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Angina Pectoris and Acute Myocardial Infarction

Angina Pectoris and Acute Myocardial Infarction

Medical Emergencies

Angina pectoris is derived from Latin words, Angina describing a spasmodic, cramp-like, choking feeling or suffocating pain and Pectoris meaning chest. Myocardial infarction (Heart attack) is a clinical syndrome characterised by severe and prolonged substernal pain caused by cardiac ischemia and damage to myocardial cells.

Angina Pectoris

  • Stable angina : There is transient, episodic chest discomfort, typically predictable and reproducible. It is provoked by physical or psychological stress and resolves spontaneously on taking rest or nitroglycerin. The frequency of attacks is constant over time.

  • Variant angina (Prinzmetal's, Atypical or Vasospastic angina) : More likely to occur at rest and at odd times during the day or night. It is caused by coronary artery spasm and often associated with dysrhythmias or conduction defects.

  • Unstable angina (Preinfarction or Crescendo angina, Intermediate Coronary Syndrome, Premature or Impending MI, Coronary Insufficiency) : It presents with at least one of the following features :

    1. Occurs at rest or with minimal exertion, usually lasting more than 20 minutes (if not interrupted by nitroglycerin).
    2. Severe and described as frank pain and of new onset (i.e, within one month).
    3. Occurs with a crescendo pattern (i.e, more severe, prolonged or frequent than previous attack).

Myocardial Infarction

  • STEMI (ST-segment Elevation acute MI) : The ST interval in ECG is prolonged in at least two contiguous leads, usually have complete occlusion of an epicardial coronary artery.
  • NSTEMI (Non-ST Elevation acute MI) : Often results from incomplete occlusion or spontaneous lysis of the thrombus and is associated with a higher incidence of reinfarction and recurrent ischemia.

Clinical Manifestations

  • Chest Discomfort :

    • Angina pectoris : Squeezing, bursting, pressing, tightness, heaviness, burning, choking, or crushing.
    • Myocardial Infarction : Painful or intolerable pain described as intense sensation, much like a pressure or weight on the chest or deep ache within the chest.

  • Location : Substernal, middle or just left to the mid-sternal region.

  • Radiation : Ache, numbness or tingling discomfort radiates to the left shoulder and medial aspect of left arm (following distribution of the ulnar nerve), or sometimes, a constricting sensation to the left side of neck and mandible.

  • Duration : Anginal pain is almost always brief, while MI pain may last for 30 minutes to several hours, if untreated.

  • Response to medication : Anginal pain is relieved within 2-4 minutes after administration of nitroglycerin, while MI pain is commonly managed through administration of opioid analgesics such as morphine or nitrous oxide and oxygen.

  • Patients with angina may sit, lie or stand still, to avoid any activity that would increase their discomfort, while patients with MI are frequently quite restless, moving around in a futile attempt to find a more comfortable position.

Differential Diagnosis

  • Musculoskeletal pain

    • Results from muscle strain after exercise or physical exertion.
    • Normally localised and does not radiate.
    • Breathing and movement increases the pain, while it is relieved by application of heat or mild analgesic.

  • Pericarditis

    • Occurs in the mid-sternum and described as oppressive.
    • Aggravates on breathing and swallowing.
    • Relieved when the patient bends forward from the waist.
    • Associated with fever before the onset of pain.

  • Esophagitis (with or without pain)

    • Substernal or epigastric burning pain.
    • Precipitated by eating or lying down after meal.
    • Relieved by antacids.
    • Often associated acid reflux into mouth.

  • Pulmonary Embolism

    • Sudden, severe chest pain.
    • Commonly associated with coughing up of blood-tinged sputum.

  • Dissecting aortic aneurysm

    • Sudden, acute, severe chest pain, often greatest at onset.
    • Spreads up and down the chest and back over a period of hours.
    • May lead rapidly to death.

  • Acute indigestion and Intestinal gas

    • Sharp and knifelike.
    • Increases in intensity with breathing.

Management

Step 1 : Terminate all dental treatment and activate the medical emergency services.

Step 2 : Position the patient in semi-reclined position.

