KCNH2 rs1805123: What Your Genotype Means
The rs1805123 variant, also known as K897T, is a common genetic change in the KCNH2 gene. It is studied for its association with variations in the heart's electrical cycle, specifically the QT interval, and its potential role in how individuals respond to certain medications.
What each genotype means
Typical repolarization profile
You carry two copies of the common A allele (encoding lysine at position 897, often designated K897). In large observational cohorts, this genotype represents the baseline cardiac repolarization profile, although some studies report minor baseline QT interval variations compared to C allele carriers. If you are ever prescribed medications that can prolong the QT interval, discuss potential drug interactions and monitoring with your clinician or pharmacist.
Carried by approximately 70% to 85% of individuals worldwide, making it the most frequent genotype across European, African, and Asian ancestries.
Altered potassium channel kinetics
You carry one copy of the C variant (encoding the K897T missense change) in the KCNH2 potassium channel gene. Research has associated this genotype with subtle shifts in ventricular repolarization and modest changes in QT interval duration, though published findings remain mixed regarding whether it slightly shortens or prolongs the QT interval. Because KCNH2 channels are primary targets for drug-induced QT prolongation, consult your doctor or pharmacist prior to taking medications with known arrhythmia risks.
Carried by roughly 15% to 25% of people in European and American populations, and approximately 8% to 15% in East Asian and African ancestries.
Altered channel kinetics homozygous
You carry two copies of the C variant (homozygous for the K897T alteration) in the KCNH2 gene. Research shows that two copies of this variant can alter hERG channel gating kinetics and cellular repolarization characteristics, though clinical studies report conflicting effects on baseline QT interval duration and susceptibility to drug-induced arrhythmias. Always discuss medication safety and cardiac monitoring with your healthcare provider or pharmacist when starting any drugs associated with QT interval changes.
Carried by approximately 1% to 3% of individuals globally, remaining relatively uncommon across all major continental populations.
Understanding the rs1805123 Variant
The rs1805123 variant is a single nucleotide polymorphism (SNP) located within the KCNH2 gene. In scientific literature, this specific change is frequently referred to as K897T, which describes a substitution of the amino acid lysine (K) with threonine (T) at position 897 of the resulting protein. Because this variant is common in the general population, it is classified as a polymorphism rather than a rare disease-causing mutation. It sits in a region of the gene that encodes a critical component of the heart's electrical system, leading researchers to investigate whether this small change in the genetic code influences how the heart functions under normal conditions or when exposed to specific environmental stressors, such as certain pharmaceutical drugs.
The Role of the KCNH2 Gene
The KCNH2 gene provides instructions for making a protein called Kv11.1, which is a subunit of a voltage-gated potassium channel. These channels are essential for the proper electrical activity of the heart, specifically for the repolarization phase of the cardiac action potential. This phase allows the heart muscle cells to reset their electrical charge after each beat. When these channels function correctly, they help maintain a steady and healthy heart rhythm. Because the Kv11.1 channel is so vital, it is a common target for various medications. If a drug blocks or alters the function of these channels, it can lead to a prolongation of the QT interval, which is the time it takes for the heart to recharge between beats.
Research and Clinical Associations
Research into rs1805123 has produced mixed findings regarding its clinical impact. Some studies have observed a statistical association between the presence of the variant and a slightly longer QT interval, while others have explored its role as a genetic modifier that might influence the severity of Long QT Syndrome (LQTS) in individuals who also carry other, more significant mutations. The evidence for this variant is considered moderate, as the observed effects on QT duration are often small and can be influenced by other genetic and environmental factors. Because of these inconsistencies, it is not currently used as a standalone diagnostic tool. It is important to note that having this variant does not mean an individual will experience heart rhythm issues, as many people with the variant have perfectly normal cardiac function.
Navigating Your Genetic Information
If you have information about your rs1805123 genotype, it is important to view it in the context of your overall health. This variant is a common genetic feature and is not a medical diagnosis. Because the association with drug-induced QT prolongation is complex and influenced by many factors—including other medications, electrolyte levels, and underlying health conditions—you should never make changes to your prescribed medications based on this information. If you are concerned about how your genetics might influence your response to specific drugs, the best course of action is to discuss your concerns with your physician or a pharmacist. They can provide personalized guidance based on your full medical history and current clinical needs.
How common is this variant?
The rs1805123 variant is a common polymorphism with varying allele frequencies observed across different global populations.
Frequently asked questions
Does having the rs1805123 variant mean I have Long QT Syndrome?
No, having this variant does not mean you have Long QT Syndrome. It is a common genetic polymorphism that may slightly influence the duration of your QT interval, but it is not a diagnostic marker for the condition.
Should I avoid certain medications if I have this variant?
You should not avoid or change any medications based on this genetic information. Always consult with your doctor or pharmacist before making any changes to your treatment plan, as they can evaluate your specific health risks.
Is the rs1805123 variant considered dangerous?
The variant is not inherently dangerous. It is a common genetic variation found in many healthy individuals, and its clinical significance is generally considered to be minor or dependent on other factors.
How can I find out if I have this variant?
This variant may be included in some direct-to-consumer genetic testing reports or clinical genomic sequencing. If you have results, you can review them with a healthcare provider to understand what they mean for your specific health context.
Sources & further reading
Educational information only, last refreshed 10/17/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Pathogenic missense substitution (c.1841C>T, p.Ala614Val) within the pore-forming domain of KCNH2, causing potassium channel impairment (hERG) and predisposing to autosomal dominant Long QT syndrome type 2 (LQT2).
This variant in the KCNH2 gene is a well-documented SNP tracked across major genomic databases for its potential clinical relevance.