Usefulness of a quantitative analysis of the recovery phase patterns of the ST-segment depression in the diagnosis of coronary artery disease

Abstract

To assess the diagnostic value of the recovery phase patterns of the ST-segment depression in patients referred for chest pain. Continuous plots of ST-segment depression against heart rate during exercise and recovery were constructed within a population of 160 consecutive symptomatic patients who all had undergone catheterization (80 with > or = 1 stenosis > or = 50%). We used a new quantitative method of measurement allowing all kinds of rate recovery loops (even the so-called "intermediate" loops) to be considered for analysis. The measurements of the heart rate (HR)-adjusted ST-segment depression were performed at 20 and 60 ms from the J point, providing two different values of a quantified recovery loop index (RLI): RLI 20 and RLI 60. Both RLI showed a higher specificity (0.81 +/- 0.04 and 0.74 +/- 0.05, respectively) than did the standard criterion (0.65 +/- 0.10), but the difference was significant regarding RLI 20 only (P = 0.011). As to the sensitivity, no significant differences were found among all of the criteria (0.74 +/- 0.05, 0.80 +/- 0.04, 0.76 +/- 0.05, respectively). The timing of measurements of the RLI within the repolarization phase did not affect their overall accuracy (0.77 +/- 0.03 for both RLI). The values of the receiver-operating characteristic (ROC) curve areas were significantly greater for both RLI (0.83 +/- 0.06 and 0.84 +/- 0.06 respectively) than for the standard criterion (0.75 +/- 0.07; P < 0.02). Finally, both RLI allowed to differentiate accurately the study subjects according to the number of diseased vessels, whereas the standard criterion could only distinguish between CAD patients and subjects with normal angiograms. The quantitative analysis of the rate recovery phase patterns appears to be useful for the diagnosis of coronary heart disease and the assessment of its severity in symptomatic patients.