Probing ^{93m}Mo Isomer Depletion with an Isomer Beam

The isomer depletion of ^{93m}Mo was recently reported [Chiara et al., Nature (London) 554, 216 (2018)NATUAS0028-083610.1038/nature25483] as the first direct observation of nuclear excitation by electron capture (NEEC). However, the measured excitation probability of 1.0(3)% is far beyond the theoretical expectation. In order to understand the inconsistency between theory and experiment, we produce the ^{93m}Mo nuclei using the ^{12}C(^{86}Kr,5n) reaction at a beam energy of 559 MeV and transport the reaction residues to a detection station far away from the target area employing a secondary beam line. The isomer depletion is expected to occur during the slowdown process of the ions in the stopping material. In such a low γ-ray background environment, the signature of isomer depletion is not observed, and an upper limit of 2×10^{-5} is estimated for the excitation probability. This is consistent with the theoretical expectation. Our findings shed doubt on the previously reported NEEC phenomenon and highlight the necessity and feasibility of further experimental investigations for reexamining the isomer depletion under low γ-ray background.

[A longitudinal study of relationship between family conflict and suicidal behavior in adolescents]

Objective: To explore the relationship between family conflict and adolescent future suicidal behavior. Methods: A total of 7 072 adolescents who participated in the baseline survey and the first follow-up survey of Shandong Adolescent Behavior and Health Cohort were included in the analysis. They were sampled from 8 middle schools in 3 counties of Shandong province, China. A self-reported questionnaire was used to measure suicidal behavior, family conflict, depression, and demographic characteristics. Logistic regression model was used to analyze the relationship between family conflict and suicidal behavior. Results: In the baseline survey, the age of 7 072 subjects was (14.58±1.45) years, and boys and girls accounted for 50.0% respectively. 750 people (10.6%) had any suicidal behavior, of which 707 (10.0%), 258 (3.6%) and 190 (2.7%) had suicidal ideation, suicide planning and suicide attempt, respectively. The family conflict scores of the suicidal group were higher than those of the non-suicidal group. After adjusting for covariates, logistic regressions showed that family conflict was associated with increased risk of suicidal behavior (OR=1.05, 95%CI: 1.01-1.10), suicidal ideation (OR=1.05, 95%CI: 1.00-1.09), suicide planning (OR=1.08, 95%CI: 1.01-1.16) and suicide attempt (OR=1.10, 95%CI: 1.02-1.19). Further stratified by gender, results showed no significant association between family conflict and suicidal behavior in girls; the association of family conflict with suicidal behavior was more significant in boys, especially for suicidal ideation and suicide planning, and the OR value of the latter was higher than the former. The results were stable after sensitivity analysis in males. Conclusions: Family conflict might increase the risk of adolescent suicidal behavior, especially in males. Harmonious family environment and good family atmosphere are of great significance to adolescent suicide prevention and control.

[Non-suicidal self-injury and exposure to suicidal behaviors among Chinese adolescents: a longitudinal study]

Objective: Non-suicidal self-injury (NSSI) in adolescents appeared prevalent and multifactorial. This study was to examine the associations between exposure to suicidal behaviors and NSSI in the Chinese adolescents. Methods: Participants included for analyses were 5 154 adolescent students who participated in the baseline survey in 2015 and the first follow-up survey in 2016 of the Shandong Adolescent Behavior and Health Cohort, but with no history of NSSI at the baseline survey. A self-administered structured questionnaire was used to collect data on demographics, behavioral and emotional problems, lifetime and last-year NSSI. Data on the history of exposure to suicide attempt or death of a family member, friend, or close acquaintance were also collected. Multivariate logistic regression methods were used to examine the associations between exposure to suicidal behaviors and NSSI. Results: In the baseline survey, mean age of the 5 154 participants was (14.49±1.48) years, with 48.5% of the participants as girls. Of the participants, 9.0% reported having been exposed to suicidal behaviors, including 6.0% reported to suicide attempt, 4.9% to suicide death, 7.3% to suicidal behaviors of friends/close acquaintances, and 3.1% to suicidal behaviors of relatives. The prevalence rates of NSSI in the last year were significantly higher in adolescents who had been exposed to suicidal behaviors than those who had not (P<0.05). Results from the multivariate logistic regressions showed that exposure to suicide death (OR=1.91, 95%CI: 1.22-3.01) or to suicidal behaviors of relatives (OR=1.79, 95%CI: 1.02-3.12) were both significantly associated with the increased risk of NSSI. Conclusions: Experiences related to exposure to suicide-death or suicidal behaviors of relatives were associated with increased risk of NSSI in adolescents. After the suicide events, psychological counseling and health education programs set for high-risk groups were helpful in promoting physical and mental health and preventing the attempt of self-injury in teenagers.

