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Acute Myocardial Infarction

Myocardium Infarction Acute

Acute myocardial infarction (AMI) ,colloquially referred to as a heart attack, is an irreversible death of a myocardial segment sequel to persistent occlusion and inadequacy of coronary blood flow to the heart. AMI typically presents with central chest pain which may radiate to the neck, left arm, jaw, and shoulders. Accompanying these symptoms are diaphoresis, dyspnea and presyncope.


Presentation

Presentation of acute MI may range from asymptomatic to sudden cardiac death. Asymptomatic AMIs occur most commonly in diabetics. Typical symptoms of acute MI include;

  • Chest pain, which could be experienced as pressure or a squeezing/choking sensation at the center of the chest which radiates to the jaw, shoulder, left arm and, occasionally, to the back.
  • Chest pain may, typically, be associated with the following; dyspnea, epigastric pain, palpitations, diaphoresis, syncope or presyncope and disorientation. AMIs occur most likely in the early hours of the morning and with exertion.
Dyspnea
  • A previously asymptomatic 53-year-old male presented 5 days after an acute anterior wall myocardial infarction, who was fibrinolytic naïve, with worsening dyspnea.[ncbi.nlm.nih.gov]
  • After 48h following the accident, the patient's condition rapidly deteriorated, with severe dyspnea at rest, tachycardia, and increasing chest pain.[ncbi.nlm.nih.gov]
  • A 77-year-old male presented to our hospital with a 4-day history of severe dizziness, mild chest tightness, and dyspnea. An inferior AMI was diagnosed. On the second hospital day, hypotension and a new cardiac murmur was found.[ncbi.nlm.nih.gov]
  • Accompanying these symptoms are diaphoresis, dyspnea and presyncope. Presentation of acute MI may range from asymptomatic to sudden cardiac death. Asymptomatic AMIs occur most commonly in diabetics.[symptoma.com]
  • Symptoms include chest discomfort with or without dyspnea, nausea, and diaphoresis. Diagnosis is by ECG and the presence or absence of serologic markers.[msdmanuals.com]
Rales
  • There may be signs of congestive heart failure, including pulmonary rales, peripheral oedema, elevated jugular venous pressure.[patient.info]
  • Rales may be audible if pulmonary edema is present and the patient is experiencing heart failure. In this situation, there may be concurrent jugular venous distension peripheral edema and a S3 gallop. Diaphoresis can be common in AMI.[clinicaladvisor.com]
  • Class I: No evidence of HF (mortality 6%) Class II: Findings of mild to moderate HF (S3 gallop, rales halfway up lung fields or elevated jugular venous pressure (mortality 17%) Class III: Pulmonary edema (mortality 38%) Class IV: Cardiogenic shock defined[healio.com]
  • Chest Rales or wheezes may be auscultated; these occur secondary to pulmonary venous hypertension, which is associated with extensive acute left ventricular MI. Unilateral or bilateral pleural effusions may produce egophony at the lung bases.[emedicine.medscape.com]
Respiratory Distress
  • Physical Examination Physical examination findings for myocardial infarction (MI) can vary; one patient may be comfortable in bed, with normal examination results, whereas another patient may be in severe pain, with significant respiratory distress and[emedicine.medscape.com]
Dyspnea at Rest
  • After 48h following the accident, the patient's condition rapidly deteriorated, with severe dyspnea at rest, tachycardia, and increasing chest pain.[ncbi.nlm.nih.gov]
Coronary Artery Disease
  • Dyslipidemia may also be the indirect link between diabetes and coronary artery disease. Diabetes causes coronary artery diseases directly by causing endothelial damage.[symptoma.com]
  • We present this unusual case of cisplatin-induced acute myocardial infarction in a patient with no organic coronary artery disease (CAD), receiving chemoradiation for small cell lung cancer.[ncbi.nlm.nih.gov]
  • Also, fQRS is considered to predict an increased likelihood of a poor outcome and mortality in patients with coronary artery disease (CAD), even for some successfully revascularized AMI patients.[ncbi.nlm.nih.gov]
  • It could predict severe clinical complications and higher risks in coronary artery disease. Although there is little electrophysiological explanation, the complications are severe.[ncbi.nlm.nih.gov]
  • Although TC is increasingly recognized as a true but relatively infrequent clinical entity, it is still important to carefully rule out obstructive coronary artery disease.[ncbi.nlm.nih.gov]
