A myocardial infarction may compromise the function of the heart as a pump for the circulation, a state called heart failure. There are different types of heart failure; left- or right-sided (or bilateral) heart failure may occur depending on the affected part of the heart, and it is a low-output type of failure. If one of the heart valves is affected, this may cause dysfunction, such as mitral regurgitation in the case of left-sided coronary occlusion that disrupts the blood supply of the papillary muscles. The incidence of heart failure is particularly high in patients with diabetes and requires special management strategies.

Myocardial infarction complications may occur immediately following a heart attack (in the acute phase), or may need time to develop (a chronic problem). After an infarction, an obvious complication is a second infarction, which may occur in the domain of another atherosclerotic coronary artery, or in the same zone if there are any live cells left in the infarct.

Signs and symptoms of ischemic cardiomyopathy include sudden fatigue, shortness of breath, dizziness and palpitations.

PVF is defined as ventricular fibrillation not preceded by heart failure or shock, in contrast to secondary ventricular fibrillation, which is.

An electrocardiogram helps establishing the exact diagnosis and guides treatment, it may reveal:

- Abnormal heart rhythms, such as bradycardia (slowed heart rate)

- myocardial infarction (ST-elevation MI, STEMI, is usually more dangerous than non-STEMIs; MIs that affect the ventricles are usually more dangerous than those that affect the atria; those affecting the left side of the heart, especially the left ventricle, are usually more dangerous than those affecting the right side, unless that side is severely compromised)

- Signs of cardiomyopathy

Approximately 10% of all myocardial infarctions lead to PVF. The incidence peaks between 20 and 50 minutes after the start of the MI. 2/3 of events occur before medical attendance, and of these medically unattended events, 2/3 occur after more than 30 minutes of warning symptoms.

Also known as 'effort angina', this refers to the classic type of angina related to myocardial ischemia. A typical presentation of stable angina is that of chest discomfort and associated symptoms precipitated by some activity (running, walking, etc.) with minimal or non-existent symptoms at rest or after administration of sublingual nitroglycerin. Symptoms typically abate several minutes after activity and recur when activity resumes. In this way, stable angina may be thought of as being similar to intermittent claudication symptoms. Other recognized precipitants of stable angina include cold weather, heavy meals, and emotional stress.

Ischemic cardiomyopathy is a type of cardiomyopathy caused by a narrowing of the coronary arteries which supply blood to the heart. Typically, patients with ischemic cardiomyopathy have a history of acute myocardial infarction, however, it may occur in patients with coronary artery disease, but without a past history of acute myocardial infarction. This cardiomyopathy is one of the leading causes of sudden cardiac death.

Unstable angina (UA) (also ""crescendo angina""; this is a form of acute coronary syndrome) is defined as angina pectoris that changes or worsens.

It has at least one of these three features:

1. it occurs at rest (or with minimal exertion), usually lasting more than 10 minutes

2. it is severe and of new onset (i.e., within the prior 4–6 weeks)

3. it occurs with a crescendo pattern (i.e., distinctly more severe, prolonged, or frequent than before).

UA may occur unpredictably at rest, which may be a serious indicator of an impending heart attack. What differentiates stable angina from unstable angina (other than symptoms) is the pathophysiology of the atherosclerosis. The pathophysiology of unstable angina is the reduction of coronary flow due to transient platelet aggregation on apparently normal endothelium, coronary artery spasms, or coronary thrombosis. The process starts with atherosclerosis, progresses through inflammation to yield an active unstable plaque, which undergoes thrombosis and results in acute myocardial ischemia, which, if not reversed, results in cell necrosis (infarction). Studies show that 64% of all unstable anginas occur between 22:00 and 08:00 when patients are at rest.

In stable angina, the developing atheroma is protected with a fibrous cap. This cap may rupture in unstable angina, allowing blood clots to precipitate and further decrease the area of the coronary vessel's lumen. This explains why, in many cases, unstable angina develops independently of activity.

Echocardiography may show poor ventricular function, signs of PED, rupture of the interventricular septum, an obstructed outflow tract or cardiomyopathy.

The left side of the heart is responsible for receiving oxygen-rich blood from the lungs and pumping it forward to the systemic circulation (the rest of the body except for the pulmonary circulation). Failure of the left side of the heart causes blood to back up (be congested) into the lungs, causing respiratory symptoms as well as fatigue due to insufficient supply of oxygenated blood. Common respiratory signs are increased rate of breathing and increased "work" of breathing (non-specific signs of respiratory distress). Rales or crackles, heard initially in the lung bases, and when severe, throughout the lung fields suggest the development of pulmonary edema (fluid in the alveoli). Cyanosis which suggests severe low blood oxygen, is a late sign of extremely severe pulmonary edema.