[The relationship between mental stimulation level of life events and suicide attempt of rural residents in Shandong Province]

Objective: To explore the relationship between the level of mental stimulation and the suicide attempts of rural residents in Shandong Province. Methods: A 1:1 matched case-control study was designed to collect 1 200 cases from a survey of three suicide attempts in rural areas of Shandong Province. Controls were selected according to the following matched factors: age difference within 3 years, same gender, same village or neighboring village, no blood relationship, no suicide history. The basic characteristics of all subjects were collected through the questionnaire, and the level of mental stimulation of life events was measured. Multivariate conditional logistic regression model was used to analyze the relationship between the level of mental stimulation of life events and suicide attempts. Results: The mean age of the case group and the control group was both (36.6±0.3) years old, and 35.8% (430/1 200) were males in each group. The low-medium level of mental stimulation of negative life events in the case group was 16.7% (200/1 200) and 61.7% (740/1 200), respectively, which was higher than that in the control group, about 2.5% (30/1 200) and 29.3% (352/1 200) (all P values <0.05), respectively. A total of 11.1% (133/1 200) of the case group had positive life events, which was lower than that of the control group [16.8% (201/1 200)] (all P values<0.05). Multivariate logistic regression model analysis showed that after the adjustment of gender, age, place of residence, education level, marital status, occupation, family income, somatic disease, mental disorders, family history of suicide, and opposite life events, the low-medium and high level of mental stimulation of negative life events were risk factors for suicide attempts, with OR (95%CI) as 5.88 (4.53-7.64) and 13.94 (8.15-23.86), respectively. Mental stimulation of positive life events was protective factor of suicide attempts, with OR (95%CI) as 0.58 (0.41-0.82). Conclusion: Mental stimulation of negative and positive life events were risk and protective factors for suicide attempts.

Effectiveness of olfactory ensheathing cell transplantation for treatment of spinal cord injury

The aim of this study was to determine the effectiveness and safety of transplantation of olfactory ensheathing cells for functional repair of the spinal cord. An olfactory bulb was obtained from a 4- to 5-month-old aborted fetus, and it was digested into single olfactory ensheathing cells and then cultured and purified for 1 to 2 weeks. Under general anesthesia, these single-cell suspensions of olfactory ensheathing cells were injected into the corresponding spinal injury site with 0.45-mm-diameter injections. The American Spinal Injury Association (ASIA) Impairment Scale was used to evaluate spinal function. A total of 15 patients (12 men, 3 women; age range, 18-56 years; mean age, 40) were admitted for obsolete spinal injuries. Spinal functions of the 15 patients were observed and followed postoperatively for a period ranging from 2 weeks to 1 month. All the 15 patients exhibited improvements in spinal function, and the improvement tendencies continued. Twelve patients had obvious spinal function improvement, and three had slight improvement according to the ASIA scale, with an obvious difference between preoperation and postoperation measures (P < 0.05). No fevers, infections, functional deteriorations, or deaths were seen. Thus, transplantation of olfactory ensheathing cells promoted spinal and neurofunctional recovery in patients with malignant spinal injuries, and this therapeutic method was safe.

LV segmentation through the analysis of radio frequency ultrasonic images

LV segmentation is often an important part of many automated cardiac diagnosis strategies. However, the segmentation of echocardiograms is a difficult task because of poor image quality. In echocardiography, we note that radio-frequency (RF) signal is a rich source of information about the moving LV as well. In this paper, first, we will investigate currently used, important RF derived parameters: integrated backscatter coefficient (IBS), mean central frequency (MCF) and the maximum correlation coefficients (MCC) from speckle tracking. Second, we will develop a new segmentation algorithm for the segmentation of the LV boundary, which can avoid local minima and leaking through uncompleted boundary. Segmentations are carried out on the RF signal acquired from a Sonos7500 ultrasound system. The results are validated by comparing to manual segmentation results.

New genotype of avian influenza H5N1 viruses isolated from tree sparrows in China

The 2004 outbreaks of highly pathogenic avian influenza H5N1 disease in China led to a great poultry loss and society attention. A survey of avian influenza viruses was conducted on tree sparrows (Passer montanus) collected in China in 2004. Four viruses were isolated from free-living tree sparrows. The results of the whole-genome analysis indicated that an H5N1 virus with a new genotype is circulating among tree sparrows. The hemagglutinin and neuraminidase genes of the new genotype were derived from Gs/Gd/96-like viruses and the nuclear protein gene descended from the 2001 genotype A H5N1 viruses, while the other inner genes originated from an unknown influenza virus. In experimental infection, all four viruses were highly pathogenic to chickens but not pathogenic to ducks or mice. The four tree sparrow viruses were different from the 2003 tree sparrow strain (genotype Z) in Hong Kong. The results suggested that H5N1 viruses might be distributed widely in tree sparrows.

Improvement of rejection-induced diastolic abnormalities in rat cardiac allografts with inducible nitric oxide synthase inhibition

OBJECTIVE

Inhibition of inducible nitric oxide synthase (nitric oxide II) activity has been proposed as a method to attenuate capillary leak and edema during rejection of heterotopically transplanted rat hearts. Myocardial edema has previously been implicated in diastolic dysfunction during allograft rejection. Accordingly, we tested the hypothesis that inducible nitric oxide synthase inhibition with aminoguanidine would alleviate left ventricular stiffening and myocardial edema formation in 4-day heterotopic rat heart allografts.

METHODS

Passive left ventricular filling was studied in American Cancer Institute Lewis rats receiving heterotopic heart transplants receiving either aminoguanidine, a selective nitric oxide synthase inhibitor (n = 6); dexamethasone (1 mg. kg(-1). d(-1) administered subcutaneously) for 4 days after transplantation (n = 6); or intravenous saline solution (n = 6). American Cancer Institute-to-American Cancer Institute isografts (n = 6) were used as controls.

