3 IHD drugs

Question 1

what are the 4 determinants of cardiac oxygen requirement?

Answer 1

• preload: diastolic filling pressure (depends on blood volume and venous tone)
• afterload: reistance to ejection of stroke volume (depends on arterial blood pressure)
• heart rate
• cardiac contractility

Question 2

why does angina occur?

Answer 2

insufficient coronary blood flow to meet oxygen demands of the myocardium

demand > supply

Question 3

4 classes of drugs for therapy of angina + examples

Answer 3

• vasodilators: nitrates, CCB
• cardiac depressants: CCB, beta blockers
• nitrates: GTN, isosorbide mononitrate
• cardiac pacemaker retardant: ivabradine

Question 4

MoA of nitrates

GTN, ISMN

Answer 4

supplies NO (endogenous vasodilator)
→ activate guanylyl cyclase
→ increase conversion of GTP to cGMP
→ inactivate myosin-Light chain
→ leads to relaxation of vascular smooth muscle

Question 5

2 therapeutic effects of nitroglycerin

Answer 5

vasorelaxation
- venodilation → preload ↓
- arteriolar dilation → afterload ↓

∴ oxygen consumption ↓

Question 6

routes of administration of GTN
onset & duration of action

vvv IMPT!

Answer 6

sublingual GTN
faster onset 1-5 min
shorter duration 10-30 min

transdermal GTN
slower onset 30-60 min
longer duration 7-10 h

∴ use sublingual GTN for emergency

Question 7

when to use ISMN and how does it work

Answer 7

oral isosorbide mononitrate
onset 30-45 min
duration 6 h

∴ use ISMN for angina pectoris prophylaxis

venous dilatation
→ peripheral pooling of blood
→ decrease venous return, reduce left ventricular end-diastolic pressure (preload)

dilate arterties
→ reduce systemic vascular resistance and arterial pressure
→ reduce cardiac afterload

direct dilatory effect on coronary arteries
→ lowers intramural pressure
→ improve subendocardial blood flow

Question 8

3 side effects of nitrates

Answer 8

vasorelaxation
- baroreflex → tachycardia
- venodilation → hypotension
- meningeal artery vasodilation → headache

Question 9

MoA of beta blockers for IHD / angina

cardiac depressant

Answer 9

blocks β1-AR of heart
→ ↓ contractility and HR
→ reduce cardiac oxygen requirements

Question 10

Who is beta blockers contraindicated in?

MUST KNOW!

Answer 10

Contraindicated in diabetic patients because it will mask the symptoms of hypoglycemia

MUST KNOW!

no feedback to tell if hypoglycaemia because heart cannot beat fast (blocked by β blocker)
patient may fall into hypoglycaemic coma

Question 11

MoA of CCBs

Verapamil, Diltiazem, Nifedipine, Amlodipine

Answer 11

Verapamil & Diltiazem (anti-arrhythmic)
treatment of arrhythmia:
decrease transmission of electrical signals from SA node and AV node → decrease supraventricular reentry tachycardia

Nifedipine, Amlodipine (anti-angina & anti-hypertensive)

treatment of angina:
decrease myocardial contractility → decrease oxygen requirement

treatment of HTN:
decrease myocardial contractility → decrease CO → decrease BP
decrease vascular smooth muscle tone → decrease BP

Question 12

Clinical indications for 3 CCBs

only in IHD can use both DHP and non-DHP

Answer 12

Lowering BP: Verapamil = Diltiazem = Nifedipine
all equal

Vasodilator: Nifedipine > Diltiazem > Verapamil (worst)

Cardiac depressant: Verapamil (best) > Diltiazem > Nifedipine

Question 13

Name 3 adverse effects of CCBs

Answer 13

Cardiac depression:
- bradycardia
- AV block
- heart failure

and hypotension

C in CCB for cardiac depression!

Question 14

Ivabradine

cardiac pacemaker retardant

Answer 14

inhibits cardiac pacemaker I(f) current that controls the spontaneous diastolic depolarisation in the sinus node
→ lowers HR
→ reduce cardiac workload and myocardial oxygen consumption

so indicated for stable angina pectoris

Question 15

3 adverse effects of ivabradine

Answer 15

visual problems
dizziness (bc bradycardia)
hypotension, fatigue, malaise (bc bradycardia)