Resveratrol preferentially inhibits protein kinase C-catalyzed phosphorylation of a cofactor-independent, arginine-rich protein substrate by a novel mechanism

Resveratrol, a polyphenolic natural product abundantly present in grape skins, is a candidate cancer chemopreventive agent that antagonizes each stage of carcinogenesis and inhibits protein kinase C (PKC), a key mediator of tumor promotion. While resveratrol has been shown to antagonize both isolated and cellular forms of PKC, the weak inhibitory potency observed against isolated PKC cannot account for the reported efficacy of the polyphenol against PKC in cells. In this report, we analyze the mechanism of PKC inhibition by resveratrol. Our results indicate that resveratrol has a broad range of inhibitory potencies against purified PKC that depend on the nature of the substrate and the cofactor dependence of the phosphotransferase reaction. Resveratrol weakly inhibited the Ca2+/phosphatidylserine-stimulated activity of a purified rat brain PKC isozyme mixture (IC(50) = 90 microM) by competition with ATP (K(i) = 55 microM). Consistent with the kinetic evidence for a catalytic domain-directed mechanism, resveratrol inhibited the lipid-dependent activity of PKC isozymes with divergent regulatory domains similarly, and it was even more effective in inhibiting a cofactor-independent catalytic domain fragment (CDF) of PKC generated by limited proteolysis. This suggested that regulatory features of PKC might impede resveratrol inhibition of the enzyme. To explore this, we examined the effects of resveratrol on PKC-catalyzed phosphorylation of the cofactor-independent substrate protamine sulfate, which is a polybasic protein that activates PKC by a novel mechanism. Resveratrol potently inhibited protamine sulfate phosphorylation (IC(50) = 10 microM) by a mechanism that entailed antagonism of the activation of PKC by protamine sulfate and did not involve competition with either substrate. On the basis of the presence of PKC isozymes at subcellular sites rich in polybasic proteins, it has been proposed that certain endogenous polybasic PKC substrates may activate PKC in cells by the same mechanism as protamine sulfate. Our results suggest that antagonism by resveratrol of the phosphorylation of cellular PKC substrates that resemble protamine sulfate in their interactions with PKC may contribute to the efficacy of resveratrol against PKC in cells.

Prophylactic oral amiodarone compared with placebo for prevention of atrial fibrillation after coronary artery bypass surgery

BACKGROUND

Postoperative atrial fibrillation occurs in 20% to 40% of patients undergoing coronary artery bypass grafting (CABG) and contributes to delayed recovery, increased length of stay, and increased hospital cost. Measures at preventing postoperative atrial fibrillation have had mixed results. We report a double-blind trial comparing oral amiodarone with placebo for the prevention of atrial fibrillation after CABG.

METHODS AND RESULTS

All patients undergoing CABG were considered eligible. Exclusion criteria included bradycardia (<50 beats/min), prior Atrial fibrillation, concurrent therapy with antiarrhythmic drugs, or concomitant valve surgery. Patients were given 2 g of amiodarone (73 patients) or placebo (70 patients) in divided doses 1 to 4 days before surgery and 400 mg daily for 7 days postoperatively. Atrial fibrillation occurred in 24.7% (18 of 43) of patients receiving amiodarone and 32. 8% (23 of 70) of patients receiving placebo (P =.30). Heart rate at onset of atrial fibrillation was 133.4 +/- 26.6 beats/min for amiodarone compared with 152.9 +/- 31.6 beats/min for placebo (P =. 04). Duration of atrial fibrillation was 10.2 +/- 8.1 hours for amiodarone compared with 16.2 +/- 27.5 hours for placebo (P =.67). Patients receiving both beta-blockade and amiodarone had a 16.7% incidence of atrial fibrillation compared with 31.9% in the remaining patients (P =.10). Atrial fibrillation was associated with an increased cost of $7011 compared with those who remained in sinus rhythm ($23,869 +/- $20,894 vs $16,857 +/- $5401 in sinus rhythm). Hospital cost of those taking amiodarone was $18,895 +/- $13,267 compared with $18,839 +/- $11,537.18 for placebo (P =.42).

CONCLUSION

Postoperative CABG atrial fibrillation is associated with prolonged hospital stay and increased cost. Prophylactic oral amiodarone did not statistically alter the incidence or duration of atrial fibrillation after CABG, although favorable trends were noted. Hospital cost was not affected by therapy with amiodarone.