RESULTS

Serum nitrite/nitrate levels in the aminoguanidine group (18 +/- 3 mmol/L) and dexamethasone group (22 +/- 4 mmol/L) were reduced versus the intravenous saline group (144 +/- 36 mmol/L [SEM]) to levels seen in controls (25 +/- 9 mmol/L). Left ventricular volume at 15 mm Hg for the aminoguanidine group was increased versus that for the intravenous saline solution group, similar to that for controls, and reduced versus dexamethasone-treated animals. Myocardial water content for the aminoguanidine-treated animals (78.3% +/- 0.4%) was similar to those of intravenous saline-treated animals (78.0% +/- 0. 3%) but greater than those of controls (77.1% +/- 0.2%) and dexamethasone-treated animals (76.7% +/- 0.3%).

CONCLUSIONS

Nitric oxide II inhibition with aminoguanidine minimizes the reduction in left ventricular filling that is seen with allograft rejection through a mechanism that is not associated with attenuation of myocardial edema.

Coronary perfusate composition influences diastolic properties, myocardial water content, and histologic characteristics of the rat left ventricle

BACKGROUND

Recent studies found that edema, histology, and left ventricular diastolic compliance exhibit quantitative relationships in rats. Edema due to low osmolarity coronary perfusates increases myocardial water content and histologic edema score and decreases left ventricular filling. The present study examined effects of perfusate osmolarity and chemical composition on rat hearts.

METHODS

Arrested American Cancer Institute (ACI) rat hearts (4 degrees C) were perfused with different cardioplegia solutions, including Plegisol (289 mOsm/L), dilute Plegisol (172 mOsm/L), Stanford solution (409 mOsm/L), and University of Wisconsin solution (315 mOsm/L). Controls had blood perfusion (310 mOsm/L). Postmortem left ventricular pressure-volume curves and myocardial water content were measured. After glutaraldehyde or formalin fixation, dehydration, and paraffin embedding, edema was graded subjectively.

RESULTS

Myocardial water content reflected perfusate osmolarity, being lowest in Stanford and University of Wisconsin solutions (p<0.05 versus other groups) and highest in dilute Plegisol (p<0.05). Left ventricular filling volumes were smallest in dilute Plegisol and Plegisol (p<0.05). Osmolarity was not a major determinant of myocardial edema grade, which was highest with University of Wisconsin solution and dilute Plegisol (p<0.05 versus other groups).

CONCLUSIONS

Perfusate osmolarity determined myocardial water content and left ventricular filling volume. However, perfusate chemical composition influenced the histologic appearance of edema. Pathologic grading of edema can be influenced by factors other than osmolarity alone.

Pressure volume curves in arrested heterotopic rat heart isografts: role of improved myocardial protection

BACKGROUND

To minimize decreases in left ventricular (LV) compliance immediately after rat heart transplantation, we tested several different methods of myocardial protection.

MATERIALS AND METHODS

Five groups of ACI rat hearts (n = 6 each) were arrested by coronary perfusion with 5 ml of UW (University of Wisconsin), UW-BDM (UW with 2,3-butanedione monoxime), CU (Columbia University), or CU-BDM solution or by LV injection of potassium chloride and Ringer's lactate immersion (KCl/RL). After abdominal isografting and blood reperfusion for 15 min, transplanted hearts (TxH) were arrested and excised. Diastolic LV pressure-volume curves (LVPVCs) were correlated with myocardial water content (MWC). Native hearts (NH) were arrested identically to TxH and maintained at 4 degrees C by immersion. LVPVCs were measured at 15-min intervals for 90 min.

RESULTS

In three of four pressure intervals at Time 0, normalized LV volume (LVV) was smaller (P < 0.05, ANOVA) in KCl/RL native hearts than in the four perfusion groups. LVV decreased significantly in NH after 45-75 min; LVV decreased similarly with time in all groups. In TxH, postarrest LVVs were higher with UW-BDM, CU-BDM, and CU than with UW or KCl/RL (P < 0.05, ANOVA). Expressing LVV of TxH as a percentage of NH, UW-BDM, CU, and CU-BDM provided qualitatively better diastolic properties than KCl/RL and UW.

CONCLUSIONS

Thus rat LVPVCs can be improved after heart transplantation with alternative strategies of myocardial protection. KCl arrest decreases LV filling volume in this model and should be avoided.

Attenuation of reperfusion injury with probucol in the heterotopic rat cardiac isograft

BACKGROUND

We tested the hypothesis that pretreatment with the antioxidant probucol attenuates reperfusion-induced diastolic abnormalities in the heterotopic rat cardiac isograft.

METHODS

American Cancer Institute rats (n = 48) were divided into 6 groups. Hearts were arrested by coronary perfusion with 3 ml 4 degrees C University of Wisconsin solution at 60 mmHg. Eighteen donor hearts were divided into 3 groups of 6 and arrested either 1 hour after intraperitoneal injection of 3 ml oil with (Prob Tx) or without (Oil Tx) probucol (300 mg/kg) or without injection (Ctrl Tx). After a 90 minute storage period, abdominal isografting was performed with a total ischemic time of 2 hours. Following 15 minutes of blood reperfusion, donor hearts were rearrested and excised. Recipients' native hearts (NH, n = 18) were also arrested. Two additional groups with (Prob NR, n = 6) and without (Ctrl NR, n = 6) probucol pretreatment were arrested and subjected to 2 hours of ischemia without reperfusion. Postmortem LV pressure-volume curves and myocardial water content (MWC) were measured.

RESULTS

At each pressure interval normalized LV volume (LVV) was significantly greater for Prob Tx than Oil Tx or Ctrl Tx. All isograft groups had significantly lower LVV at all pressure intervals and higher MWC than non-transplanted hearts.

