Community Pharmacy Records Demonstrate Suboptimal Adherence to Beta Blockade in Familial Long QT Syndrome

Aim: Risk reduction in familial long QT syndrome (LQTS) relies on long-term regular beta blockade. Adherence data is scarce in this population, retrospectively reported only on day of cardiac arrest. Our aim was to document level of beta blocker adherence in patients with LQTS types 1 and 2 and determine factors associated with adherence. Method: Pharmacy dispensing data and electronic health records for 90 Auckland patients with LQTS types 1 and 2 were reviewed over a 34-month period. The medication possession ratio (MPR: proportion of follow-up days patients were dispensed beta blocker) was calculated for each patient. Adequate adherence was demonstrated by an MPR≥0.8 and ideal as MPR=1.0. Demographic and clinical features were assessed to determine if they predicted adherence. Results: Long-term beta blockers were prescribed to 74 patients (82%). Side effects were intolerable in 6 (8%) and beta blockers were stopped. MPR was calculated in the remaining 68 patients over 151.7 patient years of follow-up. Median MPR was 0.79 (range 0-1.3). Suboptimal adherence (MPR<0.8) was recorded in 35 (51%). Seven patients (10%) never took up a prescription (MPR=0). Adequate adherence was present in 33 (49%), including 9 (13%) who had ideal adherence. Age, sex, clinical presentation, family history of sudden death, ethnicity and deprivation index did not predict adherence. Conclusion: Beta blocker adherence was suboptimal in half our patients with LQTS types 1 and 2. Risk factors for non-adherence could not be identified. Further research into beta-blocker adherence is vital in this high risk population.