Congestive Heart Failure
  • We identified subpopulations who benefitted from the law, such as former and current smokers, and those without comorbidities such as congestive heart failure and hypertension.[ncbi.nlm.nih.gov]
  • Relevance A-Z Length - Synonyms for acute myocardial infarction noun heart failure cardiovascular disease congestive heart failure acute myocardial infarction angina pectoris cardiac arrest chest pains coronary coronary infarction coronary thrombosis[thesaurus.com]
  • The reduced left ventricular ejection fraction may lead to congestive heart failure and predispose to ventricular arrhythmias.[brown.edu]
  • COMPLICATIONS The principal complications of acute myocardial infarction are shock, acute left ventricular failure, congestive heart failure, abnormalities of cardiac rhythm, thromboembolism, rupture of the ventricle, perforation of the interventricular[jamanetwork.com]
  • Downside of improved survival after AMI is the increase of both incidence and prevalence of congestive heart failure (CHF).[encarebiotech.com]
Fatigue
  • However, GAD was also highly associated with impaired psychological well-being, stress and fatigue (p   0.0001). In AMI patients, GAD was independently associated with less prehospital delay, but led to an impaired psychological state.[ncbi.nlm.nih.gov]
  • Other signs: Anxiety, Cough, Fainting, breaking out in a cold sweat, Nausea, Light-headedness, or dizziness Less common signs may include seizures, fatigue, difficulty breathing when lying down or low blood pressure.[utmedicalcenter.org]
  • […] common heart attack symptom in women is chest pain, women often experience heart attack symptoms that are different from men, including: Pain in the jaw or shoulder; Sweating; Nausea; Shortness of breath; Indigestion or heartburn; and Weakness or unusual fatigue[atlantic-cardiology.net]
  • Although most patients present with typical chest pain, including women, women are more often reporting atypical chest pain and/or associated symptoms (dyspnea, fatigue, weakness) compared to men.[acc.org]
  • Instead, their most common symptoms are weakness, fatigue and dyspnea.[cvpharmacology.com]
Fever
  • Thrombotic microangiopathy (TMA) is a rare but lethal multisystem disease characterized by peripheral thrombocytopenia, microangiopathic hemolytic anemia, fever, and various stages of renal and neurological dysfunctions.(1,2)) The causes of TMA are mainly[ncbi.nlm.nih.gov]
  • Pericarditis pain is distinguishable from infarct pain because of its pleuritic nature, radiation to the left trapezius ridge, and the associated low-grade fever and pericardial friction rub.[brown.edu]
  • Signs Cardiovascular examination findings can vary enormously: Low-grade fever, pale and cool, clammy skin. Hypotension or hypertension can be observed depending on the extent of the myocardial infarction.[patient.info]
  • In the evening, she developed a mild fever. On the following day, she awoke early in the morning because of a severe precordial pain. She stated that the pain felt like a weight pushing on her chest.[pediatrics.aappublications.org]
Pallor
  • Gross morphologic changes evolve over time as follows: Time from Onset Gross Morphologic Finding 18 - 24 Hours Pallor of myocardium 24 - 72 Hours Pallor with some hyperemia 3 - 7 Days Hyperemic border with central yellowing 10 - 21 Days Maximally yellow[library.med.utah.edu]
  • Extremities Peripheral cyanosis, edema, pallor, diminished pulse volume, delayed rise, and delayed capillary refill may indicate vasoconstriction, diminished cardiac output, and right ventricular dysfunction or failure.[emedicine.medscape.com]
Nausea
  • Symptoms include chest discomfort with or without dyspnea, nausea, and diaphoresis. Diagnosis is by ECG and the presence or absence of serologic markers.[msdmanuals.com]
  • However, women are more likely than men to have: shortness of breath jaw pain upper back pain lightheadedness nausea vomiting In fact, some women who have had a heart attack report that their symptoms felt like the symptoms of the flu .[healthline.com]
  • Other signs: Anxiety, Cough, Fainting, breaking out in a cold sweat, Nausea, Light-headedness, or dizziness Less common signs may include seizures, fatigue, difficulty breathing when lying down or low blood pressure.[utmedicalcenter.org]
  • Although the most common heart attack symptom in women is chest pain, women often experience heart attack symptoms that are different from men, including: Pain in the jaw or shoulder; Sweating; Nausea; Shortness of breath; Indigestion or heartburn; and[atlantic-cardiology.net]
