Cardiac arrhythmias Medical Assignment Help

Junctional tachycardia

Almost all junctional tachycardia is paroxysmal in nature. There is usually no associated structural disease but there may be demonstrable electrophysiological or electrocardiographic abnormalities such as the Wolff- ..Parkinson-White syndromeor the Lown-Ganong-Levine syndrome (in which there is an anomalous connection between the atrium and the bundle oTHis).
There are two main varieties of junctional tachycardia: 1 Intra-AV nodal re-entry tachycardia (AVNRT) 2 Atrioventricular tachycardia (AVRT) Both tachycardias are re-entry in type. In the intra-A V nodal re-entry tachyca;crr;;-the entire tachycardia circuit is confined to the AV node and its surrounding myocardium. In atrioventricular re-entry tachycardia there is a large circuit comprising the AV node, the His bundle, the ventricle, an abnormal connection and the atrium. The abnormal connection linking the ventricle to the atrium completes the circuit necessary to sustain the tachycardia. Typically, the tachycardia strikes s¥~nly without obvious provocation, but e~on, coffee, ~ and alcoholmay aggravate or induce the arrhythmia. The rhythm is rapid (140-280 min-I) and ~ar. An attack .may s~op  spontaneously or may continue indefinitel~ until ~e?ical intervention. The predominant symptom IS palpltatlOJlS, but che~ain, dyse.noea and po~ may develop. The polyuria occurs because tachycardia leads to an elevated atrial pressure and the release of atrial natriuretic peptide and other hormones.
The rhythm is recognized by normal QRSJ:o!TIplexes at a rate of 140-280 min-I. Sometimes the QRS com plexes will show typical bundle branch block (aberration). The P waves may occur simultaneously with the QRS complex (AV nodal tachycardia) or just after the QRS in the ST segment or the T wave (atrioventricular tachycardia)

An ECG showing Wolff-Parkinson-White syndrome.

An ECG showing Wolff-Parkinson-White syndrome.

Treatment of acute supraventricular tachycardia
An acute paroxysm of tachycardia is easy to treat.

Vagotonic manoeuvres

Most supraventricular arrhythmias require conduction through the AV node for their continuation or their expression at ventricular level. An int~vagal discharge increases AV nodal conduction time and the AV”ii(;’dat recovery tim;- Thus, atEial arrhythmias may be revealed by vagotonic stimulation -whICh block the transmissiofi 0 arr ythmias to the ventricles, and juncti~cardlas that mvolve continuous circulation (circus movement or re-entry) involving the AV node may be terminated by these manoeuvres.

Carotid sinus massage, ocular p,ressure, immemon of tlie {“acein water (diving ~flex) and the Vl!ltalva manoeuvre may be used to stimulate the vagal efferent discharge. Of these techniques the Valsalva manoeuvre is the best and often easier for the patient to perform successfully. It should be undertaken when the patient is resting in the supine position (thus avoiding elevated background sympathetic tone). Several seconds after the release of strain, the resulting intense vagal effect may terminate a junctional re-entry tachycardia or may produce sufficient AV block to reveal an underlying atrial tachyarrhythmia.

Management of tachycardia. Narrow complex.

Management of tachycardia.
Narrow complex.


Posted by: brianna


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