Electrocardiography in myocardial infarction

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Electrocardiography in myocardial infarction
12 Lead EKG ST Elevation tracing color coded.jpg
12-lead electrocardiogram showing ST-segment elevation (orange) in I, aVL and V1-V5 with reciprocal changes (blue) in the inferior leads, indicative of an anterior wall myocardial infarction.
Purposedetecting ischemia or acute coronary injury in emergency department

Electrocardiography in suspected myocardial infarction has the main purpose of detecting ischemia or acute coronary injury in emergency department populations coming for symptoms of myocardial infarction (MI). Also, it can distinguish clinically different types of myocardial infarction.

Contents

Technical issues

An acute STEMI involving the inferior and right ventricular wall. Reciprocal changes are seen in the anterior leads. IandRStemi.JPG
An acute STEMI involving the inferior and right ventricular wall. Reciprocal changes are seen in the anterior leads.

The standard 12 lead electrocardiogram (ECG) has several limitations. An ECG represents a brief sample in time. Because unstable ischemic syndromes have rapidly changing supply versus demand characteristics, a single ECG may not accurately represent the entire picture. [1] It is therefore desirable to obtain serial 12 lead ECGs, particularly if the first ECG is obtained during a pain-free episode. Alternatively, many emergency departments and chest pain centers use computers capable of continuous ST segment monitoring. [2] The standard 12 lead ECG also does not directly examine the right ventricle, and is relatively poor at examining the posterior basal and lateral walls of the left ventricle. In particular, acute myocardial infarction in the distribution of the circumflex artery is likely to produce a nondiagnostic ECG. [1] The use of additional ECG leads like right-sided leads V3R and V4R and posterior leads V7, V8, and V9 may improve sensitivity for right ventricular and posterior myocardial infarction. In spite of these limitations, the 12 lead ECG stands at the center of risk stratification for the patient with suspected acute myocardial infarction. Mistakes in interpretation are relatively common, and the failure to identify high risk features has a negative effect on the quality of patient care. [3]

Main patterns

The 12 lead ECG is used to classify MI patients into one of three groups: [4]

  1. those with ST segment elevation or new bundle branch block (suspicious for acute injury and a possible candidate for acute reperfusion therapy with thrombolytics or primary PCI),
  2. those with ST segment depression or T wave inversion (suspicious for ischemia), and
  3. those with a so-called non-diagnostic or normal ECG. However, a normal ECG does not rule out acute myocardial infarction.

ST elevation MI

The 2018 European Society of Cardiology/American College of Cardiology Foundation/American Heart Association/World Health Federation Universal Definition of Myocardial Infarction for the ECG diagnosis of the ST segment elevation type of acute myocardial infarction require new ST elevation at J point of at least 1mm (0.1 mV) in two contiguous leads with the cut-points: ≥1 mm in all leads other than leads V2-V3. For leads V2-V3: ≥2 mm in men ≥40 years, ≥2.5 mm in men <40 years, or ≥1.5 mm in women regardless of age. This assumes usual calibration of 1mV/10mm. [5] These elevations must be present in anatomically contiguous leads. [4] (I, aVL, V5, V6 correspond to the lateral wall; V3-V4 correspond to the anterior wall ; V1-V2 correspond to the septal wall; II, III, aVF correspond to the inferior wall.) This criterion is problematic, however, as acute myocardial infarction is not the most common cause of ST segment elevation in chest pain patients. [6] Over 90% of healthy men have at least 1 mm (0.1 mV) of ST segment elevation in at least one precordial lead. [7] The clinician must therefore be well versed in recognizing the so-called ECG mimics of acute myocardial infarction, which include left ventricular hypertrophy, left bundle branch block, paced rhythm, early repolarization, pericarditis, hyperkalemia, and ventricular aneurysm. [7] [8] [9]

Localisation of the occlusion in the ECG showing STEMI changes Localisation of the occlusion in STEMI.svg
Localisation of the occlusion in the ECG showing STEMI changes

