AbstractIntroduction: It is not unusual for temporary transvenous cardiac pacing (TVCP) leads to penetrate and occasionally perforate the right ventricular wall, which generally is asymptomatic. The definition of myocardial injury is evidence of elevated cardiac troponin (cTn) values above the 99th percentile upper reference limit (URL). Myocardial injury is associated with an adverse prognosis. The present study was designed to evaluating myocardial injury complicated by TVCP.Methods: Retrospective study from August 2018 to March 2020, 33 consecutive patients undergo elective TVCP support for non-cardiac procedures, 22 of them had cardiac biomarkers assays before and after TVCP. These 22 eligible patients had a median age of 66 (50-83) years, 6 (27.3%) were women, and all baseline cTn <1 URL. Compare cardiac biomarkers before and after TVCP.Results: 20 (91%, N=22) patients detect cTn >1 URL after pacing. Paired t-test compare before and after pacing leads insertion showed a mean cTn elevation of 3.599 (95% CI, 1.566 to 5.632, P<0.01）URL, and no significantly creatine kinase-MB elevation of 0.1550 (95% CI, -0.01239 to 0.3224, P>0.05 ) URL.Conclusion: This study demonstrates a high incidence of substantial myocardial injury by TVCP, which should be concerned.Introduction:Temporary transvenous cardiac pacing（TVCP）is a reliable heart rate control and potentially life-saving intervention. Primary indication is life-threatening bradyarrhythmia with hemodynamic compromise, include bradyarrhythmia due to atrioventricular blocks or sinus node dysfunction. Other indications include tachyarrhythmias needing overdrive pacing, and dysrhythmias needing rate support to allow the use of medications directed toward treatment of tachyarrhythmias that might exacerbate bradycardia such as beta blockers.1, 2Complications can be considered in two broad categories: relate to the venous access or relate to pacing catheter.3 The use of ultrasound guidance result in safer venous access, and the complication rate is statistically insignificant between novice and experienced clinicians.4Central venous access–associated complications were rare when venous access was obtained with ultrasound guidance.5-7Complications or concerns relate to pacing catheters also can be divided into two categories: electrical performance and mechanical effects.2 Electrical performance requires proper catheter placement, the lead stability, firm connections to the external generator, and external generator management to achieve pacing function. But mechanical effects are adverse complications.The TVCP lead is relatively stiff, promotes ventricular ectopic activity, or ventricular tachycardia during catheter insertion is common and occasionally prolonged ventricular arrhythmias.8 It is not unusual for these leads to penetrate and occasionally perforate the right ventricular wall.2 This is usually manifest by raised pacing thresholds and occasionally by pericarditic pain and a pericardial friction rub.9 Rarely this will result in cardiac tamponade which associated with increase in risk for in-hospital death10. Pericardial tamponade, perforate or penetrate the ventricular wall are literally myocardial injuries. The term myocardial injury used nowadays is when there is evidence of elevated cardiac troponin (cTn) values with at least one value above the 99th percentile upper reference limit (URL).11 Myocardial injury is associated with an adverse prognosis.12, 13 However, there is no study evaluating myocardial injury complicated with TVCP by cTn assays. Therefore, the objective of this study was to investigate myocardial injury caused by TVCP.Methods:Study design and patientsRetrospect study consecutive 33 cases/patients undergo elective TVCP placed by the first author (Meng L) for scheduled non-cardiac surgery from August 2018 to March 2020. 22 of them have measured cardiac biomarkers values before and after TVCP placement. Analysis of the values changes of the cardiac biomarkers. The Hunan Provincial People’s Hospital Ethics Committee granted study approval (reference number: 2020-07) and waived the usual requirement for informed consent as all data were de-identified and analyzed anonymously.22 eligible patients had a median age of 66 (50-83) years, and 6 (27%) were women, 13 (59%) from the cancer center, others from hepatobiliary surgery, general surgery, and spine surgery department. None of the patients had history recorded of myocardial infarction, stroke, heart failure, chronic kidney disease, anemia. No remarkable structure abnormality findings in echocardiography. B-type natriuretic peptide (BNP) and hemoglobin were normal. Except for slightly elevated creatinine in 1 case (120.5umol/L), creatinine was normal. Decisions of TVCP were made by surgeons after consultation with cardiologists or/and anesthesiologists. Except for the bradyarrhythmia, patients with low cardiovascular risk, so TVCP were simply placed bedside, rather than catheter lab. TVCP indications and baseline characteristics of patients included in table 1.Table 1. Baseline characteristics of patients and indication of temporary transvenous pacing.CharacteristicAll（N=22）Age，y55-83 (median 66)Female6 (27.3%)Hypertension3 (13.6%)Diabetes mellitus3 (13.6%）Coronary artery disease1 (4.5%)Smoking8 (36.4%)Surgery typeTumor ectomy 13 (59.1%)Bile duct stones 4 (18.2%)Spine diseases 3 (13.6)Intestinal obstruction 1 (4.5%)Hernia 1 (4.5%)IndicationMobitz type II AVB 1 (4.5%)Sinus pause 1 (4.5%)Sinus bradycardia andJunctional rhythm 1 (4.5%)SVT/AT 2 (9.1%)1°AVB & CRBBB 1 (4.5%)High risk intraoperative bradycardia 12(54.5%)Absent response to atropine test 4 (18.2%)Caption of table 1: Sinus bradycardia: Sinus rate <50 bpm; AVB, atrioventricular block; CRBBB, complete right bundle branch block; SVT: supraventricular tachycardia; AT: atrial tachycardia.TVCP catheter was placed within 12 hours before surgery. The catheter placed from 6 to 24 hours, and withdraw soon after surgery in 21 cases, placed 3 days in 1 case. Cardiac biomarkers values were measured within 2 weeks before TVCP and at night (2) or next morning (20) after surgery.2, Material and temporary pacemaker placementMaterialMedtronic, model 5348 or 5392 temporary pacemaker. 7 French (F) hemostasis introducer (Fast-CathTM & Cath-LockTM, ST. JUDE MEDICAL) and 6 F non-floating right heart curve bipolar pacing catheter (PACELTM, ST. JUDE MEDICAL). Catheter tip has two electrodes, which are about 1 cm apart. The distal tip is a negative and active electrode, and the proximal electrode is positive and indifferent.Bedside temporary pacemaker placementThe primary access site was through the right internal jugular vein (16 cases, 73%), followed by subclavian vein (4 cases, 18%) when surgery involved the right neck. The femoral vein approach was used (2 cases, 9%) after difficulty was experienced in advancing TVCP catheter through the subclavian vein or right internal jugular vein site. Except for subclavian vein access, all central venous access was under ultrasound guidance.Pacing catheterization guided by bipolar (both proximal electrode and distal electrode connect to separate V lead) intracavity electrocardiography (IC-ECG).14, 15The bipolar IC-ECG monitoring plus direction control skill of the catheter tip made bedside TVCP catheter placement feasible and ‘visible’.14Target proximal electrode IC-ECG was slightly ST-segment elevation <2 mV which constitute a proper position against the ventricular wall and adequate pacing site,16 but it is impossible to maintain it if patient change positions (Fig 1). All placement was further confirmed by following standard 6-lead pacing ECG that II, III, and aVF QRS waves downward.Figure 1. Unstable pacing lead.