Results of the controlled ONset Verapamil INvestigation of Cardiovascular Endpoints (CONVINCE) trial by geographical region

Objective: To examine regional differences in the Controlled ONset Verapamil INvestigation of Cardiovascular Endpoints (CONVINCE) trial. Design: Double-blind, randomized, international clinical trial. Setting: Six hundred and sixty-one clinical centers in 15 countries. Patients: Hypertensive volunteers (n = 16 602) with ≥1 additional cardiovascular risk factor, grouped into four regions: USA (n = 8144), Canada (n = 3405), Western Europe (Spain, UK, Italy, Sweden, Germany; n = 2048) or 'other' (Bulgaria, Israel, Mexico, Czech Republic, Hungary, Poland, Slovakia, Brazil; n = 2879); subgroupings included country and state/province within the USA and Canada. Interventions: Randomized to COER™-verapamil or the investigator's choice of either atenolol or hydrochlorothiazide, titrated and additional drugs added as required. Main outcome measures: Baseline characteristics; blood pressure control, medication adherence and lost-to-follow-up at 2 years; and composite primary endpoint (stroke, myocardial infarction, cardiovascular death) by regional groupings. Results: Regional differences were found at baseline for age, gender, blood pressure, percentage receiving antihypertensive drug therapy, initial choice of atenolol or hydrochlorothiazide, and risk factor profile. Blood pressure control rates increased markedly during follow-up in all regions, but varied significantly by region. Blood pressure control, medication adherence and lost-to-follow-up rates were poorest in the USA. After adjustment for baseline differences, the primary-event rate for each region was significantly lower than for the USA. Although baseline factors, blood pressure control and event rates varied by region, treatment differences did not. Conclusion: Despite differences in baseline and follow-up measures across geographical regions, the absence of treatment differences by region suggests that the overall findings of CONVINCE are robust.