B-vitamin Treatment Modifies the Mortality Risk Associated with Calcium Channel Blockers in Patients with Suspected Stable Angina Pectoris: A Prospective Cohort Study

BACKGROUND: Calcium channel blockers (CCBs) are used for the treatment of cardiovascular disease (CVD), including angina pectoris, and hypertension; however, the effect on survival remains uncertain. CCBs impair fibrinolysis and have been linked to elevated plasma homocysteine (Hcy), a CVD risk marker. OBJECTIVE: We explored the association between CCB use and mortality in a large prospective cohort of patients with suspected stable angina pectoris (SAP), and potential effect modifications by Hcy-lowering B-vitamin treatment (folic acid, B(12), and/or B(6)) as 61.8% of the patients participated in a randomized placebo-controlled B-vitamin intervention trial. METHODS: Patient baseline continuous characteristics according to CCB treatment were tested by linear regression. Hazard ratios (HRs) for mortality associated with CCB treatment, also according to B-vitamin intervention, were examined using Cox regression analysis. The multivariable model included CVD risk factors, medical histories, and the use of CVD medications. RESULTS: A total of 3991 patients (71.5 % men) were included, of whom 907 were prescribed CCBs at discharge. During 10.3 years of median follow-up, 20.6% died and 8.9% from cardiovascular- and 11.7% from non-cardiovascular causes. Patients treated with CCBs had higher plasma Hcy, fibrinogen levels, and erythrocyte sedimentation rate (all P<0.001). Furthermore, CCB use was positively associated with mortality, also after multivariable adjustments (HRs [95% CIs]: 1.34 [1.15,1.57], 1.35 [1.08,1.70], and 1.33 [1.09,1.64] for total, CVD, and non-CVD death, respectively). Numerically stronger associations were observed among patients not treated with B-vitamins (HR [95% CI]: 1.54 [1.25, 1.88], 1.69 [1.25, 2.30], and 1.41 [1.06, 1.86] for total, CVD deaths, and non-CVD deaths, respectively), whereas no association was seen in patients treated with B-vitamins (HR [95% CI]: 1.15 [0.91, 1.46], 1.09 [0.76, 1.57], and 1.20 [0.88, 1.65]). CONCLUSIONS: In patients with suspected SAP, CCB treatment was associated with increased mortality risk primarily among patients not treated with B-vitamins.