The following rules are important to note:
- Pre-excitation can only occur if the accessory pathway is capable of antegrade conduction.
- If the accessory pathway is capable of conducting the impulse in both directions (atria to ventricles as well as ventricles to atria) the individual will display pre-excitation during sinus rhythm and also be at risk of antidromic and orthodromic AVRT.
What is pre-excitation syndrome?
Pre-excitation syndrome is a heart condition in which part of the cardiac ventricles are activated too early. Pre-excitation is caused by an abnormal electrical connection or accessory pathway between or within the cardiac chambers. Pre-excitation may not cause any symptoms but may lead to palpitations caused by abnormal heart rhythms.
What is pre-excitation of the heart?
Pre-excitation refers to early activation of the ventricles due to impulses bypassing the AV node via an accessory pathway. An accessory pathway can conduct impulses either anterograde, towards the ventricle, retrograde, away from the ventricle, or in both directions.
What causes pre-excitation during sinus rhythm?
Pre-excitation can only occur if the accessory pathway is capable of antegrade conduction. If the accessory pathway is capable of conducting the impulse in both directions (atria to ventricles as well as ventricles to atria) the individual will display pre-excitation during sinus rhythm and also be at risk of antidromic and orthodromic AVRT.
What is intermittent preexcitation?
Intermittent preexcitation is defined as the presence and absence of preexcitation on the same tracing (Fig.
Is pre-excitation syndrome serious?
The most common preexcitation syndrome is Wolff - Parkinson-White syndrome, which affects 2/ 1000 people. The presence of an accessory pathway could result in serious consequences, ranging from supraventricular tachycardia to sudden cardiac death.
What does pre-excitation mean ECG?
Pre-excitation describes the electrical phenomena occurring in the heart and seen on ECG in some cases due to the presence of an AP. When there is an associated tachyarrhythmia due to the presence of an AP or in patients who experience symptoms due to the AP, this disorder is termed pre-excitation syndrome (PES).
How do you treat pre-excitation syndrome?
β-blockers are commonly used to treat patients with preexcitation syndromes and with atrioventricular reentrant tachycardia. Their effectiveness is rated from 50% to 90%. In the pediatric population the most commonly used β-blockers are propranolol and metoprolol [16].
What causes ventricular pre-excitation?
Ventricular preexcitation is due to a connection of muscle fibers between the atria and the ventricles that lies outside the AV node (accessory pathway, Kent bundle). The connection allows conduction often in the antegrade and commonly in the retrograde direction.
What is pre excitation AFIB?
Pre-excitation refers to early activation of the ventricles due to impulses bypassing the AV node via an AP.
Can you develop WPW later in life?
Wolff-Parkinson-White (WPW) syndrome is a relatively common heart condition that causes the heart to beat abnormally fast for periods of time. The cause is an extra electrical connection in the heart. This problem with the heart is present at birth (congenital), although symptoms may not develop until later in life.
Is pre excitement syndrome curable?
The condition may not require any treatment at all, but symptoms can be controlled using medication or catheter ablation. Electrical conduction system of the heart. (Accessory pathways not shown.)
What kind of arrhythmia is pre excitation syndrome?
The presence of a short PR interval, frequently with a delta wave, defines the preexcitation syndrome. While no clear arrhythmia is associated with Lown-Ganong-Levine syndrome, patients with Wolff-Parkinson-White syndrome may have atrioventricular (AV) reentrant tachycardia or atrial fibrillation/flutter.
What does pre excitation mean?
Answer :Pre-excitation is a term used to describe the early delivery of an electrical impulse to heart muscle prior to when it should normally be arriving. This condition is also known as Wolf-Parkinson-White Syndrome, or WPW.
How is Wolff-Parkinson-White diagnosed?
WPW is usually diagnosed with a standard ECG, but specialized testing is required in some people. The electrocardiogram — The WPW pattern can be detected by an ECG even while the person is in a normal rhythm. Conduction through the accessory pathway produces a characteristic ECG pattern.
