Women are more likely to have unusual or unexplained tiredness and nausea or vomiting as symptoms. Women having heart attacks are more likely to have palpitations, back pain, labored breath, vomiting, and left arm pain than men, although the studies showing these differences had high variability. Women are less likely to report chest pain during a heart attack and more likely to report nausea, jaw pain, neck pain, cough, and fatigue, although these findings are inconsistent across studies. Women with heart attacks also had more indigestion, dizziness, loss of appetite, and loss of consciousness. Shortness of breath is a common, and sometimes the only symptom, occurring when damage to the heart limits the output of the left ventricle, with breathlessness arising either from low oxygen in the blood, or pulmonary edema. Other less common symptoms include weakness, light-headedness, palpitations, and abnormalities in heart rate or blood pressure. These symptoms are likely induced by a massive surge of catecholamines from the sympathetic nervous system, which occurs in response to pain and, where present, low blood pressure. Loss of consciousness due to inadequate blood flow to the brain and cardiogenic shock, and sudden death, frequently due to the development of ventricular fibrillation, can occur in myocardial infarctions. Cardiac arrest, and atypical symptoms such as palpitations, occur more frequently in women, the elderly, those with diabetes, in people who have just had surgery, and in critically ill patients. Absence
"Silent" myocardial infarctions can happen without any symptoms at all.
Early STEMIs may be preceded by peaked T waves. Other ECG abnormalities relating to complications of acute myocardial infarctions may also be evident, such as atrial or ventricular fibrillation. Imaging
Noninvasive imaging plays an important role in the diagnosis and characterisation of myocardial infarction. Tests such as chest X-rays can be used to explore and exclude alternate causes of a persons symptoms. Echocardiography may assist in modifying clinical suspicion of ongoing myocardial infarction in patients that cant be ruled out or ruled in following initial ECG and Troponin testing. Myocardial perfusion imaging has no role in the acute diagnostic algorithm, however it can confirm a clinical suspicion of Chronic Coronary Syndrome when the patients history, physical examination (including cardiac examination) ECG, and cardiac biomarkers suggest coronary artery disease.Echocardiography, an ultrasound scan of the heart, is able to visualize the heart, its size, shape, and any abnormal motion of the heart walls as they beat that may indicate a myocardial infarction. The flow of blood can be imaged, and contrast dyes may be given to improve image. Other scans using radioactive contrast include SPECT CT-scans using thallium, sestamibi (MIBI scans) or tetrofosmin; or a PET scan using Fludeoxyglucose or rubidium-82. These nuclear medicine scans can visualize the perfusion of heart muscle.