Cardiovascular Risk Factors in Veterans with SCI and Acute Myocardial Infarction

Sunil Sabharwal, MD1,2; Pat Woods MSN1; Kelly Stolzmann1; Ram Sharma1; Errol Baker1

1VA Boston Health Care System; 2Harvard Medical School

Acknowledgements

Supported in part by the Department of Veterans Affairs, Office of Research and Development, Health Services Research and Development ,Grant # RRP 11-013

VA IHD QUERI Elliot Lowy G. Blake Wood

VA SCI QUERI Bridget Smith Fran Weaver

Heart Disease is a leading cause of morbidity and mortality in SCI

Whiteneck GG, Charlifue SW, Frankel HL, Fraser MH, Gardner BP, Gerhart KA et al. Mortality, morbidity, and psychosocial outcomes of persons spinal cord injured more than 20 years ago. Paraplegia 1992; 30: 617–630.

DeVivo MJ, Krause JS, Lammertse DP.Recent trends in mortality and causes of death among persons with spinal cord injury. Arch Phys Med Rehabil. 1999 Nov;80(11):1411-9

Garshick E, Kelley A, Cohen SA, Garrison A, Tun CG, Gagnon D, Brown R. A prospective assessment of mortality in chronic spinal cord injury.Spinal Cord. 2005 Jul;43(7):408-16.

Conventional risk factors for heart disease are well established in the general population

Non-modifiable Older age Male sex Family history of early heart disease

Modifiable Hypertension Cigarette smoking Hypercholesterolemia, lipid disorder Diabetes Other: Obesity, lack of physical activity

Novel or non-traditional

▪ Khot UN, Khot MB, Bajzer CT, Sapp SK, Ohman EM, Brener SJ, Ellis SG, Lincoff AM, Topol EJ. Prevalence of conventional risk factors in patients with coronary heart disease. JAMA. 2003 Aug 20;290(7):898-904

Role of cardiovascular risk factors in SCI:Literature exists but is limited/inconclusive

Bauman WA, Spungen AM. Coronary heart disease in individuals with spinal cord injury: assessment of risk factors. Spinal Cord. 2008 Jul;46(7):466-76.

  Cragg JJ, Noonan VK, Krassioukov A, Borisoff J.

Cardiovascular disease and spinal cord injury: results from a national population health survey. Neurology. 2013 Aug 20;81(8):723-8.

Wilt TJ, Carlson KF, Goldish GD, MacDonald R, Niewoehner C, Rutks I, Shamliyan T, Tacklind J, Taylor BC, Kane RL. Carbohydrate and lipid disorders and relevant considerations in persons with spinal cord injury. Evid Rep Technol Assess (Full Rep). 2008 Jan;(163):1-95.

Objectives

Compare the prevalence of conventional cardiovascular risk factors (hypertension, lipid disorders, diabetes, and smoking) in individuals with and without spinal cord injury (SCI) who develop acute myocardial infarction (AMI)

Study design

Retrospective cohort study of veterans with and without SCI hospitalized with AMI at any Veterans Administration (VA) hospital between July 2003 and December 2010

Data Sources

VA Cardiac Care Follow-up Clinical Study (CCFCS) data repository: ▪ Includes data, abstracted by trained abstractors using standard

reporting forms, on all patients hospitalized with a discharge diagnosis of AMI at any VA medical center from July 2003-Dec 2010▪ In addition to all patients with AMI (ICD-9 codes 410.x), ~10% of CCFCS includes a

random sample of patients with unstable angina without AMI (ICD-9 codes 411.x)

VA Spinal Cord Dysfunction (SCD) registry: ▪ Includes information about characteristics of SCI. ▪ Individuals with SCI were identified in the CCFCS database and cross-

matched with the VA SCD registry to obtain information about neurological level and completeness of SCI.

Chart review▪ If missing information about SCI level and completeness in SCD registry

Defining the Study Population

SCI and non-SCI cohorts established

Defining the SCI cohort ICD-9 codes:806.0 – 806.9 (fracture of vertebral column with

SCI), 907.2-907.3 (late effects of spinal cord injury), 952.00-952.9 (spinal cord injury without evidence of spinal bone injury), 344.0-344.09 (quadriplegia), 344.1 (paraplegia)▪ Excluded patients with multiple sclerosis and ALS

Excluded from both SCI and non-SCI cohorts Inter-hospital transfer after presenting to a community hospital AMI occurrence during inpatient stay Females – constituted < 2% of the study population in both

groups. Unstable angina without AMI (ICD-9 411.x)

