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Baseline Q Waves and Time From Symptom Onset to ST-segment Elevation Myocardial Infarction: Insights From PLATO on the Influence of Sex

      Abstract

      Background

      The prognostic value of time from symptom onset to reperfusion may be enhanced by the identification of Q waves on the presenting electrocardiogram (ECG) in patients with ST-segment elevation myocardial infarction (STEMI). We evaluated whether the relative prognostic utility of these 2 metrics was altered by sex.

      Methods

      Q waves in the distribution of the ST-segment elevation on the baseline ECG were evaluated by a blinded core laboratory in 2838 STEMI patients (2163 men and 675 women) from the PLATelet inhibition and patient Outcomes (PLATO) trial who underwent percutaneous coronary intervention (PCI) within 12 hours of symptom onset.

      Results

      Women were older (median 63 vs 57 years), more likely to be diabetic (24.1% vs 15.5%), hypertensive (69.2% vs 50.9%), and a higher Killip class > I (8.6% vs 5.9%), as compared with men. Whereas the Q waves frequency rose progressively over time to ECG in men, this relationship was attenuated in women (P = .057). Q waves on the baseline ECG were associated with a higher excess hazard of 1-year vascular death in men (hazard ratio [HR] 2.03; 95% confidence interval [CI], 1.13-3.72), and a similar trend existed in women (HR 1.97; 95% CI, 0.86-4.51). Women with baseline Q waves tended to have higher risk of 1-year vascular death than men as continuous time from symptom onset to PCI increased (P[interaction] = .182).

      Conclusions

      These differences in the evolution of baseline Q waves and relationship between time from symptom onset and vascular death in women and men deserve recognition in future studies of STEMI.

      Keywords

      Clinical Significance
      • Women with ST-segment elevation myocardial infarction presented later after symptom onset and exhibited baseline Q waves more often than men.
      • As time from symptom onset to the baseline electrocardiogram unfolded, there was a steep increase in the occurrence of Q waves, which was attenuated in women.
      • Among men with baseline Q waves, there was an excess of 1-year vascular death, and also a trend for them to have greater mortality when they presented at a later time from symptom onset to percutaneous coronary intervention (> 3 hours). A similar trend was observed in women.
      Myocardial necrosis is the major determinant of outcomes of ST-segment elevation myocardial infarction (STEMI).
      • Antman E.M.
      • Anbe D.T.
      • Armstrong P.W.
      • et al.
      ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction—executive summary.
      Although the time that elapses between symptom onset and reperfusion has been shown to be a strong predictor of myocardial necrosis in a variety of studies,
      • The Global Use of Strategies to Open Occluded Coronary Arteries in Acute Coronary Syndromes (GUSTO IIb) Angioplasty Substudy Investigators
      A clinical trial comparing primary coronary angioplasty with tissue plasminogen activator for acute myocardial infarction.
      • Andersen H.R.
      • Nielsen T.T.
      • Rasmussen K.
      • et al.
      A comparison of coronary angioplasty with fibrinolytic therapy in acute myocardial infarction.
      • Armstrong P.W.
      • Westerhout C.M.
      • Welsh R.C.
      Duration of symptoms is the key modulator of the choice of reperfusion for ST-elevation myocardial infarction.
      the precision of this metric in identifying the stage of evolution of STEMI in humans has been less reliable than that seen in experimental models.
      • Armstrong P.W.
      • Fu Y.
      • Westerhout C.M.
      • et al.
      Baseline Q-wave surpasses time from symptom onset as a prognostic marker in ST-segment elevation myocardial infarction patients treated with primary percutaneous coronary intervention.
      • Reimer K.A.
      • Lowe J.E.
      • Rasmussen M.M.
      • Jennings R.B.
      The wavefront phenomenon of ischemic cell death. 1. Myocardial infarct size vs duration of coronary occlusion in dogs.
      This ambiguity is even more pronounced in the female sex and likely relates, at least in part, to the lack of specificity of prodromal symptoms and the atypical clinical presentation in women.
      • Graham M.M.
      • Westerhout C.M.
      • Kaul P.
      • Norris C.M.
      • Armstrong P.W.
      Sex differences in patients seeking medical attention for prodromal symptoms before an acute coronary event.
      • McSweeney J.C.
      • Cody M.
      • O'Sullivan P.
      • Elberson K.
      • Moser D.K.
      • Garvin B.J.
      Women's early warning symptoms of acute myocardial infarction.
      In a prior retrospective study of STEMI patients undergoing primary percutaneous coronary intervention (PCI) within 6 hours of symptom onset, baseline Q waves emerged as a reliable independent prognostic factor and also proved to be superior to time from symptom onset in predicting 90-day clinical outcomes.
      • Armstrong P.W.
      • Fu Y.
      • Westerhout C.M.
      • et al.
      Baseline Q-wave surpasses time from symptom onset as a prognostic marker in ST-segment elevation myocardial infarction patients treated with primary percutaneous coronary intervention.
      • Mercuri M.
      • Natarajan M.K.
      • Velianou J.L.
      ST-elevation myocardial infarction: is there time for Q waves?.
      Interestingly, this electrocardiogram (ECG) metric appeared to be especially advantageous in females.
      • Kaul P.
      • Fu Y.
      • Westerhout C.M.
      • Granger C.B.
      • Armstrong P.W.
      Relative prognostic value of baseline Q wave and time from symptom onset among men and women with ST-elevation myocardial infarction undergoing percutaneous coronary intervention.
      In the current study, using the wider temporal randomization window and longer-term follow-up of the PLATelet inhibition and patient Outcomes (PLATO) trial ECG substudy,
      • Wallentin L.
      • Becker R.C.
      • Budaj A.
      • et al.
      Ticagrelor versus clopidogrel in patients with acute coronary syndromes.
      we prospectively examined the prognostic relationship between time from symptom onset and baseline Q waves in men and women.

