arrhythmia

A problem with the rate or rhythm of the heartbeat.
• tachycardia: The heart beats too quickly.
• bradycardia: The heart beats too slowly.
• atrial fibrillation (most common): The heart beats irregularly and quickly.

(Pre-excitation syndrome)
Normally, the atria and the ventricles are electrically isolated, and electrical contact between them exists only at the atrioventricular node. However, at least one more conductive pathway (abnormal accessory pathway) between the atria and the ventricles is present in the affected people.
The normal electrical depolarization wave is delayed at the atrioventricular node to allow the atria to contract before the ventricles. However, there is no such delay in the abnormal pathway, so the electrical stimulus passes to the ventricle by this tract faster than via normal atrioventricular/bundle of His system, and the ventricles are depolarized (excited) before (pre-) normal conduction system.
It is seen in tachyarrhythmias patients.

(Symptoms)
• chest pain
• shortness of breath
• sweating
• dizziness

(Causes)
• congenital heart defects
• heart attack
• stress
• smoking
• medicines

(Diagnosis)
• echocardiogram: Placing a hand-held device (transducer) on the chest, the sound waves produce images of the heart's size, structure, and motion.
• electrocardiogram (ECG, EKG): Measures the timing and duration of each electrical phase in the heartbeat.
• electrocardiographic imaging (ECGi): A multi-lead ECG-type imaging tool that enhances conventional 12-lead ECG.
• electrophysiological testing and mapping (EP study): Threading catheters tipped with electrodes through the blood vessels to different areas within the heart, maps the spread of electrical impulses through the heart.

(Treatment)
• drugs: Antiarrhythmic agents (e.g. quinidine (Ia), lidocaine (Ib), flecainide (Ic), atenolol (II, beta blocker), sotalol (III, beta blocker), verapamil (IV), digoxin (V)).
• catheter ablation: Threading one or more catheters through the blood vessels to the heart, with the heat or cold energy on the electrodes at the catheter tips, creates tiny scars in the heart to block abnormal electrical signals and restore a normal heartbeat.
• maze procedure: Makes a series of incisions in the tissue of the atria to create a pattern (or maze). Because scar tissue does not conduct electricity and interferes with stray electrical impulses that cause some types of arrhythmia.
• pacemaker (cardiac pacing device): A small device implanted in the chest to prevent the heart from beating too slowly.
- - single chamber pacemaker: Carries electrical impulses to the right ventricle.
- - dual chamber pacemaker: Carries electrical impulses to the right ventricle and the right atrium to control the timing of contractions between the two chambers.
- - biventricular pacemaker (cardiac resynchronization therapy): Stimulates both of the right and left ventricles to make the heart beat more efficiently.
• implantable cardioverter-defibrillator (ICD): A small battery-powered device implanted in the body to continuously monitor the heartbeat and deliver electric shocks when needed to restore a regular heart rhythm.
- - traditional ICD: Invasive. Implanted in the chest with the wires (leads) attached to the heart.
- - subcutaneous ICD (S-ICD): Larger but less invasive. Implanted under the skin below the armpit with an electrode that runs along the breastbone.
• coronary bypass surgery: Improves the blood flow to the heart with severe coronary artery disease.