Step 3 : Assess Circulation-Airway-Breathing and monitor vital signs (every 5 minutes).

Step 4 : Definitive Care

  • Administer Nitroglycerin tablet (sublingual) or spray (transmucosal)

    • Indicated only when the systolic blood pressure is at least 90mm Hg or diastolic 50mm Hg.
    • Nitroglycerin spray : One or two metered sprays are recommended initially (Not more than three metered doses within a period of 15 minutes).
    • Nitroglycerin tablets (0.3-0.6 mg) : Every 5 minutes as required (Not more than three doses).
    • If the discomfort is relieved after first or second dose of nitroglycerin : Assume angina pectoris is in progress, slowly taper oxygen over 5 minutes and modify dental treatment to prevent recurrence.
    • If the discomfort is relieved after third dose of nitroglycerin : Refer the patient for medical evaluation before further dental treatment.

  • Administer Oxygen : 4-6 L/min through a nasal cannula or nasal hood.

  • If the chest pain is not relieved after 3 doses of nitroglycerin, assume Acute Myocardial Infarction is in progress.

    • Administer Aspirin (325 mg orally, chewed and swallowed) : Recommended for all patients with suspected acute MI or unstable angina, unless there is known aspirin allergy or active gastrointestinal hemorrhage.
    • Start IV line with drip of a crystalloid solution (5% dextrose) at 30 ml/hr.
    • Administer Morphine sulfate (2-5 mg IV every 5-30 minutes), if the pain persists and there is severe discomfort.
    • *Morphine should not be readministered if the respiratory rate is less than 12 breaths per minute or the blood pressure falls below 90mm Hg(systolic) or 50mm Hg(diastolic).

Step 5 : Transport to emergency care facility : In case myocardial infarction is suspected or when the discomfort is not relieved after 20 minutes of appropriate therapy.

  • A 50-50 concentration of Nitrous oxide and Oxygen can be administered through nasal hood or full-face mask during transport. It provides the patient with a gaseous analgesic, that has little effect on blood pressure and also an enriched source of oxygen (50% vs 21% in atmospheric air).

Points to Note

  • Patients with unstable angina represents ASA physical status 4 and should not undergo elective dental treatment. Stable angina represents an ASA 3 risk.
  • The American Heart Association recommends that a patient with previously unrecognised CAD should seek medical assistance if suspicious chest pain persists for 2 minutes or longer.
  • Elective dental care or any minimally invasive procedure should be avoided for at least 6 months after MI. In patients with MI, even the emergency dental treatment should be undertaken only in cases where medications have been ineffective and a controlled environment such as hospital setting is available.
  • In STEMI and NSTEMI, the ischemia is severe enough to cause damage to the myocardium with release of cardiac bio-markers (Troponin T, Troponin I, or Creatinine Kinase-MB) into the bloodstream.
  • Levine sign : Universal sign of ischemic chest pain, wherein the patient holds a clenched fist over the chest while describing the pain or during MI.
  • A high percentage of MI occur in the early morning, commonly between 6 AM and noon, perhaps associated with circadian elevations in plasma catecholamines and cortisol and increases in platelet aggregability.
  • Nitrates in all forms are contraindicated in patients with initial systolic blood pressure less than 90mm Hg or less than 30mm Hg below their baseline and when patients have taken a phosphodiesterase-5 (PDE-5) inhibitor within 24 hours (48 hrs for tadalafil).
  • Nitroglycerin spray is preferred over sublingual tablets in the dental office, because of the relative instability of the tablets.
  • Naloxane, an opioid antagonist, should be available whenever opioids are administered.
  • If Nitroglycerin is unavailable, or proves ineffective in terminating an episode of chest pain, calcium-channel blocker such as Nifedipine, Verapamil or Diltiazem can be administered.

References

  • Medical Emergencies in the Dental Practice (7th Edition), Stanley F. Malamed, Daniel L Orr II, Mosby Elsevier.
  • Contemporary Oral and Maxillofacial Surgery (6th Edition), James R Hupp, Edward Ellis III, Myron R Tucker, Mosby Elsevier.

*This article is an excerpt from the above mentioned books and Medical Sutras does not make any ownership or affiliation claims.