Transplant Flashcards
Class I Human Leukocyte Antigens (HLA)
- HLA-A
- HLA-B
- HLA-C
Expressed on all cells types
ID cells as “self”
Class II Human Leukocyte Antigens (HLA)
- HLA-DR
- HLA-DRw
- HLA-DQ
- HLA-DP
Expressed on APCs
Mechanisms of Hyper-Acute Rejection
-
IgM antibodies to donor HLA antigens
- blood group mismatching
-
IgG antibodies to donor HLA antigens
- Acquired from previous transfusions (especially multidonor platelets)
- Previous pregnancy
- Previous transplant
Direct vs. In-direct Antigen Presentation
Direct Antigen Presentation
Donor cell presentation of donor antigen
In-direct Antigen Presentation
Donor antigens presented by host APC
Signal 1 Pathway of T-cell Activation
Signal 1 Pathway (direct T-cell activation)
-
Direct antigen presentation by donor (passenger) APCs
- CD8+ T-cell activation
- Early CMR
-
In-direct antigen presentation by host APCs
- CD4+ T-cell activation
- Later AMR
Signal 2 Pathway of T-cell Activation
Signal 2 Pathway (T-cell Co-stimulation)
- Augmented T-cell activation via co-stimulatory receptors that recognize APC or donor cell antigens
- T-cell augmentation of B-cell activation
Cell Mediated Rejection Mechanisms
T-cell Mediated
-
Direct Effector Pathway
- Activation of CD8+ T-cells
- Cytotoxic T-cells induce apoptosis of graft cells bearing the HLA of their activating APC
-
In-direct Effector Pathway
- Activation of CD4+ T-cells
- Release of cyotkines that increase cytotoxic CD8+ T-cell mediated apoptosis
B-cell Mediated
APC activated CD4+ T-helper cells activate B-cells to produce antibodies that
- Destroy donor endothelial cells
- Induce Antibody-Dependant Cytotoxicity
- Activate the Classical Complement Pathway
ISHLT Criteria for Antibody Mediated Rejection
- Clinical evidence of donor-specific antibodies in the recipient
- Endomyocardial Bx evidence of immunopathologic complement (C4d and C3d) staining
- Endomyocardial Bx evidence of endothelial cell and macrophage activation (CD68 staining positive)
Can be assoc. with HLA or non-HLA antibodies
Usually occurs early (weeks-months)
Histologic Criteria for the Dx of AMR
- Endothelial swelling
- Activated macrophages in the graft
- Immunoglobulin (IgG or IgM) staining positive
Clinical Presentation of AMR
- Decreased LVEF (>25% reduction)
- Increased LV Mass
- Decreased R-wave Voltage
- New RBBB or LBBB
What is Desensitization Therpay and when is it Indicated?
- IVIG
- Plasmaphoresis
- Rituximab (anti-CD20)
- Cyclophosphamide
Indicated pretransplant if calculated PRA predicts <50% chance of donor match
Maintenance Immunosuppression
- Tacrolimus
- MMF
- Prednisone
Treatment of Acute AMR
- IVIG
- Rituximab (anti-CD20)
- Alemtuzumab (anti-CD52)
- Plasmaphoresis
- Thymoglobulin
- Other
- Belatacept (CTLA4-Ig)
- Bortezomib (proteozome inhibitor)
- Eculizimab (anti-C5i complement inhibitor)
Chronic Allograft Vasculopathy (CAV) and Treatment
Definition
Diffuse (epicardial and small vessel) arterial wall thickening and stenosis
- Stage O - Not significant
- Stage 1 - Mild
- Stage 2 - Severe
- Stage 3 - Severe with Graft Dysfunction
Treatment
- Sirolimus (mammalian target of rapomycin (mTOR) inhibitor)
- Statins
Outcomes
Accounts for 45% of SCD
Mortality 25% at 5-years; 50% at 10-years
Central vs. Peripheral Tolerance
Central Tolerance
Deletion of “self”-reactive T-cells in the thymus
Peripheral Tolerance
- Deletion (T-cell apoptosis)
- Anergy/Ignorance (induced functional nonresponsiveness; no co-stimulation)
- Regulation (active alloimmunity via CD4+ Tregs)
CDC Screening Assay
Recipient serum mixed with cells expressing known HLA antigens and complement
Disadvantages
- Dependent on the affinity of the antibodies present (countered by preheating serum to inactivate IgM or add humanglobluin (CDC-AHG assay) to increase sensitivity of low titer IgGs)
- Clouded by other serum proteins
- Not all antibody isotypes bind complement
- Does not determine titer
Panel Reactive Antibody (PRA) Screening Test
Recipient serum is exposed to panel of cells expressing known HLA antigents. PRA “titer” represents the percentage of the donor pool that would be killed by the patients serum.