A peptide substrate-based affinity label blocks protein kinase C-catalyzed ATP hydrolysis and peptide-substrate phosphorylation

Studies focused on the cAMP-dependent protein kinase (PKA) have led to the identification of conserved active-site residues involved in Ser/Thr protein kinase catalysis and have ruled out a role for Cys residues in the catalytic mechanism. Protein kinase C (PKC) is a Ser/Thr protein kinase isozyme family. We recently reported that the peptide-substrate analog N-biotinyl-Arg-Arg-Arg-Cys-Leu-Arg-Arg-Leu (N-biotinyl-RRRCLRRL) spontaneously forms intermolecular disulfide bridges with the active-site region of PKC isozymes concomitant with inactivation of histone kinase catalysis. Because Cys does not participate in PKC catalysis, one can analyze the active-site topology of PKC by examining which catalytic reactions are sterically hindered when the inactivator peptide is tethered to Cys in the active-site region of the enzyme. In this report, we show that N-biotinyl-RRRCLRRL inactivates the bulky PKC-catalyzed histone phosphorylation reaction, the comparatively less bulky PKC-catalyzed phosphorylation of a series of octapeptide, hexapeptide, and pentapeptide substrates, the intramolecular autophosphorylation reaction of PKC, and the least bulky PKC-catalyzed reaction, ATP hydrolysis, in a dithiothreitol-sensitive manner with comparable efficacy. Our results provide evidence that the covalent linkage of N-biotinyl-RRRCLRRL to the active-site region of PKC sterically hinders PKC catalysis, even in the absence of peptide and protein substrates.

Placental ontogeny of the Australian scincid lizards Niveoscincus coventryi and Pseudemoia spenceri

Models for the evolution of placentation among squamate reptiles have been strongly influenced by early work on one lineage of Australian scincid lizards: one of three lineages that include species with specialized allantoplacentation. The discovery of two types of complex allantoplacentae among species currently assigned to the Eugongylus species group led Weekes ([1935] Proc. Zool. Soc. Lond., 2:625-645) to propose that a graded evolutionary sequence was exemplified by the morphological series of allantoplacental types that existed among Australian skinks. One of the model's strengths is the incorporation of testable inferences of the relationship between placental structure and function. However, descriptions of placental structure for some species are incomplete and subsequent taxonomic revisions have resulted in confusion concerning the species studied. One of the ambiguities is the identity of Lygosoma weekesae (Kinghorn [1929] Proc. Linn. Soc. N.S.W., 54:32-33), one of two species for which the most specialized type of allantoplacenta was defined. The distinguishing characteristic of this placental type is the presence of a structure known as a placentome. Subsequent to the original species description, Lygosoma weekesae was named a synonym for Pseudemoia spenceri (Rawlinson [1974] Mem. Natn. Mus. Vict., 35:87-96), yet the placental description (Weekes [1929] Proc. Linn. Soc. N.S.W., 54:34-60) is thought to be of Niveoscincus coventryi (Rawlinson [1975] Mem. Natn. Mus. Vic., 36:1-16). We describe placental ontogeny of N. coventryi and P. spenceri as a contribution to study of comparative placentation among lygosomatine skinks. We conclude that the placental description for L. weekesae could not have been N. coventryi, because a placentome is not a component of the allantoplacenta of N. coventryi. Further, the allantoplacenta of this species does not conform to previously defined categories for Eugongylus group skinks. The allantoplacenta of P. spenceri contains a placentome that is structurally congruous with the original description of placentation for L. weekesae (Weekes [1929] Proc. Linn. Soc. N.S.W., 54:34-60). Comparison of extraembryonic membrane and placental structure among the four viviparous and one oviparous species of Eugongylus group skinks for which data are available shows that each species exhibits characters that distinguish it from other species, while additional characters are shared among all, or some, species. Based on a recent phylogenetic hypothesis, the distribution of allantoplacental types among these species does not support Weekes' ([1935] Proc. Zool. Soc. Lond., 2:625-645) model of a graded sequence for the evolution of squamate placentation.

Response to radiation therapy and prognosis in breast cancer patients with BRCA1 and BRCA2 mutations

BACKGROUND AND PURPOSE

The purpose of this study is to evaluate overall survival in BRCA1 or BRCA2 breast cancer patients, describe presenting stage, review histologic findings and evaluate response to radiotherapy.

MATERIALS AND METHODS

A retrospective study was performed evaluating breast cancer patients with known mutations of BRCA1 or BRCA2. Patients from 12 different pedigrees were cross-referenced with the Utah Cancer Registry (UCR), histologic findings were verified and radiotherapy records were reviewed for acute response to treatment. Actuarial survival calculations were performed and patients were matched for age, date of diagnosis and tumor size.