Vomiting
  • However, women are more likely than men to have: shortness of breath jaw pain upper back pain lightheadedness nausea vomiting In fact, some women who have had a heart attack report that their symptoms felt like the symptoms of the flu .[healthline.com]
  • […] common symptoms include: Chest discomfort that may start out feeling mild and build in intensity; Discomfort in other areas of the upper body; Shortness of breath; Breaking out in a cold sweat; Feeling dizzy, light-headed or nauseated; or Belching or vomiting[atlantic-cardiology.net]
  • Chest pain with nausea and vomiting, marked sweating and/or breathlessness, or haemodynamic instability.[patient.info]
Abdominal Pain
  • A 49-year-old male patient presented to our clinic with abdominal pain and markedly elevated concentrations of C‑reactive protein, creatinine and high-sensitivity cardiac troponin T.[ncbi.nlm.nih.gov]
  • This patient experienced abdominal pain 35 hours prior to death. As the infarct progresses between 24 and 48 hours, coagulation necrosis is established, with various degrees of nuclear pyknosis, early karyorrhexis, and karyolysis.[emedicine.medscape.com]
  • Symptoms Common heart attack signs and symptoms include: Pressure, tightness, pain, or a squeezing or aching sensation in your chest or arms that may spread to your neck, jaw or back Nausea, indigestion, heartburn or abdominal pain Shortness of breath[mayoclinic.org]
Epigastric Pain
  • Differential diagnosis of acute myocardial infarction Arm pain Myocardial ischemia, cervical/thoracic vertebral pain, thoracic outlet syndrome Epigastric pain Myocardial ischemia, GI tract–esophagus, peptic ulcers, pancreas, liver disease–cholecystitis[medical-dictionary.thefreedictionary.com]
  • Chest pain may, typically, be associated with the following; dyspnea, epigastric pain, palpitations, diaphoresis, syncope or presyncope and disorientation. AMIs occur most likely in the early hours of the morning and with exertion.[symptoma.com]
Jaw Pain
  • However, women are more likely than men to have: shortness of breath jaw pain upper back pain lightheadedness nausea vomiting In fact, some women who have had a heart attack report that their symptoms felt like the symptoms of the flu .[healthline.com]
  • Atypical symptoms include abdominal discomfort or jaw pain; elderly patients may present with altered mental state. Signs Cardiovascular examination findings can vary enormously: Low-grade fever, pale and cool, clammy skin.[patient.info]
Chest Pain
  • For diagnosing AMI from ACS patients, MPO was the most efficient marker than others markers with efficiency 82.5% within 0-6 hr after the onset time of chest pain.[ncbi.nlm.nih.gov]
  • An adolescent male with a recent history of streptococcal pharyngitis presented with severe substernal chest pain, troponin leak, and ST-segment elevation, which are suggestive of acute inferolateral myocardial infarction.[ncbi.nlm.nih.gov]
  • If a young woman complaining of typical chest pain as acute coronary syndrome is encountered, systemic diseases must be considered.[ncbi.nlm.nih.gov]
  • A 25-year-old previously healthy male presented to our emergency room with acute chest pain and ventricular arrhythmia-related cardiac arrest.[ncbi.nlm.nih.gov]
Heart Disease
  • The pathogenesis of ischemic heart disease among patients with nephrosis is commonly thrombosis, whereas atherosclerosis is rare, especially in young individuals.[ncbi.nlm.nih.gov]
  • A bifid cardiac apex is a rare congenital cardiac anomaly in humans and is usually associated with other congenital heart diseases.[ncbi.nlm.nih.gov]
  • Fragmented QRS (fQRS) has been shown to be a valuable electrocardiographic (ECG) index for predicting the prognosis of patients with coronary heart disease.[ncbi.nlm.nih.gov]
  • Acute myocardial infarction (AMI) is the most serious type of coronary atherosclerotic heart disease (CAD). The pathological changes are characterized by atherosclerosis. Oxidative stress plays an important role in atherosclerosis.[ncbi.nlm.nih.gov]
  • Synergy between heart disease risk factors and MD underlines the need to enlarge the list of known modifiable cardiovascular risk factors to include and promote adherence to Mediterranean dietary habits.[ncbi.nlm.nih.gov]
Tachycardia
  • After 48h following the accident, the patient's condition rapidly deteriorated, with severe dyspnea at rest, tachycardia, and increasing chest pain.[ncbi.nlm.nih.gov]
