Case Studies

Case 5: Myocardial infarction

A 60-year-old man is brought to A&E with central crushing chest pain. He has been in pain for several hours and it was not relieved by nitroglycerin. The man was feeling nauseous and was very anxious. His blood pressure was 140/75. An ECG revealed ST segment elevation, pathological Q waves and inversion of the T wave in leads II, III and aVF. A diagnosis of acute inferior myocardial infarction (MI) was made.

• (a) What drugs should be administered immediately to this patient?

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  Correct answer:

  Aspirin is given to reduce further platelet aggregation. Oxygen is administered, and intravenous diamorphine together with an antiemetic (e.g. metoclopramide) is given to reduce the pain. A nitrate (e.g. glyceryl trinitrate, isosorbide dinitrate) may reduce the work of the heart and help to control the ischaemic pain. A beta-blocker (e.g. propranolol) should be given. Beta-Blockers reduce the rate and the oxygen demand of the heart and decrease ventricular wall stress by lowering the afterload. When given acutely, beta-blockers reduce ischaemia and infarct size. They also suppress arrhythmias (Chapter 17).

  Revascularization. A thrombolytic agent (e.g. streptokinase, tissue plasminogen activator [tPA], Chapter 19) should be administered to dissolve the thrombus and restore patency of the occluded artery. Clinical trials have shown that in MI with ST segment elevation, thrombolytic drugs reduce mortality by 25%. It is important that the drug is given as soon as possible, ideally within 1 h, although significant reductions in mortality occur up to 12 h from the onset of symptoms. tPA, reteplase and tenecteplase are more fibrin specific than streptokinase, and intravenous heparin is used for 48–72 h as adjunctive therapy to prevent re-thrombosis. Increasingly, primary percutaneous intervention (PCI), to mechanically disrupt the occlusion within the culprit epicardial coronary artery, is replacing pharmacological thrombolysis (see Chapter 19).

• (b) What contraindications should you consider?

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  Correct answer:

  The drugs cited above have the following contraindications:

  Aspirin: allergy, history of active peptic ulceration.

  Beta-Blocker: left ventricular failure.

  Thrombolytics: recent haemorrhage, cerebrovascular disease (e.g. stroke), uncontrolled hypertension, and in the case of streptokinase, previous allergic reaction. Antibodies to streptokinase develop and reduce its effectiveness. For this reason it should not be used beyond 4 days of first administration

• (c) What drugs would you prescribe for this patient to take long-term when he returns home?

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  Correct answer:

  The long-term management of this patient involves the use of a number of drugs. Glyceryl trinitrate for anginal pain. To prevent platelet aggregation, aspirin should be given together with Clopidogrel. Warfarin is occasionally used in patients with extensive myocardial infarction or evidence of blood clots in the left ventricle. Aβ - blocker should be prescribed because long-term use has been shown to reduce mortality, recurrent MI and sudden death by about 25%. Treatment with an ACE-inhibitor should be started within 24 hours and continued when the patient is discharged, especially if there is evidence of left ventricular dysfunction. ACE-inhibitors reduce afterload and improve ejection fraction. They also reduce ventricular remodelling and infarct expansion, actions that reduce mortality, the incidence of heart failure, and further MIs. The patient should be given a statin (Chapter 20) because they have been shown to reduce the incidence of coronary events.