      Materials and Methods

      Q waves aligned with the location of the qualifying acute infarct on the baseline ECG were assessed in STEMI patients. We evaluated the associations among these baseline Q waves, time from symptom onset to PCI, and sex on vascular mortality within 1 year. Vascular death was defined as death from vascular causes including cardiovascular deaths, cerebrovascular deaths, and any other death for which there was no clearly documented nonvascular cause.

      Data Collection

      The PLATO trial was a multicenter, randomized and double-blind study that compared the effects of the novel platelet P2Y12 receptor inhibitor ticagrelor with clopidogrel therapy. Specific details of the study design and primary results have been published.
      • Wallentin L.
      • Becker R.C.
      • Budaj A.
      • et al.
      Ticagrelor versus clopidogrel in patients with acute coronary syndromes.
      We included only those patients who had at least 1 mm of ST-segment elevation in the inferior or 2 mm in the anterior leads, in at least 2 contiguous leads, on the qualifying ECG, and who had undergone primary PCI within 12 hours of randomization. Although patients were suitable for inclusion in PLATO for up to 24 hours after symptom onset, given the long temporal distribution tail of patients presenting after 12 hours, they were excluded (Supplementary Figure, available online). We confined our assessment to those patients enrolled within 12 hours in accordance with the usual treatment window of current STEMI guidelines.
      • Antman E.M.
      • Anbe D.T.
      • Armstrong P.W.
      • et al.
      ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction—executive summary.
      • Thygesen K.
      • Alpert J.S.
      • Jaffe A.S.
      • et al.
      Third universal definition of myocardial infarction.
      In the Supplementary Table (available online), the baseline characteristics of both the included and excluded patients are shown.