PRA > 10% or > 25% have incrementally poorer outcomes
Poor for low titer antibodies or MCH class II antibodies
Risk Factors for High PRA
- Pregnancy (multiparity)
- Multiple Blood Product Transfusions
- MCS
- Congenital Heart Disease
- Previous Transplant
Solid Phase Flow Cytometry (SPA)
Reactivity to HLA antigens characterized by mean fluorescence intensity
Advantages
- Provides titer
- Provides individual donor-recipient compatibility
Virtual Crossmatch
Comparison of donor HLA genotype and recipient SPA antibodies
PPV 80%
True cross-match confirmed by CDC-AHG assay
Glucocorticoids
MOA
Inhibition of intracellular NF-kB
- decreases proinflammatory Th1 cytokines
- increases antinflammatory Th2 IL-10
Purine Analogs
MOA
Incorporates into DNA/RNA disrupting cell cycling
Azathioprine (Imuran)
SE - bone marrow susppression
Mycophenolate Mofetil (mmF/Cellcept)
More specific to immune cells types
SE - GI upset
Calcineurin Inhibitors
MOA
Inhibits caclineurin binding of calmodulin which activates TCRs and NFAT induced proinflammatory gene activation
Cyclosporin A
Tacrolimus (FK506)
SE - renal dysfunction, DMII, DLP, cholestasis, neuologic, non-Hodgkins lymphoma
mTOR Inhibitors
MOA
Inhibit serine/threonine protein kinase inhibiting immune cell activation and proliferation and VEGF production
Sirolimus (Rapamycin)
Everolimus
SE - impaired wound healing, cancer
Can be used to lower the dose/SE of calcineurin inhibitors
Monoclonal Antibodies
Basiliximab (Simulect; anti-CD25)
Rituximab (anti-CD20)
B-cell depletion
Desensitization and treatment of AMR
Bortezomib (Velcade; anti-CD265 proteosome)
Treats persistant AMR
Alemtuzumab (Campath; anti-CD52)
Treats Acute Rejection
Belatacept (Nulojix; CTLA4-Ig protetypic immunoglobulin fusion protein)
Inhibits Signal 2 Pathway (co-stimulation)
Polyclonal Antibodies
Antithymocyte Globulin (RATG or ATGAM)
SE - Increased PTLD and CMV
IVIG (pooled human IgG)
Desensitization and treatment of Acute AMR
What does UNOS stand for?