CONCLUSIONS

Pretreatment with probucol attenuates reperfusion-induced decreases in LVV in the heterotopic rat heart isograft model. Probucol, which is orally active in humans, merits further study for its potential to improve myocardial protection during cardiac surgery.

Conductance artifacts in a novel in vitro model of ventriculothoracic electrical coupling

The utility of open chest conductance (COND) ventriculography is limited by artifacts altering the relationship between COND and left ventricular (LV) volume. Pressure-COND loops often lean to the left during LV volume reduction by caval occlusion. Time varying alterations in the pericardial-LV contact area affect electrical coupling in the open chest during the cardiac cycle, producing COND artifacts. In this study, an open-mediastinum model was constructed. Components represented the LV, blood, pericardium, and thoracic contents. Varying ventriculothoracic coupling was simulated by changing the volume of pericardial saline (0, 30, 60 ml). Raw dual field COND was repeatedly (n = 20) compared with volumes of normal saline from 60 to 120 ml at 5 ml intervals. Groups were compared by linear regression and repeated measures ANOVA. Artifacts significantly (p < 0.01) altered parallel COND, indicated by the y-intercept, with the exception of 0 versus 30 ml. The slope constant also changed significantly, with the exception of 30 versus 60 ml. These results suggest that variable pericardial-LV contact can cause time varying artifacts in COND in the open chest. Therefore, posterior insulation may reduce artifacts in COND ventriculography and should be tested for this effect.

A novel arresting solution for study of postmortem pressure--volume curves of the rat left ventricle

OBJECTIVE

We have found diastolic properties of the rat heart extremely sensitive to the method used to induce arrest. Accordingly, we sought to develop a reliable solution for measuring the LV pressure-volume relationship (LVPVR) in the rat.

MATERIALS AND METHODS

The study had five phases: (i) K120Na100, consisting of KCl (120 mEq/L) in NaCl (100 mEq/L) diluted with distilled water was developed in preliminary experiments. (ii) ACI rats were arrested with 3 cc of 4 degreesC KCl (n = 6) or K120Na100 (n = 6) infused into the aortic root. The LVPVR was expressed as normalized volume (Vn) at standardized pressures. Myocardial water content (%MWC) was determined. (iii) Six hearts were arrested with K120Na100 and LVPVRs observed over 1 h. (iv) Four hearts were instrumented with sonomicrometry crystals to compare in vivo and postmortem pressure diameter data. (v) The relation between body weight and dry heart weight was determined in 48 animals.

RESULTS

In hearts arrested with KCl, mean Vn at pressures of 10, 15, and 20 mmHg (206 +/- 26, 306 +/- 21, and 336 +/- 25 microl, respectively) was significantly reduced vs K120Na100 hearts (345 +/- 11, 407 +/- 12, and 472 +/- 18 microl) (P < 0.05). Mean %MWC changed insignificantly. Vn at 20 mm Hg became significantly smaller vs initial data 60 min after arrest with K120Na100 (P < 0.05, ANOVA). No differences between in vivo and postmortem mean normalized diameter were observed. The correlation coefficient for the relation between body weight and dry heart weight was 0.80. Conclusions. K120Na100 at 4 degreesC reliably preserves LV diastolic properties in the rat heart for 30 min. Normalization of LV volume to body weight is justified.

Effect of improved myocardial protection on edema and diastolic properties of the rat left ventricle during acute allograft rejection

BACKGROUND

Studies of myocardial edema and diastolic dysfunction in rat heart transplantation have been flawed by ischemic injury. This study uses improved methods to prevent ischemic contracture.

METHODS

Hearts of 30 ACI rats were transplanted into the abdomen of Lewis rats by use of cold University of Wisconsin solution for improved preservation. Left ventricular diastolic properties were expressed as volume at standardized pressure intervals.

RESULTS

On posttransplantation day 3, mean left ventricular volume at 15 mm Hg in allografts (290 +/- 9 microl, SEM) was not significantly different vs isografts (299 +/- 32 microl), allografts on day 0 (337 +/- 28 ml) or day 1 (324 +/- 20 microl), or native hearts (334 +/- 19 microl). However, volume was reduced to 173 +/- 17 microl on day 4 and to 70 +/- 23 microl on day 5 (p < 0.05). Similar findings were obtained for volume at 5 and 10 mm Hg. Allograft myocardial water content on day 3, 76.3% +/- 5%, similar to allografts on day 0 and 1 and to isografts on day 3, increased to 77.6% +/- 8% on day 4 (NS) and 79.4% +/- 6% on day 5 (p < 0.05 vs day 0). Histologically, rejection in allografts was mild on day 3, moderate on day 4, and severe on day 5.

CONCLUSIONS

Reduced left ventricular filling volume during rejection is only partially explained by edema. Abnormalities of diastolic properties previously attributed to the unloaded state of nonworking heart models may actually reflect inadequate peritransplantation myocardial protection.

Reversal of iatrogenic myocardial edema and related abnormalities of diastolic properties in the pig left ventricle

OBJECTIVE

This study examines the resolution of iatrogenic edema and related changes in systolic and diastolic properties in the intact pig left ventricle.

