Opteonâ¢ YF (HFO-1234yf) is a low global warming potential (GWP) refrigerant for use in automotive air-conditioning systems. Opteonâ¢ YF (HFO-1234yf) has a chemical structure of CF3CF= CH2 2,3,3,3-tetrafluoropropene.
During isovolumetric relaxation, which is the second last phase of the cardiac cycle, all the heart valves are closed. This means that there is no blood passing between the cardiac chambers or out of the heart. The pressure drop below 120 mmHg as the ventricles relax causes the semilunar valves to close. As the pressure drops further, the atrial pressure exceeds that of the ventricles and the atrioventricular valves open. Meanwhile, blood is being pumped around the body.
When the heart beats, the atria (atrial systole) and ventricles (ventricular systole) contract and the open bicuspid and tricuspid valves are pushed closed due to blood pressure in the chambers. The relaxed chordae tendineae tense up to hold the cusps of the atrioventricular valves in place when they close. This prevents prolapsing of the valve leaflets and blood from regurgitating (flowing backwards) into the upper atrial chambers (the left atrium and right atrium).