Pulmonary arteriovenous malformation as a cause of ischaemic stroke in the elderly

Abstract

Pulmonary arteriovenous malformation (PAVM) is well recognised as a cause of paradoxical brain embolism. The authors report the case of an older woman with a medical history of arterial hypertension who was found unconscious and was discovered to have pulmonary thromboembolism and ischaemic stroke related to a PAVM.

Background

A pulmonary arteriovenous malformation (PAVM), also called pulmonary arteriovenous fistulae, arteriovenous aneurysm, cavernous angioma of the lung and pulmonary telangiectasis,¹ represents an abnormal communication between a pulmonary artery and vein in the absence of a capillary communication.²

Right-to-left shunt formed by PAVM can result in cyanosis, haemorrhage and significant paradoxical embolic phenomena,³ representing an uncommon but important cause of ischaemic stroke. Most ischaemic strokes occur in patients who have not yet been diagnosed with their arteriovenous malformation.⁴

Catheter embolisation and surgical resection are the methods of choice for the treatment of PAMV, and of these, catheter embolisation is the standard of care due to its low incidence of complications and because it is less invasive than surgical resection.⁵

Case presentation

An 86-year-old female patient, Caucasian, with a medical history of arterial hypertension, was found unconscious in her house by a relative. After regaining consciousness, the relative noticed dysarthria and deviation of the labial commissure to the left, so she referred the patient to the emergency department. On observation, she followed simple orders and presented psychomotor agitation. The physical examination was also remarkable for labial cyanosis and discreet digital clubbing. Blood pressure was high (188/123 mm Hg) with a normal heartbeat (92 bpm). Cardiac and pulmonary auscultation did not reveal changes. On summary neurological examination, the patient had dysarthria and deviation of the labial commissure to the left. There were no motor deficits despite poor collaboration.

Investigations

Arterial blood gas analysis revealed pH 7.45, pCO2 (partial pressure of carbon dioxide) 33.5 mm Hg, pO2 (partial pressure of oxygen) 59.9 mm Hg, oxygen saturation 91.4%, HCO3 (bicarbonate) 24.2 mEq/L and lactates 0,9 mg/dL. Performed blood count, coagulation study (d-dimers 2238 ng/mL; normal range <255 ng/mL), biochemistry (C reactive protein 7.21 mg/L; normal range <6.20 mg/dL) and troponin test (0081 ng/mL, high risk). Electrocardiogram showed sinus rhythm, without any alterations. Considering the hypocapnia and the high values of d-dimers, we considered the hypothesis of pulmonary thromboembolism and CT angiography of the chest was requested. This examination showed a complex arteriovenous malformation, irrigated by two arteries, in the right upper lobe, with a thrombus in the anterior afferent artery (figures 1 and 2). Considering the existing of a right-left shunt which can lead to paradoxical embolic phenomena, we requested a cranial brain CT which did not revealed acute lesions, although previously, it showed small bilateral and right thalamic nucleocapsular hypodensities, and sequelae of ischaemic vascular lesions with left paramedian infarction in the pons and bilateral cerebellar infarcts. The patient was not suitable for thrombolysis due to uncertain onset time. She was admitted to the internal medicine department with a pulmonary thromboembolism diagnosed and a suspicion of ischaemic stroke without imaging translation, caused by a PAVM.

Figure 1.

Chest CT angiography showing an arteriovenous malformation in the right upper lobe.

Figure 2.

Chest CT angiography showing an arteriovenous malformation with a thrombus in the anterior afferent artery.

During the hospitalisation, the patient was monitored by continuous ECG and for vital parameters without any abnormalities. In addition, thrombophilia screen for hereditary and acquired prothrombotic conditions was performed in addition to autoimmune and vasculitis serology. All of them did not reveal any changes. A brain MRI done within 24 hours after hospital admission showed recent ischaemic foci involving the left internal parietal region and right posterior frontal juxtacortical and right internal parietal (figure 3). It also revealed a left superior cerebellar hemispheric sequelae lesion (figure 4). Other chronic lesions were described involving right thalamic lacunar infarction, left protuberancial lacunar infarction and bilateral cerebellar hemispheric lacunar infarcts. In the absence of other typical factors as arterial hypertension for a stroke, imaging evidence of both old and acute strokes in more than one vascular territory, it was determined that the PAVM was a probable conduit for right-to-left paradoxical embolic phenomena.

