Myocardial Protection in Pediatric Cardiac
Surgery
No Disclosures
High KHigh K++ cardiac arrestMelrose 1955 –Potassium citrate ( 77m mol/L)
~~20 years(Mortality 20 years(Mortality ~~10-20%)10-20%)Hypothermia: systemic and/or topical Hypothermia: systemic and/or topical
Bigelow et al. 1950; Shumway et al. 1959; Swan 1973
Continuous or intermittent aortic occlusionCooley et al. 1962
Aortic root or intracoronary blood perfusion Kay et al. 1958
Ellectrically induced VF (fibrilator) Ellectrically induced VF (fibrilator) Senning 1952
History History
Pharmacological arrest was first Pharmacological arrest was first successfully used by successfully used by Bretschneider* in 1964 (HTK)Bretschneider* in 1964 (HTK)
St. Thomas in 1975 St. Thomas in 1975 Blood cardioplegia Blood cardioplegia
Buckberg et al, in 1978 Buckberg et al, in 1978
History History
*Bretschneider HJ (1964) U˝ berlebenszeit und Wiederbelebungszeit des Herzens bei Normo
undHypothermie. Verh Deutsch Ges Kreislaufforschung 30: 11 34.
Importance of MP
1.1. IIrreversible ischemic damage rreversible ischemic damage begins tobegins to occur in the occur in the normothermic normothermic heart after only 20 heart after only 20 minmin
2.2. However, However, when current techniques when current techniques of myocardial protection are used, of myocardial protection are used, arrest times of more than 4 or 5 arrest times of more than 4 or 5 hours may behours may be tolerated without tolerated without irreversible damageirreversible damage
1. Reimer KA,et al. Am J Cardiol 1983;52:72A2. Hosenpud JD, et al. J Heart Lung Transplant 2001;20;805
Morphological differences between pediatric/adult
myocardium In the newborn only 30% of the In the newborn only 30% of the
myocardial massmyocardial mass comprises comprises contractile tissue compared with contractile tissue compared with 60% in60% in the mature myocardium. the mature myocardium.
Pediatric myocardium has fewer Pediatric myocardium has fewer mitochondria andmitochondria and less oxidative less oxidative capacity.capacity.
Clinical differences between pediatric/adult
myocardium NNormal immature myocardiumormal immature myocardium has a has a
greater tolerance to ischemia when greater tolerance to ischemia when compared tocompared to mature myocardiummature myocardium11..
HHypoxicypoxic neonatal heart is more neonatal heart is more sensitive to ischemia than thesensitive to ischemia than the adultadult2. .
When cWhen compared with infants, ompared with infants, children children have have had significantly less had significantly less reperfusion injury and better reperfusion injury and better clinical outcomeclinical outcome 3..
1. Yano Y et al. J Thorac Cardiovasc Surg 1987;94:8872. Kempsfor RD, et al. J Thorac Cardiovasc Surg 1989;97:8563. Imura H, et al. Circulation 2001;103:1551
1. Physiological differences between
pediatric/adult myocardium Immature myocardium Immature myocardium 1-3
Decreased ventricular complianceDecreased ventricular compliance Less preload reserveLess preload reserve Decreased Decreased sensitivity to catecholamines sensitivity to catecholamines in in
immature heartsimmature hearts Less inotropic reserve (with maximum Less inotropic reserve (with maximum
adrenergic stimuli)adrenergic stimuli) More (-) inotropic response to anesthetic agentsMore (-) inotropic response to anesthetic agents Cardiac output in pediatric patients is more Cardiac output in pediatric patients is more
dependent on heart rate and sinus rhythm.dependent on heart rate and sinus rhythm. Increase oIncrease off afterload will produce significant afterload will produce significant
hemodynamic impairmenthemodynamic impairment
1. Teitel D, et al. J Am Coll Cardiol 1983;1:11832. Boudreaux JP, et al. Anesth Analg 1984;63:7313. Caspi J, et al. Circulation 1991;84(Suppl 3):394
2. Physiological differences between pediatric/adult
myocardium Immature myocardium is more sensitive to Immature myocardium is more sensitive to
extracellular Ca levels than mature extracellular Ca levels than mature myocardiummyocardium1,21,2..
The The sarcoplasmic reticulum is underdeveloped in sarcoplasmic reticulum is underdeveloped in the pediatricthe pediatric heart heart
reduced storage capacity for calcium reduced storage capacity for calcium 33
The activity of the SR Ca ATPase is lower than in The activity of the SR Ca ATPase is lower than in the adult heartthe adult heart
Antioxidant defense Antioxidant defense systemsystem is reduced in is reduced in cyanotic heart defectscyanotic heart defects4,54,5
Catalase ↓Catalase ↓ Superoxide dismutase ↓Superoxide dismutase ↓ Glutathione reductase ↓Glutathione reductase ↓
1. Gombosova I, et al. Am J Physiol 1998;274:H21232. Boucek RJ, et al. Pediatr Res 1984;18:9483. Boland R, et al. J Biol Chem 1974;249:6124. Teoh KH,et al. J Thorac Cardiovasc Surg 1992; 104:1595. del Nido PJ,et al. Circulation 1987;76:174
Differences between the immature and mature
myocardium on primary sourse of ATP
Myocardial protection in pediatric cardiac
surgery Cardioplegic arrest On-pump beating heart
The advantages of cardioplegia
Diastolic arrest of the contractive components and cessation of electrical activity
Reduction of metabolic activity (arrest and hypothermia)
Intermittent oxygen delivery (blood) Maintaining acid-base balance Maintaining high osmotic P counteracts
tissue edema Modifying reperfusion (prevention of
reperfusion injury) Reversible Low toxicity
TThehe type of type of cardioplegia cardioplegia
There is still no consensus on the type of cardioplegia
There are 167 different cardioplegic solutions used for only heart transplantation in USA 1.
