Introduction

Pulmonary arteriovenous malformations (PAVMs) are characterized by an unusual communication between abnormal pulmonary arteries and pulmonary veins, which results in greater or lesser degrees of right-to-left shunting.

Patients with PAVMs may present with the Rendu-Weber-Osler syndrome (cutaneous and mucosal spider angiomas), dyspnea on exertion, hemoptysis, chronic heart failure or a major neurologic event such as a stroke or intracerebral abscess. The degree of chronic heart failure is dependent on the size of the right-to-left shunt.

Case Report

A 21-year-old woman was referred to our department for evaluation of massive hemoptysis. According to the history she had recently (2 weeks) become symptomatic (dyspnea especially on exertion, chest pain, cough, hemoptysis and fatigue). Vital signs were as follows: respiratory rate 16 breaths/minute, heart rate 82 beats/minute, temperature 36,9 ^o C. Physical examination revealed mild acral cyanosis, clubbing and a left lower posterior pulmonary murmur which increased during inspiration. Laboratory work-up detected polycythemia (Hematocrit: 49%, Hb: 16,2 g/dl). Results of coagulation studies and chemistry were normal. Room air arterial blood gas values were as follows: pH-7,40, PaCO₂-38 mm Hg, PaO₂-56 mm Hg.

Admission chest X-ray showed an abnormal shadow in the left lower lobe. Bronchoscopy did not reveal anything abnormal. An urgent chest computed tomography revealed a well-circumscribed mass in the left lower lobe connected by blood vessels to the hilum of the left lung (Figure 1). Pulmonary angiography was the next step of the diagnostic approach which confirmed the diagnosis of pulmonary arteriovenous malformation, providing information regarding size and location of the lesion and the vessels involved in the malformation (Figure 2).

Figure 1

Figure 2

According to the fact that hemoptysis was getting worse the patient underwent urgent left posterolateral thoracotomy through the 5 ^th intercostal space. A pulsating complex PAVM (dimensions: 4X5 cm), centrally located, occupying large part of the left lower lobe was found (Figure 3). The wall of the PAVM was flimsy and seemed to have the tendency to rupture easily. A typical left lower lobectomy was performed (Figure 4). The histopathological study of the resected lobe confirmed the diagnosis of PAVM (plexiform mass of dilated vessels with feeding vessels).

Figure 3

Figure 4

The postoperative period was straightforward with no problems. On 6 ^th postoperative day the patient became acyanotic with improved room air arterial blood gas values: pH-7,41, PaCO₂-37 mm Hg, PaO₂-79 mm Hg. She discharged home on 8 ^th postoperative day. Because of the fact that there is a strong association between PAVMs and hereditary hemorrhagic telangiectasia a detailed history concerning epistaxis, dyspnea on exertion, hemoptysis, cyanosis and pulmonary bruits-murmurs was detected to family members. Follow-up visits at 3, 6 and 9 months after the operation showed normal and asymptomatic condition.

Discussion

PAVM was first described in 1897 by Churton [₁], in a 12-year-old boy found to have multiple bilateral PAVMs on postmortem examination. They may be simple (single pulmonary artery to pulmonary vein communication) or complex (multiple feeding arteries and draining veins) and single (40%), multiple (40%) or bilateral (20%) [₂].The vast majority are congenital. Acquired lesions are rare and have been reported following surgery, trauma, pulmonary infection, metastatic carcinoma and hepatic cirrhosis. 36% of single lesions and 57% of multiple lesions are associated with hereditary hemorrhagic telangiectasia [₃]. 53% to 70% of PAVMs are found in the lower lobes. Women are affected twice as often as men, but there is a male predominance in newborns [₄]. PAVMs may be present at birth but in most cases they remain unrecognized until the late teenage years. Studies suggest that PAVMs grow during life.

The exact pathogenesis of PAVM is unknown. It is well known that the ingrowth of mesenchyme into the foregut pharyngeal pouch brings with it the capacity for the development of the pulmonary vasculature. During blood vessel development , primitive arteriovenous connections form to initiate the flow of blood. Subsequent vascular remodeling, results in normal vessel development. PAVMs result from unknown stimuli during the stage of arteriovenous communication in the retiform plexus [₅]. The large friable sac can be the source of severe hemorrhage. Other investigators have hypothesized that the cause is a defect in the terminal arterial loops, which allows dilatation of the thin-walled capillary sacs [₆].

