Altered body composition in adults with complex congenital heart disease

Abstract: IntroductionThanks to achievements in paediatric heart surgery and medicine, the population of adults with surgically repaired or palliated congenital heart defects is growing. Many of these adults have reduced exercise capacity, weaker muscular strength and shorter height, all of which suggest an altered body composition.The overall aim of this thesis was to evaluate the body composition, in terms of bone, muscle and fat mass, in adults with complex congenital heart disease (CHD). Changes as such may be of prognostic importance and thus suggest future therapeutic targets outside the traditional hunting grounds of the cardiologist.Material and methodsThe overall material consisted of two cohorts. The first cohort, recruited in a Swedish multicentre study, comprised 73 adult patients with complex CHD and 73 controls, matched for age and sex. Participants were examined with full body dual-energy x-ray absorptiometry (DXA), providing muscle, bone and fat mass for arms, legs and trunk respectively (papers I and II).The second cohort, recruited within a single centre study, comprised 49 adult patients with complex CHD and 49 age and sex matched controls. Participants were examined with peripheral quantitative computed tomography (pQCT), providing slices of forearm and calf, describing muscle, bone and fat area and corresponding density (papers III and IV). Muscular strength in selected muscle groups was also evaluated in both cohorts.ResultsMore than half of the adults with complex CHD had a pathologically low skeletal muscle mass and strength compared to controls, a trait referred to as sarcopenia. There was a strong association between forearm muscle mass and grip strength.Bone mass was lower in adults with complex CHD, according to both DXA and pQCT analyses, also when adjusting for shorter height. Patients also had lower full body bone mineral density (BMD) as measured with DXA. However, analysis of BMD in limbs with pQCT showed no such reduction. Despite this latter finding, the strength-strain index (a surrogate marker for bone strength provided by pQCT in the lower limbs) was still lower in patients compared to controls.Female patients had a higher amount of fat, both in terms of fat mass and proportion of fat, in comparison to controls. The fat mass was predominantly distributed around the internal organs, known as visceral adipose tissue. Male patients showed no such difference regarding fat mass compared to controls.ConclusionConsequences of living with complex CHD go far beyond the heart; this young population presents a reduced skeletal muscle mass as well as reduced bone strength – both premature traits of frailty, prone to increase with further ageing. Also, women with complex CHD have an increased amount of visceral adipose tissue, which may elevate the risk of acquired heart disease.The extent of future complications remains to be seen. However, the standard treatments for both sarcopenia and osteoporosis include optimal nutritional intake and increased physical exercise. These measures should start sooner rather than later, preferably evaluated through existing quality registers and interventional trials.