Nathan.qxp 29/7/08 10:04 Page 16
Acute Coronary Syndromes
Bridging the Gap Between Scientific Evidence and Clinical Practice in the
Management of Non-ST-segment Elevation Acute Coronary Syndromes
a report by
Sandeep Nathan, MD and Rajiv Swamy, MD
Section of Cardiology, University of Chicago Medical Center
The spectrum of acute coronary syndromes (ACS) encompasses a broad proportion of ACS patients overall, suffer equal or higher rates of one-
array of clinical characteristics and risk strata, ranging from unstable year mortality than STEMI patients underscores the need for further
angina (UA) and non-ST-segment elevation myocardial infarction clarification and continued progress in this area of cardiovascular
(NSTEMI) to ST-segment elevation myocardial infarction (STEMI) and medicine.
1,2
Revised practice guidelines published by the American
sudden cardiac death (SCD). In this article, UA and NSTEMI will be College of Cardiology and the American Heart Association (ACC/AHA)
considered together as non-ST-segment elevation acute coronary and the European Society of Cardiology (ESC) have helped to distill the
syndromes (NSTE-ACS), reflecting the similarity in the pathogenesis and enormous body of scientific data regarding ACS into organized
management of these entities. recommendations suitable for implementation by the practicing
clinician.
3,4
Quality improvement initiatives have facilitated the
Despite the significant advances that have been made in diagnostic benchmarking of ACS care at both institutional and national levels and
technologies, the availability of newer therapeutic agents, and greater these measures, along with a greater adoption of evidence-based
access to invasive therapies, as well as the burgeoning body of clinical strategies and increased clinician awareness, have vastly improved
trial and registry data linking specific treatment paradigms with improved patient outcomes.
5
The goal of this review is to provide the clinician with
clinical outcomes, many challenges remain in the management of NSTE- a succinct and up-to-date perspective on the evidence-based acute
ACS. The dynamic nature of ACS presentation often confounds accurate pharmacological treatment of NSTE-ACS, which has become a complex
risk stratification, with a resultant impact on early use of proven and often confusing endeavor.
therapies. Hospital-specific resource limitations and uncertainties arising
from the timing and use of invasive cardiac diagnostics and Pathophysiology of Acute Coronary Syndromes
revascularization also often complicate management. The consistent The contemporary model of ACS pathophysiology implicates several
observation that patients with NSTE-ACS, who make up the greatest contributing factors, including acute and chronic vascular alterations,
plaque growth, activation of the platelet and coagulation cascades, and
inflammation (local and systemic).
6
The term ‘atherothrombosis’ is often
Sandeep Nathan, MD, is an Assistant Professor of Medicine at
used to describe these and related systemic processes occurring in any of
the University of Chicago Pritzker School of Medicine and an
interventional cardiologist at the University of Chicago Medical
a number of diseased arterial beds, most often the coronary, cerebral,
Center. He is a Fellow of the American College of Cardiology and peripheral vasculature. Rupture or erosion of a thin-capped coronary
(ACC) and the Society of Cardiovascular Angiography and
plaque serves as the initiating factor for most ACS events. Resultant
Interventions (SCAI). He currently serves as an Investigator
for a number of industry and National Institutes of Health
exposure of thrombogenic plaque contents and bound tissue factor to
(NIH)-sponsored studies and registries. He has co-authored the circulating blood pool activates the coagulation cascade.
7
Activated
numerous abstracts, original scientific manuscripts, and textbook
platelets that adhere to the site of vascular injury occupy a central
chapters in the areas of acute coronary syndromes, platelet inhibition, percutaneous coronary
intervention, and cardiogenic shock. Dr Nathan received his undergraduate and medical degrees
pathogenetic role in that they participate in both early and late thrombin
from Boston University and completed his internal medicine residency training at the University of generation, promote the efficient assembly of coagulation factors, and
Pittsburgh Medical Center. He completed his fellowship in cardiovascular medicine at Rush
aggregate via interactions between activated platelet surface
University Medical Center, where he also served as Chief Cardiology Fellow and subsequently
received training in cardiovascular and peripheral vascular intervention.
glycoprotein (GP) IIb/IIIa receptors and soluble fibrinogen to form a
platelet-rich thrombus.
8,9
The binding of fibrin, trapping of cellular
E: snathan@medicine.bsd.uchicago.edu
material, and formation of a mature, occlusive thrombus represent
Rajiv Swamy, MD, is a Fellow in the Section of Cardiovascular relatively late events in the atherothrombotic process. The presence of
Medicine at the University of Chicago Medical Center. He is a
collateral coronary flow, the counterbalancing effects of endogeneous
member of the American College of Cardiology (ACC). His
research interests are focused on the area of pharmacoinvasive
thrombolytic mechanisms, and ultimately the degree of coronary luminal
strategies for the management of acute coronary syndromes. Dr compromise largely determine the nature of the clinical presentation.
Swamy completed his undergraduate training at Duke University
Transient reductions in coronary blood flow often manifest as UA,
and earned his medical degree from the University of Chicago
Pritzker School of Medicine. He completed his internal medicine
whereas more prolonged flow reduction and macro- or microvascular
residency training at the University of Chicago Medical Center, embolization may result in myocardial necrosis and NSTEMI presentation.
where he also served as Chief Medical Resident.
It is now recognized that simultaneous activation of multiple coronary
plaques and/or polyvascular disease occurs in a significant proportion of
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