A cost analysis of cardiac magnetic resonance imaging in the diagnostic pathway of a population with unexplained acute myocardial injury and normal coronary angiography

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): National Institute for Health Research (NIHR) Biomedical Research Centre at St Bartholomew"s Hospital London. Irish Cardiac Society

OnBehalf

European Association of Cardiovascular Imaging (EACVI) -Task Force for Cost Effectiveness.

Background

Acute presentations with myocardial injury that occur despite culprit-free coronary angiography were first reported over 70 years ago, with a prevalence between 5-9%.  1-3 There is increasing evidence that a more accurate diagnosis is available and that CMR is a key tool to determine the underlying pathology. This is reflected with the most recent international guidelines advocating for the use of CMR in the diagnostic pathways of this heterogeneous population.  However, to date there is no formal assessment of the financial implications of adopting these new guidelines.

Purpose

To determine the financial impact of implementing cardiac magnetic resonance imaging in the diagnostic pathway of a population with unexplained acute myocardial injury and normal coronary angiography in comparison to existing clinical practice.

Methods

We performed a focused cost-benefit analysis using a hypothetical population of 2,000 patients with unexplained acute myocardial injury and normal coronary angiography.  The population was split evenly into two groups of either standard, or CMR guided management, and extrapolated over a ten-year period. Standard management was defined as 66% of the population receiving dual antiplatelet therapy (ticagrelor and aspirin) for one year followed by aspirin for life, and the remaining 34% of the population receiving aspirin for life. CMR guided management determined antiplatelet therapy according to the imaging findings. This analysis focused on CMR’s ability to accurately identify those patients who may have had an MI and facilitate tailored treatment with evidence based dual antiplatelet therapy. Costs and rates were defined in Table 1. A one-way sensitivity analysis was also performed to determine the variables with largest impact on the costs. Each variable was varied by +/- 20% and the change in cost determined at year 10.

Results

Using CMR in the diagnostic pathway resulted in an increased cost of £72,656 in the first year. After year 7, CMR guided practice becomes cost neutral, resulting in cost saving of £24,054 over a ten-year period in a population of 1000 patients. Figure 1. Utilizing CMR in this population also resulted in 7 fewer myocardial infarctions and 14 fewer major bleeding events over a ten-year time horizon.

The three most sensitive variables were, in decreasing order, the cost of CMR, the cost of ticagrelor and the percentage of the population with MI requiring DAPT. A 20% change from baseline resulted in a 320%, 247% and 162% change in costs at 10 years, respectively.

Conclusion

Utilizing CMR in this population may be associated with reduced costs in the medium to long term. The initial increased cost of CMR is offset over time, by delivering a more personalised, higher quality level of care to patients.

Generation of catalytically active granzyme K from Escherichia coli inclusion bodies and identification of efficient granzyme K inhibitors in human plasma

Granzymes are granule-stored lymphocyte serine proteases that are implicated in T- and natural killer cell-mediated cytotoxic defense reactions after target cell recognition. A fifth human granzyme (granzyme 3, lymphocyte tryptase-2), renamed as granzyme K (gene name GZMK), has recently been cloned from lymphocyte tissue. For its further characterization we successfully generated catalytically active enzyme in milligram quantities per liter of Escherichia coli culture. The natural proform of granzyme K with the amino-terminal propeptide Met-Glu was expressed as inclusion bodies and converted to its active enzyme by cathepsin C after refolding of precursor molecules. Recombinant granzyme K cleaves synthetic thiobenzyl ester substrates after Lys and Arg with k(cat)/K(m) values of 3.7 x 10(4) and 4.4 x 10(4) M(-1) s(-1), respectively. Granzyme K activity was shown to be inhibited by the synthetic compounds Phe-Pro-Arg-chloromethyl ketone, phenylmethylsulfonyl fluoride, PefablocSC, and benzamidine, by the Kunitz-type inhibitor aprotinin and by human blood plasma. The plasma-derived inter-alpha-trypsin inhibitor complex, its bikunin subunit, and the second carboxyl-terminal Kunitz-type domain of bikunin were identified as genuine physiologic inhibitors with K(i) values of 64, 50, and 22 nM, respectively. Inter-alpha-trypsin inhibitor and free bikunin have the potential to neutralize extracellular granzyme K activity after T cell degranulation and may thus control unspecific damage of bystander cells at sites of inflammatory reactions.