Myocardial Infarctions NCLEX® Review

A myocardial infarction (MI) or heart attack continues to be one of the leading causes of morbidity and mortality in the United States. According to the CDC, an MI occurs every 40 seconds here in the United States1. Every year they indicate that around 790,000 Americans have a heart attack with over half of them being their first MI.

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    Clients who don’t live a heart-healthy lifestyle increase their risk of developing an atherosclerotic lesion in their blood vessels. An MI occurs when a clot is formed over time in the coronary arteries which serve the purpose of supplying the heart with blood. The coronary arteries provide the heart with oxygen and nutrients while clearing out waste. These clots can be formed slowly over time which eventually leads to the diagnosis of coronary artery disease (CAD) or ischemic heart disease (IHD). Clients will present with signs and symptoms suggesting their heart is not getting enough oxygen.

    Over time, clients may present with symptoms of angina which describes the signs and symptoms of ischemia in the heart (e.g. chest pain, arm pain, back pain). Clients may present with stable angina which means the symptoms are reproduced consistently after physical exertion, and can go away on its own.

    Unstable angina describes clients experiencing this discomfort for a prolonged period which may present more severely and with little to no physical exertion triggering it. An MI occurs when a significant blockage of blood flow occurs in the heart which causes extreme often irrecoverable necrosis of heart tissues which can trickle down to further complications and potentially death.

    Causes of Myocardial Infarction

    There are many contributing factors that can increase the risk of having a heart attack – many of which can be modified to reduce this risk.

    Examples of modifiable risk factors include:

    • Obesity (BMI > 25)
    • Frequent use of artery narrowing drugs and substances (e.g. caffeine, theophyline)
    • Diets high in cholesterol (mainly LDL-C)
    • Comorbidities associated with narrowing of blood vessels (e.g. diabetes, hypertension)

    Uncontrollable factors include being male (especially African American) and advanced age > 50 years.

    Symptoms of Myocardial Infarction

    Chest pain is a key sign and symptom of clients who are experiencing an MI. This pain may be described as sudden, crushing, radiating, shooting, and with heavy pressure. This chest pain is often described clinically as substernal chest pain. These symptoms may be indicative of other issues (e.g. heartburn, gas, anxiety attack), so clinicians should be careful when screening for the possibility of a heart attack.

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    Clients with enough symptoms may be quickly admitted to the hospital and sent to a catheterization lab to further evaluate their condition and potentially provide treatment. Pain in other areas may help distinguish between other issues versus a heart attack. Examples include jaw pain, left arm pain, and pain in the mid-back or shoulder.

    Clients experiencing an MI may also experience shortness of breath (labored breathing), nausea and vomiting, sweating, pale cool “dusty” skin, and anxiety. It is important to note that some of these symptoms may go unobserved by certain populations including diabetics and women who either may not consider their condition critical or not feel it at all due to reduced sensation.

    Myocardial Infarction Pathophysiology

    When an MI occurs, the heart tissue will undergo significant stress as a result of poor blood flow to its cells. This can lead to necrosis of tissues including the cardiac muscles which can release a key protein called troponin which is a gold standard clinical manifestation of clients having a MI.

    Troponin levels of > 0.5 very likely indicate a client is having a heart attack. Other markers that may be evaluated include CK, CKmb, and CRP, which are not used as frequently for diagnosis.

    Clients with suspected MI will also like to have an abnormal EKG, which should be assessed immediately upon chest pain complaints. EKG changes are due to damage to the conductive tissue in the heart.

    This may present as ST elevation, which suggests no oxygen supply to the heart or potentially hyperkalemia which becomes confirmed by a positive troponin level. ST depression or T wave inversion may also indicate low oxygen supply in the heart suggesting a partial blockage or hypokalemia.

    Some clients may not have troponin elevations that become clinically significant that may still require further evaluation. Clinicians can run a stress test on these clients to ensure they are in stable condition. One stress test method involves having their clients exercise by running on a treadmill while monitoring their EKG and chest pain.

    The stress test should be discontinued after changes to their ST wave or onset of chest pain to prevent a critical event. Another stress test that can be utilized involves injecting a nuclear dye marker into the arteries which can be visualized to assess for blockage. These dyes or contrast can be extremely toxic to the kidneys, leading to acute kidney injury or chronic kidney disease.