      Electrocardiogram Analysis

      The ECGs were analyzed by an ECG core laboratory (Canadian VIGOUR Centre, Edmonton, Alberta, Canada) without knowledge of the treatment assignment or outcome and according to methods previously described.
      • Armstrong P.W.
      • Siha H.
      • Fu Y.
      • et al.
      ST-elevation acute coronary syndromes in the Platelet Inhibition and Patient Outcomes (PLATO) trial: insights from the ECG substudy.
      The definition of the Q waves or Q-wave equivalent was based on Selvester QRS screening criteria. A pathologic Q wave was defined as follows: ≥ 30 ms in lead aVF (inferior), ≥ 40 ms in leads I and aVL (lateral), ≥ 40 ms in 2 or more of leads V4, V5, or V6 (apical), or any Q wave ≥ 20 ms or QS complex in leads V2 and V3 (anterior). A Q-wave equivalent was defined as follows: R wave ≥ 40 ms in V1 (posterior) or R wave ≤ 0.1 mV and ≤ 10 ms in V2 (anterior). ST-segment elevation was measured at the J point with magnified calipers to the nearest 0.05 mV. The sum total across all leads except aVR was used to determine either ST-segment elevation sums (ΣST-E) or ST-segment depression sums. The percent resolution of ST-segment elevation sums and ST-segment deviation sums (elevation plus depression; ΣST-D) from baseline to discharge (the median time between the 2 ECGs were 3 days) was dichotomized in accordance with guidelines by the European Society of Cardiology and the American College of Cardiology/American Heart Association as either < 50% or ≥ 50%.

      Biomarker Analysis

      Baseline troponin was assessed centrally using the Advia Centaur TNI-Ultra Immunoassay (Siemens, Malvern, Pennsylvania). A positive result for troponin-I was considered for a level of 0.08 μg or more per liter for the first sample taken. Locally collected biomarkers included creatine kinase-MB, troponin-T, and troponin-I; these markers were reported as a ratio of the upper limit of normal. Peak biomarkers were used to assess myocardial necrosis.

      Statistical Analysis

      Categorical variables were presented as percentages, and differences between groups were tested by the chi-squared test; the Fisher's exact test was applied when the cell count was < 5. Continuous variables were summarized as medians with 25th and 75th percentiles, and differences between groups were tested via Wilcoxon rank-sum test.
      Time from symptom onset to PCI was considered continuously and then dichotomously with a 3-hour cut point (≤ 3 vs > 3) to correspond with our prior work.
      • Armstrong P.W.
      • Fu Y.
      • Westerhout C.M.
      • et al.
      Baseline Q-wave surpasses time from symptom onset as a prognostic marker in ST-segment elevation myocardial infarction patients treated with primary percutaneous coronary intervention.
      • Kaul P.
      • Fu Y.
      • Westerhout C.M.
      • Granger C.B.
      • Armstrong P.W.
      Relative prognostic value of baseline Q wave and time from symptom onset among men and women with ST-elevation myocardial infarction undergoing percutaneous coronary intervention.
      The relation between time from symptom onset to baseline ECG per hour for the first 6 hours and then grouped from 7-12 hours was explored according to sex. The Cochran-Armitage trend test was used to test whether the frequency of Q waves differed across every hour of time from symptom onset to baseline ECG.
      The associations of sex, Q waves, and time to PCI on vascular mortality within 1 year were assessed using Cox proportional hazards regression model. Sex-specific relations between Q waves and time to PCI were also examined. Other factors included in the multivariable model were: age, systolic blood pressure, Killip class, heart rate, and myocardial infarction (MI) location, which corresponds to the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO)-I mortality model.
      • The Global Use of Strategies to Open Occluded Coronary Arteries in Acute Coronary Syndromes (GUSTO IIb) Angioplasty Substudy Investigators
      A clinical trial comparing primary coronary angioplasty with tissue plasminogen activator for acute myocardial infarction.
      Unadjusted and adjusted hazard ratios (HR) with 95% confidence intervals (CI) are reported. The following interactions were tested: 3-way interaction of sex, baseline Q waves, and time to PCI (continuous); 2-way interaction of sex and Q waves, and sex and time to PCI (3-hour cut point). Restricted cubic spline functions with 5 knots were used to examine the linearity assumption when time to PCI was considered continuously.
      All statistical tests were 2-sided, and were considered statistically significant when P < .05. Analyses were performed using SAS (version 9.3; SAS Institute Inc, Cary, NC).