The most common symptoms at the time of presentation include dyspnea on exertion, palpitations, hemoptysis or chest pain. Patients presenting with epistaxis , gastrointestinal tract bleeding, hematuria or neurologic symptoms should be evaluated for coexisting Weber-Rendu-Osler disease. As many as 75% of patients may have cyanosis, clubbing, pulmonary vascular bruits or murmurs on physical examination. Careful auscultation can detect murmurs that can be intensified by inspiring against a closed glottis (Muller's maneuver) and alleviated by the Valsalva maneuver. Ear, nose and throat examination may confirm the diagnosis of Weber-Rendu-Osler disease by demonstrating the presence of nasopharyngeal or oral mucosal telangiectasias. Neurologic symptoms, including headaches, confusion, dizziness, syncope and cerebral vascular accidents may arise from the associated hypoxia and secondary polycythemia or paradoxical emboli. Brain abscesses caused by paradoxical septic emboli have also been reported. There is also a reported association between multiple pulmonary AVMs and polysplenia [₇].

The primary physiologic abnormality is a right to left shunt from pulmonary artery to pulmonary vein, leading to hypoxemia and in extreme cases high output cardiac failure. The most common laboratory finding is reduced arterial oxygen tension, occurring in > 80% of cases. Hemodynamic measurements, including cardiac output, intracardiac, pulmonary arterial, and pulmonary capillary wedge pressures are usually within normal limits. Chest radiographs are abnormal in approximately 98% of patients with PAVM. The most common finding is a well-circumscribed, peripheral, noncalcified nodule(s) connected by blood vessels to the hilum of the lung. Pulmonary angiography remains the gold standard for diagnosing PAVM, providing information regarding size of the lesion, the location of the lesion, and the vessels involved in the malformation. Other modes of investigation include CT, contrast echocardiography, three dimensional MR angiography, fluoroscopy, perfusion lung scan and shunt evaluation.

Treatment of PAVM should be based on the size, number and location of the lesions and the specific complications as well as the patient's general condition. The therapy for symptomatic congenital PAVMs previously consisted of surgical resection entailing local excision, segmental resection, lobectomy or pneumonectomy. However, in the late 1970's percutaneous catheterization of the femoral vein and embolization of the malformation through a catheter positioned in the feeding pulmonary artery has become the treatment of choice. The advantages of this procedure arise from the avoidance of surgery, general anesthesia and loss of lung tissue and the fact that patients can undergo repeated procedures for recurrent or multiple PAVMs. Today percutaneous transcatheter embolization by coil or balloon is the treatment of choice. However in selected patients (large – diameter> 2 cm, centrally located PAVMs, urgent conditions) surgery plays an important role.

PAVMs constitute a rare cause of massive hemoptysis, accounting for approximately 2% of cases in large series [₈]. Pouwels and colleagues [₉] reported a case of life-threatening hemoptysis in which a right bronchial angiogram revealed a hypertrophic right bronchial artery, with hypertrophic branches running toward a large malformation in the right lower and middle lobes. Ference and colleagues [₁₀] reported massive hemoptysis or hemothorax in 11/143 patients (8%) with PAVMs and Weber-Rendu-Osler disease. There were four men and seven women. One patient died directly related to the pulmonary hemorrhage. Three of the seven women experienced pulmonary hemorrhage during pregnancy. In our case massive hemoptysis was the clinical manifestation of the PAVM. Due to its size (dimensions 4X5 cm) and location (central development), surgery (lobectomy) was our first option.

Pulmonary hemorrhage due to spontaneous rupture of a PAVM is a potentially life-threatening complication that should be treated aggressively. Although advances in interventional radiology have led to new therapeutic options (angiographic embolization with metal coils or balloon occlusion) surgery is a safe method of treatment of PAVMs in selected cases.

Correspondence to

N. Barbetakis M.D. Ph.D, Cardiothoracic Surgeon Anatolikis Thrakis 100B, Alexandroupolis, GR 681 00 GREECE. E-MAIL: nibarb@otenet.gr TEL: 0030 6972039345