Study design and population
The study is a retrospective analysis of echocardiographic findings in healthy normal controls that formed part of a study (M170389) conducted at Chris Hani Baragwanath Academic Hospital (CHBAH). The inclusion criteria for the prior study included: (i) absence of cardiovascular symptoms, (ii) normal blood pressure (≤140/90 mmHg), (iii) absence of diabetes and cardiovascular disease, (iv) not on any chronic medication, and (vi) presence of sinus rhythm (heart rate between 50 and 85 b.p.m). The exclusion criteria were pre-existing: (i) cardiovascular diseases, (ii) pulmonary diseases, (iii) previous abnormal echocardiography, (iv) congenital heart diseases, (v) cardiac pathology detected by echocardiography, (vi) sinus tachycardia (vii) inadequate echocardiographic image quality, and (viii) athlete.