Transcatheter aortic valve implantation for severe aortic stenosis in a patient with mucopolysaccharidosis type II (Hunter syndrome) accompanied by severe airway obstruction

Abstract

Mucopolysaccharidosis type II, known as Hunter syndrome, is a rare inherited metabolic disorder with glycosaminoglycan accumulation leading to progressive multisystem involvement, such as heart, respiratory, and central nervous systems. In particular, concurrence of major heart and respiratory problems in this syndrome often causes difficulty in performing curative and invasive treatments. Transcatheter aortic valve implantation (TAVI) has been an established therapy for severe aortic stenosis (AS). In patients who cannot undergo surgical aortic valve replacement because of high risk for general anesthesia, TAVI with local anesthesia has become an alternative therapy for severe AS. We report herein a case of 50-year-old man with Hunter syndrome accompanied by severe airway obstruction who underwent TAVI with local anesthesia for severe AS.

<Learning objective: Mucopolysaccharidosis is characterized by glycosaminoglycan accumulation leading to progressive multisystem involvement. Heart disease and respiratory problems are often concomitant in patients with mucopolysaccharidosis. When surgical treatment is required, consideration about treatment strategy and perioperative management are important because of its high surgical risk or inoperable status. We describe a case with mucopolysaccharidosis accompanied by severe airway obstruction who underwent transcatheter aortic valve implantation with local anesthesia for severe aortic stenosis.>

Introduction

Mucopolysaccharidosis type II, known as Hunter syndrome, is a rare inherited metabolic disorder with glycosaminoglycan accumulation leading to progressive multisystem involvement [1]. This syndrome especially causes heart disease (e.g. valvular heart disease, cardiomyopathy, heart failure, and arrythmia) as well as respiratory problems (e.g. airway obstruction, sleep apnea, and respiratory infection), which have the potential to be life-threatening [2]. When there are simultaneously major problems in such vital organs, comprehensive treatment strategy, minimally invasive surgery, and careful perioperative management, are usually required because of high surgical risk or inoperable status. Transcatheter aortic valve implantation (TAVI) is a less invasive procedure to treat severe aortic stenosis (AS) in patients at increased risk for surgical aortic valve replacement [3,4], and TAVI with local anesthesia is useful particularly in patients with respiratory disorders [5]. We report herein a case of 50-year-old man with Hunter syndrome accompanied by severe airway obstruction who underwent TAVI with local anesthesia for severe AS.

Case report

A 50-year-old man with Hunter syndrome was referred to our institution for treatment of congestive heart failure caused by severe AS. He was diagnosed with Hunter syndrome based on the decreased leukocyte iduronate 2-sulftase activity (below 1.3 nmol/mg protein/4 hour) 16 years previously [6]. Leukocyte arylsulfatase A was 171.9 nmol mg protein/hour, and genetic testing was not done. Four years previously, he was transferred to another hospital with cardiopulmonary arrest due to ventricular fibrillation. After successful resuscitation and intensive treatment, he was fully recovered, and an implantable cardioverter defibrillator was inserted into the left anterior chest wall. At that time, transthoracic echocardiography (TTE) showed moderate AS. While he was followed up as an outpatient, he usually worked and the activities of daily living was good until the most recent hospitalization. He was admitted to another hospital due to congestive heart failure two weeks before transfer to our institution. TTE showed severe AS, and diuretic therapy was started. Since the control of heart failure was difficult because of a drop in blood pressure after the administration of intravenous diuretics, the intervention in severe AS was needed for the control of heart failure.

TTE after admission showed severe AS with global hypertrophy of left ventricle and mildly reduced left ventricular ejection fraction of 47% (Fig. 1A to C). Computed tomography demonstrated severe tracheal stenosis 20 mm below the glottis with a minimum diameter of 3 mm due to accumulation of glycosaminoglycan (Fig. 2A and B). Since endotracheal intubation and mechanical ventilation seemed to be impossible, TAVI under local anesthesia with conscious sedation was planned after multidisciplinary heart team discussion. The patient had good transfemoral (TF) access, moderate calcification in the noncoronary cusp (Fig. 2C), and aortic annulus area and circumference of 478.71 mm² and 79.08 mm (Fig. 2D), as assessed by computed tomography. Therefore, we decided to perform TF-TAVI using a 29-mm Evolut PRO (Medtronic, Minneapolis, MN, USA) valve.

