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Antianginal Therapy

Oct. 1, 1995
Angina pectoris can be a life-threatening emergency that re-quires the dental staff to be alert when responding to patients who report chest pains of more than two minutes in duration.

Angina pectoris can be a life-threatening emergency that re-quires the dental staff to be alert when responding to patients who report chest pains of more than two minutes in duration.

Cynthia R. Biron, RDH

Dental patients who present a history of angina pectoris may have an underlying disease which, if known, can provide the dental team with definitive information for the risk management of such medically compromised patients. Most of the patients have coronary artery disease (CAD) because of atherosclerotic luminal narrowing of coronary arteries. A table of the diseases that may underlie angina pectoris is on page 46.

The pain of an angina attack is because of lack of oxygenated blood perfusion of the myocardium. The patient usually describes the pain as substernal (demonstrated by placing the fist on the sternum), strangling and suffocating. Duration is three to eight minutes. The type of angina the patient has will be the determining factor in which antianginal agents are prescribed for him. Every diagnosed angina pectoris patient should have been prescribed a rapid-acting nitrate (nitroglycerine) to relieve the pain of an acute anginal attack.

The patient should bring this nitroglycerine with him to every dental appointment. Long acting nitrates are prescribed to prevent angina attacks and/or reduce their severity. Dipyridomole, beta-adrenergic blocking agents and the calcium channel blockers are also used in the prevention of angina attacks. Associated cardiovascular diseases may extend the patient`s list of medications to include antihypertensive, anticoagulant and antiplatelet drug therapy.

Three main types of angina pectoris

The three main types of angina pectoris are stable, unstable and variant. Each has more than one name, so it behooves the dental team to be familiar with all of them and their respective syndromes, as the patients will state the term given to them by their physicians. Being familiar with each term better prepares the dental team for risk management of the patient.

Stable angina

Stable angina is also called chronic, typical, classic or exertional angina, and in 90 percent of the cases it is caused by an underlying CAD. The anginal episode is precipitated by physical exertion, a high level of stress or exposure to cold temperatures and wind. All of these factors place an increased demand on the myocardium which, in turn, demands an increased amount of oxygenated blood. When the narrowed coronary arteries are unable to contain and deliver the volume of blood necessary for myocardial perfusion, there is deprivation of oxygenated blood in the myocardium (cardiac ischemia). The patient may be told he has ischemic heart disease (IHD), as so many of these patients view their nitroglycerine as a cure for chest pain in the same way they view aspirin as a cure for headache.

Avoidance of the precipitating factors and improvement in lifestyle coupled with antianginal drug therapy can slow the progression of underlying disease and improve the quality of life for these patients, but most eventually experience myocardial infarction and/or heart failure that results in death. If the onset of angina pectoris is at age 75, it is conceivable that antianginal drug therapy and a healthy lifestyle could postpone the inevitable to even age 90 or more. Long term nitrates, beta-adrenergic blockers and/or calcium channel blockers are used in the management of stable angina.

Unstable angina

Unstable angina is also called coronary insufficiency, preinfarction angina, premature myocardial infarction and intermediate coronary syndrome. Unstable angina is either the advancement of stable angina or a resulting condition from a myocardial infarction. Unstable anginal episodes can last 30 minutes or longer. If anginal episodes are caused by little or no exertion or progressively worsening from a stable status, the condition is redefined as unstable angina when the symptoms are categorized by three subsets. The subsets below are defined by Dr. Stanley Malamed in Medical Emergencies in the Dental Office.

- Group I angina - upon effort - recent (four weeks)

- Group II angina - upon exertion - progressing pattern of incomplete relief from nitroglycerine

- Group III angina - at rest - 15 minutes plus.

Stress testing and radionuclide imaging are non-invasive techniques used to evaluate patients with stable angina, but disabling symptoms call for definitive diagnosis through catheterization. There is a higher incidence of left-main coronary artery disease in unstable angina patients and cardiologists can diagnose and to a degree, treat these arteries with catheterizations for angioplasty and coronary artery bypass grafts are determined.

More aggressive antianginal drug therapy is implemented for the unstable angina patient in an attempt to improve myocardial perfusion and function.