Additional signs indicating left ventricular failure include a laterally displaced apex beat (which occurs if the heart is enlarged) and a gallop rhythm (additional heart sounds) may be heard as a marker of increased blood flow or increased intra-cardiac pressure. Heart murmurs may indicate the presence of valvular heart disease, either as a cause (e.g. aortic stenosis) or as a result (e.g. mitral regurgitation) of the heart failure.

"Backward" failure of the left ventricle causes congestion of the lungs' blood vessels, and so the symptoms are predominantly respiratory in nature. Backward failure can be subdivided into the failure of the left atrium, the left ventricle or both within the left circuit. The patient will have dyspnea (shortness of breath) on exertion and in severe cases, dyspnea at rest. Increasing breathlessness on lying flat, called orthopnea, occurs. It is often measured in the number of pillows required to lie comfortably, and in orthopnea, the patient may resort to sleeping while sitting up. Another symptom of heart failure is paroxysmal nocturnal dyspnea: a sudden nighttime attack of severe breathlessness, usually several hours after going to sleep. Easy fatigability and exercise intolerance are also common complaints related to respiratory compromise.

"Cardiac asthma" or wheezing may occur.

Compromise of left ventricular "forward" function may result in symptoms of poor systemic circulation such as dizziness, confusion and cool extremities at rest.

Heart failure symptoms are traditionally and somewhat arbitrarily divided into "left" and "right" sided, recognizing that the left and right ventricles of the heart supply different portions of the circulation. However, heart failure is not exclusively "backward failure" (in the part of the circulation which drains to the ventricle).

There are several other exceptions to a simple left-right division of heart failure symptoms. Additionally, the most common cause of right-sided heart failure is left-sided heart failure. The result is that patients commonly present with both sets of signs and symptoms.

Unstable angina (UA) is a type of angina pectoris that is irregular. It is also classified as a type of acute coronary syndrome (ACS).

It can be difficult to distinguish unstable angina from non-ST elevation (non-Q wave) myocardial infarction (NSTEMI). They differ primarily in whether the ischemia is severe enough to cause sufficient damage to the heart's muscular cells to release detectable quantities of a marker of injury (typically troponin T or troponin I). Unstable angina is considered to be present in patients with ischemic symptoms suggestive of an ACS and no elevation in troponin, with or without ECG changes indicative of ischemia (e.g., ST segment depression or transient elevation or new T wave inversion). Since an elevation in troponin may not be detectable for up to 12 hours after presentation, UA and NSTEMI are frequently indistinguishable at initial evaluation.

Chest pain is a major indication of coronary ischemia. If chest pain occurs while exercising, or during sex, but it doesn't persist after rest, it may be coronary ischemia, or what is called, "angina". Some people characterize the pain they feel as though an elephant is sitting on their chest.

Other typical symptoms include diaphoresis which is sweaty palms, and clammy skin, nausea or vomiting, or shortness of breath. Chest pain radiating down the left arm is also a symptom of coronary ischemia and the pain can also be radiating directly to the back in some instances.

Dressler syndrome was, historically, a phenomenon complicating about 7% of myocardial infarctions; however, in the era of percutaneous coronary intervention, it is very uncommon. The disease consists of a persistent low-grade fever, chest pain (usually pleuritic in nature), pericarditis (usually evidenced by a pericardial friction rub), and/or a pericardial effusion. The symptoms tend to occur 2–3 weeks after myocardial infarction, but can also be delayed for a few months. It tends to subside in a few days, and very rarely leads to pericardial tamponade. An elevated ESR is an objective, yet nonspecific, laboratory finding.

Coronary ischemia is a medical term for not having enough blood through the coronary arteries. Coronary ischemia is linked to heart disease as well as heart attacks. It is also known as cardiac ischemia.

Hemopericardium refers to blood in the pericardial sac of the heart. It is clinically similar to a pericardial effusion, and, depending on the volume and rapidity with which it develops, may cause cardiac tamponade.

The condition can be caused by full-thickness necrosis (death) of the myocardium (heart muscle) after myocardial infarction, chest trauma, and by over-prescription of anticoagulants. Other causes include ruptured aneurysm of sinus of Valsalva and other aneurysms of the aortic arch.

