DISCUSSION
Our main results are the following: 1) permanent LPM implantation in
patients hospitalized in intensive care unit is feasible in 98% of
cases; 2) procedure-related complications are <5% in this
very high-risk population, with a virtually null risk of infection.
Pacemaker implantation in ICU patients is associated with several
challenging issues. Venous access is often limited due to the presence
of central venous lines for perfusion or hemodialysis or hemofiltration
[7,8]. In our series, 3 patients had no suitable supracaval venous
access for conventional pacemaker implantation. The alternative is
cardiac surgery with an epicardial approach, which appears highly
invasive in this critically ill population. The infectious risk is also
a major issue, amplified by multiple central venous lines, mechanical
ventilation, and ongoing sepsis or bacteremia [9-11]. More than half
of our patients were actually under intravenous antibiotherapy.
When atropine bolus or isoproterenol infusion are not sustainable
options, implantation of a temporary pacemaker is usually performed,
before considering PPM [12]. TTP is associated with a high rate of
complications [13]. In the US national database, pneumothorax,
pericardial tamponade and non-pericardial bleeding were found in 0.6,
0.9 and 2.4% of patients, respectively [14]. In a more recent
review of the literature, the total rate of complications related to TTP
ranged from 23% (in the 2010s decade, 5.7% considered serious
complications) to 43% (in the 1980s, 16.5% serious), including 2% of
complicated access, 1.6% of cardiac perforation, near 5% of
infections, and more than 20% of device complications [2]. TTP also
prolongs hospitalization with a mean of 11 days.
Patients hospitalized in ICU and requiring prolonged cardiac pacing are
frail and severe. Bradycardia <40 beats-per-minute adds 4
points to the APACHE II and 11 points to the SAPS II scores. In our
cohort, median Charlson comorbidity index was as high as 7 and
in-hospital mortality as low as 6%, as compared with a median score of
2 and an in-hospital mortality rate of 18% in a study by Christensen
and colleagues, although these 2 ICU populations cannot be directly
compared [15-17].
In that respect, LPM implantation is appealing. The Micra LPM is a small
0.8 cubic centimeter device, weighing barely 2 grams, implanted through
a femoral approach on the right ventricular septum (Figure 2 ).
The femoral approach solves the potential issues regarding supracaval
venous access, and the risk of device-related infection is virtually
nil, even in high-risk populations [6,18]. In our series, 60% of
patients had ongoing sepsis or documented bacteremia, of whom 92% were
under antibiotherapy, and no device infection occurred. Moreover, the
risk of dislodgement or pacing issue is extremely rare (<1%)
[19], to be compared with a risk of ~20% with TTP
[2]. The main issue with LPM is the risk of acute cardiac injury,
4% in our series, as compared with a less than 1% reported rate in the
literature [18]. This can be easily explained by the frailty and
multiple comorbidities of the ICU population. This risk could be further
decreased by positioning the device on the right ventricular septum
rather than at the apex, and with regular appropriate training [19].
The alternative to implant an active fixation lead connected to an
external re-sterilized pulse generator has also been shown to be
associated with a very low risk of complications, while being a
removable system [20]. However, this technique requires suitable
supracaval access and could not have been offered in up to 3% of our
patients.