United Network of Organ Sharing
Etiologies of ESHF prompting heart transplant
- Ischemic - 90%
- Valvular - 2%
- Adult Congenital - 2%
- Retransplant - 2%
Indications for Heart Transplant
- Systolic HF (EF 35%)
- Intractable Angina
- Intractable Arrhythmias
- Hypertrophic Cardiomyopathy (NYHC IV despite all therapies)
- Congenital HD withOUT fixed PHTN
- Cardiac Tumor (without invasion or metastasis)
- Restrictive Cardiomyopathy (NYHC IV despite all therapies)
Absolute Contraindications to Heart Transplant
- Age > 65-75
- Fixed PHTN (PVR > 6 woods units; PV gradient > 15mmHg)
- Systemic illness limiting survival
- Cancer (<2-5y survival)
- HIV/Aids
- Systemic Lupus
- Sarcoidosis with multisystem involvement
- Systemic process with high risk of involvement of the donor heart
- Irreversable other organ failure
Relative Contraindications for Heart Transplant
- Recent Malignancy
- COPD
- Unresolved PE or Pulmonary Infarct
- DM with end-organ damage
- PVD
- Cerebral VD
- Acute PUD
- Current or recurrent diverticulitis
- Systemic illness likely to limit survival or rehab
- BMI < 20 or > 35
- Severe osteoporosis
- Active Smoking/EtOH/Drugs
- Hx of non-compliance
- Psychiatric illness likley to interfere with compliance
- Absence of psychosocial supports
Calculate Pumonary Vascular Resistance
TPG (mmHg) = MPAP (mmHg) - PCWP (mmHg)
PVR (woods units) = MPAP (mmHg) - PCWP (mmHg)
CO (L/min)
PVRI = PVR
BSA
TPG > 15mmHg or PVR > 6 woods units indicative of PHTN
Determination of Fixed vs. Reversible PHTN
PVR > 6 woods units without evidence of reversibility
Reversibility on right heart cath…
- Nitroprusside (0.5ug/kg/min)
- Adenosine
- Prostaglandin E1
- Milrinone
- Inhaled NO
- Prostacyclin
Decrease in PVR of > 2.5 woods units or 50%
REMATCH Trial
29 Patients
VAD vs. OMT
Survival at 1-year 52% vs. 28%
Survival at 2-years 29% vs. 13%
Determinants of Recipient Priority/Organ Allocation
- Blood Type
- Body Size
- Duration of Time at a particular status level
- Geographic Distance
UNOS Status 1A
- MCS (IABP, VAD, TAH, ECMO)
- MCS > 30-days with complications
- Mechanical Ventilation
- Continuous Inotropes or invasive hemodynamic monitoring
- Life Expectancy < 7-days
UNOS Status 1B
- VAD > 30-days
- Continuous IV Inotropes
What is Autonomic/Cytokine Storm?
- Norepinepherine release causes endocardial ischemic
- Cytokine release causes myocardial depression
- Vasodilitation
- Loss of temperature regulation
Autonomic Response to Brain Stem Death
- Loss of Sympathetic Tone
- Hypovolemia
- Hypotension
- Hypothermia
- Dysrrhythmias
- DM Insipidus
Brain Death Criteria
Clinical
- Etiology consistent clinical picture
- Exclude metabolic or drugs
- Core temperature > 36°C
- No reversible paralysis
- SBP > 100mmHg
- No spontaneous respiration
Comatous
- No motor response
- No brainstem reflexes
- Outside standoff period 6-24hrs
- Confirmed by 2 qualified people
- Apnea test (patient resp-optimized pre, no spont resp off vent, ABG at 8-10min shows PCO2>60 or rise>20)
Ancillary
- EEG consistent with brain death
- No cerebral blood flow by doppler or MRI
Contraindications for Heart Donoation
- Malignancy (non-cerebral)
- Severe CAD
- Contusion
- Prolonged HoTN
- Prolonged Arrest
- Septicemia
- Intracardiac drug injection
- HIV/HBV/HCV
Prinicples of Stabilzation of the Heart Donor
- Swan
- Minimize Volume
- Inotropic Support (MAP>60, CVP6-10)
