Abnormal Myocardial Enzyme Research Articles

Abnormal myocardial enzymes in the prediction of mortality and hypertension in COVID-19 patients: a retrospective study.

This study aims to determine the differences in myocardial enzymes in COVID-19 patients with and without hypertension. A total of 130 patients with COVID-19 in Yunmeng County People's Hospital were analyzed. The clinical manifestations and laboratory indicators were collected and analyzed. We found that COVID-19 patients with hypertension had higher mortality rate, greater age, and higher rates of basic disease such as diabetes than patients without hypertension. The γ-glutamyl transpeptidase (GGT), blood urea nitrogen (BUN), albumin/globulin (A/G), Ca, Mg, lactate dehydrogenase (LDH), and α-hydroxybutyric-dehydrogenase (α-HBD) levels in COVID-19 patients with hypertension were higher than in COVID-19 patients without hypertension. We found that the predictive effect of the creatine kinase isoenzyme (CK-MB), LDH-L, and α-HBD levels in the COVID-19 patients without hypertension were higher than in COVID-19 patients with hypertension. We used the ROC curve model to predict whether patients would have hypertension, and we found that CK-MB, LDH-L and HBD parameters could distinguish the COVID-19 patients with hypertension and non-hypertension, and could predict the mortality of COVID-19 patients.

Clinical and MRI differential analysis of autoimmune encephalitis and viral encephalitis

ObjectivesThe goal of this study was to analyze the clinical and magnetic resonance imaging (MRI) characteristics of autoimmune encephalitis (AE) and viral encephalitis (VE) at the initial stage of onset. MethodsThis study was a retrospective analysis of the clinical manifestations, laboratory tests, electroencephalogram examination, imaging examinations, and treatment outcomes of 24 VE patients and 20 AE patients. ResultsThe onset age was significantly younger in the VE group than in the AE group, mainly occurring in adolescents (P < 0.05). The proportions of fever, headache, and vomiting were higher in the VE group than in the AE group (P < 0.05), and there were few manifestations of central hypoventilation. The incidence of abnormal myocardial enzymes was significantly higher in the VE group than in the AE group (P < 0.05). There was no significant difference in electroencephalogram test results between the VE and AE groups. Regarding magnetic resonance imaging (MRI), the proportion of single lesion involving a single lobe or multiple asymmetries involving the limbic system in the VE group was higher than that in the AE group (P < 0.05). The incidence of lesion enhancement in the VE group was higher than that in the AE group. Meanwhile, diffusion-weighted imaging sequence was more sensitive than T2 liquid-attenuated inversion recovery sequence in the detection, efficacy evaluation, and follow-up review of the AE and VE groups. ConclusionThe onset age of VE is younger, and the clinical symptoms of AE and VE differ with statistical significance. MRI can objectively reflect the imaging characteristics of both groups. Combining early clinical manifestations with imaging manifestations can facilitate early diagnosis and treatment, and improve the prognosis.

Clinical findings, diagnosis and therapy of patent ductus venosus in children: a case series.

Patent ductus venosus (PDV) is a rare form of congenital portosystemic shunt. Because of the diversity of clinical symptoms and insufficient knowledge of this condition, clinicians often fail to perform targeted examinations, resulting in missed diagnoses and misdiagnoses. This study summarized the clinical and radiological findings, as well as surgical methods, of PDV with the aim of improving early diagnosis and guiding treatment. Clinical, laboratory, and radiologic data of patients with PDV were analyzed retrospectively. In all, 9 patients with PDV were included in the study (7 male, 2 female; median age 1.6 years, age range 16 days to 16.5 years). Data for all 9 patients with PDV were reviewed. The most common initial clinical presentations were jaundice and respiratory symptoms. Laboratory data revealed hypoxemia in 5 patients, hyperammonemia in 2, hyperbilirubinemia in 7, abnormal coagulation function in 6, abnormal myocardial enzymes in 4, hepatic dysfunction in 8, and renal dysfunction in 3. The direct imaging sign of PDV was a vascular structure connecting the left branch of the portal vein (LPV) to the inferior vena cava. Secondary imaging findings observed in all 9 patients were dilated right heart, pulmonary artery, and LPV, and an atrophic right branch of the portal vein. The main portal vein was dilated in 8 patients and shrunk in 1. Moreover, 8 patients had enlarged livers, and 3 presented with hypoperfusion in the right lobe of the liver. The spleen was enlarged in 8 patients but shrunk in 1. Renal imaging was abnormal in 2 patients. Hepatic encephalopathy was found in 4 patients; 7 patients had PDV combined with other malformations, with congenital heart disease and vascular abnormalities being the most common; 3 patients successfully underwent surgical ligation of PDV. PDV can lead to multisystem damage. Secondary radiological signs of PDV play an important role in early diagnosis and preoperative evaluation. Complications and coexisting malformations were common and should not be missed during preoperative evaluation. Early surgical closure for PDV is recommended.

