Scant data are available on the relation between ST-segment elevation (STE) resolution and 30-day mortality in patients with STE acute myocardial infarction treated with percutaneous coronary intervention in contemporary, real world, clinical practice. Furthermore, whether the prognostic value of STE resolution is influenced by the patient clinical risk profile or postprocedural Thrombolysis In Myocardial Infarction (TIMI) flow has never been investigated. Lombardima was an observational registry implemented in Lombardy, a Northern Italian region. The clinical characteristics, electorcardiographic parameters, and procedural data were prospectively entered into a Web-based database. In the present study, we enrolled 3,403 patients. STE resolution occurred in 2,452 patients (group 1) and did not in 951 patients (group 2). The mortality rate was 2.4% in group 1 and 11.3% in group 2 (p <0.001). After stratifying patients according to their TIMI risk index, we observed that STE resolution was an independent predictor of 30-day mortality across all spectrum of clinical risk. Furthermore, in patients with TIMI 3 flow, STE resolution remained an independent predictor of 30-day mortality (p <0.0001). In conclusion, STE resolution was a strong and independent predictor of 30-day mortality in patients with STE acute myocardial infarction undergoing percutaneous coronary intervention across all spectrum of clinical risk.
The relation between ST-segment elevation (STE) resolution and prognosis in patients with STE acute myocardial infarction (STEMI) treated with percutaneous coronary intervention (PCI) has been studied in either randomized trials, which might not be representative of real world clinical practice, or in registry studies that either reported the results for a limited number of patients or were performed almost 10 years earlier. Moreover, no study has ever assessed whether a relation exists between STE resolution and the clinical risk profile of patients with respect to their short-term prognosis. Furthermore, limited data are available on the relation between post-treatment Thrombolysis In Myocardial Infarction (TIMI) 3 flow and STE resolution with respect to 30-day mortality and no real-world data are available on whether STE resolution maintains its prognostic value in those patients with postprocedural TIMI 3 flow. Thus, we performed an observational study to establish the association between STE resolution and 30-day mortality in a large and unselected cohort of patients enrolled in a real-world registry with no exclusion criteria. Moreover, we evaluated the prognostic value of STE resolution in different strata of the population enrolled, according to the patient clinical risk profile and in patients with postprocedural TIMI 3 flow. Finally, we determined the independent predictors of STE resolution.
Methods
The Lombardima Registry was implemented in 2005 to monitor the outcomes of patients undergoing PCI in Lombardy, a Northern Italian region with a population of nearly 9.5 million inhabitants, 15% of the Italian population. The network included 67% of the PCI centers in the region. All consecutive patients with characteristic symptoms of acute STEMI presenting at the first medical contact within 12 hours of symptom onset with ≥1-mm STE in ≤2 contiguous leads or ≥2 mm in leads V 1 to V 4 or left bundle branch block and who underwent PCI were included in the Registry. The clinical characteristics, risk markers, electrocardiographic parameters, intervals, and angiographic and procedural data were prospectively entered into a Web-based database with a prespecified data set. The Registry enrolled patients treated with rescue PCI, facilitated PCI, and primary PCI from January 2005 to December 2006. For the purposes of the present study, we included only patients treated with primary PCI or facilitated PCI. The use of interventional strategies and antithrombotic drugs were at the operator’s discretion. The 30-day follow-up was performed by telephone interview. The use of the Registry was approved by the local ethics committees, and patients provided informed consent to participate in the present study.
The primary objective of the present study was to evaluate the association between STE resolution and the risk of 30-day mortality. STE resolution was measured in all patients at each center according to a prespecified protocol. The absolute level of STE was measured manually to the nearest 0.01 mV, 20 ms after the end of the QRS interval, using the TP segment as the isoelectric baseline. The sum of STE on the postprocedure electrocardiogram (ECG) was determined 60 minutes after PCI. All investigators reading the ECGs were unaware of the patient outcomes. Patients were considered to have STE resolution if they had a percentage of reduction >50% of the summed score of STE on the postprocedure ECG with respect to the preprocedure ECG.
