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Cardiac Catheterization in Patients with Acute Coronary Syndrome
Am Fam Physician. 2008 Nov 15;78(10) Online.
Background: High-risk patients with non-ST segment elevation acute coronary syndromes have better outcomes if they receive early cardiac catheterization rather than more conservative management. Despite evidence-based guidelines supporting this approach, the use of cardiac catheterization is still suboptimal. Geographic differences, hospital attributes, and patient risk levels and comorbidities may contribute to this difference, but the specific reasons for this divergence between recommendations and practice remain unclear. Lee and colleagues examined why some patients were not referred for early treatment.
The Study: The Canadian Acute Coronary Syndromes Registry II is a prospective observational study investigating clinical characteristics, management, and outcomes of adult patients hospitalized for non-ST segment elevation myocardial infarction and unstable angina. To minimize selection bias, no formal exclusion criteria were used. Each patient’s managing physician was asked to clinically determine the initial risk level, whether evidence- or guideline-based therapy had been undertaken, and, when applicable, the main reason why these therapies had not been used. The patient’s objective risk status was then calculated using the Thrombolysis in Myocardial Infarction (TIMI) risk score, which is a composite score that uses seven predictor variables (see accompanying table). The patients were then divided into low-, medium-, and high-risk categories (TIMI risk score of 0 to 2, 3 to 4, and 5 to 7, respectively). Data on clinical outcomes, cardiac procedures, and medications used were collected one year after initial hospitalization and analyzed for outcome analysis.
Table. Thrombolysis in Myocardial Infarction Risk Factors for Unstable Angina or ST Elevation Myocardial Infarction
Thrombolysis in Myocardial Infarction Risk Factors for Unstable Angina or ST Elevation Myocardial Infarction
Age 65 years or older
At least three risk factors for coronary artery disease*
Prior coronary stenosis of 50 percent or more
Elevated serum cardiac markers
ST-segment deviation on electrocardiography
At least two episodes of severe angina in preceding 24 hours
Aspirin use within preceding seven days
NOTE: All factors are equally weighted.
*—Risk factors include family history of coronary artery disease, hypertension, hyperlipidemia, diabetes, or current smoking.
Results: A total of 2,136 patients at 36 hospitals were included, of which 1,382 were referred for cardiac catheterization. Most of the managing physicians were cardiologists (73.7 percent), with the remainder being internists, family physicians, general practitioners, and emergency department physicians. Patients receiving catheterization had significantly lower TIMI risk scores (mean 2.99) compared with those that did not receive catheterization (mean 3.11). No significant differences in catheterization rates or time to catheterization were seen based on patient risk level. Overall, catheterization was recommended more often by cardiologists than noncardiologists (77.0 and 67.6 percent, respectively), and it was more often recommended in hospitals with on-site catheterization facilities than in those without (75.6 and 58.6 percent, respectively).
Of patients who were not catheterized, the most common reason (68.4 percent) was that the patient was not considered to be high risk, or that their clinical status did not justify an early invasive strategy. Cardiologists and noncardiologists were equally likely to not refer patients because of perceived lower risk. However, 59.1 percent of patients not referred for catheterization were actually at intermediate or high risk according to their TIMI risk score. Differences were found in baseline characteristics of patients who were not referred for cardiac catheterization because of perceived lower risk compared with those who were referred. These differences included older age; more women; more congestive heart failure, coronary artery bypass grafts, strokes, or ischemic attacks; worse Killip class status at presentation; lower incidence of ST-segment depression; and positive cardiac marker status.
Of the 2,094 patients discharged alive, 1,834 (87.6 percent) were alive after one year, and 121 (5.8 percent) were lost to follow-up. One-year mortality rates correlated with initial TIMI risk level (2.7, 7.1, and 15.7 percent for low-, intermediate-, and high-risk, respectively).
Overall, patients who received catheterization had significantly lower in-hospital and one-year mortality rates (0.8 and 4.0 percent, respectively) compared with those who did not receive catheterization (3.7 and 10.9 percent, respectively). When analysis was restricted to patients with higher TIMI risk scores (3 to 7), patients who received catheterization during the index hospitalization had lower in-hospital and one-year mortality rates (1.0 and 5.6 percent, respectively) than those who did not (4.8 and 14.3 percent, respectively). Patients with higher TIMI risk scores who did not receive catheterization because of perceived low-risk had significantly greater one-year mortality rates than those who received catheterization (9.1 versus 5.6 percent, respectively).
Conclusion: The authors conclude that early cardiac catheterization is underutilized in patients with non-ST segment elevation acute coronary syndromes, possibly because physician perception of patient risk does not necessarily correlate with actual risk. Of patients not referred for catheterization because of the managing physician’s perception that the patient was low-risk, nearly 60 percent were intermediate- or high-risk based on their TIMI risk scores, and these patients had significantly greater mortality rates one year after hospitalization. Improved risk stratification could significantly benefit higher-risk patients.
Lee CH, et al. Use of cardiac catheterization for non–ST-segment elevation acute coronary syndromes according to initial risk. Arch Intern Med. February 11, 2008:168(3):291-296.
Copyright © 2008 by the American Academy of Family Physicians.
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