PATHOPHYSIOLOGY OF MI Myocardial infarction is a medical term of “heart attack” and is a serious result of coronary artery diseases that occurs from atherosclerosis which is a process of arterial wall damage and gradual occlusion associated with the infiltration of lipids and build up of plaque (Hand 2001).
Stained cross section through a Coronary artery and Coronary Artery with lipids deposit
Cont. The artery consist of three layers: the inner, the middle and the outer tunica. The atheromatous plaque begins to build up under the inner tunica, causing a gradual narrowing of the lumen of the artery to partial or complete occlusion and as the plaque develops it become vulnerable from rupture.
Cont. Rupture of the plaque expose a foreign surface to the blood that can lead to thrombosis (clotting) and this blood clot can result to the total artery occlusion MI can also occurs because of severe coronary spasm. The spasm will also slow down the blood flow through the vessels again promoting thrombosis (julian and cowan 1992)
cont Occlusion of the artery result in decrease perfusion (oxy supply) of the myocardium and when the supply of 02 is insufficient to meet the metabolic demand, myocardium ischemia occurs and prolonged ischemia result to MI and necrosis(20 min after) of the affected myocardial cells.
cont After coronary blood flow has ceased, the myocardium oxygen reserve is used within 8 sec and the anaerobic respiration is activated and the accumulation of hydrogen ions and lactic acid at this stage further compromises the myocardium.
Nursing care The patient will connected to the cardiac monitor for the detection of the cardiac arrhythmias Analgesia will be given as needed to try and keep the patient pain free.
Cont The patient is likely to be very frightened. Need to offer reassurance, using calm and confident manner. An intravenous cannula will be inserted to allow drugs to be given easily and immediately. The cannula must be observed and cared for.
cont The patient will be made comfortable and will have at least the first 2 days rest, as any activity will further increase the hearts oxygen demand. The heart rate, blood pressure and respiration rates should be done every 15 minutes.
Cont To address the imbalance between myocardial O2 supply and demand, prescribed O2 is frequently administered. The oxygen saturation should be continously recorded. An ECG will be done also. To monitor for arrhythmias.
cont fluid balance chart should be used to monitor the fluid balance as urine output is a good indicator of the ability of the heart to pump effectively and to perfuse the tissues adequately. The nurse will also liaise with other MDT and family members given them support as well as the patient.
Sign and symptoms Crushing chest pain that may radiate to arms throat and to jaw. This happens because one of the major arteries that supply blood and oxygen to the heart develops a clot and the supply to that area will stop. study by McNulty(2003) suggest that 25% of individuals might not experience pain.
cont Nausea, vomiting, sweating, pallor clammy skin and anxiety may occur as a result of peripheral vasoconstriction because the body diverts the blood supply towards the vital organs (brain and heart)
cont Hypotension (low bp) is caused by impaired pumping ability of the myocardium Tachycardia is increased, over 100 beats per minutes. This is due to the heart not getting adequate blood and oxygen supply
References Hand H(2001).Myocardium infarction: part1.Nursing standard.vol15(36),p45-53.