L12 Cardiac Function

Question 1

How do changes in preload affect stroke V?

Answer 1

Increased preload= increased stroke V

Question 2

How do changes in afterload affect stroke V?

Answer 2

Increased afterload= decreased stroke V

Question 3

How do changes in contractility affect stroke V?

Answer 3

Increased contractility= increased stroke V

Question 4

Define systolic heart failure.

Answer 4

Decreased ventricular contractility, heart fails to provide CO sufficient to meet body’s needs

Question 5

Define diastolic heart failure.

Answer 5

Decreased ventricular compliance, heart fails to provide CO sufficient to meet body’s needs

Question 6

How does systolic heart failure affect ventricular contractility?

Answer 6

Contractility is decreased

Question 7

How does systolic heart failure affect ventricular compliance?

Answer 7

There is no affect on compliance

Question 8

How does diastolic heart failure affect ventricular contractility?

Answer 8

There is no affect on contractility

Question 9

How does diastolic heart failure affect ventricular compliance?

Answer 9

Compliance is decreased

Question 10

Define ejection fraction.

Answer 10

Fraction of blood ejected during one stroke of the heart in relation to the total L ventricular end-diastolic V
EF= (EDV-ESV)/EDV= SV/EDV

Question 11

What factors affect preload?

Answer 11

• Pressure gradient btw. atria and ventricles (increased EDV= decreased ventricular filling)
• Time for ventricular filling (increase in HR= decrease in ventricular filling)
• Ventricular compliance (decrease in compliance= decrease in filling)
• Atrial fxn/kick (decrease of atrial fxn= decrease filling)

Question 12

What factors affect afterload?

Answer 12

• Aortic pressure (hypertension)
• Ventricular outflow tract resistance (valvular stenosis, subaortic stenosis)
• Ventricular size (dilated heart= higher wall tension= larger afterload)

Question 13

What factors affect contractility?

Answer 13

Sympathetic nerve activity
Drugs (positive inotropic agents, digitalis)
Disease (myocardium)

Question 14

How does increase in heart rate affect contractility?

Answer 14

Increased HR= increased contractility (force-freq. relationship)

Question 15

How does heart rate affect ventricular filling?

Answer 15

Increased HR= decreased ventricular filling

Question 16

What factors affect heart rate (ventricular rate)?

Answer 16

• Pacemaker fxn (NSR, SSS, increased/decreased PM fxn)
• AV node conduction (2nd or 3rd deg. heart block, A Fib/flutter)
• Ventricular arrhythmias