1.Demmy TL, et al. Ann Thorac Surg 1997;63:262
Cardioplegia Composition and
additives K+
Mg++
Ca++
Buffering Systems (HCO3
-, THAM) Glutamate–aspartate Glucose
Insulin Oxygen-derived free
radical scavengers Superoxide dismutase,
catalase, Glutathione peroxidase, Glutathione, Vit E,A, ascorbate, Allopurunol Desferrioxamine
Procainamide
Beta blockers (esmolol)
Na+-H+ exchange inhibitor (Amiloride, Cariporide)
Na+blocker (lidocaine, tetrodotoxin)
L-Arginine
K+ channel openers Aprikalim, pinacidil,
nicorandilC
a++ channel blockers
Blood vs crystalloid cardioplegia
Crystalloid cardioplegia Delivery is simple and cheap One single shot is possible
Blood cardioplegiaHemoglobin is used for O2 transportationMetabolic substrates Physiological buffersPhysiological osmotic PLess hemodilution Endogeneous oxygen free radical scavengerBlood C is superior to crystalloid C over 1 h ischemia
* Corne AF. J Thorac Cardiovasc Surg 93:163:19872,*
Hypothermia
Hypothermia has been used since Hypothermia has been used since 1950 for myocardial protection 1950 for myocardial protection
The methods to cool the heart The methods to cool the heart Cold cardioplegia Cold cardioplegia Systemic coolingSystemic coolingTopical myocardial cooling » damage to Topical myocardial cooling » damage to
phrenic nerve !!phrenic nerve !!
Less OLess O2 2 consumption in arrested consumption in arrested heartheart
Warm cardioplegia
Hypothermia - Hypothermia - depletion of depletion of myocardialmyocardial energy suppliesenergy supplies
Lichtenstein * 1989 6.5 h CC (normothermic continuous blood cardioplegia)
*Lichtenstein SV et al, Lancet 1989.**Lichtenstein SV et al, Ann Thorac Surg 1991.
Warm and cold combined cardioplegia
Warm and cold combined blood Warm and cold combined blood cardioplegia cardioplegia Warm inductionWarm inductionCold cardioplegiaCold cardioplegiaHot shotHot shot
Delivery techniques Antegrade, retrograde, or
combined?A
nterograde delivery: a
dvantages and disadvantages Simple Uniform distribution
of cardioplegia AI: poor antegrade
coronary perfusion Aortic valve or root
surgery injury to the
coronary ostia
Delivery techniques Antegrade, retrograde, or
combined?R
etrograde delivery: a
dvantages and disadvantages Nonphysiological Nonhomogenous
distribution Decreased flow to the
right ventricle and septum
The advantage in AI and aortic root surgery
Risk of ruptere of the coronary sinus
Single-dose/multi-dose /multi-dose CardioplegiaCardioplegia
Single-doseSingle-doseContinuous (adult heart)Continuous (adult heart)Multi-dose cardioplegiaMulti-dose cardioplegia
Cold cardioplegia every 20-30 minCold cardioplegia every 20-30 minWarm cardioplegia every 15-20 minWarm cardioplegia every 15-20 min
Myocardial injury after surgery
Ventricular hypertrophyVentricular hypertrophy Pre-ischemic energy depletionPre-ischemic energy depletion Length of the ischemic intervalLength of the ischemic interval Incomplete myocardial protectionIncomplete myocardial protection
Ventricular distention (failure to vent the LA adequately)
Retraction and stretch injury to the myocardium
Ventriculotomy edema (hemodilution or low colloid oncotic P)
Reperfusion injury Reperfusion injury Coronary artery injury or embolism of air Coronary artery injury or embolism of air
bubbles bubbles
Low output after surgery
Hypocalcemia, acidosis, hypoxia
Residuel volume overload (VSD, PY,AY)
Residual pressure overload (LVOTO,RVOTO)
Cardiac compression (oedema, tamponade)
Decreased preload (hypovolemia, diastolic dysfunction)
Increased afterload (systemic HT, PHT)
Arrhythmia (AV block, AF, JET, VT )
Myocardial protection in our clinic
Miniplegia – Anterograde
On-pump beating BDCPS, FontanPS, PVR, TVR
The cystalloid composition for
Miniplegia Infusion pump composition
30 meq K+
10 meq Mg++
20 ml 30% dextrose Induction [[KK++]] 25 meq/L 25 meq/L Maintenance [[KK++]] 13 meq/L 13 meq/L
1. Result 1. Result
WhenWhen a medical a medical center decide center decidess onon the myocardial protection the myocardial protection method, the most important method, the most important determinants are the determinants are the clinical clinical results results and the surgeons’ and the surgeons’ experiences.experiences.
ThThisis method method shouldshould be effective, be effective, simple, cheap and simple, cheap and should should be be accepteacceptedd by by allall surgeonssurgeons..
2. Results2. Results
Myocardial protection is challengingMyocardial protection is challenging in in some casessome cases
LLongong operations operations CComplexomplex operations operations which recurrent which recurrent
cardioplegia delivery from the cardioplegia delivery from the open open aortic root aortic root isis requiredrequired
Newborn patientsNewborn patients Preoperatively damaged Preoperatively damaged
myocardiummyocardium
3. Results3. Results
The The medical medical center center shouldshould evaluate evaluate the protection method with respect to the protection method with respect to the outcome in different proceduresthe outcome in different proceduresIf the morbidity and mortality rate If the morbidity and mortality rate
is high in especially long and is high in especially long and complex procedures, complex procedures, the the myocardial myocardial protection methodprotection method must also be must also be considered as a risk factor. considered as a risk factor.
T
Thank You!