Causative and risk factors
Arrhythmias can occasionally occur in normal healthy hearts. However in most cases, there exists an underlying cause. Hypertension, congenital defects of the heart and pre-existing diseases of the heart such as rheumatic heart disease or coronary heart disease can give rise to arrhythmias. Arrhythmias can also result from heart muscle changes, prior heart attack, electrolyte imbalances or thyroid disorders. Abuse of drugs or alcohol, strong emotional excitement, stress or anger can also give rise to arrhythmias.
The types of arrhythmias include:
- Atrial fibrillation: refers to irregular heart rhythm that causes abnormal contraction of the atria.
- Premature ventricular contractions: Skipping of a heartbeat. Very common type of arrhythmia. They are considered harmless in most cases.
- Atrial flutter: It is more organized that atrial fibrillation. It results because of one or more rapid circuits in atrium.
- Paroxysmal supraventricular tachycardia: Tachycardia which originates from above the ventricles and follows regular rhythm.
- AV nodal reentrant tachycardia. Tachycardia which occurs as a result of presence of more than one pathway through the AV node. It can lead to palpitations, fainting, or heart failure.
- Premature atrial contractions: These are harmless extra beats that originate early in the atria.
- Ventricular tachycardia: This refers to rapid heartbeats which arise from the ventricles of the heart. This prevents sufficient filling of blood in heart. Due to this less blood is pumped through the body.
- Ventricular fibrillation: Refers to a disorganized pushing of impulses from ventricles. It is a medical emergency.
- Bradyarrhythmias: Few heart conditions like sinus node dysfunction, heart block results in bradyarrhythmias. Basically these are very sluggish heart rhythms.
- Sinus node dysfunction: An abnormal SA node is responsible for slow heart rhythm. Needs to be treated with a pacemaker.
- Heart block: It is a condition in which there is delay or complete block in transmitting electrical impulse from sinus node to the ventricles.
- Accessory pathway tachycardias: Tachycardia because of abnormal connection between atria and ventricles. Due to this abnormal connection the impulses travel through two routes: the usual route and the abnormal route. This results in very rapid heartbeat.
- Long QT syndrome: An abnormally longer QT interval results in this condition. Long QT syndrome is an inherited condition.
Clinical presentation
The patient may experience palpitations or a fluttering sensation in the chest or neck. He/she may feel dizzy, weak and out of breath. Other symptoms include pain in the chest, tachycardia and syncope. Sometimes the patient may collapse due to a sudden cardiac arrest.
Complications can arise such as stroke, heart failure, Alzheimer’s disease and sometimes, sudden death.
Investigations
The different kinds of arrhythmias must be differentiated from each other by means of symptomatic assessment and necessary investigations.
A chest X-ray, an ECG and a stress test are performed. Holter monitoring is recommended which records the heart’s electrical signals for a full 24 or 48 hour period. Blood tests are done to check serum electrolyte levels, complete blood count and thyroid/kidney/liver function tests.
Procedures such as coronary angiography, cardiac catheterization and an electrophysiology study are recommended if necessary. In an electrophysiology study, a thin wire is introduced into the veins of the heart to record its electrical signals.
Head-up tilt table test: In this test, the vital parameters of the patient such as pulse, blood pressure etc. are monitored whilst being in the head raised position.
Treatment
Patients are advised not to smoke or drink in excess. If overweight, the excess weight should be lost.
One or more of the following medications are prescribed to the patient depending upon the type of arrhythmias – beta blockers, calcium channel blockers, digoxin, ibutilide, amiodarone, propafenone etc.
Certain procedures such as defibrillation or vagal maneuvers may be indicated. In defibrillation, electricity is applied to the heart. Vagal maneuvers are simple exercises that can occasionally help reduce some types of supraventricular arrhythmias.
Any of the following surgeries may be needed:
- Catheter ablation: a thin, flexible tube is introduced into the heart to destroy minor areas of heart muscle where abnormal heart rhythms may originate.
- Pacemaker: a small device is placed under the skin of the patient’s chest in order to regulate abnormal heart rhythms.
- Maze surgery: The atria are subjected to small cuts or burns which prevent the spread of disorganized electrical signals.
- Coronary artery bypass