- DDAVP for DM Insipidus
- Maintain Normothermia
- Maintain Acid/Base
- Treat Thyroid (triiodothronine 4ug + 3ug/h)
- Steroids (methylpred 15mg/kg)
- Maintain blood sugars
Steps of Heart Procurement
- Mobilize and encirle the…
- IVC
- SVC
- Azygous
- Aorta
- PA(s)
- Heparinize (30 000U)
- Ligate the SVC and Azygous
- Transect IVC
- Vent the LV (LAA or RUPV)
- X-clamp Ao and administer cardioplegia
- Cold saline and slush
- Apicalize the heart and transect…
- Pulmonary vv. or LA cuff
- Aorta
- MPA or RPA/LPA
- Check for PFO
- Pack on ice
Principles of Organ Preservation
- Static Hypothermia (4-10°C)
- Diastolic Arrest
- Safe ischemic Time (<6-hours)
Cardioplegia Solutions for Heart Procurement
Intracellular Solutions
Mod-High K / Low Na
Decrease hypothermia induced cellular edema
- University of Wisconsin
- Euro-Collins
- Bretschnieders (HTK)
- Intracellular Stanford
Extracellular Solutions
Low-Mod K / High NA
Avoid intracellular damage and increased SVR caused by high K
- Hopkins
- Celsior
- Krebs
- St. Thomas Hospital
Describe the 5 Different Techniques for Heart Transplantation
- Orthotopic
- Heterotopic
- Bicaval
- Shumway (RA and Septum)
- Biatrial (RA and LA cuffs)
Advantages of Bicaval Approach to Heart Transplant
- Increased Survival
- Less Arrhythmias (earlier return to NSR)
- Improved RV Function
- Decreased Early RA Pressure
- Decreased TR
Special Surgical Considerations when performing Heart Transplant post-LVAD
- Minimize manipulation of the LAA and LVApex to avoid entraining air
- Clamp outflow graft before initiating CPB to avoid backward flow through device
- More likely to be vasolplegic post with the reintroduction of pulsitile flow
Consequences of Autonomic Denervation
- Increased intrinsic SA node rate (90-110bpm)
- Decreased rate response to hypovolemia/hypoxia/anemia
- Orthostatic hypotension
-
Absence of response to treatments with MOA through autonomic nervous system
- Carotid message
- Valsalva
- Atropine
- Digoxin
Etiologies of Early Allograft Failure
- Donor Instability
- PHTN
- Ischemic injury during preservation
- Acute Rejection (rare)
Management of PHTN and RV Failure Post-Transplant
- Inhaled NO
- Nitroglycerine
- Nitroprusside
- PGE1
- Prostacyclin
- IABP
- VAD
- ECMO
Common Arrhythmias Post-Transplant and their Treatment
Sinus/Junctional Bradycardia (50%)
Treat with Theophylline
RFs - prolonged organ ischemic time; abnormal nodal artery; biatrial anastomoses, preop amiodarone, rejection
AFib/Flutter/SVT (30%)
Alterations to Medication Responses Post-Transplant
No Effect
- Atropine
- Digoxin
- Class Ia antiarrhythmics (procainamide)
Attenuated Effect
- Dopamine
- Ephedrin
Exagerated Effect
- Beta-blockers
- Calcium channel blockers
- Adenosine
- Epi/Norepinephrine
Hyper-Acute Rejection
(RF, MOA, Timeline, Histology, Treatment)
RF - Young Female Donor
MOA - Donor-specific antibodies (ABO or PRA)
Occurs in Minutes to Hours
Histology - global interstitial hemorrhage and edema with immunoglobulin and complement deposition
Treatment
- Plasmaphoresis
- IVIG
- Mechanical support
- Retransplant
ISHLT Grading of ACR (Acute Cellular Rejection)
- Interstitial or Perivascular Infiltrate and
- Myocyte Damage
Grade 0R - No Rejection
Grade 1R - (Mild) 1 Focus
Grade 2R - (Moderate) 2 or more Foci
Grade 3R - (Severe) Diffuse with hemorrhage, edema and/or vasculitis
ISHLT Grading of Acute AMR (Antibody-Mediated Rejection)