Hemopericardium can be diagnosed with a chest X-ray or a chest ultrasound, and is most commonly treated with pericardiocentesis. While hemopericardium itself is not deadly, it can lead to cardiac tamponade, a condition that is fatal if left untreated.

Chest pain is the most common symptom of acute myocardial infarction and is often described as a sensation of tightness, pressure, or squeezing. Pain radiates most often to the left arm, but may also radiate to the lower jaw, neck, right arm, back, and upper abdomen. The pain most suggestive of an acute MI, with the highest likelihood ratio, is pain radiating to the right arm and shoulder. Similarly, chest pain similar to a previous heart attack is also suggestive. The pain associated with MI is usually diffuse, does not change with position, and lasts for more than 20 minutes. Levine's sign, in which a person localizes the chest pain by clenching one or both fists over their sternum, has classically been thought to be predictive of cardiac chest pain, although a prospective observational study showed it had a poor positive predictive value. Pain that responds to nitroglycerin does not indicate the presence or absence of a myocardial infarction.

The pathophysiology of unstable angina is controversial. Until recently, unstable angina was assumed to be angina pectoris caused by disruption of an atherosclerotic plaque with partial thrombosis and possibly embolization or vasospasm leading to myocardial ischemia. However, sensitive troponin assays reveal rise of cardiac troponin in the bloodstream with episodes of even mild myocardial ischemia. Since unstable angina is assumed to occur in the setting of acute myocardial ischemia without troponin release, the concept of unstable angina is being questioned with some calling for retiring the term altogether.

Symptoms of myocardial rupture are recurrent or persistent chest pain, syncope, and distension of jugular vein. Sudden death caused by a myocardial rupture is sometimes preceded by no symptoms.

Myocardial infarction (MI) refers to tissue death (infarction) of the heart muscle (myocardium). It is a type of acute coronary syndrome, which describes a sudden or short-term change in symptoms related to blood flow to the heart. Unlike other causes of acute coronary syndromes, such as unstable angina, a myocardial infarction occurs when there is cell death, as measured by a blood test for biomarkers (the cardiac protein troponin or the cardiac enzyme CK-MB). When there is evidence of an MI, it may be classified as an ST elevation myocardial infarction (STEMI) or Non-ST elevation myocardial infarction (NSTEMI) based on the results of an ECG.

The phrase "heart attack" is often used non-specifically to refer to a myocardial infarction and to sudden cardiac death. An MI is different from—but can cause—cardiac arrest, where the heart is not contracting at all or so poorly that all vital organs cease to function, thus causing death. It is also distinct from heart failure, in which the pumping action of the heart is impaired. However, an MI may lead to heart failure.

The typical presentation of takotsubo cardiomyopathy is a sudden onset of chest pain associated with ECG changes mimicking a myocardial infarction of the anterior wall. During the course of evaluation of the patient, a bulging out of the left ventricular apex with a hypercontractile base of the left ventricle is often noted. It is the hallmark bulging out of the apex of the heart with preserved function of the base that earned the syndrome its name "tako tsubo", or octopus pot in Japan, where it was first described.

Stress is the main factor in takotsubo cardiomyopathy, with more than 85% of cases set in motion by either a physically or emotionally stressful event that prefaces the start of symptoms. Examples of emotional stressors include grief from the death of a loved one, fear of public speaking, arguing with a spouse, relationship disagreements, betrayal, and financial problems. Acute asthma, surgery, chemotherapy, and stroke are examples of physical stressors. In a few cases, the stress may be a happy event, such as a wedding, winning a jackpot, a sporting triumph, or a birthday.

Takotsubo cardiomyopathy is more commonly seen in postmenopausal women. Often there is a history of a recent severe (usually negative, sometimes happy) emotional or physical stress.

Left ventricular thrombus is a blood clot (thrombus) in the left ventricle of the heart. LVT is a common complication of acute myocardial infarction (AMI). Typically the clot is a mural thrombus, meaning it is on the wall of the ventricle. The primary risk of LVT is the occurrence of cardiac embolism, in which the thrombus detaches from the ventricular wall and travels through the circulation and blocks blood vessels. Blockage can be especially damaging in the heart or brain (stroke).

Dressler syndrome needs to be differentiated from pulmonary embolism, another identifiable cause of pleuritic (and non-pleuritic) chest pain in people who have been hospitalized and/or undergone surgical procedures within the preceding weeks.

Symptoms of hemopericardium often include difficulty breathing, abnormally rapid breathing, and fatigue, each of which can be a sign of a serious medical condition not limited to hemopericardium. In many cases, patients also report feeling chest pressure and have an abnormally elevated heart rate.