Pharmacology - Drugs Affectign Cardiac Rate and Force

Question 1

What impact does the sympathetic system have on cardiac rate and force?

Answer 1

Increased heart rate
Increased contractility
Increased conduction velocity at AV node
Increased automaticity
Decreased duration of systole
Slide 5+6

Question 2

Why is there decreased contractility of the heart when innervated by the parasympathetic system ?

Answer 2

There is a dcrease of phase 2 in cardiac action potential and decreased Ca entry. Slide 8

Question 3

How is the pacemaker potential affected?

Answer 3

The ‘funny current’ (depolarising current) can change it.

These funny currents are controlled by channels through hyperpolarisation and cyclic AMP HCN channels. Slide 9

Question 4

What is an example of a selective HCN channel blocker?

Answer 4

Ivabradine.

When the HCN channels are blocked, it decreases the slope of the potential and reduced HR. Slide 9

Question 5

What is Milrinone used for and what does it target?

Answer 5

Only used for acute heart failure to sustain cardiac function.
It inhibits the enzyme PDE which allows increased contractility. Slide 12

Question 6

What are examples of catecholamines and what do they target?

Answer 6

Examples are Dobutamine, Adrenaline and Noradrenaline.
They are agonists on B adrenoceptors.
Slide 13

Question 7

Clinically what can adrenaline be used for?

Answer 7

Cardiac arrest as a part of the ALS treatment algorithm
Anaphylactic shock
Slide 14

Question 8

What clinically can dobutamine be used for?

Answer 8

Acute heart failure. Slide 14

Question 9

What are some selective and non selective B adrenoreceptors antagonists?

Answer 9

Non selective: Propranolol and alprenolol.
Selective:
Atenolol, bisoprolol and metoprolol. Slide 15

Question 10

What are the clinical uses in the CVS of B adrenoceptor antagonists?

Answer 10

Treatment of arrhythmias e.g. stress or AF
Treatment angina
Treatment heart failure
Treatment hypertension. Slide 16

Question 11

What are some adverse effects of B blockers?

Answer 11

Bronchospasm
Uncompensated heart failure might get worse
Bradycardia
Hypoglycaemia
Fatigue
Cold extremities
Slide 17

Question 12

What is Atropine used for and what do you have to be careful when using it?

Answer 12

Non selective muscurinic ACh receptor antagonist.
Increase HR
First line for severe bradycardia, especially after MI
However, in low doses it can actually lower heart rate so must start dose between 300-6000mg. Slide 18

Question 13

How does Digoxin work and what do you have to be careful of?

Answer 13

Increases contractility of heart by blocking the sarcolemma Na/K ATPase allowing Ca build up.
However it has a very narrow therapeurtic window. Slide 20+21

Question 14

What are the direct and indirect effects of Digoxin on electrical activity?

Answer 14

Indirect: Slows SA node discharge and slows AV conduction.
Direct: Shortens action potential and refractory periodd. Slide 21

Question 15

What is the clinical use of Digoxin and what are adverse side effects?

Answer 15

Acute heart failure (IV)
Chronic heart failure (oral)
Heart failure with AF
Adverse side effects:
Excessive depression of AV node - arrythmias
Nausea
Diarrhoea
Slide 22

Question 16

What does Levosimendan do and when is it used?

Answer 16

Increase troponins sensitivity to Ca.

Used for acute decompensated heart failure (IV). Slide 23

Question 17

What are examples of drugs which inhibit PDE in cardia and smooth msucle cells?

Answer 17

Amrinone and milrinone. Slide 24