SCN5A rs3807992: Cardiac Conduction and PR Interval
The single nucleotide polymorphism rs3807992 is a common noncoding variant residing in an intronic regulatory enhancer region of the SCN5A gene. This variant has been repeatedly identified in genome-wide association studies for its association with electrocardiographic traits, specifically modulating PR interval duration and cardiac conduction speed. Because it is a common regulatory variant with subtle physiological effects, its evidence strength regarding overt clinical disease predisposition remains classified as limited.
What each genotype means
Typical baseline cardiac conduction
Individuals with two copies of the C allele show standard cardiac sodium channel expression and average PR interval durations on electrocardiograms. Large genome-wide association studies link this baseline genotype with typical atrioventricular electrical conduction velocities and no elevated risk for conduction delays. Because this finding reflects population-level statistical traits rather than a medical diagnosis, it does not confirm the absence of cardiovascular conditions.
Carried by approximately 36% of individuals of European ancestry and roughly 25% of individuals of East Asian ancestry.
Slightly prolonged PR interval
Carriers of one T allele typically exhibit modest alterations in intronic enhancer activity for SCN5A, which is associated with a slightly longer PR interval on an electrocardiogram. While published association studies suggest this genotype confers a modest tendency toward slower atrioventricular conduction, the effect size is subtle and does not determine clinical disease on its own. Any concerns about heart rhythm, conduction abnormalities, or cardiac symptoms should be evaluated in a clinical setting.
Found in about 48% to 50% of individuals across both European and East Asian populations.
Prone to PR prolongation
Individuals with two copies of the T allele carry the highest non-coding modifier effect at this locus, which has been consistently associated with prolonged PR interval duration and altered cardiac conduction properties in population studies. Current research indicates that while this genotype confers a statistically measurable predisposition to conduction delays, clinical penetrance is low and largely shaped by broader polygenic background and cardiovascular health. This is an informational predisposition marker rather than a diagnostic finding.
Carried by approximately 16% of individuals of European ancestry and about 25% of individuals of East Asian ancestry.
Genomic Location and Variant Characteristics
The single nucleotide polymorphism rs3807992 is located on chromosome 3 within an intronic region of the SCN5A gene. Rather than altering the amino acid sequence of the encoded protein, this variant is situated within an active cardiac regulatory enhancer sequence. Enhancer elements function as binding platforms for transcription factors and other nuclear proteins that fine-tune the timing and quantity of RNA transcription. Molecular investigations suggest that the distinct alleles at this locus, typically involving an exchange between adenine and guanine (often cataloged as A and G, or T and C depending on the chromosomal strand orientation), subtly modify local transcription factor recruitment. Because it does not disrupt an open reading frame or cause premature protein truncation, rs3807992 acts as a quantitative regulatory modifier rather than a high-penetrance monogenic switch.
The Role of SCN5A and the Nav1.5 Channel
The SCN5A gene encodes the alpha subunit of Nav1.5, the primary voltage-gated sodium channel responsible for generating the rapid upstroke (Phase 0) of the cardiac action potential. Expressed abundantly across atrial tissue, the ventricular myocardium, and specialized conduction pathways such as the bundle branches and Purkinje fibers, Nav1.5 governs how rapidly electrical impulses spread through the heart. When sodium channel density or kinetics change even modestly, the speed of myocardial depolarization shifts accordingly. Rare pathogenic coding mutations in SCN5A that severely impair channel gating can trigger severe monogenic channelopathies, including Brugada syndrome, type 3 long QT syndrome, or progressive cardiac conduction defects. In contrast, noncoding variants like rs3807992 primarily exert nuanced, continuous adjustments to channel density, influencing common physiological variation across healthy populations.
Electrocardiographic Associations and Strength of Evidence
Large-scale genome-wide association studies (GWAS) assessing electrocardiographic traits have consistently identified rs3807992 as a locus linked to variability in the PR interval. The PR interval on an electrocardiogram measures the elapsed time from the onset of atrial depolarization to the start of ventricular depolarization, directly reflecting atrioventricular nodal and intra-atrial conduction velocity. The association between rs3807992 and subtle millisecond-level shifts in PR duration is statistically robust across large population cohorts. However, the variant's classification under disease predisposition carries limited evidence strength. While individuals carrying the conduction-slowing allele show statistically lengthened conduction times, this polygenic effect rarely causes independent clinical pathology, such as advanced heart block or spontaneous arrhythmia, in the absence of other structural or genetic factors.
Population Distribution and Ancestral Patterns
Unlike rare pathogenic alleles that are tightly restricted or subject to negative selective pressure, rs3807992 is widespread in human populations worldwide. According to broad sequencing databases such as gnomAD, the minor allele frequency is substantial across major continental ancestries, registering around 0.40 in European ancestry cohorts and reaching approximately 0.50 among East Asian populations. Frequencies can vary across other global groups, reflecting historical demographic patterns and genetic drift. The widespread presence of both major and minor alleles indicates that carrying a PR-interval-prolonging allele is an exceptionally common physiological variation rather than an anomalous finding. Consequently, high allele prevalence reinforces that this locus represents normal human phenotypic variation rather than an inherently pathogenic mutation.
Clinical Perspective and Navigating Your Results
Learning your rs3807992 genotype provides insight into normal human biological diversity and subtle differences in electrical conduction traits, but it cannot diagnose any medical condition. An association with minor conduction adjustments does not mean an individual will experience symptomatic bradycardia, atrioventricular block, or heart disease. Direct-to-consumer genetic profiles should never be used to initiate, alter, or discontinue cardiac medications, including antiarrhythmic therapies or beta-blockers, without professional medical evaluation. If you have personal symptoms such as syncope, lightheadedness, or palpitations, or a documented family history of premature cardiac arrest or arrhythmias, you should consult a licensed healthcare provider, cardiologist, or genetic counselor for formal clinical testing.
How common is this variant?
The minor allele at rs3807992 is common globally, displaying an allele frequency of approximately 0.40 in European ancestral groups and about 0.50 in East Asian populations.
Frequently asked questions
Does having the rs3807992 variant mean I have heart disease?
No. The rs3807992 variant is a common noncoding marker linked to modest, normal shifts in electrical conduction velocity across entire populations. It does not serve as a diagnostic marker for heart block, cardiomyopathy, or arrhythmia.
What is the PR interval and why does it matter?
The PR interval is a standard measurement on an electrocardiogram (ECG) that tracks how quickly an electrical signal travels from the top chambers of the heart (atria) to the bottom chambers (ventricles). Modest differences in this interval are typical among healthy people, though marked abnormalities can signify conduction system disease.
Can rs3807992 predict my response to heart medications?
Currently, rs3807992 is not recognized by clinical pharmacogenomics guidelines (such as CPIC or PharmGKB) as an actionable guide for drug selection or dosing. Anyone with questions regarding medications that alter cardiac conduction should speak with their physician or pharmacist.
Why is the evidence strength for this variant listed as limited?
While the statistical association between rs3807992 and minor variations in PR interval duration is well-demonstrated in research studies, the evidence that this variant directly causes overt medical disease on its own is weak. It represents one of many subtle polygenic factors rather than an established disease mutation.
Sources & further reading
Educational information only, last refreshed 9/11/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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