Docstoc

MR Imaging of Acute Myocardial Infarction miocardial infarction

Document Sample
MR Imaging of Acute Myocardial Infarction miocardial infarction Powered By Docstoc
					                                                                                                                                                                                               531




                                                                    MR Imaging     of Acute Myocardial
                                                                    Infarction: Value of Gd-DTPA


                                                                                                                               ,             ...,


                            Albert de Roos1                            The potential         of gadolinium      (Gd)-DTPA           to improve      the detection       of acute     myocardial
                          Joost Doornbos1                           infarction by MR has been shown in experimental    canine studies. To determine     its value
                     Ernst E. van der Wall2                         in humans, we studied five patients 2-17 days after myocardlal    Infarction by using ECG-
                    Ad E. van Voorthuisen1                          gated MR before and after administration                   of 0.1 mmol/kg   Gd-DiVA.      One patient had a
                                                                    rupture of the interventricular             septum,     complicating    an acute inferior-wall        infarction.
                                                                    Spin-echo       images were obtained             before   and immediately     after injection      of Gd-DiVA
                                                                    and were repeated            every 10 mm for up to 40 mm. In four patients,                  intensity-vs-time
                                                                    curves revealed         increasing    signal intensity in the infarcted      area in the first 20 mm after
                                                                    injection    of gadolinium.      Contrast     between     normal and infarcted     myocardium        was great-
                                                                    est 20-30 mm after Gd-DiVA                injection. In one patient, increasing       signal intensity of the
                                                                    infarcted     myocardium        was observed        up to 40 mm after Gd-DTPA        injection. The precon-
                                                                    trast intensity ratio between infarcted              and normal myocardium       was 1.1 at echo time (TE)
                                                                    =   30 msec and was 1.4 at TE = 60 msec (p < 05). The postcontrast                        intensity ratio was
                                                                    1.6, which was not statistically            different   from the ratio at TE = 60 msec but which was
                                                                    significantly     higher than the ratio at TE = 30 msec (p < O1). Infarct definition                           was
                                                                    substantially         improved   on postcontrast               images.    The septal     rupture      was clearly        seen,
                                                                    and the infarcted   myocardium  surrounding    the septal rupture showed                                enhancement           on
                                                                    postcontrast   images.
                                                                       These results suggest that Gd-DTPA       can improve MR visualization                                and detection         of
                                                                    acute myocardlal    infarction.


                                                                       MR imaging           of the heart      can identify           and quantitate         acute myocardial      infarction
                                                                    noninvasively,          as shown     by experimental                canine studies         [1 ]. In humans, MR can
                                                                    be used to detect and localize acute myocardial                                 infarction      by showing    local wall
                                                                    thinning,   increased      signal intensity   in the infarcted                   area, and increased       flow signal
                                                                    in the ventricular      cavity [2-5].
                                                                        Prolongation      of Ti and T2 relaxation         times in the edematous     infarcted  zone
                                                                    occurs    consistently.       T2 prolongation      appears     to predominate and therefore    an
                                                                    increased        myocardial       signal is best appreciated                    on spin-echo         images       with    long
                                                                    echo    times     [4]. Sometimes,               however,        no contrast       between        infarcted     and normal
                                                                    myocardium      is observed. Furthermore,    subendocardial   increased signal intensity
                                                                    can be difficult to differentiate from flow-related   enhancement.     Other problems in
                                                                    diagnosing   rnyocardial      infarction     by MR are the occurrence    of an increased    rnyo-
                                                                    cardial signal, an increased           flow-related  signal, and myocardial    wall thinning    in
    Received    September     10, 1987; accepted     after
                                                                    asymptomatic      volunteers      [3].
revision November      2, 1987.
    ‘Department     of Diagnostic  Radiology, University               Gd-DTPA     is a clinically useful paramagnetic       contrast agent for MR [6]. In humans,
Hospital Leiden, Rijnsburgerweg          10, 2333 AA Lei-           it has been used primarily for the examination                of brain tumors. Because of its
den, the Netherlands.    Address     reprint    requests       to   favorable       pharmacokinetic          properties            and lack of adverse          reactions,         Gd-DTPA        is
A. de Roos.
                                                                    safe    for     use     in humans        [6].     Gd-DTPA           produces       significant       shortening          of Ti
    2 Department   of Cardiology,    University     Hospital
                                                                    relaxation      time of irreversibly            damaged          canine myocardium,              resulting     in increased
Leiden,   2333 AA Leiden,    the Netherlands.
                                                                    signal intensity  of the infarct relative to normal myocardium     [7, 8]. In this study, we
AJR 150:531-534,       March 1988
0361 -803x/88/1     503-0531
                                                                    evaluated    the use of Gd-DTPA        for detection of acute myocardial    infarction  in five
ct American    Roentgen    Ray Society                              patients.
532                                                                                                             DE ROOS               ET     AL.                                                              AJR:150,      March     1988