Reducing oxidative stress may be important for treating pirarubicin-induced cardiotoxicity with schisandrin B.

The cardiotoxicity of pirarubicin (THP) seriously affects its clinical application, which cannot be ignored. The antioxidant effect of schisandrin B (SchB) has been extensively reported in the context of dietotherapy. However, whether this antioxidant effect can protect the heart from THP damage remains unknown. The aim of the present study was to investigate whether the antioxidant effect of SchB can antagonize the cardiotoxicity of THP. Changes in electrocardiogram (ECG), echocardiography and serum lactate dehydrogenase, brain natriuretic peptide, creatine kinase MB and cardiac troponin T levels were used to detect the degree of cardiac damage. The levels of superoxide dismutase (SOD), malondialdehyde, catalase and total antioxidant capacity in the serum and heart were measured to observe the oxidative stress state of rats. Primary cardiomyocytes were cultured, and cell viability and reactive oxygen species (ROS) production were detected. Western blotting was used to detect the expression levels of SOD2, NOX2, pro/cleaved-caspase3 and Bcl-2/Bax in heart tissue and primary cardiomyocytes to verify the related signaling pathways. THP-treated rats showed a range of cardiac damage, including an abnormal ECG, echocardiography and myocardial enzymes. In the cellular experiments, cell viability decreased and ROS increased. However, this damage was alleviated after SchB treatment. Further studies demonstrated that SchB antagonized THP cardiotoxicity via its antioxidant effect. In conclusion, SchB protects the heart from THP damage in rats, and the mechanism may be closely associated with its antioxidant effect.

Association of Myocardial Enzyme Abnormality with Clinical Outcomes of Patients with COVID-19: A Retrospective Study.

Background It has been observed that COVID-19 may cause myocardial damage, but there are few detailed reports on myocardial enzyme abnormalities. Methods In this retrospective study, we analyzed data from 157 consecutive laboratory-confirmed and hospitalized COVID-19 patients from Wuhan. We collected information on demographic and clinical characteristics, laboratory findings, and clinical outcomes. Logistic regression analysis was used to explore the risk factors associated with the severity of COVID-19. The association between myocardial enzyme abnormalities and the mortality was also investigated. Results The mortality in abnormal myocardial enzyme group was obviously higher than the normal group (P < 0.001). The majority of patients (n = 72, 97.3%) with normal cardiac enzyme group were of the common novel coronavirus pneumonia (NCP) type, whereas half of the patients with cardiac enzyme abnormalities (n = 40, 48.2%) developed critical and severe NCP type. The multivariable logistic regression analysis indicated that COVID-19 patients with increasing age (P = 0.035), higher levels of CRP (P = 0.038), and TNI (P = 0.036) were associated with increased death than other patients. Conclusions Myocardial enzyme abnormality and myocardial injury were associated with the severity and fatal outcomes of COVID-19. Clinicians should pay attention to the markers of myocardial injury in COVID-19 patients, especially those with older age, comorbidities, and inflammation.

Abnormal Myocardial Enzymes are Important Indicators of Poor Prognosis in COVID-19 Patients

Objective: Researching the prognostic value of myocardial enzymes in COVID-19 patients. Materials & methods: We collected 113 confirmed COVID-19 patients. The dynamic changes of CK, LDH and α-HBDH in patients were studied retrospectively, the correlation between myocardial enzyme index, clinical classification and outcome of patients and its significance to prognosis. Results: There are significant statistical differences between LDH, α-HBDH, CK and the clinical classification, and patient’s outcome. In the receiver operating characteristic curve analysis, LDH, α-HBDH and CK have a good diagnostic value for the death outcome of patients. Conclusion: LDH, α-HBDH and CK were the components of myocardial enzyme profiles, and our results found that they were significantly positively correlated with clinical classification and prognosis of COVID-19 patients. The values of LDH, α-HBDH and CK increased with the increase of the severity of admission clinical classification and the deterioration of outcome. Therefore, we propose that continuous monitoring of LDH, α-HBDH and CK indicators can warn the deterioration of COVID-19 to a certain extent, regardless of whether patients with cardiovascular diseases are combined or not, and prompt early intervention.

