Drugs Used in Chronic IHD Flashcards

1
Q

Classic angina

A

Occlusion of coronary aa. resulting from atherosclerotic plaque

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2
Q

Variant (Prinzmetal) angina

A

Episodes of vasoconstriction of coronary aa.

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3
Q

Angina def:

A

Imbalance between oxygen demand of the heart and oxygen supply via the coronary aa.

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4
Q

Why does angina occur during exercise or stress?

A

Oxygen demand of the heart increases significantly, which is greater than the supply of oxygen through the partially blocked coronary a.

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5
Q

3 approaches to treating angina pectoris

A
  1. Decrease cardiac work
  2. Increase blood flow through coronary aa.
  3. Reduce myocardial oxygen demand
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6
Q

What is the best way to treat vasospastic (Prinzmetal) angina?

Is it helpful in classic angina?

A

Increase coronary blood flow using vasodilators.

No.

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7
Q

What is the “coronary steal” phenomenon?

A

The redistribution of blood to non-ischemic areas associated w/ dilation of small arterioles. This is the reason vasodilators don’t work well in classic angina.

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8
Q

3 phases of phasic coronary flow

A
  1. Isovolumetric contraction
  2. Ejection
  3. Diastole
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9
Q

3 drug classes used in chronic IHD

A

Nitrates
Ca++ channel blockers
Beta-blockers

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10
Q

How do organic nitrates work?

A

Once ingested, the nitrates are activated and lead to SM relaxation and vasodilation.

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11
Q

3 Nitrovasodilators (nitrates)

A

Nitroglycerin
Isosorbide dinitrate
Isosorbide mononitrate

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12
Q

What is the first-pass metabolism of nitrates?

A

It is significant, meaning the oral bioavailability is low. Other routes that avoid the GI tract are used mostly.

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13
Q

What nitrate is a poor substrate of nitrate reductase and has a greater bioavailability?

A

Isosorbide mononitrate

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14
Q

What is needed to release NO from nitrates?

A

Thiols

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15
Q

What does NO dilate?

A

Veins and large arteries (higher conc. needed for aa.)

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16
Q

NO dilates veins and arteries. What is the effect of dilating them?

A

Veins:

  • increased venous capacitance
  • reduced ventricular preload

Arteries:
-reduce afterload

*there is no substantial increase in coronary blood flow into the ischemic area in classic angina.

17
Q

MOA of nitrates to treat variant angina

A

Vascular SM relaxation -> coronary a. dilation -> coronary spasm relief

18
Q

MOA of nitrates to treat classic angina

A

Venous dilation -> reduced preload -> decrease oxygen demand

19
Q

4 ways to develop tolerance to nitrates

A

Depletion of thiol components

Increased generation of superoxide radicals (leads to depletion of NO)

Reflex activation of SNS

Salt and water retention

20
Q

What is the use of short-acting nitrates vs. long-acting nitrates?

A

Short-acting: relieve angina attack

Long-acting: prevent future attacks

21
Q

S/E of nitrates

A

HA

Orthostatic hypoTN

Tachy/inotropy

Increased Na+ and water reabsorption

22
Q

3 Non-cardioactive (Dihydropines) Ca++ channel blockers

A

Amlodipine (long-acting)
Nifedipine (short-acting)
Nicardipine (short-acting)

23
Q

2 Cardioactive Ca++ channel blockers

A

Diltiazem

Verapamil

24
Q

Ca++ channel blockers MOA

A

Ca++ enters via voltage-dependent Ca++ channels to cause SM contraction, so by blocking it, it is inhibited.

25
What are some anti-anginal mechanisms of Ca++ channel blockers for classic angina?
Decrease myocardial oxygen demand. - dilation of peripheral aa. -> dec. PVR and afterload, decreased BP. - arterioles are more affected than vein.s All of this leads to decreased cardiac contractility and HR.
26
What are some anti-anginal mechanisms of Ca++ channel blockers for variant angina?
Increased blood supply by dilating coronary aa. to relieve local spasm.
27
Major S/E of Ca++ channel blockers? Minor?
Cardiac depression/arrest Acute HF (cardioactives) Bradyarrhythmias, AV block Flushing, HA, anorexia, dizziness, edema, constipation.
28
What's a unique S/E of NIfedipine (immediate-release)?
Increases risk of MI in pts. w/ HTN
29
4 beta-blockers indicated in angina
Propranolol Nadolol Metoprolol Atenolol
30
MOA of beta-blockers for treating angina
Decreased myocardial oxygen demand. - decreased HR -> improved myocardial perfusion. - decrease contractility - decrease in BP leads to reduced afterload
31
S/E of beta-blockers
``` Reduced CO Bronchoconstriction Poor Glc metabolism Bad LDL/HDL profile Sedation SNS hyperresponsiveness ```
32
Contraindications for use of beta-blockers
``` Asthma Peripheral vascular DZ T1DM Bradyarrhythmias Low cardiac function ```
33
Using nitrates alone, what are 2 major undesirable effects?
Increased HR Increased contractility
34
Using either beta-blockers or Ca++ channel blockers, what are 2 major undesirable effects?
Increased end-diastolic vol. Increased ejection time
35
Overall, what is the approach to a pt. w/ variant angina?
Prevention is the choice, but: | Ca++ channel blockers are first choice. If they are contraindicated, long-acting nitrates are used.
36
Overall, what is the approach to a pt. w/ classic angina?
Lifestyle mods/prevention/diet, etc are first choice, but: 1. Beta-blocker (or CCB or LA nitrate) 2. Add CCB or BB (if not used first) 3. Consider triple therapy 4. CABG surgery