Paucity of angiographic findings despite extensive organized thrombus in chronic thromboembolic pulmonary hypertension

Suspected pulmonary embolism: enhancement of pulmonary arteries at deep-inspiration CT angiography--influence of patent foramen ovale and atrial-septal defect

PURPOSE

To investigate if abnormal early contrast enhancement of the aorta and decreased attenuation of pulmonary arteries at deep-inspiration spiral computed tomographic (CT) angiography might be caused by a patent foramen ovale (PFO).

MATERIALS AND METHODS

Two hundred forty-four spiral CT angiographic images of the pulmonary arteries obtained during deep inspiration in patients suspected of having pulmonary embolism (PE) were reviewed for evidence of abnormal early enhancement of the aorta. In 45 patients, enhancement of the ascending aorta was equal to or more than that of the pulmonary arteries. Nonenhanced or contrast material-enhanced echocardiography was performed in 39 of these cases. All CT images with abnormal enhancement patterns were graded for contrast quality with respect to sufficient enhancement of pulmonary arteries (four grades) at three anatomic levels: right and left main and lobar and segmental branches. In addition, all spiral CT angiographic images were evaluated concerning the diagnosis of PE and the grouping of central (main pulmonary artery to proximal lobar arteries) and peripheral (beyond proximal lobar branches) locations of emboli. Mean attenuation values of ascending aortas and main pulmonary arteries in group 1 (n = 244) were compared with those in groups 2 and 3 (n = 45) by means of the two-tailed Student t test for unpaired data (P <.05).

RESULTS

Attenuation values for ascending aortas in group 1 were significantly lower than those in groups 2 and 3 (P <.001). Attenuation values in main pulmonary arteries were significantly higher in group 1 than in groups 2 and 3 (P <.001). Echocardiographic images showed an intracardiac right-to-left shunt in all 39 cases with abnormal contrast dynamics in the CT study (16% of the whole study population). Three patients had an atrial-septal defect, and 36 had a PFO. Images with a shunt had good (9%), intermediate (37%), fair (33%), and poor (23%) contrast of the pulmonary arteries. Sufficient vessel contrast for the diagnosis of PE could not be achieved in 27 of 45 patients with a shunt, but severe central PE could be ruled out. PE could be diagnosed in 31% of the 244 images, 58% were negative, and 11% were indeterminate.

CONCLUSION

A PFO may frequently lead to insufficient attenuation of the pulmonary arteries, which potentially limits the diagnosis of PE if the examination is performed during deep inspiration.

Diagnostic value of transoesophageal echocardiography in suspected haemodynamically significant pulmonary embolism

OBJECTIVE

To assess the value of transoesophageal echocardiography (TOE) for diagnosing suspected haemodynamically significant pulmonary embolism and signs of right ventricular overload at standard echocardiography.

METHODS

113 consecutive patients (58 male; 55 female), mean (SD) age 53.6 (13.3) years, in whom there was clinical suspicion of pulmonary embolism and right ventricular overload on transthoracic echocardiography, underwent TOE in addition to routine diagnostic procedures to identify pulmonary artery thrombi.

RESULTS

TOE revealed thrombi in 32 of 51 patients who had suspected acute pulmonary embolism and in 31 of 62 with suspected chronic pulmonary embolism. In one patient a pulmonary angiosarcoma rather than chronic pulmonary embolism was found at surgery. The diagnosis of pulmonary embolism was confirmed in 77 patients by scintigraphy, spiral computed tomography, angiography, or necropsy (reference methods). While TOE failed to provide a diagnosis of pulmonary embolism in 15 of these 77 patients, no false positive findings were reported (sensitivity 80.5%, specificity 97.2%). In 11 and 26 cases, respectively, the thrombi were confined to the left or right pulmonary artery. Bilateral thrombi were found in 25 patients. Mobile thrombi were observed only in acute pulmonary embolism (in 19 of 32 patients). No complications of TOE were noted.

