Angina Pharm Flashcards
What is angina?
lack of sufficient oxygen (ischemia) to the heart that causes pain
Why does angina occur?
coronary artery obstruction limits blood supply to part of the myocardium
What is exertional angina? What is the cause?
coronary circulation can meet oxygen demands of the myocardium at rest, but not when the heart work increases by exercise (due to atheroma/fixed coronary vascular obstruction)
What is Prinzmetal’s angina? What is it also called? Prognosis?
Variant angina. Occurs when vasospasm blocks blood flow. Excellent prognosis.
What is unstable angina? What is its cause?
Recurrent angina associated with minimal exertion. Caused by atherosclerosis and thrombosis (formed by platelet aggregation after fissuring of plaques) that blocks blood flow
Heart work “demand” is determined by what?
HR
Cardiac contractility
Wall tension (afterload)
Heart (O2) “supply” is determined by what?
coronary vascular resistance
perfusion pressure
collateral blood flow
HR and mechanics
What type of angina has a high correlation with MI?
unstable angina
What type of angina will have normal coronary angiograms?
Prinzmetal’s (variant) angina
What are the 3 major approaches for treating angina?
1) Increase coronary blood flow
2) Reduce myocardial oxygen consumption
3) Prevent platelet deposition/aggregation
What are the 3 ways to reduce myocardial oxygen consumption?
1) Negative chronotropic effect (decrease HR)
2) Negative inotropic effect (decrease contractility)
3) Decrease ventricular workload (reduce preload or afterload)
What is the effect of venodilation?
reduced preload
What is the effect of vasodilation?
reduced afterload
When does the heart receive greatest perfusion? How do we exploit this to get relief of angina?
During diastole, because blood vessels are allowed to relax and serve the subendocardium. You want to increase the amount of time the heart is in diastole (use beta blockers/calcium channel blockers)
What are the two major effects of nitrate treatment for angina? How do these help?
1) Venodilation (decrease in preload and increase in subendocardial blood flow)
2) Coronary vasodilation (reperfuse ischemic areas, prevent/reverse coronary vasospasm)
What are the hemodynamic effects of nitrate therapy?
1) BP unchanged or slightly decreased
2) HR unchanged or slightly decreased
3) Pulmonary vascular resistance decreased
4) Slight reduction in CO
What is the cellular mechanism of nitrate action?
Nitrovasodilators undergo denitration to release NO. This activates guanylate cyclase to elevate intracellular cGMP that works through PKG to cause relaxation of vascular SM that leads to venodilation and coronary vasodilation.
How does the nitrate vasoreactant pathway change over time?
it decreases with age
What are the ROAs of nitrate drugs? List the drugs by group
1) Mucosal (spray, sublingual): Nitrostat, Nitrogard
2) Oral: Isordil, Ismo, Nitro-SR
3) Transdermal: Nitrol ointment
4) IV: Tridil
What is the most common adverse effect of nitrates? Why does this occur?
Headache. Due to vasodilation of meningeal arteries (vasomotor headache) that is transient and can be treated with aspirin or Tylenol
What adverse effect is commonly seen with higher doses of nitrates? Why? Compensatory responses?
Hypotension from arterial vasodilation. This may trigger reflex sympathetic stimulation of the heart (tachycardia, decreased coronary perfusion, etc.) that may worsen angina.
What adverse effects of nitrates are commonly seen in patients who are sensitive to reductions in preload (they are volume depleted, have a valvular heart disease, or HCM)?
Dizziness, orthostatic hypotension, syncope
What adverse effect is seen with long acting nitrates or cutaneous nitrates?
drug rash
What drugs are ABSOLUTELY contraindicated with nitrates? Why?
Sildenifil (Viagra) and other Type V PDE inhibitors that increase levels of cGMP by preventing its breakdown (this compounds the effect of nitrates and can lead to profound hypotension and MI)
What is the major problem with continuous nitrate therapy?
Tolerance- frequently repeated or continuous exposure to high doses of organic nitrates leads to a marked attenuation of their biological effects. Worse problem with high doses or oral, transdermal or IV.
How do you get around the problem of nitrate tolerance?
have 8-12 hours of “nitrate free” intervals each day (usually at night) OR (for IV) titrate dose upward until effect is seen so that you are using the minimal required dose
What is the most important mechanism of nitrate tolerance?
depletion of tissue cysteine stores (so that the nitrate can no longer form NO)
What is anginal rebound?
Sudden interruption of IV nitroglycerin in unstable angina leads to coronary vasospasm. This is why you MUST overlap with transdermal or oral form when you are withdrawing someone from nitrates
What are the 3 major uses of CCBs?
1) Angina
2) HTN
3) Supraventricular arrhythmias
What are the three chemical classes of CCBs?
1) Phenylalkylamines
2) Benzothiazepines
3) Dihydropyridines
List the phenylalkylamine used for angina treatment.
Verapamil
List the benzothiazepine used for angina treatment.
diltiazem