Leads aVL and aVF of an electrocardiogram showing atrial fibrillation. There are irregular intervals between heart beats. No P waves are seen and there is an erratic baseline between QRS complexes. The heart rate is about 125 beats per minute.
3D rendering showing thick myocardium within the heart wall.
Normal rhythm tracing (top) Atrial fibrillation (bottom)
The swirling musculature of the heart ensures effective pumping of blood.
How a stroke can occur during atrial fibrillation
Cardiac muscle
Non-modifiable risk factors (top left box) and modifiable risk factors (bottom left box) for atrial fibrillation. The main outcomes of atrial fibrillation are in the right box. BMI=Body Mass Index.
Illustration of a cardiac muscle cell.
A 12-lead ECG showing atrial fibrillation at approximately 132 beats per minute
Intercalated discs are part of the cardiac muscle cell sarcolemma and they contain gap junctions and desmosomes.
Diagram of normal sinus rhythm as seen on ECG. In atrial fibrillation the P waves, which represent depolarization of the top of the heart, are absent.
Dog cardiac muscle (400X)
ECG of atrial fibrillation (top) and normal sinus rhythm (bottom). The purple arrow indicates a P wave, which is lost in atrial fibrillation.
3D Medical Animation still shot of Left Atrial Appendage Occlusion

All of these mutations affect the processes of polarization-depolarization of the myocardium, cellular hyper-excitability, shortening of effective refractory period favoring re-entries.

- Atrial fibrillation

Certain ion currents such as IK(UR) are highly specific to atrial cardiomyocytes, making them a potential target for treatments for atrial fibrillation.

- Cardiac muscle

6 related topics with Alpha

Overall

A man with congestive heart failure and marked jugular venous distension. External jugular vein marked by an arrow.

Heart failure

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Set of manifestations caused by the failure of the heart's function as a pump supporting the blood flow through the body.

Set of manifestations caused by the failure of the heart's function as a pump supporting the blood flow through the body.

A man with congestive heart failure and marked jugular venous distension. External jugular vein marked by an arrow.
Signs and symptoms of severe heart failure
Severe peripheral pitting edema
Kerley B lines in acute cardiac decompensation. The short, horizontal lines can be found everywhere in the right lung.
Model of a normal heart (left); and a weakened heart, with over-stretched muscle and dilation of left ventricle (right); both during diastole
Chest radiograph of a lung with distinct Kerley B lines, as well as an enlarged heart (as shown by an increased cardiothoracic ratio, cephalization of pulmonary veins, and minor pleural effusion as seen for example in the right horizontal fissure. Yet, no obvious lung edema is seen. Overall, this indicates intermediate severity (stage II) heart failure.
Siderophages (one indicated by white arrow) and pulmonary congestion, indicating left congestive heart failure
Ultrasound showing severe systolic heart failure
Congestive heart failure with small bilateral effusions
Kerley B lines

Common causes of heart failure include coronary artery disease, including a previous myocardial infarction (heart attack), high blood pressure, atrial fibrillation, valvular heart disease, excess alcohol use, infection, and cardiomyopathy of an unknown cause.

Heart failure may be the result of coronary artery disease, and its prognosis depends in part on the ability of the coronary arteries to supply blood to the myocardium (heart muscle).

A myocardial infarction occurs when an atherosclerotic plaque slowly builds up in the inner lining of a coronary artery and then suddenly ruptures, causing catastrophic thrombus formation, totally occluding the artery and preventing blood flow downstream.

Myocardial infarction

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A myocardial infarction occurs when an atherosclerotic plaque slowly builds up in the inner lining of a coronary artery and then suddenly ruptures, causing catastrophic thrombus formation, totally occluding the artery and preventing blood flow downstream.
Cross section showing anterior left ventricle wall infarction
Diagram showing the blood supply to the heart by the two major blood vessels, the left and right coronary arteries (labelled LCA and RCA). A myocardial infarction (2) has occurred with blockage of a branch of the left coronary artery (1).
A 12-lead ECG showing an inferior STEMI due to reduced perfusion through the right coronary artery. Elevation of the ST segment can be seen in leads II, III and aVF.
ECG : AMI with ST elevation in V2-4
Inserting a stent to widen the artery.

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.

Other ECG abnormalities relating to complications of acute myocardial infarctions may also be evident, such as atrial or ventricular fibrillation.

Ventricular fibrillation (VF) showing disorganized electrical activity producing a spiked tracing on an electrocardiogram (ECG)

Arrhythmia

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Too fast or too slow.

Too fast or too slow.

Ventricular fibrillation (VF) showing disorganized electrical activity producing a spiked tracing on an electrocardiogram (ECG)
Broad classification of arrhythmias according to region of heart required to sustain the rhythm
Normal sinus rhythm, with solid black arrows pointing to normal P waves representative of normal sinus node function, followed by a pause in sinus node activity (resulting in a transient loss of heartbeats). Note that the P wave that disrupts the pause (indicated by the dashed arrow) does not look like the previous (normal) P waves – this last P wave is arising from a different part of the atrium, representing an escape rhythm.

Supraventricular tachycardias include atrial fibrillation, atrial flutter and paroxysmal supraventricular tachycardia.

Automaticity refers to a cardiac muscle cell firing off an impulse on its own.