METHODS

The coronary arteries were perfused for 50 to 60 seconds with diluted blood (hematocrit value 10% +/- 1%, edema group, n = 5) or whole blood (hematocrit value 28% +/- 1%, control group, n = 6) infused into the aortic root during aortic crossclamping in conditioned, anesthetized pigs. After whole blood reperfusion, preload reduction by vena caval occlusion was used to define systolic and diastolic properties at 15-minute intervals. Left ventricular pressure and conductance, aortic flow, and two-dimensional echocardiography were recorded.

RESULTS

Left ventricular mass (wall volume) in the edema group increased significantly compared with that in control pigs after crossclamp removal. Mass returned to preperfusion levels after 45 minutes. The ventricular stiffness constant (beta) increased significantly in the edema group versus the control group, returning to baseline by 30 minutes. The diastolic relaxation constant (tau) and base constant (alpha) did not differ between groups. There was no significant change in contractility.

CONCLUSION

Increases in left ventricular mass and diastolic stiffness induced by coronary perfusion with hemodiluted blood resolve after 45 minutes of whole blood perfusion in pigs. This study defines physiologic effects of edema in the normal heart while eliminating most common confounding experimental errors.

A method for detecting changes in left ventricular mass during variations in filling volume

Two-dimensional echocardiography has been useful for measuring changes in left ventricular mass (LVM) at constant left ventricular end-diastolic volume (LVEDV). Two-dimensional echocardiographic measurement of LVM changes during variations in LVEDV requires definition of the LVM/LVEDV relation because two-dimensional echocardiographic measurements could be affected by asymmetrical redistribution of LVM. Echocardiography data were recorded during caval occlusions in pigs (n = 6). Results confirm that A(M) (left ventricular [LV] short-axis cross-sectional [SACS] wall thickness area), was inversely related to AL (LV SACS lumen area), the average relation being A(M) = -0.33 AL + 20 (r = 0.82 +/- 0.05 [SE]). In addition, we developed a model that computes normal relation between LV SACS wall thickness area (AMc) and LV SACS lumen area (ALc) over a physiologic range of LVEDVs based on a single end-diastolic two-dimensional echocardiographic SACS image. Each computed relation corresponds uniquely to an LVM (LVMc). Theoretically, a difference between AMc/ALc relation before an intervention and the computed relation after the intervention would indicate a change in LVM. To test the utility of this model, edema was induced in a second group of pigs (n = 6) by coronary hemodilution. Two conditions were tested: pre-edema and edema. Serial AMc/ALc and LVMc were computed. Pre-edema and edema AMc were compared at matched LV SACS end-diastolic areas (ALc = 15 cm2). Results showed a significant increase in LVMc (two-tailed p value < 0.05), as observed by two-dimensional echocardiography. We conclude that the A(M) and AL are inversely related. This relation is useful for detecting alterations in LVM during variations in LVEDV.

Diastolic properties, myocardial water content, and histologic condition of the rat left ventricle: effect of varied osmolarity of a coronary perfusate

BACKGROUND

Although myocardial edema is known to impair diastolic filling of the left ventricle, the interrelation of edema, histologic condition, and function has not been quantitated sufficiently for extrapolation to studies of multifactorial influences on diastolic properties.

METHODS

Accordingly, ACI rat hearts arrested at 4 degrees C underwent coronary artery perfusion with a cardioplegia solution that was either unaltered (288 mOsm/L, P288 group, n = 6), diluted (144 mOsm/L, P144 group, n = 6), or concentrated (380 mOsm/L, P380 group, n = 6). Postmortem left ventricular pressure-volume curves and myocardial water content were measured. Myocardial samples were fixed in varying dilutions of glutaraldehyde. After dehydration and paraffin embedding, edema was graded subjectively (0 to 5), and myocardial interstitial spaces were determined by use of a semiquantitative method.

RESULTS

Mean normalized left ventricular filling volume at 20 mm Hg filling pressure in the P144 group, 189 +/- 16 microliters (SEM), was reduced versus both the P288 (278 +/- 26 microliters) and the P380 (332 +/- 18 microliters) groups (p < 0.05, ANOVA). Mean myocardial water content in the P144 group, 80.7% +/- 1%, was increased versus the P380 (76.7% +/- 0.4%, p < 0.05) but not versus the P288 group (78.4% +/- 0.8%). In hearts preserved with 2.5% glutaraldehyde, mean edema grade and interstitial space in the P144 group (4.0 +/- 0.3) were increased versus the P380 (1.8 +/- 0.3, p < 0.05) but not the P288 group (2.7 +/- 0.5). Derived linear regressions relate water content to filling volume and histologic condition.

CONCLUSIONS

Coronary perfusate osmolarity is thus associated with predictable changes in myocardial water content, left ventricular filling volume, and edema. These correlations allow definition of new hypotheses for the study of cardiac allograft rejection in patients and experimental animals.

Retrograde coronary perfusion: effects on iatrogenic edema and diastolic properties

BACKGROUND

The relative merits of antegrade infusion and retrograde infusion of cardioplegic solution in terms of heart weight, myocardial water content, and ventricular diastolic properties are undefined. Accordingly, we compared antegrade and retrograde flow of hemodiluted blood in isolated, hypothermic porcine hearts.

METHODS

After cardiectomy, 1 L of cold heparinized blood diluted with lactated Ringer's solution to concentrations ranging from 100% lactated Ringer's to 50% lactated Ringer's and 50% blood was perfused in an antegrade (n = 6) or retrograde (n = 6) fashion at mean pressures of 62 +/- 2 mm Hg (+/- standard error of the mean) and 49 +/- 2 mm Hg, respectively. Heart weight, myocardial water content, and left ventricular pressure-volume relationships were obtained before and after perfusion.