RESULTS

Thirty breast cancer patients with BRCA1 mutations were found to have 34 breast cancers (four had bilateral metachronous lesions) and 20 breast cancer patients with BRCA2 mutations were found to have 22 breast cancers (two had bilateral metachronous disease). The median age at diagnosis was 49 years (range 21-77 years) and 42 years (range 23-83 years), respectively, for BRCA1 and BRCA2 patients. Unusual histologic types of breast cancers were represented with 7% (4/56) medullary and 5% (3/56) lobular carcinomas. Complete staging was possible for 63% (35/56) of cancers. Stages I, II, III and IV represented 26, 63, 6 and 6% of cancers, respectively. The most severe radiation reaction was moist desquamation which was self-limiting and developed in 29% (6/21) of irradiated patients. The mean follow-up was 9.8 and 7.5 years for BRCA1 and BRCA2 cancers, respectively. Kaplan-Meier survival analysis demonstrated 5-year survival values of 75% for BRCA1 patients, 73% for BRCA2 patients, 70% for matched controls and 69% for UCR controls. No statistically significant differences were evident between the groups at 5 or 10 years.

CONCLUSIONS

Despite their younger age at presentation, breast cancer patients harboring BRCAI or BRCA2 mutations present at a similar stage, display a normal acute reaction to radiotherapy and have a similar prognosis when compared with sporadic breast cancer patients.

Cognitive test performance and crash risk in an older driver population

This paper reports on the usefulness of five brief tests of cognitive function for identifying older drivers who may be at increased risk of crash involvement; it also examines the broader issue of whether impaired cognitive function is associated with increased crash risk in the older driver population. Data for the study were collected from 3238 drivers aged 65 and older applying for renewal of their North Carolina driver's license. The specific cognitive assessments examined include the Trail Making Test parts A and B, the Short Blessed Orientation-Memory-Concentration test of cognitive impairment, a modification of the American Association of Retired Persons 'Reaction Time' test, and a timed Traffic Sign Recognition test. Information on crash involvements during the 3-year period prior to testing was obtained by linkage with the North Carolina driver history file. Although the individual tests were not found to be particularly effective screening tools for identifying subsets of high risk drivers, cognitive test performance remained significantly associated with crash risk even after controlling for driver age, race and measures of driving exposure. Drivers who scored in the lowest 10% on the cognitive tests were approx. 1.5 times more likely to be in crashes than were drivers who scored in the highest 10%. Implications for the counseling and licensing of older drivers are discussed, along with recommendations for future research.

Prognosis of adenocarcinoma arising in Barrett's esophagus

BACKGROUND

The rising incidence of adenocarcinoma of the esophagus, as well as its association with Barrett's esophagus, has been reported previously. We report our experience in treating patients with adenocarcinoma arising in Barrett's esophagus.

METHODS

A retrospective review was performed of 70 consecutive patients with adenocarcinoma of the esophagus treated between November 1988 and April 1996 with preoperative chemoradiation and resection. Demographics, pathologic features, and survival were compared with patients who developed adenocarcinoma of the esophagus without Barrett's. Statistical analyses was performed using Student's t test, Fisher's exact test, and Kaplan-Meier where appropriate.

RESULTS

Thirty-two (46%) patients had adenocarcinoma arising in Barrett's esophagus. During the last 4 years, 72% (23 of 32) of patients with adenocarcinoma had coexistent Barrett's. No differences in patients with or without Barrett's with regard to age, sex, race, tumor location, preoperative chemotherapy, type of operation, or operative stage were observed. Tumors in patients with Barrett's were larger (p = 0.017), had better differentiation (p = 0.002), and were less likely to have a complete response to preoperative chemoradiation (p = 0.05). Actuarial survival, however, was better in the group with associated Barrett's esophagus (p = 0.033).

CONCLUSIONS

The incidence of adenocarcinoma of the esophagus arising in Barrett's esophagus appears to be increasing. It may be distinct clinically and biologically from adenocarcinoma of the esophagus that does not develop in association with Barrett's epithelium. Long-term survival was better in our patients with adenocarcinoma associated with Barrett's esophagus.

