What you carry at this position in your DNA and what research says about it.
QT Interval Duration: 10/10 evidence, 21 publications.
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Sample genotype (not yours): T/T
Shorter QT Interval and Faster Cardiac Repolarization
This genetic profile is associated with a shorter QT interval, indicating faster electrical recharging of the heart ventricles. It also correlates with a typical QRS duration, though it may slightly increase resting heart rate.
What this genotype means: Faster ventricular repolarization; Typical QRS conduction speed; Slightly higher resting heart rate.
Sample genotype (not yours): C/C
Longer QT Interval and Slower Cardiac Repolarization
This genotype is linked to a longer QT interval and an extended QRS duration, indicating slower electrical conduction in the heart. It also correlates with a slightly lower resting heart rate.
What this genotype means: Slower ventricular repolarization; Slightly prolonged QRS duration; Slightly lower resting heart rate.
Sample genotype (not yours): T/C
Slightly Longer QT Interval and Intermediate Conduction
An intermediate genetic profile leads to a slightly longer QT interval and marginally slower ventricular depolarization. These subtle electrical changes represent a balanced mix of cardiac conduction traits.
What this genotype means: Slightly slower ventricular repolarization; Intermediate QRS conduction speed; Typical resting heart rate.
Gene function and biological role
Gene Function: The PLN gene encodes phospholamban, a critical micropeptide that regulates calcium cycling in cardiac muscle cells [1]. In its unphosphorylated state, phospholamban inhibits the sarcoplasmic reticulum calcium ATPase (SERCA2a) pump, which actively transports calcium ions from the cytosol back into the sarcoplasmic reticulum [2]. This inhibition slows down cardiac muscle relaxation [1]. When the heart is stimulated by adrenaline, phospholamban is phosphorylated, which relieves the inhibition and allows faster calcium reuptake and rapid cardiac relaxation [2]. Genetic variations in or near this gene can alter these delicate calcium dynamics, impacting the heart's electrical intervals and overall rhythm [1].
Variant Impact: This intergenic variant is located on chromosome 6 near the PLN gene and acts as a major genetic modifier of cardiac electrical conduction [1]. The genetic change influences the expression or regulation of phospholamban, thereby subtly altering calcium handling in myocardial cells [1]. Large-scale genome-wide association studies have identified this specific variant as one of the strongest common genetic determinants of the QT interval, which measures the time required for the heart's ventricles to depolarize and repolarize [1] [3]. It also influences other electrocardiogram parameters, including the QRS duration and the PR interval, highlighting its broad role in cardiac electrical architecture [4] [5].
Key Insight: This variant is one of the strongest common genetic influences on the heart's QT interval, explaining nearly 0.74% of its total variation.
Location: PLN. Chromosome 6 · 6q22.31 · 118.3 Mb
Estimated prevalence by population
Global 37.2%; European 25.8%; African 52.4%; East Asian 58.3%; South Asian 35.2%; Americas 46.6%; Ashkenazi 33.2%; Finnish 30.3%; Middle Eastern 20.8%; Amish 33.5%.
Estimated TT genotype frequency.
Global 45.9%; European 50.0%; African 40.0%; East Asian 36.1%; South Asian 48.3%; Americas 43.3%; Ashkenazi 48.8%; Finnish 49.5%; Middle Eastern 49.6%; Amish 48.8%.
Estimated TC genotype frequency.
Global 16.8%; European 24.2%; African 7.6%; East Asian 5.6%; South Asian 16.6%; Americas 10.1%; Ashkenazi 17.9%; Finnish 20.2%; Middle Eastern 29.6%; Amish 17.7%.
Estimated CC genotype frequency.
Showing effects for T/T genotype
Cardiovascular & Metabolic
Heart Rhythm & Conduction
QT Interval. Evidence: 10/10. Source: PMID 19587794. Typical.
QRS Duration. Evidence: 9/10. Source: PMID 27659466. Typical.
Resting Heart Rate. Evidence: 8/10. Source: PMID 23583979. Slightly Higher.
