Clinical Meetings at RH Year 2008

2008 Clinical Meeting TKOH - A Man with Polycythaemia

Drs LAM Soe-tjhoen, CHAN Sik-nga & TSE Pak-yiu
Department of Medicine, Tseung Kwan O Hospital

Case History

A 25-year-old gentleman was referred to our medical general outpatient clinic from a general practitioner for work up of elevated haemoglobin (Hb) level of 19g/dL with haematocrit (Hct) of 55%. He was an aeroplane technician. He did not smoke or drink and had previously enjoyed good past health. He had on and off small amount of sputum irritating his throat since 18-19 yrs old. Moreover, he complained of getting tired easily and had recurrent upper respiratory tract infections. He lived in Hong Kong all along and had never lived in high altitude. There was no history of lung disease, heart disease, renal disease or family history of elevated haemoglobin. He had no skin itchiness or burning pain over hands and feet. In addition, he had no vertigo, tinnitis, headache or visual disturbance. There was no history of previous cerebrovascular accident. He had a bone marrow aspiration done in private which showed the haemopoiesis was normoblastic and active. There was no relative hyperplasia. Megakaryocytes were adequate in number and morphologically unremarkable. Iron store was present. USG abdomen performed in private showed normal liver size and echo texture without any focal liver mass. There was no splenomegaly and kidneys were normal.

Physical examinations were mostly unremarkable. The blood pressure was normal. Initial blood tests showed Hb 19.5g/dL, Hct 0.56L/L, white blood cell 5.5 x10^9/L, platelet 211 x10^9/L with normal liver and renal function tests. His CXR on presentation was shown in Fig. 1.


On further investigations, red cell mass was 1958ml (normal range 1144-1906ml). Haemoglobin pattern was normal. ABG showed hypoxemia. ABG at room air was pH 7.434, pCO2 4.26kPa, pO2 7.9kPa, HCO3 20.9mmol/L, base excess -2.1mmol/L and SaO2 91.8%. Echocardiogram showed EF 60% with normal LV size. There was no RWMA, valvular dysfunction or ASD/VSD/PDA. There was also no evidence of pulmonary hypertension.

The patient was then referred to our respiratory clinic for workup of secondary polycythaemia due to hypoxemia. On further questioning, his exercise tolerance was decreased and the patient had occasional blood stained sputum in recent 3 years. Sputum for AFB was negative for twice. Sputum cytology showed inadequate for diagnosis for twice. A-a gradient was calculated to 6.6Kpa. Lung function test was done which showed no obstructive ventilatory defect. TLC and DLco were both within normal limits. He was also found to have orthodeoxia with SaO2 93%RA while sitting and SaO2 97% RA when lying. Transesophageal echocardiogram was done which showed no intracardiac shunt. Agitated saline injection showed no right to left shunt.

CT thorax was performed subsequently. Four arteriovenous malformations (AVMs) ranged from 0.6cm to 1.5cm were detected in right lower lobe (Fig.2). They all received single artery supply from branches of right lower lobe pulmonary artery and drained to a single vein towards right inferior pulmonary veins. This patient had no telangiectasia over face, chest and upper extremities. There was no mucosal telangiectasia. He had no epistaxis or history of gastrointestinal bleeding. He had no family history of hereditary haemorrhagic telangiectasia (HHT).


He was then referred to Queen Elizabeth Hospital for further management. Pulmonary angiogram was performed and showed four AVMs at right lower lobe. In addition, multiple fine nodularities were noted at background of right lung parenchyma, features probably due to very fine tiny AVM and were not embolizable. These 4 AVMs at right lower lobe were embolized with platinum coils and post embolization angiogram showed satisfactory occlusion (Fig. 3 & 4). Fig. 5 showed the CXR after embolization.


After treatment, his exercise tolerance was similar. Orthodeoxia was still present with SaO2 92% RA while sitting and 95% RA when lying. His Hb level was 18.3g/dL. His calculated shunt fraction was 17.1% (normal  5%). The seemingly unimproved symptoms and laboratory findings of the patient could probably be explained by the presence of multiple tiny non-embolizable AVMs in the right lung parenchyma as mentioned above.

