Peter Pastuszko

The hybrid procedure for the borderline left ventricle.

UNLABELLED IntroductionIn patients with varying degrees of left heart hypoplasia, it is often difficult to determine whether the left heart structures are adequate in size to support biventricular circulation. Historically, the decision to pursue a single ventricle or biventricular repair needed to be made early and was often irreversible. The hybrid procedure may be a better initial approach for patients with borderline left ventricles. METHODS We describe a series of four patients with various congenital cardiac malformations, all of whom had borderline left ventricles. Based on pre-operative echocardiograms, several scoring systems and left ventricle volumes were used to predict the optimal type of repair. A left ventricular volume of 20 millilitres per square metre was used as the minimum cut-off value for adequacy of biventricular repair. RESULTS The left ventricular volumes for the patients were 17.1, 23.7, 25.4, and 25.8 millilitres per square metre. In none of the four patients were the calculations unanimous in the recommendation to pursue either type of repair. All patients underwent the hybrid procedure and then eventual single ventricle palliation (two patients) or biventricular repair (two patients). All survived with a mean follow-up of 18 plus or minus 3.9 months. CONCLUSIONS The hybrid procedure may be the best option in patients with a borderline left ventricle. It can serve as a bridge to a more definitive repair when patients are older, larger, and for whom the decision between single ventricle and biventricular repair can be more easily made.

The effect of hypothermia on neuronal viability following cardiopulmonary bypass and circulatory arrest in newborn piglets

OBJECTIVE To determine the effect of recovery with mild hypothermia after cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) on the activity of selected key proteins involved in initiation (Bax, Caspase-3) or inhibition of apoptotic injury (Bcl-2, increased ratio Bcl-2/Bax) in the brain of newborn piglets. METHODS The piglets were placed on CPB, cooled with pH-stat management to 18 degrees C, subjected to 30 min of DHCA followed by 1h of low flow at 20 ml/kg/min, rewarmed to 37 degrees C (normothermia) or to 33 degrees C (hypothermia), separated from CPB, and monitored for 6h. Expression of above proteins was measured in striatum, hippocampus and frontal cortex by Western blots. The results are mean for six experiments+/-SEM. RESULTS There were no significant differences in Bcl-2 level between normothermic and hypothermic groups. The Bax levels in normothermic group in cortex, hippocampus and striatum were 94+/-9, 136+/-22 and 125+/-34 and decreased in the hypothermic group to 59+/-17 (p=0.028), 70+/-6 (p=0.002) and 48+/-8 (p=0.01). In cortex, hippocampus and striatum Bcl-2/Bax ratio increased from 1.23, 0.79 and 0.88 in normothermia to 1.96, 1.28 and 2.92 in hypothermia. Expression of Caspase-3 was 245+/-39, 202+/-74 and 244+/-31 in cortex, hippocampus and striatum in the normothermic group and this decreased to 146+/-24 (p=0.018), 44+/-16 (p=7 x 10(-7)) and 81+/-16 (p=0.01) in the hypothermic group. CONCLUSION In neonatal piglet model of cardiopulmonary bypass with circulatory arrest, mild hypothermia during post bypass recovery provides significant protection from cellular apoptosis, as indicated by lower expression of Bax and Caspase-3 and an increased Bcl-2/Bax ratio. The biggest protection was observed in striatum probably by decreasing of neurotoxicity of striatal dopamine.

Effect of granulocyte-colony stimulating factor on expression of selected proteins involved in regulation of apoptosis in the brain of newborn piglets after cardiopulmonary bypass and deep hypothermic circulatory arrest

