Pavm
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1. Pulmonary arteriovenous malformations (PAVMs) are rare vascular anomalies where abnormal dilated vessels provide a right-to-left shunt between the pulmonary artery and vein. 2. PAVMs are usually diagnosed through imaging like chest X-ray, CT, or MRI which show dilated vessels. Right-to-left shunting can be detected using echocardiography, oxygen studies, or pulmonary angiography. 3. Treatment involves embolization to occlude the abnormal vessels which successfully treats over 99% of PAVMs. Surgery is an alternative for cases that cannot be embolized or if embolization fails.
Pavm
- 2. Introduction • Rare vascular anomalies of the lung, in which abnormal dilated vessels provide a right-to-left shunt between the pulmonary artery and vein. • Also known as pulmonary arteriovenous fistulae, pulmonary arteriovenous aneurysms, cavernous angiomas of the lung, and pulmonary telangiectases • First described by T. Churton in a 12 year old boy with epistaxis and hemoptysis.
- 3. Introduction • They are generally considered direct high flow, low- resistance fistulous connections between the pulmonary arteries and veins. • Important consideration in the differential diagnosis of common pulmonary problems, including hypoxemia, pulmonary nodules, and hemoptysis. • Mostly congenital in nature however they may be acquired due number of secondary causes.
- 4. Introduction
- 5. Epidemiology • Female predilection with around 1.5 to 1.8:1 though more common in the male infants in neonatal age. • The estimated incidence is thought to be around 2-3 per 100,000. • Around 10% of cases of PAVM are identified in infancy or childhood, followed by a gradual increase in the incidence through the fifth and sixth decades. • Approximately 70% of the cases of PAVM are associated with HHT.
- 6. Etiology • Mostly congenital in nature and due to HHT in majority of cases • Most common acquired cause is hepatic cirrhosis • They are also associated with surgeries for CHD including classic glenn shunt • HHT has an autosomal dominant inheritance • Endoglin, the most abundant TGFb binding protein that is found on endothelial cells, has been identified as the HHT gene mapping to locus 9q3, and is presently referred to as the gene for HHT 1.
- 7. Etiology • Hereditary hemorrhagic telangiectasia • Hepatic cirrhosis • Penetrating chest trauma or congenital heart surgery • Mitral stenosis • Schistosomiasis • Actinomycosis • Fanconi's syndrome • Metastatic thyroid carcinoma • Status post surgery for congenital heart disease • Idiopathic
- 8. Natural History • True mortality and morbidity data are unknown • Mortality is usually attributed to the complications of PAVM like stroke and brain abscess, as well as hypoxemic respiratory failure and life-threatening hemoptysis or hemothorax. • Most PAVMs remain stable in size. However, approximately 25 percent will enlarge slowly, usually at a rate of 0.3 to 2 mm/year. • PAVMs do not spontaneously resolve.
- 9. Pathology • Analogus to arterio-venous malformations else where in the body having an afferent feeder artery and a efferent draining artery. • PAVM may appear macroscopically as a large, single or multi-lobulated sac, a plexiform mass of dilated vascular channels, or a dilated and tortuous direct anastomosis between an artery and vein. • usually thin-walled, consisting of a single layer of endothelium and variable amounts of connective tissue stroma
- 10. Pathology • PAVMs are supplied by pulmonary arteries in about 95 percent of cases and are usually drained by pulmonary veins; however, they may occasionally be fed by systemic arteries (ie, the bronchial artery) and/or drain into the left atrium or inferior vena cava. • When PAVMs are fed by systemic arteries, hereditary hemorrhagic telangiectasia (HHT) is usually not the cause of the PAVM
- 11. Pathology • Most solitary PAVMs are seen in bilateral lower lobes, the left lower lobe being the most common location, followed by right lower lobe, left upper lobe, right middle lobe, and right upper lobe • PAVMs are usually found in close proximity to the visceral pleura or embedded in the outer third of lung parenchyma.
