Myocardial infarction complications may occur immediately following a

heart attack A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may tr ...

(in the

acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology * Acute (medicine), a disease that it is of short duration and of recent onset. ** Acute toxicity, the adverse eff ...

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. Post-myocardial complications occur after a period of ischemia, these changes can be seen in gross tissue changes and microscopic changes. Necrosis begins after 20 minutes of an infarction. Under 4 hours of ischemia, there are no gross or microscopic changes noted.Kumar, V., Abbas, A. K., & Aster, J. C. (2015). Robbins and Cotran pathologic basis of disease (Ninth edition.). Philadelphia, PA: Elsevier/Saunders. From 4-24 hours

coagulative necrosis Coagulative necrosis is a type of accidental cell death typically caused by ischemia or infarction. In coagulative necrosis, the architectures of dead tissue are preserved for at least a couple of days. It is believed that the injury denatures stru ...

begins to be seen, which is characterized by the removal of dead

cardiomyocytes Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle tha ...

through heterolysis and the nucleus through karyorrhexis, karyolysis, and pyknosis. On gross examination, coagulative necrosis shows darkened discoloration of the infarcted tissue. The most common complication during this period is arrhythmias. Day 1-7 is marked by the inflammatory phase. Days 1-3 are marked by “acute inflammation”, in which neutrophils infiltrate the ischemic tissue. A major complication during this period is fibrinous pericarditis, particularly in transmural ventricular wall damage (an infarct that impacted all 3 layers of the heart, the epicardium, myocardium, and endocardium). This leads to inflammation, such as swelling, leading to rubbing of the heart on the pericardium. Day 4 through 7 are marked by “chronic inflammation”, on histology macrophages will be seen infiltrating the tissue. The role of these macrophages is the removal of necrotic myocytes. However, these cells are directly involved in the weakening of the tissue, leading to complications such as a ventricular free wall rupture, intraventricular septum rupture, or a papillary muscle rupture. At a gross anatomical level, this staged is marked by a yellow pallor. Weeks 1-3 are marked on histology by abundant capillaries, and fibroblast infiltration. Fibroblasts start replacing the lost cardiomyocytes with collagen type 1 and leads to the granulation of tissue. After several weeks fibrosis occurs and heavy collagen formation. Collagen is not as strong or compliant as the myocardium that it replaced, this instability could lead to a ventricular aneurysm, and the stasis of blood in an aneurysm can lead to a mural thrombus. A rarer complication that also occurs during this time is Dressler's syndrome and is thought to have autoimmune origins.

Congestive heart failure

A myocardial infarction may compromise the function of the heart as a pump for the circulation, a state called

heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...

. 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 rupture

Myocardial rupture Myocardial rupture is a laceration of the ventricles or atria of the heart, of the interatrial or interventricular septum, or of the papillary muscles. It is most commonly seen as a serious sequela of an acute myocardial infarction (heart atta ...

is most common three to seven days after myocardial infarction, commonly of small degree, but may occur one day to three weeks later. In the modern era of early revascularization and intensive pharmacotherapy as treatment for MI, the incidence of myocardial rupture is about 1% of all MIs. This may occur in the free walls of the ventricles, the

septum In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatri ...

between them, the

papillary muscles The papillary muscles are muscles located in the ventricles of the heart. They attach to the cusps of the atrioventricular valves (also known as the mitral and tricuspid valves) via the chordae tendineae and contract to prevent inversion or pr ...

, or less commonly the atria. Rupture occurs because of increased pressure against the weakened walls of the heart chambers due to heart muscle that cannot pump blood out effectively. The weakness may also lead to ventricular

aneurysm An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also be a nidus (s ...

, a localized dilation or ballooning of the heart chamber. Risk factors for myocardial rupture include completion of infarction (no revascularization performed), female sex, advanced age, and a lack of a previous history of myocardial infarction. In addition, the risk of rupture is higher in individuals who are revascularized with a thrombolytic agent than with PCI. The shear stress between the infarcted segment and the surrounding normal myocardium (which may be hypercontractile in the post-infarction period) makes it a nidus for rupture. Rupture is usually a catastrophic event that may result a life-threatening process known as

cardiac tamponade Cardiac tamponade, also known as pericardial tamponade (), is the buildup of fluid in the pericardium (the sac around the heart), resulting in compression of the heart. Onset may be rapid or gradual. Symptoms typically include those of obstructi ...

