Cardiology is the study of the heart. Cardiology is a branch of medicine that deals with disorders of the heart and the cardiovascular system. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease, and electrophysiology. Physicians who specialize in this field of medicine are called cardiologists, a specialty of internal medicine. Pediatric cardiologists are pediatricians who specialize in cardiology. Physicians who specialize in cardiac surgery are called cardiothoracic surgeons or cardiac surgeons, a specialty of general surgery.
Bradycardia, also called bradyarrhythmia, is a resting heart rate under 60 beats per minute (BPM). While bradycardia can result from various pathologic processes, it is commonly a physiologic response to cardiovascular conditioning or due to asymptomatic type 1 atrioventricular block. Resting heart rates of less than 50 BPM are often normal during sleep in young and healthy adults and athletes. In large population studies of adults without underlying heart disease, resting heart rates of 45-50 BPM appear to be the lower limits of normal, dependent on age and sex. Bradycardia is most likely to be discovered in the elderly, as age and underlying cardiac disease progression contribute to its development.
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to the lungs. In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest, called the mediastinum.
Electrocardiography is the process of producing an electrocardiogram, a recording of the heart's electrical activity through repeated cardiac cycles. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat). Changes in the normal ECG pattern occur in numerous cardiac abnormalities, including:
Cardioversion is a medical procedure by which an abnormally fast heart rate (tachycardia) or other cardiac arrhythmia is converted to a normal rhythm using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart at a specific moment in the cardiac cycle, restoring the activity of the electrical conduction system of the heart. Pharmacologic cardioversion, also called chemical cardioversion, uses antiarrhythmia medication instead of an electrical shock.
Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal or abnormal.
Sinus node dysfunction (SND), also known as sick sinus syndrome (SSS), is a group of abnormal heart rhythms (arrhythmias) usually caused by a malfunction of the sinus node, the heart's primary pacemaker. Tachycardia-bradycardia syndrome is a variant of sick sinus syndrome in which the arrhythmia alternates between fast and slow heart rates.
An implantable cardioverter-defibrillator (ICD) or automated implantable cardioverter defibrillator (AICD) is a device implantable inside the body, able to perform defibrillation, and depending on the type, cardioversion and pacing of the heart. The ICD is the first-line treatment and prophylactic therapy for patients at risk for sudden cardiac death due to ventricular fibrillation and ventricular tachycardia.
Third-degree atrioventricular block is a medical condition in which the electrical impulse generated in the sinoatrial node in the atrium of the heart can not propagate to the ventricles.
The cardiac conduction system transmits the signals generated by the sinoatrial node – the heart's pacemaker, to cause the heart muscle to contract, and pump blood through the body's circulatory system. The pacemaking signal travels through the right atrium to the atrioventricular node, along the bundle of His, and through the bundle branches to Purkinje fibers in the walls of the ventricles. The Purkinje fibers transmit the signals more rapidly to stimulate contraction of the ventricles.
Supraventricular tachycardia (SVT) is an umbrella term for fast heart rhythms arising from the upper part of the heart. This is in contrast to the other group of fast heart rhythms – ventricular tachycardia, which start within the lower chambers of the heart. There are four main types of SVT: atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia (PSVT), and Wolff–Parkinson–White syndrome. The symptoms of SVT include palpitations, feeling of faintness, sweating, shortness of breath, and/or chest pain.
AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia. It is more common in women than men. The main symptom is palpitations. Treatment may be with specific physical maneuvers, medications, or, rarely, synchronized cardioversion. Frequent attacks may require radiofrequency ablation, in which the abnormally conducting tissue in the heart is destroyed.
Atrioventricular block is a type of heart block that occurs when the electrical signal traveling from the atria, or the upper chambers of the heart, to ventricles, or the lower chambers of the heart, is impaired. Normally, the sinoatrial node produces an electrical signal to control the heart rate. The signal travels from the SA node to the ventricles through the atrioventricular node. In an AV block, this electrical signal is either delayed or completely blocked. When the signal is completely blocked, the ventricles produce their own electrical signal to control the heart rate. The heart rate produced by the ventricles is much slower than that produced by the SA node.
Premature atrial contraction (PAC), also known as atrial premature complexes (APC) or atrial premature beats (APB), are a common cardiac dysrhythmia characterized by premature heartbeats originating in the atria. While the sinoatrial node typically regulates the heartbeat during normal sinus rhythm, PACs occur when another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat, in contrast to escape beats, in which the normal sinoatrial node fails, leaving a non-nodal pacemaker to initiate a late beat.
In cardiology, a ventricular escape beat is a self-generated electrical discharge initiated by, and causing contraction of the ventricles of the heart; normally the heart rhythm is begun in the atria of the heart and is subsequently transmitted to the ventricles. The ventricular escape beat follows a long pause in ventricular rhythm and acts to prevent cardiac arrest. It indicates a failure of the electrical conduction system of the heart to stimulate the ventricles.
Wandering atrial pacemaker (WAP) is an atrial rhythm where the pacemaking activity of the heart originates from different locations within the atria. This is different from normal pacemaking activity, where the sinoatrial node is responsible for each heartbeat and keeps a steady rate and rhythm. Causes of wandering atrial pacemaker are unclear, but there may be factors leading to its development. It is often seen in the young, the old, and in athletes, and rarely causes symptoms or requires treatment. Diagnosis of wandering atrial pacemaker is made by an ECG.
Accelerated idioventricular rhythm is a ventricular rhythm with a rate of between 40 and 120 beats per minute. Idioventricular means “relating to or affecting the cardiac ventricle alone” and refers to any ectopic ventricular arrhythmia. Accelerated idioventricular arrhythmias are distinguished from ventricular rhythms with rates less than 40 and those faster than 120. Though some other references limit to between 60 and 100 beats per minute. It is also referred to as AIVR and "slow ventricular tachycardia."
Junctional rhythm also called nodal rhythm describes an abnormal heart rhythm resulting from impulses coming from a locus of tissue in the area of the atrioventricular node(AV node), the "junction" between atria and ventricles.
Atrial fibrillation is an abnormal heart rhythm (arrhythmia) characterized by rapid and irregular beating of the atrial chambers of the heart. It often begins as short periods of abnormal beating, which become longer or continuous over time. It may also start as other forms of arrhythmia such as atrial flutter that then transform into AF.
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 – is called tachycardia, and a resting heart rate that is too slow – below 60 beats per minute – is called bradycardia. Some types of arrhythmias have no symptoms. Symptoms, when present, may include palpitations or feeling a pause between heartbeats. In more serious cases, there may be lightheadedness, passing out, shortness of breath, chest pain, or decreased level of consciousness. While most cases of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. Others may result in sudden death.