Protective Effect of Pravastatin on Myocardial Ischemia Reperfusion Injury by Regulation of the miR-93/Nrf2/ARE Signal Pathway.

PurposeThis research intended to study the mechanism of pravastatin in myocardial ischemia reperfusion (I/R) injury.Patients and MethodsAltogether 70 male rats were selected and grouped into Sham operation group (Sham group), ischemia reperfusion group (I/R group), pravastatin pretreatment group (I/R+P group), I/R+miR-93-mimics, I/R+P+miR-93-mimics, I/R+Nrf2 siRNA, and I/R+P+Nrf2 siRNA group. The myocardial function of each group was detected.ResultsMyocardial I/R injury could lead to abnormal myocardial enzyme activity, inflammatory reaction and oxidative stress. However, pravastatin could significantly inhibit the activity of myocardial enzymes, alleviate inflammatory reaction and inhibit oxidative stress reaction, thus playing a protective role. Furthermore, cell experiments showed that pravastatin can alleviate the injury of H9C2 myocardial cells caused by I/R, inhibit the apoptosis of myocardial cells, and lead to a significant reduction in pro-apoptotic genes Bax, caspase-3 and caspase-9 transcription levels, an obvious increase in anti-apoptotic gene Bcl-2, and an increase in cell activity. After I/R induced injury, miR-93 level was significantly up-regulated and Nrf2 level was down-regulated. Over-expression of miR-93 or inhibition of Nrf2 expression would lead to further aggravation of I/R myocardial injury, increase the apoptosis rate of cells and decrease the activity of myocardial cells. Pravastatin administration could inhibit miR-93, activate and promote Nrf2 in myocardial tissue, and promote protein expression of downstream regulatory genes HO-1 and NQO1. In the I/R model, pravastatin was given. Over-expression of miR-93 or silencing Nrf2 could reverse the therapeutic effect of pravastatin on I/R.ConclusionPravastatin acts as a protector on myocardial ischemia reperfusion injury by regulating miR-93/Nrf2/ARE signaling pathway.

Clinical significance and prognostic value of cellular immunity, inflammatory factors and myocardial enzymes in septic shock

Objective To investigate the clinical significance of cellular immune function, inflammatory factors and myocardial enzyme detection in evaluation of prognosis of septic shock, so as to provide a reference for clinical diagnosis and treatment of septic shock. Methods From June 2015 to June 2018, 73 patients with septic shock treated in the First People's Hospital of Yongkang were selected as the research subjects.According to the 28d prognosis after the patients entered the ICU, the patients were divided into the death group and the survival group.Another 67 cases of health examination from June 2015 to June 2018 were selected as control group.The changes of T lymphocyte subsets includingCD3, CD4 and CD8 were measured by BD FACSCanto I I flow cytometry, the content of procalcitonin(PCT) was determined by immunoluminescence assay, the content of C-reactive protein(CRP) was determined by immunoturbidimetry, and the content of creatine kinase MB(CK-MB), cardiac troponin I(cTnI) and lactate dehydrogenase(LDH) was determined by enzymatic kinetics. Results The APACHE Ⅱ score and MODS score of the survival group and the death group were higher than those of the control group [(2.20±0.61)points and (4.86±1.29)points]. The APACHE Ⅱ score and MODS score of death group [(16.45±4.28)points and (27.63±4.97)points] were higher than those of survival group [(9.84±2.45)points and (19.84±3.28)points](all P<0.05). The CD3+, CD4+ and CD4+/CD8+ in the survival group and the death group were significantly lower than those in the control group[(71.32±6.96)%, (42.63±4.26)%, (1.67±0.31)%](all P<0.05). The contents of PCT and CRP in the survival group and the death group were higher than those in the control group [(0.19±0.03)ng/mL and (2.19±0.76)mg/L], and the contents of PCT [(15.93±3.26)ng/mL] and CRP [(184.32±29.80)mg/L] in the death group were higher than those in the survival group [(6.87±1.94)ng/mL and (69.49±17.42)mg/L] (all P<0.05). The CK-MB content in the survival group and the death group of septic shock was lower than that in the control group [(1.97±0.21)μg/L], and the cTnI and LDH contents were higher than that in the control group [(0.03±0.01)μg/L and (168.93±16.52)U/L], the content of CK-MB [(0.68±0.10)μg/L] in the death group was lower than that in the survival group [(1.27±0.13)μg/L], while the contents of cTnI [(0.39±0.06)μg/L] and LDH [(384.52±39.89)U/L] in the death group were lower than those in the survival group [(0.17±0.04)μg/L and (257.18±25.47)U/L] (P<0.05). Conclusion The immune function of the patients with septic shock is obviously reduced, there are obvious inflammatory reactions and abnormal myocardial enzymes, and the detection of cellular immune function, inflammatory factors and myocardial enzymes can be used as an effective index to judge the shock of septic shock. Key words: Shock, septic; Immunity, cellular; C-reactive protein; Creatine kinase, MB form; Troponin I; Lactate dehydrogenases; Prognosis