- 12. Classification • Pathological classification • simple type: commonest; has a single segmental artery feeding the malformation; the feeding segmental artery may have multiple subsegmental branches that feed the malformation, but must have only one single segmental level • complex type: have multiple segmental feeding arteries (~20%) • diffuse type: rare (~5% of lesions); the diffuse form of the disease is characterised by hundreds of malformations; some patients can have combination of simple and complex AVMs within a diffuse lesion
- 13. Classification • Anatwabi et al in 1965 • group I: multiple small arteriovenous fistulas without aneurysm • group II: large arteriovenous aneurysm • group III – large arteriovenous aneurysm (central) – large arteriovenous aneurysm with anomalous venous drainage – multiple small arteriovenous fistulae with anomalous venous drainage • group IV – large venous aneurysm with systemic arterial communication – large venous aneurysm without fistula • group V: anomalous venous drainage with fistulae
- 14. Pathophysiology • In contrast to systemic arteriovenous malformation, PAVMs do not affect cardiac haemodynamics. Cardiac output, cardiac index, pulmonary capillary wedge pressure, heart rate, blood pressure, and the electrocardiogram are usually within normal limits. • Degree of shunt is what determines the clinical effects on the patient. • The peripheral oxygen saturation is low and as expected does not normalise with 100% oxygen.
- 15. Clinical Features • pulmonary symptoms in only 20 to 65 percent (approximately 40 percent) and the remainder are asymptomatic, typically found incidentally on chest imaging. • The most common pulmonary symptoms are dyspnea in 13 to 56 percent and hemoptysis in 7 to 30 percent • Patients with underlying HHT often shows symptoms attributable to this disorder including epistaxis and mucocutaneous telangiectases
- 16. Clinical Features • PAVM, and is seen in almost all patients who have associated clubbing • it has been noted clinically that symptoms such as dyspnea are sometimes strikingly minimal when compared with associated signs such as cyanosis and clubbing • patients also have platypnea • This phenomenon is believed to be secondary to a decrease in blood flow through PAVM in the dependent portions of the lungs upon assuming the supine position.
- 17. Clinical Features • Epistaxis, which is caused by bleeding from mucosal telangiectases and reflects the high incidence of HHT in patients with PAVM. • Epistaxis is characteristically spontaneous or precipitated by minor trauma. Epistaxis is an early symptom specially in patients with HHT. • Bleeding from telangiectases on the skin and in the GIT is seen in patients with PAVM and HHT. • The incidence of gastrointestinal hemorrhage in patients with HHT is 15 to 30%.
- 18. Clinical Features • In a sizeable number of patients (43%–67%), a history of neurological symptoms—that is, headache, vertigo, paresis, numbness, paresthaesia, syncope, or confusion can be found. • The most common physical findings are cyanosis, clubbing, and pulmonary vascular bruit. • Pulmonary bruit is increased by inspiration and the Muller manoeuvre, this is caused by an increase in the pulmonary blood flow and decreased by expiration and the Valsalva manoeuvre, by decreasing venous return to the lung.
- 19. Diagnosis • PAVMs should always be suspected in patients who present with unexplained dyspnea or hypoxemia as well as in patients with nodules and a history of a stroke or brain abscess • The classical triad of dyspnea, cyanosis and clubbing may be found few patients. • Diagnosis rests on radiological demonstration of malformation, documentation of the right to left shunt in the setting of clinical scenario.
- 20. Diagnosis
- 21. Chest X Ray • Classic roentgenographic 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 with microvascular telangiectases may have normal chest radiographs, or only a vague increase in pulmonary vascular markings.
- 22. Chest X Ray
- 23. ABG and Orthodexia • Patients with diffuse PAVMs are uniformly hypoxemic with a mean arterial oxygen tension (PaO2) of about 47 mmHg. • Orthodeoxia is the laboratory correlate of platypnea. It is defined as a decrease in the oxyhemoglobin saturation by 2 percent or more when rising from the supine to the upright position
- 24. Echocardiography • Transthoracic contrast echocardiography — TTCE (also known as “bubble study”) is the preferred initial test. • TTCE identifies PAVM-associated shunt with a sensitivity, specificity, positive predictive value, and negative predictive value of 100, 49, 32, and 100 percent, respectively. • TTCE involves the injection of echocardiographic contrast, usually 10 to 20 mL of agitated saline into a peripheral vein while simultaneously imaging the right and left atria. • The contrast is normally visualized in the right atrium soon after injection and should not be visualized in the left cardiac chambers at all
- 25. Echocardiography When microbubbles are seen in the left atrium • within one cardiac cycle of their appearance in the right atrium, this is typically associated with an intra- cardiac shunt • within three to eight cycles is consistent with an intra-pulmonary shunt • within one to three cardiac cycles the location of the shunt is indeterminate
- 26. Echocardiography • Grade 0 – Grade 0 refers to no bubbles reaching the left ventricle (ie, no right-to-left shunt). • Grade 1 – Grade 1 refers to fewer than 30 bubbles seen in the left ventricle. should undergo yearly observation. • Grade 2 or 3 – Grade 2 shunt (30 to 100 bubbles in the left ventricle) or grade 3 shunt (>100 bubbles in the left ventricle)
- 27. 100% Oxygenation • It can be determined by the 100 percent oxygen method, which involves measuring the arterial oxygen tension (PaO2) and saturation (SaO2) and the arterial carbon dioxide tension (PaCO2) after breathing 100 percent oxygen through a mouthpiece or airtight mask for 15 to 20 minutes and then using those values to calculate the shunt fraction. • A shunt fraction of >5 percent is considered abnormal.
