Results
Baseline Characteristics of 559 Study Patients
Table 1 shows the baseline relevant variables of 559 study patients. The age, male gender, and risk factors for coronary artery disease including the prevalences of diabetes mellitus, hypertension, current smoking, and serum level of low-density lipoprotein did not differ between conventional DTB group and shortened DTB group. In additional, the 12-lead complete electrocardiogram showed that the prevalences of infarct locations of anterior, inferior, and lateral walls did not differ between the two groups. However, the serum level of the total cholesterol was significantly higher in the conventional DTB group than that in the shortened DTB group.
Laboratory examination showed that serum creatinine level, WBC count, fasting blood sugar, troponin-I, and creatine kinase creatine kinase MB upon presentation did not differ between the two groups of patients. However, the peak level of creatine phosphokinase (CPK) was significantly higher in the conventional DTB group than that in the shortened DTB group. This finding implies that the strategy of shortened DTB time during primary PCI contribute to the benefit of reducing MI size.
The Clinical Characteristics, Echocardiography Findings, Results of Angiography, and 30-day Clinical Outcomes of the Study Patients
The prevalences of Killip scores, the prevalence of cardiogenic shock, and the requirement for IABP or ECMO support were similar between the conventional DTB group and the shortened DTB group ( Table 2 ). Besides, the mean NYHfA functional classification of CHF and the prevalence of advanced CHF (defined as ≥ CHF score 3) did not differ between the two groups.
Although the duration from chest pain onset to arrival at emergency department did not differ between the conventional DTB group and the shortened DTB group, the door-to-puncture time and puncture-to-first balloon inflation time were significantly reduced in the shortened DTB group than those in the conventional DTB group. Further analysis also demonstrated significantly higher prevalence of DTB time less than 60 minutes in the shortened than that in the conventional DTB group.
Coronary angiography revealed no notable difference in the prevalences of multivessel disease and significant left main obstructive disease between the two groups. Furthermore, the prevalences of initial TIMI flow greater than or equal to 2 or less than or equal to 1, final TIMI-3 flow (i.e., successful reperfusion), and less than or equal to TIMI-2 flow (i.e., unsuccessful reperfusion) also did not differ between the two groups.
The prevalences of pre-PCI stenosis (%) and post-PCI residual stenosis (%) were also similar among the patients. In addition, pre- or post-PCI minimal lumen diameter and pre-PCI or post-PCI reference lumen diameter also did not differ between the two groups. The relatively lower prevalence of patients receiving drug-eluting stent implantation was due to either economic problem or a vessel diameter greater than 4.0 mm. The prevalence of bare metal stenting was significantly lower, whereas the prevalence of drug-eluting stenting was significantly higher in shortened DTB group than in conventional DTB group. Furthermore, the utilizing rate of thrombectomy or PercuSurge distal protection was significantly higher in shortened DTB group than in conventional DTB group. On the other hand, the prevalences of acute or subacute stent thrombosis and the final TIMI-3 flow in bare metal stenting or in drug-eluting stenting were similar between the two groups. Similarly, there was also no significant difference in LVEF, prevalence of 30-day mortality, and 30-day combined endpoint between the two groups.
Impact of Shortening DTB Time Less Than 45 Minutes Could Offer Additional Benefit to the Patients—Analysis of 559 Patients
To elucidate whether shortened DTB time would provide additional benefits for the 559 STEMI patients, subgroup analysis was performed ( Table 3 ): 1) DTB time less than or equal to 30 versus greater than 30 minutes; 2) DTB time less than or equal to 45 versus greater than 45 minutes; and 3) DTB time less than or equal to 60 versus greater than 60 minutes. Surprisingly, the results demonstrated that the prevalences of final TIMI-3 flow, advanced CHF, 30-day mortality, and 30-day combined endpoint did not differ among patients from the three time intervals. The findings may imply that shortened DTB time cannot provide significantly greater benefit than that of conventional DTB time for STEMI patients undergoing primary PCI.
Impact of Different Time Intervals From Chest Pain Onset to Reperfusion on Outcomes in STEMI Patients Undergoing Primary PCI—Analysis of 559 Patients
To determine whether the different time intervals from chest pain onset to first balloon inflation is critical for reducing the level of CPK cardiac isoenzyme (i.e., an indirect indicator of infarct size), and improving LV function and 30-day outcomes, subgroup analysis was performed ( Table 4 ): 1) chest pain onset to reperfusion time less than or equal to 240 versus greater than 240 minutes; 2) chest pain onset to reperfusion time less than or equal to 180 versus greater than 180 minutes; and 3) chest pain onset to reperfusion time less than or equal to 120 versus greater than 120 minutes. The results demonstrated that the prevalences of 30-day mortality and 30-day combined endpoint showed only a tendency without statistical significance on comparison of the three time intervals (all p values > 0.05). However, comparing chest pain onset to reperfusion time of less than or equal to 240 versus greater than 240 minutes and less than or equal to 180 versus greater than 180 minutes demonstrated that the CPK level was significantly lower in the two earlier time intervals than that in the two latter time intervals. Besides, these two short time intervals from chest pain onset to reperfusion also showed similar trend compared with that of LV functional preservation. On the other hand, when the time from chest pain onset to reperfusion was shortened to less than or equal to 120 minutes, the LVEF was found to be significantly increased compared with the time of chest pain onset to reperfusion greater than 120 minutes. However, the CKP level showed no significant difference between patients from these two time intervals.
Univariate Analysis and Multiple Stepwise Logistic Regression Analysis of the Predictors for 30-day Mortality
The univariate analysis demonstrated that advanced CHF, prevalence of unsuccessful reperfusion, and age were the most powerful predictors of 30-day mortality ( Table 5 and Table 6 ). Conversely, LVEF was significantly predictive of freedom from 30-day mortality.
Multiple stepwise logistic regression analysis showed that advanced CHF and age were the strongest independent predictors of 30-day mortality. Furthermore, unsuccessful reperfusion was significantly and independently associated with 30-day mortality. Conversely, increased LVEF was significantly and independently predictive of freedom from 30-day mortality.