Читать книгу Manual of Equine Anesthesia and Analgesia - Группа авторов - Страница 86

 Ventricular pressure continues to fall with no change in ventricular volume (isovolumetric relaxation).

 This proceeds until the ventricular pressure drops below atrial pressure, when the AV valves open and the phase of rapid ventricular filling begins.Ventricular pressure rises slowly but ventricular volume increases rapidly as blood that accumulated in the atria during ventricular systole flows rapidly into the ventricle.Rapid filling may be associated with a functional protodiastolic murmur and the termination of rapid filling results in the low‐frequency third heart sound (S3).The rapid decline in both atrial volume and pressure results in the “y” descent on the atrial pressure curve and may be visualized as a collapse of the jugular vein.

 The period of rapid ventricular filling is followed by a period of low velocity filling (diastasis) which extends until the next atrial systole.In the resting horse with a normal HR, diastasis is the longest period of diastole.During diastasis, jugular vein filling may occur, especially during periods of bradycardia.

 SA node firing followed by atrial contraction occur during the last phase of ventricular diastole and start the cardiac cycle again.