Table 1
Environmental triggers and medications that can unmask inherited arrhythmia syndromes. SCD: sudden cardiac death
| SYNDROME | ENVIRONMENTAL TRIGGERS | MEDICATIONS THAT MAY UNMASK OR WORSEN ARRHYTHMIA | CLINICAL NOTES |
|---|---|---|---|
| Long QT Syndrome (LQTS) | Physical exercise (especially swimming in LQT1), emotional stress or sudden auditory stimuli (LQT2), rest or sleep (LQT3), electrolyte imbalance (hypokalemia, hypomagnesemia) | QT-prolonging drugs such as macrolide antibiotics, fluoroquinolones, certain antipsychotics, antidepressants, and class IA/III antiarrhythmics | Avoid QT-prolonging medications; correction of electrolyte abnormalities is essential |
| Brugada Syndrome (BrS) | Fever, increased vagal tone, large meals, alcohol intake | Sodium channel-blocking drugs such as ajmaline, flecainide, procainamide; certain psychotropic drugs and anesthetics | Fever should be treated promptly; drug avoidance lists are available (eg, brugadadrugs.org) |
| Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) Ca²+Release Deficiency Syndrome | Physical exercise, emotional stress, catecholamine release SCD or aborted SCD without exercise-induced syncope | Sympathomimetic agents (eg, epinephrine, dopamine), stimulants | Strict exercise restriction and avoidance of adrenergic stimulants are recommended Exercise test mostly negative No induction of complex arrhythmias |
| Short QT Syndrome (SQTS) | Less clearly defined; may occur during rest or increased sympathetic tone | Drugs that further shorten the QT interval (rare) | Quinidine may be used to prolong QT interval and suppress arrhythmias |
Table 2
Genetic mechanisms contributing to atrial fibrillation. AF: atrial fibrillation
| GENE/LOCUS | GENE FUNCTION | MECHANISM CONTRIBUTING TO AF |
|---|---|---|
| PITX2 | Transcription factor regulating cardiac development and left–right asymmetry | Alters electrical patterning of the left atrium and pulmonary veins, increasing susceptibility to AF |
| SCN5 A | Cardiac sodium channel (Nav1.5) | Alters atrial depolarization and conduction velocity |
| KCNQ1 | Potassium channel involved in cardiac repolarization | Shortens atrial action potential duration, promoting reentry |
| KCNE2 | Potassium channel regulatory subunit | Modifies repolarizing currents and atrial electrophysiology |
| NPPA | Encodes atrial natriuretic peptide | Influences atrial remodeling and fibrosis |
| GJA5 | Connexin 40 (gap junction protein) | Disrupts intercellular electrical coupling in atrial myocardium |