An increase was observed in the number of abnormal S waves (baseline 4 [2;7]; follow-up 7 [3;11] leads; P = .002), and a nonsignificant trend in the amount of abnormal T waves (baseline 3 [0;19]; follow-up 13 [0;29] leads; P = .058).
A clear trend was observed where the number of leads with abnormal amplitudes increased per disease stage; the lowest number of abnormal leads was observed in the presymptomatic stage, whereas the highest number of abnormal leads was observed in the structural stage (R wave 2 [1;5] vs 9 [5;16] leads, P = .004; S wave 4 [1;6] vs 7 [5;12] leads, P = .022; T wave 0 [0;4] vs 20 [10;29] leads, P < .001).