PR Interval. Evidence: 8/10. Source: PMID 32439900. Slightly Longer.
Hypertension
Diastolic Blood Pressure. Evidence: 6/10. Source: PMID 35762941. Slightly Higher.
Showing effects for C/C genotype
QT Interval. Evidence: 10/10. Source: PMID 19587794. Increased.
QRS Duration. Evidence: 9/10. Source: PMID 27659466. Increased.
Resting Heart Rate. Evidence: 8/10. Source: PMID 23583979. Typical.
PR Interval. Evidence: 8/10. Source: PMID 32439900. Typical.
Diastolic Blood Pressure. Evidence: 6/10. Source: PMID 35762941. Typical.
Showing effects for T/C genotype
QT Interval. Evidence: 10/10. Source: PMID 19587794. Slightly Increased.
QRS Duration. Evidence: 9/10. Source: PMID 27659466. Slightly Increased.
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
A faster cardiac repolarization rate is characteristic of this genotype, driven by a shorter QT interval on electrocardiograms [1]. This faster electrical recovery reduces the susceptibility to certain types of ventricular arrhythmias that are triggered by delayed repolarization [1]. Additionally, the QRS duration, which measures the time it takes for electrical signals to spread through the ventricles, remains within the typical, efficient range [2]. However, this profile also correlates with a slightly higher resting heart rate and a marginally longer PR interval, which represents the conduction time between the atria and ventricles [3] [4]. These minor trade-offs are generally considered benign and fall well within normal physiological ranges [1]. Overall, the avoidance of QT interval prolongation makes this genotype highly favorable for maintaining stable cardiac electrical timing [1].
Faster ventricular repolarization; Typical QRS conduction speed; Slightly higher resting heart rate.
Sample genotype: CC (Homozygous)
Slower electrical recharging of the heart's ventricles is a hallmark of this genotype, characterized by a significantly longer QT interval on electrocardiograms [1]. This delay in repolarization is accompanied by a prolonged QRS duration, which reflects slower electrical conduction through the ventricular muscle [2]. While these changes are quantitative and usually remain within normal clinical limits, a longer QT interval is a recognized risk factor for electrical instability under certain conditions, such as when taking QT-prolonging medications [1] [3]. On the positive side, this profile is associated with a slightly lower resting heart rate and lower diastolic blood pressure, which can be protective against hypertension [4] [5]. These contrasting cardiovascular effects highlight how a single genetic variant can influence multiple aspects of heart function [1].
Slower ventricular repolarization; Slightly prolonged QRS duration; Slightly lower resting heart rate.
Sample genotype: TC (Heterozygous)
A slightly longer QT interval is observed in individuals with this heterozygous genotype, reflecting a minor delay in the heart's electrical recharging phase [1]. This intermediate effect is situated between the faster repolarization of the T/T genotype and the longer intervals of the C/C genotype [1]. Similarly, the QRS duration is marginally extended, indicating a very slight slowdown in the spread of electrical signals across the ventricles [2]. Conversely, the resting heart rate and diastolic blood pressure are slightly lower than those with the T/T genotype, offering a minor cardiovascular trade-off [3] [4]. These subtle variations in cardiac electrical timing are common in the general population and typically do not cause clinical symptoms on their own [1]. They represent the complex, polygenic nature of resting electrocardiogram parameters [1].
Slightly slower ventricular repolarization; Intermediate QRS conduction speed; Typical resting heart rate.
Variants with shared genetic architecture
rs12143842 · NOS1AP Gene · Chr 1 · QT Interval Duration
rs1805123 · KCNH2 Gene · Chr 7 · Heart Rhythm
rs2074238 · KCNQ1 Gene · Chr 11 · Cardiac QT Interval
52 Genetic Loci Influencing Myocardial Mass.
Monogenic and Polygenic Contributions to QTc Prolongation in the Population.
High Blood Pressure and Intraocular Pressure: A Mendelian Randomization Study.
Content updated August 2026.
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