VA Cardiac Care Follow-up Study Data Repository

(N=96,025)

SCI Diagnosis (n=479)

SCI with AMI (n=465)

SCI Patients Presented to VA

ER with AMI (n=223)

SCI Males Presented to VA

ER with AMI (n=191)

Final SCI AMI Group (n=191)

Excluded: Females (n=3); Incorrect SCI

diagnosis (n=29)

Excluded: Developed AMI as inpatients (n=190); Transfer

from community hospital (n=52)

Excluded: Unstable angina

w/out AMI (n=14)

Non-SCI (n=95,560)

Non-SCI with AMI (n=86,206)

Non-SCI Patients

Presented to VA ER with AMI (n=56,951)

Non-SCI Males Presented to VA

ER with AMI (n=55,958)

Final Non-SCI AMI Group (n=55,958)

Excluded: Females (n=993)

Excluded: Developed AMI as inpatients

(n=15,364);Transfer from

community hospital (n=13,891)

Excluded: Unstable angina

w/out AMI (n=9,354)

Defining the SCI & non-SCI Cohorts

Study Variables

Patient demographics, cardiovascular history and risk factors, AMI characteristics

SCI characteristics (Neurological level and completeness of SCI). For analyses we grouped SCI into 4

groups: High-Complete, High-Incomplete, Low-Complete, and Low-Incomplete.

Analyses

Prevalence of individual cardiovascular risk factors was identified in the SCI and non-SCI cohorts (and for each of the SCI sub-groups) from the CCFCS database

Multiple logistic regression was used to assess the significance of select cardiovascular risk factors (hypertension, lipid disorder, diabetes, cigarette smoking, and age) on SCI status

SCI & Non-SCI Cohorts with AMI: Logistic Regression

SCIN = 191

Non-SCI N =

55,958

P Value Odds Ratio

(95%CI)

Age (mean, years) 66.5 68.8 0.007

Risk Factors (%) Hypertension Lipid disorder Diabetes mellitus Smoking history Smoking w/in past year

51.855.929.920.115.9

63.372.134.422.626.1

0.002<0.001

0.220.2

<0.001

1.4 (1.1-2.0)

2.0 (1.5-2.8)

1.1 (0.8-1.7)

1.3 (0.9-1.9)

2.4 (1.5-3.7)

Other variables assessed

SCI(N = 191)

Non-SCI (N =

56,951)

P Value

Prior Event (%) Myocardial infarction Heart failure Stroke Coronary angioplasty Coronary artery bypass surgery

19.824.28.69.19.1

21.320.46.115.820.2

0.410.220.160.010.002

Other variables Family history (high missing) Obesity (recorded diagnosis only) Depression

13.63.19.8

12.28.59.6

0.840.010.94

Diagnosis – MI type (%) Non-ST- Elevation MI (NSTEMI) ST- Elevation MI (STEMI)

83.314.1

83.214.8

N.S.N.S.

Within the SCI group: High complete vs. all other SCI

High-Complete N

= 19

Other SCI

N = 172

P Value

Age Hypertension Lipid disorder Diabetes mellitus Smoking history Smoking w/in past year

62.451.855.929.920.115.9

66.963.372.134.422.626.1

0.90.020.060.70.20.5

Study Limitations

Retrospective study, relies on accuracy and completeness of data (However, concern mitigated by use of trained abstractors)

Limited to male veterans; potential effect on

generalizability

Relatively small sample size of the SCI group (though large for an SCI cohort study)

Does not account for AMI that was completely missed so never entered in CCFCS

Conclusion: Primary Finding

Individuals with SCI were less likely to be identified as having several of the conventional risk factors for cardiovascular disease than the non-SCI cohort, despite developing AMI at a younger age

Potential Explanations

Factors other than the traditional risk factors may play a more prominent role in development of cardiovascular disease in people with SCI

Some aspects of risk may not be fully captured by conventional diagnostic criteria in the CCFCS database (e.g. peripheral insulin resistance vs. diabetes, isolated low HDL vs. “lipid disorder”, relative hyper-adiposity vs. obesity diagnosis)

Threshold for cardiovascular risk could be different in people with SCI for some traditional risk factors (e.g. hypertension)

Potential Implications

Our results support further study to examine the role of factors such as autonomic impairment, sepsis, and pro-inflammatory/ pro-thrombotic factors in the development of cardiovascular disease following SCI

Conventional risk factors for heart disease should be identified and treated in people with SCI according to current standards of care, while gathering evidence to guide possible adaptation of the standards for individuals with SCI.