Since the first successful resection of pulmonary arteriovenous malformation (PAVM) was made in 1942,1 different surgical techniques have been employed including local excision, segmental resection, lobectomy, ligation, and even pneumonectomy. In 2001 Schröder et al2 described a lung-saving procedure of fistulectomy as an alternative to traditional surgical options.
In this report, we describe the preliminary clinical outcomes of fistulectomy for PAVM in 6 selected patients.
From July 2003 to July 2008, fistulectomies were performed in 6 patients with PAVM who had symptoms of dyspnoea on exertion. Three patients had a history of neurological symptoms including headache, vertigo, numbness and paresthaesia. On physical examination, cyanosis was obvious in 5 patients, clubbing in 4, and pulmonary vascular murmur in 4. Typical clinical manifestations of Osler-Weber-Render disease or hereditary hemorrhagic telangiectasia (HHT) such as telangiectases of the skin and mucosa, epistaxis and melaena were not present in all patients.
PAVMs were diagnosed by angiography in 1 patient and by contrast computed tomography with three dimensional reconstructions in the other 5 patients. Exclusion criteria for fistulectomy included diffuse multiple PAVMs, mural thrombus, hemorrhagic tendency and severe lung dysfunction.
All patients provided written informed consent for this study, which was approved by the Ethical Committee of Beijing Anzhen Hospital. Preoperative data are summarized in Table 1.
The operation was performed through muscle-sparing thoracotomy via one-lung ventilation. The precise location and periphery of the anomaly were detected by entering the thoracic cavity. The pulmonary artery and lobe vein were dissected free and encircled with tapes as precautionary measure in case of injury during operation for aneurysms and relevant vessels. The fundi of fistulas were gently dissected from the adjacent lung parenchyma to the origin of the main feeding arteries and draining veins. The small vessels in the lung bed were dissected and ligated. After ligation of the main feeding arteries and draining veins, the entire fistulas were removed. The lungs were reventilated, and then air leakage or injuries of the lung parenchyma were treated with sutures. The chest was closed routinely with one or two chest drains.
Bilateral PAVMs were treated respectively in one-stage operation for patient 1 and in staged operation for patient 2 with an interval of one month.
Values of variables are expressed as mean ± standard deviation. Comparisons of variables were made with the Student's unpaired t test. A P value < 0.05 was considered statistically significant.
The mean time for the procedure was (155.7±43.0) minutes (range, 125 to 250 minutes) and the mean blood loss in operation was (190.0±60.6) ml (range, 150 to 320 ml). No severe injuries happened and pulmonary vessel clamping was not needed. All patients were extubated within 2 hours after operation. There were no major procedure-related complications including death, bleeding, respiratory failure and stroke. The average post-operative hospital stay was (8.0±1.4) days (range, 7 to 10 days). PaO2 in room air increased from (57.3±12.5) mmHg before operation to (90.1±11.7) mmHg after discharge (P <0.01). One patient received staged transcatheter embolotherapy for the remained small PAVMs in the opposite lung 2 weeks after operation. The perioperative outcomes are shown in Table 2.
The 6 patients were followed up postoperatively for 9 months to 5 years. They were free of symptoms and O2 saturation remained >90% while breathing room air during the follow-up. Five patients were subjected to postoperative CT scan once 6 to 12 months, and no evidence of recurrence was found.
Pathological examination demonstrated that PAVM was composed of a large, single sac or a plexiform mass of dilated vascular channels which were thin-walled and lined with a layer of the endothelium. The diameter of the feeding arteries to 9 fistulas resected ranged from 1.0 cm to 2.4 cm (mean (1.7±0.6) cm).
Pulmonary arteriovenous malformations are caused by abnormal communications between the pulmonary arteries and pulmonary veins, often through a thin-walled aneurysm, which are most commonly congenital in nature.3 Patients with PAVMs are at risk of life-threatening complications including stroke, brain abscess, or massive hemothorax or hemoptysis. A consensus on PAVM management has not been reached mainly because of the uncertainty of the natural history of the disease. But there is evidence that PAVMs progressively enlarge over a period of time and the incidence of progression is higher in patients with untreated PAVM. The morbidity associated with PAVM is significantly higher in untreated patients than in treated patients.4 Generally, treatment is recommended for all symptomatic patients and asymptomatic patients with lesions greater than 2 cm on chest radiography or with feeding vessels greater than 3 mm in diameter.5
The current preferred treatment for the majority of patients with PAVMs is percutaneous embolotherapy using coils or balloons. Being less invasive and easy to repeat, this method has definite advantages over surgery. It is especially suitable for the elderly who are poor surgical candidates and for patients whose lesions are too numerous to be resected.6 However, even with advantage of less invasiveness and good initial results, embolization is associated with a higher subsequent recurrent rate compared with surgery. The need for a repeat procedure on follow-up is not uncommon, which may cause an increased medical cost. The most common mechanism of recurrence is recanalization of the originally occluded artery. Reperfusion of PAVM secondary to post-procedural growth of accessory vessels and bronchial artery hypertrophy may also occur. Reperfusion risk appears to be increased with increasing diameter of the PAVM feeding artery, which hints a possibility of incomplete treatment for these patients.7 And large feeding arteries may be the source of accidental systemic embolization. Coils or balloons may escape from the malformation if the feeding artery does not narrow downstream.
