The signs and symptoms of a heart attack (myocardial infarction) often leads to panic, both on the part of the person having the heart attack and those around them. However, early intervention, even by a person with basic emergency care knowledge, can save the life of the heart attack patient. Recognizing the early features of a heart attack and immediately calling for emergency medical services can ensure that that early treatment will reduce or even prevent the damage to the heart muscle.
Emergency Care (Pre-Hospital Care)
Chest pain should never be ignored since it might herald a heart attack. If attended to at the earliest possible stage, it can save the person’s life and prevent extensive damage to the heart muscle. A person who suspects that he/she is having a heart attack or any individual witnessing such an event should immediately call 911 or the local emergency number. Cardiopulmonary resuscitation (CPR) should be started immediately after calling 911 in case the person is unconscious and unresponsive. The patient should be transported to the hospital in an ambulance.
A type of arrhythmia known as ventricular fibrillation (VF) is the most common cause of death in the initial stages of myocardial infarction. This is only one of the several heart attack complications that arises within minutes to hours that can cause death. Immediate ECG monitoring and defibrillation in case of VF along with rapid transport of the patient to the hospital for immediate reperfusion (restoring blood flow) of the affected coronary artery can help to save a life.
Immediate care may be given by emergency medical personnel in a suspected MI. This includes :
- Aspirin (160 to 325 mg) should be given as soon as possible and should be chewed), unless there are contraindications such as active or recent gastrointestinal bleeding or an allergy to aspirin. It helps to prevent blood from clotting.
- Oxygen administration after monitoring oxygen saturation using a pulse oximeter.
- Establishing intravenous (IV) access.
- Glyceryl trinitrate (GTN) sublingually (under the tongue) or by spray may be used as a first-aid measure to help in pain relief. Nitroglycerin acts by dilating the blood vessels.
- Administration of IV morphine for persistent and severe pain, plus metoclopramide, an antiemetic.
- If a 12-lead ECG can be obtained which shows ST elevation as discuss under diagnosing a heart attack, then the receiving hospital should be notified of it.
- Fibrinolytic checklist should be started.
- Pre-hospital fibrinolysis may be advisable if the time from seeking aid to estimated arrival time at the hospital is likely to be more than 30 minutes. Use of intravenous bolus of reteplase or tenecteplase is recommended in such cases rather than an IV infusion.
- Thorough history, with special attention to cardiovascular history.
- Physical examination.
- Oxygen administration.
- Establishing IV access.
- Blood tests for CBC, glucose, lipids, and cardiac enzymes.
- Chest x-ray.
- Continuous monitoring of heart rhythm.
- Chewable aspirin 160 to 325 mg, if not already administered.
- Glyceryl trinitrate (GTN) under the tongue or as spray may be given to help relieve pain. Subsequently, it may be given intravenously to relieve recurrent or persistent chest pain and for treatment of left ventricular failure. Use of nitroglycerin should be avoided in patients with inferior MI and right ventricular infarction, blood pressure less than 90 mm Hg, heart rate less than 50 per minute, or a heart rate more than 100 per minute. It should also be avoided in a patient known to have taken a phosphodiesterase inhibitor such as sildenafil (Viagra) or vardenafil within the last 24 hours or tadalafil within 48 hours since a severe fall in blood pressure may occur with use of GTN.
- IV morphine plus metoclopramide. Morphine may be repeated every 5 to 15 minutes if pain relief is not adequate. The major contraindication to use of morphine is hypotension.
- Complete fibrinolytic checklist and check for contraindications to fibrinolytic therapy.
- Defibrillation if ventricular fibrillation (VF) develops.
- Other arrhythmias such as atrial tachycardia, flutter, or fibrillation should be treated if present.
- A 12-lead ECG should be performed and analyzed by an experienced physician within 10 minutes of arrival in the ED so as to identify patients with STEMI. In case of STEMI, the decision regarding further treatment should be made within the next 10 minutes. These patients need rapid reperfusion therapy, which may be done either by fibrinolytics or primary percutaneous coronary intervention (PCI). The door-to drug time should ideally be within 30 minutes and the door-to-balloon time 90 minutes to achieve optimum results. Reducing the door-to-balloon time further significantly reduces cardiac damage and death associated with MI.
