Impact of loss of ambulation on right ventricular size in patients with neuromuscular disorders

Abstract

Neuromuscular disorders (NMD) are a group of hereditary and acquired neurological diseases with skeletal disability. Patients may be wheelchair bound, depending of clinical severity and mechanical ventilation support is needed in patients with significant respiratory insufficiency. Right ventricular (RV) dimensions may be affected by intrathoracic pressures and venous return, this last one depending on peripheral skeletal function. We aimed to assess the impact of loss of ambulation on right ventricular size in patients with neuromuscular disorders, using the RV end diastolic area (RVEDA). We reviewed from our database patients with neuromuscular disorders who underwent transthoracic echocardiography. We systematically assessed right ventricular size, skeletal muscle function and pulmonary function. We included 320 patients (female gender: 32%) with neuromuscular disorders (including 40% myotonic dystrophy type I, 20% Duchenne muscular dystrophy, 10% Becker muscular dystrophy). Median age was 37 years [28–48], median body mass index (BMI) at 22.6 kg/m2 [19.4–26], median forced pulmonary vital capacity (FVC) at 75% of predicted value [45–96.5], 28% of patients were wheelchair bound and 35% of patients were on nocturnal noninvasive ventilation (NIV). Median left ventricular ejection fraction (LVEF) was 60% [55–66], median RVEDA was 17 cm2 [13–20] and median right ventricular peak systolic tissue Doppler velocity (Sm RV) was 13 cm/s [11–15]. The RVEDA was reduced in patients with beta-blocker (BB) use (14 cm2 vs. 17 cm2, P < 0.001), ACE inhibitor use (14 cm2 vs. 17.8 cm2, P < 0.001), NIV use (14 cm2 vs. 18 cm2, P < 0.001), wheelchair use (12.5cm2 vs. 18.6 cm2, P < 0.001). The RVEDA was associated with age (r = 0.1, p 0.04), BMI (r = 0.27, P < 0.001), Walton score (r = −0.53, P < 0.001), FVC (r = 0.5, P < 0.001), minimal vena cava diameter (r = −0.3, P < 0.001), left atrial diameter (r = 0.3, P < 0.001), right ventricular end diastolic volume (r = 0.97, P < 0.001), left ventricular end diastolic volume (r = 0.37, P < 0.001) and systolic arterial pulmonary pressure (r = 0.15, P 0.025). Using multivariate analysis, at the risk of 5%, by adjusting for age, BB, ACE inhibitor, LVEF, NIV and history of pacemaker, wheelchair use remained significantly associated with RVEDA (P < 0.001). In patients with NMD, the loss of ambulation is associated with a reduction of the right ventricular size, irrespective of age, betablockers, ACE inhibitor, LVEF and ventilation