There are heavily researched clinical decision tools such as the TIMI Scores which help prognose and diagnose STEMI based on clinical data. For example, TIMI scores are frequently used to take advantage of EKG findings to prognose patients with MI symptoms. [10] Based on symptoms and electrocardiographic findings, practitioners can differentiate between unstable angina, NSTEMI and STEMI, normally in the emergency room setting. [11] Other calculators such as the GRACE [12] and HEART [13] scores, assess other major cardiac events using electrocardiogram findings, both predicting mortality rates for 6 months and 6 weeks, respectively.[ citation needed ]

Typical progression

Sometimes the earliest presentation of acute myocardial infarction is the hyperacute T wave, which is treated the same as ST segment elevation. [14] In practice this is rarely seen, because it only exists for 2–30 minutes after the onset of infarction. [15] Hyperacute T waves need to be distinguished from the peaked T waves associated with hyperkalemia. [16]

In the first few hours the ST segments usually begin to rise. [17] Pathological Q waves may appear within hours or may take greater than 24 hr. [17] The T wave will generally become inverted in the first 24 hours, as the ST elevation begins to resolve. [17]

Long term changes of ECG include persistent Q waves (in 90% of cases) and persistent inverted T waves. [17] Persistent ST elevation is rare except in the presence of a ventricular aneurysm. [17]

See also

Related Research Articles

<span class="mw-page-title-main">Electrocardiography</span> Examination of the hearts electrical activity

Electrocardiography is the process of producing an electrocardiogram, a recording of the heart's electrical activity through repeated cardiac cycles. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat). Changes in the normal ECG pattern occur in numerous cardiac abnormalities, including:

<span class="mw-page-title-main">T wave</span> Repolarization of the ventricles in a human heart

In electrocardiography, the T wave represents the repolarization of the ventricles. The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period. The last half of the T wave is referred to as the relative refractory period or vulnerable period. The T wave contains more information than the QT interval. The T wave can be described by its symmetry, skewness, slope of ascending and descending limbs, amplitude and subintervals like the Tpeak–Tend interval.

<span class="mw-page-title-main">Acute coronary syndrome</span> Medical condition

Acute coronary syndrome (ACS) is a syndrome due to decreased blood flow in the coronary arteries such that part of the heart muscle is unable to function properly or dies. The most common symptom is centrally located pressure-like chest pain, often radiating to the left shoulder or angle of the jaw, and associated with nausea and sweating. Many people with acute coronary syndromes present with symptoms other than chest pain, particularly women, older people, and people with diabetes mellitus.

<span class="mw-page-title-main">Variant angina</span> Medical condition

Variant angina, also known as Prinzmetal angina,vasospastic angina, angina inversa, coronary vessel spasm, or coronary artery vasospasm, is a syndrome typically consisting of angina. Variant angina differs from stable angina in that it commonly occurs in individuals who are at rest or even asleep, whereas stable angina is generally triggered by exertion or intense exercise. Variant angina is caused by vasospasm, a narrowing of the coronary arteries due to contraction of the heart's smooth muscle tissue in the vessel walls. In comparison, stable angina is caused by the permanent occlusion of these vessels by atherosclerosis, which is the buildup of fatty plaque and hardening of the arteries.

<span class="mw-page-title-main">Unstable angina</span> Medical condition

Unstable angina is a type of angina pectoris that is irregular or more easily provoked. It is classified as a type of acute coronary syndrome.

<span class="mw-page-title-main">Left bundle branch block</span> Medical condition

Left bundle branch block (LBBB) is a conduction abnormality in the heart that can be seen on an electrocardiogram (ECG). In this condition, activation of the left ventricle of the heart is delayed, which causes the left ventricle to contract later than the right ventricle.

<span class="mw-page-title-main">Acute pericarditis</span> Medical condition

Acute pericarditis is a type of pericarditis usually lasting less than 6 weeks. It is the most common condition affecting the pericardium.

P2Y<sub>12</sub> Protein-coding gene in the species Homo sapiens

P2Y12 is a chemoreceptor for adenosine diphosphate (ADP) that belongs to the Gi class of a group of G protein-coupled (GPCR) purinergic receptors. This P2Y receptor family has several receptor subtypes with different pharmacological selectivity, which overlaps in some cases, for various adenosine and uridine nucleotides. The P2Y12 receptor is involved in platelet aggregation and is thus a biological target for the treatment of thromboembolisms and other clotting disorders. Two transcript variants encoding the same isoform have been identified for this gene.