  • Synonyms for acute myocardial infarction noun heart failure cardiovascular disease congestive heart failure acute myocardial infarction angina pectoris cardiac arrest chest pains coronary coronary infarction coronary thrombosis myocardial infarction tachycardia[thesaurus.com]
  • These data show the following: ( a ) LVEDP is usually elevated in acute myocardial infarction, even in absence of clinical heart failure; ( b ) cardiac output apparently is supported by increased LVEDP and compensatory tachycardia; ( c ) in patients with[jci.org]
  • The risk score includes 8 variables [age, systolic blood pressure, heart rate, initial glomerular filtration rate (GFR), serum glucose, Killip class, cardiac arrest, ventricular tachycardia/ventricular fibrillation (VT/VF)].[ncbi.nlm.nih.gov]
  • For those outcomes where there was evidence of heterogeneity , meta-analysis with both fixed-effect and random-effects models showed that magnesium could decrease ventricular tachycardia ( OR 0.45, 95% CI 0.31 to 0.66 by fixed-effect model; OR 0.40, 95%[cochrane.org]
Hypotension
  • On the second hospital day, hypotension and a new cardiac murmur was found. The emergency echocardiographic study disclosed a ventricular septal defect. Soon after that the patient suddenly died of ventricular free-wall rupture.[ncbi.nlm.nih.gov]
  • Hypotension : Hypotension may occur in various settings following acute MI.[brown.edu]
  • Their results were mixed: IV magnesium reduced the incidence of serious arrhythmias, but this treatment also increased the incidence of profound hypotension, bradycardia and flushing.[cochrane.org]
  • These drugs provide potent alpha-1 constriction and are used in the management of hypotension. Norepinephrine and epinephrine have Beta-1 stimulation as well. These drugs not only squeeze, they stimulate.[cathlabdigest.com]
  • Alternative mechanisms that can cause this mismatch in oxygen supply and demand include coronary vasospasm, severe aortic stenosis, extreme exertion, and hemodynamic changes such as hypotension and hypertension.[clinicaladvisor.com]
Systolic Murmur
  • On day 2, however, the patient's vital signs deteriorated to a state of shock and systolic murmur appeared at the apical region. TTE showed a left-to-right shunt in the apical septal region, and ventricular septal perforation was diagnosed.[ncbi.nlm.nih.gov]
  • Diagnosis is made by detection of a new systolic murmur, and by the documentation of giant "V-waves" on the pulmonary capillary wedge tracing.[brown.edu]
  • Third and fourth heart sound, systolic murmur if mitral regurgitation or ventricular septal defect develops, pericardial rub.[patient.info]
Upper Back Pain
  • However, women are more likely than men to have: shortness of breath jaw pain upper back pain lightheadedness nausea vomiting In fact, some women who have had a heart attack report that their symptoms felt like the symptoms of the flu .[healthline.com]
Shoulder Pain
  • pain Myocardial ischemia, cervical vertebra, acute musculoskeletal lesions, pericardial pain, pleuritis, subdiaphragmatic abscess, thoracic outlet syndrome . a·cute cor·o·nar·y syn·drome (ACS) ( ă-kyūt' kōr'ŏ-nar-ē sin'drōm ) acute myocardial infarction[medical-dictionary.thefreedictionary.com]
Confusion
  • This anomaly, because it is rare, can be a source of confusion to clinicians, especially when acute coronary syndrome is present. The possible presence of this anomaly should, therefore, be kept in mind in daily practice.[ncbi.nlm.nih.gov]
  • This is because LBBB alone can produce signs that may be confused with those of infarction: deep QS waves in the right chest leads and ST depression and T wave inversion in the left chest leads.[medicine-on-line.com]
  • For each classification, a confusion table was calculated and used for benchmarking the performances of biomarkers.[clinchem.aaccjnls.org]
  • Patterns of Anterior Infarction The nomenclature of anterior infarction can be confusing, with multiple different terms used for the various infarction patterns. The following is a simplified approach to naming the different types of anterior MI.[lifeinthefastlane.com]
Altered Mental Status
  • In addition, some patients may have an altered mental status caused by medications or impaired cerebral perfusion.[emedicine.medscape.com]
Agitation
  • A catheter was placed in the right atrium in front of the fossa ovalis, and agitated saline solution was injected while the anesthesiologist induced a Valsalva maneuver.[pediatrics.aappublications.org]

