CVC Case Examples

Dilated Cardiomyopathy (DCM), as read in its name, is a disease of the heart muscle primarily affecting the left ventricle which is the main cardiovascular muscle involved in pumping blood throughout the body. In DCM the left ventricle is enlarged or ‘dilated’ and the walls thin out which leads to inefficient blood flow throughout the body [http://www.heartregistry.org.au/patients-families/genetic-heart-diseases/familial-dilated-cardiomyopathy/].

Normal heart vs. Heart with DCM

Generally, DCM is known to be an inherited disease that runs in families. However, recent findings in the genetic origin of the disease have shown that DCM may be caused by certain pathogenic genes that were discovered while studying idiopathic and other non-inherited DCM patients – such as those arising from alcoholism and chemotherapy [https://doi.org/10.1016/j.hlc.2019.11.018]. This was a recent revelation due to the heterogenous nature of the disease whether it be in its symptoms, how it manifests in patients and even in genes – meaning that different patients exhibit widely different genotypic and phenotypic traits which make it hard to pinpoint the specific genetic origins of the disease. Nevertheless, certain attributes of the disease have made researchers suspect the underlying genetic basis of the disease – the most concrete evidence being the extra-cardiac*

symptoms of the disease. These include skeletal myopathy, neurological defects, lipodystrophy, dysmophism, and intellectual disability. In short, it just means that the fact that this cardiovascular disease had sometimes presented itself with non-cardiovascular symptoms have made geneticists certain that there should be an underlying genetic explanation for the manifestation of the disease.

Why exactly is this important?

DCM being a genetic disease opens up an entire world of genetic diagnosis and treatments that may not have been considered before. This increases the chances of it being diagnosed earlier and thus being prevented. It also increases the pool of treatments available for patients with DCM.

Familial Atrial Fibrillation

Familial Atrial Fibrillation (FAF), is the most common clinical tachyarrhythmia*

disease. Arrhythmia is a cardiovascular disease pertaining to having an abnormal cardiac rhythm. Having a steady heart rhythm is important in making sure that blood pumps throughout the body steadily and in the most efficient way possible. Tachyarrhythmia is simply an arrhythmia disease that is specific to having a faster heart rate than normal. Arrhythmia may be subdivided into [https://www.cedars-sinai.org/health-library/diseases-and-conditions/f/familial-arrhythmia-syndromes.html]:

Increased research into FAF genetic variants have gained valuable results which revealed the various genetic variants that may lead to FAF. Thus, currently FAF as a disease has been put under the field of personalized medicine.

Generally, inherited or familiar AF does not show any sign of increased severity or increased morbidity compared to non-FAF. However, disease risk studies show that patients with the specific 4q25 SNP rs2200733 had an increased risk of developing recurrent AF even after treatment. While these breakthroughs in studying the correlation between genotype and various AF treatments are good, there is still much to improve in diagnosing FAF patients and predicting the likelihood of developing the disease as well as its severity. On another side of these studies is the discovery that patients with certain genotypes – such as β1AR Arg389Arg genotype have been found to be more responsive to antiarrhythmic drugs and thus, require lower doses. This is massively helpful in personalizing treatment for these patients, however clinical use of this is still limited [https://www.frontiersin.org/articles/10.3389/fcvm.2020.00014/full].

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