RESULTS

In the comparison of measurements before and after perfusion, changes in heart weight (36 +/- 4 g versus 5 +/- 2 g; p < 0.05), myocardial water content (6.9% +/- 1.0% versus 2.5% +/- 0.4%; p < 0.01), and ventricular filling measured by normalized left ventricular volume at 10, 15, and 20 mm Hg were greater in the antegrade group.

CONCLUSIONS

In the isolated porcine heart, retrograde flow is distinguished from antegrade flow by less change in heart weight and myocardial water content and no diastolic dysfunction.

Electrical isolation of the heart. Stabilizing parallel conductance for left ventricular volume measurement

Modern indices of left ventricular function require accurate measurement of left ventricular volume (LVV). Although conductance catheter (COND) measurements of LVV have been found to be reproducible under steady state conditions in closed chest animals, after median sternotomy, measurements of LVV are subject to exaggerated variation in parallel conductance (alpha Vc) outside of the left ventricle. Current calibration methods for measuring alpha Vc include hypertonic saline injection and quantitative two dimensional echocardiography. Unfortunately, these methods are hampered by imprecision, since frequent changes in alpha Vc in the open chest make recalibration impractical. Accordingly, a latex wrap technique was developed to insulate the left ventricle from extracardiac sources of alpha Vc in the open chest. Anesthetized pigs (n = 5) underwent a median sternotomy with insertion of a 6 French COND-micromanometer combination catheter into the left ventricle. Three conditions were tested: 1) unaltered; 2) metallic retractor outside of the pericardium (metal); and 3) latex wrap between the metal and pericardium. Pressure/COND loops showed that the insulator improved the shape of the loops and decreased alpha Vc, as measured by an echo-area/COND relationship, whereas metal increased alpha Vc and produced artifacts in the loops. In conclusion, electrical isolation eliminates distortion of pressure/COND loops related to extracardiac sources of alpha Vc, therefore allowing for accurate COND measurements in the open chest.

Myocardial edema: comparison of effects on filling volume and stiffness of the left ventricle in rats and pigs

BACKGROUND

This study compared the adverse effects of crystalloid-induced myocardial edema on left ventricular (LV) compliance in small and large hearts.

METHODS

Plegisol (289 mOsm/L) was perfused into the coronary arteries of pigs (n = 8) and 1:1 dilute Plegisol (145 mOsm/L) into the coronary arteries of rats (n = 6). Pressure-volume relations, heart weight, and water content were then determined. The pressure-volume relations were compared using an LV volume at a pressure of 10 mm Hg.

RESULTS

Edema in rats was associated with significant (p < 0.05) increases in heart weight (1.1 +/- 0.0 g versus 1.4 +/- 0.1 g [average +/- standard error of the mean]) and water content (76.8% +/- 0.4% versus 81.3% +/- 0.8%), but an increase in LV stiffness (7.91 +/- 0.52 versus 9.27 +/- 1.42) and a decrease in the LV volume at 10 mm Hg (0.25 +/- 0.02 mL versus 0.14 +/- 0.05 mL) were not statistically significant. Edema in pigs was associated with statistically significant (p < 0.05) increases in LV stiffness beta (0.050 +/- 0.004 versus 0.072 +/- 0.008), heart weight (207 +/- 8 g versus 274 +/- 9 g), and water content (79.8% +/- 0.6% versus 85.3% +/- 0.6%) and a significant decrease in the LV volume at 10 mm Hg (88.4 +/- 5.8 mL versus 60.4 +/- 6.8 mL).

CONCLUSIONS

Myocardial edema is associated with an increase in water content and LV stiffness and a decrease in the LV volume at 10 mm Hg in both species. In rats, however, the water content is smaller in the control state and a more hypotonic perfusate is needed to induce a given degree of edema.

Validation of right and left ventricular conductance and echocardiography for cardiac function studies

BACKGROUND

Continuous estimation of left ventricular volume from instantaneous conductance has compared favorably with "gold standards," is less labor intensive, and provides real-time data. Little information exists, however, correlating right ventricular conductance with such gold standards or examining the effects of an electrical field generated in the opposite ventricle.

METHODS

In open-chested sheep, right and left ventricular conductance, two-dimensional echocardiography, and thermodilution cardiac outputs were measured at steady-state conditions. After these measurements, postmortem pressure-volume relations, ventricular mass, and ventricular casting were performed.

RESULTS

The corrected end-diastolic volume measured by conductance correlated well with volumes measured by echocardiography (r = 0.89), postmortem pressure-volume relations (r = 0.84), and casts (r = 0.85). Left ventricular end-diastolic volume measured by conductance did not differ significantly from other standards by analysis of variance. The presence of an electrical field in the opposite ventricle did not affect measured conductance in the studied ventricle.

CONCLUSIONS

Conductance is useful for the measurement of right and left ventricular end-diastolic volumes in the beating heart and is not affected by the presence of an electrical field in the opposite ventricle. Hence, conductance is a useful tool in studies involving interventricular dependence and function.

