Relationship Between Perioperation Risks Of Stenting In Left And Right Coronary Artery And Regional QT Dispersion

The techniques of percutaneous transluminal coronary angioplasity(PTCA) exploit a new way for the diagnosis and therapy of coronary heart disease(CHD). Mortality of CHD (especially acute myocardial infarction, AMI) has reduced signally since the use of coronary stent in clinic came into reality. With the popularization and development of coronary interventionai technique, people came to realize perioperation period plays an important role in the intervention. Usual causes for cardiac death include acute thromobosis, subacute thromobosis and sudden fatal arrhythmia, etc. The study focuses on the chance of latent fatal arrhythmia through regional difference of QT dispersion (QTd). Thus we can speculate the perioperation risks of interventional therapy in left and right coronary artery. QTd of CHD patients who successfully underwent PTCA and stenting surgery were selected to evaluate the accident risks after interventional therapy in coronary care unit.Materials and Methods130 patients with CHD (angina and AMI) were enrolled in this study, all of whom showed stenosis of coronary artery≥70%, underwent PTCA and stenting successfully. 86 male and 44 female were 46～83 years old (average 64.3±9.7 years old). 76 patients were diagnosised as angina, 30 and 24 patients as AMI and OMI respectively. 88 cases for left coronary artery lesion, 114 stents were implanted; 42 cases for right coronary artery lesion, 60 stents were implanted. Average stenosis of coronary artery before operation is 89.1+7.8%, residual stenosis after operation was below＜10% in this study.All of 130 cases were simply left or right coronary artery stent (those who implant left and right coronary artery stents were excluded). 68,40,6 and 60 stents were implanted in left anterior descending (LAD), left circumflex (LCX), intermediate branch, and right coronary artery (RCA), respectively. 60,26 and 90 lesion were type A, B and C, respectively.Judkin's method was used to insert 6F or 7F catheter through femoral artery to perform coronary artery and left ventricular angiography. Multi-angle projection was used to ascertain the type and place of the lesion. Balloon dilation should reach satisfaction before stent were implanted in coronary artery. Proportion between diameter of the stent and vessel was 1:1～1.1:1. The severity of the lesion was presented by the area of coronary artery stenosis. All the cases were treated according to conventional therapy of coronary stenting procedure before, inter and after the surgery. The criteria for successful stenting should be: the stent should stride over lesion of the aimed artery and dilating enough according to demand. Perfusion of coronary blood follow should reach TIMI 3.12 lead electrocardiograms (ECGs) were conventionally recorded in all the patients 1 day before, and 1,2,3 days after operation. At least 3 QT intervals were measured in each lead to calculate the average value. QT intervals of leadâ…¡,â…¢aVF, V_7～9 were measured to represent the region of myocardium dominated by RCA(inferior wall myocardium). QT intervals of leadâ… , aVL, V₁～V₆ were measured to represent myocardium dominated by left coronary artery (anterior wall myocardium). Terminal of QT interval should be judged by:â‘ the crossway between T wave and equipotential line;â‘¡the incisura between T and U wave, if U wave appeared;â‘¢the crossway between the desending of T wave and equipotential line. Minus between maximal QT interval and minimal QT interval were difined as the QT dispersion (QTd). QTd should be corrected by heart rate according to Bazett formulation: QTc=QT/RR^1/2. QTcd was the corrected QT interval dispersion. The formulation could be difined as: QTd=QTmax-QTmin. QTcd=QYcmax-QYcmin.ResultsThe changes of QTd in 130 CHD patients underwent PTCA and stenting were as the following: QTd and QTcd of patients before operation were 61.36±22.19ms and 67.13±10.05ms, beyond their normal range. After successful PTCA and stenting, QTd and QTcd were decreased signally, 1, and 3 days after operation (p＜0.05). The heart rate had no significant difference before and after operation. We can speculate that the coronary flow became fluency after stenting, the ischemic myocardium attained enough oxygenation blood, hibemating myocardium and stunned myocardium resuscitated. Thus the electrical activity of the myocardium became stabilized. And it provided another evidence that revascularization of coronary artery served as an effective therapy to cure CHD patients.For CHD patients, the accident ratio (AMI, sudden death) in perioperation was different. It depended on which coronary artery the lesion lies in. The QTd and QTcd of patients underwent right coronary artery stenting were significantly longer than those underwent left coronary artery stenting 1,2,and 3 days after operation. QTd and QTcd were 54.22±17.45ms and 54.00±33.33ms in patients underwent right coronary artery stenting, compared with that of 41.44±16.42ms and 49.23±42.10ms in patients underwent left coronary artery intervention (P＜0.05). So we must keep guard when perform RCA intervention, pay more attention in perioperation period to prevent the onset of cardiac events. Fortunately, QTd and QTcd decreased gradually in both patients underwent RCA or left coronary artery intervention. Patients became more and more safe. So it was important for us to keep guard and prevent fatal arrhythmia in perioperation, it was a key period.For instance, the QTd and QTcd of myocardium dominated by left coronary artery or RCA were measured separately 1 day after operation. For patients underwent RCA intervention, QTd and QTcd were 55.56±15.97ms and 61.45±28.86ms in leadâ…¡,â…¢, aVF, V₇, V₈ and V₉ (reflecting the blood flow of RCA), significantly higher than that in lead V₁-V₆,â… , and aVL (reflecting the blood flow of left coronary artery) QTd and QTcd being 50.42±17.45ms and 52.00±32.21ms, respectively. For patients underwent left coronary artery intervention, it was quite the contrary: QTd and QTcd were 46.41±16.42ms and 59.18±42.23ms in leads V₁-V₆,â… , and aVL, significantly longer that in leadsâ…¡,â…¢, aVF, V₇, V₈ and V₉ (QTd and QTcd being 41.21±10.97ms and 48.22±33.20ms, respectively)(P＜0.05). We came to the conclusion that: both stenosis in CHD patients and the procedure of revasculation injured the myocardium dominated by the coronary artery. So we must pay more attention to this fatal arrhythmia when we proceeded coronary intervention. For example: lesion of RCA caused third degree A-V block, lesion of left coronary artery caused ventricular fibrillation.ConclusionThis article investigate the variance of QTd during the course of PTCA and stenting and demonstrate that successful PTCA and stenting increase the perfusion of the myocardium, decrease QTd significantly. The electrical activity of myocardium becomes stabilized 1 day after operation. Successful PTCA and stenting improve perfusion of the myocardium, decrease the nonuniform repolarization, and improve the prognosis of patients with CHD. There is no obvious change of heart rate before and after operation.QTd and QTcd in different leads change a lot after PTCA and stenting of RCA and left coronary artery. QTd and QTcd in leads of inferior wall myocardium are longer than that in leads of anterior wall myocardium in patients underwent RCA intervention. Whereas QTd and QTcd in leads of anterior wall myocardium are longer than that in leads of inferior wall myocardium for patients underwent left coronary artery intervention. In this way we can see the regional difference through the variance of QTd and QTcd in different leads.In short, QTd and QTcd of RCA after coronary intervention are longer than that of left coronary artery. So the chance for fatal arrhythmia is significantly higher in RCA intervention group than that in left coronary artery intervention group. Since the safety of patients after coronary intervention increases a lot, in coronary care unit we must pay more attention to patients underwent RCA intervention in perioperation.