| Background: Direct PCI (percutaneous coronary intervention) as an effective therapeutic method of STEMI (ST-segment elevation myocardial infarction) has been clarified. A large number of researches show that the reperfusion time is a critical factor for therapeutic effect of direct PCI, but whether delayed or optional PCI is more effective than conservative ways remains controversial. Meanwhile, further studies are still required on relationships between the reperfusion time and the postoperative cardiac function, as well as the mortality rate. Most researchers consider that QT dispersion (QTd) reflects the local variations of ventricular repolarization. Some studies indicate that QTd correlates with left ventricular mass, cardiac function, and vicious arrhythmia. PCI shortenes QTd despite of several oppsite results. Controversial remains on QTd and its clinical value, on the other hand, alterrations other ECG time interval indice after acute myocardial infarction (AMI), such as QRS width, QT et al. have not been reported. Currently, sinus heart rate turbulence (HRT) had been defined as a reliable factor which predicts high risks of sudden death after myocardial infarction. More and more studies have shown that TS is a critical risk factor after AMI. LOWNS, as a parameter of remature ventricular contractions classification, can not fully reflect the risk of premature ventricular contractions, while the width, amplitude, notch of premature ventricular can reflect the risk at some extent. How to combine these possible risk factors to conclude the prognosis of AMI expects more further studies.Objective: To investigate effects of PCI operation on ECG time interval indicators, heart rate turbulence, long-term prognosis and their clinical significance in patients with STEMI.Methods: 128 hospitalized patients in Heart MED diagnosed as AMI and STEMI according to WHO diagnostic criteria during 2004 -2006 were retrospectively analysed. Male patients were 100 while female were 28 cases, aged 29 - 86 years old, average 66.7±10.3 years old. And they were after direct PCI in our hospital and success for opening infarct-related artery. They were follow-up within 4.2±0.76 years. Clinical procedures were as the folowing:I. PCI time grouping: According to the time from invasion to direct PCI they are divided into 3 groups: Emergency group (<12 hours), Delayed group (12-48 hours), Elective group (48 hours -28 days).①To compare with preoperative TIMI grade, postoperative TIMI grade, and left ventricular ejection fraction (LVEF), left atrial diameter(LAD), left ventricular diameter(LVD) metered at diastasis which were measured by the UCG before prior to discharge with ANOVA.②To compare with long-term mortality rate with chi-square analysis.③To compare with the ECG time interval indicators of preoperative, postoperative 12h and postoperative 1w, and their dynamic changes with the repeated measurement variance analysis.④To compare with the benefit of postoperative TIMI (postoperative TIMI grade-preoperative TIMI grade), postoperative LVEF, LVD, the ECG time interval indicators of postoperative 12h and postoperative 1w with Pearson's bivarition correlation analysis. II. Infarction locum grouping: According to the infarction locum they wrer divided to two groups: anterior group (containing anterior-septal / anterior / extensive-anterior STEMI), non-anterior group (containing none of anterior-septal / anterior / extensive-anterior STEMI). ECG time interval indicators of preoperative, postoperative 12h and postoperative 1w were compared between 2 groups. III. Arrhythmia grouping: According to the occurrence of arrhythmia in hospital (post-PCI 4 hours after) ther were divided into: malignant ventricular arrhythmia group, potential malignant arrhythmia group, without arrhythmia group. ECG time interval indicators of before and 12h, 1w after the PCI were compared between 3 groups.IV. Turnover grouping: They were divided into death group and survival group by the follow-up results, who had ventricular arrhythmias (67cases) during their hospitalization. Premature ventricular width and notches, TO, TS were compared. A stepwise Logistic regression analysis was to explore prognosis and various risk factors.Results:I. A study of significance of difference test were done, which among three PCI time groups for gender, age, smoking index, cardio-cerebral vascular diseases positive family history, history of hypertension, diabetes history, history of cerebrovascular disease, hyperlipidemia and other risk factors, infarct location, and lesion artery numbers. Results suggested that these indicators were all comparable between 3 PCI methods groups (P> 0.05).II. By using the ANOVA to compare with preoperative TIMI among different PCI time, result in statistically significant differences. Preoperative