CONCLUSIONS

TOE permits visualisation of pulmonary arterial thrombi, confirming the diagnosis in the majority of patients with pulmonary embolism and right ventricular overload. This may be useful for prompt decision making in patients with haemodynamic compromise considered for thrombolysis or embolectomy.

From the archives of the AFIP: pulmonary vasculature: hypertension and infarction

Pulmonary hypertension is the hemodynamic consequence of vascular changes within the precapillary (arterial) or postcapillary (venous) pulmonary circulation. These changes may be idiopathic, as in primary pulmonary hypertension or pulmonary veno-occlusive disease, but more commonly they represent a secondary response to alterations in pulmonary blood flow. The pulmonary and systemic bronchial circulations form broad anastomoses that largely prevent infarction except in settings of markedly elevated pulmonary venous pressure, underlying malignancy, or excessive embolic burden. Causes of precapillary pulmonary hypertension include long-standing cardiac left-to-right shunt, chronic thromboembolic disease, and widespread pulmonary embolism arising from intravascular malignant cells, parasites, or foreign materials. The classic radiologic features of precapillary pulmonary hypertension are central arterial enlargement, sharply pruned peripheral vascularity, and right-sided heart hypertrophy and chamber dilatation. Postcapillary pulmonary hypertension may develop secondary to focal venous constriction or to compromised pulmonary venous drainage due to left atrial neoplasia, mitral stenosis, or left ventricular failure. Radiologic manifestations of postcapillary pulmonary hypertension include prominent septal lines, small pleural effusions, and occasionally air-space opacities. In addition, radiologic evaluation of postcapillary pulmonary hypertension may demonstrate evidence of pulmonary arterial hypertension, secondary to the retrograde transmission of elevated pulmonary venous pressure across the capillary bed.

Three-dimensional CT angiography of the thorax: clinical applications

Spiral CT with three-dimensional (3D) display can provide a rapid noninvasive examination of the vascular system and has been shown to have a wide range of clinical applications in the thorax, including imaging of the aorta, pulmonary vasculature, and venous abnormalities. Three-dimensional images can provide views of the imaging volume from innumerable viewing angles for both the radiologist and referring clinician, and potentially obviate invasive procedures such as angiography. In this article, we will review many of these applications of spiral CT angiography with 3D displays. Emphasis is placed on study design, protocol selection, and display of pathology.

Noninvasive diagnosis of suspected severe pulmonary embolism: transesophageal echocardiography vs spiral CT

OBJECTIVE

Patients with pulmonary embolism (PE) and echocardiographic signs of right ventricular overload have worse prognosis and may require aggressive therapy. Unequivocal confirmation of PE is required before thrombolysis or embolectomy. This study compares the value of transesophageal echocardiography (TEE) and spiral CT (sCT) in direct visualization of pulmonary artery thromboemboli in patients with suspected PE and echocardiographic signs of right ventricular overload.

MATERIAL AND METHODS

Forty-nine consecutive patients (29 men and 20 women), aged 52.2+/-18.3 years, with clinical suspicion of acute (23) or chronic (26) PE and otherwise unexplained right ventricular overload at transthoracic echocardiography underwent TEE and sCT. Main and lobar (central) pulmonary arteries were searched for emboli with both TEE and sCT, while segmental and subsegmental (distal) pulmonary arteries were searched only with sCT.

RESULTS

Of 40 patients with PE confirmed by high-probability lung scan (27) or angiography (13), central pulmonary arterial emboli were found at TEE and sCT in 32 (80%) and 36 (90%) patients, respectively. Neither method reported false central PE (specificity, 100%). When distal pulmonary arteries were analyzed, sensitivity of sCT increased to 97.5%, but three patients with primary pulmonary hypertension according to standard tests were misclassified as having distal PE (specificity, 90.1%). Most patients had bilateral PE according to sCT (34/36) and standard tests (40/40) but not TEE (15/32), probably due to its topographic limitations.

CONCLUSIONS

Because of high prevalence of bilateral central pulmonary thromboemboli in patients with hemodynamically significant PE, both sCT and TEE allow its definitive confirmation in most cases. Thrombi reported by sCT distally to lobar arteries should be interpreted with caution.