Background: Electrocardiography (ECG), predictive of adverse outcomes in the general population, has not been studied in cancer survivors. We evaluated the prevalence of ECG abnormalities and associations with mortality among childhood cancer survivors.
Methods: Major and minor abnormalities were coded per the Minnesota Classification system for participants in the St Jude Lifetime Cohort Study (n = 2,715) and community controls (n = 268). Odds ratios (ORs) and 95% CIs were calculated using multivariable logistic regression; and hazard ratios, using Cox proportional hazards regression.
Results: Survivors were a median age of 31.3 (range 18.4-63.8) years at evaluation and 7.4 (range 0-24.8) years at diagnosis. Prior therapies included cardiac-directed radiation (29.5%), anthracycline (57.9%), and alkylating (60%) chemotherapies. The prevalence of minor ECG abnormalities was similar among survivors and controls (65.2% vs 67.5%, P = .6). Major ECG abnormalities were identified in 10.7% of survivors and 4.9% of controls (P < .001). Among survivors, the most common major abnormalities were isolated ST/T wave abnormalities (7.2%), evidence of myocardial infarction (3.7%), and left ventricular hypertrophy with strain pattern (2.8%). Anthracyclines ≥300 mg/m2 (OR 1.7 95% CI 1.1-2.5) and cardiac radiation (OR 2.1 95% CI 1.5-2.9 [1-1,999 cGy], 2.6 95% CI 1.6-3.9 [2,000-2,999 cGy], 10.5 95% CI 6.5-16.9 [≥3,000 cGy]) were associated with major abnormalities. Thirteen participants had a cardiac-related death. Major abnormalities were predictive of all-cause mortality (hazard ratio 4.0 95% CI 2.1-7.8).
Conclusions: Major ECG abnormalities are common among childhood cancer survivors, associated with increasing doses of anthracyclines and cardiac radiation, and predictive of both cardiac and all-cause mortality.
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