Comment
The primary endpoint of this study was 6-month survival in postapproval
(post-trial) patients who received the HM3 as a primary device in the
United States. Our single-center 6-month survival for post-trial
patients is 93.3%, which mirrors the 6-month survival in the trial
group from our center (93.8%). Our postapproval patients were not
selected based on strict inclusion criteria as set for the trial
patients. As a result, younger acutely and critically ill patients
underwent implantation of the HM3 who otherwise would not have qualified
for the HM3 device during the trial phase. This population reflects
real-world experience. Although our trial and postapproval patients were
not statistically different based on overall baseline INTERMACS profile(p=0.17) , the postapproval group included more patients with
INTERMACS profile 1 (p=0.04 ) than the trial group, and these
patients required a higher degree of hemodynamic support with Impella
5.0, Tandem, or ECMO devices (p=0.01 ). At our center, we have
historically seen higher percentages of INTERMACS 1 and 2 profile
patients than reported in the MOMENTUM 3 and European postapproval
ELEVATE registry (73.9% vs 32.3% vs 31%,
respectively).10,12 This difference in patient
profiles can be attributed to differences in patient populations,
referral patterns, and differences in access to health care facilities,
insurance coverage for advanced therapies, and late transfers from
outside institutions (our center is the only heart transplant and LVAD
center for the state of Louisiana). Another explanation for this
difference can be related to the fact that because the trial findings
showed a significant improvement in the device hemocompatibility profile
when compared with the previous generation devices, surgeons at our
center had more confidence in implanting the HM3 in sicker patients vs
other devices.
Our postapproval group patients were younger than the trial group
patients because the HM 3 device was used in all comers, including
patients who were upgraded from IABP to higher support devices (Tandem,
Impella, and ECMO) due to ongoing cardiogenic shock while on IABP
support ( which was an exclusion for the trial patients). Due to
postapproval group consisting of more young patients, a higher
percentage of these patients were BTT candidates as compared to the
trial group (p=0.05). Also, the postapproval group had a statistically
elevated pre-operative INR (a decreased synthetic function of the liver)
compared to the trial group, reflecting a higher degree of illness
(p=0.04).
Six deaths occurred in the postapproval group and five deaths in the
trial group. Two patients in the trial group and four in the
postapproval group were transplanted within the first 6 months of their
LVAD implant. Six-month postapproval survival data are comparable with
the results from the MOMENTUM 3 trial and the primary implants cohort of
the ELEVATE registry (93.3% vs 88% vs 92%,
respectively).10,12 The observed long-term benefit of
the HM3 vs the previous generation of CF-LVADS is a marked reduction in
stroke rates.13 Stroke rates 6 months after an implant
at our center were comparable between the trial and postapproval groups
(7.3% vs 4.4%; p =0.52). However, the stroke rate at our center
is comparable to the 6-month MOMENTUM 3 and postapproval ELEVATE
registry (4.4% vs 7.9% vs 5.4%, respectively).7,10The lower rate of stroke seen at our center could be attributed to our
adherence to robust blood pressure and anticoagulation management
protocols.14,15
A significant reduction in re-exploration rates was observed in the
postapproval group. This observation can be explained by a series of
changes made during the perioperative phase of the implant: modification
in surgical technique (placing 16 vs 12 pledgetted stitches around the
sewing ring), preoperative administration of vitamin K (2 doses 24 hours
prior to implantation), and use of thromboelastogram analysis for
correction of coagulopathy prior to leaving the operating room. Lessons
learned during the trial phase showed that the majority of patients who
underwent re-exploration for bleeding had a bleeding site at the apical
sewing ring. Increasing the number of pledgetted stitches from 12 to 16
eliminated bleeding from the sewing ring site. We have determined that
administration of 2 doses of vitamin K 24 hours prior to LVAD
implantation reduces bleeding complications. Vitamin K administration
has become a part of our routine and was used during the postapproval
phase of device implantation.16
Pump thrombosis was comparable between the two groups, and all cases of
pump thrombosis were related to outflow graft twist identified by
computed tomography scan. All patients presented with acute onset
low-flow alarms. At the time of pump exchange, thrombus was present in
the outflow graft extending into the HM 3 device. All of these patients
underwent successful pump exchange with full recovery. The incidence of
outflow graft twist has now been completely eradicated with the changes
in the spline cover of the HM3 pump.
The MCS-ARC definition of acute severe RVF was used for
analysis.11 A reduction in the incidence of severe RVF
requiring inotropes >14 days was observed in the
postapproval group (34.8% vs 41.5%; p =0.36) compared to the
trial group patients. This finding can be explained by our incremental
improvement in understanding the HM3 device, improved perioperative
management, and a significant reduction in the incidence of
postoperative bleeding requiring re-exploration (a well-established risk
factor for the development of RVF).17-23 Also, the
incidence of right ventricular assist device (RVAD) use for severe RVF
was similar between the two groups.