      Results

      Of the 5417 patients who had STEMI and underwent PCI (Figure 1), 2579 were excluded because of prior MI or Q waves outside the acute ST-segment elevation territory (n = 486), or Q waves were not determined because of poor quality ECG (n = 23), or left bundle branch block (n = 204). In addition, patients who had PCI more than 12 hours after randomization (n = 1019) or a noninferior STEMI with < 2 mm ST-segment elevation in 2 contiguous leads (n = 847) were also excluded to correspond with the universal definition of MI
      • Antman E.M.
      • Anbe D.T.
      • Armstrong P.W.
      • et al.
      ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction—executive summary.
      • Thygesen K.
      • Alpert J.S.
      • Jaffe A.S.
      • et al.
      Third universal definition of myocardial infarction.
      and to allow us direct comparison with earlier work in the Assessment of PEXelizumab in Acute Myocardial Infarction (APEX-AMI) trial.
      • Armstrong P.W.
      • Fu Y.
      • Westerhout C.M.
      • et al.
      Baseline Q-wave surpasses time from symptom onset as a prognostic marker in ST-segment elevation myocardial infarction patients treated with primary percutaneous coronary intervention.
      • Kaul P.
      • Fu Y.
      • Westerhout C.M.
      • Granger C.B.
      • Armstrong P.W.
      Relative prognostic value of baseline Q wave and time from symptom onset among men and women with ST-elevation myocardial infarction undergoing percutaneous coronary intervention.
      Figure thumbnail gr1
      Figure 1Patient cohort. ECG = electrocardiogram; LBBB = left bundle branch block; MI = myocardial infarction; PCI = percutaneous coronary intervention; STEMI = ST-segment elevation myocardial infarction.
      The baseline patient characteristics of the 2838 patients in the current study are presented in Table 1 according to sex, the presence of Q waves (left panel), and time from symptom onset to PCI (right panel). Women were older (median 63 vs 57 years) and were more likely to have diabetes (24.1% vs 15.5%), hypertension (69.2% vs 50.9%), and a Killip class > I (8.6% vs 5.9%) as compared with men. When further categorized, those with baseline Q waves had more frequent high-risk baseline characteristics, presented later after symptom onset and similarly, had a longer time to PCI. Whereas there was a relatively balanced distribution of men and women with Q waves, a greater proportion of women had a delay of > 3 hours from symptom onset to PCI (76.4 vs 67.3% P < .001).
      Table 1Baseline Patient Characteristics in Men and Women According to Q-wave Status and Time From Symptom Onset to Percutaneous Coronary Intervention
      MenWomenMenWomen
      No Q WavesQ WavesNo Q WavesQ WavesSymptom Onset to PCI ≤ 3 hSymptom Onset to PCI > 3 hSymptom Onset to PCI ≤ 3 hSymptom Onset to PCI > 3 h
      n113510284052707081455159516
      Age, y55 (50, 63)59 (52, 66)62 (55, 71)65 (57, 73)56 (50, 64)58 (51, 66)60 (55, 69)64 (56, 72)
      Diabetes, n (%)162 (14.3)173 (16.8)91 (22.5)72 (26.7)104 (14.7)231 (15.9)30 (18.9)133 (25.8)
      Hypertension, n (%)549 (48.4)553 (53.8)277 (68.4)190 (70.4)331 (46.8)771 (53.0)99 (62.3)368 (71.3)
      Heart rate, bpm74 (65, 84)78 (68, 90)74 (64, 85)78 (70, 90)75 (65, 85)76 (67, 88)76 (66, 85)75 (67, 88)
      Systolic blood pressure, mm Hg132 (120, 150)135 (120, 150)130 (120, 150)138 (120, 152)132 (120, 150)134 (120, 150)130 (110, 150)133 (120, 150)
