On to the articles:
1) "Utility of Routine Testing for Patients With Asymptomatic Severe Blood Pressure Elevation in the Emergency Department," Karras, D, et. al. Annals of Emergency Medicine 51(3) March 2008
A prospective, observational study examining the benefit of standard recommended testing on asymptomatic patients with hypertension. The authors for this study include my mentor from residency, as well as our own current department chair and program director!
Design: A prospective, observational study of patients at three urban EDs with sustained blood pressures greater than or equal to 180 mmHg systolic or 110 mmHg diastolic. Any patient with symptoms which could even remotely be tied to their hypertension were excluded - the authors wanted truly asymptomatic patients. A panel of tests including basic metabolic panel, urinalysis, ECG, CBC count, and chest radiograph were obtained, though not every patient got every test. Treating physicians were then surveyed as to their reasons for performing the tests, and as to whether the results were "clinically meaningful." Clinically meaningful results were defined as those leading to unanticipated hospitalization, medication modification, or further immediate evaluation. The primary outcome was the prevalence of unanticipated clinically meaningful test abnormalities.
Results: 109 patients were enrolled (out of 409 screened). Approximately 50% of these patients had "unexpected" test results, though the article did not characterize these results. Only 7 (6%) had "clinically meaningful" abnormal test results, 2 of which were thought to be very unlikely to be related to the patients' blood pressure. The clinically meaningful outcomes were as follows:
click image to enlarge
Discussion points: We REALLY wanted this article to give us an answer as to how to work-up the patient with severe, but asymptomatic, hypertension. Unfortunately, the group felt that it fell short in this goal. While the authors calculated that they would need 300 patients to obtain adequate power, and that they would need to screen 400 patients for this, they were only ably to enroll 109 subjects. While this low number was likely due to their rigorous definition of "asymptomatic" it lead to a much smaller study than anticipated. This small size may have limited the applicability of the results. Also, 1 in 20 patients was found to have an abnormality requiring alteration in management, with no easily identifiable way to recognize them up front (eg, there was no correlation with underlying cardio- or renal-vascular disease). It was discussed that given the nature of the population studied (largely medically under served) these abnormalities might represent "baseline noise" rather than consequences of hypertension. In other words, if we were to screen every patient with theses tests, we would likely find a not insignificant number with similar abnormalities.
Overall, this article will not change any of our practice. Most faculty agreed that there is a blood pressure cut-off, above which they will screen for end-organ damage, but there was no consensus as to what tests to order. This magic number seemed to be about 180-200/110-120 for most people, but a very few voiced the opinion that in truly asymptomatic patients, they would do nothing. Generally, it was felt that these patients should have their renal function checked, but this still remains controversial.
2) "The Diagnostic Accuracy of 64-Slice Computed Tomography Coronary Angiography Compared With Stress Nuclear Imaging in Emergency Department Low-Risk Chest Pain Patients," Gallagher, M,. et. al. Annals of EMergencncy Medicine, 2006.
Yet another study with an Emory author, this article compared standard stress tests to CT angiography for low-risk chest pain patients in an ED observation unit.
Design: Prospective study of patients with chest pain felt to be low-risk by the Reilly/Goldman criteria who had negative serial ECGs and cardiac markers. The goal was to identify significant coronary artery disease (> 70% stenosis) or adverse cardiac event within 30-days of evaluation. Patients recieved both nuclear sestamibi stress testing and CT coronary angiography. Abnormal stress results (perfusion defects) or CT results (> 50% stenosis or calcium scopre > 100) were considered for cardiac catheterization, and all patients had 30-day follow-up for adverse cardiac events. Primary outcomes were the accuracy of multidetector CT and myocardial perfusion imaging for the detection of an acute coronary syndrome and 30-day major adverse cardiac events (defined as an acute coronary syndrome, [STEMI, non-STEMI, or unstable angina], the development of new Q waves on subsequent ECGs, new congestive heart failure or cardiogenic shock, major dysrhythmias (high-grade atrioventricular block, ventricular tachycardia, ventricular fibrillation), cardiac arrest, or death from an acute coronary syndrome.)
Results: 96 patients were enrolled who met the following enrollment criteria:
- no ECG evidence of acute infarction or ischemia (including new left bundle branch block)
- no pain that was worse than usual angina or like a previous myocardial infarction
- no recent revascularization
- no rales above both bases
- systolic blood pressure that was greater than 110 mm Hg
- negative initial chest radiograph
- negative initial set of cardiac markers (CK-MB and troponin I)
Of these patients, 4 were later excluded to to protocol violations, and 7 had uninterpretable CT results due to poor image quality. 85 patients were included in the study, 7 (8%) of whom were identified to have significant coronary disease, but none of whom had an MI or adverse cardiac event on 30-day follow-up. The investigators were able to perform 30-day follow-up on 83 of the enrolled patients,
The statistical calculations in this paper were complex, and I am not going to reproduce the number here. Generally, CTA had a higher sensitivity, specificity, and predictive value than stress testing, though 13 (15%) of patient had discordant results. 5 of these received a cardiac catheterization, 3 with significant stenosis. None of the other 8 (all with positive CTA and negative stress tests) had a major cardiac adverse event in the 30 day period.
Discussion points: This was a very complex paper which was chosen to spark conversation as to the role of CT coronary angiography in the ED.
The biggest flaw in the paper is the number of patients with the "target condition": 7! It is very difficult to conclusively evaluate any test when only 7 patients actually have the disease being studied. When you apply a test to a population with such a low disease prevalence you are very unlikely to get meaningful results. The group felt that there might in fact be a role for CTA in the future, but that more literature was necessary.
1) Calcium scoring is a measure of calcification of the coronary vessels on CT scan, thought to be a surrogate measure of coronary artery disease. This is only useful in older patients, as young people typically have non-calcified CAD.
2) The size of a coronary lesion does NOT predict its propensity for rupture with thrombus formation, and therefore is not indicative of the likelihood for causing acute MI. More important is the stability of the plaque, determined by the amount of lipid core versus fibrous cap. The thinner the cap, the more unstable, and the higher likelihood of rupture. No current risk stratification tool, including cardiac catheterization, can identify this. Experimental procedures including intra-coronary ultrasound may provide this information, but we are not there yet.
Overall, we are unsure as to the role of coronary CTA in the ED. This controversial topic will likely get a lot more study, and hopefully a reasonable role will be found.