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DECEMBER 2013
ISSUE 57
Low-radiation Coronary CT Angiography without Beta-blockers in an Emergency
Department Patient with Reactive Airway Disease
Harshna Vadvala, MD, Andy Chan, MD, William Binder, MD, Neal Chatterjee, MD, Sanjeev Francis, MD, and
Brian Ghoshhajra, MD, MBA
Clinical History
A 44 year old male smoker with chronic obstructive
pulmonary disease (COPD) and hypertension presented
to the Emergency Department (ED), primarily because he
had recently run out of his home inhalers, but noting recent
progressive chest tightness and shortness of breath.
14 months prior, after complaining of similar symptoms,
he underwent elective exercise stress nuclear perfusion
imaging, achieving excellent exercise capacity (10 METS),
normal ECG response, normal myocardial perfusion with
gastric uptake artifact adjacent to the inferior wall, and a
preserved left ventricular ejection fraction (LVEF) of 58%.
In the emergency department, his vital signs were stable.
Initial serum biomarkers and ECG were negative for
ischemic changes, but confirmed sinus tachycardia at 125
beats per minute.
Figure 1
Figure 2
Figure 3A
Figure 3B
Findings
Retrospectively-ECG gated CCTA with functional
assessment was performed after the uneventful
administration of sublingual nitroglycerine and without
intravenous beta-blockade (due to ongoing COPD). Images
revealed a 7cm segment total occlusion of the dominant right
coronary artery, with distal reconstitution via collaterals.
There was mild hypokinesia of the basal to mid inferior wall,
with decreased left ventricular ejection fraction of 48%.
He was admitted for observation and serial biomarkers
and ECG exams excluded ongoing ischemia. A SPECT
myocardial perfusion imaging was performed, confirming a
new inferobasal scar, and a decreased LVEF of 50%. He
was discharged on maximal medical therapy.
Discussion
In patients with acute chest pain deemed at low to
intermediate risk of acute coronary syndrome, CCTA has
been shown by several randomized, controlled trials to be
efficacious and cost-effective, demonstrating high sensitivity
and high negative predictive value. (1) Several important
exclusions were applied to most early CCTA studies, chiefly
due to the need for strict heart rate and rhythm control when
using older-generation CT technology.
The present patient’s tachycardia would previously have
been considered a contraindication to CCTA, and was
compounded by his relative contraindication to rate control
with beta-blockers (i.e. active COPD). However, some
modern CT scanners have obviated the need for strict rate
control via such technologies as dual-source scanning,
and arrhythmia rejection algorithms. (2) Further, these
low-radiation dose techniques often allow acquisitions at
reasonable radiation exposures over a wide range of heart
rates yet obtain sufficient cardiac phases necessary for
functional assessment.
In the present case, CCTA enabled rapid diagnosis of
coronary artery disease, and showed that the extent of
disease was limited to a single vessel not readily amenable
to percutaneous intervention. The exam confirmed the
presence of ischemic cardiomyopathy via the corresponding
territorial resting left ventricular wall motion abnormality, a
finding known to complement the sensitivity of anatomic
stenosis assessment. (3)
Figure 1: Double-oblique long-axis maximum intensity projection (MIP) image of the right coronary artery demonstrates
a partially calcified plaque (white arrow) and a long segment, 7-centimeter occlusion of the RCA, with filling of the distal
vessel via collaterals. Low tube potential (100 kVp), retrospectively ECG-gated 128-detector-row dual-source CTA resulted
in a dose-length product of 224 milliGray-centimeters, corresponding to the equivalent of an effective radiation dose of 3.1
milliSieverts (including the non-contrast calcium scoring exam). The patient’s heart rate during scan acquisition was 89
beats per minute (range 86 to 92 beats per minute).
Figure 2: Multiphase assessment of the CTA dataset in the mid-ventricular short axis view of the left ventricle
demonstrates regional hypokinesis of the inferior wall. Calculated left ventricular ejection fraction was 48%.
Figure 3(A,B): Regadenoson stress (A) and rest (B) perfusion single-photon computed tomography myocardial perfusion
imaging (SPECT-MPI) demonstrates a new fixed inferior wall defect with adjacent gastric uptake artifact (white arrows), with
calculated left ventricular ejection fraction decreased to 50% currently versus 58% on the prior study 4 months prior (not
shown).
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Editors:
Brian Ghoshhajra, MD, MGH Department of Radiology
Sanjeev A. Francis, MD, MGH Division of Cardiology
Editor Emeritus:
Suhny Abbara, MD
Wilfred Mamuya, MD, PhD