Heart 'growth stagnation' during the year following menarche

During puberty, most body structures show an acceleration followed by deceleration in growth, while some grow at a constant rate. This study analyses heart growth dynamics during puberty. The focus was directed towards detection of 'unexpected' events in pubertal physiological growth, such as an episode of a heart growth stagnation or even a temporary reduction in size. A longitudinal study was performed in 173 healthy children (81 girls and 92 boys), aged 11.5 years at the beginning and 14.5 years at the end of the study. Changes in echocardiographic (parasternal M-mode) cardiac dimensions and in anthropometric and ergometric size of related body structures and functions were recorded annually. Direction (positive, zero or negative) and sizes of yearly increments were determined from the measurements, and three annual growth rates were compared for each variable by paired sample t-test. All observed variables increased following the usual growth velocity curve in boys. In girls, body height and weight, lean body mass, aortal root and left atrium, as well as diastolic blood pressure changed in the expected way during puberty, but cardiac left ventricle and endurance time did not. At the age of 13, thickness of the left ventricular walls and length of endurance time did not increase; later the growth of these variables resumed. Menarche onset (12.6 years) immediately precedes these events. Possible mechanisms are: temporary reduction of myocardial cells growth and division, and physiological heart "remodelling' due to changed growth pattern favouring longitudinal instead of transverse myofibrils growth, increased myocardial diastolic compliance and oscillatory blood volume increase.