- 28. Exercise Tolerance • Symptom-limited incremental exercise resulted in a decrease in SaO2 from 86% at rest to 73% with peak exercise. Despite this impressive degree of desaturation, exercise capacity was generally well preserved with 60% patients achieving 70% of predicted maximal workload. • 6 minute walk test may also be done.
- 29. Chest CT • CT is often the diagnostic imaging modality of choice. • The characteristic presentation of a PAVM on non- contrast CT is a homogeneous, well-circumscribed, non-calcified nodule up to several centimeters in diameter or the presence of a serpiginous mass connected with blood vessels • Contrast injection demonstrates enhancement of the feeding artery, the aneurysmal part, and the draining vein on early-phase sequences.
- 30. Chest CT • If the CT scan shows one or more PAVM with a feeding artery diameter (FAD) ≥2 to 3 mm diameter, the patient should be referred for pulmonary angiography and potential embolotherapy. • If the CT scan shows PAVMs with a FAD <2mm, in most patients pulmonary angiography may be deferred unless patients have clinical features suggestive of symptomatic PAVM. • If the CT scan is negative for PAVM and shunt is present on TTCE, microscopic PAVMs may be responsible for the shunt
- 31. Chest CT
- 32. Pulmonary Angiogram • Pulmonary angiography is the gold standard test for defining the vascular anatomy of PAVMs that are identified on prior CT as suitable for embolotherapy. • During angiographic testing, contrast should be directly injected into the feeding artery or a distal pulmonary artery (ie, hyper-selective angiography) to accurately define the angioarchitecture of individual lesions.
- 35. MRI • Three-dimensional contrast–enhanced MR angiography has is considered the MR technique of choice for imaging vascular structures in the thorax 10. Most lesions within the lung have a relatively long relaxation time and produce medium to high intensity signals. Lesions with rapid blood flow within result in a signal void and produce low intensity signals
- 36. Treatment modalities • Surgical resection was first reported in 1942 and was the mainstay of treatment till 1980s • Successful percutaneous embolization by Taylor in 1978 opened up new therapeutic modality. • Percutaneous embolization is now preferred modality of choice. • May use – Balloon embolization – Coil embolization
- 38. Surgery • Surgical resection of PAVMs is indicated in patients who fail embolotherapy, develop serious bleeding complication despite embolotherapy, have intrapleural rupture of the PAVM, or have untreatable contrast allergy and lesions not amenable to embolotherapy. • Different surgical techniques have been employed which include local excision, segmental resection, lobectomy, ligation, and even pneumonectomy.
- 39. Surgery • Lung conserving resection, local resection, or segmentectomy is the procedure of choice whenever possible. Staged bilateral thoracotomies were performed in a case of an extensive bilateral PAVM. • PAVM surgery has the same risk as any other thoracic surgery procedure, but when properly performed in well selected patients, it results in minimal morbidity and mortality
- 40. Surgery
- 41. Embolisation • embolotherapy is the mainstay of treatment as most PAVMs (>99 percent) can be successfully treated with this therapy. • PAVMs with FAD ≥3 mm are targeted for embolization and smaller PAVMs are embolized, if technically feasible. • distal lesions with hyperacute branching of the pulmonary artery or of the feeding artery itself may make it technically difficult to access the PAVM for coil placement
- 42. Embolisation • most patients who undergo embolotherapy, symptoms improve and complications are avoided. • However, in a small percentage (<20 percent) the pulmonary arteriovenous malformation (PAVM) will not be successfully occluded, the PAVM recanalizes, or a new PAVM develops.
- 43. Embolisation
- 44. Embolisation
- 45. Case