Control/Tracking Number : 04-237-SCMR Activity
:Abstract Current Date/Time : 9/12/2003 3:59:30
Low Dose Dobutamine Stress 3D Tagged and First-Pass
Contrast-enhanced Magnetic Resonance Imaging for Regional Detection of Stunned
Izlem Izbudak, MD1, Walter G.
O'Dell, PhD2, Luciano Amado, MD1, Raymond C. Boston,
PhD3, Dara L. Kraitchman, VMD, PhD1.
1Radiology, Johns Hopkins University, Baltimore, MD, USA,
2Radiology, University of Rochester, Rochester, NY, USA,
3University of Pennsylvania, Kennett Square, PA, USA.
Introduction: The differentiation of reversibly injured, i.e.,
stunned, myocardium from irreversibly injured myocardium is important for
driving clinical therapy.
Purpose: A canine model of
transient ischemia was used to investigate the role of low dose dobutamine
stress (LDDS) tagged and perfusion MRI for the detection of stunned myocardium
and recovery at 1 week.
dogs underwent a 20 minute coronary artery balloon occlusion followed by
reperfusion to create myocardial stunning. Three-dimensional tagged MRI (fast,
breath-hold, segmented k-space, ECG-gated gradient echo acquisition) was
performed at rest and during 5 ug/kg/min dobutamine stress at one week before
(baseline), ~1hr after, and one week after transient ischemia (recovery) on a
1.5T MR scanner. Short-axis and rotating long-axis tagged images were obtained
spanning the left ventricle. The tag lines detection and tracking and 3D
circumferential strain in the midwall were calculated in 12 circumferential
segments at 8 anatomic levels using custom software. Myocardial tissue at risk
of stunning (S) was identified based on <0.1 ml/g/min microsphere blood
flow during occlusion and compared to remote (R) tissue. Early after
reperfusion, 248 S segments and 424 R segments were identified for statistical
analysis. A linear regression analysis of strain versus time yielded systolic
strain rate (SSR) comparing the same S and R segments at baseline and recovery.
First-pass CE MRI (saturation recovery fast gradient echo EPI hybrid sequence)
was performed in the 4-6 short-axis planes after a 0.05 mmol/kg iv bolus of
Gd-DTPA. TTC staining was performed
Results: TTC staining demonstrated 100%
viable myocardium at euthanasia. Signal intensity time curves of CE MRI were
similar between stunned (S) and non-stunned remote (R) tissue (P=NS). SSR was
reduced in stunned tissue in the first hours after ischemia relative to remote
at rest (-0.15 ± 0.12 S vs. -0.32 ± 0.10 R, P<0.05). LDDS in the first hours
of reperfusion showed improved function in stunned tissue (-0.30 ± 0.16 LDDS vs
-0.15 ± 0.12 rest, P<0.05) as well as remote ( -0.45 ± 0.23 LLDS vs 0.32 ±
0.10 rest, P<0.05 ). Moreover, S regions showed complete recovery of function
at 1 week at rest (-0.53 ± 0.23 S vs -0.44 ± 0.20 R, P=NS ). There was no
significant change in SSR at rest in R regions from baseline to reperfusion and
recovery. LDDS caused significant increase in SSR in all regions at each time
point of MR imaging.
Conclusion: LDDS MRI with 3D
myocardial tagging can non-invasively identify dysfunctional myocardium that can
be recruited, which is the hallmark of stunned tissue. CE-MRI did not
demonstrate any differences between stunned and non-stunned tissue. Thus, tagged
serial MRI exams may be sufficient to demonstrate stunned tissue and recovery at
Category (Complete): Experimental MRI
Additional Information (Complete):
: Oral or Poster
Return to SCMR SCMR Meetings Department 19 Mantua
Road Mt. Royal, NJ 08061