Variations in the amplitude of the Q wave in lead CM5 during computerised exercise stress testing were studied in 220 patients and compared with the results of coronary angiography. The average amplitude of the Q wave increases during exercise in athletes (n = 30) from 3 +/- 2.75 mm to 4.72 +/- 2.35 mm (p less than 0.01), and in subjects without coronary artery disease (n = 49) from 0.92 +/- 1.05 mm to 1.75 +/- 1.62 mm (p less than 0.01). The Q wave did not vary significantly during exercise in patients with coronary disease but without previous infarction (n = 88) (0.70 +/- 0.91 mm to 0.62 +/- 0.85 mm). The amplitude of the Q wave did tend to decrease in patients with previous myocardial infarction (n = 83) from 1.96 +/- 2.05 mm to 1.35 +/- 1.26 mm (p less than 0.05). It is therefore possible to define a new diagnostic criterion of coronary disease: "the exercise stress test is said to be positive (delta q+) when the Q wave tends to decrease or remains stable during exercise, and negative (delta q-) when the Q wave amplitude increases during exercise". This criterion was tested in 49 normal and 83 coronary patients without infarction. The sensitivity (Se) was 79 p. 100 and the specificity (Sp) 65 p. 100, so correctly classifying 74 p. 100 of patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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