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.
Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart involving an accessory pathway able to conduct electrical current between the atria and the ventricles, thus bypassing the atrioventricular node. About 60% of people with the electrical problem developed symptoms, which may include an abnormally fast heartbeat, palpitations, shortness of breath, lightheadedness, or syncope. Rarely, cardiac arrest may occur. The most common type of irregular heartbeat that occurs is known as paroxysmal supraventricular tachycardia.
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.
The bundle of His (BH) or His bundle (HB) ( "hiss") is a collection of heart muscle cells specialized for electrical conduction. As part of the electrical conduction system of the heart, it transmits the electrical impulses from the atrioventricular node to the point of the apex of the fascicular branches via the bundle branches. The fascicular branches then lead to the Purkinje fibers, which provide electrical conduction to the ventricles, causing the cardiac muscle of the ventricles to contract at a paced interval.
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.
First-degree atrioventricular block is a disease of the electrical conduction system of the heart in which electrical impulses conduct from the cardiac atria to the ventricles through the atrioventricular node more slowly than normal. First degree AV block does not generally cause any symptoms, but may progress to more severe forms of heart block such as second- and third-degree atrioventricular block. It is diagnosed using an electrocardiogram, and is defined as a PR interval greater than 200 milliseconds. First degree AV block affects 0.65-1.1% of the population with 0.13 new cases per 1000 persons each year.
Trifascicular block is a problem with the electrical conduction of the heart, specifically the three fascicles of the bundle branches that carry electrical signals from the atrioventricular node to the ventricles. The three fascicles are one in the right bundle branch, and two in the left bundle branch the left anterior fascicle and the left posterior fascicle. A block at any of these levels can cause an abnormality to show on an electrocardiogram.
Heart block (HB) is a disorder in the heart's rhythm due to a fault in the natural pacemaker. This is caused by an obstruction – a block – in the electrical conduction system of the heart. Sometimes a disorder can be inherited. Despite the severe-sounding name, heart block may cause no symptoms at all in some cases, or occasional missed heartbeats in other cases, or may require the implantation of an artificial pacemaker, depending upon exactly where in the heart conduction is being impaired and how significantly it is affected.
Lev's disease, also known as Lenegre disease, is an idiopathic disease that can result in a complete heart block, or an extremely slowed heart rate, in patients with this condition. It is thought that for certain patients, this impairment of heart's electrical conduction system is due to fibrosis and calcification of conduction cells. This disease is considered to be age related, with increasing decline seen in elderly patients.
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.
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.
Left bundle branch block (LBBB) is a conduction abnormality in the heart that can be seen on an electrocardiogram (ECG). In this condition, activation of the left ventricle of the heart is delayed, which causes the left ventricle to contract later than the right ventricle.
Lown–Ganong–Levine syndrome (LGL) is a pre-excitation syndrome of the heart. Those with LGL syndrome have episodes of abnormal heart racing with a short PR interval and normal QRS complexes seen on their electrocardiogram when in a normal sinus rhythm. LGL syndrome was originally thought to be due to an abnormal electrical connection between the atria and the ventricles, but is now thought to be due to accelerated conduction through the atrioventricular node in the majority of cases. The syndrome is named after Bernard Lown, William Francis Ganong, Jr., and Samuel A. Levine.
Multifocal atrial tachycardia (MAT) is an abnormal heart rhythm, specifically a type of supraventricular tachycardia, that is particularly common in older people and is associated with exacerbations of chronic obstructive pulmonary disease (COPD). Normally, the heart rate is controlled by a cluster of cells called the sinoatrial node. When a number of different clusters of cells outside the SA node take over control of the heart rate, and the rate exceeds 100 beats per minute, this is called multifocal atrial tachycardia.
The electrical axis of the heart is the net direction in which the wave of depolarization travels. It is measured using an electrocardiogram (ECG). Normally, this begins at the sinoatrial node ; from here the wave of depolarisation travels down to the apex of the heart. The hexaxial reference system can be used to visualise the directions in which the depolarisation wave may travel.
A left posterior fascicular block (LPFB), also known as left posterior hemiblock (LPH), is a condition where the left posterior fascicle, which travels to the inferior and posterior portion of the left ventricle, does not conduct the electrical impulses from the atrioventricular node. The wave-front instead moves more quickly through the left anterior fascicle and right bundle branch, leading to a right axis deviation seen on the ECG.
Junctional ectopic tachycardia (JET) is a rare syndrome of the heart that manifests in patients recovering from heart surgery. It is characterized by cardiac arrhythmia, or irregular beating of the heart, caused by abnormal conduction from or through the atrioventricular node. In newborns and infants up to 6 weeks old, the disease may also be referred to as His bundle tachycardia or congenital JET.
An intraventricular block is a heart conduction disorder — heart block of the ventricles of the heart. An example is a right bundle branch block, right fascicular block, bifascicular block, trifascicular block.
A frequent type of syncope, termed vasovagal syncope is originated by intense cardioinhibition, mediated by a sudden vagal reflex, that causes transitory cardiac arrest by asystole and/or transient total atrioventricular block. It is known as “Vaso-vagal Syncope”, “Neurocardiogenic Syncope” or “Neurally-mediated Reflex Syncope”. Although many different therapies have been tried in this condition, severe and refractory cases have been treated with pacemaker implantation despite great controversies about its benefit.
Progressive cardiac conduction defect(PCCD) is a hereditary cardiac condition marked by a progressive delay in impulse conduction via the His-Purkinje system, resulting in right or left bundle branch block (RBBB or LBBB), syncope, and occasionally sudden cardiac death.
