Info

Heart Sounds

FIGURE 3 Phases of the cardiac cycle are correlated with pressure, auditory, volume, and electrical events in and around the heart. The seven phases of the cardiac cycle are as follows: (A) atrial systole, (B) isovolumetric ventricular contraction, (C) rapid ventricular ejection, (D) reduced ventricular ejection, (E) isovolumetric ventricular relaxation, (F) rapid ventricular filling, and (G) reduced ventricular filling.

FIGURE 3 Phases of the cardiac cycle are correlated with pressure, auditory, volume, and electrical events in and around the heart. The seven phases of the cardiac cycle are as follows: (A) atrial systole, (B) isovolumetric ventricular contraction, (C) rapid ventricular ejection, (D) reduced ventricular ejection, (E) isovolumetric ventricular relaxation, (F) rapid ventricular filling, and (G) reduced ventricular filling.

During rapid ejection the velocity at which blood is being ejected is increasing, causing ventricular pressure to slightly lead that in the aorta by a few mm Hg. As the rate of ejection slows during the reduced ejection period, the inertia of the decelerating column of blood traveling down the aorta reverses the gradient causing aortic pressure to slightly lead ventricular pressure.

As the ventricle begins to relax, pressure in the ventricle falls. As blood begins to flow backward across the aortic valve, it closes its leaflets. That momentary retrograde flow of blood at the aortic valve and its abrupt deceleration as the valve snaps closed cause a small rebound in the aortic pressure trace called the dicrotic notch. The volume of blood left in the ventricle at aortic valve closure is termed the end-systolic volume. During the isovolumetric period of relaxation, E, left ventricular and aortic pressure separate and ventricular pressure continues to fall. The isovolumetric relaxation period ends when ventricular pressure reaches left atrial pressure and the mitral valve opens. Although the mitral valve is closed during systole, blood continues to return to the left atrium, causing its pressure to steadily rise, generating the V wave in the atrial pressure tracing. This elevated pressure causes blood to surge into the ventricle as soon as the mitral valve opens. For that reason, period F is called the rapid filling phase. The abrupt fall in atrial pressure during the rapid filling phase gives rise to the Y wave. During the remainder of diastole, the reduced ventricular filling period, the pressure within the ventricle has equilibrated with atrial pressure, and little additional blood enters the ventricle. As atrial blood fills the ventricle, atrial pressure rises once more as the H wave.

The pressure in the aorta is the arterial blood pressure. The peak pressure during ejection is referred to as the systolic pressure, whereas the lowest pressure just prior to aortic valve opening is called the diastolic pressure. Blood pressure is usually reported as systolic/ diastolic, so for the example in Fig. 3 the patient's blood pressure would be 120/80 mm Hg.

The diagram in Fig. 3 is for the left heart and the aorta. The pressure relationships within the right heart and pulmonary artery are virtually identical to those shown in Fig. 3, with the exception that the pressures are only about one-fifth as great. The student should meticulously study this diagram until the mechanisms underlying these correlations are conceptually obvious.

Relaxation Audio Sounds Relaxation

Relaxation Audio Sounds Relaxation

This is an audio all about guiding you to relaxation. This is a Relaxation Audio Sounds with sounds called Relaxation.

Get My Free MP3 Audio


Post a comment