6Medtronic, Inc., Mounds View Minnesota,
United States
7London Health Sciences Centre, Ontario,
Canada
We have read the comments made by Mealing and colleagues and appreciate
the opportunity to further clarify certain aspects of our work. Thank
you for your interest in our manuscript. The model employed a 3-month
cycle time, selected because of the life-long time horizon. No patient
in the model was “immune” to complications as the full cohort of
patients having a replacement faced the probability of complication at
the transition between the ‘generator replacement’ and ‘replacement
complication’ states. This was intended to represent an average timing
of peri-procedural complications which could occur either during the
procedure or for 6-12 months afterward. The complications have proper
impact on the overall mortality and cost calculations, and any error
related to timing would be limited to a one-cycle difference in the
discounted results which is minimal.
The perspectives for each country were chosen to represent the
stakeholder most likely to impact the decision of ICD type given an
indication for therapy. In the US, a fractionated payer system pays for
a generic procedure and does not differentiate between models, so the
choice is made at the hospital. The rest of the countries have more
unified payers with some even employing model-specific reimbursement
payment amounts.
Device longevity was not fixed in the model, there was a time-varying
probability of device replacement. It was based on clinical observation
from patients in the Pivotal study (NCT04060680) combined with
engineering model projections as displayed in Figure 2. We did
acknowledge uncertainty about this in the limitations (“Modeled
longevity…could be impacted by changes in technology”) and
incorporated a robust sensitivity analysis varying the expected
longevity by two standard deviations based on current data. We
acknowledge that the substernal defibrillator is new technology, but
there is robust post-market clinical study activity that will enhance
the evidence base (NCT06048731). We accounted for concerns about
uncertainty in cost parameters a similar way and found in the
sensitivity analysis that cost had an even smaller impact on model
outcomes.
The substernal ICD carries a strong mechanism for comparative energy
efficiency. With a projected 60% improvement in device longevity, one
would expect the avoided replacement surgeries and cost savings
predicted by this model.