Door-to-balloon is a time measurement in emergency cardiac care (ECC), specifically in the treatment of ST segment elevation myocardial infarction. The interval starts with the patient's arrival in the emergency department, and ends when a catheter guidewire crosses the culprit lesion in the cardiac cath lab. Because of the adage that "time is muscle", meaning that delays in treating a myocardial infarction increase the likelihood and amount of cardiac muscle damage due to localised hypoxia, ACC/AHA guidelines recommend a door-to-balloon interval of no more than 90 minutes. As of 2006 in the United States, fewer than half of STEMI patients received reperfusion with primary percutaneous coronary intervention (PCI) within the guideline-recommended timeframe. It has become a core quality measure for the Joint Commission on Accreditation of Healthcare Organizations (TJC).

The Thrombolysis In Myocardial Infarction (TIMI) Study Group, is an academic research organization (ARO) affiliated with Brigham and Women's Hospital and Harvard Medical School with a focus in the field of cardiovascular disease. The group has its headquarters in Boston, Massachusetts.

<span class="mw-page-title-main">Wellens' syndrome</span> Medical condition

Wellens' syndrome is an electrocardiographic manifestation of critical proximal left anterior descending (LAD) coronary artery stenosis in people with unstable angina. Originally thought of as two separate types, A and B, it is now considered an evolving wave form, initially of biphasic T wave inversions and later becoming symmetrical, often deep, T wave inversions in the anterior precordial leads.

<span class="mw-page-title-main">Myocardial infarction</span> Interruption of blood supply to a part of the heart

A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops in one of the coronary arteries of the heart, causing infarction to the heart muscle. The most common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck or jaw. Often such pain occurs in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like heartburn. Other symptoms may include shortness of breath, nausea, feeling faint, a cold sweat, feeling tired, and decreased level of consciousness. About 30% of people have atypical symptoms. Women more often present without chest pain and instead have neck pain, arm pain or feel tired. Among those over 75 years old, about 5% have had an MI with little or no history of symptoms. An MI may cause heart failure, an irregular heartbeat, cardiogenic shock or cardiac arrest.

<span class="mw-page-title-main">ST elevation</span> Elevation of the ST segment on an electrocardiogram

ST elevation refers to a finding on an electrocardiogram wherein the trace in the ST segment is abnormally high above the baseline.

<span class="mw-page-title-main">ST depression</span> Depression of the ST segment on an electrocardiogram

ST depression refers to a finding on an electrocardiogram, wherein the trace in the ST segment is abnormally low below the baseline.

<span class="mw-page-title-main">Reperfusion therapy</span> Restoring blood flow post-heart attack

Reperfusion therapy is a medical treatment to restore blood flow, either through or around, blocked arteries, typically after a heart attack. Reperfusion therapy includes drugs and surgery. The drugs are thrombolytics and fibrinolytics used in a process called thrombolysis. Surgeries performed may be minimally-invasive endovascular procedures such as a percutaneous coronary intervention (PCI), which involves coronary angioplasty. The angioplasty uses the insertion of a balloon and/or stents to open up the artery. Other surgeries performed are the more invasive bypass surgeries that graft arteries around blockages.

<span class="mw-page-title-main">Francis M. Fesmire</span> American emergency physician (1969–2014)

Francis Miller Fesmire was an American emergency physician and a nationally recognized expert in myocardial infarction. He authored numerous academic articles and assisted in the development of clinical guidelines on the standard of care in treating patients with suspected myocardial infarction by the American College of Emergency Physicians and the American Heart Association/American College of Cardiology. He performed numerous research investigations in chest pain patients, reporting the usefulness of continuous 12-lead ECG monitoring, two-hour delta cardiac marker testing, and nuclear cardiac stress testing in the emergency department. The culmination of his studies was The Erlanger Chest Pain Evaluation Protocol published in the Annals of Emergency Medicine in 2002. In 2011 he published a novel Nashville Skyline that received a 5 star review by ForeWord Reviews. His most recent research involved the risk stratification of chest pain patients in the emergency department.