What is WPW and how is it treated?
Cardiac catheter ablation Treatment for Wolff-Parkinson-White (WPW) syndrome depends on the severity and frequency of symptoms and the type of heart rhythm problem (arrhythmia) causing the fast heart rate. The goals of treatment are to slow a fast heart rate when it occurs and to prevent future episodes.
Can WPW cause anxiety?
Patients with Wolff-Parkinson-White syndrome may present with a multitude of symptoms such as unexplained anxiety, palpitations, fatigue, light-headedness or dizziness, loss of consciousness, and shortness of breath.
What is pre-excitation?
What is that and is it dangerous? Answer : Pre-excitation is a term used to describe the early delivery of an electrical impulse to heart muscle prior to when it should normally be arriving. This condition is also known as Wolf-Parkinson-White Syndrome, or WPW.
What is pre-excitation in fetal life?
In those people in whom it doesn't disappear, we are left with that extra pathway. The pre-excitation refers to what's seen on an electrocardiogram.
What is the pathophysiology of pre-excitation and accessory pathways?
Pathophysiology of pre-excitation and accessory pathways. Pre-excitation refers to early activation of the ventricles due to impulses bypassing the AV node via an accessory pathway. Accessory pathways, also known as bypass tracts, are abnormal conduction pathways formed during cardiac development and can exist in a variety ...
Why are QRS complexes narrow?
The QRS complexes are narrow because impulses are being transmitted in an orthodromic direction (A -> V) via the AV node
How is tachyarrhythmia facilitated?
Tachyarrhythmias can be facilitated by: Formation of a reentry circuit involving the accessory pathway, termed atrioventricular reentry tachycardias (AVRT) Direct conduction from the atria to the ventricles via the accessory pathway, bypassing the AV node, seen with atrial fibrillation or atrial flutter in conjunction with WPW.
Where does anterograde conduction occur?
In orthodromic AVRT, anterograde conduction occurs via the AV node, with retrograde conduction occurring via the accessory pathway. This can occur in patients with a concealed pathway.
Which pathway allows rapid conduction directly to the ventricles bypassing the AV node?
The accessory pathway allows for rapid conduction directly to the ventricles bypassing the AV node
Is pre-excitation pronounced?
The features of pre-excitation may be subtle, or present only intermittently. Pre-excitation may be more pronounced with increased vagal tone e.g. during Valsalva manoeuvres, or with AV blockade e.g. drug therapy.
What happens to the ventricles during pre-excitation?
As mentioned in Chapter 1, pre-excitation causes secondary ST-T changes. This is due to the fact that pre-excitation leads to abnormal depolarization of the ventricles and this leads to abnormal repolarization as well.
What is the only communication between the atria and the ventricles?
Pre-excitation. The atrioventricular node and bundle of His are normally the only communication between the atria and the ventricles. The atrial impulse must pass through the atrioventricular node, which delays the impulse due to its slow conduction, before the impulse may reach the ventricles.
Is LGL a preexcitation?
LGL (Lown-Ganong-Levine) syndrome has traditionally been described as pre-excitation with an accessory pathway between the atria and His bundle (with antegrade conduction). This is considered to result in tachyarrhythmias with short PR interval but no delta wave and normal QRS complexes. However, there are no evidence that such a syndrome actually exist and electrophysiological studies have consistently failed to verify the existence of such an accessory pathway in patients presenting with such arrhythmias. Therefore, the term LGL syndrome should not be used.
Does the accessory pathway show pre-excitation?
Individuals with accessory pathways (Kent’s bundle) only display pre-excitation on the ECG when impulses are actually conducted over the accessory pathway. In most individuals with accessory pathways the conduction over the pathway is intermittent, meaning that pre-excitation may not be seen at all times.
Do accessory pathways have slow conduction?
Accessory pathways do not display the slow conduction that the atrioventricular node does, and this means that any impulse reaching the accessory pathways may travel directly to the ventricles without any delay. Hence, the ventricle will be excited (depolarized) earlier than expected, which is referred to as pre-excitation. This manifests with three features on the ECG and the combination of these features are unique to pre-excitation:
What is the condition that promotes early ventricular excitation?
