title: High-frequency QRS analysis compared to conventional ST-segment analysis in patients with chest pain and normal ECG referred for exercise tolerance test.
abstract: BACKGROUND
  The novel analysis of high-frequency QRS components (HFQRS-analysis) has been proposed in patients with chest pain (CP) and normal electrocardiography (ECG) referred for exercise tolerance test (ex-ECG). The aim of the study was to compare the diagnostic value of ex-ECG with ex-HFQRS-analysis.
  
  
  METHODS
  Patients with CP and normal ECG, troponin, and echocardiography were considered. All patients underwent ex-ECG for conventional ST-segment-analysis and ex-HFQRS-analysis. A decrease ≥ 50% of the HFQRS signal intensity recorded in at least 2 contiguous leads was considered an index of ischemia, as ST-segment depression ≥ 2 mm or ≥ 1 mm and CP on ex-ECG. Exclusion criteria were: QRS duration ≥ 120 ms and inability to exercise. End-point: The composite of coronary stenosis ≥ 70% or acute coronary syndrome, revascularization, cardiovascular death at 3-month follow-up.
  
  
  RESULTS
  Three-hundred thirty-seven patients were enrolled (age 60 ± 15 years). The percent-age of age-adjusted maximal predicted heart rate was 89 ± 10 beat per minute and the maximal systolic blood pressure was 169 ± 23 mm Hg. Nineteen patients achieved the end-point. In multivariate analysis, both ex-ECG and ex-HFQRS were predictors of the end-point. The ex-HFQRS-analysis showed higher sensitivity (63% vs. 26%; p < 0.05), lower specificity (68% vs. 95%; p < 0.001), and comparable negative predictive value (97% vs. 96%; p = 0.502) when compared to ex-ECG-analysis. Receiver operator characteristics analysis showed the incremental diagnostic value of HFQRS (area: 0.655, 95% CI 0.60-0.71) over conventional ex-ECG (0.608, CI 0.55-0.66) and CP score (0.530, CI 0.48-0.59), however without statistical significance in pairwise comparison by C-statistic.
  
  
  CONCLUSIONS
  In patients with CP submitted to ex-ECG, the novel ex-HFQRS-analysis shows a valuable incremental diagnostic value over ST-segment-analysis.
authors.affiliation: Emergency Medicine and Chest Pain Unit, Department of Critical Care Medicine and Surgery, Careggi University Hospital, Florence, Italy. aaaconti@hotmail.com.
authors.forename: Alberto
authors.initials: A
authors.lastname: Conti
authors.forename: Andrea
authors.initials: A
authors.lastname: Alesi
authors.forename: Giovanna
authors.initials: G
authors.lastname: Aspesi
authors.forename: Niccolò
authors.initials: N
authors.lastname: De Bernardis
authors.forename: Simone
authors.initials: S
authors.lastname: Bianchi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Coppa
authors.forename: Chiara
authors.initials: C
authors.lastname: Donnini
authors.forename: Caterina
authors.initials: C
authors.lastname: Grifoni
authors.forename: Alessandro
authors.initials: A
authors.lastname: Becucci
authors.forename: Claudia
authors.initials: C
authors.lastname: Casula
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000787:Angina Pectoris / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D019540:Area Under Curve; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure; D016009:Chi-Square Distribution; D003324:Coronary Artery Disease / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D004452:Echocardiography; D004562:Electrocardiography; D004632:Emergency Medical Services; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011379:Prognosis; D012372:ROC Curve; D012017:Referral and Consultation; D013997:Time Factors; D014336:Troponin / Q000097:blood; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014336:Troponin