Heart block

What is it?

The electrical pulses that trigger and regulate the heart’s beating pattern are disrupted, causing the heart to beat more slowly.

What are the symptoms?

Shortness of breath, irregular heartbeat, dizziness and fainting.

How the heart beats

Normally the trigger to make heart muscles contract (beat) is electrical pulses from a group of specialised cells called the SA node (sinoatrial node) found in the upper heart chamber (atrium).

Pulses spread to the strong lower chambers (ventricles) through the AV node (atrioventricular node) so the upper and lower chambers of the heart almost beat in unison. Heart block occurs if the transmission from the SA node is interrupted.

Types of heart block

First-degree heart block: There’s a split-second delay in the time it takes electrical pulses to move through the AV node. It rarely causes any noticeable symptoms.

Second-degree heart block:

There’s a series of increasing delays in the time it takes the AV node to send the pulse to the lower chamber leading to a heartbeat being skipped.

Third-degree heart block:

There’s no transmission of electrical pulses between the upper and the lower chambers through the AV node. The symptoms can be lifethreatening.

What causes it?

The commonest causes are destruction of heart muscle from a heart attack, certain medicines and ageing of SA and AV nodes.

How it’s diagnosed

By an electrocardiogram (ECG) where small electrodes are placed on your chest which record a trace of your heart’s rhythm and measure the strength and frequency of the electrical signals.

What’s the treatment?

Basically a pacemaker. Transcutaneous pacing (TCP) is a temporary method of pacing the heart. Pads are applied to your chest and electrical pulses are passed through them to stabilise your heartbeat and restore your heart rate to normal.

Once your heartbeat has been stabilised, a permanent pacemaker may be recommended.