Discussion
Though no strict serial sequential assays, the myocardial injury was identified in 20 (91%) of 22 after TVCP. Average increased 3.599 URL cTn indicates substantial cardiac injury. Before cTn assay and term of myocardial injury, the best myocardial infarction biomarker was CK-MB. CK-MB slightly above URL in only 4 (18%) of 22, and average increased 0.1550 URL without statistically significant or clinic meaning. This may be why a high incidence of myocardial injury after TVCP was not noticed. Elevation CK and MYO values could attribute to perioperative non-cardiac muscle injury. Patients requiring emergency TVCP usually have an acute heart condition such as myocardial infarction, heart failure, cardiogenic shock, cardiac arrest10, and subsequently with the elevation of cTn values. Postoperative cTn levels are elevated after all types of cardiac surgery17, so it is a predictable elevation of cTn values for patients requiring TVCP to support cardiac surgery. In this study, elective TVCP was scheduled for non-cardiac surgery. So, patients were well prepared and relatively healthy. Risks of myocardial injury include hypoxemia, shock/hypotension, anemia, kidney disease, heart failure, ischemic heart disease11, but none of them recorded in those 22 cases. And baseline cTn values under URL, normal BNP, all of those limit the incidence of perioperative myocardial injury and reveal myocardial injury by TVCP. Hence, myocardial injury complicated with TVCP was an under-estimate complication.
Constant friction between the catheter tip and the ventricle wall could explain the myocardial injury. Cardiac perforation is an extreme example of mechanical damage. For permanent pacing lead, giant R wave on IC-ECG stands for continuous contact between electrode and ventricle wall. QS wave and lightly ST elevation on IC-ECG recommend for TVCP catheter,16, which indicate catheter tip is not continued touch with the ventricular wall. Since the heart systole and diastole constantly, there was a constant collision between the catheter tip and endocardium. Suppose heart rate 60 beats per minute, 86400 impacts happened in one day. Unlike permanent pacing lead fix to one spot, TVCP catheter tip may contact and injury a certain surface of endocardium.
The indication of TVCP must weigh the risks and benefits. Our study would aid in clinical decision-making to guide practice in their diagnosis, evaluation, and management. TVCP catheter is not just a foreign body to the heart, and the substantial cardiac injury should be a concern in TVCP placement. Myocardial injury is prognostically important and warrants clinical attention.18 Thought underlying pathophysiological mechanisms of myocardial injury after TVCP is different from the more common reason such as myocardial infarction, shock, poison, myocarditis; it contributes to a poorer outcome more or less. The complication rate of TVCP is 22.9% in the last 10 years, of which 10.2% is considered serious.3 The most common serious complication is re-intervention (5.4%), followed by cardiac perforation (1.6%).3Generally, perforations are asymptomatic,19, 20 usually seal on their own without causing any significant morbidity.16 An Analysis of > 360,000 Patients underwent TVCP in the United States between 2004 and 2014, concludes TVCP is generally safe with low pericardial complication rates (0.6%), which is a fivefold increase in risk for in-hospital death.10 But the in-hospital mortality rate was >10% and striking high mortality rate >50% over 4 years of follow-up, raise the concern to seek other complications and alteration of TVCP.3, 10, 21 Though the high mortality indicate a sick patient population, myocardial injury which is associated with an adverse prognosis12, 13 should be a concern. Hwang etc. evaluated the clinical differences between patients who have undergone TVCP and patients who have not. In their report, in acute inferior ST-elevation myocardial infarction and high-degree atrioventricular block, periprocedural TVCP in primary percutaneous coronary intervention do not decrease adverse cardiocerebrovascular events, but more likely increase cardiogenic shock and prolonged hospitalization.22 Myocardial injury may explain their result. High incidence of myocardial injury further support the guidelines recommendation that TVCP should be avoided or applied as briefly as possible,23 it may be best for the patient to avoid temporary pacing and proceed directly to permanent system implantation.1 It is a graded increase of major adverse cardiovascular events and mortality with higher postoperative cTn levels.24, 25 cTn release from the contractile apparatus of myocardial cells, average elevation in our study was 3.599 URL, indicate small amount injury of myocardial cells.11 cTn is not relate to endocardium, but endocardium is between contractile muscle and TVCP catheter. Since TVCP catheter tip do not fixed at one spot, endocardium damage would be broad. Consequence of large area endocardium damage, such as aggregation of platelets and the formation of thrombosis, ventricular arrhythmia should be the primary concern and worth further study.
This study has several limitations. First, it was conducted with a relatively small number of patients, resulting in an insufficient power to postulate generalizations. Second, myocardial injury cannot totally attribute to TVCP, since in patients with high cardiovascular risk, perioperative myocardial injury detected and quantified by an acute increase in high-sensitivity cTn plasma concentrations is a common complication after non-cardiac surgery occurring in 1 of 7 patients.26 Third, this is not a prospected study, monitor cTn of the patients was clinicians’ discretion; it is not consecutive series.