OBJECTIVE The study objective was to investigate the effect of granulocyte-colony stimulating factor on the expression of proteins that regulate apoptosis in newborn piglet brain after cardiopulmonary bypass and deep hypothermic circulatory arrest. METHODS The newborn piglets were assigned to 3 groups: (1) deep hypothermic circulatory arrest (30 minutes of deep hypothermic circulatory arrest, 1 hour of low-flow cardiopulmonary bypass); (2) deep hypothermic circulatory arrest with prior injection of granulocyte-colony stimulating factor (17 μg/kg 2 hours before cardiopulmonary bypass); and (3) sham-operated. After 2 hours of post-bypass recovery, the frontal cortex, striatum, and hippocampus were dissected. The expression of proteins was measured by gel electrophoresis or protein arrays. Data are presented in arbitrary units. Statistical analysis was performed using 1-way analysis of variance. RESULTS In the frontal cortex, only Fas ligand expression was significantly lower in the granulocyte-colony stimulating factor group when compared with the deep hypothermic circulatory arrest group. In the hippocampus, granulocyte-colony stimulating factor increased Bcl-2 (54.3 ± 6.4 vs 32.3 ± 2.2, P = .001) and serine/threonine-specific protein kinase (141.4 ± 19 vs 95.9 ± 21.1, P = .047) when compared with deep hypothermic circulatory arrest group. Caspase-3, Bax, Fas, Fas ligand, death receptor 6, and Janus protein tyrosine kinase 2 levels were unchanged. The Bcl-2/Bax ratio was 0.33 for deep hypothermic circulatory arrest group and 0.93 for the granulocyte-colony stimulating factor group (P = .02). In the striatum, when compared with the deep hypothermic circulatory arrest group, the granulocyte-colony stimulating factor group had higher levels of Bcl-2 (50.3 ± 7.4 vs 31.8 ± 3.8, P = .01), serine/threonine-specific protein kinase (132.7 ± 12.3 vs 14 ± 1.34, P = 2.3 × 10(6)), and Janus protein tyrosine kinase 2 (126 ± 17.4 vs 77.9 ± 13.6, P = .011), and lower levels of caspase-3 (12.8 ± 5.0 vs 32.2 ± 11.5, P = .033), Fas (390 ± 31 vs 581 ± 74, P = .038), Fas ligand (20.5 ± 11.5 vs 57.8 ± 15.6, P = .04), and death receptor 6 (57.4 ± 4.4 vs 108.8 ± 13.4, P = .007). The Bcl-2/Bax ratio was 0.25 for deep hypothermic circulatory arrest and 0.44 for the granulocyte-colony stimulating factor groups (P = .046). CONCLUSIONS In the piglet model of hypoxic brain injury, granulocyte-colony stimulating factor decreases proapoptotic signaling, particularly in the striatum.

Bicuspid aortic valves experience increased strain as compared to tricuspid aortic valves.

Objective: To determine whether the leaflets of bicuspid aortic valve (BAV) experience increased strain when compared to tricuspid aortic valve (TAV) leaflets. Background: The population at highest risk of aortic valve calcification (AVC) are individuals with BAVs. Currently, efforts to medically treat AVC are hampered by a limited understanding of the biomechanical forces involved in the molecular pathogenesis of AVC. Methods: Surgically created BAVs and control TAVs were placed into a left heart simulator. Strains were calculated by comparing the distances between points on the aortic valve (AoV) leaflet during various time points during a simulated cardiac cycle. Results: The fused leaflets of BAVs experience significantly more strain during systole when compared to TAVs. Specifically, BAVs experience 24% strain (P < .0001) in the radial direction, parallel to the direction of blood flow, as compared to TAVs. There was peak difference of 4% (P < .001) in the circumferential direction. Discussion: Based upon the data presented here, we are in the process of identifying how increased strain activates calcification-associated pathways in AoV cells. Future studies will examine whether these stretch responsive pathways can be blocked to inhibit calcification of BAVs.

Purification of neurocatin, a neuroregulatory factor from brain

A neuroregulatory factor (neurocatin) has been isolated from bovine brain. Neurocatin is a powerful affector of catecholamine metabolism in synaptosomes isolated from rat brain, causing increased formation of norepinephrine (NE) and decreased formation of 3,4-dihydroxyphenylacetic acid (DOPAC). The ratio NE/DOPAC in synaptosomes has been used to measure the neurocatin content of samples during isolation. Neurocatin has now been purified to a single chromatographic peak by high-resolution HPLC and a preliminary amino acid content measured. It appears to be a small peptide with a molecular weight in the range of 2,000-2,500 Da.

