## Limitations

Our calculations and the discussion above are not framed around the traditional form of cost-effectiveness measures such as incremental cost-effectiveness ratio (ICER) given that granular patient-level cost details were not available. However, our endeavour is to provide an estimate of the modular cost of implementing a program such as the TN STEMI Program de novo in settings such as LMICs where such infrastructure is either non-existent or rudimentary. We have used fairly conservative estimates in our imputations; the actual benefits could be higher, but will vary based on country and region. These costs will vary with nature of the health care and social system to which the program is being added. It is reasonable to assume that, depending on the existing health care infrastructure and management, program costs would be substantially different. In contexts with better infrastructure and fewer managerial inefficiencies, costs could be lower; on the other hand, in contexts with worse infrastructure and less management structure to build on, costs could be much higher. At the same time, it is possible that the benefits could also be lower and higher in these two different contexts. However, other formal ICER analyses of implementing STEMI networks in various countries have yielded similar values. For instance, the ICER of utilizing primary PCI for all-comers with STEMI in China was estimated at USD 10,700 [22]. Similarly, the Catalan STEMI study from Spain estimated the ICER of implementing a STEMI-network to be Euro 4,355 (USD 5,383) [23]. We also only considered mortality, but further benefits can be expected from reductions in morbidity as well.

## Final thoughts

For LMICs, the sharp increase in mortality and morbidity from non-communicable diseases such as ischemic heart disease presents one of the biggest challenges to sustained economic growth in the 21st century and beyond. Tragically, this is occurring despite tremendous strides in available management options for these conditions. For STEMI in particular, the current unstructured and highly inefficient system of management in most LMICs means that the gains from revascularization therapies noted in developed countries can seldom be achieved. Such a system puts the onus on patients (and their families), who are already in the throes of an MI, to have the wherewithal to present to the right hospital within the right timeframe and with the availability of immediate financial liquidity. We therefore believe that the large-scale adoption of a STEMI systems-of-care approach as studied in the TN STEMI Program represents a cost-effective investment for health systems to correct many such inequalities and social deprivation among this high-risk vulnerable patient population. Such investments will likely be repaid many times over in hundreds of thousands of lives saved each year, enhanced economic development, and strengthened global security.