Posterior myocardial infarction represents the end result of myocardial ischemia and coronary insufficiency due to acute obstruction of either right or circumflex coronary arteries. It is difficult to diagnose on classical 12 lead electrocardiogram as it only shows indirect signs. Identifying it is easier when it is associated with inferolateral infarction, which is most often the case, or when posterior leads are used.
The acute event in posterior myocardial infarction may be preceded by chest pain that becomes more prolonged and intense progressively and is accompanied by fatigability, malaise or no cardiovascular symptoms. The chest pain is intense, lasts for more than 30- 60 minutes, is located in the retrosternal area and may radiate to the jaw, neck, epigastrium, left shoulder, arm or the inter- scapulovertebral region, in which case, aortic dissection must be considered in the differential diagnosis. The pain is classically described as squeezing, burning, aching, tight, crushing or sharp. Symptoms most usually occur early in the morning, due to sympathetic hyperactivity  or after intense effort or distress that causes increased myocardial oxygen demand. Depending on the dimensions of the infarcted area, patients may present with low cardiac output symptoms, such as lightheadedness, syncope, sweating, dyspnea. Associated signs include anxiety, arrhythmia, nausea and vomiting (especially if the inferior wall of the left ventricle is also involved), cough and wheezing. The clinical picture allows, to some degree, outcome prediction, based on risk scores: TIMI (Thrombolysis In Myocardial Infarction) and GRACE (Global Registry of Acute Coronary Events)  .
Clinical examination may reveal cutaneous pallor or cyanosis, diaphoresis, tachycardia (or bradycardia, in cases where an atrioventricular block coexists), various atrial or ventricular arrhythmias, unequal peripheral pulses (if aortic dissection is present), hypertension (or hypotension, if the pump function is severely impaired), fever , new heart murmurs (indicating papillary muscle dysfunction or ventricular septum rupture). Right heart failure signs (jugular distension, peripheral edema, hepatomegaly, pulmonary rales) may appear if the infarcted area has ruptured. This can lead to pericardial bleeding, compression of the right ventricle, and an early death.
Posterior myocardial infarction is not an isolated event, but a progression of an inferolateral infarction. This implies that a large portion of the left ventricle is impaired and early diagnosis is imperative  .
Entire Body System
Role of endothelial shear stress in the natural history of coronary atherosclerosis and vascular remodeling: molecular, cellular, and vascular behavior. J Am Coll Cardiol. 2007 Jun 26. 49(25):2379-93. [Medline]. [medscape.com]
Chest Pain Radiating to the Arms
pain radiating into both arms. [bestbets.org]
Routine use of posterior-leads in the standard assessment of patients with chest pain may identify up to an additional 7% of STEMIs, allowing prompt reperfusion therapy, which would reduce morbidity and mortality. [ncbi.nlm.nih.gov]
The acute event in posterior myocardial infarction may be preceded by chest pain that becomes more prolonged and intense progressively and is accompanied by fatigability, malaise or no cardiovascular symptoms. [symptoma.com]
While not a definitive way to differentiate chest pain of cardiac origin from chest pain from other causes, there are factors that increase and others that decrease the likelihood of ACS. [statpearls.com]
Session Title: Acute and Stable Ischemic Heart Disease: Clinical 5 Abstract Category: 02. Acute and Stable Ischemic Heart Disease: Clinical Presentation Number: 1330-370 2019 American College of Cardiology Foundation [onlinejacc.org]
Our Specialty Centers The Johns Hopkins Ciccarone Center for the Prevention of Heart Disease takes a multidisciplinary approach to helping you prevent heart disease and stroke—and that includes getting your cholesterol in check. [hopkinsmedicine.org]
Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 10th ed. Philadelphia, PA: Elsevier Saunders; 2015. Wijnbergen I, Van't Veer M, Pijls NH, Tijssen J. [medscape.com]
Horizontal STD in leads V1 through V3, occurring in a patient with the potential for acute ischemic heart disease, should lead one to consider the diagnosis of acute PMI and employ additional investigations such as posterior thorax ECG leads. [reliasmedia.com]
Neurological exam Neurologic deficits should also raise the suspicion for aortic dissection Extremities Edema: bilateral edema can be evidence of heart failure whereas unilateral edema should prompt further evaluation for DVT and PE Pulse deficits, mottling [statpearls.com]
The electrocardiogram is a reliable method for cardiac ischemia diagnosis, but posterior myocardial infarction is not represented directly on the classical 12 lead recording : horizontal ST depression with tall R and T waves in leads V1-V3 and R/S>1 in V2 . Leads V7-V9 show the classical aspect of ST elevation and Q waves. The ST elevation is usually small, with 0.5 mm being enough to establish the diagnosis because of the increased distance between the posterior leads and the heart. 30% of posterior myocardial infarction patients also develop an atrioventricular ischemic block .
After the clinical evaluation and electrocardiogram have raised suspicion of a posterior myocardial infarction, blood tests and echocardiographic evaluation are necessary. Blood workup should include cardiac troponins I or T , total creatine kinase and its MB isoenzyme, B-type natriuretic peptide- useful for risk stratification , complete blood cell count, lipid profile and complete biochemistry (creatinine, potassium, glucose, lactate dehydrogenase, arterial blood gasses). Cardiac biomarkers should be evaluated in a dynamic manner.
Echocardiography establishes the dimension of the infarction, preexisting abnormal motion areas, the presence of complications: septum, wall or papillary muscle rupture, aneurysms, pericardial effusion or tamponade, etc.