      Killip class > I, n (%)51 (4.5)76 (7.4)29 (7.2)29 (10.7)38 (5.4)89 (6.1)12 (7.5)46 (8.9)
      Creatinine clearance, mL/min91.5 (76.1, 107.1)86.3 (69.9, 105.6)82.2 (62.7, 102.7)75.2 (57.6, 95.7)90.7 (74.9, 106.3)88.4 (72.4, 106.7)82.5 (63.9, 100.0)78.6 (60.4, 99.3)
      Time from symptom onset to baseline ECG, h1.9 (1.1, 3.3)2.5 (1.5, 4.2)2.5 (1.4, 4.0)3.0 (1.7, 4.7)1.1 (0.7, 1.6)3.1 (2.0, 4.5)1.1 (0.7, 1.8)3.4 (2.2, 4.9)
      Time from symptom onset to PCI, h3.5 (2.5, 5.1)4.2 (2.9, 6.1)4.3 (3.1, 6.3)4.8 (3.2, 6.5)2.3 (1.9, 2.7)4.8 (3.8, 6.7)2.3 (2.0, 2.7)5.3 (4.0, 6.9)
      Continuous variables presented as median (25th, 75th percentiles).
      ECG = electrocardiogram; PCI = percutaneous coronary intervention.
      The baseline characteristics of those included vs excluded in our study are shown in the Appendix (Supplementary Table, available online). In general they were similar, although there were a numerically higher number of patients with diabetes and Killip class > I in excluded patients. As expected, the mean time from symptom onset to PCI was longer, and percentage of noninferior MI was also higher, reflecting the exclusion of patients presenting more than 12 hours and those noninferior STEMI patients with < 2 mm ST-segment elevation.
      In Table 2, detailed baseline ECG and biomarker data are shown according to a similar format. Although there were fewer inferior MI patients presenting with Q waves, the MI location was balanced according to time to PCI. Patients with Q waves had more ST-segment elevation and deviation and were less likely to exhibit ST-segment resolution after PCI. Both men and women with Q waves had longer times to PCI and had greater biomarker evidence of myocardial necrosis.
      Table 2ECG and Cardiac Biomarker Data According to Baseline Q and Time From the Onset of Symptoms to PCI
      MenWomenMenWomen
      No Q WavesQ WavesNo Q WavesQ WavesSymptom Onset to PCI ≤ 3 hSymptom Onset to PCI > 3 hSymptom Onset to PCI ≤ 3 hSymptom Onset to PCI > 3 h
      n113510284052707081455159516
      Inferior MI, n(%)775 (68.3)420 (40.9)289 (71.4)100 (37.0)393 (55.5)802 (55.1)83 (52.2)306 (59.3)
      Baseline ΣST-E, mm7.0 (4.5, 11.5)10.5 (6.5, 16.0)7.0 (4.5, 11.0)9.0 (6.5, 14.5)9.0 (6.0, 14.3)8.5 (5.0, 13.0)8.5 (5.5, 12.0)7.5 (4.5, 12.0)
      Baseline ΣST-D, mm12.5 (8.0, 18.5)14.5 (10.0, 21.0)12.0 (9.0, 18.0)13.0 (9.5, 18.5)14.0 (9.5, 21.0)13.0 (9.0, 19.5)13.0 (9.0, 18.5)12.5 (9.0, 18.0)
      ΣST-E resolution ≥ 50%, n (%)779 (86.0)595 (74.4)286 (88.5)154 (74.8)481 (85.1)893 (78.3)109 (91.6)331 (80.7)
      ΣST-D resolution ≥ 50%, n (%)802 (88.5)614 (76.8)276 (85.5)154 (74.8)491 (86.9)925 (81.1)105 (88.2)325 (79.3)
      Central troponin I ≥ 0.08 ng/mL at study entry, n (%)971 (86.1)954 (93.3)356 (88.6)248 (92.9)581 (82.5)1344 (92.9)133 (84.7)471 (92.0)
      Peak local CK-MB, ratio of the ULN [valid n]5.7 (2.1, 13.4) [790]9.1 (2.9, 21.1) [724]6.6 (2.2, 15.6) [282]7.7 (2.7, 22.6) [201]6.7 (2.1, 16.6) [456]7.2 (2.5, 16.9) [1058]6.6 (1.7, 16.6) [110]7.2 (2.4, 17.8) [373]
      Peak local troponin I, ratio of the ULN [valid n]62.1 (5.6, 249.9) [617]134.4 (18.6, 460.0) [531]57.0 (6.0, 203.8) [218]99.3 (13.0, 368.2) [127]78.6 (6.2, 308.7) [418]99.1 (11.9, 380.0) [730]56.7 (4.2, 225.1) [96]73.8 (9.8, 261.2) [249]
      Peak local troponin T, ratio of the ULN [valid n]20.0 (3.0, 80.6) [353]44.2 (9.3, 132.2) [306]17.7 (2.3, 59.3) [127]33.0 (8.1, 85.0) [93]37.0 (6.4, 114.3) [203]26.3 (4.2, 88.7) [456]17.5 (2.0, 42.0) [52]25.7 (4.3, 77.3) [168]
