TBL11 - Cardiac Cycle

Question 1

What is the heart? What do the atria and ventricles do?

Answer 1

The heart is a two-sided chamber with the atria drawing blood from the circulation and the ventricles pumping it back into the circulation

Question 2

How do the heart chambers act in relation to one another?

Answer 2

Although adjacent to each other, the chambers act in series, dividing the circulation into the pulmonary and systemic circuits

Question 3

What does the cardiac cycle describe? What is the normal heart rate (pulse) in an adult?

Answer 3

1) The cardiac cycle describes a single heartbeat, which is based on systole (contraction) and diastole (relaxation) of the ventricles
2) In adults, normal heart (pulse) rates range from 60-100 beats/minute

Question 4

What is diastole characterized by in relation to valve closing and opening? What occurs at the end of diastole?

Answer 4

1) Diastole begins after closure of the aortic and pulmonary artery valves and opening of the mitral and tricuspid valves; thus, the superior vena cava (SVC), inferior vena cava (IVC), and pulmonary veins can refill the atria and begin ventricular refilling without retrograde (reverse) flow into the ventricles from the aorta or pulmonary arteries
2) At the conclusion of diastole, atrial compression (mild contraction relative to the ventricles) completes ventricular refilling

Question 5

What is characteristic of the beginning of systole? What causes the return of venous blood into the atria during systole?

Answer 5

1) Systole begins with closure of the mitral and tricuspid valves; thus, ventricular contraction thrusts open the aortic and pulmonary valves and propels blood into the aorta and pulmonary arteries without retrograde flow into the atria
2) During systole, increased vascular pressure initiates the return of venous blood into the atria

Question 6

What are normal systolic/diastolic pressure in the systemic and pulmonary arteries? What is normal oxygen saturation of blood in the atria, ventricles, pulmonary arteries, and aorta?

Answer 6

1) Normal systolic/diastolic pressures in the systemic and pulmonary arteries are 120/80 and 20/8 mmHg, respectively
2) Normal oxygen saturation of blood in the right atrium, right ventricle, and pulmonary arteries is about 75%, while saturation in the left atrium, left ventricle, and aorta is about 95%

Question 7

What surrounds the aortic, pulmonary trunk, and atrioventricular orifices? How does this help with the cardiac cycle? What three valves consist of three cusps? Which one only consists of two?

Answer 7

1) Rings of dense connective tissue surround the atrioventricular orifices (openings) and the orifices of the aorta and pulmonary trunk thereby reinforcing the valves and insuring their proper opening and closure during the cardiac cycle
2) The aortic, pulmonary, and tricuspid valves consist of three cusps and the mitral valve consists of two cusps

Question 8

What creates heart sound S1? What creates heart sound S2? What part of the cardiac cycle includes silence?

Answer 8

1) Closure of the mitral and tricuspid valves during systole creates heart sound S1
2) Closure of the aortic and pulmonary valves during diastole creates heart sound S2
3) Normal forward blood flow through the open valves is silent

Question 9

Where are auscultation sites for the aortic and pulmonary valves? Where are auscultation sites for the tricuspid and mitral valves?

Answer 9

1) Auscultation sites for the aortic and pulmonary valves lie on the parasternal lines in the right and left 2nd ICS
2) Auscultation sites for the tricuspid and mitral valves lie on the parasternal and midclavicular lines in the left 4th and 5th ICS

Question 10

What does valvular stenosis result in? What does valvular insufficiency result in? What are the most common valvular abnormalities?

Answer 10

1) Valvular stenosis (narrowing) slows forward blood flow out of a chamber
2) Valvular insufficiency allows reverse blood flow into a chamber
3) Aortic valve stenosis and mitral valve prolapse (insufficiency) are the most common valvular abnormalities

Question 11

What do stenotic and prolapsed valves result in? What are murmurs classified by? What are the classifications? What are other ways of creating heart murmurs?

Answer 11

1) Stenotic and prolapsed valves create turbulent blood flow that causes cardiac murmurs (i.e., abnormal sounds created during forward and reverse blood flow)
2) Murmurs are classified by their temporal relation to the cardiac cycle
3) Thus there are systolic, diastolic, and continuous murmurs
4) Abnormal cardiac chambers, septal defects between chambers, and anomalies of the great vessels also create heart murmurs

Question 12

Why are auscultation sites situated superficial to the chamber or vessel into which blood has passed rather than directly above the valves?

Answer 12

Blood tends to carry the sound in the direction of its flow; consequently, each area is situated superficial to the chamber or vessel into which the blood has passed and in a direct line with the valve orifice

Question 13

How is the murmur from a prolapsed mitral valve classified? Which heart chamber is affected? Why can pulmonary edema result?

Answer 13

1) A prolapsed mitral valve is an insufficient or incompetent valve with one or both leaflets enlarged, redundant or “floppy,” and extending back into the left atrium during systole (systolic)
2) As a result, blood regurgitates into the left atrium when the left ventricle contracts, producing a characteristic heart sound or murmur (left atrium affected)
3) When there is a backflow of blood flow from the left ventricle –> left atrium –> pulmonary veins –> capillaries –> interstitial tissue due to high pressures causes pulmonary edema

Question 14

Why does left ventricular hypertrophy with associated dyspnea result from aortic valve stenosis? How is the resulting murmur classified?

Answer 14

1) The great majority of aortic stenoses is a result of degenerative calcification and comes to clinical attention in the 6th decade of life or later. Aortic stenosis causes extra work for the heart, resulting in left ventricular hypertrophy
2) Systolic murmur occurs because during systole due to turbulence

Question 15

Which cardiac chamber is affected by pulmonary valve stenosis and pulmonary valve insufficiency? How are the respective murmurs classified and where could edema occur?

Answer 15

1) Both types of pulmonary stenoses (pulmonary valve stenosis & infundibular pulmonary stenosis) produce a restriction of right ventricular outflow and may occur together. The degree of hypertrophy of the right ventricle is variable
2) Systolic murmur occurs because during systole due to turbulence in pulmonary stenosis
3) Diastolic murmur occurs in pulmonary insufficiency
4) Systemic edema could occur

Question 16

How is the murmur from aortic valve insufficiency classified and what is the resulting collapsing pulse?

Answer 16

1) Insufficiency of the aortic valve results in aortic regurgitation (backrush of blood into the left ventricle), producing a heart murmur and a collapsing pulse (forcible impulse that rapidly diminishes)
2) It is a diastolic murmur