Therapy often includes anticoagulant or antiplatelet therapy as studies have shown a reduction in mortality in older patients on such therapy.

Verapamil has been cited as the calcium channel blocking agent of choice for unstable angina. Beta-adrenergic blockers such as propranolol reduce the number and duration of episodes in unstable angina patients.

It is thought that several mechanisms of action are responsible for the reduction in episodes. Propranolol`s inotropic and chronotropic effects and blockade of reflex tachycardia caused by nitrates are theorized as reasons. But beta-adrenergic blockers are used judiciously as a study conducted by Kern, Ganz and Harowitz showed potentiation of coronary vasoconstriction by beta adrenergic blockade in patients with coronary artery disease. The use of beta adrenergic blockers in CAD patients requires close monitoring.

Variant angina

Variant angina is less common than both stable and unstable angina. Other terms are Printzmetal`s, dynamic, atypical, spasmodic or vasoplastic angina. It is more common in women under 50, and women overall have a lower incidence of angina pectoris or heart disease in general in the premenopausal years, due to circulating estradiol.

Exceptions to this finding are related to endocrine disorders, hereditary heart disease and lifestyles that predispose women to hypertension and hypercholesterolemia.

Variant angina episodes are more prevalent when the patient is at rest than active or stressed. This is the type of anginal episode that wakes a person from sleep as catacholamine levels that are elevated during the night bring on the coronary artery spasms. The spasm of the coronary artery temporarily occludes its walls preventing blood flow to the myocardium.

The vasodilating properties of nitroglycerine are usually effective in eliminating the symptoms, but the duration of the variant angina attack could be longer than the three-to-eight minute attack experienced by the patient with stable angina. In the dental office, both the unstable and variant anginal episodes can be most upsetting as the duration of the attacks signal a concern that it could be a myocardial infarction.

All of the nitrates have the capability of relaxing vascular smooth muscle to produce vasodilation. There is redistribution of blood flow along collateral vessels, which improves profusion of the myocardium. Overall, the blood pressure is reduced, but not to the degree of compromising perfusion of the myocardium. The nitrates that are prescribed to patients for acute anginal episodes are sublingual and transmucosal tablets and translingual spray, all of which have an onset that varies from one to two minutes.

Amyl nitrate

The fastest acting nitrate that is available is amyl nitrite with an onset of 10 to 30 seconds. Amyl nitrite is available as an inhalant in a vaporole that is crushed at the time of administration. It has a profound potency that can effect even the emergency team that is near the patient.

Usually, amyl nitrite is reserved for medical emergency kits. It is such a profound vasodilator that it can cause a severe drop in blood pressure that could lead to hypotensive shock. Nitroglycerine tablets have a limited shelf life once the bottle has been opened. The tablets must be kept in their original sealed, tinted bottle, protected from moisture. An opened bottle should be discarded in six months and replaced with a new unopened supply.

Often, the tablets produce a burning or tingling sensation at the location of sublingual placement. Although some people think that the sensation is the true indicator of drug potency and freshness, the newer stable preparations do not all produce that sensation, and some older patients never have experienced it. Most of the patients using sublingual nitroglycerine experience a headache during the initial vasodilating effects. In about 50 percent of the patients, the headache is persistent for several hours.

Nitroglycerine in the sublingual spray form is packaged in an aerosol container and more stable for an extended shelf life. This is an important factor for emergency kits. The onset of the spray, however, is right at two minutes whereas the sublingual tablet can have an onset as early as one minute. In a medical emergency, one minute can seem like a long time if it is the first episode of chest pain and the effects of nitroglycerine are providing the differential diagnosis between angina and myocardial infarction.

Long term use of nitroglycerine can be provided through sustained-release oral tablets (six to 12 hours), topical ointment (12 hours), and transdermal patches (24 hours). Long term use of nitroglycerine can cause patients to develop a tolerance to antianginal effects. Increasing the dosage does not provide efficacy. Only withdrawal from nitrates will restore the antianginal effects of the drug. Nitrate withdrawal of 10 to 12 hours will be effective for restoring efficacy.

