Pharmacological Control of Output

Question 1

What three things determine stroke volume?

Answer 1

• preload - left ventricular end diastolic pressure
• afterload - pressure in the wall of the left ventricle during ejection
• inotropy - contractility

Question 2

What determines contractility?

Answer 2

Ca²⁺

Question 3

What are inotopic drugs?

Answer 3

positive inotropic drugs = increase Ca = increase heart rate

negative inotropic drugs eg verapamil

Question 4

What are the three types of inotropic drugs?

Answer 4

1. cardiac glycosides
2. sympathomimetics
3. phosphodiesterase inhibitors

Question 5

What is an example of a cardiac glycoside?

Answer 5

digitalis

found in foxgloves

Question 6

What is the mechanism of digoxin?

Answer 6

inhibits Na/K ATPase = more Ca in cell = contraction increased

positive inotropism

it also blocks AV conduction, reducing HR by enhancing vagal nerve activity

Question 7

What are uses of digoxin?

Answer 7

• permanent/persistent atrial fibrillation (not first line)
• first line for patients with AF who also have co-existing heart failure
• if heart failure is due to left ventricular dysfunction and condition has worsened even after using ACEi, diuretics and beta blockers

Question 8

What are signs and symptoms of digoxin toxicity?

Answer 8

• bradycardia
• arrhythmia
• nausea, vomiting
• confusion
• visual disturbances

Question 9

What is the dosing for digoxin?

Answer 9

• high initial loading dose 5mcg/kg of lean body weight
• maintenance dose calculated adjusted for renal function

Question 10

What is the monitoring for digoxin?

Answer 10

• to make toxicity isnt developing
• monitor urea and electrolytes

Question 11

Where are the a-receptors, b1-receptors and b2-receptors and what is their action?

Answer 11

a-receptors: in vasculature, agonists cause vasoconstriction

b1-receptors: expressed in heart, agonists are positively chronotropic

b2-receptors: vasculature, agonists cause vasodilatation

Question 12

Describe the use of dopamine

Answer 12

medium dose: b1 tachycardia and increased contraction

large doses: a effects = peripheral vasoconstriction

it is a sympathomimetic

Question 13

What is the function of Ad and NAd?

Answer 13

Ad: acts on all three receptors

used in cardiac arrest = peripheral vasoconstriction (a effects) and strong positive chronotropia (b1 effects)

NAd: a adrenoreceptor agonist -vasoconstrictor action

Question 14

Talk about the use of phosphodiesterase inhibitors.

Answer 14

rarely used in clinical practise trials - increase in risk of mortality

used only in severe HF

eg enoximone

Question 15

Whats the mechanism for phosphodiesterase inhibitors?

Answer 15

increase cAMP - increased contractility and heart rate

cAMP broken down by PDE

phospodiesterase inhibits breakdown of cAMP

Question 16

What is inotropy and chronotropy?

Answer 16

inotropy - increeased contractility

chronotropy - increased heart arte

Question 17

What are the three types of HF?

Answer 17

• HF caused by left ventricular systolic dysfunction LVSD
  
  • left ventricle becomes weak
• HFpEF
  
  • left ventricle becomes stiff, difficult for heart chamber to fill with blood
• HF caused by diseased or damaged valves

Question 18

What are symptoms of HF?

Answer 18

• rapid weight gain
• shortness of breath
• increased welling in lower body
• frequent dry, hacking cough
• loss of appetite

Question 19

What is first line treatment for people with HFrEF?

Answer 19

• ACEi
  
  • start at low dose and titrate upwards at short intervals until target dose reached
  • measure serum sodium and potassium, assess renal function before and to 2 weeks after starting and after each dose increment
  • take first dose at night and report troublesome dry cough
• beta blockers
  
  • low dose, work upwards
  • side effects: fatigue, cold hands
  • do not stop taking