Effect of deep hypothermic circulatory arrest followed by low-flow cardiopulmonary bypass on brain metabolism in newborn piglets: comparison of pH-stat and α-stat management.

Objective: To compare the effects of pH-stat and &agr;-stat management before deep hypothermic circulatory arrest followed by a period of low-flow (two rates) cardiopulmonary bypass on cortical oxygenation and selected regulatory proteins: Bax, Bcl-2, Caspase-3, and phospho-Akt. Design: Piglets were placed on cardiopulmonary bypass, cooled with pH-stat or &agr;-stat management to 18°C over 30 mins, subjected to 30-min deep hypothermic circulatory arrest and 1-hr low flow at 20 mL/kg/min (LF-20) or 50 mL/kg/min (LF-50), rewarmed to 37°C, separated from cardiopulmonary bypass, and recovered for 6 hrs. Subjects: Newborn piglets, 2–5 days old, assigned randomly to experimental groups. Interventions: None. Measurements and Main Results: Cortical oxygen was measured by oxygen-dependent quenching of phosphorescence; proteins were measured by Western blots. The means from six experiments ± sem are presented as % of &agr;-stat. Significance was determined by Students t test. For LF-20, cortical oxygenation was similar for &agr;-stat and pH-stat, whereas for LF-50, it was significantly better using pH-stat. For LF-20, the measured proteins were not different except for Bax in the cortex (214 ± 24%, p = .006) and hippocampus (118 ± 6%, p = .024) and Caspase 3 in striatum (126% ± 7%, p = .019). For LF-50, in pH-stat group: In cortex, Bax and Caspase-3 were lower (72 ± 8%, p = .001 and 72 ± 10%, p = .004, respectively) and pAkt was higher (138 ± 12%, p = .049). In hippocampus, Bcl-2 and Bax were not different but pAkt was higher (212 ± 37%, p = .005) and Caspase 3 was lower (84 ± 4%, p = .018). In striatum, Bax and pAkt did not differ, but Bcl-2 increased (146 ± 11%, p = .001) and Caspase-3 decreased (81 ± 11%, p = .042). Conclusions: In this deep hypothermic circulatory arrest-LF model, when flow was 20 mL/kg/min, there was little difference between &agr;-stat and pH-stat management. However, for LF-50, pH-stat management resulted in better cortical oxygenation during recovery and Bax, Bcl-2, pAk, and Caspase-3 changes were consistent with lesser activation of proapoptotic signaling with pH-stat than with &agr;-stat.

Activation of striatal tyrosine hydroxylase by neurocatin, a neuroregulator from mammalian brain

Neurocatin, a neuroregulatory factor isolated from mammalian brain, is a powerful affector of dopamine synthesis in striatal rat synaptosomes. Incubation of intact synaptosomes with neurocatin caused an increase in the rate of dopamine synthesis measured by accumulation of DOPA. The increase is rapid (within two minutes) and dependent on the concentration of added neurocatin. The stimulatory effect of neurocatin on dopamine synthesis occurred only in intact synaptosomes and was almost completely abolished by lysis of the synaptosomes with Triton X-100 or sonification prior to neurocatin addition. The kinetic parameters of tyrosine hydroxylase were measured in lysates prepared from synaptosomes preincubated with neurocatin. These showed that with increasing neurocatin concentration there was an increase in Vmax with no significant change in KM for the pteridine cofactor, compared to control. Activation of tyrosine hydroxylase by neurocatin is at least partially caused by a receptor mediated increase in phosphorylation of the enzyme. Protein kinase C and protein kinase II may be involved in this process.

