Einthoven assigned the letters P, Q, R, S and T to the various deflections that it measured and described the electrocardiographic features of a number of cardiovascular disorders.
Einthoven menuliskan huruf P, Q, R, S dan T ke sejumlah defleksi, dan menjelaskan sifat-sifat elektrokardiografi sejumlah gangguan kardiovaskuler.