TIMI in the emergency group, the delay group and elective group were 0.43±0.79 VS. 0.55±0.96 VS. 1.44±1.19, P <0.01; There were no significant difference in postoperative TIMI (3.00±0.00 VS 2.88±0.52 VS 2.87±0.52, P> 0.05), left atrial diameter (3.44±0.28 VS 3.53±0.58 VS 3.43±0.39, P> 0.05), left ventricular diameter (5.05±0.41 VS 5.20±0.42 VS 5.18±0.51, P> 0.05). Postoperative LVEF have significant difference (54.29±11.11 VS 45.18±10.53 VS 47.41±12.98, P <0.01). the long-term mortality rate of emergency group was lower than the rest, but the difference was not statistically significant in chi-square test(12.24%, 22.50%, 23.08%, chi-square value of 2.21, P> 0.05).III. Repeated designed measures variance analysis showed that:①The QRS width had no significant changes before and after PCI among three PCI time groups (P> 0.05);②QT, QTc, QTd, QTcd of postoperative 12h were diminution than preoperative one, and the difference was statistically significant (P <0.01) in all three PCI time groups.③QT tendency were comparable in three PCI time groups (P> 0.05); QTc descendent trendency in elective group was delayed than that in emergency group and delayed group (P <0.05);④QTd, QTcd of preoperative in elective group were lower than the other two groups (P <0.05); QTd, QTcd trendency had a significance of difference among three PCI Time Groups(P <0.05), elective group postoperative QTd, QTcd had lower descend than the other two groups.IV. Pearson's bivarition correlation analysis showed that:①QRS width, QTd, QTcd of postoperative 12h and postoperative 1w were negatively correlated with postoperative LVEF (the results of postoperative 12h and postoperative 1w were same. QRS width: r =- 0.249, P <0.01; QTd: r = -0.418, P <0.01, QTcd: r =- 0.445, P <0.01);②QTd, QTcd of postoperative 12h and postoperative 1w were significantly positive correlated with left ventricular diameter (the results of postoperative 12h and postoperative 1w were same. QTd: r = 0.231, P <0.01; QTcd: r = 0.0.236, P <0.01). V. The repeated measures design analysis of variance showed that: QTd, QTcd of preoperative, postoperative 12h and postoperative 1w in anterior group were significantly higher than non-anterior group(P <0.01); QRS width , QT, QTc at different time points in both two groups were no significant difference (P> 0.05). VI. QRS width of postoperative 1w in malignant ventricular arrhythmia group were significantly different compared with the rest two groups (87.9±8.8 VS 93.3±14.7 VS 100.0±11.5, P <0.01); QTd, QTcd of postoperative 1w in three arrhythmia groups had significant differences (QTd: 41.6±9.0 VS 59.8±13.0 VS 68.0±12.1, P <0.01; QTcd: 44.8±9.0 VS 63.4±13.0 VS 72.9±12.2, P <0.01).VII. There was a significant difference in premature ventricular width(131.8±12.8 VS 148.8±23.4, P <0.01), notches(2.25±1.01 VS 3.55±1.56, P <0.01) and TS(3.94±8.45 VS 1.65±7.86, P <0.01) between survival group and death group. And there was no significant difference in TO between two groups (0.17±0.19 VS 0.23±0.24, P> 0.05).VIII. Logistic regression analysis showed that premature ventricular notchs and TS were correlated with long-term decease (OR = 4.641, [1.376 15.653], P <0.05; OR = 0.111, [0.022 0.552], P <0.01).Conclusions:I. The time from invasion to PCI has a significant influence on postoperative cardiac function of AMI. It would rescue the dying myocardium, improve cardiac function, even may reduce mortality,that PCI were carried out, and infarct-related artery were opened as soon as possible after AMI.II. QT, QTc, QTd, QTcd showed decreased trends after PCI, and the decrease amplitude were relative intimately with the time of PCI, and particularly in the emergency group and the delayed group instead of elective group. QTc, QTd, QTcd is expected to be the indicators which reflects blood flow restoration and myocardial effectively reperfusion after PCI.III. QRS width of AMI patients and the postoperative LVEF was negatively correlated. After adjusting primary bundle branch block, QRS width is expected to be a summary indicator for the evaluation of cardiac function after AMI. IV. Postoperative QT, QTcd were related to postoperative cardiac function and LVD. the poorer cardiac function, larger LVD, the QTd, QTcd greater. Infarct site had significant influence on QTd, QTcd. Anterior group's QTd, QTcd were higher than non-anterior one. QT, QTc were little effected by infarction site.V. QRS width, QTd, QTcd had certain predicated significance to malignant arrhythmia. Timely monitoring of QTd, QTcd after PCI, may help to predict the occurrence in the near futureof major cardiac events such as ventricular fibrillation. VI. The notchs of premature ventricular and TS are strong predicted parameters of the long-term prognosis of patients with STEMI.
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