Evolution of the 106 long QT syndrome patients on β-blockers with a static M-FACT ≥ 2 at presentation during a mean follow-up of 9 ± 8 years. Post-diagnosis CEs on β-blockers conferring the score 1 more point, additional therapeutic interventions and CEs occurring despite therapy optimization are shown for patients maintaining or increasing the static score up to a dynamic M-FACT ≥ 2 (upper half) and for those lowering the score to <2 (lower half). Changes in QTc on β-blockers (<500/550> ms) and in patient age (<20> years) also contributed to any further shift of dynamic M-FACT (from Ref. 4 with permission).