QT dispersion and principal component analysis in prehospital patients with chest pain

The objective of this study was to measure QT dispersion (QTD) and principal component analysis (PCA) ratio, using a newly developed algorithm, in a broad range of chest pain patients to determine potential value in diagnosing ischemic heart disease. The algorithm for determining QTD is based on least-square-fit technique, which has better reproducibility than threshold and simple slope methods. QTD and PCA measurements were retrospectively computer-calculated in adults with a chief or secondary complaint of chest pain or equivalent syndrome who had prehospital 12-lead ECGs acquired by paramedics. There were 2157 patients with evaluable data in the final study population. 53% were males, 47% females. Using a threshold of 46 ms, QTp global measurement had a sensitivity/specificity of 60%/90% for AMI and 28%/90% for angina. For AMI, using a threshold of 31, PCA ratio had a sensitivity/specificity of 35%/90%. These data support the contention that QTD and PCA may be useful diagnostic adjuncts for detection of ischemic heart disease.