Getting it right the first time: Stress-only MPI in the ER
Received Feb
Getting it right the first time: Stress-only MPI in the ER
David G. Wolinsky 0
FACC 0
MASNC 0 1
0 Reprint requests: David G. Wolinsky, MD, FACC, MASNC , Heart and Vascular Institute, Cleveland Clinic Florida , Weston , USA
1 Heart and Vascular Institute, Cleveland Clinic Florida , Weston
Determining the optimal pathway for evaluating patients presenting to the emergency with chest pain remains an ongoing challenge. The 2011 National Hospital Ambulatory Medical Care Survey reported over seven million emergency room (ER) visits for evaluation of chest pain.1 Only a very small percentage of these patients actually have acute coronary syndrome (ACS)2 or severe coronary artery disease. Presenting symptoms, electrocardiogram changes, and initial biomarkers can usually identify the small group of patients with acute myocardial infarction (MI) or acute coronary syndromes (ACS). These patients are rapidly admitted and undergo coronary angiography if indicated. The larger portion of remaining patients is left to undergo diagnostic and prognostic evaluation. These evaluations are usually done in an observation unit or a dedicated chest pain unit with the goal to identify all patients who are at increased short-term risk (48 to 72 hours) of a cardiac event and refer them promptly for care. Additionally, these patients may be at risk for further downstream testing, recurrent hospitalization, or late cardiovascular event. The workup of these patients should minimize these long-term risks. In the present issue of the Journal of Nuclear Cardiology, Amirian et al analyze the utility of both exercise treadmill testing (ETT) and stress-only myocardial perfusion imaging (MPI) in assessing short- and long-term events in a lowrisk population.3 Their analysis sheds new light on better options to manage these patients under the pressure of
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new health care delivery models. Incorporating
stressonly imaging would assign specific decision-making
responsibility to the groups involved in the care of these
patients— ER physicians, hospitalists, and cardiologists.
By eliminating resting studies in the majority of patients,
the evaluation can be completed more quickly and
radiation exposure is reduced.
Historically, patients inappropriately discharged
from the emergency room with ACS have risk-adjusted
mortalities twice that of similar patients who are
hospitalized and treated.4 In fact, the overall risk in this
population is low, but few patients presenting to ER with
chest pain are discharged because of medical-legal
concerns. As a consequence, these patients undergo
exhaustive workups within a 24-48 hour span while
hospitalized. From 1999-2000 to 2007-2008, utilization
of advanced imaging for evaluation of chest pain
increased by 376%.2 Multiple clinical pathways have
been developed incorporating biomarkers, functional
testing, and noninvasive angiography, all of which have
high success rates.5 Although patients are no longer
admitted, direct costs remain high ($2226-$3168)
regardless of modality, driven to a great degree by
length of stay in the hospital.3 In order to reduce the
cost, the focus should be on three critical
factors—reduce the number of people requiring chest pain
pathways, reduce utilization of advanced imaging, or
decrease length of hospital stay.
There is a preponderance of data demonstrating that
patients with chest pain who do not have a myocardial
infarction are at low risk during short- and longer-term
follow-up. Foy et al demonstrated in a national sample
of over 650,000 patients that the incidence of MI was
very low—only 0.11% at 7 days and 0.33% at 190 days
of follow-up. The incidence of myocardial infarction
was not impacted by decision to pursue noninvasive
testing prior to discharge nor was the choice of testing a
factor.6 This analysis was based on insurance claims
data; therefore, there was a paucity of clinical data
available such as pre-test likelihood of disease.
Conclusions regarding the true value of testing such as
MPI are therefore limited.
Other authors have similar data demonstrating low
risk in this population. The Cleveland Clinic has
demonstrated that patients who ‘‘rule out’’ for an MI
have a low thirty-day event rate. In patients with TIMI
scores of 2 or less, stress MPI before discharge adds
little prognostic value. In patients with higher TIMI
scores, MPI was more likely to be ischemic and
coronary angiography was more likely to be carried out;
however, revascularization did not significantly improve
prognosis. Patients with normal MPI had low cardiac
event rates consistent with multiple studies
demonstrating excellent prognosis associated with a normal
MPI. A Singapore study incorporating SPECT MPI in
the ER showed that patients with normal or probably
normal (with return for resting images) stress-only MPI
were associated with a low 30-day event rate.
Incorporating MPI reduced the incidence of coronary
angiography significantly and patients with positive MPI
were more (...truncated)