Population Trends in the Incidence and Outcomes of Acute Myocardial

Infarction

Robert W. Yeh, MD MScMassachusetts General Hospital

Alan S. Go, MDKaiser Division of Research

University of California, San Francisco

The “Ecosystem” of Acute Myocardial Infarction

Obese population rising

DM & HTN increasing

Widespread use of statins

Increased use of smokingcessation programs

Better antiplatelet therapy

More use of beta blockers and ACE-I

Population at Risk for Myocardial Infarction

Aging of the population

NET EFFECT?

BACKGROUND

Existing Recent Literature on Myocardial Infarction Incidence

- Mostly limited to trends prior to 2002- Focused on groups with limited diversity with respect to race and ethnic group, age and sex- Have not distinguished ST and non-ST-elevation MI- Have not examined trends in improvements in outpatient cardiovascular medication use

Goals of Proposed Research

To provide a comprehensive, contemporary assessment of the epidemiology of STEMI and NSTEMI in a large population-based sample between 1999 and 2008

• An evaluation of progress in the care of MI patients• A test of the true impact of medical and public health

interventions• Suggestions for more optimal health resource allocation

OBJECTIVE

Kaiser Permanente of Northern California

• Integrated health care delivery system providing comprehensive care of ~3.3 million persons

• 20 medical centers + large set of ambulatory practices

• Diverse population representative of northern California and statewide

• Low churn rate

Incidence of Myocardial InfarctionIncidence rates of STEMI and NSTEMI calculated for

each year

– All Kaiser members age ≥ 30– Numerator: Hospitalized admission for MI based on ICD-9-CM

primary discharge diagnosis.• STEMI: 4101 – 410.6, 410.8• NSTEMI 410.7, 410.9• Codes validated by detailed chart review in a random sample

of 800 MI admissions.– Denominator: Person-months, annualized, based on monthly

updated membership status.– Direct Age-Sex adjustment

METHODS

Health plan databases capture the large majority of aspects of clinical care and linked through single medical record number

• Detailed demographic information• Multiple data sources to ascertain comorbid conditions• Longitudinal outpatient prescription medication use

before and after incident MI• Outcomes – detailed discharge and billing codes with

access to medical records; linked to state death files and Social Security Administration vital status data

Comprehensive Clinical and Administrative Electronic Databases

Cardiac Biomarkers– Peak CK-MB and MB fraction ascertained for all identified MI

admissions

Mortality– 30-day all-cause mortality ascertained from linked health plan

administrative databases, proxy information, Social Security Administration vital status files, and California state death certificate information

– Logistic regression using generalized estimating equations to account for facility-based clustering used to examine trends in yearly adjusted mortality.

Outcomes

Incidence of Myocardial Infarction46,086 hospitalized patients with myocardial infarction over

18,691,131 person-years

RESULTS

Age-Sex-Adjusted Incidence of Myocardial Infarction by Year

0

50

100

150

200

250

300

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Inc

ide

nc

e(p

er

10

0 0

00

pe

rso

n-y

ea

rs)

Any MI

NSTEMI

STEMI

Medication Use

Outpatient Medication Use Prior to Myocardial Infarction

0

10

20

30

40

50

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Pro

po

rtio

n o

f U

se (

%)

ACE-I/ARB

Thienopyridine

Non-Statin Lipid Lowering

β-Blocker

Statin

0

10

20

30

40

50

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Revascularization after MI

Biomarkers

• Troponin I testing increased from 53% in 1999 to 84% in 2004– Stable testing rates after 2004

• Peak CK-MB and CK-MB fraction decreased significantly over time for all MI and for NSTEMI.

• No change in biomarker peak levels over time after STEMI

Adjusted Mortality Rates

Adjusted Odds Ratio for 30-Day Mortality After MI by Year

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Ad

just

ed O

R (

vers

us

1999

)

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Adjusted Odds Ratio for 30-Day Mortality After MI by Year

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Ad

just

ed O

R (

vers

us

1999

)

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Adjusted Mortality0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Adjusted Odds Ratio for 30-Day Mortality After STEMI by Year

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Ad

just

ed O

R (

vers

us

1999

)

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Adjusted Odds Ratio for 30-Day Mortality After STEMI by Year

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Ad

just

ed O

R (

vers

us

1999

)

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Adjusted Odds Ratio for 30-Day Mortality After NSTEMI by Year

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Ad

just

ed O

R (

vers

us

1999

)

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Adjusted Odds Ratio for 30-Day Mortality After NSTEMI by Year

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Ad

just

ed O

R (

vers

us

1999

)

Conclusions• There has been a 24% decline in the incidence of MI since 2000,

with steep decline in STEMI incidence throughout time period.

• Significant improvements in the outpatient use of cardiovascular medications including statins and beta blockers have occurred, which may, in part, explain declines in MI incidence.

• Lower severity NSTEMI have been detected over time, coinciding with increased use of troponin.

• Improvements in adjusted mortality have been modest, and are likely driven by in part by increased ascertainment of low-acuity NSTEMI

Limitations

• Reliance on diagnosis codes– Sensitivity analyses that broadened the definition of MI to include

other codes showed similar trends.– Trends in STEMI and NSTEMI were similar at 95% confidence

limits of positive predictive value of codes based on validation.

• Large, diverse population but may not be completely generalizable to all health care settings and populations

Whether declines in MI incidence have occurred similarly in other geographic regions is not known.

Thank You