Off-Pump Coronary Artery Bypass Grafting in a Patient with Lymphangioleiomyomatosis (LAM)

To The Editor, Lymphangioleiomyomatosis (LAM) is a chronic, progressive, and complex disease that almost always affects women. Women of childbearing age are frequently affected, albeit it is seen in the post-menopausal age group as well. LAM has a prevalence of 1 to 5 in 10,00,000.[1] Somatic mutations in the TSC1 gene on chromosome 9q34 and TSC2 gene on chromosome 16p13.3 cause aberration in hamartin and tuberin proteins leading to the uninhibited proliferation of cells known as LAM cells.[1] The hallmark of pulmonary disease is the cystic remodeling of pulmonary parenchyma mediated by LAM cell-derived matrix metalloproteinases.[1] In providing perioperative care for a patient with LAM, the critical concern is pulmonary dysfunction. A pulmonary pathology like LAM would increase the risk of perioperative morbidity and mortality. We discuss the perioperative management of a LAM patient undergoing off-pump coronary artery bypass grafting (CABG). CASE HISTORY A 68-year-old hypertensive woman with triple vessel coronary artery disease (CAD) was scheduled for CABG. A preoperative computed tomographic (CT) scan of the chest revealed bilateral diffusely spread numerous thin-walled well-circumscribed cystic lesions of varying sizes with ground glass opacities in the intervening lung parenchyma [Figure 1]. LAM was the diagnostic possibility and intraoperative lung biopsy was planned for definitive diagnosis. A preoperative spirometry revealed restrictive features with forced expiratory volume measured in the first second (FEV1) of 54% of the predicted normal value, increasing to 56% post-bronchodilator administration. Forced vital capacity (FVC) was 55% of the predicted value, and the FEV1 to FVC ratio was 100% of the predicted value. Preoperative inhaled bronchodilators (levosalbutamol and tiotropium) were started. An ultrasound examination of the abdomen to evaluate for the extrapulmonary manifestations of LAM was unremarkable.Figure 1: CT scan of the chestIntraoperatively, the target peak airway pressure was ≤20 cm of water (cm H2O) as a precaution against pulmonary cysts’ rupture. The intraoperative course was uneventful, and the patient was extubated at the end of surgery. The postoperative respiratory physiotherapy sessions predominantly included incentive spirometry with Respirometer® (Romsons, New Delhi, India). Additionally, vibratory positive expiratory pressure therapy was delivered with an Acapella device® (Smiths Medical, Dublin, OH, USA). The histopathological evaluation of the lung biopsy (sample taken intraoperatively) revealed cystically dilated alveolar spaces. The walls of these spaces were lined with bundles of smooth muscles. There was peribronchial lymphomononuclear cell inflammation, and immunohistochemistry was positive for human melanoma black (HMB-45) reactivity. These features clinched the diagnosis of LAM. At discharge, the patient was counseled about air travel risks, the importance of pulmonary rehabilitation, and was started on sirolimus therapy. DISCUSSION The features of pulmonary disease in LAM, apart from cyst development, are interstitial thickening, alveolar damage, and chronic fibrosis.[1] Multiple thin-walled cysts on CT scan are the characteristic feature of LAM.[2] However, other cystic pulmonary diseases should be excluded. Hence, lung biopsy is crucial for definitive diagnosis.[1] LAM's extrapulmonary manifestations include generalized lymphadenopathy, large cystic lymphoid masses in the abdomen, and chylous ascites.[1] Hence, a detailed history, physical examination, and appropriate imaging to screen for systemic manifestations become crucial. Pulmonary dysfunction in LAM can be obstructive, restrictive, or of the combined variety.[1] The age-related decline in lung function is approximately three times more rapid in LAM patients than in normal subjects.[3] A significant positive bronchodilator response on spirometry is associated with a faster decline of FEV1.[3] Irrespective of the bronchodilator response on spirometry, bronchodilators have a therapeutic role in these patients.[3] Inhaled and systemically delivered corticosteroids have no role in managing a LAM patient as per scientific literature.[3] Pulmonary cysts increase in size when exposed to a hypobaric environment, and the risk of spontaneous pneumothorax is about 1–2% per 100 flights.[4] So, our patient was cautioned about air travel. LAM: Implications for the cardiac anesthesiologist Firstly, it is crucial to avoid high peak airway pressures and use low tidal volumes to avoid iatrogenic pneumothorax.[5] Due to the cystic pulmonary pathology, LAM patients are more prone to pneumothorax and chylothorax. Secondly, an off-pump approach to CABG might be preferable to the on-pump approach in LAM patients. It avoids cardiopulmonary bypass (CPB) associated pulmonary insults like increased microvascular permeability in the lung, increased pulmonary vascular resistance, increased pulmonary shunt fraction, and intrapulmonary aggregation of leukocytes and platelets. Finally, sirolimus therapy is a crucial therapeutic measure in LAM patients who have FEV1<70% predicted.[1] Hence, our patient was advised to follow-up with pulmonologists for sirolimus therapy after getting discharged. To conclude, LAM is a rare lymphoproliferative disease. Evaluating for multisystem disease involvement is essential to deliver appropriate perioperative care. The key to uncomplicated and safe perioperative care is to understand the intricacies of the pulmonary pathophysiology, meticulous planning of intraoperative ventilatory management, and intensive postoperative respiratory physiotherapy combined with adequate analgesia. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. Acknowledgement We thank Dr. Manoj Goel, Dr. Nikhil Kumar, and Dr. R.K. Verma from the department of pulmonology, cardiology, and radiology, respectively, at Fortis Memorial Research Institute, for their expert advice regarding patient management.

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