Analysis of blood arsenic concentration and safety of arsenic-containing compound Qinghuang powder in patients with myelodysplastic syndrome

Objective To analyze the blood arsenic concentration and the safety of compound Qinghuang powder (compound QHP) in patients with myelodysplastic syndrome (MDS). Methods A total of 45 MDS patients received treatment with compound QHP (the treatment group, n=45). The concentration of blood arsenic in different time was determined by atomic fluorescence spectrometry. The clinical safety of compound QHP was evaluated by analyzing the symptoms of adverse reaction and organ function. The comparison were MDS patients with Qinghuang powder (QHP group, n=47) and healthy people. Results There was no significant difference of the blood arsenic concentration between the treatment group and the healthy control group (P=0.450), while after the treatment for 1 month those concentrations significantly increased (P=0.000). There were no significant difference between the blood arsenic concentration after treatment for 1, 3, and 6 months (P=0.240). The incidence of adverse reaction in the treatment group was significantly lower than that in QHP group(χ2=4.720, P=0.030). The incidence of adverse reactions in the digestive tract was significantly lower in the treatment group than that in QHP group (χ2=4.650, P=0.034). The blood arsenic concentration of patients with abdominal pain diarrhea was significantly lower than those without abdominal pain diarrhea (P=0.020). Before treatment in the compound QHP group, there were 21 cases with increased myocardial enzymes, 10 cases with abnormal liver function and 4 cases with renal dysfunction, respectively. After treatment at 6th month, these indicators returned to normal with 7 cases of myocardial enzymes, 6 cases of liver function and 1 case of renal function, respectively. There was no new case with abnormal myocardial enzymes, liver function and renal dysfunction, respectively. Conclusions Arsenic could be absorbed in the digestive tract into blood in MDS patients after treatment with arsenic-containing compound QHP, and the blood arsenic concentration remained stable during the course of treatment. The adverse reactions were mainly mild gastrointestinal symptoms, but no heart, liver or renal function damage was observed. The incidence of abdominal pain diarrhea in patients treated with compound QHP was significantly lower than that with QHP. Key words: Myelodysplastic syndromes; Realgar; Arsenicals; Patient Safety

Myocardial protective effect of L-carnitine in children with hand, foot and mouth disease caused by Coxsackie A16 virus

To investigate the myocardial protective effect of L-carnitine in children with hand, foot and mouth disease (HFMD) caused by Coxsackie A16 virus and possible mechanisms. A total of 60 HFMD children with abnormal myocardial enzyme after Coxsackie A16 virus infection were enrolled and randomly divided into L-carnitine group and fructose-1,6-diphosphate group (fructose group), with 30 children in each group. The two groups were given L-carnitine or fructose diphosphate in addition to antiviral and heat clearance treatment. Another 30 healthy children who underwent physical examination were enrolled as control group. The changes in myocardial zymogram, malondialdehyde (MDA), superoxide dismutase (SOD), and apoptosis factors sFas and sFasL after treatment were compared between groups. There was no significant difference in treatment response between the L-carnitine group and the fructose group (P>0.05). One child in the fructose group progressed to critical HFMD, which was not observed in the L-carnitine group. Before treatment, the L-carnitine group and the fructose group had significantly higher indices of myocardial zymogram and levels of MDA, sFas, and sFasL and a significantly lower level of SOD than the control group (P<0.05), while there were no significant differences in these indices between the L-carnitine group and the fructose group (P>0.05). After treatment, the L-carnitine group and the fructose group had significant reductions in the indices of myocardial zymogram and levels of MDA, sFas, and sFasL and a significant increase in the level of SOD (P<0.05); the fructose group had a significantly higher level of creatine kinase (CK) than the control group and the L-carnitine group, and there were no significant differences in other myocardial enzyme indices, MDA, sFas, and sFasL between the L-carnitine group and the fructose group, as well as between the L-carnitine and fructose groups and the control group (P>0.05). SOD level was negatively correlated with aspartate aminotransferase, lactate dehydrogenase (LDH), CK, and creatine kinase-MB (CK-MB) (r=-0.437, -0.364, -0.397, and -0.519 respectively; P<0.05), and MDA level was positively correlated with LDH and CK-MB (r=0.382 and 0.411 respectively; P<0.05). L-carnitine exerts a good myocardial protective effect in children with HFMD caused by Coxsackie A16 virus, possibly by clearing oxygen radicals and inhibiting cardiomyocyte apoptosis.

