A Clinical Approach to Multimodality Imaging in Pulmonary Hypertension

Abstract

Pulmonary hypertension (PH) is a clinical condition characterized by progressive elevations in mean pulmonary artery pressures and right ventricular dysfunction, associated with significant morbidity and mortality. For resting PH to develop, ~50-70% of the pulmonary vasculature must be affected, suggesting that even mild hemodynamic abnormalities are representative of advanced pulmonary vascular disease. The definitive diagnosis of PH is based upon hemodynamics measured by right heart catheterization; however this is an invasive and resource intense study. Early identification of pulmonary vascular disease offers the opportunity to improve outcomes by instituting therapies that slow, reverse, or potentially prevent this devastating disease. Multimodality imaging, including non-invasive modalities such as echocardiography, computed tomography, ventilation perfusion scans, and cardiac magnetic resonance imaging, has emerged as an integral tool for screening, classifying, prognosticating, and monitoring response to therapy in PH. Additionally, novel imaging modalities such as echocardiographic strain imaging, 3D echocardiography, dual energy CT, FDG-PET, and 4D flow MRI are actively being investigated to assess the severity of right ventricular dysfunction in PH. In this review, we will describe the utility and clinical application of multimodality imaging techniques across PH subtypes as it pertains to screening and monitoring of PH.

Keywords: computed tomography; echocardiography; magnetic resonance imaging; pulmonary hypertension; scintigraphy.

Figure 1

Echocardiographic images are shown in a scleroderma patient with severe pulmonary hypertension on stable therapies. (A) Apical 4 chamber view demonstrates severe right atrial enlargement with bowing of the interatrial septum from right to left suggestive of elevated right atrial pressures. The right ventricle is severely dilated and hypertrophied with a prominent moderator band. The left ventricle is hypertrophied and small. (B) Parasternal short-axis is shown in the same patient with marked RV enlargement and evidence of RV pressure overload distorting the normal circular short-axis geometry of the LV. There is a small posterior pericardial effusion present. (C) Tricuspid annular plane systolic excursion (TAPSE) utilizes M-mode techniques to measure the longitudinal motion of the basal right ventricular wall segment during systole as an estimate of right ventricular systolic function. TAPSE is mildly reduced at 1.5 cm (normal >1.6 cm) however fractional area change was 24% (moderate-severely reduced). (D) Right Ventricular Longitudinal Systolic Strain (RVLSS) is a recent echocardiographic advancement based on ultrasound-myocardial tissue interactions. Each segment of the RV in this example corresponds with a strain curve with the white dotted line representing an average of the segmental strain for the regional curves in this view. Regional RV free wall strain is reduced in the basal and midventricular wall segments with less reduction in the apical segment. Global strain is an average of the three RV free wall segments and is −14.3%. (E) Right Ventricular Systolic Pressure utilizes the peak tricuspid velocity to calculate the peak right ventricular systolic pressure using the modified Bernoulli equation. RVSP= [peak gradient (mmHg) = right atrial pressure + (4 × Peak velocity 2)]. In this example, RVSP = 57 mmHg + 15 mmHg = 72 mmHg. (F) Right atrial pressures are estimated from the IVC diameter made in subcostal view at end-expiration. In this example, the IVC is severely dilated at 3.2 cm with minimal respiratory variation suggestive of markedly elevated right atrial pressure of 15 mmHg.

Figure 2

Computed tomography (CT) images of the chest with and without contrast are shown from a 64-year-old female with connective tissue disease, severe interstitial lung disease, and mixed severe pulmonary hypertension are shown. (A) Transaxial images are shown demonstrating an enlarged main pulmonary arterial size at 3.2 cm when compared to ascending aorta size of 2.9 cm at the same level suggestive of pulmonary hypertension. There is no evidence of pulmonary embolism with optimal contrast opacification. (B) Transaxial images in the lung window demonstrate extensive bilateral diffuse groundglass opacities and honeycombing. There is associated intralobular and interstitial thickening and bronchiectasis consistent with patient's known history of connective tissue disease associated non-specific interstitial pneumonitis.

Figure 3

Positron emission tomography (PET) images are shown from a 52-year-old woman with emphysema and associated Group 3 pulmonary hypertension presenting with acute exacerbation. 9.78 mCi ¹⁸F-FDG injected at 119 mg/dl blood glucose level. Image acquisition 57 mins post injection. (A) Maximum intensity projection image demonstrates FDG uptake in the diaphragm, infrahyoid muscles, and intercostal muscles consistent with increased work of breathing noted during examination. There is also diffuse subcutaneous uptake, reflecting treatment with corticosteroids during the exacerbation. (B) Transaxial images at the midventricular level demonstrate abnormal uptake in the right ventricle. (C) Transaxial images at the level of the main pulmonary artery (mPA) demonstrate enlarged mPA and abnormal FDG uptake in the right ventricular outflow track.

Figure 4

Computed tomography (CT) and ^99mTc-sestamibi single-photon emission computed tomography (SPECT) images from a 23-year-old woman with history of D-transposition of the great arteries (D-TGA) status-post repair. (A) Transaxial CT angiogram image demonstrating the characteristic appearance of the pulmonary artery and aorta after repair of D-TGA. (B) Non-contrast CT acquired at time of SPECT shows a stent in the pulmonary artery that was placed after the patient developed severe pulmonary artery stenosis. (C) Short axis SPECT image shows normal radiotracer distribution in the left ventricle with extension of uptake into the visualized portion of the right ventricle, consistent with pulmonary hypertension.

Figure 5

Cardiac Magnetic Resonance (CMR) images are shown from a 38-year-old female with idiopathic pulmonary arterial hypertension. (A) Four-chamber bright blood CMR image from end diastole shows a dilated and hypertrophied right ventricle at a mean pulmonary pressure of 47 mmHg. End systolic images show leftward bowing of the interventricular septum from elevated right ventricular pressure. (B) Late systolic images show leftward bowing of the interventricular septum from elevated RV pressure. (C) Short axis CMR image shows marked hypertrophy of the right ventricular free wall and septal bowing. (D) Short axis LGE image shows prominent enhancement at the anterior and inferior RV insertion points (asterisks).