                                                                                                                                                                  Fig. 1.-A,            Precontrast           transaxial     MR image
                                                                                                                                                              throughleftventricle             in 49-year-old       man suffering     from
                                                                                                                                                              a 7-day-old myocardial              infarction.      Acute posterolateral
                                                                                                                                                              myocardlal        infarction cannot be identified.
                                                                                                                                                                  B, Postcontrast          image at same level made 20 mm
                                                                                                                                                              after Gd-DTPA            injection.       Enhancement         of infarcted
                                                                                                                                                              area improves detection                of infarct.
                                                                                                                                                                  C, Intensity-vs-time             curves       in same patient      show
                                                                                                                                                              maximal contrast between                  infarction     and two areas of
                                                                                                                                                              normal myocardium               20-30 mm after administration               of
                                                                                                                                                              Gd-DTPA.




         1.4


         1.3

 0
         1.2



 ‘a.     1.1




::
       0.8



       0.7

                                                                                                                      ---     -.   INFARCT
       0.6
                                                                                                                      _____NORMAL

                                                                                                                                   NORMAL
       0.5




                           0                        10                      20                     30                         40                   5#{176}
                                                                                                 TIME        AFTER     W4JECTION
 C


Subjects               and        Methods                                                                                             basis of experimental         data [7] and because                of time restrictions.            In
                                                                                                                                      the patient with acute inferior-wall    infarction    complicated   by septal
       Four men (38-60                    years     old) with acute              myocardial      infarction           were            ruptures,  short-axis    images were obtained         with single electronic
studied by ECG-gated MR within 1 week after the acute event. A                                                                        angulation  starting from the transverse      images.
fifth patient (a 61 -year-old man) who had a ventricular septal rupture                                                                   MR examinations      were performed    with a Philips 0.5-T Gyroscan
complicating    an acute inferior-wall infarction was studied 17 days                                                                 unit. The repetition  time was determined       by the heartbeat  interval by
after          the acute         event.     Diagnosis            of acute        myocardial       infarction           was            ECG triggering at every heartbeat. The trigger delay was 200 msec
based on history, ECG changes, and typical evolution of plasma                                                                        after the R wave of the ECG. Six 10-mm-thick slices with 1 -mm gaps
creatine kinase levels. The location of the infarct was confirmed by                                                                  were obtained in transaxial   planes with an echo-time    (TE) of 30 msec
both ECG and coronary angiography, which showed an occluded or                                                                        and four measurements.      In addition, a single-slice, four-echo   image
stenotic infarct-related   artery. In the first four patients, peak plasma                                                            (TE = 30, 60, 90, and 1 20 msec) was obtained through the largest
creatine kinase levels varied between 235 and 740 U/I (mean, 490 U/                                                                   diameter     of the left ventricle.      A matrix size of 256 x 128 was used
I). The fifth patient (with septal rupture) was first admitted 2 weeks                                                                for acquisition;   the images were displayed           with a 256 x 256 matrix.
after the acute event; therefore, maximal creatine kinase level was                                                                       All images were assessed          visually for the presence of signs indic-
not available.             Informed         consent            was obtained.         Spin-echo          images        were            ative of myocardial       infarction.    Signal intensities    were calculated    by
made            in axial       planes      before        and     after  0.1 mmol
                                                                         IV administration              of                            region-of-interest     analysis after visual inspection.         The operator-dc-
Gd-DTPA/kg.                 Images were obtained immediately after bolus injection                                                    fined regions of interest were 1 cm2. In order to account for instru-
of Gd-DTPA,                and repeat examinations were performed every 10 mm                                                         mental variations,     the myocardial       regions of interest were normalized
for up to 40 mm thereafter.                              This     40-mm      period      was     chosen              on the           to the intensity     of subcutaneous          axillary fat. Mean values of the
AJA:150,         March         1988                                                        ACUTE             MYOCARDIAL       INFARCTION                                                             533