      Continuous variables presented as median (25th, 75th percentiles).
      CK = creatine kinase; MI = myocardial infarction; ΣST-D = sum ST-segment deviation; ΣST-E = sum ST-segment elevation; ULN = upper limit of normal.
      Figure 2A (upper panel) shows the distribution of men and women for the time per hour from symptom onset to baseline ECG. Given the modest sample size, those patients presenting 7-12 hours after symptom onset were grouped together to facilitate this comparison (Supplementary Figure, available online). There was a clustering of the peak time for presentation for men within the first 2-3 hours, whereas the distribution in women tended to be flat across the time window. When this temporal analysis was examined according to the presence of Q waves on baseline ECG (Figure 2B), a progressive increase over time was evident in the frequency of Q waves in men. However, this trend tended to be attenuated in women (P = .057 for difference in sex-specific slopes).
      Figure thumbnail gr2
      Figure 2(A) Time from symptom onset to electrocardiogram (ECG; per hour) in men and women. (B) Baseline Q waves according to time from symptom onset to ECG for men and women.
      The associations of baseline Q waves and time from symptom onset to PCI with vascular death within 1 year in men and women are shown in Figure 3. The presence of Q waves on baseline ECG was associated with poor outcomes in both men and women. After multivariable adjustment, the presence of Q waves in the baseline ECG was associated with twice the risk of vascular death in men, and a similar trend existed for women (P[interaction] = .509). Although there was no significant interaction for sex, time from symptom onset to PCI > 3 hours tended to be associated with an increase in vascular deaths in men (HR 1.62; 95% CI, 0.87-3.01), but less so in women (P[interaction] = .738).
      Figure thumbnail gr3
      Figure 3Associations of baseline Q waves and time to PCI on vascular mortality within 1 year in men and women. P(interaction, sex and baseline Q waves) = .509; P(interaction, sex and time to PCI) = .738. A = adjusted; CI = confidence interval; HR = hazard ratio; PCI = percutaneous coronary intervention; pts = patients; U = unadjusted. *Adjusted for age, systolic blood pressure, heart rate, Killip Class, inferior myocardial infarction.
      The association between baseline Q waves and sex on 1-year vascular death–according to time from symptom onset to PCI as a continuous variable–is shown in Figure 4. Although there was no significant 3-way interaction for sex, baseline Q waves, and time to PCI (P = .182), a different pattern was evident between men and women. As time to PCI increased, women with baseline Q waves tended to have higher risk of 1-year vascular death than men.
      Figure thumbnail gr4
      Figure 4Associations of baseline Q waves and sex on vascular mortality within 1 year according to time to PCI as a continuous variable; P(interaction, sex, and baseline Q waves and time to PCI) = .182. For women with time = 8 hours, 95% CI, 0.85-14.8; with time = 9 hours, 95% CI, 0.77-24.2; with time = 10 hours, 95% CI, 0.69-40.0; with time = 11 hours, 95% CI, 0.61-66.8; with time = 12 hours, 95% CI, 0.54 -112.3. CI = confidence interval; HR = hazard ratio; PCI = percutaneous coronary intervention. *Adjusted for age, systolic blood pressure, heart rate, Killip Class, inferior myocardial infarction.