Workup

The ECG is the diagnostic test of choice and should be done within 10 minutes of presentation. Therapeutic interventions are guided by ECG results. Diagnosis is confirmed with serial ECG tracings done every 8 hours within the first 24 hours of presentation, then once daily. Gradual return to normal ECG findings or development of abnormal Q waves confirm the diagnosis.

An elevation of the ST segment by at least 1 mm on the adjacent leads opposite the diseased area on the ECG is diagnostic of an ST segment elevation myocardial infarction (STEMI). ST segment elevation has a 90% specificity and 45% sensitivity in diagnosing AMI. In STEMI, ECG shows ST-segment elevation ≥ 1 mm in at least 2 adjacent leads opposite the damaged area, which is diagnostic as supposed to its absence in non-ST segment elevation myocardial infarction (NSTEMI).

AMI often has similar ECG tracings as left bundle branch block, therefore, it is recommended that patients with symptoms in keeping with AMI and a provisional diagnosis of left bundle branch block should be treated for STEMI.

Assay of cardiac markers helps in the diagnosis of AMI. Cardiac markers include CK-MB, myoglobin, troponin I, and troponin T. These cardiac markers have varying sensitivities and specificities for AMI. However, the troponins are most sensitive and specific and are the cardiac markers of choice in the diagnosis of AMI.

Coronary angiography serves for both diagnostic evaluation and therautic intervention in the management of AMI. In emergency settings, coronary angiography is recommended. It is also recommended as a therapeutic modality in patients unresponsive to medical therapy and those which severe cardiac sequalae such as cardiogenic shock and unstable arrhythmias. In unstable angina or uncomplicated NSTEMI, diagnostic angiography is necessary posttreatment for detection of untreated lesions.

Adjunct investigations include erythrocyte sedimentation rate and complete blood count. A high ESR supports, but is a non-specific index in the diagnosis of AMI. Additionally, same day lipid profile should be done in all patients treated for AMI.

Mural Thrombus
  • This is a low-power photomicrograph of a mural thrombus (1) adherent to the endocardial surface (arrows). This is a photomicrograph of the lines of Zahn.[peir.path.uab.edu]
  • Left ventricular aneurysm containing mural thrombus, gross. Ischemic cardiomyopathy, microscopic. Laboratory Diagnosis of Myocardial Infarction A number of laboratory biomarkers for myocardial injury are available.[library.med.utah.edu]
Pericardial Effusion
  • Echocardiography can define the extent of the infarction and assess overall ventricular function and can identify complications, such as acute mitral regurgitation, left ventricular rupture or pericardial effusion.[patient.info]
  • No pericardial effusion appeared. During the entire hospital admission, the patient did not experience additional thoracic pain or any other complaint. No specific therapy for MI was necessary.[pediatrics.aappublications.org]
  • Normally, the pericardium can expand as the heart fills; however, with cardiac tamponade from a large pericardial effusion or constrictive pericarditis, this is not able to occur.[healio.com]
Pulmonary Edema on Chest X-Ray
  • It is important to refrain from giving beta-blockers if there are signs of cardiogenic shock, such as hypotension or pulmonary edema on chest X-ray. Long-term (lifetime) therapy has been shown to reduce MI incidence and improve mortality.[healio.com]
Wide QRS Complex
  • Note the AV dissociation in the rhythm strip in lead V1 at the bottom; this is diagnostic for VT in the setting of a wide QRS complex tachycardia, but not always seen.[healio.com]
Inferior Q Wave
  • Q Waves - not Old Inferior Wall Myocardial Infarction (MI) ECG Old Inferior Wall Myocardial Infarction (MI) ECG (Example 1) Old Inferior Wall Myocardial Infarction (MI) ECG (Example 2) Posterior Wall Myocardial Infarctions Inferior-Posterior Wall Myocardial[healio.com]
Hypertriglyceridemia
  • Clinical Topics: Acute Coronary Syndromes, Arrhythmias and Clinical EP, Diabetes and Cardiometabolic Disease, Dyslipidemia, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Prevention, SCD/Ventricular Arrhythmias, Hypertriglyceridemia[acc.org]
  • […] for atherosclerosis include the following: Age Sex Family history of premature coronary heart disease Male-pattern baldness Modifiable risk factors for atherosclerosis include the following [22] : Smoking or other tobacco use Hypercholesterolemia and hypertriglyceridemia[emedicine.medscape.com]
ST Elevation
  • To characterize our approach, we focus on data completeness for critical event times and eligibility criteria, and on the analysis of ST-elevated MI (STEMI) patients according to received reperfusion treatment.[ncbi.nlm.nih.gov]
  • In the elderly ( 60 years), patients with non-ST-elevation myocardial infarction (NSTEMI) and ST-elevation myocardial infarction (STEMI) had significantly higher NLR than did those with unstable angina (UA) and stable angina pectoris (SAP) (P 0.01).[ncbi.nlm.nih.gov]
  • In this case report, we present a 15-year-old girl with nephrotic syndrome who had acute non-ST-elevation myocardial infarction secondary to atherosclerosis of the 3 coronary arteries.[ncbi.nlm.nih.gov]
  • Very occasionally, hypocalcemia can manifest with ST segment elevation forcing the differential diagnosis with ST elevation MI.[ncbi.nlm.nih.gov]
  • A 34-year-old lady admitted with diagnosis of ST elevation acute myocardial infarction with cardiogenic shock. Left ventricular function, severely depressed, returned to normal after initial stabilization. Coronary angiogram was normal.[ncbi.nlm.nih.gov]
Right Bundle Branch Block
  • BACKGROUND New-onset extreme right axis deviation and right bundle branch block (RBBB) are rare during acute myocardial infarction (AMI), and has only been reported in several cases reflecting the severity of AMI.[ncbi.nlm.nih.gov]
  • Right bundle branch block in anterior MI is an independent marker of poor prognosis; this is due to the extensive myocardial damage involved rather than the conduction disorder itself.[lifeinthefastlane.com]
  • Prognostic significance of right bundle branch block for patients with acute myocardial infarction: a systematic review and meta-analysis. Med Sci Monit . 2016 Mar 27. 22:998-1004. [Medline] . Kim KH, Jeon KN, Kang MG, et al.[emedicine.medscape.com]
T Wave Inversion
  • Features may initially be normal but abnormalities include new ST-segment elevation; initially peaked T waves and then T-wave inversion; new Q waves; new conduction defects. Do not exclude an ACS when people have a normal resting 12-lead ECG.[patient.info]
  • This is because LBBB alone can produce signs that may be confused with those of infarction: deep QS waves in the right chest leads and ST depression and T wave inversion in the left chest leads.[medicine-on-line.com]
  • Abnormal Q waves and T-wave inversion in I and aVL. The pattern indicates prior infarction of the anteroseptal and lateral walls.[lifeinthefastlane.com]
Ischemic Changes
  • Cardiac death with symptoms suggestive of myocardial ischemia and presumed new ischemic changes or injury or new BBB on ECG, but death occurred before cardiac biomarker levles were obtained, or before cardiac biomarker values would be increased.[emedicine.medscape.com]
Electrocardiogram Change
  • Of note, all these patients had acute MI documented by typical serial electrocardiogram changes and clinically significant release of cardiac markers, and all underwent mechanical reperfusion.[clinchem.aaccjnls.org]

