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Myocardial Infarction: Difference between revisions
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Rapid revascularisation is essential to minimize the impact of the myocardial infarction and thereby reduce mortality. In the first hours after symptom onset the amount of salvageable myocardium by reperfusion is greatest. Revascularisation can be achieved by fibrinolysis or PCI. | Rapid revascularisation is essential to minimize the impact of the myocardial infarction and thereby reduce mortality. In the first hours after symptom onset the amount of salvageable myocardium by reperfusion is greatest. Revascularisation can be achieved by fibrinolysis or PCI. | ||
PCI is, if available, the preferred revascularisation method for patients with STEMI. | |||
But not all hospitals are qualified to perform PCI and therefore fibrinolysis is still used. There are however some circumstances in which transfer to a PCI qualified hospital is essential: | |||
* Patients with contraindications for fibrinolysis as active bleedings, recent dental surgery, past history of intracranial bleeding. | |||
* Patients with cardiogenic shock, severe heart failure and/or pulmonary oedema complicating the myocardial infarction. | |||
Or when PCI has a better outcome: | |||
* Patients who present three hours to four hours after the onset of the symptoms. | |||
* Patients with a non diagnostic ECG or a atypical history a coronary angiography with the ability to perform a PCI is preferred. | |||
===Fibrinolysis=== | |||
Fibrinolytics like streptokinase stimulate the conversion of plasminogen to plasmin. Plasmin demolishes fibrin which is an important constituent of the thrombus. Fibrinolytics are most effective the first hours after the onset of symptoms, after twelve hours the outcome will not improve. Because re occlusion after fibrinolysis is possible patients should be transferred to a PCI qualified hospital once fibrinolysis is done. | |||
===Percutaneous Coronary Intervention (PCI)=== | |||
The procedure of PCI starts off as a coronary angiography (see CAG). When the stenosis is visualized a catheter with an inflatable balloon will be brought at the site of the stenosis. Inflation of the balloon within the coronary artery will crush the atherosclerosis and eliminate the stenosis. To prevent that the effect of the balloon is only temporarily a stent is positioned at the site of the stenosis. To reduce the risk of coronary artery stent thrombosis antiplatelet therapy should be given. | |||
===Coronary Artery Bypass Graft=== | |||
When the coronary arteries contain too many or too severe stenoses for PCI a coronary artery bypass graft (CABG) is indicated. Especially when the stenoses are located proximally of the three major coronary arteries, causing occlusion of many ramifications and high risk of severe myocardial damage. | |||
CABG does not eliminate the stenosis like PCI does. Using the internal thoracic arteries or the saphenous veins from the legs a bypass is made around the stenosis. The bypass originates from the aorta and terminates directly after the stenosis. Thereby restoring the blood supply to the ramifications. A bypass can be single or multiple, multiple meaning that there are several coronary arteries bypassed using the same bypass. | |||
Major surgery is not preferable in patients with STEMI, but CABG is inevitable when fibrinolysis and/or PCI failed or when the patient develops cardiogenic shock, life threatening ventricular arrhymthmias or three vessel disease. | |||
===Medication to start after MI=== | |||
β blockers lower heart rate and blood pressure, this decreases the oxygen demand of the heart. | |||
Nitrates dilatate the coronary arteries so the heart receives more oxygenated blood. Anticoagulants reduce the risk of development of a thrombus in the coronary arteries. | |||
Statins: | |||
Apart from starting medication the patient needs to minimize any present risk factors like smoking, overweight and drinking alcohol. | |||
===Non ST elevated Myocardial Infarct=== | |||
Initial treatment in NSTEMI is to reduce ischemia, stabilize the hemodynamic status, make serial ECG and to repeat measurements of the cardiac markers. Depending on the early risk stratification a choice has to be made between early invasive therapy or conservative therapy with medicines. | |||
Early risk stratification is helpful to identify patients at high risk who need a more aggressive therapeutic approach to prevent further ischemic events. | |||
* Age ≥65 years | |||
* Presence of at least three risk factors for coronary heart disease (hypertension, diabetes, dyslipidemia, smoking, or positive family history of early MI) | |||
* Prior coronary stenosis of ≥50 percent | |||
* Presence of ST segment deviation on admission ECG | |||
* At least two anginal episodes in prior 24 hours | |||
* Elevated serum cardiac biomarkers | |||
Patients with a score of 0 to 1 are at low risk, score 2 to 3 are at intermediate risk, score 4 to 6 are at high risk. | |||
===Conservative Therapy=== | |||
The main objective of in hospital conservative therapy is to relieve ischemic pain by intensifying medical therapy with aspirin and clopidogrel orally and nitro-glycerine, heparin and a beta blocker intravenously. If the patients becomes asymptomatic on these medication and is still asymptomatic when the medication is stopped, rest and stress imaging testing will be performed. The advantage of conservative therapy is reduction of the number of unnecessary revascularizations. The disadvantage is a prolonged stay in the hospital. | |||
===Rest and Stress Imaging Tests=== | |||
Rest and stress testing is indicated in patients with: | |||
# Angina pectoris with ECG abnormalities during exercise ECG testing | |||
# Asymptomatic NSTEMI after in hospital conservative therapy | |||
Exercise echocardiography means that an echocardiography is made directly after exercise. The poorly perfused parts of the heart will show less activity. | |||
Myocardium Perfusion Scintigraphy (MPS) is able to show the perfusion of the heart during exercise and at rest. | |||
MRI can be done with vasodilatory dobutamine or stimulating adenosine to assess how the heart behaves during exercise. | |||