Irregular heartbeat, or arrhythmia, is a common occurrence with over 3 million cases per year in the United States alone. Most of the time, an arrhythmia is harmless and happens in those free of heart disease, but some abnormal heart rhythms can be severe and potentially deadly. Arrhythmias occur when the electrical impulses that coordinate heartbeat don’t work correctly, leading to increased, decreased, or irregular heartbeat.
Symptoms of arrhythmias include fluttering in your chest, chest pain, shortness of breath, fainting, dizziness, and racing or slow heartbeat, if you experience these symptoms frequently or at unexpected times seek urgent medical care. One type of arrhythmia that can be life-threatening is ventricular fibrillation, when the heart beats rapidly with erratic electrical impulses the heart is unable to pump blood. Ventricular fibrillation leads to an ineffective heartbeat, plummeting blood pressure, and cutting off blood supply to vital organs which can lead to death. Arrhythmia’s include various causes and risk factors such as heart tissue damage, changes in the heart structure, blocked arteries, high blood pressure, smoking, stress, and diabetes. Living a heart-healthy lifestyle, involving physical activity and a heart-healthy diet, can reduce risk of heart disease and help prevent heart arrhythmia. However, studies have shown that genetics can play a role in heart rhythm. Previous research on twins and families have shown the heritability of heart rhythm is between 40-60%.
A recent study in Nature Communications further explored the role of genetics and the heart’s electrical activity in the largest genome study of its type, involving 126 researchers at institutions across the globe. The study looked at the PR interval, part of a heart recording (electrocardiogram), which is measured in milliseconds and traces electrical conduction from the heart’s sinus node, the pacemaker of the heart, throughout the atria and to the ventricles. The PR interval begins when the atria contracts and ends when the ventricles are prepared to push blood out of the heart.
A genome-wide association study of more than 92,000 individuals of European descent looked for genetic variations or markers that were associated with particular traits related to atrial conduction. Researchers identified 44 chromosomal regions linked to the PR interval, 34 of which were previously unidentified. Further analysis of an additional 105,000 people of African and European ancestry yielded six more loci relevant to heart electrical activity. Genes in these loci are overrepresented in cardiac disease processes such as atrial fibrillation and heart block.
The genomic studied identified some developmental pathways in the heart, particularly the formation of the chambers and development of the system that allows conduction of the electrical signal through the heart, that may play a role in the origin of cardiac electrical disease. Gene regulators only found in the heart’s atrial tissues were uncovered, emphasizing the importance of analyzing genomic data in tissue types and not just blood samples. Gene transcription factors, ion channel genes, and cell junction or cell signaling proteins were identified and shown to be involved in the conduction of the heart’s electrical waves and abnormalities in these could contribute to disease. Overall, the study showed various contributing factors to cardiac electrical disease, while identifying potential targets for drug development such as transcription factors and cell-signaling or junction proteins.
To learn more about the different types of arrhythmias watch the video below!
Mayo Clinic, Heart Rhythm Society
