Is It Dead or Alive

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Is It Dead or Alive?

• Eric J. Frischhertz, M.D.

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History of Present Illness

• 73 yo man with PMH of HTN, DM2, hyperlipidemia,
  and CAD presented on 5/12/04 with cc of fatigue
  and dyspnea.
• He was dxd with CAD by angiogram on 3/30/04 and
  was also found to have severe LV dysfxn at that
  time (LVEF 20).
• He did not have CP but did c/o decreased exercise
  tolerance.

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HPI (continued)

• He could walk about 2 blocks before fatigue
  limited his activity.
• He also reported LE swelling and orthopnea.
• He did not have PND.

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Medical History

• PMH HTN, hyperlipidemia, DM2, prostate cancer,
  CAD
• PSH umbilical hernia repair
• Meds zocor 40mg qd, asa 325mg qd, toprol xl 50mg
  qd, hyzaar 50/12.5mg qd, aldactone 25mg qd,
  glipizide 5mg qd, carnitine 330mg tid, prevacid
  15mg qd
• Allergies none

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Medical History (contin)

• Social Hx Tobaccosmoked 2ppd for 40 yrs but
  stopped 6 weeks ago no alcohol or illicit drug
  use.

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Physical Exam

• VS BP 147/67 HR 73 RR 16 T 97.6
• Alert and oriented x3
• Carotid pulses 2 bilat without bruits
• No Jugular venous distention
• Regular heart rhythm, normal s1/s2, Distant heart
  sounds

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Physical Exam

• Both lungs clear but had scant bilat end
  expiratory wheezing
• Abdomen non-tender with no organomegaly
• Skin dry, no edema, femoral pulses 2 bilat
  without bruits, DP/PT pulses 2 bilat

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Laboratory Data
11.1
19
139
104
266
8.6
121
34.1
4.2
26
0.9
Hb A1c 5.9 T Cholesterol 167 Triglycerides
73 HDL 41 LDL 107
BNP 394
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Laboratory Data

• 12-Lead EKGnsr, left axis deviation, incomplete
  LBBB, LVH, when compared to EKG from 3/24/04
  there was now T wave inversion in the lateral
  leads
• Chest X-rayno acute pulmonary process

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Results

• Cardiac Angiogram (3/30/04)
• Multivessel CAD.
• Severely reduced LVEF.
• Recommend CT surgery consult and optimization of
  medical management.

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Results

• Echocardiogram (5/7/04)
• LAE, LVE.
• AK of inferior, apical, anterior, and
  inferoseptal segments with severe HK of remaining
  segments.
• LVEF 15.
• Eccentric LVH
• Severe MR, mild TR.

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Management

• It was determined after these results that
  patient should undergo a viability study to
  determine if he would benefit from
  revascularization.

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Is It Dead or Alive?

• An Overview of Myocardial Viability Testing
  Stunned vs. Hibernating Myocardium

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Hibernating myocardium

• Concept was developed in the late 1970s based on
  2 observations
• That myocardial dysfunction present before bypass
  surgery often reversed after surgery.
• And that inotropic stimulation with epinephrine
  caused transient improvement in regional and
  global LV dysfunction in patients with CAD.

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Ventriculogram with Epinephrine
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• Diamond, et al. noted in 1978, ischemic
  noninfarcted myocardium can exist in a state of
  function hibernation.
• This later led to the proposal by Rahimtoola of
  hibernating myocardium.

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Why This Is Important
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Pathophysiology

• May result from repetitive myocardial stunning,
  which is different from hibernation in that it is
  caused by short term reduction in flow, a
  re-establishement of that flow, and subsequent LV
  dysfunction of limted duration.

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Support for Stunning as a Cause of Hibernation

• In animal studies, repetitive stunning led to
  persistent LV dysfunction despite return of
  normal blood flow.
• Gradual increase in coronary stenosis in animals
  causes tissue supplied by the stenotic vessel to
  increase uptake of fluorine-18 labeled
  deoxyglucose, a glucose analog, which is a
  characteristic of hibernating myocardium.

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Histopathologic Characteristics

• Loss of contractile proteins (sarcomeres) without
  loss of cell volume in a substantial number of
  cells.
• Glycogen-rich perinuclear zones adjacent to areas
  of numerous small mitochondria.
• Nuclear changes with heterochromatin distributed
  evenly over the nucleaplasm
• Substantial loss of sarcoplasmic reticulum.

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Evaluation and treatment

• Ventriculography
• Dobutamine Echocardiography
• Myocardial Perfusion Imaging (nulcear imaging
  with thallium, sestamibi, or PET)
• MRI

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Other Modalities

• Tissue Doppler Echocardiography (TDE)/strain rate
  imaging
• Electroanatomic mapping
• Myocardial contrast echocardiography

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Ventriculography

• Asses wall motion by ventriculography then
  dtermine if there is improvement with NTG (to
  improve blood flow) or positive inotropic
  stimulation
• Limited by subjective evaluation

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Dobutamint Stress Echo

• Evaluates the inotropic reserve
• Viable myocardium shows improved global and
  regional contractile function.
• An improved contractile response requires at
  least 50 viable myocytes in a given segment
• The predictive value of the test is best when
  there is a biphasic response, i.e., improved
  contractile function with low dose infusion and
  worsening function with high dose

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DSE continued

• This represents an initial recruitment of
  contractile reserve followed by inducement of
  ischemia
• Infusion with low dose dobutamine (2.5 to 5
  mcg/kg/min) and increase incrementally while
  obtaining echo images at each dose
• Sensitivity 84 (CI 82-86)
• Specificity 81 (CI 79-84)

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Nuclear Scan Thallium

• Thallium-201 is a potassium analog which can be
  detected by single photon emission computed
  tomography (SPECT)
• Uptake by myocardial cells depends on an active
  transport process requiring intact sarcolemmal
  membranes and adequate ATP stores
• Images are obtained at rest and 4 hours later
• In normal myocardium, intial uptake is high but
  decreases rapidly within hours

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Thallium continued

• In hibernating myocardium, initial uptake is low
  but increases over time due to thallium
  redistribution.
• Uptake of greater than 50 of that in the normal
  area is the best predictor of functional recovery
  after revascularization.

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Thallium Protocols

• In addition to the 4 hour protocol, there have
  been studies with reimaging at 24 hours and also
  with reinjection of a smaller dose of thallium
  prior to obtaining redistribution images
• Both protocols have better sensitivity that the
  intial protocol

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Technetium-99m Sestamibi

• Sestamibi is a lipphilic cationic compound. The
  uptake across myocardial mebmranes is passive and
  requires the presence of intact electrochemical
  membrane gradients
• There is limited redistribution after initial
  uptake which would appear to limit its usefulness
  in determining viability

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Sestamibi Continued

• However, multiple studies comparing sestaimibi
  with thallium have shown that sestamibi produces
  results similar to that of thallium
• This would indicate that the kinetics of
  sestamibi are more complex under low flow
  conditions than can be explained by a simple flow
  dependent model

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Positron Emission Tomography

• Ischemic cells use more glucose than normal.
• Flourine-18 labeled deoxyglucose differentiates
  normal, hibernating and necrotic myocardium

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Back to Our Patient

• He underwent thallium delayed imaging.
• Images were obtained at rest, 10 minutes post
  injection, and at 24 hours post injection.

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Findings

• 17 of the left ventricular myocardium, located
  in the inferior and the inferolateral wall,
  demonstrates viability by thallium scintigraphy.
  12 of the myocardium in the same region has no
  viability and represents scar.