A system for postoperative visualization and analysis of left ventricular pressure-volume loops

A patient monitoring system for continuous real-time monitoring of left ventricular (LV) function in the postoperative setting was developed. Common hemodynamic parameters and LV functional indices are all calculated from left ventricular pressure-volume loops (PV-loops). Visualization of the PV-loops, along with the hemodynamic parameter derived from them, provides valuable insight into ventricular function and patient recovery. The pressure component is obtained via a pressure sensing catheter placed during surgery. Volume is measured via non-imaging radionuclide techniques using a modified Capintec-VEST. Following surgery and transfer to the recovery unit, the patient's blood is labeled with Tc-99m. A portable gamma camera is used to measure baseline ejection fraction (EF) and to aid in placing the VEST. The specific radioactivity of the blood is calibrated using the baseline EF and thermodilution cardiac output. To confirm the volume measurement accuracy of this technique six patients undergoing bilateral heart catheterization were studied. Single-plane cineventriculographic LV volumes were compared to those calculated from the VEST's time activity curve.

A new method for predicting crashworthiness

Consumer information concerning the predicted 'safeness' of a new car model is based on the results of crash tests. Unfortunately, because it allows comparisons only within size/weight groups, the information is somewhat incompatible with the normal car-purchase decision process since consumers often consider cars within different groups. In addition, based on past research, the association of the crash-test information with real-world crash outcomes is, at best, somewhat limited. The goal of this study was to explore a methodology for improving this information, a methodology which incorporates not only the crash-test information, but also information concerning real-world occupant injury experience in prior crashes involving similar vehicles ('clones'). The clone information included both driver injury severity in past clone crashes from the North Carolina accident file and various indicators of relative driver injury in clones extracted from published insurance-related data from the Highway Loss Data Institute (HLDI). Final models developed included both measures of the Head Index Criteria (HIC) from the crash test and some measure of clone performances as significant predictors. While the North Carolina clone data is intuitively 'cleaner' in that it describes injury level per crash rather than per insured year, the medical claims indices from the HLDI data consistently were shown to be the stronger predictors. Future research will need to look at ways of better combining the crash-test variables and of possible modifications to the HLDI indices. In general, the analyses generated encouraging results that appear to point to possible improvements in the crashworthiness information.

Electron arc irradiation of the postmastectomy chest wall: clinical results

BACKGROUND AND PURPOSE

Since 1980 electron arc irradiation of the postmastectomy chest wall has been the preferred technique for patients with advanced breast cancer at our institution. Here we report the results of this technique in 140 consecutive patients treated from 1980 to 1993.

MATERIALS AND METHODS

Thoracic computerized tomography was used to determine internal mammary lymph node depth and chest wall thickness, and for computerized dosimetry calculations. Total doses of 45-50 Gy in 5 to 5 1/2 weeks were delivered to the chest wall and internal mammary lymph nodes via electron arc and, in most cases, supraclavicular and axillary nodes were treated with a matching photon field. Patients were assessed for acute and late radiation changes, local and distant control of disease, and survival. Patients had a minimum follow-up of 1 year after completion of radiation treatment, and a mean follow up interval of 49 months and a median of 33 months. All patients had advanced disease: T stages 1, 2, 3, and 4 represented 21%, 39%, 21% and 19% of the study population, with a mean number of positive axillary lymph nodes of 6.5 (range, 0-29). Analysis was performed according to adjuvant status (no residual disease, n = 90), residual disease (positive margin, n = 15, and primary radiation, n = 2), or recurrent disease (n = 33).

RESULTS

Acute radiation reactions were generally mild and self limiting. A total of 26% of patients developed moist desquamation, and 32% had brisk erythema. Actuarial 5 year local-regional control, freedom from distant failure, and cause-specific survival was 91%, 64%, and 75% in the adjuvant group; 84%, 50%, and 53% in the residual disease group; and 63%, 34%, and 32% in the recurrent disease group, respectively. In univariate Cox regressions, the number of positive lymph nodes was predictive for local failure in the adjuvant group (P = 0.037). Chronic complications were minimal with 11% of patients having arm edema, 17% hyperpigmentation, and 13% telangectasia formation.

CONCLUSION

These data demonstrate that local-regional control with electron are therapy of the postmastectomy chest wall is comparable to photon techniques. Acute radiation reactions are well tolerated and mostly of minor extent. A previous report demonstrated a significant reduction in the dose-volume relationship of the lung using the electron arc compared with two photon techniques. Consequently, with careful attention to treatment planning and dosimetry, electron arc therapy of the postmastectomy chest wall is safe and effective. The radiation dose to heart and lung is minimized without compromise on local control.

Safety of remote aortic valve replacement after prior coronary artery bypass grafting

BACKGROUND

A previous coronary artery bypass grafting (CABG) procedure may complicate subsequent aortic valve replacement (AVR). However, the operative risks and long-term outcome of patients who undergo these two procedures remain poorly defined.

