We hypothesized that the patient-specific time-varying changes in the spatial and temporal variability in cardiac repolarization (quantified by spatial TT' angle), and in myocardial injury (measured by high sensitivity troponin I, hsTnI), are independently associated with each other. Spatial TT' angle on resting 12-lead ECG (transformed to vectorcardiogram) and hsTnI were measured simultaneously every 3 hours during a 12-hour observation period in a prospective cohort of emergency department patients (n=379; age 57.8±13.2y; 54% female, 64% black), diagnosed with acute coronary syndrome (ACS; n=28), acute decompensated heart failure (ADHF; n=35), or an acute non-cardiac condition (n=316). High (above median) HsTnI in ACS was characterized by significantly larger TT' angle (12±8 vs 5±2 degrees; P=0.01) 12 hours after admission, but not earlier. In adjusted multinomial logit model, spatial TT' angle was associated with ADHF (Relative Risk Ratio 6.24 (95%CI 1.32-29.57; P=0.021), but not ACS. After full adjustment for confounders in random-effect linear regression, a 10 fold increase in hsTnI in a specific study participant was associated with 1.05 (95%CI 0.19-1.92) degrees increase in spatial TT' angle. Longitudinal association of hsTnI and TT' angle was especially prominent in patients with acute non-cardiac conditions, but not in ACS or ADHF.