A diagnosis of myocardial infarction is created by integrating the history of the presenting illness and physical examination with electrocardiogram findings and cardiac markers. A coronary angiogram allows visualization of narrowings or obstructions on the heart vessels, and therapeutic measures can follow immediately. At autopsy, a pathologist can diagnose a myocardial infarction based on anatomopathological findings.

<span class="mw-page-title-main">Management of acute coronary syndrome</span>

Management of acute coronary syndrome is targeted against the effects of reduced blood flow to the affected area of the heart muscle, usually because of a blood clot in one of the coronary arteries, the vessels that supply oxygenated blood to the myocardium. This is achieved with urgent hospitalization and medical therapy, including drugs that relieve chest pain and reduce the size of the infarct, and drugs that inhibit clot formation; for a subset of patients invasive measures are also employed. Basic principles of management are the same for all types of acute coronary syndrome. However, some important aspects of treatment depend on the presence or absence of elevation of the ST segment on the electrocardiogram, which classifies cases upon presentation to either ST segment elevation myocardial infarction (STEMI) or non-ST elevation acute coronary syndrome (NST-ACS); the latter includes unstable angina and non-ST elevation myocardial infarction (NSTEMI). Treatment is generally more aggressive for STEMI patients, and reperfusion therapy is more often reserved for them. Long-term therapy is necessary for prevention of recurrent events and complications.

Sgarbossa's criteria are a set of electrocardiographic findings generally used to identify myocardial infarction in the presence of a left bundle branch block (LBBB) or a ventricular paced rhythm.

<span class="mw-page-title-main">De Winter syndrome</span> Medical condition

de Winter syndrome is an electrocardiogram (ECG) pattern which often represents sudden near blockage of the left anterior descending artery (LAD). Symptoms include chest pain, shortness of breath, and sweating.

