Obesity is a risk factor for cardiovascular morbi-mortality that has deleterious effects on cardiovascular function: obesity causes blood volume, cardiac output and workload to increase while lowering the level of total peripheral resistance (1, 2). With increased filling pressure and volume, patients often develop 1) left ventricular dilation (1,3) and eccentric left ventricular hypertrophy independently from arterial pressure and age (4,5 ) as well as left atrial enlargement, from increased circulating blood volume and abnormal left ventricular filling (1) as well as 2) complex ventricular arrhythmias (6) which cause adverse effects on diastolic and systolic function (2, 19, 20-22). Together, these changes constitute “obesity cardiomyopathy”.
Presence of obesity cardiomyopathy, is strongly associated with several cardiovascular risk factors however the exact cardiac alterations related to obesity have thus far been based on statistical adjustments. Precise determination of the role of obesity on cardiac alterations has been a matter of controversy.
Indeed, left ventricular myocardial segments change in shape during systole and diastole, but deformation impairments may be "invisible" when using traditional imaging methods. 3D-Wall motion tracking echocardiography (3D-WMT), which analyses myocardial motion, provides information regarding left ventricular myocardial deformation able to detect subtle myocardial deformation impairments.
Several studies have demonstrated a definite association between left ventricular mass and obesity in children, independently from blood pressure levels (7). In the Strong Heart Study, significant impairment in left ventricular mass, wall mechanics and diastolic function were also found in adolescents (8).
Others have analysed diastolic function in obese children and adolescents, finding altered transmitral and pulmonary venous velocities, suggesting a reduction in early diastolic filling. Additionally, they observed early diastolic function impairment related to body mass index (9-11).
A recent study (12) enrolled thirty consecutive non-selected obese children, free from other cardiovascular risk factors and forty-two healthy children. Results showed that asymptomatic obesity is associated with myocardial deformation changes and that this association is independent from any other occurring cardiovascular risk factor. Furthermore, a decrease in systolic longitudinal and circumferential deformation, accompanied by an increase in systolic radial deformation in order to maintain the global contractility of the left ventricle was present in the asymptomatic obesity group.
To summarise, obesity cardiomyopathy is associated with 1) changes in the structure of the heart and 2) left ventricular myocardial deformation changes. Furthermore, this association occurs as early as childhood and is independent from any other cardiovascular risk factor. This knowledge should lead us to develop new recommendations to avoid obesity, especially during childhood.
Figure 1: 3D-Wall Motion Tracking Echocardiographic analysis. Left panel: left ventricular circumferential strain analysis of a normal (non-obese) child is shown. Right panel: left ventricular circumferential strain analysis of an obese) child is shown. There is a marked difference in mean left ventricular circumferential strain value between the two panels.
Knowing the disorders that can cause obesity involving the heart, and early prevention - as early as childhood, are key. Appropriate dietary measures and regular exercise will help with early treatment. Drug therapy and surgical treatment may be reserved for difficult-to-treat cases.