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.