Fig. 1. Representative ECG tracings from LE-Cu⁺ (a), LE-Cu- (b), SHHF-Cu⁺ (c), and SHHF-Cu- (d) rats. Primary S-T segment changes occurred in one LE-Cu- animal (b) and one SHHF-Cu⁺ animal (not pictured). The LE-Cu- group (b) and the SHHF groups (c and d) showed a higher incidence of notching of the QRS complex (c, *) when compared to the LE-Cu⁺ group. The SHHF-Cu- (d) group had a significant increase in the duration of the QRS complex when compared to other groups. Vertical bars represent 1 mV; horizontal bars represent 100 ms.