Cardiovascular

Question 1

What period during the action potential is important for the prevention of constant state of contraction from recycling impulses in cardiac cells?

Answer 1

Refractory

Question 2

Name 3 basic mechanisms that come into play when cardiac function is compromised

Answer 2

Autoregulation of muscle fibre length (hypertrophy)
Neural/autonomic control (heart rate and contractility)
Endocrine control (RAAS)

Question 3

What are the major determinants of cardiac output?

Answer 3

Heart rate, contractility, venous return (preload), total peripheral resistance

Question 4

Outline some of the major objectives of treating cardiac complications

Answer 4

Stop/reverse arrhythmias
Increase/maintain cardiac output
Maintain correct vascular tone
Relieve fluid retention or treat hypovolemia
Supportive therapy

Question 5

What are potential causes of hypotension?

Answer 5

Trauma / severe haemorrhage
Cardiac disease 
Cardiogenic shock
Cardiac arrhythmias 
Addison's disease
Iatrogenic (anaesthetics / other drugs)

Question 6

Outline the general approach that may be taken to alleviate acute hypotension

Answer 6

correct hypothermia, check and correct volume deficits / electrolyte imbalances, stop / withdraw hypotension inducing drugs, consider vasopressors and positive inotropes

Question 7

Which drugs may potentiate / aggravate hypotension

Answer 7

Most general anaesthetics and premeds (alpha1-antagonists, beta-blockers, alpha2-agonists), antiarrhythmogenic drugs, furosemide

Question 8

Cardiac glycoside, causes positive inotropy, has narrow therapeutic index

Answer 8

Digoxin

Question 9

Membrane stabiliser, drug of choice for ventricular arrhythmias given IV

Answer 9

Lignocaine

Question 10

Beta-blocker, useful against hypertrophic cardiomyopathy, and ventricular arrhythmia

Answer 10

Propranolol

Question 11

Sympathomimetic, causes positive inotropy, only used for a short period

Answer 11

Dobutamine

Question 12

A loop diuretic of choice against congestive heart failure

Answer 12

Furosemide

Question 13

Non-catecholamine, positive inotropy and vasodilator (inodilator). May be useful against dilated cardiomyopathy.

Answer 13

Pimobendan

Question 14

What is an inodilator?

Answer 14

Has both positive inotropic and vasodilatory effects

Question 15

Causes vasodilation by inhibiting ACE

Answer 15

Enalapril

Question 16

Used against vagal-mediated bradycardia, asystolic cardiac arrest

Answer 16

Atropine

Question 17

What is AV block?

Answer 17

Marked slowing or blocking of impulses going through the AV node to cause ventricular depolarisation

Question 18

What is the difference between first and second degree AV block?

Answer 18

First degree - the impulse is only slowed (characterised by prolonged PR intervals on the ECG)
Second degree - total blockade of the impulse transmission (characterised by the presence of P waves with no corresponding QRS complexes)

Question 19

What is the treatment of choice for AV block?

Answer 19

A cholinergic antagonist - Atropine

Question 20

How can propranolol cause AV block?

Answer 20

Blockade of sympathetic drive to the heart allows the parasympathetic system to dominate - slows impulses through the AV node

Question 21

What side affects are associated with arrhthmogenic drugs?

Answer 21

Hypotension, AV block, depressed cardiac contractility, CNS toxicity, hypersensitivity

Question 22

Describe the mechanism of action of cardiac glycosides

Answer 22

Blocks the Na-K-ATPase pump, increases intracellular Na, slowing the Na/Ca exchanger and increasing intracellular Ca2+

Question 23

What are the pharmalogical effects of cardiac glycosides?

Answer 23

Positive inotropy, decreased heart rate secondary to hemodynamic changes, slowed sinus and AV consuction, diuresis

Question 24

What are the effects of Quinidine on glycoside therapy?

Answer 24

Quinidine displaces cardiac glycosides from binding sites in muscle which may the elevate glycoside plasma levels and cause toxicity

Question 25

What are the signs of glycoside toxicity?

Answer 25

Anorexia, vomiting and lethargy
Hypothermia, AV conduction block and bradycardia
Ventricular tachyarrhythmias, renal toxicity

Question 26

How can you treat glycoside toxicity?

Answer 26

Withdraw the glycoside, symptomatic treatment, cholestyramine resin and activated charcoal

Question 27

Why can combining NSAIDs with furosemide lead to serious pharmacodynamic interactions?

Answer 27

NSAIDs inhibit the natriuretic effect of furosemide due to inhibition of renal blood flow. Some animals may develop furosemide/loop diuretic resistance.

Question 28

Depolarisation of cardiac cells is characterised by a rapid influx of ____ ions, a slow influx of ____ ions and an outflow of ____ ions. Fill in the blanks.

Answer 28

Rapid Na+ influx, Slow Ca2+ influx, Efflux of K+