Primary PCI was defined as PCI not preceded by the administration of either glycoprotein IIb–IIIa inhibitors or thrombolytic therapy. Facilitated PCI was defined as intended PCI preceded by the administration of thrombolytic therapy and/or glycoprotein IIb–IIIa inhibitors. Cardiogenic shock (Killip class IV) was defined as persistent systolic blood pressure <90 mm Hg, unresponsiveness to intravenous fluid administration, or as the need for vasopressor agents to maintain a systolic blood pressure of ≥90 mm Hg. The total ischemic time was defined as the interval in minutes between the onset of symptoms and the first balloon dilation. The TIMI risk index was calculated using the equation: [heartrate×(age/10)2]/systolicbloodpressure.6
[ heart rate × ( age / 10 ) 2 ] / systolic blood pressure . 6
Data are presented as the mean ± SD or the median and range, as appropriate. Continuous data between groups were compared using the unpaired Student t test or Mann-Whitney rank sum test, as appropriate. Categorical variables were compared using chi-square statistics or Fisher’s exact test, as appropriate. Independent predictors of STE resolution were analyzed by multivariate logistic regression analysis. The following variables were included in the model: age, gender, renal dysfunction, Killip class (III–IV vs I–II), number of electrocardiographic leads with STE (>5 vs ≤5), glycoprotein IIb–IIIa inhibitors, stent length (>25 vs ≤25 mm), preprocedural TIMI flow (3 vs 0, 1, or 2), postprocedural TIMI flow, anterior location, total ischemic time, and diabetes. Independent predictors of 30-day mortality were analyzed using multivariate logistic regression analysis. The following variables were included in the model: STE resolution, age, gender, renal dysfunction, Killip class, number of electrocardiographic leads with STE, glycoprotein IIb–IIIa inhibitor use, postprocedural TIMI flow, total ischemic time, and diabetes. Model discrimination was assessed with the c statistic and model calibration with the Hosmer-Lemeshow statistic. Both the c-index with confidence intervals and calibration were calculated with and without STE resolution. Moreover, to assess the predictive value of STE resolution, the integrated discrimination improvement was calculated. Finally, we also evaluated the ability of STE resolution to reclassify the risk of mortality, as previously described. Patient risk of 30-day mortality was initially estimated using a multivariate model that did not include STE resolution. Patients were classified as low, intermediate, or high risk according to their risk of mortality, as determined by tertiles of the TIMI risk index. Patients were then reclassified using a second multivariate model that included STE resolution. We assessed the number of patients reclassified and also calculated the net reclassification improvement. Statistical analyses were performed using Statistical Package for Social Sciences, version 12.0, for Windows (SPSS, Chicago, Illinois) and Stata/SE, version 9.2, for Windows (StataCorp, Houston, Texas). p Values <0.05 were considered statistically significant.
Results
The Lombardima Registry recruited 3,901 patients. After excluding the patients for whom an ECG was not available (105 patients), whose ECG showed left bundle branch block (178 patients), and patients treated with rescue PCI (215 patients), 3,403 patients remained available for the analyses. The patient characteristics stratified by STE resolution are listed in Tables 1 and 2 . Of the 3,403 patients, 2452 (72%) presented with STE resolution (group 1) and 951 (22%) did not (group 2). The independent predictors of STE resolution ( Table 3 ) were age, Killip class, glycoprotein IIb–IIIa inhibitor use, stent length, preprocedural TIMI 3 flow, postprocedural TIMI 3 flow, anterior location, total ischemic time, and diabetes. Renal dysfunction was of borderline significance (p = 0.05). The Hosmer-Lemeshow statistic of the logistic model was 0.30, and the c statistic was 0.67.
| Variable | Availability | STE Resolution | p Value | |
|---|---|---|---|---|
| Yes (n = 2,452) | No (n = 951) | |||
| Age (years) | 3,403 (100%) | 62 (53–71) | 65 (56–75) | <0.001 |
| Men | 3,403 (100%) | 1,926 (79%) | 693 (73%) | <0.001 |
| Systemic hypertension | 3,403 (100%) | 1,104 (45%) | 496 (52%) | <0.001 |
| Diabetes mellitus | 3,403 (100%) | 356 (15%) | 213 (22%) | <0.001 |
| Hypercholesterolemia ⁎ | 3,403 (100%) | 970 (40%) | 354 (37%) | 0.22 |
| Smoker | 3,403 (100%) | 1,171 (48%) | 392 (41%) | <0.001 |
| Family history of cardiovascular disease | 3,403 (100%) | 775 (32%) | 247 (26%) | 0.001 |
| Renal dysfunction | 3,403 (100%) | 41 (2%) | 30 (3%) | 0.01 |
| Previous myocardial infarction | 3,403 (100%) | 274 (11%) | 106 (11%) | 0.97 |
| Previous coronary angioplasty | 3,403 (100%) | 226 (9%) | 82 (9%) | 0.63 |
| Previous coronary artery bypass grafting | 3,403 (100%) | 54 (2%) | 31 (3%) | 0.10 |
| Left ventricular ejection fraction (%) | 2,809 (82%) | <0.001 | ||
| >50% | 1,114 (55%) | 271 (35%) | ||
| 41–50% | 686 (34%) | 319 (41%) | ||
| 30–40% | 190 (9%) | 142 (18%) | ||
| <30% | 45 (2%) | 42 (6%) | ||
| Killip class | 3,380 (99%) | <0.001 | ||
| I | 2,014 (82%) | 652 (69%) | ||
| II | 284 (12%) | 164 (17%) | ||
| III | 69 (3%) | 52 (6%) | ||
| IV | 70 (3%) | 75 (8%) | ||
| No. of leads with ST elevation | 3,342 (98%) | <0.001 | ||
| <3 | 701 (29%) | 172 (19%) | ||
| 3–5 | 1,186 (49%) | 490 (53%) | ||
| >5 | 530 (22%) | 263 (28%) | ||
| Total ischemic time † | 2,633 (77%) | 173 (120–255) | 190 (134–283) | 0.02 |
| Thrombolysis In Myocardial Infarction risk index | 3,094 (96%) | 21 (15–29) | 25 (17–36) | <0.001 |
| Infarct location | 3,391 (99%) | <0.001 | ||
| Anterior | 1,037 (42%) | 559 (59%) | ||
| Nonanterior | 1,408 (58%) | 397 (41%) | ||
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