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Am Fam Physician. 2008;78(10):online-only-

Background: High-risk patients with non-STsegment elevation acute coronary syndromeshave better outcomes if they receive early cardiaccatheterization rather than more conservativemanagement. Despite evidence-basedguidelines supporting this approach, the useof cardiac catheterization is still suboptimal.Geographic differences, hospital attributes,and patient risk levels and comorbidities maycontribute to this difference, but the specificreasons for this divergence between recommendationsand practice remain unclear. Leeand colleagues examined why some patientswere not referred for early treatment.

The Study: The Canadian Acute CoronarySyndromes Registry II is a prospective observationalstudy investigating clinical characteristics,management, and outcomes ofadult patients hospitalized for non-ST segmentelevation myocardial infarction andunstable angina. To minimize selection bias,no formal exclusion criteria were used. Eachpatient’s managing physician was asked toclinically determine the initial risk level, whether evidence- or guideline-based therapyhad been undertaken, and, when applicable,the main reason why these therapies had notbeen used. The patient’s objective risk statuswas then calculated using the Thrombolysisin Myocardial Infarction (TIMI) risk score,which is a composite score that uses sevenpredictor variables (see accompanying table).The patients were then divided into low-,medium-, and high-risk categories (TIMIrisk score of 0 to 2, 3 to 4, and 5 to 7, respectively).Data on clinical outcomes, cardiacprocedures, and medications used were collectedone year after initial hospitalizationand analyzed for outcome analysis.

Age 65 years or older
At least three risk factors for coronary arterydisease*
Prior coronary stenosis of 50 percent or more
Elevated serum cardiac markers
ST-segment deviation on electrocardiography
At least two episodes of severe angina inpreceding 24 hours
Aspirin use within preceding seven days

Results: A total of 2,136 patients at 36 hospitalswere included, of which 1,382 werereferred for cardiac catheterization. Most ofthe managing physicians were cardiologists(73.7 percent), with the remainder beinginternists, family physicians, general practitioners,and emergency department physicians.Patients receiving catheterization hadsignificantly lower TIMI risk scores (mean2.99) compared with those that did notreceive catheterization (mean 3.11). No significantdifferences in catheterization ratesor time to catheterization were seen based onpatient risk level. Overall, catheterization wasrecommended more often by cardiologiststhan noncardiologists (77.0 and 67.6 percent,respectively), and it was more often recommendedin hospitals with on-site catheterizationfacilities than in those without (75.6 and58.6 percent, respectively).

Of patients who were not catheterized, themost common reason (68.4 percent) was thatthe patient was not considered to be highrisk, or that their clinical status did not justifyan early invasive strategy. Cardiologistsand noncardiologists were equally likely tonot refer patients because of perceived lowerrisk. However, 59.1 percent of patients notreferred for catheterization were actually atintermediate or high risk according to theirTIMI risk score. Differences were foundin baseline characteristics of patients whowere not referred for cardiac catheterizationbecause of perceived lower risk comparedwith those who were referred. These differencesincluded older age; more women; morecongestive 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 withinitial TIMI risk level (2.7, 7.1, and 15.7 percentfor low-, intermediate-, and high-risk,respectively).

Overall, patients who received catheterizationhad significantly lower in-hospitaland one-year mortality rates (0.8 and4.0 percent, respectively) compared withthose who did not receive catheterization(3.7 and 10.9 percent, respectively). Whenanalysis was restricted to patients withhigher TIMI risk scores (3 to 7), patientswho received catheterization during theindex hospitalization had lower in-hospitaland one-year mortality rates (1.0 and5.6 percent, respectively) than those whodid not (4.8 and 14.3 percent, respectively).Patients with higher TIMI risk scores whodid not receive catheterization because ofperceived low-risk had significantly greaterone-year mortality rates than those whoreceived catheterization (9.1 versus 5.6 percent,respectively).

Conclusion: The authors conclude that earlycardiac catheterization is underutilized in patients with non-ST segment elevation acutecoronary syndromes, possibly because physicianperception of patient risk does not necessarilycorrelate with actual risk. Of patientsnot referred for catheterization because ofthe managing physician’s perception thatthe patient was low-risk, nearly 60 percentwere intermediate- or high-risk based ontheir TIMI risk scores, and these patients hadsignificantly greater mortality rates one yearafter hospitalization. Improved risk stratificationcould significantly benefit higher-riskpatients.

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