    Fig. 2.-A,     Precontrast short-axis view through left
ventricle    In 61-year-old   man wIth 17-day-old   inferior-
wall Infarction complicated                        by septal rupture. Image
was obtained          adjacent     to ruptured septum.          Note local
wall thInnIng In septal region (arrow).
     B, Postcontrast        Image at same level. Note enhance-
ment of Infarcted             myocardlum          in inferior    wall and
septum       (arrow).      Small enhancIng           liver lesion    (high
signal     IntensIty      compatible        with hemangloma            was
seen at long-TR/TE              Images) Is also vIsIble.
     C, Postcontrast           short-axIs      view perpendicular         to
Interventricular        septum      obtained      by using single elec-
tronIc angulation.          Septal     rupture     Is clearly seen (ar-
row).
     D, Postcontrast         long-axis     view parallel to interven-
tricular septum.         Note enhancement             of Infarcted   myo-
cardlum surroundIng              septal rupture      (arrow).




measurements                    obtalned      by      two independent               observers          were    deter-     icant increase      over the precontrast      ratios with a TE of 30
mined          both     for     precontrast          images,  (TE           =   30 and      60     msec)      and   for   msec (p < .01). The difference           between     the intensity       ratio
postcontrast                  images.       The      ratio     of   the     myocardial           intensity     of   the   with a TE of 60 msec and the postcontrast            ratio did not reach
apparently infarcted myocardium to that of normal myocardium in the
                                                                                                                          statistical  significance.   In four patients,         intensity-vs-time
same image was measured. This intensity ratio is a measurement of
                                                                                                                          curves    showed      greatest    contrast     between      normal    and in-
the contrast between infarcted and normal tissue. Intensity-vs-time
                                                                                                                          farcted myocardium      at 20-30 mm after Gd-DTPA         administra-
curves         were      constructed              for infarcted       and       normal     myocardium.
    Differences               between        signal intensity values were analyzed with the                               tion (Fig. 1). In one patient, the contrast      was still increasing
Wilcoxon              rank       test.     A p value of less than .05 was considered                                      40 mm after Gd-DTPA       injection. MR clearly showed the septal
significant.                                                                                                              rupture as well as enhancement        of the infarcted   myocardium
                                                                                                                          surrounding    the defect (Fig. 2).
                                                                                                                             In the first 20-30     mm after gadolinium        injection,   an average
Results                                                                                                                   enhancement        of 40% (range, 1 5-80%)          for normal myocar-
    Short-TE     precontrast    images      showed                                       local wall thinning              dium was observed;         the infarcted    myocardium           showed     an
consistent     with myocardial    infarction    in one                                    patient. Multiecho              average    enhancement       of 90% (range, 50-i 60%). Improved
images      showed     an increased        wall signal                                      compatible    with            infarct definition   after Gd-DTPA     administration        was assessed
infarction    in four patients.    Delineation      of                                   the infarcted    area            by visual inspection       and by measuring          significantly     higher
was poor when a multiecho           technique      was                                    used because     the            contrast   ratios between      normal and infarcted         myocardium        in
signal-to-noise                    ratio was less than optimal.                             After        Gd-DTPA          all five patients.
injection,  the infarcted      areas were more visible in all five
patients,  improving    infarct definition   as compared    with defini-
                                                                                                                          Discussion
tion on precontrast     images (Fig. i). The average precontrast
intensity  ratio was 1.1 with a TE of 30 msec and 1.4 with a                                                                  The present study demonstrates            the potential of Gd-DTPA
TE of 60 msec (p < .05). The average             intensity ratio 20-30                                                    to improve detection   and definition        of acute myocardial     infarc-
mm after Gd-DTPA        administration     was 1.6; this was a signif-                                                    tion in humans.    A bolus injection         of 0.1 mmol/kg      Gd-DTPA
534                                                                             DE ROOS     ET AL.                                                                        AJR:150,      March     1988




