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RRP 11-013 – HSR&D Study

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RRP 11-013
Characterizing Veterans with SCI and Acute Coronary Syndrome
Sunil Sabharwal MD
VA Boston Healthcare System Brockton Campus, Brockton, MA
Brockton, MA
Funding Period: July 2011 - December 2012

BACKGROUND/RATIONALE:
Ischemic Heart Disease (IHD) is a leading cause of morbidity and mortality in people with spinal cord injury (SCI). With increasing life expectancy, prevalence of IHD is expected to continue to increase in this population. Acute myocardial infarction (AMI) is one of the most important manifestations of IHD. Factors unique to SCI (e.g. loss of sensation, autonomic nervous system impairment) could influence presenting symptoms of AMI. Furthermore, lack of typical presentation of AMI could delay diagnosis and impact management and outcomes in this group. Yet there has been no prior research to characterize presentation of AMI in people with SCI.

OBJECTIVE(S):
1) Characterize presenting symptoms of AMI in Veterans with SCI and compare them to those in the non-SCI Veteran population.
2) Examine the effect of neurological level and completeness of SCI on presenting symptoms of AMI.
3) Compare processes of care and outcomes of AMI between the SCI and non-SCI groups, and
4) Compare processes of care and outcomes of AMI between those with and without typical symptoms of AMI in the SCI group.

METHODS:
Study Design: Retrospective cohort study

Study population: Inclusion criteria: Veterans with and without SCI hospitalized with AMI at any Veterans Administration (VA) hospital between July 2003 and December 2010.
Exclusion criteria:
1. Patients transferred from other hospitals, since presenting symptom documentation would not be available in those cases.
2. Since females constituted less than 2% of the SCI group, they were excluded from the analyses.
3. Multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS)-related quadriplegia or paraplegia (since sensory and autonomic impairments in those groups are different from SCI).

Data Sources:
1. The VA Cardiac Care Follow-up Clinical Study (CCFCS) data repository: This 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 during the study period.
2. VA Spinal Cord Dysfunction (SCD) registry: 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.
3. Chart review of a subset of patients (100 each in the SCI and non-SCI groups) was done to identify range and distribution of unique presenting symptoms that are not captured as part of the CCFCS database.

Study variables:
1. Patient demographics and cardiovascular risk factors.
2. 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. The designated cutoff point between high and low SCI was T4 (based on physiology of cardiac sensory and autonomic innervation that could impact presenting symptoms).
3. Characteristics of AMI, i.e. with ST-elevation (STEMI) or non-ST elevation (NSTEMI)
4. Presenting symptoms of AMI: Presenting symptoms in CCFCS database designated as typical (chest pain; sub-sternal compression/crushing; chest pressure, tightness, heaviness, or aching; unexplained indigestion or epigastric pain; radiating pain to shoulders, neck, back, arm/s) or atypical (dyspnea; nausea and/or vomiting; diaphoresis).
5. AMI-related process of care measures: Time to electrocardiogram (EKG), Time to admission, Time to Cardiology involvement, Aspirin within 24 hours of admission
6. Outcomes: 30-day, 90-day, and 1-year mortality

Statistical methods:
Differences between the SCI and non-SCI groups and within the SCI group were assessed by Chi-square test for categorical variables, by analysis of variance (ANOVA) for continuous variables, and by logistic regression analysis for a mixture of categorical and continuous variables. Mortality (30 day, 90 day, and 1 year) was assessed by running proportional hazard models, where subjects either experienced an event (mortality) or were censored at 30, 90, or 365 days post-admission. All analyses were performed using SAS, version 9.1.

FINDINGS/RESULTS:
After accounting for age, veterans with SCI (n=191) had over twice the odds of presenting without typical symptoms of AMI compared to the non-SCI veteran population (n=55,958) (odds ratio 2.7; 95% confidence interval 2.0-3.7; p<.0001). Those with complete SCI above the T4 neurological level were 7 times more likely to present without typical symptoms of AMI (odds ratio 7.2; 95% confidence interval 2.9-17.9; p<.0001), and most commonly presented with dyspnea (55%).

There were significant differences in process of care measures between the SCI and non-SCI groups, and between those with and without typical symptoms of AMI within the SCI group. E.g. those with SCI were significantly less likely to receive aspirin within 24 hours of admission than the non-SCI group, and within the SCI group those without typical symptoms of AMI were 6 times less likely to receive aspirin within 24 hours than those who had typical symptoms.

30-day, 90-day, and 1-year mortality after AMI were all significantly higher in the SCI group than the non-SCI group (p<.0001). After adjusting for age, those with SCI were over twice as likely to die after AMI than the non-SCI group (Hazard Ratios of 30-day, 90-day, and 1-year mortality of 2.5, 2.5, and 2.2 respectively). Within the SCI group, those without typical symptoms of AMI were about 3 times more likely to die than those with typical symptoms (Hazard Ratios of 3.1, 3.0, and 2.8 for 30-day, 90-day, and 1-year mortality respectively). There was no significant association between mortality after AMI and the SCI group based on level and completeness of injury (i.e. hi-complete, high-incomplete, low-complete, and low-incomplete). Age at time of AMI was strongly associated with hazard of dying; for those in the SCI group each year increase in age increased the hazard of 30-day, 90-day, and 1-year mortality after AMI by 3.3%.

IMPACT:
We demonstrated that individuals with SCI, especially those with high complete injuries, are significantly less likely to develop typical symptoms of AMI. Lack of typical symptoms was associated with missed or delayed AMI-related process measures and with adverse outcomes. Our study has important implications for policy, delivery, and practice. It suggests the need to examine appropriate interventions (such as targeted patient, emergency personnel, and provider education) that could be implemented to facilitate timely recognition and management of AMI in this population

PUBLICATIONS:
None at this time.


DRA: Brain and Spinal Cord Injuries and Disorders, Cardiovascular Disease
DRE: none
Keywords: QUERI Implementation
MeSH Terms: none

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