Heart Arrhythmias

Original Editor - Vidya Acharya Top Contributors - Vidya Acharya and Lucinda hampton

Introduction

Arrhythmia is an abnormal rhythm of the heart. The only normal rhythm of the heart is a normal sinus rhythm.

• In this rhythm, an impulse is generated in the sinoatrial (SA) node, which is conducted through and slowed down while passing through the atrioventricular node (AV). It is then passes through the bundle of His, to the left and right bundle branches, and eventually into the Purkinje fibers.

Arrhythmia is a deviation from this conduction pathway and is commonly categorised based on the conduction rate:

• Bradyarrhythmia with a heart rate of fewer than 60 beats per minute (bpm)
• Tachyarrhythmia with a heart rate higher than 100 bpm

Epidemiology

• The prevalence of arrhythmias is expected to be 1.5% to 5% in the general population, with atrial fibrillation being the most common.
• Arrhythmias may or may not produce any symptoms and can be paroxysmal, leading to difficulty in estimating true prevalence.
• The overall presence of arrhythmia is associated with higher morbidity and mortality.

Assessment

A proper medical history, family history, and physical examination should be carried out by the doctor. The clinician checks for :

• swelling in your legs or feet (an enlarged heart or heart failure)
• pulse rate
• rate and rhythm of the heartbeat
• heart murmur
• signs of other diseases, such as thyroid disease, that could be causing the arrhythmia

Diagnostic Tests

Electrocardiogram

An electrocardiogram also termed an ECG or EKG (K means kardia for heart in Greek) or a 12 lead ECG. is a simple non-invasive test that records the heart's electrical activity. The ECG produces a printout that doctors can examine to diagnose arrhythmias or other types of heart disease. ECG can accurately diagnose atrial fibrillation.

Blood tests

Blood tests are carried out to check electrolytes and levels of thyroid functions. Risk of arrhythmias increases with an overactive thyroid gland or with an electrolyte imbalance.

Holter monitors

A Holter monitors are called as ambulatory electrocardiograms. They are battery-operated portable devices that record the heart’s activity (ECG) continuously for 24 to 48 hours or longer depending on monitoring requirements. Small electrodes along with wires are attached to the skin.

Event Recorders

Abnormal heart rhythms may not occur regularly. A random ECG may not pick them. Also, a standard ECG is not portable. In such a case, a cardiac event recorder helps in recording the electrical signals of the heart while carrying out daily activities. It is a battery-powered portable device that records the heart’s electrical activity (ECG) when an individual has symptoms. They are also called ambulatory ECG monitors. It is similar to the Holter monitor. Holter monitors record beats continuously (about 24 to 48 hours) whereas an event monitor does not record continually. Instead, Event Recorder only records when it is activated or when the abnormal heart rhythm is detected. These can be worn for a month or longer. There are two types of recorders: a loop memory monitor and a symptom event monitor.

Echocardiogram

An echocardiogram uses ultrasound waves to detect the heart’s size, structure, and motion. The most common type of echocardiogram is transthoracic echocardiography (TTE) provides valuable information about a heart with an arrhythmia.

Stress Test

Stress test, also called treadmill test or an exercise stress test, can diagnose people suspected with exercise-related arrhythmias.

Electrophysiology study (EPS)

Electrophysiologic testing can help to investigate suspected arrhythmias. Under local anesthesia, temporary electrode catheters are inserted through peripheral veins (or arteries) into the heart (atria or ventricles) using a fluoroscope to record the heart’s electrical signals and understand the path of electrical impulses during each heartbeat. This procedure can provoke and diagnose known as well as infrequent arrhythmias and also help trigger latent tachycardia (fast heart rate) or bradycardia (slow heart rate).

Head-up tilt table test

A tilt table test is carried out in cases of dizziness or fainting spells. The test tells about how heart rate and blood pressure respond while changing positions from lying down to standing up. An abnormally slow heart rate or a fast heart rate can cause a drop in blood pressure with the table tilted upwards. The test is normal if average blood pressure stays stable as the table tilts upward and the heart rate increases by a normal amount.

Conclusion

• 
  Arrhythmias can pose a diagnostic dilemma. The patient presentation can be varied even for the same arrhythmia and can require a different management approach based on the patient's clinical condition and characteristics.
• Depending upon the type and severity of arrhythmias, the cardiologist may prescribe antiarrhythmic drugs, or surgical implant-devices or procedures to control the abnormal rhythm, and advice healthy lifestyle changes.