Clinical efficacy and safety of compound Qinghuang powder for treatment of myelodysplastic syndromes and its association with blood arsenic concentration

Objective To analyze the clinical efficacy and safety of compound Qinghuang powder (compound QHP) for treatment of myelodysplastic syndromes (MDS) and its association with blood arsenic concentration (BAC). Methods 40 patients with MDS were treated with compound QHP, and the clinical efficacy, safety, and its association with BAC were evaluated after treatment for 6, 9 months, respectively. Results After treatment for 6 months, the rate of hematology improvement was 32.5% (13/40), and the effective rate was 87.5% (35/40). 21 cases depended on the blood transfusion before treatment, after treatment 6 cases completely got rid of blood transfusion and the blood transfusion of another 6 cases was decreased by more than 50%. The absolute neutrophil count was increased from (0.50±0.13)×109/L to (0.93±0.33)×109/L (t= 4.130, P= 0.000 8). The hemoglobin content was increased from (71.06±14.82) g/L to (80.41±27.35) g/L (t= 2.233, P= 0.032 1). After treatment for 9 months, 76.2% (16/40) of the patients got rid of blood transfusion or blood transfusion reduction was more than 50%. The platelet count was increased from (45.04±24.38)×109/L to (60.65±29.46)×109/L (t= 2.241, P= 0.033 5). The incidence of abdominal pain and diarrhea after treatment for 1, 3 and 6 months were 12.5% (5/40), 10.0% (4/40) and 5.0% (2/40), respectively, all belonging to mild level. Before treatment, there were 12 patients with abnormal liver function, including 6 cases back to normal after treatment, and 6 cases of significantly relieved, without new case with abnormal liver function. Before treatment, there were 10 cases with abnormal myocardial enzymes, including 1 cases back to normal after treatment and 9 cases significantly relieved, without new case with abnormal myocardial enzymes. No patient with abnormal renal function was observed before and after treatment. The BAC was (7.71±5.65) μg/L before treatment, which was significantly lower than that of 1, 3 and 6 months [(29.27±9.07) μg/L, (27.79±10.18) μg/L and (31.98±12.55) μg/L respectively, all P 0.05). The BAC in efficacy group [(33.48±12.56) μg/L] was significantly higher than that in non-efficacy group [(21.46±6.00) μg/L] (t= 2.089, P= 0.035). 12.5% (5/40) of the patients had mild gastrointestinal side effects after treatment for 1 month, while the BAC of them [(16.93±1.80) μg/L] was significantly lower than that in patients without gastrointestinal side effects [(31.78±1.39) μg/L, P < 0.000 1]. The occurrence rate of abdominal pain and diarrhea was decreased after treatment for 3 and 6 months, while the BAC was increased gradually. Conclusions Compound QHP is effective in the treatment of MDS with mild adverse reactions. There is no damage to the heart, liver, and renal function. Besides, it shows that reducing the gastrointestinal adverse reactions and maintaining the effective concentration of BAC play a significant role in the effect of compound QHP in the treatment of MDS. Key words: Myelodysplastic syndromes; Arsenicals; Treatment outcome; Safety

Clinical significance of the detection of myocardial enzymes and high sensitive C-reactive protein in chil-dren with herpangina

