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  .
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  .