3 DISCUSSION
At present, it is believed that the risk factors for cerebral ischemic
stroke in patients with PAVF are: (1) feeding artery diameter
> 3 mm; (2) existence of multiple PAVFs.7 Whether patients with PAVF present with clinical
manifestations depends on the right-to-left shunt quantity. There are
intrapulmonary and extrapulmonary manifestations in patients with
pulmonary arteriovenous fistula. The intrapulmonary manifestations are
as follows: dyspnea after the activity, dizziness, easy to fatigue, etc.8-10 Physical examination may reveal cyanosis,
clubbing fingers(toes), and chest continous murmur, etc. Some patients
may only present with abnormal arterial blood gas analysis.The
extrapulmonary manifestations are as follows: migraine, TIA, ischemic
stroke, brain abscess, epilepsy, etc. 8-10
Espejo-Herrero et al 1 reported a patient with TIA
presenting with a short-term (30 min) right limb paralysis, and
subsequent pulmonary arteriography showing a PAVF. Pulmonary DSA is the
gold standard for the diagnosis of PAVF, which can observe the fistula
size, feeding artery, draining vein and other conditions.8 However, DSA is an invasive examination. As a
non-invasive examination, CTA can not only show the lesions (even the
mild lesions) and the responsible blood vessels of PVAFs, but also
accurately judge the peripheral and complex PVAFs, which is more
suitable for the diagnosis of PAVF. 8 At present,
c-TCD has been widely used for right-to-left shunt screening, which can
dynamically observe the emboli entering into the intracranial arteries
and the changes of cerebral blood flow in real time.11,12 In our report of this case, c-TCD revealed a
positive result with a big right-to-left shunt, which was in line with
the diagnosis of PAVF.
Most of the PAVFs will gradually enlarge and rarely atrophy
spontaneously, which may cause serious complications. The mortality rate
of untreated patients with PAVF was as high as 50%, which can be
reduced to 3% after treatment. At present, it is advocated that active
treatments should be adopted for patients with symptomatic or
asymptomatic PAVFs, if their lesions diameter exceed 3mm. The PAVF
treatments mainly include surgery and interventional embolization, which
can improve the symptoms of hypoxia and prevent the occurrence of
central nervous system complications. 8,9 Todo et al13 reported a patient with recurrent ischemic stroke
induced by PAVF with a feeding artery diameter of 1.80 mm, who was
successfully prevented from the recurrence of embolic events after
embolic treatment. In our report, this case was treated with
interventional embolization of PAVF in our hospital, and there was no
recurrent seizure of TIA symptoms for 2 years, which further confirmed
that the recurrent TIA symptoms were associated with PAVF.
In conclusion, although pulmonary arteriovenous fistula is a rare cause
of abnormal embolism, it can not be ignored as the main extracardiac
shunt pathway. Most patients with PAVF have atypical clinical
presentations, and even present with cerebral ischemic stroke or TIA as
the only clinical symptom. Therefore, for the patients with cryptogenic
stroke , especially for the children with cryptogenic stroke, the
corresponding examinations should be conducted to judge whether they may
suffer from PAVF, then active treatments and follow-up should be
offered.