, in which blood accumulates within the

pericardium The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...

or heart sac, and compresses the heart to the point where it cannot pump effectively. Rupture of the intraventricular septum (the muscle separating the left and right ventricles) causes a

ventricular septal defect A ventricular septal defect (VSD) is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart. The extent of the opening may vary from pin size to complete absence of the ventricular septum, creating one ...

with shunting of blood through the defect from the left side of the heart to the right side of the heart, which can lead to right ventricular failure as well as pulmonary overcirculation. Rupture of the papillary muscle may also lead to acute mitral regurgitation and subsequent

pulmonary edema Pulmonary edema, also known as pulmonary congestion, is excessive edema, liquid accumulation in the parenchyma, tissue and pulmonary alveolus, air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia an ...

and possibly even cardiogenic shock.

Arrhythmia

Electrocardiogram of Ventricular Tachycardia

Since the electrical characteristics of the infarcted tissue change (see pathophysiology section),

arrhythmias Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...

are a frequent complication. The re-entry phenomenon may cause rapid heart rates (

ventricular tachycardia Ventricular tachycardia (V-tach or VT) is a fast heart rate arising from the lower chambers of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period ...

and even

ventricular fibrillation Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart quiver. It is due to disorganized electrical activity. Ventricular fibrillation results in cardiac arrest with loss of consciousness and no p ...

), and ischemia in the

electrical conduction system of the heart The cardiac conduction system (CCS) (also called the electrical conduction system of the heart) transmits the signals generated by the sinoatrial node – the heart's pacemaker, to cause the heart muscle to contract, and pump blood through ...

may cause a

complete heart block Third-degree atrioventricular block (AV block) is a medical condition in which the electrical impulse generated in the sinoatrial node (SA node) in the atrium of the heart can not propagate to the ventricles. Because the impulse is blocked, an a ...

(when the impulse from the

sinoatrial node The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is an oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of cells known as pacemaker cells. The sinus node is approxima ...

, the normal cardiac pacemaker, does not reach the heart chambers).

Pericarditis

As a reaction to the damage of the heart muscle, inflammatory cells are attracted. The inflammation may reach out and affect the heart sac. This is called pericarditis. In

Dressler's syndrome Dressler syndrome is a secondary form of pericarditis that occurs in the setting of injury to the heart or the pericardium (the outer lining of the heart). It consists of fever, pleuritic pain, pericarditis and/or a pericardial effusion. Dressle ...

, this occurs several weeks after the initial event. If pericarditis were to persist, pericardial effusion may also occur which could in turn lead to cardiac tamponade if not properly treated.

Cardiogenic shock

A complication that may occur in the acute setting soon after a myocardial infarction or in the weeks following is cardiogenic shock. Cardiogenic shock is defined as a hemodynamic state in which the heart cannot produce enough of a

cardiac output In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols Q, \dot Q, or \dot Q_ , edited by Catherine E. Williamson, Phillip Bennett is the volumetric flow rate of the heart's pumping output: t ...

to supply an adequate amount of oxygenated blood to the tissues of the body. While the data on performing interventions on individuals with cardiogenic shock is sparse, trial data suggests a long-term mortality benefit in undergoing revascularization if the individual is less than 75 years old and if the onset of the acute myocardial infarction is less than 36 hours and the onset of cardiogenic shock is less than 18 hours. If the patient with cardiogenic shock is not going to be revascularized, aggressive hemodynamic support is warranted, with insertion of an

intra-aortic balloon pump The intra-aortic balloon pump (IABP) is a mechanical device that increases myocardial oxygen perfusion and indirectly increases cardiac output through afterload reduction. It consists of a cylindrical polyurethane balloon that sits in the aorta ...

if not contraindicated. If diagnostic coronary angiography does not reveal a culprit blockage that is the cause of the cardiogenic shock, the prognosis is poor.

Congestive heart failure

Myocardial rupture

Arrhythmia

Pericarditis

Cardiogenic shock

References

Further reading