Treatment

Both STEMI and NSTEMI have different courses of treatment, therefore, the importance of an early ECG cannot be overemphasized. Nonetheless, the first step of treating all cases of MI is an urgent revascularizaton and reperfusion. Thereafter, relief of pain and prevention or treatment of complications are initiated.

En route the emergency room, the patient should have an intravenous line in place and concurrent administration of supplemental oxygen, aspirin, and nitroglycerin. If available, a prehospital ECG should be obtained.

At the emergency department, medical reperfusion strategies should be commenced immediately. These reperfusion treatments include: thrombolytic therapy, anticoagulation, and antlatelet therapy. Thrombolytic treatment should be administered within 30 minutes of the patient's presentation. Beyond 2 hours of presentation, use of thrombolytics show little effectiveness. Thrombolytic therapy has not proven to be of benefit in the treatment of STEMI.

Antiplatelet therapy is also vital in management of AMI. It is associated with high success if administered early even before arriving at the hospital. Clopidogrel is used in cases of aspirin allergy. As recommended in the Antiplatelet Therapy for Reduction of Myocardial Damage During Angioplasty-Myocardial Infarction (ARMYDA-6 MI) multicenter study, a stat dose of 600 mg clopidogrel, compared to a 300 mg stat dose, prior to primary PCI was associated with a smaller infarct size [15].

Anticoagulation is the most critical aspect of treatment of ACS. It should be instituted together with anti platelet therapy in all suspected or diagnosed cases of unstable angina or NSTEMI. Unfractionated heparin, enoxaparin, and bivalirudin are examples of potent anticoagulants for use in these cases, especially those for whom invasive interventions may be necessarily.

Other aspects of treatment in the management of AMI include pain relief, correction of complications, and cardioprotective treatment plans. Pain relief is best achieved with morphine sulphate in STEMI [16].

