Million Hearts: Description of the National Surveillance and Modeling Methodology Used to Monitor the Number of Cardiovascular Events Prevented During 2012-2016

Abstract

Background: This study describes the national surveillance and modeling methodology developed to monitor achievement of the Million Hearts initiative's aim of preventing 1 million acute myocardial infarctions, strokes, and other related cardiovascular events during 2012-2016.

Methods and results: We calculate sex- and age-specific cardiovascular event rates (combination of emergency department, hospitalization, and death events) among US adults aged ≥18 from 2006 to 2011 and, based on log-linear models fitted to the rates, calculate their annual percent change. We describe 2 baseline strategies to be used to compare observed versus expected event totals during 2012-2016: (1) stable baselines assume no rate changes, with modeled 2011 rates held constant through 2016; and (2) trend baselines assume 2006-2011 rate trends will continue, with the annual percent changes applied to the modeled 2011 rates to calculate expected 2012-2016 rates. Events prevented estimates during 2012-2013 were calculated using available data: 115 210 (95% CI, 60 858, 169 562) events were prevented using stable baselines and an excess of 43 934 (95% CI, -14 264, 102 132) events occurred using trend baselines. Women aged ≥75 had the most events prevented (stable, 76 242 [42 067, 110 417]; trend, 39 049 [1901, 76 197]). Men aged 45 to 64 had the greatest number of excess events (stable, 22 912 [95% CI, 855, 44 969]; trend, 38 810 [95% CI, 15 567, 62 053]).

Conclusions: Around 115 000 events were prevented during the initiative's first 2 years compared with what would have occurred had 2011 rates remained stable. Recent flattening or reversals in some event rate trends were observed supporting intensifying national action to prevent cardiovascular events.

Keywords: Million Hearts; cardiovascular disease prevention; heart disease; hospitalization; mortality; myocardial infarction; stroke.

Figure 1

Million Hearts mutually exclusive event calculation methodology applied to the 2013 Nationwide Emergency Department Sample, National Inpatient Sample, and National Vital Statistics System data to determine the total number of mutually exclusive events. After applying the exclusion criteria, 343 214 ED visits, 2 099 874 hospitalizations, and 386 073 deaths were summed for a total of 2 829 161 mutually exclusive events that occurred in 2013. ED indicates emergency department. Additional details are included in Figure S1.

Figure 2

Million Hearts event rates before and during the Million Hearts initiative, by sex and age group, 2006–2013. Total rates were standardized by age to the 2010 US population. Bars denote 95% confidence intervals for the rates.

Figure 3

Estimated number of mutually exclusive Million Hearts events prevented in 2012 and 2013, by baseline strategy, sex, and age group. Determined by combining the observed event totals from the 2012 and 2013 and subtracting the expected number of events calculated by multiplying the 2011 modeled sex‐ and age‐specific rates (stable baselines) or by applying the annual percent change to the modeled 2011 rate for each sex‐ and age‐specific group to generate expected 2012 and 2013 rates (trend baselines) and multiplying those rates by the US Census mid‐year population estimates for 2012 and 2013, respectively. During 2012–2013, 115 210 (95% CI, 60 858, 169 562) events were prevented using the stable baseline; an excess of 43 934 (95% CI, −14 264, 102 132) events occurred using the trend baseline. Bars denote the 95% confidence intervals. Values denoted with an asterisk (“*”) are statistically significantly different than 0 (z‐score ≥|1.96|). Table S2 includes the sex‐ and age‐specific values for each year and for 2012 and 2013 combined.