The QRS score: a promising new exercise score for detecting coronary artery disease based on exercise-induced changes of Q-, R- and S-waves: a relationship with myocardial ischaemia
Abstract
BACKGROUND: Recently, a new exercise test criterion diagnosing coronary artery disease was proposed, based on a composite of changes in Q-, R- and S-waves: the QRS score. We compared this new criterion with conventional ST-segment depression and other compositions of Q-, R- and S-wave changes in patients and normals and related the QRS score to reversible thallium-201 scintigraphic defects and ST-segment depression as markers for ischaemia. The influence of beta-blockade on the QRS score was also studied.
METHODS: The study population consisted of 155 persons with 53 normals (group I) and 102 patients with documented coronary artery disease (group II). Another 20 patients (group III) with proven coronary artery disease and a positive exercise test by ST-segment criteria were studied for the influence of beta-blockade on the QRS score. A symptom-limited exercise protocol according to the modified Bruce protocol was used. For the QRS score, Q-, R- and S-wave amplitudes which could be recovered immediately were subtracted from pretest values: delta Q, delta R, delta S respectively. The score was calculated by the formula: (delta R - delta Q - delta S)AVF + (delta R - delta Q - delta S)V5.
RESULTS: Using a cut-off point of > 5 as normal, the QRS score resulted in a sensitivity of 88.2%, a specificity of 84.8% and a predictive accuracy of 87.1%. For ST-segment depression these values were 54.9%, 83% and 64.5% respectively (P < 0.001 compared to the QRS score). Predictive…
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Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 102 participants or records.
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