When Your Heart Loses Its Rhythm: Understanding Atrial Fibrillation

This article marks the first in a new series from Starts at 60’s resident doctor, Kathryn Fox, designed to break down common health conditions in a clear, practical way. In Common Conditions Simply Explained, Dr Fox takes complex medical topics and makes them easier to understand—what they are, why they matter, and what to look out for.

We begin with something many of us rarely think about until it changes: the rhythm of the heart.

One of the things we usually take for granted is our heartbeat.

We don’t have to think about it. It’s just there – steady, a reliable electrical system ticking along in the background.

Until it isn’t.

We’ve all seen the dramatic, life-threatening rhythms on television – ventricular fibrillation (VF) or ventricular tachycardia (VT) – where doctors shout “Clear!” before delivering a shock to restore a normal rhythm.

If that works, the heart resets. If there’s a flatline – known as asystole – there’s no electrical activity at all and the doctors pronounce ‘time of death’.

But one of the most common abnormal rhythms, particularly in people over 60, is atrial fibrillation (AF). And unlike those dramatic scenarios, AF often sits quietly in the background.

Many people don’t realise they have it – or why it matters.

What Is Atrial Fibrillation?

The heart works through a carefully coordinated electrical system.

Each beat is triggered by a signal that tells the heart when to contract and pump blood, and when to relax and refill. This creates a steady rhythm – pump, refill, pump, refill – that keeps blood circulating around the body.

Think of it like a conductor leading an orchestra, with every instrument playing in time.

In atrial fibrillation, that coordination is lost. Instead of one clear signal, multiple chaotic signals fire at once.

The upper chambers of the heart – the atria – start to quiver rather than beat properly. As a result, the heartbeat becomes irregular. Sometimes fast, sometimes uneven, sometimes barely noticeable.

What Does It Feel Like?

For some people, atrial fibrillation is obvious.

They may notice:

• a racing or fluttering heart
• an irregular pulse
• shortness of breath
• fatigue or reduced exercise tolerance

Others feel nothing at all. And that’s where it becomes tricky.

Why Does AF Matter?

The issue isn’t just the irregular rhythm.

When the heart isn’t pumping effectively, blood doesn’t move through it as smoothly as it should. The upper chambers may not empty properly, allowing blood to pool – and that’s where clots may form. If a clot travels to the brain, it can block blood flow and cause a stroke. This is why atrial fibrillation is taken seriously, even when symptoms are mild – or absent.

How Common Is It?

The Heart Foundation estimates that hundreds of thousands of Australians are living with atrial fibrillation – and many don’t know it.

It becomes more common with age:

• around 5–9% of people between 60 and 80
• up to 1 in 5 people over 80

The Royal Australian College of General Practitioners (RACGP) notes that it’s often picked up incidentally during routine checks.

The Good News

Atrial fibrillation can be managed.

Treatment usually focuses on:

• controlling the heart rate or rhythm
• reducing stroke risk (often with anticoagulants, sometimes called blood-thinning medication

For many people, this significantly reduces risk and improves quality of life.

How Is It Diagnosed?

Often, it’s picked up during a routine check.

A doctor may notice an irregular pulse, or it may appear on an ECG. You can also check your own pulse. A normal pulse feels steady – like a regular drumbeat.
If it feels irregular, uneven, or unpredictable, it’s worth getting checked.

Intermittent symptoms are important to report. Don’t feel reassured just because the rhythm comes and goes. Longer monitoring – such as a 24-hour ECG or wearable monitor – can help detect episodes that aren’t always present.
Unfortunately, atrial fibrillation is sometimes first diagnosed after a stroke, which is why early detection matters.

The Bottom Line

Atrial fibrillation is more common as we age, often silent, and potentially serious. But it’s also very treatable. And the earlier it’s recognised, the better the outcome. Your heart is meant to beat with a steady rhythm. If it starts to feel out of sync, it’s important to get it checked.