Introduction to Myocardial Infarction
A heart attack occurs when the flow of blood to the heart is blocked, most often by a build-up of fat, cholesterol and other substances, which forms a plaque in the coronary arteries. The interrupted blood flow can damage part of the heart muscle. A heart attack, also called a myocardial infarction (MI), can be fatal. Both environmental and genetic factors contribute to the risk of having a heart attack.
During a heart attack, one of these plaques can rupture and spill cholesterol and other substances into the bloodstream. A blood clot forms at the site of the rupture. If large enough, the clot can completely block the flow of blood through the coronary artery.
Rainbow Myocardial Infarction Risk Assessment™ Test
The Myocardial Infarction Risk Assessment Test determines the genotypes of two risk markers located at chromosome 9p21. These two single nucleotide polymorphisms, or SNPs, associate with increased risks for development of myocardial infarction (heart attack) and coronary heart disease. The risk associations have been replicated in over 20 populations with over 20,000 myocardial infarction patients and 40,000 controls, including over 5000 Chinese, Japanese, Korean and other East Asian patients.
These population-based genetic risks have been shown to be independent of family history or traditional risk factors, including diabetes, hypertension, cholesterol, and obesity. Although the relative risks associated with these markers are not high, the population attributable risk is substantial due to the high frequency of carriers with the risk-associated variants. Risk assessment outcome may have implications for early prevention of the disease.
Introduction to Atrial Fibrillation
Atrial fibrillation (AF) is an irregular and often rapid heart rate that can increase your risk of stroke, heart failure and other heart-related complications.
In atrial fibrillation, the heart's two upper chambers (the atria) beat chaotically and irregularly — out of coordination with the two lower chambers (the ventricles) of the heart. The upper chambers of your heart (atria) experience chaotic electrical signals. As a result, they quiver. The atrioventricular node — the electrical connection between the atria and the ventricles — is bombarded with impulses trying to get through to the ventricles. Atrial fibrillation symptoms often include heart palpitations, shortness of breath and weakness.
The result is a fast and irregular heart rhythm. The heart rate in atrial fibrillation may range from 100 to 175 beats a minute. The normal range for a heart rate is 60 to 100 beats a minute.
Episodes of atrial fibrillation can come and go, or you may develop atrial fibrillation that doesn't go away and may require treatment. Although atrial fibrillation itself usually isn't life-threatening, it is a serious medical condition that sometimes requires emergency treatment.
Atrial fibrillation can lead to blood clots forming in the heart that may circulate to other organs and lead to blocked blood flow (ischemia).
Rainbow Atrial Fibrillation Risk Assessment™ Test
Genome-wide association studies have successfully identified chromosome 4q25 near transcription factor PITX2. The PITX2 locus encodes a transcription factor necessary for pulmonary myocardial sleeves development, and for the formation of a sinus node in the left atrium. In numerous follow-up studies with over 10,000 patients and 30,000 controls, the chromosome 4q25 risk association has been confirmed in Caucasian, Japanese, Chinese and Korean populations.
In this test, two SNPs located adjacent to the PITX2 gene were both tested for the presence of the at-risk allele. Carriers of this allele at either locations are at a higher risk of AF compared to that of the general population.
The process starts with a physician office visit at a Rainbow-authorized clinic. The clinician will order the test for the patient. DNA will be sequenced using Sanger sequencing methods at a CAP-accredited or CLIA-certified Laboratory with current ABI 3730 DNA sequencing systems.
Data analysis will be performed by the clinical and bioinformatics team at Juntendo University, Japan. Based on the allele calls and multiple publications of the lifetime risks associated with specific ethnic populations, our team determines the risk levels associated with the genotypes of the SNPs for each condition based on the patient’s specific ethnicity. A physician report will be issued by one of the medical directors at Juntendo University, Japan.
- Impact of adding a single allele in the 9p21 locus to traditional risk factors on reclassification of coronary heart disease risk and implications for lipid-modifying therapy in the Atherosclerosis Risk in Communities (ARIC) study Circ Cardiovasc Genet. 2009 June; 2(3): 279–285.
- Common Atrial Fibrillation Risk Alleles at 4q25 Predict Recurrence after Catheter-based Atrial Fibrillation Ablation. Heart Rhythm. 2013 March ; 10(3): 394–400.
- Genetic risk for atrial fibrillation could motivate patient adherence to warfarin therapy: a cost effectiveness analysis. BMC Cardiovascular Disorders (2015) 15:104
- Usefulness of single nucleotide polymorphism in chromosome 4q25 to predict in-hospital and long-term development of atrial fibrillation and survival in patients undergoing coronary artery bypass grafting. Am J Cardiol. 2011 May 15;107(10):1504-9.
- Clinical utility and functional analysis of variants in atrial fibrillation-associated locus 4q25. J Cardiol. 2017 Jan 10.
- Genetic Testing for Early Detection of Individuals at Risk of Coronary Heart Disease and Monitoring Response to Therapy: Challenges and Promises. Curr Atheroscler Rep (2011) 13:396–404
- Genetic Risk, Adherence to a Healthy Lifestyle, and Coronary Disease. N Engl J Med. 2016 Dec 15;375 (24):2349-2358.
- Genetics of coronary artery disease and myocardial infarction. World J Cardiol 2016 January 26; 8(1): 1-23
- A common variant on chromosome 9p21 affects the risk of myocardial infarction. Science. 2007 Jun 8;316(5830):1491-3.
- Association between 9p21.3 genomic markers and coronary artery disease in East Asians: a meta analysis involving 9,813 cases and 10,710 controls. Mol Biol Rep (2013) 40: 337.
- The same sequence variant on 9p21 associates with myocardial infarction, abdominal aortic aneurysm and intracranial aneurysm. Nat Genet. 2008 Feb;40(2):217-24.
- Associations Between Single Nucleotide Polymorphisms on Chromosome 9p21 and Risk of Coronary Heart Disease in Chinese Han Population. Arterioscler. Thromb. Vasc. Biol. 2008;28;2085-2089.
- Risk variants for atrial fibrillation on chromosome 4q25 associate with ischemic stroke. Ann Neurol. 2008 Oct;64(4):402-9.
- Assessment of association of rs2200733 on chromosome 4q25 with atrial fibrillation and ischemic stroke in a Chinese Han population. Hum Genet. 2009 Dec;126(6):843-9.
- Replication of the association between a chromosome 9p21 polymorphism and coronary artery disease in Japanese and Korean populations. J Hum Genet (2008) 53:357–359.
- Variants conferring risk of atrial fibrillation on chromosome 4q25. Nature. 2007 Jul 19;448(7151):353-7.
- Association between 9p21.3 genomic markers and coronary artery disease in East Asians: a meta-analysis involving 9,813 cases and 10,710 controls. Mol Biol Rep. 2013 Jan;40(1):337-43.
- 9p21 and the genetic revolution for coronary artery disease. Clin Chem. 2012 Jan;58(1):104-12.