Figure 3.

MRI-Diffusion-weighted imaging (DWI) sequence showing right posterior frontal juxtacortical and right internal parietal infarction.

Figure 4.

MRI-DWI sequence showing cerebellar sequelae.

Treatment

The case was discussed in a multidisciplinary meeting, and a conservative approach was decided, considering the patient’s age, clinical status and risk of intervention. She started low-molecular-height heparin (1 mg/Kg every 12 hours).

Outcome and follow-up

During the hospitalisation, the patient developed urosepsis secondary to a multiresistant Escherichia coli spp. She is still being treated with piperacillin/tazobactam which prevents the patient from discharged.

Discussion

PAVMs are structurally abnormal vascular communications between pulmonary arteries and veins bypassing capillary beds to create low-resistance, high-flow intrapulmonary right-to-left shunts.^{6 7} They are recognised as a cause of paradoxical brain embolism.⁸ Previously considered a rare condition, affecting 3, 2–4, 5 individuals per year or about 2–3 per 100 000 individuals,⁹ recent reports demonstrate a frequency of 1 per 2600¹⁰ with a male to female ratio varying from 1:1.5 to 1.8.¹¹

More than 80% of PAVMs are hereditary and associated with an autosomal dominant genetic disease, hereditary haemorrhagic telangiectasia (HHT).^{12 13} A triad of epistaxis, mucocutaneous or visceral telangiectasia, and a family history of PAVM, characterises HHT.² The present patient had no clinical signs or family history suggestive of HHT. The second most common aetiology of single PAVMs seems sporadic, generally solitary.¹⁴ However, it can only be considered after HHT has been sought out and excluded in the subject and family members.¹⁵ PAVMs can also be secondary to hepato-pulmonary syndrome, caval pulmonary shunts or trauma.¹¹ Most PAVMs are diagnosed in the first three decades of life, but they can manifest from birth to the eighth decade.¹³ About 83% of PAVMs occur in the lower lung zones, with the upper zones’ involvement in 17% of the cases.¹¹

Approximately 13%–56% of individuals with PAVMs are asymptomatic, and the majority is detected incidentally.² When large or multiple, PAVMs increase the risk of paradoxical embolism due to right-to-left shunt effect.^{2 8} About 19%–59% of patients have acute neurological complications, frequently ischaemic stroke and brain abscess, as the presenting complaint.¹⁰ Other presenting symptoms may include dyspnoea, intrapulmonic haemorrhage, palpitations, cough and chest pain.² There are two mechanisms responsible for the symptoms. In the first, the reduced O2 partial pressure and oxygen saturation in the arterial system can lead to hypoxaemia, anaemia, haemoptysis, haemothorax and pulmonary hypertension.² The second mechanism is related to abnormal venous drainage resulting in pulmonary arterial hypertension and complications from paradoxical embolisation.²

Embolisation is the gold standard for the treatment of PAVMs, with the surgical resection reserved for the cases which have failed embolotherapy.⁶ The present case was discussed in a multidisciplinary meeting, and a conservative approach with anticoagulation therapy was decided, considering the patient’s age, clinical status and risk of intervention.

Learning points.

• The frequency of pulmonary arteriovenous malformation (PAVM) is about 1 case per 2600 individuals with a male to female ratio varying from 1:1.5 to 1.8.

• More than 80% of PAVMs are hereditary and associated with hereditary haemorrhagic telangiectasia.

• Right-to-left shunt formed by PAVM can result in significant paradoxical embolic phenomena, representing an uncommon but important cause of ischaemic stroke.

• Catheter embolisation and surgical resection are the methods of choice for the treatment of PAMVs.

Ethics statements

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