    Clients being injected with dye should be taken off any medications that can exacerbate kidney damage such as NSAIDs, and even metformin at least until the dye has been completely cleared. They should also be instructed to hold substances for 24-48 hours including caffeine (including decaffeinated beverages), cigarettes, medications that can affect coronary blood flow (nitroglycerin, beta-blockers, theophylline), and should not eat or drink for four hours before or after the intervention.

    Clients should be encouraged to drink plenty of water after the procedure to dilute the dye. Clients with an allergy to iodine – where the allergy involves more than just facial flushing – should not be given contrast. Kidney function should be monitored with contrast use with a serum creatine – a Scr > 1.3 or a CrCL < 30 ml/hr serves as a potential contraindication to dye use.

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    Myocardial Infarction Treatment

    Time to treatment is critical when treating clients who may be having a heart attack. The goal is to unclog their arteries as soon as possible to achieve optimal results and prevent serious cardiac damage. For this reason, troponin-positive clients may be admitted to the catheterization lab to identify and treat the clot if present. Clients should not be eating for six to twelve hours prior to admission to the cath lab.

    A common surgical intervention is called a percutaneous coronary intervention or PCI. This procedure involves inserting a balloon into the coronary artery. It starts with inflating the balloon to dilate blood vessels and allow for blood flow, then inserting a cage to maintain the dilation and blood flow through the coronaries.

    Another surgical intervention is called coronary artery bypass grafting (CABG). This procedure involves extracting a blood vessel from another part of the body (usually the leg) and attaching it to a part of the heart before the blockage and another part after the block. This allows blood to flow normally in the heart by literally bypassing the block. A CABG is more invasive than a PCI which therefore extends recovery time, requiring more time in the hospital. A minimally invasive direct coronary artery bypass (MIDCAB) is similar to a procedure requiring a smaller incision.

    After the cath lab, clients should be advised to avoid heavy lifting and any situation where the incisions may become soaked. The goal is to prevent infection because if the tissue becomes infected it can lead to serious complications.

    After a cath procedure there it’s important to note that if the pedal pulse cannot be palpated the healthcare provider should be notified, as well as remarkably cool legs which suggest very low perfusion. However, the pedal pulse should be diminished for four to twelve hours after the procedure but any longer requires a referral.

    Myocardial Infarction Pharmacology

    Initially, clients admitted for suspected or diagnosed MI will be treated with oxygen as well as medications that can improve blood flow. These steps should be made prior to catheterization procedures as the preparations are made for surgical or pharmacological interventions to remove the clot.

    Nitroglycerin, or similar medications, are used as a vasodilator to improve blood flow in the coronary arteries. They should also be provided morphine, which can help with pain as well as reduce the stress to the heart. When morphine fails to relieve the client of pain their condition may be assessed as critical. Lastly, these clients may be put on aspirin which reduces the formation of platelets, thus preventing the clot from getting worse.

    Under certain circumstances, a client may be eligible to receive thrombolytics, which are used to dissolve and break up the clot as an alternative to surgical intervention. These agents should only be used around two to six hours after the initial MI.

    Thrombolytics are extremely dangerous medications as they can cause massive bleeding throughout the body. For this reason, many contraindications to using thrombolytics include active internal bleeding, current intracranial hemorrhage, severe uncontrolled hypertension, and serious head trauma within the last three months.

    There are two main thrombolytic agents that are used for myocardial infarctions. The more commonly used one is called TPA or alteplase. The other kind of thrombolytic used is streptokinase, which is used less commonly due to higher prevalence of allergies, including anaphylaxis.

    After the clot has been treated in clients, they will likely be put on heparin via IV route which is a blood thinner. It is important to recognize that heparin acts to prevent clots from being form rather than breaking the clot up. Therefore, heparin should never be used to treat an MI as it plays a role mostly in prevention.

    Clients should also be provided medications that can reduce the oxygen demands on the heart while improving blood flow. They may be initiated on nitroglycerin IV drip, dilating the coronary arteries to improve perfusion.

    Clients may also be put on a beta blocker or a calcium channel blocker that works on the heart (verapamil, diltiazem). These agents act to reduce the frequency of heartbeats as well the force of the contractions. This ultimately helps the heart by reducing the amount of oxygen and nutrients it needs, reducing stress on the cardiac tissue.

