Atrial fibrillation occurs when the electrical impulses that cause cardiac contractions become erratic and unsynchronised, causing the heart to beat irregularly. This ‘arrhythmia’ of the atrium, when left untreated, leads to several complications like blood clots, stroke, and even heart failure.
Over 2.7 million Americans suffer from cardiac arrhythmia, often accompanied by nausea and breathlessness, especially, while carrying weight up stairs or bending down. However, some people are asymptomatic, and discover they have atrial fibrillation only during a doctor visit or after a cardiac event.
How atrial fibrillation causes heart rhythm problems or “arrhythmia”?
Every heartbeat is controlled by the heart’s electrical system.
In normal conditions, the electrical impulse initiates from the sinoatrial (SA) node at the top of the heart, from where the it travels to the lower parts or the ventricles, signaling them to contract. The atrioventricular (AV) node serves as a ‘gatekeeper’ for the current passing through the atria to the ventricles. It delays the electrical wave to reach the ventricles in order to lend them extra time to finish filling with blood before contracting. The SA node fires off between 60-100 beats per minute in healthy adults.
In case of atrial fibrillation, the contractions might start in random areas in the atria or even in the pulmonary veins. As a result, the electrical current doesn’t flow in an organized, rhythmic, top-to-bottom fashion. The AV node often cannot regulate this chaotic current. The ventricle fills irregularly and cannot supply enough blood per beat. Hence, the ventricle beats more often than it should (100-175 times), leading to breathlessness and fatigue.
How does atrial fibrillation lead to stroke?
Imagine wringing out a sponge. Without a good squeeze, water will still be left in the sponge. In the same way, uneven heart contraction limits the blood outflow from the atria. The pooled up blood in the atria is at a greater risk of clotting. These clots can then be pumped out of the heart lodging in an artery in the brain, and blocking off blood supply; this is an embolism and it results in a stroke. This type of stroke is called an embolic stroke, or more specifically, a cardio-embolic stroke.
Atrial fibrillation and heart failure: What’s the connection?
Atrial fibrillation can lead to heart failure, and vice-versa. Here’s how: rapid heartbeats prevent efficient blood pumping. As a result, some blood flows backwards into the pulmonary vein that, normally, brings oxygen-rich blood from the lungs to the heart. When blood backflow reaches the lungs, it further deprives the heart of fresh blood.
Fluid also can build up in the feet, ankles, and legs, causing heart-failure related weight gain.
So, even though your heart is working hard, your body is still experiencing oxygen deprivation.
Moreover, a rapid heartbeat can stretch and scar the cardiac muscles that become unresponsive to electrical impulses, further deteriorating the condition.
All of this sets the stage for heart failure.
An atrial fibrillation episode may be temporary and resolve on its own (spontaneous remission), or it may be persist and require more than just medications for its treatment. Whatever may be the case, a constant professional monitoring of the condition is required, as it is symptomless in most people.
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