Validation study of a new transit time ultrasonic flow probe for continuous great vessel measurements

Continuous measurement of cardiac output is important during experimental and clinical cardiac surgery as an indicator of ventricular function. Previous flow probes underestimated flow secondary to position and flow (S-series probes; Transonic Systems, Inc., Ithaca, NY), required frequent calibrations (electromagnetic), and were cumbersome to use. The new A-series probe (ASP) by Transonic Systems, Inc., uses a new X method of ultrasonic illumination insensitive to perturbations in flow. The ASPs were found to be accurate during in vitro studies, but have not been validated in vivo. Six anesthetized pigs were instrumented for right atrium to left atrium bypass, and ASPs were placed on the ascending aorta and pulmonary artery. Baseline measurements included aortic (Ao) and pulmonic flow (P), and thermodilution (Td) cardiac output. Animals then were placed on right heart bypass, and flow was randomly varied from 1 to 6 L/min, and Ao flow was recorded. In addition, ASPs were rotated and their direction reversed. After data collection, the occlusive roller pump (RP) was calibrated using a timed collection method. Calibrated RP flows were plotted versus ASP flows, and regression was applied. There was no difference between mean Ao, P, and Td cardiac outputs at baseline. In addition, changes in position and direction of the probe did not affect measurement of flow. The ASPs showed a highly linear correlation with RP ([r = 0.98, p < 0.01] ASP[L/min] = 0.98 RP-0.032). During laminar flow states, ASPs are accurate and insensitive to position on the great vessels.

Iatrogenic myocardial edema: increased diastolic compliance and time course of resolution in vivo

BACKGROUND

Perfusion-induced edema reduces diastolic compliance in isolated hearts, but this effect and the time for edema to resolve after blood reperfusion have not been defined in large animals.

METHODS

Edema was induced by coronary perfusion with Plegisol (750 mL, 289 mOsm/L) during a 1-minute aortic occlusion in 6 pigs. This was followed by whole blood reperfusion, inotropic support, and circulatory assistance until sinus rhythm and contractile function were restored. A control group (n = 6) was treated similarly, with 1 minute of electrically induced ventricular fibrillation and no coronary perfusion. Recorded data included electrocardiogram, left ventricular pressure and conductance, aortic flow, and two-dimensional echocardiography. Preload reduction by vena caval occlusion was used to define systolic and diastolic properties. Data were recorded at baseline and at 15-minute intervals for 90 minutes after reperfusion.

RESULTS

In the edema group, average left ventricular mass (132 +/- 7 [standard error of the mean] versus 106 +/- 4 g) and ventricular stiffness constant (0.15 +/- 0.02 versus 0.05 +/- 0.01) increased after Plegisol versus baseline (p < 0.05), returning to normal after 45 minutes of reperfusion. In controls, mass (118 +/- 6 versus 116 +/- 4 g) and ventricular stiffness (0.06 +/- 0.01 versus 0.05 +/- 0.01) did not change significantly. There was no significant change in systolic function. Myocardial water content at the end of the study was not different for the two groups.

CONCLUSIONS

Crystalloid-induced edema and diastolic stiffness resolve after 45 minutes in pigs. This suggests that edema caused solely by cardioplegia during cardiac operations should not cause significant perioperative ventricular dysfunction.

Conductance-echocardiography correlation during changes in left ventricular volume

Conductance (COND) measurements of left ventricular volume, satisfactory under steady state conditions, may be altered by extraneous factors during complex experiments or cardiac surgery. A reference technique is needed to detect changes in the COND-left ventricular volume relationship. This technique should indicate when recalibration of COND is needed. Accordingly, we assessed the relationship between left ventricular COND and the area of left ventricular short-axis cross section (SACS) by two-dimensional echocardiography during vena caval occlusion. Thirteen anesthetized pigs underwent a median sternotomy and insertion of a COND catheter. Two-dimensional echocardiography and COND were displayed and recorded simultaneously on a digital video monitor. Data were analyzed at end-diastole during the filling phase after vena caval occlusion, because the quality of two-dimensional echocardiography was better during recovery. Results demonstrated a linear relationship between left ventricular COND and SACS at end-diastole, with a positive slope. Correlation coefficients ranged from 0.88 to 1.0 and averaged 0.96 +/- 0.01 (SE). The overall mean relationship was (SACS) = 0.40 (COND) - 17. It is concluded that SACS by two-dimensional echocardiography can be employed to confirm COND measurements of left ventricular end-diastolic volume during laboratory experiments or cardiac surgery. Stability of the SACS-COND relationship indicates that COND calibration is valid. Changes in the SACS-COND relationship would require recalibration of COND. Data markedly deviating from a linear SACS-COND relation reflect experimental error and should be discarded.

Extrinsic factors influencing left ventricular conductance in situ

BACKGROUND

The accuracy of conductance measurement of left ventricular (LV) volume is affected by parallel conductance (Vp) from right ventricular (RV) volume as well as surroundings of the heart. No studies have quantified the extrinsic influences on Vp.

METHODS AND RESULTS

In six anesthetized pigs, using a median sternotomy and pericardial well, implantable cardioverter defibrillator patches, normal saline, or echocardiography gel were introduced and removed. LV end-diastolic pressure (LVEDP) did not change significantly with these interventions. Raw LV conductance was used to estimate end-diastolic volume (LVEDV), end-systolic volume (LVESV), and stroke volume (SV). Saline significantly increased mean +/- SEM calculated LVEDV from 106 +/- 8 to 131 +/- 6 mL and calculated LVESV from 81 +/- 7 to 110 +/- 5 mL; calculated SV decreased from 25 +/- 3 to 21 +/- 2 mL (P < .05, paired t test). Implantable cardioverter defibrillator patches and gel did not significantly change calculated LV volumes. LV conductance was also measured in arrested hearts during LV filling (5 to 60 mL) at four levels of RV volume (RVV). Using a fixed value for Vp, calculated mean LV volume was 30 +/- 3 mL at RVV = 0, 32 +/- 3 mL at RVV = 20, 33 +/- 3 mL at RVV = 40, and 36 +/- 3 mL at RVV = 60 (P < .01, repeated-measures ANOVA).