Fig. 1.

(A) Transthoracic echocardiography (TTE) image obtained from parasternal long-axis view in diastolic frame showing mild global left ventricular hypertrophy and calcified aortic valve (arrow). (B) TTE image obtained from parasternal short-axis view in systolic frame showing calcified aortic valve with severe stenosis (arrows). (C) Continuous wave Doppler measurement by TTE showing severe aortic stenosis with peak velocity of 4.5 m/s.

Fig. 2.

(A) Computed tomography (CT) sagittal view showing severe stenosis in the lower respiratory tract (arrows). (B) Multi-slice three-dimensional CT reconstruction of airway showing severe tracheal stenosis (arrow). (C) Multi-slice CT showing moderate calcification in the noncoronary cusp. (D) Multi-slice CT showing measurement of aortic annulus dimensions.

At the TAVI procedure, the administration of dexmedetomidine hydrochloride to induce conscious sedation resulted in the development of stridor and worsening of airway obstruction. As a result, the patient was kept awake without any sedation, and his ventilation was assisted by high flow nasal canula oxygen. A 5 Fr sheath and a guide wire were respectively inserted into the right internal jugular vein and right common femoral vein, preparing for immediate initiation of venovenous extracorporeal membrane oxygenation in case of failure to maintain his spontaneous ventilation. A 20 Fr Dryseal sheath (W.L. Gore and Associates, Flagstaff, AZ, USA) was inserted into the right common femoral artery, and a 29-mm Evolut PRO valve was directly implanted under control pacing (Fig. 3A and B). TTE showed good expansion of the valve and trivial paravalvular leakage, requiring no post-dilatation. Post-procedural clinical course was favorable, and the patient was discharged from our institution. Tracheal stenosis was followed by conservative management because he could not tolerate the risk of complications related to the surgical treatment.

Fig. 3.

(A) Transcatheter aortic valve implantation under control pacing with implanted cardioverter defibrillator. (B) Aortography after implantation of transcatheter aortic valve showing good positioning of device and trivial paravalvular leakage.

Discussion

Hunter syndrome is a rare, X-linked multisystem disorder characterized by accumulation of glycosaminoglycan on various organ systems due to the deficiency of lysosomal enzyme iduronate 2-sulftase [1]. Cardiac involvement is often a major cause of morbidity and mortality. There are two types according to the severity of disease in Hunter syndrome: severe form and less severe form. Patients with severe form typically die in the second decade of life, whereas patients with less severe form survive until the fifth or sixth decade of life [7]. It is reported that cardiovascular involvement was seen 82% of patients in Hunter syndrome. The prevalence of valvular heart disease was 57% and median age at onset of valvular disease was reported to be 6.1 years old [2]. Progressive thickening and stiffening of the valve leaflets commonly in mitral and aortic valves lead to valvular stenosis and regurgitation [8]. Therefore, surgical intervention for cardiac disease is occasionally needed. However, airway obstruction caused by large tongue/tonsils/adenoids and soft tissue enlargement in laryngopharynx and trachea, in addition to skeletal problems such as short neck and spinal deformities, often makes perioperative airway management difficult [9]. In our case, severe tracheal stenosis by accumulation of glycosaminoglycan, as well as large tongue and hypertrophy of laryngopharynx, was considered to disable not only endotracheal intubation but use of sedative agents.

TAVI has become an established therapy for severe AS in patients with high surgical risk, and the safety and efficacy were recently demonstrated even in intermediate and low surgical risk patients [3,4]. In recent studies, TAVI with local anesthesia and conscious sedation was associated with fewer post-procedural complications and lower early mortality compared with TAVI with general anesthesia [5]. In our case, TAVI under local anesthesia with conscious sedation was planned after multidisciplinary heart team discussion. Since conscious sedation with dexmedetomidine hydrochloride resulted in the development of stridor and worsening of airway obstruction, we discontinued any sedation and accomplished the procedure without major complications.

To the best of our knowledge, this is the first report demonstrating successful TAVI for severe AS in a patient with Hunter syndrome accompanied by severe airway obstruction. A successful outcome may be achieved by utilizing TAVI while keeping awake with careful respiratory monitoring for inoperable AS patients with severe airway obstruction.