Therefore, surgical resection remains the treatment of choice for at least some patients. It is indicated for patients who fail to embolotherapy, develop serious bleeding complications, and have untreatable contrast allergy or lesions unsuitable for embolotherapy.
In our series, PAVMs under consideration for fistulectomy were all large and fed by huge arteries, which appeared to be unsafe for the placement of coils or balloons. And this opinion was agreed by the interventional radiologist.
Open-chest lung resections, segmentectomy, lobectomy or pneumonectomy have been successfully performed to treat PAVM. Operatively, all existing PAVMs should be removed. And at the same time, conservative operations, such as wedge resection, local excision and segmentectomy are preferred over conventional lobectomy or pneumectomy to save normal lung parenchyma if main PAVMs can be removed.4,8 Video-assisted thoracoscopy has been used in the resection of PAVM for minimized injury to respiratory muscles and a good cosmetic outcome.9,10
The original procedure of fistulectomy introduced by Schröder et al2 is a complete and lung-saving operation. The rationale of this technique is shown by a combination of radical surgical treatment and the avoidance of lung loss. Schröder et al2 described the key principles of fistulectomy in his case report and we did similarly with some modifications.
Schröder et al2 recommended cross-clamping of the artery and vein of the segments involved and a systemic injection of heparin (0.5 mg/kg). In our patients, we dissected the vessels and encircled them with tapes just as a precautionary measure but did not block the circulation and also we did not use heparin regularly. We consider that it is more advisable to clamp the related vessels only in case of severe injury of fistulas or main vessels. With use of a preset device, it will be convenient to control bleeding as the common practice of pulmonary angioplasty in lung surgery. And in other cases, avoiding unnecessary heparinization can protect clotting. This is especially important in an operation where the scope of dissection being wide. During the operation for our patients, handling of aneurysm was careful and gentle. Manipulations of the fistulas were limited to the distended part of their walls to avoid migration of emboli at the internal arteriovenous capillary interface.
From our experience, the ideal indication for fistulectomy is isolated, large PAVM located closely below the visceral pleura with a single feeding artery and draining vein. Pathologically PAVMs are usually found in close proximity to the visceral pleura or embedded in the outer third of the lung parenchyma and the reported incidence of single PAVMs ranges from 42% to 74%.11 Eighty to ninety percent of PAVMs are related to a single feeding artery and a single draining vein.12 Pathological studies have shown that fistulectomy is appropriate for most PAVMs. Mural thrombus in the fistula is a contraindication for fistulectomy because of high risk of paradoxical embolization. For those with multiple PAVMs in bilateral lungs, one-stage or staged bilateral fistulectomies can be chosen according to the patient condition. In cases where small lesions coexisted with isolated, large PAVMs, operation in combination with an embolization procedure is advisable.13 Massive hemoptysis after intrabronchial rupture or hemothorax after subpleural rupture of PAVM is rare but potentially fatal complication. Emergency fistulectomy can be considered in these conditions. Diffuse PAVMs are usually related to HHT and are not indicated for surgical treatments including fistulectomy.
Successful fistulectomy lies in the choice of candidates. It is necessary to define and to analyze the angioarchitecture of PAVM before surgical treatment. Angiography is the gold standard diagnosis of PAVM traditionally. But as an invasive method, it is labor cost and radiation intensive. Contrast enhanced computed tomography with three dimensional reconstructions is a valuable tool in defining the vascular anatomy of PAVM. The superiority of CT scan is attributed to the absence of superimposition of lesions on transaxial computed tomography. In our center, this technique is widely used for diagnosis or preoperative evaluation of patients with PAVMs. Pulmonary angiography is limited to individuals intended for interventional therapy and seldom used for pure diagnosis purpose.
Fistulectomy seems to be more demanding compared with traditional lung resection procedures. But in practice it is uncomplicated from the point of surgical technique in well selected patients. After thoracotomy, it is usually not difficult to locate a PAVM by finding a protrusion from the pleural surface and palpating a thrill. The feasibility of dissecting fistulas fully from adjacent lung bed depends on the vascular structure and periphery of PAVMs. The most commonly encountered vascular anomaly in our series was a vascular plexus with enlarged channels. There was usually a thin layer of connective tissue stroma which is scant with communication with surrounding lung tissue and may allow for safe performance. Occasionally, the wall of anomaly was thickened by fibrous tissue and adhered to the lung bed. In these cases or where collateral vessels were tight with surrounding lung parenchyma, we preferred to dissect from the lateral side of the anomaly and would rather sacrifice a thin layer of lung tissue because the air leakage is easy to manage but improper damage of the thin wall of fistula will cause hemorrhea and possible air embolic event. And long time clamping of main vessels during hemostasis or vessel suturing will cause ischemia reperfusion injury. Obviously, the absolute lung saving is not always achievable in any case and safety comes in the first time.
In summary, fistulectomy is an acceptable surgical option for PAVM. It has the same risk as other surgical procedures, but has the special superiority and additional benefit of lung-sparing. When properly performed in well selected patients, it results in minimal morbidity and may serve as an alternative to lung resections.
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