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Myocardial Ischemia and Acute

VIEWS: 17 PAGES: 45

									       Complications of Acute M.I.



              Douglas Burtt, M.D.


Bio-Med 350
 Left Anterior Descending Occlusion
                    Occlusion of
                    the
                    left anterior
                    descending
                    coronary
                    artery




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                   Experimental Data
      Canine studies – transient artery
       clamping or ligation
      Balloon angioplasty studies
              Time dependent series of events
              Chest Pain as a late event




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                        ACUTE M.I.
               THE “ISCHEMIC CASCADE”
                               Diastolic dysfunction
 Chest pressure, etc.


                  Acute MI            Release of CPK



 Ischemic EKG changes
                           Localized systolic dysfunction



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                        ACUTE M.I.
                    THE “ISCHEMIC CASCADE”


              1.   Diastolic dysfunction
              2.   Localized systolic dysfunction
              3.   Ischemic EKG changes
              4.   Chest pressure, etc.
              5.   Release of CPK


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              Time course of cell death

       20 - 40 minutes to irreversible cell
        injury
       ~ 24 hours to coagulation necrosis
       5 - 7 days to “yellow softening”
       1 - 4 weeks: ventricular
        “remodeling”
       6 - 8 weeks: fibrosis completed


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              Think Anatomically!!
       Left main coronary artery supplies
        two-thirds of the myocardium
       LAD supplies ~ 40% of the L.V.,
        including apex, septum and anterior
        wall
       RCA supplies less L.V.
         myocardium, but all of
         the R.V. myocardium

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         Blood supply of the septum




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              Think Anatomically!!!
         LAD supplies most of the conduction
          system below the A-V node
              (i.e. the His-Purkinje system)
         RCA supplies most of the conduction
          system at or above the A-V node
              (i.e. the A-V node and, usually, the
                S-A node)




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              Conduction System of the
                       Heart




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          Conduction System: detail




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                   ACUTE M.I.
               Anatomical correlates
              LAD occlusion causes extensive
                infarction associated with:

                           LV failure
                     High grade heart block
                    Apical aneurysm formation
                  Thrombo-embolic complications

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                      ACUTE M.I.
                  Anatomical correlates
              RCA occlusion causes moderate
                infarction associated with:

                             RV failure
                         Bradyarrhythmias
                 Occasional mechanical complications


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                        ACUTE M.I.
                        Arrhythmias
                     Sinus bradycardia
                     Sinus tachycardia
                     Atrial fibrillation
               PVCs / ventricular tachycardia
                   /ventricular fibrillation
                        Heart block


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                    Arrhythmias:
                    Inferior M.I.
         Sinus bradycardia -- S.A. nodal artery
          and increased vagal tone
         Heart block -- A-V nodal artery
          1st degree A-V block
          Wenckebach 2nd degree A-V block
          A-V dissociation
         Atrial fibrillation -- L.A. stretch
         Ventricular tachycardia / fibrillation --
                 via “re-entry” or increased
                     automaticity
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                     Arrhythmias:
                     Anterior M.I.
       Sinus tachycardia -- low stroke
        volume
       Heart block -- His-Purkinje system
          Left or Right Bundle branch block
          Complete Heart Block
         Ventricular tachycardia /
          fibrillation
             due to “re-entry” or increased
              automaticity
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                  ACUTE M.I.
                  Hypotension

            Identify hemodynamic subset
              
        Distinguish decreased preload from
              decreased cardiac output
       Think about hemodynamic monitoring



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              Hemodynamic subsets
     Starling curves to
                                      6
      plot “preload”                  5
      versus cardiac        Cardiac   4

      output                Output
                                      3
                                      2
     Identification of               1
                                      0
      high risk subgroups
     Definition of                       L.V.E.D.P.
      cardiogenic shock


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                       3
                     2.5    1           3
            Cardiac    2
             Index
          (L/min/m2)
                     1.5
                       1    2           4
                     0.5
                       0

                           L.V.E.D.P.


                   Hemodynamic Subsets
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                    Acute M.I.
              Mechanical Complications
         Rupture of free wall      Tamponade

                        Pseudoaneurysm
       Rupture of papillary muscle


                      Acute Mitral regurgitation

         Rupture of intraventricular septum

                       Acute V.S.D.
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                     ACUTE M.I.
              Papillary Muscle Rupture
               Leading to Acute M.R.




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                     ACUTE M.I.
              Papillary Muscle Rupture
               Leading to Acute M.R.

                      Systolic murmur
               Giant V - waves on PC Wedge
                           tracing
                 Echo/Doppler confirmation
                RX with Afterload reduction
                 Intra-aortic balloon pump
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              “Flail” Mitral Leaflet




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 Echo/Color Doppler of Acute M.R.