- Coronary thrombolysis or fibrinolysis done as soon as possible helps in coronary reperfusion, thus improving chances of survival and preservation of left ventricular function. Fibrinolytics give best results when used within 2 hours of onset of symptoms and are usually not started after 12 hours except in certain cases, such as persistent chest pain and ST-segment elevation of more than 1 mm in 2 or more contiguous chest or limb leads.
Apart from aspirin and nitrates used in emergency care, the following medication may also be necessary :
- Beta blockers. IV atenolol or metoprolol in the acute stage may reduce the risk of cardiac rupture. However, they cannot be used in patients with heart failure or bradycardia (low heart rate). Beta-blockers may be continued long term and may be useful in lowering the blood pressure in hypertensive patients.
- Anticoagulants (blood thinners). Heparin may be used in immobile patients who are at risk of venous thrombosis. Warfarin may be continued long-term in patients at risk of systemic thromboembolism. Clopidogrel may also be used on a long-term basis to prevent blood from clotting.
- Angiotensin converting enzyme (ACE) inhibitors. Drugs such as lisinopril, captopril, and enalapril may help to prevent or reduce left ventricular dilatation but should be used with caution since they may drastically lower the blood pressure. These act by dilating the blood vessels.
- Statins. Drugs such as atorvastatin, lovastatin, and simvastatin help to lower cholesterol.
- Gastrointestinal disruptions like constipation and stress ulcers may develop. It is important to avoid constipation and straining at stool. Stool softeners may be prescribed if necessary. Stress ulcers may be prevented by use of oral sucralfate, famotidine, or ranitidine.
Contraindications to fibrinolytic therapy include :
- Active internal bleeding
- Previous brain hemorrhage
- Recent trauma
- Recent surgery
- History of peptic ulcer
- Severe diabetic retinopathy
- Current menstruation
Streptokinase and alteplase are given by IV infusion. Reteplase and tenecteplase can be given as bolus injection. Maximum benefit is obtained when fibrinolytic therapy is started at the earliest, ideally within 1 hour of onset of symptoms. Tenecteplase should be given within 6 hours. If streptokinase, alteplase, or reteplase is used, treatment should be started within 12 hours. If streptokinase is used once in MI, it cannot be used again in future infarctions because of antibody formation.
Indications for fibrinolytic therapy
- The patient is seen within 12 hours of chest pain.
- Presentation within 12 to 24 hours in case of persistent chest pain and/or ST elevation.
- ST elevation more than 1 mm in 2 contiguous limb leads or more than 2 mm in contiguous chest leads.
- Posterior MI.
- New onset left bundle branch block.
ST segment depression or enzymatic changes are not indications for fibrinolytic therapy.
Percutaneous Transluminal Coronary Angioplasty (PTCA)
A coronary angiogram is initially done to identify the site of clot. A balloon angiography is then done whereby the artery is dilated by inflating a tiny balloon within the artery. A stent, which is a tiny wire mesh tube, may then be placed within the artery to prevent the walls from collapsing. Medicated stents may also be used. These are known as drug-eluting stents since they continuously release medicine into the artery which help to prevent re-blocking or re-stenosis of the arteries. Primary coronary intervention (PCI) may be done during initial management of MI. It is often regarded as superior to fibrinolysis. PCI may also be done in case of persistent coronary occlusion despite fibrinolytic therapy.
Coronary Artery Bypass Graft (CABG)
CABG is a major surgery which may take about 4 hours to perform. The blocked arteries may be bypassed by taking a graft of another blood vessel and thus restoring blood flow to the heart. A vein from the leg (saphenous vein) is most commonly used. Chest wall arteries, particularly the left internal mammary artery, are also used as bypass grafts.
CABG surgery is usually indicated in :
- Patients in whom fibrinolysis or angioplasty is not appropriate.
- Previous PTCA with stent placement has not given the desired result.
- Re-stenosis following PTCA and stent placement.
- Patients with left main artery block.
- Multiple artery block, usually 3 or more.
- Severe ventricular dysfunction.
- Patients with diabetes mellitus.