ACE inhibitors and beta-blockers also significantly reduce morbidity and mortality in AMI. However, these should be used only after excluding all contraindications to their use. Angiotensin-receptor blockers are alternatives to ACE inhibitors if there are any contraindications to the use of ACE inhibitors. Nondihydropyridine calcium channel blockers ( verapamil and diltiazem) are indicated if there are contraindications to the use of beta-blockers upon exclusion of left ventricular failure, pulmonary edema and AV block [17] [18].

Failure of the above medical intervention and percutaneous interventions are indications for coronary artery bypass surgery (CABG). CABG is also indicated if there are concomitant cardiac complications or defects.

Prognosis

AMI causes death in 30% of cases, over half of which occur before the patient arrives at the hospital. Generally, most of the deaths caused by AMI occur within the first 24 hours of onset of symptoms. Up to 10% of patients who get treatment for AMI die within the same year of treatment, and in up to 50% of cases, there is a recurrence of AMI.

Most of the deaths from AMI are due to ventricular arrhythmias. Deaths within a year of successful treatment of AMI results from ventricular arrhythmias, ventricular failure, or a recurrent AMI. Consequently, a stress ECG is recommended for all patients successfully treated for AMI. Poor stress ECG results strongly predicts imminent mortality.

By and large, prognosis of AMI depends largely on the extent of myocardial necrosis, the timing of initiating reperfusion measures, and the degree of ventricular dysfunction. Early reperfusion and revascularization ( initiation of thrombolytic therapy within 30 minutes of presentation or of percutaneous intervention within 90 minutes of presentation) with preserved ventricular function is associated with a better prognosis.

A high thrombolysis in Myocardial infarction score (TIMI) is strongly associated with a high mortality rate in AMI. Several indices are taken into account in calculating this score. The more indices present in the individual, the higher the score. These indices include [7]:

1. At least 65 years of age.

2. Presence of at least 3 risk factors for artherosclerotic cardiovascular disease.

3. Positive history of coronary artery disease.

4. Elevated cardiac enzymes.

5. Aspirin use within the last one week.

6. ST segment elevation by at least 0.5mm.

Presence of risk factors of atheroscleotic vascular diseases, late or unsuccessful reperfusion, severe ventricular failure, congestive cardiac failure, pulmonary edema all contribute to high mortality and bad outcome [8] [9]. Laboratory findings of elevated B-natiuretic peptide, C-reactive proteins levels and high secretory-associated  phospholipase A2 activity are also associated with high mortality in AMI [10] [11] [12] [13] [14].

Etiology

The risk factors for AMI consist of diseases and lifestyle habits which predispose one to vascular damage and occlusion. These factors could be categorized as modifiable and nonmodifiable. The modifiable risk factors include diabetes mellitus, hyperlipidemia, hypertension, tobacco use, and substance abuse. The non modifiable risk factors include a male gender and a positive family history of vasculocclusive diseases.

High levels of total cholesterol, LDL, or triglycerides cause considerable increase in the risk of developing coronary artherosclerosis and AMI. Persistent reduction of HDL levels below 40mg/dl is also associated with a high risk of developing AMI [3]. Dyslipidemia may also be the indirect link between diabetes and coronary artery disease. Diabetes causes coronary artery diseases directly by causing endothelial damage.

Hypertension involving either or both systolic and diastolic pressures is a strong risk factor for coronary artery disease and AMI [4]. Tobacco use constitutes a significant risk factor of AMI and strokes. Constituents of tobacco impose toxic reactions to the endothelium of blood vessels. This injury, in turn, triggers an inflammatory response which results in atherosclerotic changes in the vessels [5].

Although, males are said to be at a higher risk of developing coronary artery disease than females, the incidence evens out with increasing age. A family history of atherosclerotic cardiovascular and cerebrovascular diseases are often associated with genetic links to these diseases, predisposing individuals with such family histories to developing coronary artery disease.

Coronary artery disease and AMI are not exclusively linked to atherosclerosis, other vascular and cardiac defects including vasculitis, valvular heart defects, coronary trauma, and congenital coronary defects may also predispose to AMI.

Epidemiology

Cardiovascular disease is the leading cause of death in the United States. As reported in the results of the 2005 Behavioral Risk Factor Surveillance System (BRFSS) survey, MI occurs more in men than women and the incidence of the disease significantly increases with age.

Sex distribution
Age distribution

Pathophysiology

Acute myocardial infarction is the terminal response of the heart to undercompensated and persistent myocardial ischemia. Most cases of AMI result from coronary artery disease involving atherosclerotic occlusion of the vessel [6]. This makes AMI a presentation of acute coronary syndromes.