                   LV




              RA        LA



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              Development of giant “V
                      waves”
              P. A. pressure   P.C. Wedge pressure
                                     V-wave




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        Acute Mitral Regurgitation:
               Treatment
       Rapid diagnosis
       Afterload reduction
       Inotropic support
       Intra-aortic balloon pump
       Surgical valve replacement




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                    ACUTE M.I.
              Acute Ventricular Septal
                      Defect
                           •Can occur with either
                           anterior or inferior MI
                           •Peak incidence on
                           days 3-7
                           •Causes an abrupt left-
                           to-right “shunt”



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                    ACUTE M.I.
              Acute Ventricular Septal
                      Defect
                           •Abrupt onset of a
                           harsh systolic murmur,
                           often with a “thrill”
                           •Detected by an
                           oxygen saturation
                           “step-up”



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       Oxygen saturation “step-up”
       IV C sat SV C sat RA sat RV sat PA sat

        70%     65%      68%    88%     88%




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                Acute V.S.D.:
                 Treatment
       Rapid diagnosis
       Afterload reduction
       Inotropic support
       Intra-aortic balloon pump
       Surgical repair of ruptured septum




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          Intra-Aortic Balloon Pump
             Augments coronary blood
              flow during diastole
             Decreases afterload
              during systole by
              deflating at the onset of
              systole
             Reduces myocardial
              ischemia by both
              mechanisms



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              Intra aortic balloon pump




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              Intra-aortic balloon pump




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                     Free Wall Rupture
             Cardiac                        Pseudoaneurysm
              Tamponade
                                             Enlarged cardiac
              Equalization of diastolic       silhouette
              pressures                      Echocardiographic
              Hypotension                     diagnosis

              J.V.D.

              Clear lung fields

              Pulsus paradoxus
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                ACUTE M.I.
              Apical Aneurysm
                         Associated with
                          large, transmural
                          antero-apical MI
                         Can lead to LV
                          apical thrombus
                         Is associated with
                          ventricular
                          arrhythmias


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                ACUTE M.I.
              Apical Aneurysm
                         Causes
                          “dyskinesis” of the
                          apex
                         Can be detected
                          by cardiac echo
                         Can lead to
                          systemic emboli
                         Anticoagulants
                          may prevent
                          embolization
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              Right Heart Failure
    Very commonly a              Cardiac causes
     sequela of Left                 Pulmonic valve stenosis
                                     RV infarction
     Heart Failure
                                  Parenchymal pulmonary
            LVEDP                 causes
            PCW                     COPD
            PA pressure             ILD

         Right heart pressure    Pulmonary vascular
          overload                 disease
                                     Pulmonary embolism
                                     Primary Pulmonary
                                      hypertension



Bio-Med 350
               ACUTE M.I.
       Right Ventricular Infarction

       Jugular venous distention with clear
                        lungs
       Equalization of right atrial and PCW
                      pressures
          ST elevation in right precordial
                        leads
                Therapy with fluids

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                       3
                     2.5    1           3
            Cardiac    2
             Index
          (L/min/m2)
                     1.5
                       1    2           4
                     0.5
                       0

                           L.V.E.D.P.


                   Hemodynamic Subsets
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                    ACUTE M.I.
                    Pericarditis


                 Pleuritic chest pain
           Radiation to the trapezius ridge
                         Fever
               Pericardial friction rub



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                  ACUTE M.I.
              CARDIOGENIC SHOCK

          Large area of myocardial necrosis
          Consider mechanical complications
           Exclude correctable causes --
            i.e. hypovolemia or R.V. infarct
         I.A.B.P.     C.A.B.G. OR P.T.C.A.


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                     Summary for RCA (or
                      circumflex) infarct

                                  Right coronary artery


    Right ventricular infarct       S-A nodal infarct       Postero-medial papillary
                                    A-V nodal infarct           muscle infarct


      Hypotension due to           Bradyarrhythmias         Acute mitral regurgitation
     decreased L.V. filling      1st degree A-V block            (with or without
                                Mobitz I 2nd degree block   papillary muscle rupture)
                                    A-V dissociation




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              Summary for LAD infarct
                                      Left anterior descending artery


                       40% of LV myocardium                                 His-Purkinje system

      Cardiogenic shock due
       loss of large amount of                                             Advanced Heart Block
      to
            myocardium                                                  (LBBB, 3rd degree A-V block
                                                                          and Mobitz II 2nd degree)

       Intraventricular septum              Antero-apical wall
          (upper two-thirds)



    Acute ventricular septal defect       Apical L.V. aneurysm


                                 Ventricular             Apical thrombus
                                 arrhythmias                formation


                                                        Arterial embolism
                                                      originating in the L.V.


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                        Summary
         Think                Think
          anatomically!!!       hemodynamic
                                subsets!!!

         LAD vs. RCA

                                Watch for
                                mechanical
                                complications

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              THE END




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