Cardiac Medications Used To Treat Angina Pectoris
Types of Angina
After all is said and done, angina pectoris is due to an imbalance between the work being demanded of the heart and the amount of perfusion the heart has moment to moment.Example : If the person has just eaten a large meal, the body diverts a great deal of blood to the digestive system in order to digest the meal. This takes away blood volume from other organs, including the heart. Why, then, would a large meal place a burden on the heart ?
Answer : Eating causes an increase in the heart rate just due to the thermogenic effects of food and the shunting of blood to the digestive tract. The increased heart rate represents an increased work burden on the heart. In hearts that are already sick (CAD) the increased heart rate, shortened diastolic rest phase and the increase in myocardial oxygen demand (MVO2) can be enough stress in a sick heart to bring on angina.
Example : If a person is under a great deal of emotional stress, like being involved in a bank holdup, a plane crash or a fire, the adrenal medulla will release large quantities of epinephrine and some norepinephrine. Epinephrine has the effect of causing the heart rate to increase dramatically, blood vessels will constrict and the force of the heart's contraction will increase. Why, then, would stress be able to trigger angina ?
Answer : Epinephrine has the ability to vasoconstrict blood vessels throughout the body. It is also a potent hormone that drives up the heart rate (increases heart chronotrophy) and increases the strength of contraction (increases heart inotrophy). Anytime you increase the work of the heart by driving up the heart rate and strength of each contraction, you increase the myocardial oxygen demand (MVO2). In a sick heart, these stressors can bring on angina because the heart has reached its anginal threshold. The anginal threshold is that point at which the perfusion of the heart is no longer sufficient to supply enough oxygen for the intensity of work being demanded. The heart becomes hypoxemic and angina or chest pressure or pain signal the onset of heart ischemia.
Example : If a person is performing a great deal of physical work, like shoveling snow in the winter time, small muscle groups in the upper extremities will have to do a great deal of pushing, lifting and throwing. When people perform a lot of lifting and throwing, they will frequently Valsalva and hold their breath. Why would shoveling snow in the cold weather bring on an episode of angina pectoris ?
Answer : Whenever a person performs a Valsalva maneuver, the blood return to the heart is inhibited thus reducing filling volumes and ejection fractions. Also, the Valsalva deranges blood pressure and thus represents a derangement of vascular pressures - an important concept to remember when you recall that the heart receives its perfusion during diastole and depends on good ejection fractions and intravascular pressures for adequate perfusion. Additionally, upper extremity work (snow shoveling) represents a significantly higher work burden because the upper extremities generally have a lower absolute VO2max and upper extremity muscle mass is smaller. Therefore for any absolute work burden, the actual cost of performing the work will be higher for the upper extremities versus the energy required to do the same work by the lower extremities using a much larger muscle mass.
Therefore, anytime you increase heart rate and therefore increase MVO2 for the heart, you place it at risk for angina if CAD is present.
Example : If a person smokes a cigarette, we know that it causes the blood vessels to constrict because tobacco has a great deal of nicotine - a powerful vasoconstrictor. Why would a chronic smoker be more likely to suffer from angina than a non-smoker ?Answer : Nicotine is a powerful vasoconstrictor and therefore inhibits perfusion to any organ system. Plastic surgeons do not like to perform re-attachments or flaps or skin grafts on smokers on a smoking patient until they have stopped smoking for 2-4 weeks. Plastic surgeons correctly maintain that the blood supply to an extremity or to a flap or skin graft is jeapordized if the patient smokes. Additionally, it is well known that atherosclerotic processes are acclerated in smokers. The burdens of decreased perfusion due to nicotine and the decreased perfusion due to atherosclerotic plaque formation in the coronary vessels creates the poor perfusion conditions that lead to angina pectoris and eventually to a myocardial infarction.
A. Stable Angina
Onset due to :
Treatment Philosophy :
Onset due to :
|Verapamil (Calan, Isoptin)||Nifedipine (Procardia)|
|Diltiazem (Cardizem)||Bepridil (Bepadin, Vascor)|
|Felodipine (Plendil)||Isradipine (Dynacirc)|
Mechanisms of Action:
Side Effects : Headaches, flushing, peripheral edema, dizziness, swelling in the feet and legs, nausea, syncope, hypotension, tachycardia, bradycardia.
Medical Uses :
|Nitroglycerin (Nitro-Bid, Nitrostat, Nitro-Dur)|
|Isosorbide Dinitrate (Iso-Bid)|
|Erythrityl Tetranitrate (Cardilate)|
|Pentaerythritol Tetranitrate (Peritrate)|
Mechanisms of Action :
The nitrates basically cause vasodilation. How ?
They do this by activating guanylate cyclase which cleaves GTP (guanosine triphosphate) into cGMP. cGMP (a second messenger) activates a protein kinase which dephosphorylates myosin in smooth muscle. If myosin has no phosphate group to activate it, myosin cannot connect to actin and cause muscle contraction. Hence, myosin is essentially inactivated, and permissive vasodilation or relaxation of vessel tone occurs. The net effect is as follows :
Side Effects : Orthostatic Hypotension, Headaches, Dizziness, Vertigo, Flushing, Sweating
Medical Uses : To treat angina quickly.
The Nitroglycerin Paradigm : With the onset of angina, sit down and place one nitroglycerin tablet under the tongue (sublingual) and wait 3-5 minutes. If the angina has not subsided, take another tablet sublingually and wait 3-5 minutes. If the angina has not subsided, take a third tablet of nitroglycerin and call 911 for help. Notify the patient's physician immediately.
|Non-Selective Beta Blockers|
|Propranolol (Inderal)||Nadolol (Corgard)|
|Penbutolol (Levatol)||Sotalol (Betapace)|
|Pindolol (Visken)||Timolol (Blocarden)|
|Carteolol (Cartrol)||Carvedilol (Coreg)|
|Beta-1 Selective Beta Blockers|
|Atenolol (Tenorman)||Metoprolol (Lopressor)|
|Acebutolol (Sectral)||Betaxolol (Kerlone)|
|Bisoprolol (Zebeta)||Esmolol (Brevibloc)|
Mechanisms of Action :
Side Effects : Fatigue, hypotension, bradycardia, skin rashes, increased airway resistance and bronchoconstriction (blockade of beta-2 receptors thus inhibiting bronchodilation - beta blockers should be only cautiously given to patients with COPD), hypoglycemia (blockade of beta-2 receptors in liver thus preventing glycogenolysis - this becomes a problem for diabetics).
Medical Uses :
1. Beta blockers are used to prevent/suppress supraventricular tachydysrythmias such as :
2. Beta blockers are used to suppress the re-occurrence of ventricular dysrythmias such as :
General Clinical Considerations For All Of These Cardiac Medications For Physical Therapists To Remember :
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