Antianginal Drugs – Several considerations need to be addressed when treating dental patients with coronary artery disease (CAD) to prevent recurrence of angina or infarction by giving them antianginal drugs. The determination of vital signs such as blood pressure, pulse rate and rhythm prior to dental care is essential. Patients with CAD are at increased risk of demand-related ischemia with increased heart rate and blood pressure. Anxiety can increase the heart rate and blood pressure and can provoke angina or ischaemia. So a dentist must take care of following points:
In patients with CAD, dental care should be provided in the late morning or the early afternoon due to the influence of cicardian variation on the triggering of acute coronary events between 6 AM and noon. This may be due to sympathetic nervous system activation and an increased coagulative state. Medications like antianginal drugs designed to prevent these events, such as beta blockers, aspirin, and antihypertensives should be continued.
Patients of angina pectoris must be advised to keep sublingual tablet of nitroglycerine or isosorbide mononitrate and similar antianginal drugs with him so that same may be used to abort the acute attack if precipitated. Fortunately risk is low during out patient dental procedures. Depending on level of anticipated stress premedication with antianginal drugs (benzodiazepines) and/or inhalation nitrous oxide may be employed to reduce the anxiety.
The use of xylocaine+ adrenaline injection or adrenaline-impregnated gingival retraction cord is contraindicated in patients taking propranolol as an antianginal drugs. Elective dental procedures especially those requiring general anaesthesia should be avoided for at least 4 weeks following an acute myocardial infarction as there is small risk of recurrent events. Since antianginal drugs like beta blockers and calcium channel blockers are used for prophylaxis of angina pectoris, all those precautions should be taken for these antianginal drugs.
Angina pectoris is a clinical condition. It occurs due to imbalance between the oxygen supply and oxygen demand. It may be angina of effort (or exertional or classical angina), variant (Prinzmetal’s) angina (occurs even during rest), and unstable (crescendo or preinfarction) angina (occurs with minimal exertion). To abort or terminate an acute attack of classical or variant angina, sublingual glyceryl trinitrate or isosorbide dinitrate is taken on ‘as and when’ required basis.
For chronic prophylaxis, generally one agent from beta blocker or nitrates or calcium channel blocker group is used initially. When antianginal drugs fails to provide adequate relief in tolerated doses, two or three drugs may be fried concurrently. For chronic prophylaxis of classical angina, a beta blocker may be combined either with nitrate or dihydropyridine (nifedipine). The advantages of such a combination are:
- Blocking of nitrate induced tachycardia by beta blocker or dihydropyridine
- Counteracting the tendency of beta blocker to cause ventricular dilatation by nitrate or dihydropyridine
- Opposing the tendency of beta blocker to reduce total coronary flow by nitrate or dihydropyridine.
For chronic prophylaxis of severe variant angina, nitrates are used in combination with calcium channel blockers. Such combination of antianginal drugs may decrease cardiac work to an extent not possible with either drug alone. For chronic prophylaxis of most severe and resistant cases of classical angina, combined use of all the three classes is indicated. Such a combination will lead to supradditive effect due to difference in their primary mechanism of action.
Beta blockers antianginal drugs are not used in combination with verapamil or diltiazem because such a combination will have marked depressant effects on SA and AV node. Nitrates primarily decrease preload. Calcium channel blockers mainly reduce after load. Due to direct action on heart, beta blockers decrease cardiac work.