Atrial fibrillation and atrial flutter are two common rhythm abnormalities of the heart.
The heart contracts rhythmically. There are autonomic pacemakers in the heart. They are SA node and AV node. SA node is located in the right atrium. It discharges rhythmically at a rate of 60-100 beats per minute. If SA node does no function, AV node takes over. AV node is located close to the tricuspid valve. AV node discharges at a rate of 40-60 beats per minute. The AV node has a refractory period in which it does not transmit impulses. If two impulses reach the AV node it will transmit the first one. If the second one reaches the AV node during the refractory period, the AV node will not transmit it. If AV node also does not function properly, the Purkinje fibers (bundle of His) takes over. Nerves and hormones control heart rate. Parasympathetic nerve impulses coming along the Vagus nerve slow the heart rate down. Adrenalin, noradrenaline increase the heart rate. Dopamine increases the heart rate, as well as the force of contraction. Drugs can speed up or slow down heart rate. Dopamine, dobutamine, and adrenalin are commonly used to treat cardiogenic shock. Atenolol, propranolol, and labetolol slow the heart down.
What is Atrial Fibrillation?
In atrial fibrillation multiple sites in the right atrium act as pacemakers. These loci discharge haphazardly. The rate of discharge is less than 200 beats per minute. Therefore, the AV node transmits all impulses. Because these impulses reach the ventricles irregularly, the pulses are irregular. Coronary heart disease, heart failure, cardiomyopathies, drugs, and hyperthyroidism are a few known atrial fibrillation causes. Atrial fibrillation ECG shows an irregular cardiac rhythm on the rhythm strip. Otherwise, the trace is normal, and there is a P wave.
Atrial fibrillation symptoms include palpitations, dizziness, and poor exercise tolerance. Rate control and rhythm control with beta blockers and digoxin are effective treatment for atrial fibrillation. Atrial fibrillation leads to poor contraction of the right atrium. This stagnates the blood in the right atrium. Stagnation leads to clot formation. These clots break up into small pieces and shoot up to block arteries. Stroke, amorousis fugax, and retinal hemorrhages can develop due to these emboli. (You may also be interested in reading the Difference Between Thrombosis and Embolism)
What is Atrial Flutter?
Atrial flutter causes a rapid heart rate around 200 beats per minute. Due to some reason SA node fires off at an alarming rate. Even if the discharge rate is above 200 beats per minute, the refractory period prevents impulse transfer. Atrial flutter ECG does not have a P wave. The baseline appears like the edge of a saw (Saw tooth appearance). Heart muscle receives blood during diastole. The heart rate rises as diastole shortens, and myocardial blood supply drops. Atrial flutter symptoms include chest pain, palpitations, and dizziness. Digoxin is an effective treatment for atrial flutter, as well.
What is the difference between Atrial Fibrillation and Atrial Flutter?
• Fibrillation has a slow heart rate while flutter rate is around 200 beats per minute.
• Fibrillation is due to haphazardly discharging foci and flutter is due to rapid discharge of SA node.
• Both cause palpitations, chest pain, and dizziness.