Once the diagnosis is clear, a coronary artery angiography should be performed, with both diagnostic (to establish which artery is occluded and at which level) and therapeutic (emergency angioplasty) intent. If angioplasty is impossible, coronary angiography can establish, based on the status of the peripheral arterial bed, if coronary artery bypass is possible. Multidetector computed tomography coronary angiography is used in acute situations to determine the urgency of treatment and to detect myocardial ischemia in patients without confirmatory findings on ECG or with cardiac markers  .
Inferior Q Wave
Example #2: Old inferior Q-wave MI; note largest Q in lead III, next largest in aVF, and smallest in lead II (indicative of right coronary artery occlusion). [ecg.utah.edu]
The presence of Q waves is not always pathologic and up to 12% of healthy young men can have inferior Q waves. 14 Normal Q waves are narrow with a duration of less than 0.04 seconds, and of low amplitude of less than one-third the size of the accompanying [ahcmedia.com]
QT, RR, ST Intervals
INTRODUCTION: Isolated posterior ST-elevation myocardial infarction (STEMI) accounts for up to 7% of STEMIs. The diagnosis is suggested by indirect anterior-lead ECG changes. Confirmation requires presence of ST-elevation in posterior-leads (V7-V9). [ncbi.nlm.nih.gov]
Posterior lead placement V7, V8, V9 The degree of ST elevation seen in V7-9 is typically modest – note that only 0.5 mm of ST elevation is required to make the diagnosis of posterior MI! Example ECG Example 1a Inferolateral STEMI. [litfl.com]
Standard ECG: Posterior ECG: Standard ECG: ST elevation in II, III, aVF (inferior) V5, V6 (lateral) with prominent ST depression in V1-V3 and R S in V2 Posterior ECG: ST elevation in V7-V9 Don’t confuse with RV infarction- - ST elevation in inferior leads [emdaily.cooperhealth.org]
Jugular Venous Pressure
A common theory is that prominent R-waves may actually represent inverted Q-waves.1,8 Interestingly, over a third of patients had prominent R-waves in either V1 or V2. [bjcardio.co.uk]
The additional findings of upright T waves and prominent R waves in the same leads suggested posterior wall ST segment elevation AMI. [journals.lww.com]
R waves in V1-V3, R/S wave ratio 1.0 in lead V2, upright T-waves in V1-V3, often coexisting inferior or lateral MI. [errolozdalga.com]
R waves are observed in the right precordial leads. [reliasmedia.com]
 R/S wave ratio 1.0 in lead V2 Co-existing acute, inferior, and/or lateral MI Limited to leads V1 – V3: ST-segment depression (horizontal moreso than downsloping or upsloping) Prominent R wave Prominent, upright T wave Combination of horizontal ST-segment [foamem.com]
Other ECG Findings
- Wijnbergen I, Van't Veer M, Pijls NH, et al. Circadian and weekly variation and the influence of environmental variables in acute myocardial infarction. Neth Heart J. 2012;20(9):354-9.
- Amsterdam EA, Wenger NK, Brindis RG, et al. 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. 2014;130(25):e344-426.
- Roffi M, Patrono C, Collet JP, et al. 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation: Task Force for the Management of Acute Coronary Syndromes in Patients Presenting without Persistent ST-Segment Elevation of the European Society of Cardiology (ESC). Eur Heart J. 2016;37 (3):267-315.
- Patel MR, Mahaffey KW, Armstrong PW, et al. Prognostic usefulness of white blood cell count and temperature in acute myocardial infarction (from the CARDINAL Trial). Am J Cardiol. 2005;95 (5):614-618.
- Oraii S, Maleki M, Abbas Tavakolian A, et al. Prevalence and outcome of ST-segment elevation in posterior electrocardiographic leads during acute myocardial infarction. J Electrocardiol 1999;32: 275-278.
- Matetzky S, Freimark D, Chouraqui P, et al. Significance of ST segment elevations in posterior chest leads (V7 to V9) in patients with acute inferior myocardial infarction: application for thrombolytic therapy. J Am Coll Cardiol 1998;31:506-511.
- Rich M, Imburgia M, King T, et al. Electrocardiographic diagnosis of remote posterior wall myocardial infarction using unipolar posterior lead V9 Chest 1989;96:489-493.
- Boden E, Kleiger R, Gibson R, et al. Electrocardiographic evolution of posterior acute myocardial infarction: Importance of early precordial ST-segment depression. Am J Cardiol 1987;59:782-787.
- Eisenstein I, Sanmarco M, Madrid W, et al. Electrocardiographic and vectorcardiographic diagnosis of posterior wall myocardial infarction. Chest 1988;3:409-416
- Mueller C. Biomarkers and acute coronary syndromes: an update. Eur Heart J. 2014;35(9):552-556.
- Haaf P, Reichlin T, Corson N, et al. B-type natriuretic peptide in the early diagnosis and risk stratification of acute chest pain. Am J Med. 2011;124 (5):444-52.
- Goldstein JA, Chinnaiyan KM, Abidov A, et al, for the CT-STAT Investigators. The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) trial. J Am Coll Cardiol. 2011;58 (14):1414-1422.
- Samad Z, Hakeem A, Mahmood SS, et al. A meta-analysis and systematic review of computed tomography angiography as a diagnostic triage tool for patients with chest pain presenting to the emergency department. J Nucl Cardiol. 2012;19 (2):364-376.