When patients develop a tolerance to nitrates the on and off 12-hour alternating schedule is used. Short term use of nitrates are less likely to be associated with tolerance. The transmucosal preparations which have an efficacy duration of three to five hours are also less likely to be associated with tolerance. They are placed in the mucobuccal fold for transmucosal uptake of the drug.

Beta-adrenergic blocking agents

The four drugs in this category that are most commonly used in the treatment of angina are nadolol (Congard), propranolol (Inderal), atenolol (Tenormin) and metoprolol (Lopressor). The beta blockade lowers the heart rate and blood pressure and reduces the cardiac output. It is most useful in patients who demonstrate that sympathetic activity has adverse effects on cardiac function. In damaged hearts, where sympathetic activity is mandatory for cardiac function, beta blockers are contraindicated.

The most important factor for the dental team to remember is that patients taking these drugs must not receive concomitant administration of any vasoconstrictors, in local anesthesia or otherwise, as the patient could undergo a hypertensive crisis.

A 48-hour withdrawal from beta-adrenergic blockers before general anesthesia may be required. The depression of the myocardium during anesthesia could increase the chances of cardiac arrest, and difficulty in starting the heart beat has been reported.

Calcium channel blockers

The three drugs in this category that are most commonly used in the treatment of angina are verapamil (Colon, Isoptin), diltiazem (Cardizem), and nifedipine (Procardia, Adalat). These agents inhibit the movement of calcium ions through cardiac cells allowing reduction in contractility of the smooth muscle of the myocardium and the vascular system.

The drugs selectively affect pacemaker tissues and are very frequently used an antidysrhythmic agents. These drugs lower blood pressure and nifedipine (Procardia) is now used in medical emergencies to treat hypertensive crisis. Biting the capsule open and swallowing the contents provides the fastest absorption, and it is the method of administration in emergency management of hypertensive crisis. Nifedipine (Procardia) has become well known to the dental team from its adverse effect of causing gingival hyperplasia.

Preventing anginal episodes

Consulting the patients` physician and employing stress reduction protocols are mandatory for the angina pectoris patient. The cause of the angina episode is myocardial ischemia. Increasing blood oxygen concentration ensures adequate perfusion of the myocardium. During routine treatment, these patients should be provided with supplemental oxygen using a nasal cannula or nasal hoot at a two to four liter flow rate. Before a tooth extraction or oral surgery procedure, sublingual placement of nitroglycerine should be administered in addition to supplemental oxygen.

Emergency management of chest pain

Not all chest pain is caused by cardiac conditions, but a first time occurrence of chest pain that lasts three minutes or longer requires the expertise of emergency medical personnel and ambulance transport to the hospital.

Never transport a patient with chest pain to the hospital in a passenger car. Every additional bodily movement exerted by the patient increases the demand on an already taxed myocardium. Even when chest pain has been relieved by nitroglycerine, the patient must be transported by EMS if it is a first time episode.

Patients with chest pain of two or more minutes should be provided with high concentrations of supplemental oxygen (90 percent). The proper delivery system is the non-rebreather bag mask with a 10 to 12 liter flow rate. Nasal cannulas and nasal hoods do not provide high enough concentrations of oxygen. Demand valve resuscitators are not well tolerated by conscious patients with chest pain.

If a patient has their own nitroglycerine, they will take it themselves very quickly. Do not administer nitroglycerine to a patient unless his diastolic blood pressure is elevated. If any nitrate is given to a patient with a fallen diastolic blood pressure, the patient could go into cardiac shock or cardiac arrest.

The one thing the dental team can do that will lessen the extent of cardiac ischemia is provide the patient with high concentrations of supplemental oxygen. Morphine outside of a hospital setting is contraindicated by all EMS professionals.

Nitrous oxide or synthetic opioids are pain relievers that are recommended for chest pain outside of a hospital setting. A clip chart is provided for quick access in managing chest pain. You might want to cut it out and place it on an office bulletin board.

Check the expiration date on the emergency supply of nitroglycerine to make sure it is fresh, check the oxygen tank, and set up the non-rebreather bag mask and be familiar it. We owe it to our patients to be prepared for a life-threatening emergency.

References are available upon request from the author.

Cynthia R. Biron, RDH, is chair of the dental hygiene program at Tallahassee Community College. She is also a certified emergency medical technician.

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