Annual deaths from tornadoes, earthquakes and floods together total fewer than 200. The most deadly heat wave in recent years occurred in Chicago over a week in July 1995, when temperatures hovered around 100 degrees.
Cardiac Cycle: 1st Systole Phase. During the systole phase, the right ventricle receives impulses from the Purkinje fibers and contracts. The atrioventricular valves close and the semilunar valves open. The de-oxygenated blood is pumped into the pulmonary artery.
Active filling from atrial systole contributes about 20% of the blood volume to the ventricles during diastole (in contrast with the 80% from rapid, passive filling in mid diastole). Normally, active filling is silent, but when blood impacts a stiff, non-compliant ventricle, the result is a fourth heart sound (S4) .