Multiple risk assessment tools have been developed to help us identify low risk CP patients who are safe for discharge and can be followed up as outpatient. Some of these score systems have been validated and the basic idea is to quickly identify patients who are a very low risk for adverse events in a short period of time (usually 2 hrs) instead of the usual 8-12 hr protocols. A key concept to understand is that we do not rule out ACS in the ED, a patient with 90% stenosis can graduated from the department with 3 sets of negative cardiac markers and non-diagnostic EKG's. So we re-stratify patients to a level of risk that is acceptable (and defendable) that will guide further management.
It is not my intention to write a meta-analysis given the heterogeneity of these individual studies in their methodology, protocols and type of biomarker used. But here is a quick summary of some of the main studies evaluating accelerated re-stratification protocols (Rajeev... I hope this answers your question)
The Lancet. March 2011 (http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2811%2960310-3/fulltext) was a prospective validation study of 3582 patient in Australasia using a TIMI score of 0 (http://www.mdcalc.com/timi-risk-score-for-uanstemi/), non-ischemic EKG, negative biomarkers at 0 and 2 hr time. If all of those criteria were fulfilled, these patients were considered safe for discharge. Out of the initial pool of patients, 352 met criteria for discharge and only 3 had a cardiovascular negative outcome within 30 days defined as AMI, need for revascularization or death. This gives a 99.3% sensitivity, a 99.1% NPV and specificity of only 11%.
JAMA, December 2011 (http://www.ncbi.nlm.nih.gov/pubmed/22203537?access_num=22203537&link_type=MED&dopt=Abstract) Another prospective study, done in Germany with 1818 subjects. This study used only highly sensitive troponin I (no scores and no EKG's) at 0, 3 and 6 hrs. At 3 hr, repeat negative troponins had a sensitivity of 98.2% and PPV of 95.8% for ACS, with the 6 hr marker not adding significant extra benefit, making the point that 3 hr markers are as good as the 6 hr.
Clinical Pathways in Cardiology. March 2013. This is an European journal (http://journals.lww.com/critpathcardio/Abstract/2013/03000/HEART_Score_to_Further_Risk_Stratify_Patients_With.1.aspx) and the authors here put forward a new HEART score (http://www.heartscore.nl/score/) applied to patients with an already low TIMI score (0-1) to further identify very low risk patients who are safe for discharge from the ED. This included 8815 enrolled, from which 485 had both a TIMI of 0 and HEART score of 0. From this subset none had a negative cardiovascular outcome at 30 days for a sensitivity of 100%.
JAMA, Internal Medicine. October 2013. (http://archinte.jamanetwork.com/article.aspx?articleID=1748796) This is a randomized, parallel comparison study with blinded outcomes comparing a 2-hr accelerated diagnostic protocol (ADP) including TIMI of 0, non-ischemic EKG and negative biomarkers at 0 and 2 hr, vs standard care (initial negative biomarkers, prolonged observation usually with admission to hospital and second biomarker at 6-12 hr after onset of symptoms). The ADP had 270 pt of which 52 were discharge following the protocol and the standard care group had 272 pt and 30 discharges. At 30 days none of the discharged patients in both groups reported a negative cardiovascular event, making the conclusion that accelerated protocols are as effective and more efficient than standard prolonged observation protocol.
So, now what do we do with this information? Are these accelerated protocols ready for clinical use in the ED? Well... sort of. The good news is that these studies were done in the ED with general population cohorts and not cardiology centers, they have excellent results which can be applied to general practice. The bad news is that the AHA and ACC have not yet come on record with an official opinion about these protocols. However, as more and more patients show up through our doors with CP's the need for more efficient and cost-effective disposition has become imperative. But don't be the odd ball of your group and start doing this alone, take this information and talk to your medical directors and come up with an agreement on how to use these protocols in your departments.
A heart ATTACK !!!