Medicine lecture on cardiovascular medicine explains treatment for tachyarrythmias
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Treatment strategy for tachyarrhythmias differs depending on the cause of increased ventricular rate.
If any interference has to be made for atria or ventricles cells, we use class I or Class III antiarrhythmic drugs
In arrhythmias which occur due to pacemaker cells i.e SA node or involve AV node , in that case, it is Class II or class IV antiarrhythmic drugs are used. So basically these 2 classes of drugs are used for Supraventricular arrhythmias that are caused in SA node or due to excessive conduction of impulses through AV node.
Supra ventricular causes of tacharrhythmias:
In case of supra ventricular arrhythmias, cause can be at the level of SA node or atria or AV node pathway
1. At the level of SA node: inappropriate tachycardia: For treating SA node arrhythmia we may use either Class II drugs i.e beta blockers or class IV drugs i.e calcium channel blockers
2. Atrial causes of tachyarrhythmias.: It may be either atrial flutter or fibrillation
For AF/AFi, we need to decrease the number of impulses being conducted to ventricle. This is done by class II or class IV antiarrhythmics. It does not terminate the arrhthmia as such but decreases the number of impulses conducted to ventricles. But if, ventricular rate cannot be controlled or the patient experiences symptoms like palpitation or the patient is hemodynamically unstable, we need to revert to sinus rhythm..i.e terminate the arrhythmias.
If it is an emergency condition: electrical cardio version is done
class Ic i.e propafenone or class III drugs dofetilide may be used:
a. In case if it is not an emergency but the patient is experiencing the symptoms
b. the in case the condition is recurrent tomaintain sinus rhythm
For prolonged treatment for recurrent AF or atrial fibrillation, another class III drug amiadarone is used
Also ablation of the focus with readiofrequency waves may be done..
3. Reentry arrhythmias- it may be either AV nodal reentry arrhythmias or Atrio-ventricular reentry arrhythmias.
In AV nodal reentry, both fast and slow pathways are present in the conducting pathways involving AV node. For the treatment, Initially vagal manoeuvres are sought which decrease the RMP. or IC adenosine is gicen which also hyperpolarizes the tissue, making them less excitable.
For Atrioventricular reentry, where there is an accessory pathway between the atria and the ventricles, use potassium channel blockers i.e class III drugs which will prevent the ventricular cells from getting depolarised and class I drugs which will increase the threshold. Again, vagal monouvers and adenosine will hyperpolarize the tissue and may be used for termination of arrhythmias
Ventricular arrhythmias
1. Ventricular tachycardia: if the person is hemodynamically unstable we need to urgently use electrical cardioversion to bring revert him to sinus rhythm
If VT is arising in an ischaemic tissue, we can use Class Ib drugs especially IV lidocaine. In case of recurrent VT we need to resort to long term treatment. Again for long term we have to use Class III drugs esp amiadorone.
2. Ventrciular fibrillation: for hemodynamically unstable case, we need to use electrical cardio version to revert them to sinus rhythm. …in case of recurrent VF, we need to implant a cardiac defibrillator i.e ICD in patient’s heart which senses the origin of the VF and delivers shocks to restore normal sinus rhythm. If the patient is not an ideal candidate for ICD we may use class IIII drug..amiadoarone to increase the refractory period and make the cells unresponsive so that reentry is not possible.
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