Heart disease is a leading cause of death worldwide, and studies have shown that genetic factors play a significant role in its development. One way to investigate the role of genetics in heart disease is by studying identical twins. Identical twins share the same genetic makeup, making them an ideal population to study the impact of genetics on disease. Research has shown that identical twins have a higher concordance rate for heart disease compared to fraternal twins or non-twin siblings. The concordance rate refers to the proportion of identical twins who both have a certain disease or trait. Studies have found that the concordance rate for heart disease in identical twins ranges from 20-60%, depending on the study population and the specific heart disease being studied. This is higher than the concordance rate for fraternal twins or non-twin siblings, which is typically around 10-20%. This suggests that genetics play a significant role in the development of heart disease. However, it is important to note that the environment and lifestyle also play a role. Identical twins may have different lifestyle habits and environmental exposures that could contribute to the development of heart disease. There is also evidence that the heritability of heart disease varies depending on the specific type of heart disease being studied. For example, studies have shown that heritability for coronary artery disease is higher than for heart failure. This may be due to the fact that different genetic and environmental factors contribute to the development of different types of heart disease. In conclusion, identical twins provide a valuable population for studying the role of genetics in heart disease. Studies have shown that identical twins have a higher concordance rate for heart disease compared to fraternal twins or non-twin siblings, suggesting that genetics play a significant role in the development of heart disease. However, it is important to note that the environment and lifestyle also play a role and the heritability of heart disease varies depending on the specific type of heart disease being studied. Dr. A. Arrazaghi. MD,FRCPC