Atrial Fibrillation is a common abnormal heart rhythm which is often associated with fainting, palpitations, chest pain, or congestive heart failure. This condition is identified clinically by observing an abnormal pulse, and performing an electrocardiogram. An ECG on a patient with Atrial fibrillation will show an absent P wave as well as an irregular ventricular rate.
The electrical impulses of the heart begin in the
sinoatrial (SA node), which is located in the right ventricle. Normally, this node is able to adjust the rate of impulses based on an individual's activity. The impulse travel's from the SA node through the conductive cardiac tissue of the right ventricle, where it then reaches the AV node. The AV node is considered the "electrical bridge", allowing the impulse to travel from the atria to the ventricles. Through this travel, the impulse causes the walls of the ventricles to contract, and therefore blood can be moved throughout the heart. In the case of atrial fibrillation, instead of the SA node regulating one specific rhythm, many impulses fire at once resulting in a very fast and chaotic rhythm in the atria. These abnormal electrical signals are then transferred to the AV node where they cause irregular ventricular contraction, and therefore a fast and abnormal heartbeat. The rate of impulses in the atria in a patient with atrial fibrillation can range from 300-600 beats per minute.
SNP's and Atrial Fibrillation Edit
According to 23 and me, the estimated heritability of atrial fibrillation is 62%. This means that there is a greater chance of contracting this condition due to genetic factors than environmental factors. As a result, the single nucleotide polymorphism involved is rs2200733. This SNP is located on chromosome 4 on something referred to as a "gene desert" region, signifying that there are no nearby genes. Scientists believe however that this SNP might somehow affect the closest gene PITX2. PITX2 is a protein coding gene which controls cell proliferation in a tissue specific manner. It has also been shown that this gene exerts a role in the expansion of muscle progenitors in embryonic development, specifically encoding a transcription factor involved in the development of cardiac tissue. Therefore, it is thought that a mutation in rs2200733 may directly alter PITX2, which affects the normal structure of the heart leading to a predisposition to atrial fibrillation.
Effects on the Individual Edit
Performing genetic testing allows an individual to see if they contain certain genetic factors that will predispose them to various medical conditions. Through this process, it is evident that John M. Burke is at a slighter higher risk for contracting atrial fibrillation than the rest of the population. The average risk for this condition is 27.2%, and professor Burke's risk was calculated to be 33.9%. Although the risk is slighter increased, there are still steps professor Burke can take to prevent or minimize the severity of this condition. Eating healthy is perhaps the best thing you can do for your heart. Having a good diet will help to suppress conditions such as obesity, hypertension, high cholesterol, and heart disease, which would all increase the risk of atrial fibrillation. Artificial stimulants such as caffeine or nicotine can also increase risk. Patient's predisposed who are on steroids for asthma or other inflammatory conditions may develop atrial fibrillation at a higher intensity. Lastly, any consumption of alcohol can raise the incidence of atrial fibrillation in patients who are already diagnosed. Other than installing a pacemaker, there is no cure for this illness, however these preventative measures can significantly improve the overall health of a patient, and therefore the condition itself.
1. "23andMe - Genetic Testing for Ancestry." Log In. N.p., n.d. Web. 13 Sept. 2014. https://www.23andme.com/you/journal/atrialfib/overview/
2. "Atrial Fibrillation." Wikipedia. Wikimedia Foundation, 09 Nov. 2014. Web. 13 Sept. 2014. []
3."PITX2 Gene." - GeneCards. N.p., n.d. Web. 13 Sept. 2014.http://www.genecards.org/cgi-bin/carddisp.pl?gene=PITX2
4. Nazario, Brunilda. "Atrial Fibrillation: Causes and Risk Factors." WebMD. WebMD, 21 June 2013. Web. 13 Sept. 2014. http://www.webmd.com/heart/atrial-fibrillation-stroke-11/causes-and-risks