Inspiratory Muscle Training Is Associated With Improved Inspiratory Muscle Strength, Resting Cardiac Output, and the Ventilatory Efficiency of Exercise in Patients With a Fontan Circulation

Abstract

BackgroundPatients with a Fontan circulation have reduced exercise capacity and respiratory muscle strength. Inspiratory muscle training (IMT) improves exercise capacity and quality of life in adults with heart failure. We assessed whether 6 weeks of a home‐based program of IMT improves inspiratory muscle strength and the ventilatory efficiency of exercise in adolescent patients with a Fontan circulation.Methods and ResultsTwenty‐three adolescent participants (aged 16±2 years) with a Fontan circulation underwent 6 weeks of IMT for 30 minutes daily. Respiratory muscle strength (maximal inspiratory pressure and expiratory pressure), lung function, and exercise capacity (cardiopulmonary exercise testing) were assessed. Fourteen of 23 participants also underwent exercise cardiac magnetic resonance imaging to examine the effects of IMT on cardiac output and systemic and pulmonary blood flow. Six weeks of IMT improved maximal inspiratory pressure by 36±24 cm H2O (61±46%) with no change in maximal expiratory pressure. Ventilatory efficiency of exercise improved after 6 weeks of IMT (from 34.2±7.8 to 32.2±5.6, P=0.04). In those who underwent exercise cardiac magnetic resonance imaging, IMT increased resting cardiac output (from 4.2±1.2 to 4.5±1.0 L/min, P=0.03) and ejection fraction (from 50.1±4.3 to 52.8±6.1%, P=0.03).ConclusionsSix weeks of IMT is associated with improved inspiratory muscle strength, ventilatory efficiency of exercise, and resting cardiac output in young Fontan patients. IMT may be a simple beneficial addition to the current management of Fontan patients, potentially reducing exercise intolerance and long‐term morbidity and mortality.

A restrictive ventilatory pattern is common in patients with univentricular heart after Fontan palliation and associated with a reduced exercise capacity and quality of life

“…confirmed by Laohachai et al,11 who explored the consequences of a 6-week inspiratory muscle training (IMT) in Fontan patients. Even after such a short training period, an improved ventilatory efficiency (defined as VE/VCO 2 ) and cardiac function could be described.Wu et al 13 obtained similar results in a small cohort of Fontan patients after a 12-week program of IMT, showing an improvement in peakVO 2 and ventilatory efficiency.Not only the preserved "thoracic pump" plays a key role in maintaining an adequate systemic venous return in Fontan circulation 13.…”

“…4 However, this palliation has intrinsic limitations 5 and the circumvention and management of long-term complications is still a major topic in the care of these patients. 10 Weakness in skeletal muscles is common in Fontan patients 11 and the presence of an impaired ventilation 12 with restrictive spirometry and reduced lung volumes was reported. 7,8 In UVH, the single ventricle is the systemic ventricle and the passive pulmonary blood flow 9 is substantially enhanced by the ventilatory movements and by the skeletal muscular pump of the veins.…”

Providing a framework of principles for conceptualising the Fontan circulation

“…The patient can increase his circulatory output by using peripheral muscles to pump blood into his caval veins to increase systemic venous pressure to drive blood through the critical bottleneck; respiratory pattern and force may also be helpful. 15,16 The clinician may improve output by lowering pulmonary vascular resistance but with limited result as many pulmonary lesions such as hypoplasia, stenosis, exclusion and others are not amenable to dilation; a great desire exists for improving the "suction of the ventricle", but no lusitropic drugs nor efficient manoeuvres to lower VEDP are available. 4,7,8 Increasing lower extremity muscle mass may impact active systemic venous return; however, this is a…”

Resting respiratory lung volumes are “healthier” than exercise respiratory volumes in different types of palliated or corrected congenital heart disease

“…Among all types of CHD, a special consideration must be addressed to functional univentricular heart palliated to total cavopulmonary connection (TCPC) in which an adequate ventilatory performance is crucial for the balance of pulmonary circulation 5 : without a pulsatile propelling subpulmonary ventricle, the systemic venous return usually occurring during inspiration due to the negative intrathoracic pressure can be increased by the training of the inspiratory muscles 6,7 …”

“…3 It is known, indeed, that pulmonary blood flow modulates the development of pulmonary parenchyma, vessels, and vascular bed size 4 Among all types of CHD, a special consideration must be addressed to functional univentricular heart palliated to total cavopulmonary connection (TCPC) in which an adequate ventilatory performance is crucial for the balance of pulmonary circulation 5 : without a pulsatile propelling subpulmonary ventricle, the systemic venous return usually occurring during inspiration due to the negative intrathoracic pressure can be increased by the training of the inspiratory muscles. 6,7 Nowadays, there is growing interest toward quality of life (QoL) of patients with repaired CHD and data support the notion that respiratory function disturbances, physical deconditioning, and hemodynamic alterations may all be associated with abnormal functional capacity and symptoms-limited ability to perform dailylife activities. Exercise capacity is an important determinant of survival 8,9 and it is routinely evaluated in the follow-up of patients with CHD.…”