drugs and the heart

Question 1

give some drugs that decrease the HR and outline their MOA

Answer 1

β-blockers – Decrease If and Ica

Calcium antagonists – Decrease Ica

Ivabradine – Decrease If

Question 2

give some drugs that decrease cardiac contractility and outline their MOA

Answer 2

β-blockers – Decrease contractility

Calcium antagonists – Decrease Ica

Question 3

what are the 2 classes of calcium antagonists?

Answer 3

Rate slowing (Cardiac and smooth muscle actions)
Phenylalkylamines (e.g. Verapamil)
Benzothiazepines (e.g. Diltiazem)

Non-rate slowing (smooth muscle actions – more potent)
Dihydropyridines (e.g. amlodipine)

Question 4

what are some drugs that influence myocardial oxygen demand/supply? outline their MOA

Answer 4

organic nitrates

K+ channel opener

Question 5

what are the side effects of beta blockers?

Answer 5

Worsening heart failure

CO reduction

Increased vascular resistance

Bradycardia

Heart block – decreased conduction through AV node

cold extremities

hypoglycaemia

Question 6

why might beta blockers cause cold extremities

Answer 6

vasoconstriction in cutaneous vessels so reduced blood flow to peripheral areas eg. hands, causing cold extremities.

Question 7

what are some side effects of calcium channel blockers?

Answer 7

Verapamil (rate slowing)

Bradycardia and AV block (Ca2+ channel block)

Constipation (Gut Ca2+ channels) – 25 % patients

Dihydropyridines(non-rate slowing) – 10-20% patients

Ankle Oedema – vasodilation means more pressure on capillary vessels

Headache / Flushing – vasodilation

Palpitations

vasodilation may result in reflex tachycardia

Question 8

what is the main risk of arrhythmias?

Answer 8

sudden death

stroke (due to increased clotting from irregular beats)

Question 9

recallthe Vaughan-Williams classification of anti arrhythmic drugs

Answer 9

1. Sodium channel blockade
2. Beta adrenergic blockade
3. Prolongation of repolarisation
4. Calcium channel blockade

Question 10

define hypertension

Answer 10

Blood pressure (BP) = cardiac output (CO) x total peripheral resistance (TPR)

Hypertension is defined as being consistently above 140/90 mmHg

Question 11

what is the first line of treatment of hypertension?

Answer 11

Angiotensin converting enzyme (ACE) inhibitor OR angiotensin receptor blocker - under 55

Calcium channel blocker (CCB) or thiazide-like diuretic- over 55

Question 12

what is the second line of treatment for hypertension

Answer 12

combine the 2 drugs from step 1

CCB or thiazide-like diuretic & ACEi or ARB
ARBs preferred to ACEi for AfroCaribbean’s

Question 13

describe the MOA of ACE inhibitors

Answer 13

reduction in angiotensin II production

less Na+ reabsorption in kidney

decreased water retention so plasma volume decreases, lowering blood pressure

decrease in SNS activation causing thirst

reduces vasoconstriction

reduction in aldosterone secretion

Question 14

what are the uses for ACE inhibitors

Answer 14

• hypertension
• heart failure
• post-myocardial infarction
• diabetic nephropathy
• progressive renal insufficiency
• patients at high risk of cardiovascular disease

Question 15

what are some side effects of ACEI and ARBs?

Answer 15

cough (ACEI)- bradykinin

hypotension/postural hypotension

hyperkalaemmia (take care if also taking K supplements or K sparing diuretics)

renal failure in patients with renal artery stenosis