DOI:10.2214/AJR.06.0569
AJR 2007; 189:S26-S28
© American Roentgen Ray Society
AJR Teaching File: Dyspnea Following Surgical Repair of Partial Anomalous Venous Return
Ba D. Nguyen1
1 Department of Radiology, Mayo Clinic Scottsdale, 13400 E Shea Blvd.,
Scottsdale, AZ 85259.
Received April 26, 2006;
accepted after revision October 4, 2006.
Address correspondence to B. D. Nguyen
(nguyen.ba{at}mayo.edu).
Keywords: cardiopulmonary imaging • cardiovascular imaging • nuclear medicine
Case History
A 32-year-old woman had a history of bilateral partial anomalous pulmonary
venous return. The left upper pulmonary vein drained into the left
brachiocephalic vein and the pulmonary vein of the right upper lobe (RUL) and
right middle lobe (RML) communicated with the superior vena cava. She had
corrective surgery with the left pulmonary vein implanted to the left atrial
appendage and the RUL/RML pulmonary vein channeled to a conduit baffled
through the upper aspect of the atrial septum to the left atrium. Five months
after surgery, the patient started to complain of shortness of breath and
imaging showed fleeting right lung infiltrates. There was no definite
infectious cause from extensive clinical and laboratory workup.
Radiologic Description
Postoperative serial chest radiographs show ill-defined waxing and waning
right lung infiltrates (Fig.
1A). Lung ventilation/perfusion (V/Q) scintigraphy shows diffusely
decreased ventilatory tracer distribution in the RUL and RML
(Fig. 1B). There was complete
absence of radiotracer perfusion of these two right pulmonary lobes
(Fig, 1C). A coronal MR
angiographic maximum-intensity-projection (MIP) image of chest shows a
high-grade obstruction of the graft connecting the RUL and RML pulmonary veins
to the left atrium (Fig. 1D). A
sagittal CT reconstruction image of the right lung also shows confluent
opacities diffusely within the RUL and RML from congestion
(Fig. 1E).
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Fig. 1A —32-year-old woman with major cardiovascular surgery and onset
of dyspnea. Posteroanterior chest radiograph shows ill-defined right upper
lobe (RUL) and right middle lobe (RML) infiltrates (arrowheads).
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Fig. 1D —32-year-old woman with major cardiovascular surgery and onset
of dyspnea. Coronal maximum-intensity-projection MR angiographic image shows
entire course of RUL–RML pulmonary vein graft (long arrows)
joining left atrium (LA). There is segmental stenosis the venous graft
(short arrows) proximal to its connection with left atrium (LA).
Anatomic landmarks: AA: aortic arch; SVC: superior vena cava; IVC: inferior
vena cava; RPA: right pulmonary artery; LPV: left pulmonary vein.
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Fig. 1E —32-year-old woman with major cardiovascular surgery and onset
of dyspnea. Sagittal CT reconstruction image of right lung shows congestion of
RUL and RML from postcapillary obstruction (arrows).
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Differential Diagnosis
The differential diagnosis of pulmonary venous stenosis (PVS) includes
mucus plug, tumor compression or invasion of the pulmonary vessels, and
pulmonary embolism (PE).
Diagnosis
Based on the radiographic and scintigraphic findings, pulmonary vein graft
stenosis is the best diagnosis.
Commentary
Lung ventilation and perfusion scintigraphy are primarily used to evaluate
PE. The diagnosis is based on mismatched lung perfusion defects, which could,
however, be seen with other nonembolic causes. This article presents a case of
pulmonary vein graft stenosis with scintigraphic findings that could mislead
to the diagnosis of PE. This presentation also addresses another iatrogenic
cause of PVS related to radiofrequency ablation treatment of atrial
fibrillation.
PVS has been reported with abnormal lung V/Q scans simulating the diagnosis
of PE. Pathologic processes causing PVS may be congenital, thromboembolic,
neoplastic, or postsurgical [1,
2]. The recently expanding
practice of atrial fibrillation therapy with radiofrequency catheter ablation
at the pulmonary vein ostium may also induce PVS
[3,
4]. The occurrence rate of PVS
is not known but is expected to be on the rise due to the popularity of this
interventional procedure offering a success rate of 80–95% in curing
atrial fibrillation [5]. This
iatrogenic complication is multifactorial, related to the initial size of the
targeted pulmonary vein, ablation energy and technique, and experience of the
operator. PVS is from induced fibrosis and scar contraction of the involved
pulmonary vein ostium. Functional evaluation with lung V/Q scintigraphy shows
mismatched perfusion defects in instances of greater than 80% luminal PVS or
resting pulmonary vein–left atrium pressure gradient above 5 mm Hg
[4]. PVS may be detected when
perfusion MRI shows a venous diameter reduced to less than 6 mm
[6].
Independently of its different causative mechanisms, PVS triggers pulmonary
congestion, increases the capillary wedge pressure, and counterbalances the
pulmonary arterial flow. The postcapillary obstruction raises the
physiologically low impedance of the pulmonary circulation of involved lung
and induces preferential flow distribution to regions with less resistance
[4]. PVS thus decreases or
prevents the circulation of radiolabeled methoxyacetic acid particles to the
capillary level of the concerned lung, producing mismatched perfusion defects
on lung V/Q scan. PVS symptomatology is nonspecific, ranging from absence of
clinical manifestation to a myriad of clinical findings of chest discomfort,
shortness of breath, cough, pleuritic chest pain, and hemoptysis. PVS may
present with chest radiographic findings of infiltrates, consolidation, and
pleural effusion
[1–3].
Without prior knowledge of cardiovascular surgery or ablative therapy for
atrial fibrillation, the clinical and radiographic features of PVS may mislead
clinicians and imagers toward the diagnosis of pneumonia radiographically or
PE scintigraphically.
Mucus plug, with predominant impact on airways, may cause matched or
reversed mismatched V/Q defects
[7,
8]. Neoplastic extrinsic and
intrinsic compromise of the pulmonary vasculature with variable patterns of
perfusion defect may be difficult to differentiate PE from PVS based solely on
scintigraphy and should be further assessed with CT
[9]. In this case presentation,
CT and MR angiography exclude mucus plug, PE, and tumor compressing pulmonary
vasculature and airways. CT shows congestion of the RUL and RML as a result of
postcapillary obstruction with decreased radiotracer distribution on
ventilation scintigraphy. MR angiography shows the high-grade stenosis of the
surgically corrected right lobar anomalous pulmonary venous return as the
cause of abnormal lung V/Q scintigraphic findings.
Objective
This article presents different causes of PVS, explains its pathophysiology
resulting in lung scintigraphic perfusion abnormalities, and discusses its
differential diagnosis.
Conclusion
PVS with postcapillary obstructive physiopathology should be included in
the differential diagnosis of pulmonary perfusion deficits on lung
scintigraphy, especially in the clinical context of prior cardiovascular
surgery and the expanding practice of radiofrequency ablation therapy for
atrial fibrillation.
References
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- Bray ST, Johnstone WH, Dee PM, Pope TL Jr, Teates CD, Tegtmeyer CJ.
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Case History
Radiologic Description