- Histologic Features
- Immunologic Features (CD68 or C4D staining)
AMR 0 - No Rejection
AMR 1(H) - Histologic only
AMR 1(I) - Immunologic only
AMR 2 - Both
AMR 3 - Severe histologic features (hemorrhage, edema, capillary fragmentation, multi cell infiltrates, endothelial cell pyknosis/karyorrhexis)
CMR (Cell Mediated Rejection) Treatment
High Dose Prednisone 100mg/d
Change
- Tacrolimus → Cyclosporine
- Sirolimus → MMF or Azathioprine
If severe or in the first 3 months
- IV methelprednisolone 1000mg/d
- OKT3
- Thymoglobulin
- Antithymocyte Globulin
AMR (Antibody Mediated Rejection) Treatment
- High Dose Corticosteroids
- Thymoglobulin
- Plasmaphoresis
- IVIG
- Cyclophosphamide, MMF
- Heparin
Indications for Retransplantation
Early Allograft Failure
Chronic Allograft Vasculopathy (CAV)
Refractory Acute Rejection
1yr Survival for Retransplantation
Within 6 month - 50%
After 2 years - 85% (comparable to initial Tx)
Risk Factors
- Older recipient age
- Elevated creatinine
- Preop mechanical ventilation
- Bridge to Tx with ECMO or VAD
Survival following Heart Transplantation
30 day - 5-10%
1 year - 85%
Annual risk of death - 3.5%
Better
- age < 55
- young donor
- shorter ischemic time
- caucasian
- centre volume > 9/yr
Worse
- diabetes
- mechanical ventilation
Common COD post-heart transplant
Early (30d)
- Graft Failure
- MSOF
- Infection
1 Year
- Infection
- Graft Failure
- Acute Rejection
Late
- CAV (chronic allograft vasculopathy)
- Malignancy
Lung Allocution Score
Days on the wait list subtracted from predicted 1 year post-transplant survival using the following criteria:
Age, height, weight, lung Dx code, functional status, 6 min walk test, ventalitory support, oxygen requirements, FVC, systemic PAP, mean PAP, PCWP, current pCO2, lowest pCO2, highest pCO2, change in pCO2, diabetes, creatinine
Serum titers to be measure prior to listing specifically for lung transplantation
- Histoplasma
- Coccidioides
- Toxoplasma
HLA donor-recipient matching at the following loci improves graft survival
Heart
- HLA-DR
Lung
- HLA-B
- HLA-DR
PRA > 25 in a lung transplant recipient…
…Necessitates a prospective crossmatch for lung transplantation
PRA > 10 in a heart transplant recipient…
…Necessitates a prospective crossmatch for heart transplantation
Indications for Lung Transplant
- COPD/Emphysema
- Interstitial Pulmonary Fibrosis
- Cystic Fibrosis
- A1 Anti-trypsin Deficiency
- Idiopathic Pulmonary Artery Hypertension
- Bronchiectasis
- Congenital Heart Disease
- Obliterative Bronchiolitis
- Sarcoidosis
- Interstitial Pneumonitis
- Cancer
- Allograft Failure
Contraindications for Lung Transplant
- Age > 65
- Systemic or MSOD
- Irreversible Liver or Renal Dysfunction
- Active malignancy (other than non melanoma skin)
- Corticosteroids
- Cachexia or Obesity
- Pan-resistant Pulmonary Flora
- Active Smoking
- EtOH or drug abuse
- Psychiatric illness with noncompliance
- Previous Cardiothoracic Surgery (relative)
- Osteoporosis
- Prolonged mechanical ventilation
- HIV
- HCV/HBV with Bx proven liver disease
Post-Transplant Lymphoproliferative Disorder
Diagnosis/Histology/Treatment/Prognosis
Diagnosis/Histology
High index of suspicion and Bx
Presence of lymphoproliferation and EBV DNA/RNA/protein
Treatment
d/c Immunosuppression
Treat malignancy (surgery/rad/chemo/inerferon/immunoglobulin)
Outcomes
Mortality 60-100%