References

  1. 1 2 Cannon CP at al. Management of Acute Coronary Syndromes. p. 175. New Jersey: Humana Press, 1999. ISBN   0-89603-552-2.
  2. ↑ Selker HP, Zalenski RJ, Antman EM, et al. (January 1997). "An evaluation of technologies for identifying acute cardiac ischemia in the emergency department: executive summary of a National Heart Attack Alert Program Working Group Report". Ann Emerg Med. 29 (1): 1–12. doi: 10.1016/S0196-0644(97)70297-X . PMID   8998085.
  3. ↑ Masoudi FA, Magid DJ, Vinson DR, et al. (October 2006). "Implications of the failure to identify high-risk electrocardiogram findings for the quality of care of patients with acute myocardial infarction: results of the Emergency Department Quality in Myocardial Infarction (EDQMI) study". Circulation. 114 (15): 1565–71. doi: 10.1161/CIRCULATIONAHA.106.623652 . PMID   17015790.
  4. 1 2 Ecc Committee, Subcommittees Task Forces of the American Heart Association (2005). "2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care — Part 8: Stabilization of the Patient With .......Acute Coronary Syndromes". Circulation. 112 (24_suppl): IV–89–IV–110. doi: 10.1161/CIRCULATIONAHA.105.166561 . PMID   16314375.
  5. ↑ Thygesen, Kristian; Alpert, Joseph S.; Jaffe, Allan S.; Chaitman, Bernard R.; Bax, Jeroen J.; Morrow, David A.; White, Harvey D. (October 2018). "Fourth Universal Definition of Myocardial Infarction (2018)". Journal of the American College of Cardiology. 72 (18): 2252. doi: 10.1016/j.jacc.2018.08.1038 . hdl: 10044/1/73052 . PMID   30153967.
  6. ↑ Brady WJ, Perron AD, Martin ML, Beagle C, Aufderheide TP (January 2001). "Cause of ST segment abnormality in ED chest pain patients". Am J Emerg Med. 19 (1): 25–8. doi:10.1053/ajem.2001.18029. PMID   11146012.
  7. 1 2 Wang K, Asinger RW, Marriott HJ (November 2003). "ST-segment elevation in conditions other than acute myocardial infarction". N. Engl. J. Med. 349 (22): 2128–35. doi:10.1056/NEJMra022580. PMID   14645641.
  8. ↑ Brady WJ, Chan TC, Pollack M (January 2000). "Electrocardiographic manifestations: patterns that confound the EKG diagnosis of acute myocardial infarction-left bundle branch block, ventricular paced rhythm, and left ventricular hypertrophy". J Emerg Med. 18 (1): 71–8. doi:10.1016/S0736-4679(99)00178-X. PMID   10645842.
  9. ↑ Brady WJ, Perron AD, Chan T (April 2001). "Electrocardiographic ST-segment elevation: correct identification of acute myocardial infarction (AMI) and non-AMI syndromes by emergency physicians". Acad Emerg Med. 8 (4): 349–60. doi:10.1111/j.1553-2712.2001.tb02113.x. PMID   11282670.
  10. ↑ David A. Morrow; Elliott M. Antman; Andrew Charlesworth; Richard Cairns; Sabina A. Murphy; James A. de Lemos; Robert P. Giugliano; Carolyn H. McCabe; Eugene Braunwald (2000). "TIMI Risk Score for ST-Elevation Myocardial Infarction: A Convenient, Bedside, Clinical Score for Risk Assessment at Presentation: An Intravenous nPA for Treatment of Infarcting Myocardium Early II Trial Substudy". Circulation. 102 (17): 2031–7. doi: 10.1161/01.cir.102.17.2031 . PMID   11044416.
  11. ↑ David A. Morrow; Elliott M. Antman; Andrew Charlesworth; Richard Cairns; Sabina A. Murphy; James A. de Lemos; Robert P. Giugliano; Carolyn H. McCabe; Eugene Braunwald (2000). "The TIMI Risk Score for Unstable Angina/Non–ST Elevation MI: A Method for Prognostication and Therapeutic Decision Making". JAMA. 284 (7): 835–42. doi: 10.1001/jama.284.7.835 . PMID   10938172.
  12. ↑ Fox KA, Dabbous OH, Goldberg RJ, Pieper KS, Eagle KA, Van de Werf F, Avezum A, Goodman SG, Flather MD, Anderson FA Jr, Granger CB (2006). "Prediction of risk of death and myocardial infarction in the six months after presentation with acute coronary syndrome: prospective multinational observational study (GRACE)". BMJ. 333 (7578): 2153–8. doi:10.1136/bmj.38985.646481.55. PMC   1661748 . PMID   17032691.
  13. ↑ Backus BE, Six AJ, Kelder JC, Bosschaert MA, Mast EG, Mosterd A, Veldkamp RF, Wardeh AJ, Tio R, Braam R, Monnink SH, van Tooren R, Mast TP, van den Akker F, Cramer MJ, Poldervaart JM, Hoes AW, Doevendans PA (2013). "A prospective validation of the HEART score for chest pain patients at the emergency department". Circulation. 168 (3): 2153–8. doi: 10.1016/j.ijcard.2013.01.255 . PMID   23465250.
  14. ↑ Somers MP, Brady WJ, Perron AD, Mattu A (May 2002). "The Prominent T wave: electrocardiographic differential diagnosis". Am J Emerg Med. 20 (3): 243–51. doi:10.1053/ajem.2002.32630. PMID   11992348.
  15. ↑ Smith SW, Whitwam W (February 2006). "Acute coronary syndromes". Emerg. Med. Clin. North Am. 24 (1): 53–89, vi. doi:10.1016/j.emc.2005.08.008. PMID   16308113.
  16. ↑ Van Mieghem C, Sabbe M, Knockaert D (April 2004). "The clinical value of the ECG in noncardiac conditions". Chest. 125 (4): 1561–76. doi:10.1378/chest.125.4.1561. PMID   15078775. Archived from the original on 2008-12-10.
  17. 1 2 3 4 5 gpnotebook.co.uk > ECG changes in myocardial infarction Retrieved on June 16, 2010
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