AIM  To investigate the relationship and threshold effect between the Tp-Te/QT ratio, P wave dispersion and the risk of malignant arrhythmia in patients undergoing emergency percutaneous coronary intervention (PCI) after acute myocardial infarction (AMI).

METHODS A retrospective analysis was conducted in 200 patients who were admitted to our hospital from March 2020 to May 2024 and underwent emergency PCI after AMI. The patients were divided into two groups based on whether they developed malignant ventricular arrhythmias after treatment: occurrence group (58 cases) and non-occurrence group (142 cases). General clinical data, coronary angiography, echocardiography results and electrocardiogram (ECG) findings were collected and compared between the two groups. Multivariate linear regression analysis was used to examine the relationship between Tp-Te/QT, P wave dispersion and heart rate variability. Stratified regression analysis was performed to evaluate the relationship between Tp-Te/QT, P wave dispersion and the risk of malignant arrhythmia in different subgroups. Smooth fitting curves for Tp-Te/QT and P wave dispersion were established using R3.6.1 software, and threshold effect analysis was conducted to calculate the odds ratios (ORs) and their 95% confidence intervals (CIs) before and after the threshold points.

RESULTS Compared with the non occurrence group, the incidence group had a higher proportion of TIMI blood flow grade 0, a lower proportion of 3 grades (P<0.05), an increased LVEDD (P<0.05), a decreased LVEF (P<0.05), a lower proportion of Killip grade I, a higher proportion of (II-IV) grades (P<0.01), a lower SV (P<0.01), an increased NT-proBNP (P<0.01), an increased cTnI (P<0.01), and an increased LVESD (P<0.01); Compared with lower levels, higher levels of Tp Te/QT, QTd, and P-wave dispersion have a higher risk of malignant arrhythmia (P<0.05). Tp Te/QT and P-wave dispersion are independent risk factors that can predict the decrease of heart rate variability indicators SDNN, SDANN, and RMSSD (all P<0.05). Stratified analysis was conducted based on variables such as gender, age, BMI, number of stents implanted, Killip grading, and TIMI blood flow grading. The association between Tp Te/QT, P-wave dispersion, and the risk of malignant arrhythmia was statistically significant in each stratification (all P<0.05). Curve fitting analysis found that when Tp Te/QT ≤ 0.29, as Tp Te/QT increases, the risk of malignant arrhythmia in patients is not affected (OR=1.000, 95% CI: 0.894~1.120); when Tp Te/QT>0.29, as Tp Te/QT increases, the risk of malignant arrhythmia in patients significantly increases (OR=1.712, 95% CI: 1.294~1.821, P<0.05). When P-wave dispersion ≤ 42.28 ms, as P-wave dispersion increases, the risk of malignant arrhythmia in patients is not affected (OR=1.001, 95% CI: 0.822~1.531); when P-wave dispersion>42.28 ms As the P-wave dispersion increases, the risk of malignant arrhythmia in patients significantly increases (OR=1.312, 95% CI: 1.159~1.437, P<0.05).

CONCLUSION Tp-Te/QT and P wave dispersion are independent factors influencing the occurrence of malignant arrhythmias in patients after emergency PCI for acute myocardial infarction. Clinically, these parameters can be effectively used to predict the risk of malignant arrhythmias following PCI in such patients.