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Tachycardia: Difference between revisions
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=Supra-ventricular tachycardia= | =Supra-ventricular tachycardia= | ||
==Atrial arrhythmias== | ==Atrial arrhythmias== | ||
==Sinus Tachycardia= | ===Sinus Tachycardia=== | ||
====Pathophysiology:==== When the sinus node fires with a frequency between 100-180bpm, the term sinustachycardia is used. The maximum heart rate a person can achieve during exercise can be calculated by subtracting the age in years from 210. Usually it is a physiological reaction to stress (exercise, inflammation, stress). External factors can increase the heart rate like coffee and alcohol or drugs. The term inappropriate sinus tachycardia is used when the sinus node has a exaggerated response to stress. | |||
====Clinical diagnosis:====A sinus tachycardia usually has a gradual start and ending. Diagnosis on the ECG can be made by the morphology of the P-wave. The P-wave has the same morphology during sinus tachycardia as during normal sinus rhythm. | |||
= | * <b>Management: </b> | ||
===Pathophysiology= | ===Atrial Tachycardia=== | ||
===Atrial Flutter=== | |||
=== | ===Atrial Fibrillation=== | ||
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=AV node arrhythmias= | ==AV node arrhythmias== | ||
This section covers the arrhythmias in which the AV node is critical in maintaining the arrhythmia. Most of these arrhythmias share the common characteristic that AV-node blocking or delaying manoeuvres or medication (adenosine) can terminate the arrhythmia. | This section covers the arrhythmias in which the AV node is critical in maintaining the arrhythmia. Most of these arrhythmias share the common characteristic that AV-node blocking or delaying manoeuvres or medication (adenosine) can terminate the arrhythmia. | ||
==AV junctional tachycardia== | ===AV junctional tachycardia=== | ||
An AV junctional tachycardia is a tachycardia resulting from regular frequent firing (60-100 bpm) of the AV-node. It has the characteristics of a small QRS with a retrograde or no P-wave. The P-wave is not always visible because it can be hidden in the QRS complex. If it is visible it is negative in the inferior leads and narrow, suggesting an AV-nodal origin. The small QRS is not preceded by a p-wave as atrium and ventricle are activated both from the AV-node. | An AV junctional tachycardia is a tachycardia resulting from regular frequent firing (60-100 bpm) of the AV-node. It has the characteristics of a small QRS with a retrograde or no P-wave. The P-wave is not always visible because it can be hidden in the QRS complex. If it is visible it is negative in the inferior leads and narrow, suggesting an AV-nodal origin. The small QRS is not preceded by a p-wave as atrium and ventricle are activated both from the AV-node. | ||
==AV Nodal Re-entry Tachycardia (AVNRT)== | ===AV Nodal Re-entry Tachycardia (AVNRT)=== | ||
====Pathophysiology:==== | |||
AVNRT is a regular arrhythmia relying only on the dual AV-physiology for its maintenance. The AV-node has two pathways; a fast pathway with fast conduction times and a slow pathway with exhibits slow conduction. The fast pathway has a longer refractory period than the slow pathway. Due to these characteristics re-entry formation is possible. Normally the impulse from the atria is conducted through the fast pathway to the ventricle. The impulse also travels through the slow pathway, but reaches a refractory ending of the AV-node (as the fast pathway already has conducted the impulse and activated this part of the AV-node). When an extra premature atrial contraction occurs it encounters a refractory fast-pathway (which has a longer refractory period). It enters the slow pathway and when it reaches the end of this pathway it can conduct to the (now restored) end of the AV-node to the ventricles and back into the fast pathway. The result is a ventricular activation with a retrograde P-wave. If the slow pathway is restored when the impulse reaches the end (atrial side) of the fast pathway, the impulse can re-enter the slow-pathway and a re-entry mechanism is established. This is usually the mechanism of an AVNRT and is called a typical AVNRT and is found in 90% of the patient with an AVNRT. There exists two other form of AVNRT that take a different route through the AV-node. Firstly there is an atypical AVNRT in which the impulse travels through the fast pathway and returns through the slow pathway. The result of this AVNRT is a retrograde P-wave which appears far from the QRS complex. Finally there is a rare AVNRT which in patients with two slow pathways. The impulse enters en re-enters through a slow pathway. | |||
====Clinical diagnosis:==== | |||
It is a fast regular small complex tachycardia with a frequency of 180-250 bpm. It is more common in female than in men (3:1) and has a sudden onset. Palpitation can cause the Frog sign; neck vein palpitations which occur due to simultaneous contraction of the atrial and ventricle. The atria cannot empty in the ventricles and therefore expulse their content in the venous circulation. A typical AVNRT can be diagnosed on the ECG by a RP distance of 100ms. The P wave is hidden in the QRS complex or appears directly after the QRS complex. An atypical AVNRT has a retrograde P appearing far away from the QRS, as it has to travel through the slow pathway. A registration of the onset can often be quite helpful in establishing the diagnosis AVNRT. | |||
====Management:==== | |||
Termination is possible by vagal manoeuvres (blowing on the wrist, carotid sinus massage) or medication (adenosine, verapamil, diltiazem). If manoeuvres or medication fails electrocardioversion can be performed. | |||
==AVRT== | ==AVRT== | ||