An atherosclerotic plaque is made up of a lipid core and a fibromuscular outer layer. This outer layer is eroded with time by the actions of catalytic enzymes which include collagenases, proteases and matrix metalloproteases. This enzymatic breakdown coupled with hemodynamic forces in the blood vessel completely erode the fibromuscular layer and a consequent endothelial damage. The endothelial injury triggers the extrinsic coagulation pathway, eventually leading to thrombus formation. Occlusion of the coronary vessel is caused by the thrombus.

Persistent occlusion of the coronary vessel shifts changes from compensation to the occurrence of an acute myocardial infarction. Prolonged ischemia first leads to necrosis of the endocardium, then the myocardium before affecting the epicardium. After onset of AMI, failure to restore coronary blood flow within 8 hours leads to a significant myocardial loss. The severity of AMI is determined by the extent of myocardial necrosis, which in turn, is determined by the duration and level of coronary occlusion. The more proximal the coronary occlusion occurs, the greater the severity and complications of AMI.

Prevention

The modifiable risk factors for coronary artery disease can be prevented to forestall the occurrence or recurrence of AMI. Smoke cessation is associated with a 50% reduction in the risk of recurrence of AMI within the same year of quitting. This informs the recommendation of counselling and appropriate smoke cessation therapies for all patients with acute coronary syndrome who smoke.

Mild alcohol consumption has also been shown to reduce the risk of atherosclerotic vascular disease. However, there are no strict guildlines on alcohol use in the prevention of AMI and, therefore, should be based on the doctor's clinical discretion.

Summary

Acute myocardial infarction (AMI) refers to irreversible myocardial necrosis resulting from sustained myocardial ischemia [1] [2]. AMI is usually the complication of coronary artery disease in which an atherosclerotic plaque, mostly, occludes coronary blood flow. 

AMI may present with no symptoms at all. However, typical symptoms of AMI are a central chest pain which often radiates to the jaw, neck, left arms, and shoulders and which may be associated with dyspnea, palpitations and, presyncope.

Diagnosis of AMI is made by characteristic features on the ECG. However, coronary angiography presents an excellent modality for both diagnostic and therapeutic purposes in the management of AMI.

Treatment of AMI is achieved with fast institution of antiplatelet and thrombolytic therapy and, most importantly, anticoagulation. Percutaneous intervention and coronary artery bypass surgery may be necessary in cases unresponsive to medical treatment.

Patient Information

Overview.

Myocardial infarction is the medical term for a heart attack. A heart attack occurs when the blood flow to the heart is blocked for a long time. The heart muscle dies after a prolonged period of inadequate blood and oxygen supply. This death and sudden loss of action of the heart muscle is what is referred to as a heart attack. It presents suddenly, that's why its described as acute.

Etiology.

The obstruction of the blood supply is initiated by a fatty substance which attaches to the blood vessel wall, building up with time and trigerring the development of a clot which, ultimately, blocks the vessel. This deprivation of blood flow causes the heart muscle to die, becoming fatal in a few hours.The risk of having a heart attack increases with advancing age, tobacco smoking, diabetes and a family history of a heart attack, to name a few.

Presentation.

A heart attack , typically, presents with chest pain which radiates to the left arm, jaw, shoulders and neck. There could also be breathlessness, vomiting , and sweating. Patients also feel lightheaded and dizzy.

Work up.

An Electrocardiogram (ECG) is the diagnostic method of choice for AMI. Once your symptoms are typical of a heart attack, an urgent ECG would be ordered. Other laboratory tests such as cardiac enzyme levels may also be necessary to support the diagnosis. A coronary angiography is a form of X-ray of the blood vessels of the heart done after a dye is passed through them to make them more visible. This test may be ordered to view the coronary vessels and the site of the blockage and it could also be used to remove the blockage in emergency situations.

Treatment.

A heart attack requires an urgent treatment, which involves an urgent call to the paramedics who would initiate treatment to reopen the blood vessel even before reaching the hospital. The longer one stays without restoring the blood flow to the heart, the more likely the individual would die, even en route the hospital. In severe cases, surgery may be needed to repair the affected blood vessel.

Prognosis.

More than one-third of patients who develop a heart attack die, half of these people die before getting to the hospital. The key thing to note in AMI is that the longer the patient stays without treatment of the symptoms, the greater the extent of the heart muscle death and the higher the chances of death from this condition.

References

Article

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Last updated: 2018-06-21 20:35