      Discussion

      In this well-characterized population of STEMI patients, women presented later after symptom onset and more often exhibited Q waves in comparison with men. Patients with Q waves more often had noninferior MI, greater ST-segment elevation and deviation at baseline, and were less likely to have ST-segment resolution. They also had more evidence of myocardial necrosis as measured by biomarkers.
      There was a twofold excess in 1-year vascular death among men with baseline Q waves, and also a trend for them to have greater mortality when they presented at a later time from symptom onset to PCI (> 3 hours). A similar relationship between the presence of a baseline Q wave and outcome existed in women, which reverted to a trend after adjustment.
      As time from symptom onset to the baseline ECG unfolded, there was a steep increase in the occurrence of Q waves, which was attenuated in women. Moreover, when time from symptom onset to PCI was examined as a continuous variable, women with baseline Q waves tended to have a higher 1-year vascular mortality than men.
      Although our study is derived from a smaller number of STEMI patients than in our prior retrospective APEX-AMI study, it has the advantage of evaluating a broader temporal therapeutic window of 12 vs 6 hours after symptom onset and providing longer-term mortality data, that is, 12 vs 3 months. Because we excluded patients who had < 2 mm ST-segment elevation in noninferior leads and those who presented more than 12 hours after symptom onset, we cannot be assured that our observations apply to that population. The current prospective results are aligned well with the previous ones from APEX-AMI because they highlight both the prognostic value of baseline Q waves in both sexes as well as their particular value among women where time from symptom onset is a less reliable guide to prognosis. The symptomatic profile of women presenting with STEMI–as well as the response of the health care system–are known to contribute to delays in receiving reperfusion therapy, and underscore the need to use additional metrics such as baseline Q waves at the time of presentation. Consideration of including this signal in STEMI guidelines and in selecting patients for future clinical trials seems warranted.

      Appendix

      Supplementary TableBaseline Patient Characteristics According to Patients Included vs Excluded
      Patients in This Study n = 2838Patients Excluded From This Study n = 2579P Value
      Age, y58.0 (52.0, 67.0)60.0 (52.0, 69.0)<.001
      Diabetes, n (%)498 (17.5)555 (21.5)<.001
      Hypertension, n (%)1569 (55.3)1584 (61.4)<.001
      Heart rate, bpm75.0 (66.0, 87.0)75.0 (66.0, 87.0).305
      Systolic blood pressure, mm Hg132.0 (120.0, 150.0)130.0 (120.0, 150.0).656
      Killip class > I, n (%)185 (6.5)221 (8.6).004
      Creatinine clearance, mL/min87.3 (70.3, 104.9)85.2 (67.3, 104.0).012
      Time from symptom onset to baseline ECG, hours2.3 (1.3, 3.9)3.2 (1.4, 7.9)<.001
      Time from symptom onset to PCI, hours3.9 (2.8, 5.8)9.0 (4.2, 19.6)<.001
      Inferior MI, n (%)1584 (55.8)709 (31.5)<.001
      Continuous variables presented as median (25th, 75th percentiles).
      ECG = electrocardiogram; MI = myocardial infarction; PCI = percutaneous coronary intervention.
      Figure thumbnail fx1
      Supplementary FigureTime from symptom onset to percutaneous coronary intervention (PCI) per hour on patients with time available in the PLATelet inhibition and patient Outcomes trial (PLATO; n = 4341, median 4.7 [3.1-8.3]).

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