.78 ± 0.13 (continuous scale, 0 = "none" → 1 = "excellent"). Mean level of motion artifacts was low, measuring 0.13 ± 0.08 (continuous scale, 0 = "none" → 1 = "severe").

CONCLUSION

It is feasible to perform single breathhold, noncardiac gated, ultrafast, high spatial-temporal resolution whole chest MR pulmonary perfusion imaging in humans.

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.

Comparison of the diagnostic utility of cardiac magnetic resonance imaging, computed tomography, and echocardiography in assessment of suspected pulmonary arterial hypertension in patients with connective tissue disease

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a life-threatening complication of connective tissue diseases (CTD). Our aim was to compare the diagnostic utility of noninvasive imaging modalities, i.e., magnetic resonance imaging (MRI), computed tomography (CT), and echocardiography, in evaluation of these patients.

METHODS

In total, 81 consecutive patients with CTD and suspected PH underwent cardiac MRI, CT, and right heart catheterization (RHC) within 48 hours. Functional cardiac MRI variables [ventricle areas and ratios, delayed myocardial enhancement, position of the interventricular septum, right ventricular mass, ventricular mass index (VMI), and pulmonary artery distensibility] were all evaluated. The pulmonary artery size, pulmonary artery/aortic ratio (PA/Ao), left and right ventricular (RV) diameter ratio, RV wall thickness, and grade of tricuspid regurgitation were measured on CT. Tricuspid gradient (TG) and size of the RV were assessed using echocardiography.

RESULTS

In our study of 81 patients with CTD, 55 had PAH, 22 had no PH, and 4 had PH owing to left heart disease. There was good correlation between mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) measured by RHC and VMI derived from MRI (mPAP, r = 0.69, p < 0.001; PVR, r = 0.78, p < 0.001) and systolic area ratio (mPAP, r = 0.69, p < 0.001; PVR, r = 0.68, p < 0.001) and TG derived from echocardiography (mPAP, r = 0.84, p < 0.001; PVR, r = 0.76, p < 0.001). In contrast, CT measures showed only moderate correlation. MRI and echocardiography each performed better as a diagnostic test for PAH than CT-derived measures: VMI ≥ 0.45 had a sensitivity of 85% and specificity 82%; and TG ≥ 40 mm Hg had a sensitivity of 86% and specificity 82%. Univariate Cox regression analysis showed the MRI measurements were better at predicting mortality. Patients with RV end diastolic volume < 135 ml had a better prognosis than those with a value > 135 ml, with a 1-year survival of 95% versus 66%, respectively.

CONCLUSION

In patients with CTD and suspected PAH, cardiac MRI and echocardiography have greater diagnostic utility than CT in the assessment of patients with suspected PAH, and MRI has prognostic value.

Contrast-enhanced multidetector-row computed tomography vs. Time-resolved magnetic resonance angiography vs. contrast-enhanced perfusion MRI: assessment of treatment response by patients with inoperable chronic thromboembolic pulmonary hypertension

PURPOSE

To compare therapeutic effect assessment capability of multidetector-row computed tomography (MDCT), magnetic resonance angiography (MRA), and dynamic perfusion MRI for chronic thromboembolic pulmonary hypertension (CTEPH) patients.

MATERIALS AND METHODS

Twenty-four consecutive CTEPH patients treated with conventional therapy underwent pre- and posttherapeutic MDCT, MRA, dynamic perfusion MRI, 6-minute walk distance (6-MWD), cardiac ultrasound (US), and right heart catheterization. According to therapeutic results, all patients were divided into response (n = 13) and nonresponse (n = 11) groups. CTEPH indexes for MDCT (CTEPH(CT) ) and MRA (CTEPH(MRA) ) were calculated on the basis of embolic burden. Pulmonary perfusion parameter maps were generated from all perfusion MR data, followed by determination of improvements in mean perfusion parameter at regions of interest (ROIs) for each patient. Receiver operating characteristic (ROC)-based positive tests were performed to determine the feasible threshold values for distinguishing two groups. Finally, diagnostic capabilities were compared by means of McNemar's test.

RESULTS

When feasible threshold values adapted, specificity (90.9 〈10/11〉%, P < 0.05) and accuracy (95.8 〈23/24〉%, P < 0.05) for improvement in pulmonary blood flow were significantly higher than those for CTEPH(CTA) (specificity: 36.4 〈4/11〉%, accuracy: 70.8 〈17/24〉%).

CONCLUSION

Dynamic perfusion MRI has better capability for assessment of therapeutic effect on CTEPH patients than does MDCT.

Pulmonary hypertension: chapters of innovation and tribulation

As can be seen by the mounting literature, there has been immense progress in the field of pulmonary hypertension (PH) over the last three decades, illustrated by several important milestones including improved understanding of disease pathogenesis, new classifications of disease, advances in screening and diagnostic techniques, and new rules for staging and follow-up, which have subsequently led to improvements in patient outcomes. The objectives of this manuscript are to not only highlight these very recent advances but also point out areas of deficiencies or gaps in our knowledge that may serve a focal point for future discussion and investigation.

Diagnostic accuracy of contrast-enhanced MR angiography and unenhanced proton MR imaging compared with CT pulmonary angiography in chronic thromboembolic pulmonary hypertension

OBJECTIVE

To evaluate the diagnostic accuracy of contrast-enhanced MR angiography (CE-MRA) and the added benefit of unenhanced proton MR angiography compared with CT pulmonary angiography (CTPA) in patients with chronic thromboembolic disease (CTE).

METHODS

A 2 year retrospective study of 53 patients with chronic thromboembolic pulmonary hypertension who underwent CTPA and MRI for suspected pulmonary hypertension and a control group of 36 patients with no CT evidence of pulmonary embolism. The MRI was evaluated for CTE and the combined diagnostic accuracy of ce-MRA and unenhanced proton MRA was determined. CE-MRA generated lung perfusion maps were also assessed.

RESULTS

The overall sensitivity and specificity of CE-MRA in diagnosing proximal and distal CTE were 98% and 94%, respectively. The sensitivity improved from 50% to 88% for central vessel disease when CE-MRA images were analysed with unenhanced proton MRA. The CE-MRA identified more stenoses (29/18), post-stenosis dilatation (23/7) and occlusions (37/29) compared with CTPA. The CE-MRA perfusion images showed a sensitivity of 92% for diagnosing CTE.

CONCLUSION

CE-MRA has high sensitivity and specificity for diagnosing CTE. The sensitivity of CE-MRA for visualisation of adherent central and lobar thrombus significantly improves with the addition of unenhanced proton MRA which delineates the vessel wall.