Whole Body Periodic Acceleration (pGz) as a non-invasive preconditioning strategy for pediatric cardiac surgery

We hypothesized that pGz has cardio and neuroprotective effects due to upregulation of pathways which include eNOS, anti-apoptotic, and anti-inflammatory pathways. We analyze protein expression of these pathways in the brain of neonatal piglets, as well as report on the myocardial function after Deep Hypothermic Circulatory Arrest (DHCA) and pGz preconditioning. Animal data affirms both a cardio and neuroprotective role for pGz. These findings suggest that pGz can be a simple, non-invasive cardio and neuroprotective strategy preconditioning strategy in children requiring surgical intervention.

Granulocyte colony-stimulating factor significantly decreases density of hippocampal caspase 3-positive nuclei, thus ameliorating apoptosis-mediated damage, in a model of ischaemic neonatal brain injury

OBJECTIVES Ischaemic brain injury is a major complication in patients undergoing surgery for congenital heart disease, with the hippocampus being a particularly vulnerable region. We hypothesized that neuronal injury resulting from cardiopulmonary bypass and associated circulatory arrest is ameliorated by pretreatment with granulocyte colony-stimulating factor (G-CSF), a cytokine and an anti-apoptotic neurotrophic factor. METHODS In a model of ischaemic brain injury, 4 male newborn piglets were anaesthetized and subjected to deep hypothermic circulatory arrest (DHCA) (cooled to 18°C, DHCA maintained for 60 min, rewarmed and recovered for 8-9 h), while 4 animals received G-CSF (34 µg/kg, intravenously) 2 h prior to the DHCA procedure. At the end of each experiment, the animals were perfused with a fixative, the hippocampus was extracted, cryoprotected, cut and the brain sections were immunoprocessed for activated caspase 3, a pro-apoptotic factor. Immunopositive neuronal nuclei were counted in multiple counting boxes (440 × 330 µm) centred on the CA1 or CA3 hippocampal regions and their mean numbers compared between the different treatment groups and regions. RESULTS G-CSF pretreatment resulted in significantly lower counts of caspase 3-positive nuclei per counting box in both the CA1 [52.2 ± 9.3 (SD) vs 61.6 ± 8.4, P < 0.001] and CA3 (41.2 ± 6.9 vs 60.4 ± 16.4, P < 0.00002) regions of the hippocampus as compared to DHCA groups. The effects of G-CSF were significant for pyramidal cells of both regions and for interneurons in the CA3 region. CONCLUSIONS In an animal model of ischaemic brain injury, G-CSF reduces neuronal injury in the hippocampus, thus potentially having beneficial effect on neurologic outcomes.

Response of Purine Metabolism and Cortical Oxygen Pressure to Hypoxia and Reoxygenation in Newborn Piglets

It has been proposed that the level of purine metabolites (particularly hypoxanthine) reflects the intracellular energy metabolism and can be used as sensitive, specific markers of response of tissue to hypoxic/ischemic conditions.26,27 Several studies have shown that hypoxic conditions cause breakdown of cellular nucleotides resulting in accumulation of hypoxanthine and xanthine4,7,8,28 and these metabolites can serve as oxidizable purine sub-strates for xanthine dehydrogenase and oxidase. One of the possible mechanisms of tissue damage during reoxygenation following hypoxic/ischemic conditions is through genera-tion of free radicals by the hypoxanthine-xanthine oxidase reactions.1,5,615,16,24,29 Under hy-poxic/ischemic conditions the elevated cytosolic calcium concentration can activate a protease, calpain, which converts xanthine dehydrogenase to xanthine oxidase.32 During posthypoxic reoxygenation xanthine oxidase catalyzes oxidation of xanthine to uric acid with formation of Superoxide radical O2 4,15,28. The Superoxide radical can further react with hydrogen peroxide produced in the same reaction and form hydroxyl radicals. Contribution of toxic oxygen metabolites from xanthine oxidase to tissue injury during reoxy-genation has been based particularly on studies showing that the inhibitors of xanthine oxidase, such as allopurinol, decrease the postischemic injury of different tissues.9,19,20,21,24