Discussion
Pulmonary arteriovenous malformations (PAVMs) are caused by abnormal communications between pulmonary arteries and pulmonary veins, which are most commonly congenital in nature. However, PAVMs may also occur in a variety of acquired medical conditions, such as hepatic cirrhosis. About 70% of PAVMs are associated with hereditary haemorrhagic telangiectasia (HHT) / Osler-Weber-Rendu Disease and about 15-35% of individuals with HHT have a PAVM1. PAVM is an uncommon disease.

PAVM can be classified as either simple or complex. Simple type is defined as those with a single feeding segmental artery and a single draining vein and it accounts for about eighty to ninety percent of PAVM. The rest are complex, with two or more feeding arteries or draining veins2, 3 & 4.

Patients with PAVM have a wide spectrum of symptoms ranging from none to life-threatening hemoptysis. About 76% of patients have symptoms referable to the PAVM or underlying HHT, such as epistaxis, dyspnea, haemoptysis, bleeding from telangiectases and platypnoea5.

Spirometry of patients with PAVMs is usually within normal limit and minute ventilation is usually increased6. Pulmonary artery pressure is normal or low in nearly all of PAVM patients1.

The chest radiograph is abnormal in the majority of patients with symptoms attributable to PAVM. The classic chest radiograph appearance of a PAVM is that of a round or oval mass of uniform density, frequently lobulated but sharply defined, more commonly in the lower lobes, and ranging from 1 to 5 cm in diameter. Patients who have multiple PAVM usually have 2 to 8 lesions. Hemorrhage into contiguous parenchyma, or atelectasis may obscure the PAVM shadows in chest radiograph. If patients have microvascular telangiectases, chest radiographs can be normal, or there may be just a vague increase in pulmonary vascular markings at the bases. Sometimes, the chest shadows of PAVM may come and go1.

Shunt fraction measurement is commonly measured by the 100% oxygen method. Radionuclide perfusion lung scanning is another method for shunt fraction measurement. However, it is expensive and not routinely available in many centers5. Contrast-enhanced echocardiography is useful to look for any intra-cardiac or intra-pulmonary shunt. Computerized tomography of the chest evaluates PAVM vascular anatomy and is very sensitive for PAVM detection8. Pulmonary angiography is the gold standard in the diagnosis of PAVM. It is used to define the angioarchitecture and is necessary if resectional or obliterative therapy is being considered 9.

About 25% of PAVM gradually enlarge, usually at a rate of about 0.3 to 2mm per year7 & 10. Modern series of untreated PAVM have mortality of 7.7 to 15.8%7, 11, 12 & 13. Most deaths are related to stroke, cerebral abscess, haemoptysis, or haemothorax.

The tradition indications to treat PAVMs are progressive PAVM enlargement and development of complication, like paradoxic embolization and symptomatic hypoxemia14.

Surgical intervention, including vascular ligation, local excision, and lobectomy or pneumonectomy, was the method of choice for treating PAVM between 1942 and 1980. Postoperative acute right heart failure occasionally develops, likely due to removal of the low resistance PAVM15.

Embolization therapy is a form of treatment based on the angiographic occlusion of the feeding arteries to a PAVM. The largest series of embolotherapy for PAVM involves the successful occlusion of 415 PAVMs in 155 patients, with a procedural success rate of 100%16. The procedural success rate has been over 98% in cumulative series, 1 with no reports of procedural mortality.

Because of considerable morbidity and mortality of PAVM without treatment, all patients who are symptomatic due to PAVM, all patients with PAVM greater than 2cm in diameter, and all patients whose PAVM have feeding arteries at least 3mm in diameter, or some suggested that if the lesion is feasible for embolotherapy, should be treated with either embolotherapy or surgery. Post embolotherapy management includes lifelong antibiotics prior to invasive procedures and routine follow up computerized tomography of chest and shunt fraction measurement5.

Acknowledgement
We would like to thank Department of Radiology and Imaging of Queen Elizabeth Hospital for giving us the permission to use the pulmonary angiogram and CXR film for illustration.

References:

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