A rare condition that promotes early ventricular excitation is the enhanced AV conduction, so-called Lown-Ganong-Levine syndrome [ 406 ]. The impulse runs very quickly through the AV node and His bundle, with a short PR interval and a normal QRS complex. Two histological backgrounds have been reported to explain the missed delay at the specialized AV junction: (a) a congenitally hypoplastic AV node, with a lessened bulk of specialized tissue to slow down impulse transmission from atria to ventricles [ 407] ( Figure 10.61) and (b) the presence of an atrio-His bundle of working myocardium that bypasses the AV node and transmits the activation signal directly to the His bundle without any delay at the nodal level (so-called James' Brechenmacher's fascicles) [ 393, 394 ]. In both substrates, the onset of atrial fibrillation, with nearly one to one AV conduction, may trigger ventricular fibrillation, as it occurs in the Wolff-Parkinson-White syndrome.
What is PJRT in ventricular preexcitation?
For people with this problem, there can be a unique form of tachycardia known as permanent junctional reciprocating tachycardia (PJRT) ( Fig. 5.31 ). This tachycardia is incessant and often begins in childhood. Over time, patients with this problem often develop tachycardia-induced cardiomyopathy. Individuals with this problem require ablation of the accessory pathway because there is no other treatment. If it is not diagnosed and corrected in time, patients can develop CHF with risk of life-threatening ventricular arrhythmias or symptoms requiring cardiac transplant.
What drugs increase the refractory period of the accessory pathway?
These patients are usually treated with drugs that increase the refractory period of the accessory pathway, such as procainamide, propafenone, flecainide, disopyramide, ibutilide, and amiodarone. 49–51 However, individual patient response will vary depending on the window of unidirectional block, as well as the different effects the same drug has on both pathways. For example, verapamil and digoxin may perpetuate the arrhythmias, especially when WPW syndrome is associated with atrial fibrillation. 48,52 A nonpharmacologic approach in the treatment of patients with pre-excitation syndromes is catheter ablation of the accessory pathways, 53,54 with initial success of approximately 95% in most series. 55
What is the treatment for reentrant tachycardia?
The preferred treatment is often ablation of accessory pathway. The main problem is related to the risk of sudden death that might complicate the follow-up and be the first event in patients with asymptomatic preexcitation. The risk of sudden death remains rare and should be compared with the risks and success of ablation of accessory pathway. Generally, noninvasive studies are unable to correctly predict the risk. Electrophysiological study is the best means to detect the risk of sudden death, evaluate the nature of the symptoms, and discuss ablation.
Does lown-ganong-levine syndrome cause short PR interval?
There are other reported forms of ventricular preexcitation that involve rapid conduction via the AV node, leading to a short PR interval but a normal QRS complex. This electrocardiographic finding is not per se the Lown-Ganong-Levine (LGL) syndrome, which, as originally described, involves an SVT and a short PR interval. Indeed a short PR interval need not indicate an accessory pathway at all but could be due to enhanced AV node conduction. With enhanced AV node conduction, the AH interval (i.e., the time it takes to traverse the AV node) is rapid, and the refractory period of the AV node is short so that rapid conduction proceeds very quickly. For people with this condition who develop AF, ventricular response rate can be extremely rapid; because the condition involves the AV node and not an extra AV nodal accessory pathway, there is no delta wave and thus no evidence of ventricular preexcitation. Patients with LGL syndrome may have other accessory pathways involved in reentry tachycardias; however, these are not well characterized. Treatment with either a calcium channel blocker or β-adrenergic blocker may not be effective, and often additional treatment using antiarrhythmic drugs, such as class IC or class III antiarrhythmic drugs is required.
Does Digoxin cause ischemia?
