Drugs to treat angina background

Coronary artery disease/ ischemic heart disease definition

Chronic condition caused by atherosclerotic narrowing/blockage of coronary arteries

• leads to inadequate coronary blood flow to the heart

• results in an imbalance between myocardial oxygen demand and supply

• increases the risk of myocardial ischemia

What is myocardial ischemia?

• when myocardial O2 demand is greater than the O2 supply to the heart

• typically due to reduced coronary blood flow

• reversible if perfusion is restored

What is angina pectoris?

• a symptom of CAD

• chest pain from transient myocardial ischemia

• usually starts in chest and radiates to left arm, jaw, back

• no myocyte death occurs

What is a myocardial infarction?

• irreversible death of myocardial cells caused by prolonged ischemia (20-40 minutes)

Stable angina cause

Fixed atherosclerotic narrowing (stable plaque)

When does stable angina occur?

occurs only with exertion (demand ischemia)

Variant angina cause

Transient constriction of coronary arteries (vasospasm)

When does variant angina occur?

occurs at rest (supply ischemia)

What causes unstable angina

plaque rupture → platelet aggregation → non-occlusive thrombus

Causes new, worsening, or at rest chest pain

Causes transient ischemia, no infarction

Unstable angina is a precursor to what?

NSTEMI and STEMI

Acute coronary syndrome

spectrum of clinical conditions caused by acute myocardial ischemia, typically due to plaque rupture, platelet aggregation, thrombus formation, and decreased coronary blood flow

What are the 3 types of ACS?

Unstable angina

Non-ST segment elevated MI

ST segment elevated MI

Does unstable angina elevate ST wave?

no

What is NSTEMI?

Non-ST segment elevated MI

Partial occlusion with infarction (increased troponin)

What is STEMI?

ST segment elevated MI

Complete occlusion with infarction (increased troponin)

Determinants of myocardial O2 demand

• HR

• Contractility

• afterload

• preload

Determinants of myocardial O2 supply

• coronary blood flow

• regional myocardial blood flow

What is the equation used to estimate myocardial O2 consumption (MVO2)?

HR x Systolic BP

What class(es) of drugs treat stable angina and work to decrease O2 demand by lowering HR and contractility?

B-blockers and non-DHP CCBs

What class(es) of drugs treat stable angina and work to decrease O2 demand by decreasing preload?

Organic nitrates

What class(es) of drugs treat stable angina and work to decrease O2 demand by decreasing afterload?

All CCBs

High dose nitrates

What class(es) of drugs treat variant angina by increasing O2 supply?

Vasodilators → all CCBs, organic nitrates

Therapeutic goal in stable angina

decrease O2 demand

therapeutic goal in variant angina

increase O2 supply

Why can’t beta blockers be used to treat variant angina?

They have no mechanism to increase O2 supply, they only decrease O2 demand

Why are non-selective b blockers contraindicated in variant angina?

may worsen vasospasm by allowing unopposed a1 mediated vasoconstriction

Therapeutic goal in unstable angina

prevent thrombus expansion and infarction

Primary treatment for unstable angina

antithrombotic agents:

antiplatelets

anticoagulants

What drug class are first line agents for ischemia control and reduces risk of progression to MI in unstable angina?

Beta blockers, by reducing O2 demand

What are the second line agents for ischemia control and reduces risk of progression to MI in unstable angina?

Non DHP CCBs, if b blockers are contraindicated/not well tolerated

Role of nitrates in unstable angina

rapid chest pain relief via decrease in preload and coronary vasodilation