Several hundred medicines lengthen the heart's recovery time as a side effect. Most people absorb it without consequence — and the reason some do not is partly written in common variants that do nothing on their own.
A mechanism with population evidence behind it and no clinical test in front of it. Several hundred medicines prolong the QT interval, and most people absorb that without consequence because the heart has spare capacity to repolarise on time. Common QT variants appear to reduce that spare capacity: a risk score built from them was associated with drug-induced QT prolongation and with torsade de pointes (Strauss et al., Circulation 2017). No society recommends genotyping before prescribing, and the factors clinicians actually act on — potassium and magnesium levels, heart rate, kidney function, other QT-prolonging drugs — matter more. Useful as an explanation of why the same drug is uneventful in most people and not in everyone.
Strauss DG et al., Common Genetic Variant Risk Score Is Associated With Drug-Induced QT Prolongation and Torsade de Pointes Risk. Circulation 2017; CredibleMeds QT drug lists
These are the positions in your own file that carry the genes above. Not every gene in a guideline is one we report — where that is the case the gene appears above without a variant here, and the note says so.