induced          a marked     shortening     of Ti relaxation    time in the                count     for this increased-wall-signal                      artifact      [5]. Another          poten-
infarcted         area, thereby    enhancing    the signal intensity  of the                tial application            of Gd-DTPA               is the differentiation                   between
infarcted         myocardium.      Both visual inspection     and measure-                  reversible       and irreversible             myocardial           injury     [i ii.
ment of the signal intensity                    of the infarcted myocardium                    In conclusion,              Gd-DTPA-enhanced                          MR using           spin-echo
relative to normal myocardium                   showed improved infarct defi-               images        with     short       echo      times       improves           the     detection         and
nition      on    postcontrast       images.       These     results    are   in accor-     definition of acute myocardial infarction in humans and elimi-
dance with a recent study comparing Gd-DTPA                             enhancement         nates some confounding     factors that are related to multiecho
in different stages of myocardial infarction [9].                                           techniques.
    Maximal    contrast     between        normal and infarcted          myocar-
dium was seen 20-30              mm after Gd-DTPA            administration        in
                                                                                            ACKNOWLEDGMENT
four patients,     probably      because       of delayed     washout       of the
contrast     agent from the infarcted              zone as compared           with             We thank Schering                 AG (Berlin,         W. Germany)              for providing        Gd-
normal myocardium.                                                                          DTPA/dimeglumine               and Ineke Lek for her secretarial                    assistance.
    Our study also shows an average enhancement                      of 40% for
normal myocardium.           Enhancement           of normal myocardium            is
related to myocardial          blood flow and offers the potential                to        REFERENCES
detect hypoperfusion          distal to severe stenotic         coronary      arte-
                                                                                             1 . Caputo      GR, Sechtem U, Tscholakoff D, Higgins CB. Measurement of
ries as demonstrated          in experimental        studies [10].                               myocardial      infarct size at early and late time intervals                using MR imaging:
    Although    MR without the use of contrast              agents can detect                    an experimental        study in dogs. AJR 1987;149:237-243
and localize myocardial          infarction,     there are still notable limi-               2. McNamara          MT, Higgins CB, Schechtmann                     N, et al. Detection       and char-
tations. When no contrast             agent is used, spin-echo            images                 acterization      of acute myocardial              infarction       in man with use of gated
                                                                                                 magnetic     resonance.        Circulation      1985;71(4):717-724
with long echo times (multiecho              images) usually are acquired
                                                                                             3. Filipchuk NG, Peshock              RM, Malloy CR, et al. Detection             and localization        of
for improved           definition   of the infarct.        However,     these images             recent myocardial         infarction      by magnetic       resonance     imaging. Am J Cardiol
have a less-than-optimal                signal-to-noise        ratio as compared                 1986;58:214-219
with images that have               short echo times.          Another  advantage            4. Johnston      DL, Thompson              AC, Liu P. et al. Magnetic resonance imagina
                                                                                                 during acute myocardial             infarction.   Am J Cardiol 1986;57: 1059-1065
of the multislice,          single-echo        technique     is the potential       capa-    5. Fisher MR. McNamara                MT. Higgins CB. Acute myocardial                 infarction:     MR
bility of obtaining      images of the entire left ventricle with high                           evaluation    in 29 patients. AJR 1987;148:247-251
signal-to-noise      ratio. However,        the signal-to-noise  ratio of                    6. Carr FH, Brown J, Bydder GM, et al. Clinical use of intravenous                         gadolinium-
second-echo,        multislice    cardiac   images is poor because     of                        DTPA as a contrast agent in NMR imaging of cerebral                             tumours.       Lancet
                                                                                                 1984;2:484-486
cardiac movement.            Flow artifacts   are also more pronounced
                                                                                             7. Rehr RB, Peshock               AM, Malloy CR, et al. Improved                   in vivo magnetic
when the multiecho technique is used.                                                            resonance      imaging of acute myocardial                 infarction   after intravenous        para-
  The effect of Gd-DTPA administration                         is observed      to best          magnetic contrast agent administration.                    Am J Cardiol 1986;57:864-868
advantage           on images       with   short    echo     times.    Therefore,     the    8. Tscholakoff        D, Higgins CB, Sechtem               U, McNamara            MT. Occlusive        and
application         of Gd-DTPA        obviates       the use of multiecho           tech-         reperfused    myocardial     infarcts:    effect of Gd-DTPA     on ECG-gated        MR
                                                                                                  imaging. Radiology      1986;1 60:51 -519
niques and thereby     eliminates   some potential        pitfalls.   Fur-
                                                                                              9. Eichstaedt Hw, Felix A, Dougherty FC, Langer M, Rutsch W, Schmutzler
thermore,   Gd-DTPA    probably   can discriminate       between       the                        H. Magnetic resonance imaging in different stages of myocardial            infarction
areas of increased    wall signal caused      by infarction       and the                         using the contrast agent gadolinium-DTPA.           Clin Cardiol 1986;9:527-535
areas of increased    myocardial    signal observed         on the T2-                      1 0. Johnston     DL, Liu P, Lauffer          RB, et al. Use of gadolinium-DTPA         as a
weighted   images of asymptomatic         volunteers.     Areas of in-                            myocardial    perfusion   agent: potential applications and limitation for mag-
                                                                                                  netic resonance imaging. J NucI Med 1987;28:871-877
creased wall signal in asymptomatic       persons can occur in up                           1 1 . McNamara MT, Tscholakoff D, Revel D, et al. Differentiation of reversible
to 83% of the population       and are not well understood             [3].                       and irreversible myocardial       injury by MR imaging with and without gadolin-
Probably  respiratory   motion or cardiac wall motion can ac-                                     ium-DTPA.     Radiology    1986;1 58:765-769

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:6
posted:1/13/2011
language:English
pages:4