Materials and Methods
Literature review:
A literature review using PUBMED ('aortic dissection' infiltration of the lung parenchyma ',' interstitial pulmonary hemorrhage ') has led to the identification of seven reported cases,
illustrated by computed tomography (1,
2,
5,
6,
7,
8,
and 9).
Our radiological cases:
Case series of twelve aortic dissections with hemorrhagic infiltration of the aortopulmonary sheath,
from five academic centers was reported from 2008 to 2010.
The medical records were reviewed.
Computed tomography (MDCT) was performed for each patient.
Our pathological cases:
A search of autopsy reports from 2006 to 2012,
at the Montreal General Hospital was performed.
Two reports describing acute aortic dissection with infiltration of the aortopulmonary sheath were identified.
They also contain photographs of this disease.
MDCT technique:
Images from the MDCT were performed with computed tomography (CT) 16-MDCT (LightSpeed 16,
GE Healthcare),
64-MDCT (LightSpeed VCT,
GE Healthcare),
or 256-MDCT (iCT,
Philips Healthcare).
The study initial CT acquisition is usually obtained from a non-contrast CT,
followed by a study with IV injection of iodinated contrast.
The nonionic contrast medium (100 mL iopamidol 370,
Isovue 370,
Bracco,
or 100 mL iodinanol 320 Visipaque 320,
GE Healthcare) is injected intravenously at a rate of 5 mL/s in the right antecubital vein through a 18-gauge needle,
followed by a bolus of saline (bolus-tracking method).
Radiological Findings
Our case series includes a total of twelve patients (5 M,
7 F) (see Table 1),
with an average age of 71.1 years (range 49-90 years).
Six patients presented with chest pain,
and seven had a history of poorly controlled hypertension.
In one patient,
the aortic dissection was likely secondary to an iatrogenic dissection of the right coronary artery,
which occurred during conventional coronary angiography (aortocoronary dissection).
MDCT without contrast findings:
When available,
the MDCT without contrast showed hyperdense foci at the periphery of the proximal pulmonary arteries (Fig.
2,
images on the left).
In the interstitium,
hemorrhagic extravasations along the subsegmental pulmonary arteries would be seen on MDCT as ground glass opacities.
In the particular case of the patient with iatrogenic aortocoronary dissection (Patient 5),
MDCT without contrast (performed immediately after coronary angiography) showed very hyperdense areas at the periphery of the ascending aorta and proximal pulmonary arteries.
This hyperdensity is caused by remaining contrast agent from the recent angiography (Fig.
3).
MDCT findings using iodized contrast:
The opacification of the pulmonary arteries' lumen shows the infiltrated appearance surrounding the periphery of these arteries in continuity with the infiltrated appearance of the circumference of the ascending aorta. That is to say,
the presumed site of the common aortopulmonary sheath.
We may also note the compression,
to varying degrees,
of the pulmonary trunk and of the right and left main pulmonary arteries,
which in one case,
to a near-total luminal obstruction (Fig.
4).
This peri-vascular infiltration involves right and left main pulmonary arteries in 6 cases,
the right main pulmonary artery in 2 cases (Fig.
5),
and left alone in one case. In 2 cases,
the infiltration is limited only to the pulmonary trunk without reaching the bifurcation.
In 4 cases,
the presence of ground-glass opacities is displayed at the periphery of the pulmonary arteries (Fig.
6).
One hypothesis explaining this finding is that these opacities are the result of localized alveolar hemorrhage secondary to ischemia.
This would nevertheless have to be confirmed pathologically.
It is important to note that the presence of ground-glass opacity is mainly observed in cases where the compression of the pulmonary trunk is greater than or equal to 40%.
Pathology findings
The first of two autopsy cases,
with the most extensive disease,
is the one of a 90 year-old woman,
who died suddenly in an emergency,
following a presentation of severe chest pain.
The autopsy showed an aneurysm of the ascending thoracic aorta measuring 7cm in diameter,
with a transverse parietal fissure of 9 cm in length (Fig.
7a).
This fissure transected the intima,
media and adventitia to reach the sheath located between the aorta and the pulmonary trunk. The hemorrhage infiltrated along the sheath and entered the lung parenchyma through the hilum (Fig.
7b),
spreading around the bronchi,
arteries,
and pulmonary veins (Fig.
7c).
The second case is a 45 year-old woman who presented with severe epigastric pain. She died suddenly of cardiac arrest soon after her arrival in the emergency department. The autopsy showed an aneurysm of the ascending aorta measuring 4.1 cm in diameter with a transparietal fissure of 1cm in length,
located in the left lateral wall of the ascending aorta,
likely due to a rupture with dissection. Extensive hemorrhagic infiltration was noted reaching the right hilum and infiltrating the circumference of the right main bronchus and pulmonary arteries of middle lobe (Fig.
8).