When taking care of a patient, more often than not, doctors have to cross over into the field of ano-ther sub-specialty simply because our bodies are not distinct compartments.
This means that problems occurring in one part of the body – for example, the heart – can very easily affect another distant part – in this case, the brain.
This is essentially how the heart causes a stroke.
If you have followed my previous article, When hearts go haywire published on Jan 8, I wrote that our heartbeat is generated from our own biological battery (“pacemaker”), which usually beats bet-ween 60 to 100 beats a minute at rest.
This natural heartbeat is known as the sinus rhythm (simply be- cause the “battery” is called the sinus node), where the heart muscles contract in sequence and in synchrony.
What happens when the heart is no longer in sinus rhythm? We call this condition an arrhythmia.
There are many different forms of arrhythmia, but in this article, we will delve into one called atrial fibrillation.
Atrial fibrillation (AF)
AF is a rhythm that is built on a chaotic and disorganised circuit that makes the heart’s contractions become fast and irregular.
Patients feel uncomfortable du- ring this sudden top-gear rhythm switch, experiencing palpitations and developing difficulty in breathing. For those who already have a weakened heart to begin with, this rhythm can be potentially dangerous and might cause sudden heart failure.
AF can be an episodic event (paroxysmal), something more persistent, or even permanent.
As a general rule, when a patient is found to have an irregular heartbeat, AF needs to be ruled out.
Now, to understand how AF can cause a stroke, I wish to draw your attention to a specific area of the heart called the left atrial appendage.
Left atrial appendage (LAA)
Imagine a little pocket that dangles out of the left heart chamber (the atrium), made out of tissue which normally contracts to maintain constant blood-emptying back into the heart chamber.
During AF, the tissue in the LAA will not contract, but will instead fibrillate, hence the name atrial fibrillation.
How does this lead to clot formation?
Heart clots will form when three factors are disturbed, namely, when the blood flow becomes sluggish, when structures become abnormal, and when there is increased blood thrombogenicity (blood thickening).
During AF, most of these factors are affected. Due to the nature of AF, blood in the LAA gets sluggish, stagnant and the thrombogenicity will also worsen.
If a clot is formed, the risk of it travelling to the brain to cause a stroke is high. The risk of a stroke will be even higher when other risk factors such as age, hypertension, diabetes mellitus, previous stroke or heart failure co-exist.
A classic case example: A female patient with longstanding hypertension and diabetes mellitus.
This patient had been experiencing what she described as “a frequent funny heartbeat sensation” for a couple of months now, but had always attributed it to her recent addiction to coffee.
Out of nowhere, she developed devastating weakness and later on suffered from a stroke.
During her admission, an ECG was done and AF was detected.
This is likely a case of what we call an embolic stroke where the stroke was caused by a clot originating from the heart, due to her previously undiagnosed AF.
Treatment of AF
The goal of AF management is rate and rhythm control, but more importantly, to prevent stroke from happening.
In patients who have AF with risk of developing embolic stroke, anticoagulation therapy is needed.
This has to be balanced against the risk of bleeding caused by the anticoagulants – usually well calculated and decided by the attending cardiologist.
The main problem in detecting AF is sub-optimal awareness. Many patients will brush aside their symptoms of palpitation and missed beats, which could well be the warning signs.
Some patients may even already have had stroke, but due to the paroxysm of their AF, this abnormal rhythm is not detected instantly.
This may warrant the use of a device called a loop recorder for detection of hidden AF.
In addition, a patient’s non-compliance to their medication can hamper adequate stroke prevention treatment.
In short, AF is similar to an unknown villain. Not as glamorous as other heart diseases, but equally potent in causing debilitating results.
Just like the tip of the iceberg, sometimes what awaits underneath is more than just an irregular pulse.
Don’t let AF go undetected.
Consult your health care provider to learn more.
Dr Choy Chun Ngok is a consultant cardiologist and electrophysiologist. For further information, e-mail starhealth@thestar.com.my. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
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