CONCLUSIONS

While implantable cardioverter defibrillator patches and gel have no statistically significant effect, saline and RVV affect LV volume calculations by conductance, requiring special techniques during cardiopulmonary bypass or caval occlusion.

Diastolic function in the heterotopic rat heart transplant model. Effects of edema, ischemia, and rejection

Decreased systolic ventricular function and compliance and increased left ventricular edema and mass have been demonstrated in cardiac allograft rejection. Whether decreased left ventricular compliance in rejection is caused by myocardial edema has not been examined, and compliance in the Ono-Lindsey model has not been reported. Heterotopic rat abdominal cardiac transplantation was performed in ACI isografts (n = 24) and in ACI to Lewis allografts (n = 24). Subgroups were studied on posttransplantation days 0, 1, 3, and 5 (each n = 6). Both transplanted hearts and native hearts were arrested with potassium for the assessment of myocardial water content, heart weight, and the left ventricular pressure-volume relation. In transplanted hearts, myocardial water content did not change in isografts but increased on posttransplantation day 5 in allografts (81.1% on posttransplantation day 5 versus 76.1% on day 0, 77.2% on day 1, and 77.5% on day 3, p < 0.05). Wet and dry heart weight also increased on posttransplantation day 5 in allografts (p < 0.05). The left ventricular pressure-volume relation in transplanted hearts shifted to the left when compared with that in native hearts in all subgroups; these volume differences were statistically significant (p < 0.01) for all pressures above 7.5 mm Hg. This pattern was similar in isografts and allografts on posttransplantation days 0, 1, and 3, and no significant differences between isografts and allografts were demonstrated. On posttransplantation day 5, however, the pressure after a 0.05 ml injection in allografts was greater in transplanted hearts than in native hearts (24 +/- 3 versus 3 +/- 1 mm Hg, p < 0.01). The pressure difference between transplanted and native hearts was also significantly greater in allografts than in isografts (22 +/- 2 versus 6 +/- 1 mm Hg, p < 0.01), indicating an increase in stiffness of allografts. Thus edema and impaired diastolic properties occur concurrently with allograft rejection. Left ventricular volume is abnormal from posttransplantation days 0 to 5 in transplanted hearts but not native hearts in the Ono-Lindsey model with current methods, apparently because of ischemic injury during transplantation.

Systolic arterial pressure recovery after ventricular fibrillation in pigs

Ventricular fibrillation (VF) is induced during implantable cardioverter defibrillator insertion and can result in cardiovascular collapse. The relation between repeated VF trials of varying duration and systolic blood pressure (SBP) recovery rate was studied in 6 pigs. Two implantable cardioverter defibrillator patches were placed on the heart, and VF was varied in a cyclic pattern until cardiovascular collapse occurred. A negative logarithmic relation between SBP recovery rate and duration of VF was found in 4 of the pigs with correlation coefficients of 0.62 to 0.97 (p < 0.05). The overall correlation coefficient was 0.51 for all 116 data points (p < 0.001). Although there was a significant (p < 0.05) decrease in average (+/- standard error of the mean) baseline SBP in the second half of each experiment (83 +/- 5 mm Hg versus 77 +/- 6 mm Hg), no significant difference in SBP was observed during VF (17 +/- 1 mm Hg versus 16 +/- 1 mm Hg) or after 15 seconds of SBP recovery (51 +/- 4 mm Hg versus 46 +/- 3 mm Hg) between the two halves of the experiments. Cardiovascular collapse occurred without warning; epinephrine was effective in reversing it. In conclusion, SBP recovery rate and duration of VF have a negative logarithmic relation consistent with a negative effect on left ventricular contractility with prolongation of VF. The onset of cardiovascular collapse during implantable cardioverter defibrillator testing cannot be predicted on the basis of monitored blood pressure alone.

Systolic arterial pressure recovery after ventricular fibrillation/flutter in humans

Although the elective induction of cardiac arrest for implantable defibrillator insertion under general anesthesia is widely used, the hemodynamics of recovery of arterial blood pressure after cardiac arrest is not well-defined. Accordingly, the time course of recovery of systolic arterial pressure was studied in seven patients during the repetitive induction of ventricular fibrillation (n = 6) or ventricular flutter (n = 1). The mean number of episodes of cardiac arrest was 7 +/- 2, and the mean drop in systolic pressure was 84 +/- 16 mmHg. The mean recovery time for systolic pressure was 10 +/- 6 seconds, the average systolic pressure recovery rate was 13 +/- 14 mmHg/sec, and the mean percent systolic pressure recovery was 94% +/- 9%. A negative logarithmic relation was found to exist between the rate of systolic arterial pressure recovery and the duration of ventricular fibrillation or flutter with a correlation coefficient of 0.68 to 0.97 (P < 0.05) in five of the seven patients. A linear relation between the time for systolic pressure recovery and duration of asystole was also defined. These results are consistent with the view that prolongation of ventricular fibrillation or flutter increases the duration of arterial pressure recovery through a negative effect on left ventricular contractility. Increased understanding of these relations may lead to increased safety of implantable defibrillator insertion.