Myocardial Infarction Treatment
Myocardial infarction is a major cardiac emergency. Currently myocardial infarction is well standardized in terms of therapeutic means.
It starts with pain treatment, and anti-ischemic treatment:
- Nitroglycerin (given sublingually, spray or intravenously)
- Aspirin in all patients (160-325 mg)
- Oxygen if the patient is hypoxic
- Atropine in case of sinus bradycardia (decreased heart rate below 60 beats per minute in adults and less than 80 beats per minute in children) and / or hypotension
- Cardio-respiratory resuscitation
- Procainamide should not be administred for ventricular extrasystoles prevention.
During prehospital care, thrombolysis is possible, given the existence of mobile coronary unit. Its benefits are increased reperfusion, reduced mortality, decreased size of infarction zone area. The first 60 minutes elapsed the from stroke onset are considered “the golden hour” of reperfusion (resumption of circulation to the infarction zone). The agents used are Streptokinase, tissue plasminogen activator, Urokinase.
Emergency treatment consists of morphine, oxygen (flow rate of 2 l / min), 325 mg Aspirin (unless it was given), and nitroglycerin (sublingual or perfusion).
If the patient shows no signs of haemodynamic deterioration and bradycardia, beta blockers are intravenously administered (metoprolol, atenolol).
Coronary Care Unit
- Aspirin in doses of 160-325mg / day
- Further fighting pain using common analgesics (metamizole sodium, vials 1g), opioid analgesics (morphine 20mg/1ml vials) in doses of 4-8mg intravenously, 5-15 mg at 2-8 minutes until the pain disappeares.
Beneficial effects of morfine : intense analgesic effect, reduces sympathetic tone, increase vagal tone, reduces anxiety, produces vasodilation.
Morphine contraindications: hypotension, bradycardia, inferior myocardial infarction, right ventricular infarction.Morphine side effects: hypotension, respiratory depression, nausea, vomiting.
- Oxygen therapy: 2-4 liters / minute, under the mask or nasal tube for 6-12 hours in patients with moderate hypoxemia. It is not indicated if the oxygen saturation is normal, because it can increase the peripheral vascular resistance.
- Nitrates and beta blockers can relieve pain through their coronary and anti-ischemic effect.
Cardioprotection by restoring coronary blood flow.
Cardioprotective measures include all pharmacological measures, especially thrombolysis, and non-pharmacological measures that aim for myocardial reperfusion. Myocardial reperfusion by thrombolysis is the most important measure that reduces mortality, improves ventricular function and limitates the infarct size . This measure will be continued in the coronary artery unit as early restoration of coronary blood flow (1-2 hours after onset), reduces the size of necrotic myocardium.
- Thrombolysis medication. Can be administed directly in the coronay arteries (only when coronary thrombosis occurs during an angiographic procedure) or intravenously. Streptokinase, tissue plasminogen activator are used.
A possible evolution of coronary thrombolysisis is reocclusion of the coronary artery (approximately 10% of cases). To reduce the risk, antiplatelet therapy is required (aspirin, clopidogrel), and antithrombotic agents (low molecular weight heparin). Antiplatelet therapy increases the success rate of reperfusion, prevents intraventricular thrombus formation, prevents deep vein thrombosis and pulmonary embolism.
The most important complication of thrombolytic therapy is bleeding (cerebral, digestive, etc.)
Absolute contraindications of thrombolysis: Stroke (any time in history), ischemic stroke, brain neoplasm, active internal bleeding, suspected aortic dissection.
- Percutaneous transluminal coronary angioplasty (PTCA procedure) is another important method of thrombolysis and reperfusion.
- Bypass surgery, is indicated in the following situations associated with myocardial infarction: PTCA procedure failure (with persistent pain or hemodynamic instability), PTCA risk procedure due to the coronary anatomy (left common trunk stenosis), coronary occlusion occurred after catheterization, cardiogenic shock.
Cardioprotection by decreasing myocardial oxygen consumption.
- Beta-blockers. Early treatment with beta blockers is associated with reduced mortality and reduced cardiac arrest risk by 15%. Their administration reduces heart rate and blood pressure decreasing myocardial oxygen consumption through these mechanisms. Beta-blockers indications: recurrent or persistent pain, ischemic tachyarrhythmias (atrial fibrillation with fast heart rate), myocardial infarction with or without ST-segment elevation, actually all patients without contraindications.
Beta-blockers contraindications: hypotension (systolic blood pressure <90 mmHg), bradycardia (heart rate <50 beats per minute), heart blocks.
- Nitrates. Nitroglycerin can be used in the first 24-48 hours in patients with acute myocardial infarction, congestive cardiac failure, persistent ischemia, hypertension. After 48 hours, will be administered to patients with recurrent angina, or pulmonary stasis. It is administrated intravenously , blood pressure monitoring is mandatory.
Nitroglycerin contraindications: hypotension, myocardial infarction of right ventricle.
- Angiotensin converting enzyme inhibitors have beneficial effects as it prevents ventricular remodeling after myocardial infarction, decrease the rate of occurrence of heart failure, reduce the risk of recurrence of myocardial infarction and reduce mortality. Are indicated in all patients with acute myocardial infarction, especially those with heart failure, diabetes mellitus, hypertension.
Contraindications: hypotension, pregnancy, renal insufficiency (creatinine> 3mg%)
- Calcium channel blockers. At the onset of myocardial infarction are not recommended, nifedipine increases mortality risk. It suddenly lowers blood pressure, followed by reduction of the coronary blood flow and tachycardia, with increased imbalance between intake and myocardial oxygen demand.
Verapamil and diltiazem can be used, but with caution (due to the negative inotropic effect) in patients in whom beta blockers are ineffective or contraindicated (asthma patients) and for heart rate control in patients with atrial fibrillation.
- Magnesium. Can be administered in case of a demonstrated magnesium deficiency , in episodes of torsades de pointes with QT interval prolongation, in doses of 1-2g IV, magnesium sulfate (10 ml vials, 20%), bolus for 5 minutes.
Physical and emotional rest. In uncomplicated myocardial infarction, absolute bed rest will not exceed 12 hours, a gradual resumption of physical activity is recommended, which takes into account age, physical capacity and condition. The first two days help from another person is recommended, including when washing and feeding. The following days the patient can wash his face on his own, can go to the toilet, and movement is allowed but only supervised, inside and outside the chamber (20-200 meters). After 5 to 7 days walking (200m), three times a day, climbing stairs are allowed, under supervision, and exercise testing before hospital discharge.
- Diet: light regime, hypo-caloric, salt restriction, foods rich in potassium
- Mild laxatives will be administered if needed, .
- Correction of anemia with packed red blood cells transfusions
- Treatment of infections
- Monitoring and keeping the blood pressure within normal values.