Ganong's Review of Medical Physiology, 23rd Edition

CHAPTER 31

The Heart as a Pump 511

FIGURE 31–3
Events of the cardiac cycle at a heart rate of 75 beats/min.
The phases of the cardiac cycle identified by the numbers at
the bottom are as follows: 1, atrial systole; 2, isovolumetric ventricular contraction; 3, ventricular ejection; 4, isovolumetric ventricular relaxation;
5, ventricular filling. Note that late in systole, aortic pressure actually exceeds left ventricular pressure. However, the momentum of the blood keeps
it flowing out of the ventricle for a short period. The pressure relationships in the right ventricle and pulmonary artery are similar. Atr. syst., atrial
systole; Ventric. syst., ventricular systole.

Time (s)

Electrocardiogram

Heart sounds

(phonocardiogram)

Aortic pressure

(at o, the aortic valve opens;

at c, it closes)

Left ventricular pressure ( )

Left atrial pressure ( )

(right is similar)

Left ventricular volume

(at c’, the mitral valve closes;

at o’, it opens)

Jugular venous pressure,

showing a, c, and v waves

Carotid pressure

(n = dicrotic notch)

Radial pressure

Plumonary arterial pressure

Right ventricular pressure

0

Atr.

syst.

Ventric.

syst. Diastole

0.2

P

Q

41

o

c'

o'

a

12 3 4 5

c v

n

c

23

S

R T

U

0.4 0.6 0.8

120

Pressure

(mm Hg)

Ventricular

volume (mL)

Aortic

blood flow

(L/min)

Pressure

(mm Hg)

130

65

25

15

0

30

15

0

0

80

40

0

Phases of cardiac cycle