Vascular ischemia of the toes with characteristic cyanosis

Ischemia

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Restriction in blood supply to any tissues, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism .

Restriction in blood supply to any tissues, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism .

Vascular ischemia of the toes with characteristic cyanosis
Native records of contractile activity of the left ventricle of isolated rat heart perfused under Langendorff technique. Curve A - contractile function of the heart is greatly depressed after ischemia-reperfusion. Curve B - a set of short ischemic episodes (ischemic preconditioning) before prolonged ischemia provides functional recovery of contractile activity of the heart at reperfusion.

It occurs when the heart muscle, or myocardium, receives insufficient blood flow.

Other causes are heart conditions including myocardial infarction, mitral valve disease, chronic atrial fibrillation, cardiomyopathies, and prosthesis, in all of which thrombi are prone to develop.

Mouse heart slice showing dilated cardiomyopathy

Dilated cardiomyopathy

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Condition in which the heart becomes enlarged and cannot pump blood effectively.

Condition in which the heart becomes enlarged and cannot pump blood effectively.

Mouse heart slice showing dilated cardiomyopathy
Illustration of a Normal Heart vs. Heart with Dilated Cardiomyopathy
Serial 12-lead ECGs from a 49-year-old black man with cardiomyopathy. (TOP): Sinus tachycardia (rate about 101/min) with LBBB accompanied by RAD (here about 108°). Frequent multifocal PVCs (both singly and in pairs) and left atrial enlargement. (BOTTOM): Same patient about 5 months later status-post orthotopic heart transplant.
Dilated cardiomyopathy on CXR
Dilated cardiomyopathy on CT

It is a type of cardiomyopathy, a group of diseases that primarily affects the heart muscle.

As a result, those with DCM are at increased risk of atrial fibrillation.

MRI video of a teen's heart beating.

Cardiac cycle

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Performance of the human heart from the beginning of one heartbeat to the beginning of the next.

Performance of the human heart from the beginning of one heartbeat to the beginning of the next.

MRI video of a teen's heart beating.
MRI video of a teen's heart beating.
The cycle diagram depicts one heartbeat of the continuously repeating cardiac cycle, namely: ventricular diastole followed by ventricular systole, etc.—while coordinating with atrial systole followed by atrial diastole, etc. The cycle also correlates to key electrocardiogram tracings: the T wave (which indicates ventricular diastole); the P wave (atrial systole); and the QRS 'spikes' complex (ventricular systole)—all shown as color purple-in-black segments.
The Cardiac Cycle: Valve Positions, Blood Flow, and ECG
The parts of a QRS complex and adjacent deflections. Re the cardiac cycle, atrial systole begins at the P wave; ventricular systole begins at the Q deflection of the QRS complex.
A Wiggers diagram illustrate events and details of the cardiac cycle with electrographic trace lines, which depict (vertical) changes in a parameter's value as time elapses left-to-right. The ventricular "Diastole", or relaxation, begins with "Isovolumic relaxation", then proceeds through three sub-stages of inflow, namely: "Rapid inflow", "Diastasis", and "Atrial systole". (During the "Diastole" period, the "Ventricular volume" increases (see red-line tracing), beginning after the vertical bar at "Aortic valve closes" and ending with the vertical bar at R in the QRS complex). + The ventricular "Systole", or contraction, begins with "Isovolumic contraction", i.e., with the vertical bar at "A -V valve closes"; it ends with completing the "Ejection" stage at the bar at "Aortic valve closes". During "Ejection" stage, the (red-line) tracing of "Ventricular volume" falls to its least amount (see ejection fraction) as the ventricles pump blood to the pulmonary arteries and to the aorta.
Diastole (at right) normally refers to atria and ventricles at relaxation and expansion together—while refilling with blood returning to the heart. Systole (left) typically refers to ventricular systole, during which the ventricles are pumping (or ejecting) blood out of the heart through the aorta and the pulmonary veins.
CGI animated graphic of the human heart, sectioned, with motions and timing synced with the Wiggers diagram. The section shows: 1) the opened ventricles contracting once per heartbeat—that is, once per each cardiac cycle; 2) the (partly obscured) mitral valve of the left heart; 3) the tricuspid and pulmonary valves of the right heart—note these paired valves open and close oppositely. + (The aortic valve of the left heart is located below the pulmonary valve, and is completely obscured.) The (unsectioned) atria are seen above the ventricles.
Cardiac diastole: Both AV valves (tricuspid in the right heart (light-blue), mitral in the left heart (pink)) are open to enable blood to flow directly into both left and right ventricles, where it is collected for the next contraction.
Cardiac (ventricular) systole: Both AV valves (tricuspid in the right heart (light-blue), mitral in the left heart (pink)) are closed by back-pressure as the ventricles are contracted and their blood volumes are ejected through the newly-opened pulmonary valve (dark-blue arrow) and aortic valve (dark-red arrow) into the pulmonary trunk and aorta respectively.

The movements of cardiac muscle are coordinated by a series of electrical impulses produced by specialised pacemaker cells found within the sinoatrial node and the atrioventricular node.

Atrial kick is absent or disrupted if there is loss of normal electrical conduction in the heart, such as caused by atrial fibrillation, atrial flutter, or heart block.