ARRHYTHMIA-TREATMENTS
ARRHYTHMIA the irregular rhythmical beats of heart may result many times fatal if unattended
The Anatomy of Electrical Conduction Of the Heart Beats
As in the above diagram the electrical conduction of the heart muscle is clitched to start at the Sinu-Atrial (SA) node the most auto generated electrically depolarizable tissue in our body.
The atrium contracts and the conduction spreads down wards like waves to reach Atrio-Ventricular (AV) node as in the above figure.
The AV node is situated in between the Right Atrium (RA) and the Right Ventricle and this AV node is acting as protective shield to filter of any unwanted excessive impulses from above to pass further down to this shield.Also AV node acts as a Gate to pass needed impulses from the SA node sufficient for ventricular contraction.
Ventricular contraction not begins immediately when the impulses reaches AV node as the node is situated more towards the right as in the figure above,and because both right and left ventricle needed equal impulses to contract.To disperse the impulse equally from AV node to both the sectors nature has provided a special tissue which is a portion of AV node.This special tissue is known as Bundle of His as you can note in the figure.This tissue is branched equally to right and left.AV node send impulses to Bundle of His which sends the impulses to both right and left down to the bottoms of both the ventricles known as Purkinje Fibers and the ventricles contracts.
This can be easily illustrated by an ECG as followsl;-
P-wave represent the Atrial depolarization and contraction
PR-interval represents the conduction of the impulse from the Atria to Purkinje fibers
QRS curve the rapid repolarize and depolorization of Ventricles
The ST segment represent the resting period or plateu period of the myocardium.
There are two types of impulse defects may occur during a rhythm.
1.Defects in the formation of the impulses as during stresses,straining to expell the feces in constipation,weight lifting,hard excercise.These impulses are non pathalogic and need no medical interventions.It can get corrected by taking rest and relax.
2.Defects in the conduction of formed impulses due to some underlying causes such as HT,Cardiac Failure,MI,Drugs,Infections,Anginas,Valvular defects and cardiac muscle damages may be pathologic and is known as Pathologic Arrhythmias and may be fatal.This condition needs medical intervensions.Also arrythmias can be pathologic if impulses originates from other parts of the myocardium especially from the fast acting cells instead of the pace maker tissues such as SA node and AV node.
Treatments
Class-IA-.Sodium channel blockers
Quinidine
Procainimide
Disopyramide
Quinidine prolongs the QT intervals and thereby calm down the rapid depolarization of fast acting muscles like Purkinje fibers and inturn calm down ventricular fibrillation.
Quinidine is administered orally
It is metabolised in the liver and half life is 6 to 8 hrs.
Toxicity 1.GI disturbances like Diarrhea,Nausea,Vomiting.
2.Cinchonism such as blurred vision,dizziness,head ache,and tinnitus
3.Syncope with light headedness and possible faint.
4.Thrombocytopenia
5.Excess prolongation of QT intervals result in a brady arrhythmia known as Torsade de Points causes immediate death.
6.AV block
Drug Interactions 1.Increases plasma levels of digoxin and oral anti coagulants
2.Quinidine plasma levels are rapidly depleted by Phenytoin and Phenobarbital
This can be easily illustrated by an ECG as followsl;-
P-wave represent the Atrial depolarization and contraction
PR-interval represents the conduction of the impulse from the Atria to Purkinje fibers
QRS curve the rapid repolarize and depolorization of Ventricles
The ST segment represent the resting period or plateu period of the myocardium.
There are two types of impulse defects may occur during a rhythm.
1.Defects in the formation of the impulses as during stresses,straining to expell the feces in constipation,weight lifting,hard excercise.These impulses are non pathalogic and need no medical interventions.It can get corrected by taking rest and relax.
2.Defects in the conduction of formed impulses due to some underlying causes such as HT,Cardiac Failure,MI,Drugs,Infections,Anginas,Valvular defects and cardiac muscle damages may be pathologic and is known as Pathologic Arrhythmias and may be fatal.This condition needs medical intervensions.Also arrythmias can be pathologic if impulses originates from other parts of the myocardium especially from the fast acting cells instead of the pace maker tissues such as SA node and AV node.
Treatments
Class-IA-.Sodium channel blockers
Quinidine
Procainimide
Disopyramide
Quinidine
Uses-Ventricular tachycardia and supraventricular arrhythmias,Atrial fibrillation and Atrial flutterQuinidine prolongs the QT intervals and thereby calm down the rapid depolarization of fast acting muscles like Purkinje fibers and inturn calm down ventricular fibrillation.
Quinidine is administered orally
It is metabolised in the liver and half life is 6 to 8 hrs.
Toxicity 1.GI disturbances like Diarrhea,Nausea,Vomiting.
2.Cinchonism such as blurred vision,dizziness,head ache,and tinnitus
3.Syncope with light headedness and possible faint.
4.Thrombocytopenia
5.Excess prolongation of QT intervals result in a brady arrhythmia known as Torsade de Points causes immediate death.
6.AV block
Drug Interactions 1.Increases plasma levels of digoxin and oral anti coagulants
2.Quinidine plasma levels are rapidly depleted by Phenytoin and Phenobarbital
Procainamide
Uses
1.Venricular and supraventricular arrhythmias
2.Premature ventricular contractions
Procainamide is taken by oral,i.v.;or i.m.
