27 patients aged 5-28 yrs. with Thal were studied by exercise testing (ET) (Bruce protocol) and by M mode echocardiography (Echo). Hemoglobin (Hgb) was determined 1 hr. prior to ET. 19/27 had no digitalis therapy (DIG). Endurance time: 16/27 had low endurance time (END) (<80% of predicted mean [PM] for age); all patients with Hgb<11 gms.%, 5/6 boys and 4/7 girls≥15 yrs., and 4/8 boys and 2/6 girls<15 yrs. had low END. END was not predictable by ejection fraction (EF) on Echo nor related to DIG. Heart rate response (HR): 8/27 (2 boys, 6 girls) had decreased HR (>2 standard deviations below the PM) at maximal exercise (ME), not related to age or Hgb. 4/27 (2 boys, 2 girls) had increased HR at ME, not related to age or Hgb. EF and left ventricular internal diameter shortening on Echo were not predictors of HR. Dysrhythmias: 1/27 developed ventricular premature contractions (runs of 2 or 3) not seen on 24 hr. taping or standard ECG. 1/27 showed atrial premature beats. 1/27 on DIG showed sinus arrests during recovery. ST segments-T waves: No changes of ischemia were noted.

Conclusions: (a) 60% of patients with Thal showed decreased END that correlated with decreased Hgb (<11 gms.%); (b) HR was not related to Hgb, age or DIG and was unexpectedly low in 1/3 of the patients; (c) myocardial function by Echo was not a predictor of exercise response; (d) an ischemic response was not identified; (e) dysrhythmias were uncommon; (f) Echo and ET showed less myocardial dysfunction than expected by the natural history of Thal with acquired hemachromatosis.

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Klein, A., Kluger, J., Markenson, A. et al. 124 DYNAMIC EXERCISE TESTING WITH ECHOCARDIOGRAPHY CORRELATES IN THALASSEMIA MAJOR (Thai). Pediatr Res 12, 384 (1978). https://doi.org/10.1203/00006450-197804001-00129

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