Therapeutics - approach to treatment

Question 1

Why administer drugs?

Answer 1

Cure underlying disease Prevent or slow progression of disease Increase life expectancy Improve quality if not length of life

Question 2

Outline steps to appropriate management - 4

Answer 2

Correct ID of underlying disease Stage severity Apply EBVM In absence of ‘best evidence’, make an informed and rational decision

Question 3

Define EBVM

Answer 3

the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients

Question 4

What is the best evidence?

Answer 4

Well-designed, blinded, prospective studies. The next-best evidence comes from lower quality sources such as case-control studies, retrospective uncontrolled studies, case series, individual case reports and expert opinion.

Question 5

What is the best evidenced tx for MVD (dogs)?

Answer 5

Pimobendan ACEI Spironolactone

Question 6

Best evidenced Tx for DCM

Answer 6

Pimobendan and ACEI

Question 7

Best evidenced Tx for feline HCM

Answer 7

ACEI

Question 8

How can CSs of cardiac disease be divided up in terms of thinking about therapy?

Answer 8

Is the patient showing congestive signs (wet) or outpt signs (i.e. ‘cold’) or both?

Question 9

Define lusitropy

Answer 9

the ability of the heart to relax

Question 10

What are the different signs that could underlie the the signs present in a patient?

Answer 10

Increased preload Increased afterload Impaired inotropy Impaired lusitropy Abnormalities of cardiac rate and rhythm

Question 11

Main sign of excessive preload

Answer 11

Congestion - detectable on PE or radiographs. Oedema, ascites, peripheral oedema, pleural oedema, pleural effusion and venous congestion

Question 12

Tx - preload reduction

Answer 12

DIURETICS AND VENODILATORS

Providing the underlying disease is readily rectifiable, diuresis with or without venodilation will be required.

Question 13

When to treat for afterload reduction? How?

Answer 13

Patients are likely to appear pale or cold. Treatment for this will help when the patient has mitral regurgitation. HOW: arteriodilators (if no fixed obstruction)

Question 14

When might you want to improve systolic function?

Answer 14

DCM and later stages of MVD. Use inotropic agents may improve output and signs.

Question 15

When might diastolic function need to be improved? What drugs should be used?

Answer 15

when the heart muscle is excessively hypertrophied or where there is excessive fibrosis. DRUGS TO USE: hasten relaxation (calcium channel blockers), slow HR (beta-blockers) or reduce fibrosis (ACEI).

Question 16

How can you optimise heart rate and rhythm?

Answer 16

Changing SV and HR and therefore CO.

Question 17

List classes of diuretic

Answer 17

• DIURETICS - Frusemide and Torasemide - THIAZIDES - chlorothiazide, hydrochlorothiazide - POTASSIUM SPARING DIURETICS: spironolactone, amiloride

Question 18

How can diuretics be used initially and when they become refractory to this?

Answer 18

• USUALLY START DIURESIS WITH A SINGLE AGENT: fursemide at 1-2mg/kg orally 2-3 times, administer at higher doses and IV where animal is in more severe HF. WHEN PATIENT BECOMES REFRACTORY TO FRUSEMIDE: can increase dose, increase freqency, introduce second diuretic - sequential blockade (spironolactone), swap to torasemide

Question 19

Risks of diuresis

Answer 19

Hypovolaemia Hypotension Electrolyte disturbances Stimulation of RAAS

Question 20

Outline venodilation

Answer 20

VENODILATORS - glyceryl trinitrate - percutaneously administered ointment or cutaneous patches BALANCED VASODILATORS - act on arteries and veins - ACEI, pimobendan and nitroprusside

Question 21

Define afterload

Answer 21

the peak ventricular wall tension during systole

Question 22

What are the benefits of afterload reduction?

Answer 22

Increased SV Increased CO Decreased MR Reduced systolic wall tension reduces cardiac work - decreased myocardial oxygen demand, improved oxygenation of the myocardium

Question 23

Risks of afterload reduction

Answer 23

Hypotension Reduction in SVR may result Decreased BP may compromise perfusion of essential vascular beds

Question 24

List agents for afterload reduction

Answer 24

BALANCED VASODILATORS: ACEI, pimobendan, others (calcium channel blockers - amlodipine, xanthnes, alpha-blocers), ARTERIODILATORS - hydralazine

Question 25

What are problems with inotropes?

Answer 25

INCREASED MYOCARDIAL WORK - may be associated with increased rate of myocardial deterioration, increased mortality in humans INCREASED MYOCARDIAL OXYGEN DEMAND - exacerbate ischaemia/hypoxia, may lead to rhythm disturbances DIGOXIN EXCEPTION DUE TO OTHER EFFECTS: reduced HR, decreased SNS tone.

Question 26

What is pimobendan evidence for?

Answer 26

Good evidence of efficacy in DCM after the onset of HF

Question 27

What are indications for other inotropes?

Answer 27

SYSTOLIC FAILURE SHORT TERM REQUIRED AS EMERGENCY MEASURE - dobutamine infusion DIGOXIN: HF associated with systolic failure of myocardium, supraventricular rhythm disturbance

Question 28

What broad categories of drugs can you use to improve output signs? 3

Answer 28

Inotropes Afterload reduction Anti-arrhythmics

Question 29

How can you improve congestive signs? 2

Answer 29

Diuretics/venodilators Preload reduction

Question 30

Outline the use of anti-arrhythmic agents

Answer 30

Controversial and fairly hazardous area No licensed agents Always do with caution

Question 31

What are overall aims of therapy - 4

Answer 31

• Restore adequate peripheral perfusion - Control rate and frequency of rhythm - Restore sinus rhythm - not always possible or necessary - Prevention of sudden death

Question 32

How can cardiac rate and rhythm be optimised? 3

Answer 32

ANTI-DYSRHYTHMIC MEDICATION: - ventricular arrhythmias (lignocaine, procainamide, beta-blockers) - supraventricular arrhythmias (digoxin, calcium channel blockers, beta-blockers) - Bradyarrhythmias (atropine, propantheline bromide, xanthines, pacing)

Question 33

What should you do if you diagnose AF?

Answer 33

See diagram

Question 34

Broad treatment option for afterload reduction

Answer 34

Arteriodilators OR balanced vasodilators

Question 35

Main Tx to enhance systolic function

Answer 35

Inotropes

Question 36

Main Tx to enhance diastolic function

Answer 36

Lusitropes OR negative chronotropes

Question 37

Main Tx to optimise cardiac rate and rhythm

Answer 37

Anti-arrhythmics (not licensed and potentially hazardous. Use all with care and only when you are certain they are indicated)

Question 38

When are anti-thrombotics principally used?

Answer 38

In cats at risk of aortic thromboembolism - aspirin adn clopidogrel