Objective To evaluate the clinical significance of myocardial enzymes and high sensitive C-reactive protein（ hs-CRP） in children with herpangina. Methods A total of 80 children with herpangina（ obser-vation group,n=80）,at the same time,50 healthy children as control group（n=50）were assigned for the detec-tion of myocardial enzymes（AST,LDH,CK,CK-MB）and hs-CRP. Results The elevated CRP levels were found in 45（56. 25%）patients of observation group and 2（4%）patients of the control group,showing statistical significance（χ2 =31. 55,P〈0. 01）. Abnormal myocardial enzyme levels were observed in 59（73. 75%）cases, which included AST 51. 6%, CK 40. 1%, CK-MB 21. 4%, LDH 72. 2%. Abnormal myocardial enzyme levels were observed in 6（12%） cases of control group,which included AST l6%,CK 10%,CK-MB 4% and LDH 12%. The significant differences were observed between the two groups （ P〈0. 01 ） . Conclusion Herpangina children may have different degrees of myocardial damage. Myocardial enzymes and hs-CRP are useful indicators for myocardial injury which may effectively provide reference for clinical diagnosis and treatment. Key words: Herpangina; Myocardial enzymes; High sensitivity C-reactive protein; Myocardial injury

Analysis of clinical features of pregnant women with hypertrophic cardiomyopathy

To discuss the clinical features of pregnant women with hypertrophic cardiomyopathy (HCM). There were 28 patients with HCM who delivered in Renji hospital of Shanghai Jiaotong University from January 2000 to August 2012. Clinical data were analyzed, including diagnosis, cardiac functional grading, gestational weeks of delivery, delivery mode, birth weight, Apgar scores, etc. (1) Of all the 28 patients, 14 (50%) were diagnosed before pregnancy and others (50%) were diagnosed during pregnancy.(2) Four cases were obstructive HCM (14%), 3 with cardiac function grade I and 1 with grade II. Twenty four cases were non-obstructive HCM (86%), 14 with cardiac function grade I, 9 with grade II and 1 with grade IV. (3) Of all the 28 patients, 4 had family history, 18 (64%) had clinical symptoms or signs which occurred in 8-32 gestational weeks. Twenty-three cases had abnormal ECG (82%). Among them 21 had non-obstructive HCM (88%), with average interventricular septal thickness of (22 ± 3) mm. The other 2 patients had obstructive HCM, with average interventricular septal thickness of (23 ± 4) mm.7 patients (7/28, 25%) had mild-to-moderate pulmonary hypertension [6 with non-obstructive HCM (6/24, 25%) ], and 10 patients had abnormal myocardial enzyme spectrum or troponin levels [9 with non-obstructive HCM (9/24, 38%) ].(4) Among all the patients, only one had vaginal delivery and others received cesarean section. Twenty-two patients had term pregnancies and 6 had preterm birth. The average gestational weeks of delivery in non-obstructive HCM and obstructive HCM were (36.5 ± 2.5) and (38.5 ± 0.4) weeks, respectively. The average birth weight of neonates were (2684 ± 563) and (3164 ± 321) g, and Apgar scores were 9.9 and 10 (10 minutes) respectively. Patients transferred to NICU after delivery were 8 and 0. There was 1 maternal death (with non-obstructive HCM whose ejection fraction was only 26%) and no perinatal death. More attention should be paid to the clinical signs and abnormal ECG.HCM could be definitely diagnosed by timely echocardiography. Patients with hypertrophic cardiomyopathy were mainly non-obstructive HCM, with cardiac function grade I and II. Monitoring the change of ejection fraction during pregnancy would help. Perinatal outcomes were fine.

Time factor in reversibility of myocardial metabolic changes in hemorrhagic shock.

Summary1. The abnormal changes that occur in the % extraction of pyruvate and lactate by the heart in shock are returned to normal if a blood transfusion is given within 1 to 1 1/4 hours of onset of shock. If the shock period is prolonged to 3 or more hours, the changes are irreversible to transfusion. 2. The % extraction of O2 by the heart, which is markedly elevated in hemorrhagic shock, is returned to normal after an infusion of blood given following 1 to 1 1/4 hours of shock. In contrast, if transfusion is given after more prolonged shock, the myocardial % extraction of O2 is depressed to abnormally low levels. It is suggested that this may be a reflection of depleted or abnormal myocardial enzyme systems after prolonged shock. 3. These findings support other biochemical, physiological, and pathological observations which point to irreversible myocardial damage as an important factor in the irreversibility of prolonged shock.