Right bundle branch block does not significantly reduce the accuracy of the EST for the diagnosis of ischemia. Digoxin may also cause false-positive ST-segment depressions during exercise and is also an indication to consider an imaging modality to assess for ischemia. Fig. 5.1 presents an algorithm for selecting the appropriate stress test in different settings.
Is bypass conduction antegrade or retrograde?
Some are never functional and are clinically irrelevant. Other bypass tracts may be capable of only retrograde conduction (i.e., from the ventricles to atria), but may or may not be capable of antegrade conduction due to functional or organic reasons.
What is pre-excitation in heart?
Pre-excitation exists when there is an accessory pathway (AP) for electrical conduction between the atria and ventricles. The pathophysiology of pre-excitation occurs when impulses are transmitted across an AP from the atria to the ventricles thus bypassing the AV nodal pathway. The AP consists of normal myocardium and can permit either anterograde or retrograde conduction of electrical activity between the chambers of the heart. The pathway is thought to develop due to incomplete separation of the atria and ventricles during embryogenesis.
What is the name of the pre-excitation syndrome?
PES may also be called ventricular PES or AP syndrome. Syndromes of pre-excitation include Wolff-Parkinson-White (WPW) syndrome, concealed WPW syndrome, Lown-Ganong-Levine syndrome, and Mahaim type of pre-excitation. WPW, in which pre-excitation is associated with supraventricular tachycardia, is the most common and prototypical syndrome ...
What is ventricular pre-excitation?
Ventricular pre-excitation is a condition in which some or all of the ventricular muscle of the heart undergoes electrical activation (or depolarization) earlier in relation to atrial events than would be expected had the electrical impulses travelled normally by way of the atrioventricular (AV) conduction system.
Is PES contraindicated?
Certain medications used to treat PES may be contraindicated in patients with structural heart disease, cardiomyopathy, or decreased LVEF. Please see above.
Can preexcitation be asymptomatic?
Patients with pre-excitation may be asymptomatic, particularly if only ECG findings of pre-excitation are present. Male gender or young age may predispose to the development of symptoms or sudden cardiac death (SCD). In patients with an associated tachyarrhythmia and PES, common signs and symptoms include: palpitations, heart fluttering, racing heartbeat, dizziness, lightheadedness, presyncope/syncope, anxiety, pounding sensation in the neck/chest, chest discomfort or pain, and shortness of breath. These symptoms typically are paroxysmal but may be persistent in some cases.
Is pre-excitation a tachyarrhythmia?
The actual prevalence of pre-excitation syndrome (pre-excitation with an associated tachyarrhythmia) is unknown but is much less than the prevalence for pre-excitation alone. The risk of death due to arrhythmia in asymptomatic patients with pre-excitation is extremely low.
Can pre-excitation syndrome be detected?
There are no specific laboratory findings for pre-excitation syndrome. Electrolyte abnormalities are commonly monitored and corrected in order to prevent or decrease the chance for arrhythmias. Similarly, patients are usually screened with thyroid function tests which could indicate a potential treatable trigger for tachycardia.
What does premature ventricular complexes indicate?
Premature ventricular complexes placed at the time of His bundle refractoriness during supraventricular tachycardia that preexcite the atrium without a change in the atrial activation sequence and reset the tachycardia indicate an accessory pathway−mediated tachycardia. However, rarely, in patients with AV node reentry who have a bystander retrograde conducting nodoventricular tract, a similar response can occur during AV nodal reentrant tachycardia. The premature ventricular complexes conduct over the nodoventricular tract to reset the AV nodal reentry.
What is Pompe disease?
Pompe disease is an autosomal recessive disorder that results from the deficiency of acid α-glucosidase, a lysosomal hydrolase. Three major forms of the disorder are recognized: infantile, juvenile, and adult onset. The infantile form usually presents by the age of 6 months and is marked by a progressive and rapidly fatal course. Recombinant human α-glucosidase treatment has shown some promise in the treatment of this disease. 29 The association of Pompe disease with preexcitation was reported as early as 1978. 30 A synopsis of these genetic preexcitation syndromes is presented in the Table.
