Table 1.

Glossary of key definitions relating to heritability and cardiovascular measures

Heritability definitions
ACE model	This model assumes that the source of phenotype variance can be attributed to genetic influences (A), shared environmental factors (C), and unique environmental factors (E). Environmental factors are all those that are not inherited irrespective of whether they are explicitly measured.
CE model	Assumes that the source of phenotype variance can be attributed to shared environmental factors (C) and unique environmental factors (E)
Heritability	Proportion of population variance of a phenotype attributed to genetic factors at a particular time point.
Cardiovascular definitions
Augmentation pressure	Augmentation pressure (AP) is the difference between central systolic blood pressure and P1 (see Figure 1).
Cardiac output	Volume of blood ejected by the left ventricle per minute.
Pressure at P1	Pressure at the first systolic shoulder of the central pressure waveform. P1 represents the pressure at the first systolic shoulder or peak and corresponds to the time of peak myocardial wall stress (see Figure 1).
Pulse pressure	Pulse pressure is the pressure difference between systolic and diastolic pressure.
Pulse wave velocity	Pulse wave velocity is the velocity at which the pressure pulse propagates along the arterial tree and is regarded as the gold-standard measure of arterial stiffness.
Stiffness index	An index of arterial stiffness derived from the finger photoplethysmography that both theoretically and empirically relates to PWV.
Systemic vascular resistance	Resistance to blood flow offered by the systemic vasculature.