Toxicity 1.Lupus like rashes or arthralgia.Renal involvement is unusual
2.Pericarditis,
3.Hellucination,and psycoses
4.Torsade de Points.
Disopyramide
Action is very similar to the other two above mentioned drugs but produce prolonged negative inotropic (decreasing frequency of contractility) and stronger anticholinergic effect.
This medicine can be taken by I.V. or by Oral
Uses Both ventricular and supra ventricular arrhythmias
Kinetics Largely excreted by kidneys unchanged
Toxicity 1.Dry mouth, Blurred vision,Urinary retention,Constipation and Glacoma
2.Torsade de Points
3.Contra indicated in left ventricle dysfunction as it may leads to Heart Failure
4.Because of the anticholinergic effects protate gland would be affected.
Class - IB
1.Lidocaine
2.Tocainide
3.Mexiletine
4.Phenytoin
This medicine can be taken by I.V. or by Oral
Uses Both ventricular and supra ventricular arrhythmias
Kinetics Largely excreted by kidneys unchanged
Toxicity 1.Dry mouth, Blurred vision,Urinary retention,Constipation and Glacoma
2.Torsade de Points
3.Contra indicated in left ventricle dysfunction as it may leads to Heart Failure
4.Because of the anticholinergic effects protate gland would be affected.
Class - IB
1.Lidocaine
2.Tocainide
3.Mexiletine
4.Phenytoin
Lidocaine (Xylocaine)
Lidocaine a local anethetic exert blocking effect on sodium channels
Use Lidocaine is the drug of choice for ventricular arrhythmias
Route I.V. only
Kinetics Lidocaine is metabolised in liver and care should be taken while using in liver dysfuntion
Toxicity CNS effects like Drowsiness,numbness,slurred speach,and convulsions
Nystagmus a condition at which rapid and involuntary movements of eyeballs occur
Tocainamide(Tonocard)
Usesd in ventricular arrhythmias
Taken orally
Toxicities 1.Bradycardia;2.Tachycardia;3.AV block;4.Hypotension
5.Nausea;6.Tremor;7.Lung fibrosis(Rare) ;8.Aplastic anemia(Rare)
Mexiletine (Mexitil)
Used in ventricular arrhythmias
Can be taken orally
Toxicity Dizziness;Nausea,& Vomiting;Erythrocytopenia;Thrombocytopenia;Leucopenia;Agranulocytosi s and Nystagmus
Phenytoin (Dilantin)
This drug block the inactivated sodium channel and keep it blocked for a long time and there by it is useful for convulsions and atrial and ventricular arrhythmias.
Can be taken orally or by I.V.
Side effects are similar as above.
Class-IC
1.Flecainide
2.Propafenone
3.Morizicine
Used in supraventricular and ventricular arrhythmias in patients with normal heart structure
Toxicity 1.This medicine should be used only if other medicines are ineffective because the Cardiac Arrhythmia Suppressor Trial (CAST) studies proved that this medicine is fatal to those who suffered recent heart attacks,and who suffer asymptomatic ventricular arrhythmias.
2.CNS effects like blurred vision,and headaches
3.Heart Arrest in patients who have defective conduction system.
Propafenone (Rhythmol)
Used in supraventricular and ventricular arrhythmias
Blocks sodium channels upto Purkinje fiber level and thereby correcting the ventricular contraction similar to flecainide but also have some beta adrenergic blocking effects.
Toxicity is having a proarrhythmogenic effect and beta blockade effects like Bronchospasm,bradycardia.
Class-II Antiarrhythmic Drugs-The Beta Adrenergic Blockers
In this class the most commonly used medicines as antiarrhythmics are as follows:-
1.Propranolol
2.Sotalol
3.Esmolol
Sotolol can be included in Class-III too.
The mechanism of these drugs are generally depressing the automaticity of the myocardium other than the pacemakers like SA and AV nodes and make the pacemakers to little calm by slowing their contractions and elongating their refractory periods and thereby preventing the arrhythmic excitations of the heart.
Sotolal is used clinically ventricular fibrillation
Esmolol is short acting and can be used safely during emergencies such as surgery.
Class-III -Potassium Channel Blockers
1.Bretylium 2.Amiodarone 3.Sotolol 4.Procainamide
The mechanism of action is by blocking the potassium channels so that there is no sodium influx and potassium efflux and there by prolong the ventricular excitations
These drugs can be used to treat venricular fibrillations
Postural hypotention can be an adverse effect of these medicines
Amiodarone is the drug of choice used in the name of Cardarone.
This drug also exhibits Class-I and Class-II properties also.
Amiodarone is used in Arterial flutter and ventricular arrhythmias
Amiodarone can be taken orally as well as by I.V.route.
Toxicities 1.Lung fibrosis;2.Tremor ;3.Live damage;4.Photosensiivity;5.Corneal micro deposits;6.Thyroid defects leads to iodine accumulation and thereby bluish body skin discolouration;
Class-IV-Calcium channel Blockers
1.Verapamil
2. Diltiazem
3.Nifedipine
The mechanism of action is blocking the L-type calcium channels and thereby calm down the SA and AV nodes.The actions are mostly supra ventricular and hence can be used in atrial flutters
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