Calcium channel blockers for preventing cardiomyopathy due to iron overload in people with transfusion-dependent beta thalassaemia

Background Beta-thalassaemia is an inherited blood disorder that reduces the production of haemoglobin. The most severe form requires recurrent blood transfusions, which can lead to iron overload. Cardiovascular dysfunction caused by iron overload is the leading cause of morbidity and mortality in people with transfusion-dependent beta-thalassaemia. Iron chelation therapy has reduced the severity of systemic iron overload, but removal of iron from the myocardium requires a very proactive preventive strategy. There is evidence that calcium channel blockers may reduce myocardial iron deposition. This is an update of a Cochrane Review first published in 2018. Objectives To assess the effects of calcium channel blockers plus standard iron chelation therapy, compared with standard iron chelation therapy (alone or with a placebo), on cardiomyopathy due to iron overload in people with transfusion-dependent beta thalassaemia. Search methods We searched the Cochrane Haemoglobinopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books, to 13 January 2022. We also searched ongoing trials databases and the reference lists of relevant articles and reviews. Selection criteria We included randomised controlled trials (RCTs) of calcium channel blockers combined with standard chelation therapy versus standard chelation therapy alone or combined with placebo in people with transfusion-dependent beta thalassaemia. Data collection and analysis We used standard Cochrane methods. We used GRADE to assess certainty of evidence. Main results We included six RCTs (five parallel-group trials and one cross-over trial) with 253 participants; there were 126 participants in the amlodipine arms and 127 in the control arms. The certainty of the evidence was low for most outcomes at 12 months; the evidence for liver iron concentration was of moderate certainty, and the evidence for adverse events was of very low certainty. Amlodipine plus standard iron chelation compared with standard iron chelation (alone or with placebo) may have little or no effect on cardiac T2* values at 12 months (mean difference (MD) 1.30 ms, 95% confidence interval (CI) -0.53 to 3.14; 4 trials, 191 participants; low-certainty evidence) and left ventricular ejection fraction (LVEF) at 12 months (MD 0.81%, 95% CI -0.92% to 2.54%; 3 trials, 136 participants; low-certainty evidence). Amlodipine plus standard iron chelation compared with standard iron chelation (alone or with placebo) may reduce myocardial iron concentration (MIC) after 12 months (MD -0.27 mg/g, 95% CI -0.46 to -0.08; 3 trials, 138 participants; low-certainty evidence). The results of our analysis suggest that amlodipine has little or no effect on heart T2*, MIC, or LVEF after six months, but the evidence is very uncertain. Amlodipine plus standard iron chelation compared with standard iron chelation (alone or with placebo) may increase liver T2* values after 12 months (MD 1.48 ms, 95% CI 0.27 to 2.69; 3 trials, 127 participants; low-certainty evidence), but may have little or no effect on serum ferritin at 12 months (MD 0.07 mu g/mL, 95% CI -0.20 to 0.35; 4 trials, 187 participants; low-certainty evidence), and probably has little or no effect on liver iron concentration (LIC) after 12 months (MD -0.86 mg/g, 95% CI -4.39 to 2.66; 2 trials, 123 participants; moderate-certainty evidence). The results of our analysis suggest that amlodipine has little or no effect on serum ferritin, liver T2* values, or LIC after six months, but the evidence is very uncertain. The included trials did not report any serious adverse events at six or 12 months of intervention. The studies did report mild adverse effects such as oedema, dizziness, mild cutaneous allergy, joint swelling, and mild gastrointestinal symptoms. Amlodipine may be associated with a higher risk of oedema (risk ratio (RR) 5.54, 95% CI 1.24 to 24.76; 4 trials, 167 participants; very low-certainty evidence). We found no difference between the groups in the occurrence of other adverse events, but the evidence was very uncertain. No trials reported mortality, cardiac function assessments other than echocardiographic estimation of LVEF, electrocardiographic abnormalities, quality of life, compliance with treatment, or cost of interventions. Authors' conclusions The available evidence suggests that calcium channel blockers may reduce MIC and may increase liver T2* values in people with transfusion-dependent beta thalassaemia. Longer-term multicentre RCTs are needed to assess the efficacy and safety of calcium channel blockers for myocardial iron overload, especially in younger children. Future trials should also investigate the role of baseline MIC in the response to calcium channel blockers, and include a cost-effectiveness analysis.