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.
FloWireÂ® Doppler Guide Wire image, courtesy Volcano Corporation. What is FFR? Fractional Flow Reserve, or FFR, is a guide wire-based procedure that can accurately measure blood pressure and flow through a specific part of the coronary artery. FFR is done through a standard diagnostic catheter at the time of a coronary angiogram (a.k.a. cardiac catheterization). The measurement of Fractional Flow Reserve has been shown useful in assessing whether or not to perform angioplasty or stenting on intermediate blockages. 1  The point of opening up narrowings or blockages in the coronary arteries is to increase blood flow to the heart.