What is Normal Heart Rhythm?
Our heart normally beats in a synchronized rhythmic fashion. First, the atria (the receiving chambers) fill passively with blood and pump it into the ventricles. Then, the ventricles (the pumping chambers), pump this blood back into the body and lungs. This rhythm is based on electrical activity within the heart and is detected on an Electrocardiogram- ECG/EKG.
As shown in this diagram, the normal electrical conduction of the heart starts in the top right chamber (the right atrium), where the natural pacemaker of the heart is located. This natural pacemaker is called the SA node. The electrical impulse then travels downwards to the AV node and subsequently is conducted to the two pumping chambers, the left and right ventricles.
The normal electrical conduction can be detected on an electrocardiogram.
The Normal ECG. Please note that the normal ECG has specific characteristic waves: P, QRS and T.
What is the normal heart rate?
Our heart rate increases with exercise or exertion. Infants and children have faster-resting heart rates up to 110-120/min. Adolescents and adults have resting heart rates of 60-80/min. Any heart rate above 200-220 is usually abnormal, even in children.
What is an Arrhythmia?
An arrhythmia is any change in the regular, synchronized rhythm of the heartbeat.
Most arrhythmias are caused by an electrical “short circuit” in the heart.
- Tachycardia is the term used for fast heart rate. When this fast heart rate has an abnormal rhythm, it is termed as Tachyarrhythmia
- Bradycardia is the term used for slow heart rate. When this slow heart rate has an abnormal rhythm, it is termed as Bradyarrhythmia
What are the types of Tachyarrhythmias?
Tachyarrhythmias can be divided into Atrial and Ventricular
Common Atrial arrhythmias include SVT, Atrial tachycardia and Atrial flutter/ fibrillation.
Common Ventricular tachyarrhythmias include Ventricular tachycardias and Ventricular fibrillation. There are a specific group of cardiac conduction disorders known as Channelopathies. Examples of channelopathies are Long QT syndrome (associated with congenital deafness) and Brugada syndrome. Patients with these disorders are at high risk of ventricular tachycardia and ventricular fibrillation.
ECG of Long QT syndrome
ECG of SVT ECG of Ventricular Tachycardia
The diagnosis of all arrhythmias can be made on an ECG. Sometimes, the rhythm abnormality may be transient. As the regular ECG only detects the rhythm for a few seconds, all transient arrhythmias will need ECGs for a longer duration to detect and diagnose the exact abnormality. These longer ECGs are known as Holter recordings and can be undertaken for 24, 48 or 72 hours.
When to Suspect Tachyarrhythmias?
Symptoms of Tachycardia/ Tachyarrhythmia are: Palpitations– feeling one’s own heartbeat, dizziness, loss of consciousness and breathing difficulty.
Are any Tachycardias normal?
Sinus tachycardia is the normal acceleration of the heart rate and is seen with fever, anxiety or after sports or exercise.
How to treat Tachyarrhythmias?
Tachyarrhythmias can be treated with medications if the patient is relatively stable. If the patient is unstable or has collapsed, the rhythm needs to be converted to a normal rhythm immediately. This is achieved with a Cardioversion or DC shock using a defibrillator (photograph shown below).
What is Bradyarrhythmia?
The commonest bradyarrhythmia requiring treatment in children is Complete Heart Block. Other bradyarrhythmias include a 2:1 or 3:1 heart block or sinus node dysfunction.
Sinus bradycardia is the term used to describe slow heart rate with a normal rhythm, as can be seen during deep sleep.
When to Suspect Bradyarrhythmias?
Symptoms of Bradycardia/ Bradyarrhythmia include dizziness, loss of consciousness and fatigue. In small babies, poor growth and breathlessness may be the only symptom of bradycardia.
How do you treat bradyarrhythmia?
If symptomatic, a patient with bradyarrhythmia may need a pacemaker.
Can arrhythmias be life-threatening?
- Ventricular tachycardia, especially when associated with channelopathies like long QT syndrome can be life-threatening
- SVT (supraventricular tachycardia) can usually be well tolerated when it is transient and self-resolving. Prolonged SVT can also cause weakness of the heart pumping function. But this generally resolves once the rhythm returns to normal.
- Complete heart block can also be life-threatening if the heart rate is too slow to maintain adequate blood supply to the body.
Can Arrhythmia medications be given in small babies?
Arrhythmia medicines are safe in babies and children if the correct dose is given. These medicines should only be given when clinically indicated and should be prescribed only by a trained specialist.
Can an artificial pacemaker be inserted in a small baby?
- When required, even a newborn baby can have a pacemaker implantation.
- In small children, the pacemaker is put surgically as an epicardial pacemaker with the pacing lead on top of the heart
- In older children and adults, the pacing lead is put within the heart as an endocardial pacemaker
Diagram of a pacemaker with the battery, circuitry, and the pacing lead.
Important Points to remember
- Arrhythmias in children can present with a variety of symptoms, and some can be potentially life-threatening
- Arrhythmias are treatable with medications (for tachyarrhythmias) and pacemakers (for heart block) if diagnosed correctly
- Even arrhythmias in small babies can safely be treated with medications and pacemakers if required