Ganong 24e chapter 30 - The Heart as a Pump (1) Flashcards
What percentage of ventricular filling is produced by passive filling in diastole? What makes up the remainder of ventricular filling?
70%. The remainder is made up by atrial contraction.
Name three events that occur at the start of ventricular systole. What is the name of this first phase of ventricular systole?
AV-valves close, 1st heart sound is heard, R-wave of the ECG. This is all part of isovolumetric contraction.
What are the pressure changes that mark the end of isovolumetric contraction?
The left ventricular pressure surpasses the aortic pressure (at the 80mmHg mark). This causes the aortic valve to open. Meanwhile, the RV pressure surpasses the pulmonary arterial pressure (at the 10mmHg mark), causing opening of the pulmonary valve.
What does this image represent? What is happening at d-a? At a-b? At b-c? At c-d?
This is the left ventricular pressure-volume loop. d-a is diastolic ventricular filling. a-b is isovolumetric contraction. b-c is systolic ventricular ejection. c-d is isovolumetric relaxation.
During the cardiac cycle, what is the peak pressure in the LV? How about in the RV?
LV peak: 120mmHg. RV peak: 25mmHg.
What is the normal stroke volume? What is the normal end-disastolic ventricular volume? What does this make the normal ejection fraction?
Normal stroke volume is about 80mL. End-diastolic ventricular volume is about 130mL. Normal ejection fraction is about 65%.
What are the pressure changes that mark the end of isovolumetric relaxation?
The ventricular pressure falls below the atrial pressure, and so the AV-valves open.
Which atrium contracts first?
The right atrium.
What is the maximum rate that a healthy AV-node can conduct impulses through to the ventricles?
230 impulses/min
What produces the dicrotic notch in the aortic pressure curve?
Closure of the aortic valve, at the end of systolic ventricular ejection.
Explain the a-wave, c-wave and v-wave in the CVP trace.
a-wave = atrial contraction. c-wave = the rise in atrial pressure caused by the bulging backwards of the tricuspid valve during ventricular contraction. v-wave = atrial filling during isovolumetric relaxation, against a closed tricuspid valve.
What is meant by the cardiac index? What is its average value in a healthy person?
This is the cardiac output per minute per square meter of body surface. The average is 3.2 L
Draw the graph that represents Starling’s law of the heart.
What shifts the Frank-Starling curve upward and to the left in the heart?
Sympathetic stimulation, inotropic agents, exercise, things that increase contractility.
In systolic failure, what is the major physiological impairment, and how does this affect the pressure-volume loop?
There is impaired contractility during systole. The pressure-volume loop of the LV is narrowed (reflecting a smaller stroke volume), and slightly shifted to the right.
In diastolic failure, what is the major physiological impairment, and how does this affect the pressure-volume loop?
There is impaired diastolic filling. The LV pressure-volume loop is narrowed (reflecting the smaller stroke volume), and shifted slightly to the left and up.
What is each numbered phase of the cardiac cycle, as per Ganong figure 30-3?
Phase 1: Atrial systole
Phase 2: Isovolumetric contraction
Phase 3: Ventricular ejection
Phase 4: Isovolumetric relaxation
Phase 5: Ventricular filling
What is the normal blood flow to the beating heart at rest?
84mL/100g/min, or 250mL/min
How much oxygen does a normal beating heart consume?
9mL/100g/min.
How much can the heart’s oxygen consumption increase during exercise?
100% (it can increase from 9mL/100g/min up to 18mL/100g/min)
What is a normal cardiac output at rest?
6.4L/min (assuming SV 80mL and HR 80)
How much can the cardiac output increase during intense exercise?
700% (can increase to 35L/min)
What happens to systolic BP during exercise? What happens to diastolic BP? And PVR?
Systolic BP rises and diastolic BP falls. There is an overall net fall in PVR.