    After an MI a client will be chronically put on a variety of medications to reduce their risk of having another heart attack. They will be put on an ACE inhibitor or ARB as well as other blood pressure medications that can help reduce cardiac damage and even encourage remodeling of the cardiac tissue such as spironolactone. They will also be prescribed antiplatelet medications. Clients will also be discharged with a prescription for sublingual nitroglycerin which can be used when symptoms of angina are present.

    These can be dissolved under the tongue and can be repeated every 5 minutes until symptomatic resolution. If symptoms do not improve after the first five minutes, they should call 911 to treat another potential MI. Other forms of nitrates may also be prescribed to be taken daily in post-MI clients. It is essential to note that if they are prescribed nitrates, they should never be prescribed sexual enhancement medications like sildenafil (Viagra) or tadalafil (Cialis) as they can cause a life-threatening drug interaction.

    Nursing Interventions for Myocardial Infarction

    Post-MI clients will need to be provided with numerous consultations and monitored for a variety of complications. The first being the possibility of cardiogenic shock where a client’s blood pressure becomes very low as a result of reduced cardiac output. Signs and symptoms for cardiogenic shock includes agitation, cool pale skin, and low urine output.

    These clients should be treated with vasodilators to increase blood pressure (e.g. norepinephrine, epinephrine and dopamine).

    Post-MI clients are also at increased risk of developing a dysrhythmia, critical forms include ventricular fibrillation or ventricular tachyarrhythmia. These dysrhythmias occur in around 90% of recovering MI clients. Clients who do not have a pulse and are going through V Fib should be defibrillated (before performing CPR). Clients with a pulse that can be counted can undergo cardioversion to correct the arrhythmia.

    Another significant complication that can occur after an MI is heart failure which can become chronic. Clients with heart failure essentially have issues adequately pumping blood throughout their body – as a result fluid can start to buildup in the lungs and periphery of the client.

    These clients should be instructed to weigh themselves everyday to monitor for increased fluid retention. In the event of serious edema in the lungs or periphery loop diuretics like furosemide or torsemide may be used to alleviate these symptoms. These clients should also have their heart sounds monitored for S3 heart sounds.

    Another complication that can occur is pericarditis, which involves inflammation around the heart which can lead to deadly pericardial effusion causing the heart to stop bleeding. Signs and symptoms include jugular vein distension, extreme low blood pressure, and the inability to hear heart sounds. The last serious complication to monitor for is mitral valve prolapse where the valve becomes torn. These clients will have a heart murmur and may develop atrial fibrillation.

    Several lifestyle recommendations should be provided to clients to prevent heart failure’s onset and/or progression. The goal is to reduce stress to the heart as much as possible which means they should be advised to take it easy for a few weeks after their MI. Additionally they should be instructed to restrict sodium to < 2 grams/day and fluids to < 2 liters/day. They should also be advised to reduce stress, alcohol consumption caffeine.

    Post-MI clients should have a cholesterol panel taken and evaluated. Cholesterol goals includes a total cholesterol < 200, triglycerides < 150, LDL < 100, and HDL (good cholesterol) > 40. These clients should be instructed to avoid high cholesterol foods such as red meats and may be prescribed statins to reduce cholesterol levels.

    Statins may be prescribed for these clients to lower their LDL levels but should be used with caution in clients with liver disease. Additionally, they should be told to increase their fiber intake with fruits and vegetables.

    Other important counseling points to be made includes increasing exercise (with caution) up to 30 minutes a day for five days/week. To prevent scarring and atherosclerotic risk, clients who smoke should be advised to pursue smoking cessation treatment with their HCP “health care provider”. Finally, post-MI clients will have to avoid sexual intercourse as this can increase the risk of a heart attack. They should only be allowed to have sex after they can climb 2 flights of stairs without shortness of breath.

    Myocardial Infarction Conclusion

    Myocardial infarctions are very serious but unfortunately common events in the medical industry today. Medicine and surgery have come a long way in treating heart attacks as well as preventing future ones.

    Nevertheless, the modern lifestyle appears to contribute heavily to the likelihood of having an MI which means the prevalence of myocardial infarctions will remain high. It is critical to understand the signs and symptoms as well as treatment modalities to save the lives of your clients – which is why it is important to understand this subject matter when preparing for the NCLEX® exam.

    References

    1. Heart Attack Facts & Statistics. Centers for Disease Control and Prevention. https://www.cdc.gov/heartdisease/heart_attack.htm. Accessed October 6, 2019

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