ABSTRACT
Background In children with sickle cell anaemia (SCA), ischaemic electrocardiogram (ECG) changes occur during both vaso-occlusive crises (VOC) and the steady state. Myocardial ischaemia evidenced by an ischaemic pattern on ECG may lead to myocardial injury which is evidenced by elevated serum cardiac troponin T (cTnT). Occasionally, the myocardial injury is fatal. Aim To determine the relationship between raised serum cTnT levels and an ischaemic ECG pattern in children with SCA. Methods This was a dual study design comprising a prospective cohort study of a group of children with SCA observed during VOC and 6 weeks later during follow-up steady state, and a case-control study of SCA children and apparently healthy children. The subjects were 34 SCA children aged 5-17 years and 34 age- and sex-matched apparently healthy controls with haemoglobin genotype AA attending University of Calabar Teaching Hospital. VOC was diagnosed by clinical examination and a history of bone pain. During VOC and follow-up steady state, an ECG was performed and blood taken for serum cTnT estimation. In the apparently healthy children, only serum cTnT was estimated. Serum cTnT was analysed by electrochemiluminescence immune-assay. Ischaemic ECG was assessed using the World Heart Federation criteria. Results Twenty-eight (82.4%) SCA children had elevated serum cTnT during VOC and it was elevated in only six (17.6%) of them during the steady state. An ischaemic ECG was observed in 25 (73.5%) and 20 (58.8%) of them during VOC and the steady state, respectively. Ischaemic ECG identified SCA children with elevated cTnT during VOC (sensitivity 75%, specificity 33.3%) and the follow-up steady state (sensitivity 50%, specificity 39.3%). Measures of agreement between ECG and cTnT in detecting myocardial injury were poor during VOC (κ 0.07, p = 0.68) and the follow-up steady state (κ - 0.06, p = 0.63). Conclusions Most SCA children have an ischaemic ECG with elevated serum cTnT, especially during VOC, which suggests ischaemic-induced cardiac injury. However, elevated serum cTnT can occur without an ischaemic ECG and vice versa. Performing only electrocardiography or cTnT to detect ischaemia-induced cardiac injury may be misleading. Therefore, when there is a high index of suspicion, both tests should be undertaken, especially during VOC, to ensure prompt, effective treatment. Abbreviations AHC, apparently healthy children; AUC, area under the ROC curve; BMI, body mass index; cTnT, cardiac troponin T; ECG, electrocardiogram; EDTA, ethylene diamine tetra-acetic acid; GFR, glomerular filtration rate; HbS, haemoglobin S; HLA, human leucocyte antigen; LVH, left ventricular hypertrophy; ROC, receiver operating characteristic; SCA, sickle cell anaemia; UCTH, University of Calabar Teaching Hospital; URL, upper reference limit; USFDA, United States Food and Drug Administration; USNIH, United States National Institutes of Health; VOC, vaso-occlusive painful crisis; WHF, World Heart Federation.
