Natural selection, which includes sexual selection, is the fact that some traits make it more likely for an organism to survive and reproduce. Population genetics describes natural selection by defining fitness as a propensity or probability of survival and reproduction in a particular environment. The fitness is normally given by the symbol w=1-s where s is the selection coefficient.
Atrial fibrillation with RVR (Rapid Ventricular Response) is a heart condition caused by irregular electrical activity that results in irregular contractions of the heart walls and its chambers. The heart (atrium), shakes with a rapid tremulous movement or makes fine irregular twitching movements, generally referred to as fibrillating.
Pulse volume recording (PVR) is a non-invasive imaging test that evaluates the lower or upper extremity blood flow. They are actually the more complete form of ankle brachial index, because they test more areas of the limb and not just the flow at the end. Pulse volume recording is a functional test. This means that it does not examine specific blood vessels, but rather assesses the sum of all blood flow to the examined limb.