Case presentation

A 14-year-old, 38 kg boy,with a severe form of Becker muscular dystrophy resulting in early onset of muscle weakness and cardiomyopathy was admitted with heart failure. He had been followed up as an outpatient and his heart failure had been managed with carvedilol, losartan, and furosemide. His brother had the same disease and died at the age of 14 years because of complications following paracorporeal assist device implantation.

The patient had severe left ventricular dysfunction and moderate mitral regurgitation. Fractional shortening was 12%. His cardiac index was 2 L/min/m² by thermodilution in the setting of anaesthetic-related hypotension. His pulmonary function was markedly decreased (forced vital capacity 44% of predicted, forced expiratory volume in 1 second: 48%, maximal forced expiratory flow: 36%). Initial diuretic-related weight loss was followed by progressive cachexia due to poor oral intake and inability to tolerate naso-enteral tube feeds.

At baseline, he could ambulate short distances but quickly became completely wheelchair dependent. It could not be ascertained to what extent his progressive muscle weakness and need for non-invasive ventilation were related to heart failure or his underlying muscular pathology. His life expectancy independent of heart failure was unclear. Despite maximal medical therapy including high-dose inotropes, he continued to deteriorate and was scheduled for device implantation.

In the context of a chronic debilitated state and severe heart failure, he developed fevers and pneumonia. Cultures were negative, but procalcitonin level was elevated at 0.30 ng/ml, and thus antibiotics were started. He was transferred to the intensive care unit with worsening heart failure, and required mechanical ventilation. We elected to proceed with ventricular assist device implantation.

A Heartware HVAD was implanted via median sternotomy using cardiopulmonary bypass without aortic cross-clamping. Owing to the fact that the patient was left-handed, the driveline was tunnelled out through the right subcostal region. The patient was weaned from bypass on nitric oxide, milrinone, and epinephrine.

Heparin and aspirin were initiated on post-operative day 1. Chest tubes were removed on day 3. He had bleeding and cardiac tamponade requiring emergent mediansternotomy and drainage on day 10. Another episode of bleeding into the left chest necessitated video-assisted thoracoscopic drainage of a haemothorax 10 days later. In both cases, the patient had a partial thromboplastin time of 50–60 seconds, an international normalised ratio of 1.1, and anti-Factor Xa level of 0.30–0.40 IU/ml.

After a failed attempt at liberation from mechanical ventilation, a percutaneous tracheostomy was performed in the intensive care unit on post-operative day 20. Following this, he made rapid progress weaning from mechanical ventilation and skeletal muscle strength improved. In the setting of oropharyngeal weakness, a percutaneous feeding tube was placed to ensure provision of adequate nutrition. His anticoagulation regimen was converted to aspirin and Coumadin.

The tracheostomy was decannulated after 2 months. He continued to receive physical and occupational therapy and regained skeletal muscle function equivalent to that at admission, and he is receiving ongoing, intensive outpatient therapy. Pre-discharge pulmonary function tests were similar: (forced vital capacity: 33%, forced expiratory volume1: 37%, maximal forced expiratory flow max: 52%). He has had no driveline infections and no clinical evidence of a thromboembolic event.

Comment

With the advent of smaller implantable ventricular assist devices, the use of these devices in children has increased considerably. This case of a patient with Becker muscular dystrophy and cardiomyopathy demonstrates a novel application for these devices, with the potential to alter the current management paradigm for patients with muscular dystrophy and heart failure.

In the setting of progressive skeletal muscle weakness, differentiating between physical limitation due to heart failure and deconditioning as opposed to that due to primary skeletal muscle pathology is difficult. Implantation of an assist device, rather than moving directly to transplant, provides advantages in these patients, including the opportunity to evaluate patients in the absence of left-sided heart failure.

The small size of the Heartware HVAD provides important advantages in smaller patients and those with skeletal muscle disease. It can be inserted in patients with significantly smaller size than the larger Heartmate II device; it is approved for use in patients with a body surface area ⩾1.5 m², but has been used in patients as small as 0.7 m².Reference Miera, Potapov and Redlin ³ Moreover, intra-pericardial placement may better preserve diaphragm function, which is important in patients with muscular dystrophy.

This patient’s clinical course illustrates several important features in the management of muscular dystrophy patients following cardiac surgery. Early and aggressive physical therapy and ambulation is critical. In retrospect, delaying the tracheostomy for 3 weeks was too long. The tracheostomy simplified care and enabled sedation weaning and increased physical activity. This resulted in rapid improvement in skeletal muscle strength and respiratory function. Although this patient was successfully weaned from mechanical ventilation and decannulated, muscular dystrophy patients are at risk for prolonged (and permanent) ventilator support. This possibility, along with the need for enteral tube feeding, should be discussed with patients and families before ventricular assist device implantation.

Implantation was delayed because of concerns for infection. In the meantime, the patient deteriorated rapidly and has required a longer course of inpatient rehabilitation post-operatively. We would recommend early implantation and early physical therapy and ambulation to minimise the rapid deconditioning apparent in patients with muscular dystrophy.

Thromboembolism prevention and resultant bleeding complications remain a significant issue in children on mechanical circulatory support.Reference Chen, Richmond and Charette ⁴ Rapid diagnosis and treatment prevented significant sequelae from either episode, but in children on ventricular assist devices, monitoring of anticoagulation using multiple tests including prothrombin time, partial thromboplastin time, anti-Factor Xa, and thromboelastograms is important. In addition, the use of minimally invasive surgical treatment of thoracic pathology including haemothorax allows for rapid recovery without the effects of a thoracotomy. Minimally invasive techniques should be used in these patients where possible.

This case demonstrates the feasibility of treating patients with muscular dystrophy and severe heart failure with an intracorporeal ventricular assist device. In certain cases, this may be a superior alternative to transplantation. Other populations of children may also benefit from insertion of an implantable assist device, particularly where the underlying non-cardiac pathology or social and family situations make survival following transplantation uncertain. Early referral of such patients for evaluation for mechanical circulatory support is critical.