Credible Meds has a great website and app on which you can check drugs that cause QT prolongation. It is important to do this, especially if you are already on drugs that prolong QT interval since combination of 2 drugs that do this can cause lethal arrhythmias.
Grapefruit juice causes QT prolongation related to blocking of HERG channels by naringenin (a flavinoid).
Anti-arrhythmic drugs used for AFIB patients can prolong QT interval. Grapefruit juice should be avoided by all arrhythmia patients since it can interact with the drugs and cause a life threatening arrhythmia called torsades de pointes.