METHODS

The medical records of all patients undergoing AVR between February 1986 and September 1995 were reviewed retrospectively. The patients selected for analysis had previously undergone CABG.

RESULTS

We performed AVR in 23 consecutive patients who had previously undergone CABG (mean number of grafts, 2.8). The AVR was performed an average of 7.6 years after CABG (range, 2 to 17 years). There were 20 men and 3 women, with a mean age of 69 years (range, 56 to 85 years). Twenty patients were operated upon for aortic stenosis (mean gradient 54 mm Hg, mean valve area 0.7 cm2), and 3 patients underwent operation for aortic regurgitation. The average aortic valve gradient at the initial revascularization operation was 8 mm Hg (range, 0 to 29 mm Hg). There was no correlation between the aortic valve gradient at the initial revascularization and the interval between CABG and AVR. At the second operation, AVR was performed alone in 11 patients, combined with repeat CABG in 11 patients (mean number of grafts, 1.4), and with mitral valve replacement in 1 patient. A mechanical prosthesis was selected in 14 patients, and a bioprosthesis was used in 9 patients. There were no perioperative deaths. There were five late deaths at an average follow-up of 44 months. The 5-year actuarial survival was 71%.

CONCLUSIONS

Previous CABG poses added technical challenges at the time of reoperation for AVR. The operation can be performed safely, with the expectation of satisfactory long-term survival.

Evaluation of pulmonary lesions with FDG-PET. Comparison of findings in patients with and without a history of prior malignancy

STUDY OBJECTIVE

The purpose of this study was to evaluate the accuracy of positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG) in differentiating benign from malignant pulmonary lesions both in patients with and without a history of prior malignancy.

DESIGN

Forty-eight consecutive patients with pulmonary lesions suspicious for malignancy underwent FDG-PET scanning. Group 1 included 27 patients without and group 2 included 21 patients with a history of malignancy. Pathologic proof of diagnosis was obtained for 32 patients and 16 patients were followed up clinically and radiographically for at least 6 month. The standard uptake ratio (SUR) and the lesion to background (L/B) ratio were determined in 45 patients.

SETTING

Vanderbilt University Medical Center.

RESULTS

In group 1, the average SUR and L/B ratio for malignant lesions (n=14) were 8.9 +/- 4.9 and 20.6 +/- 14.2, respectively. For benign lesions (n=12), the average SUR was 3.3 +/- 3.2 and L/B ratio was 5.2 +/- 5.5. In group 2, the average SUR and L/B ratio for malignant lesions were not significantly different from group 1. Using either a SUR greater than 2.5 or L/B ratio greater than 5 as an cutoff level to differentiate benign and malignant lesions, the sensitivity and negative predictive value in both groups were 100%. There were five false-positive studies in group 1 and one in group 2, including tuberculosis (n=2), a granulomatous lesion (n=1), an inflammatory lesion (n=1), a schwannoma (n=1), and a fibrous mesothelioma (n=1). The overall accuracy was 88%, 81% in group 1, and 95% in group 2.

CONCLUSION

FDG-PET can identify malignant pulmonary lesions both in patients without and with a history of prior malignancy with a high sensitivity and negative predictive value for lesions greater than 1 cm (100% in this study). High FDG uptake by some inflammatory processes and benign tumors may cause false-positive results. Semiquantitative evaluation using SUR or L/B ratio provides similar accuracy.

Effects of North Carolina's mandatory safety belt law on children

OBJECTIVES

To assess the effect of the North Carolina law mandating that all front seat passengers use a safety belt on children 4 through 15 years of age.

METHODS

North Carolina collision reports, completed by local police or the state highway patrol for crashes with greater than $500 worth of damage, were analyzed using time series analysis on the monthly percentage of deaths and serious injuries between January of 1980 and February of 1994.

RESULTS

Following the 1985 implementation of the law, children 4 to 15 years of age experienced a 42% decline in deaths and serious injuries.

CONCLUSIONS

The mandatory safety belt law in North Carolina has been associated with a decline in deaths and serious injuries. Additional research in needed to assess the seat belt behaviors of this age group as well as the specific effects of seat belt use using outcome measures more precise than those available in police crash reports.

Embryonic development of central nervous system myelination in a reptilian species, Eumeces fasciatus

The myelin proteolipid proteins are a vital component of the vertebrate central nervous system (CNS), contributing essential functions to the development of the myelinating cells of the CNS and to the structure of CNS myelin. Alternative splicing of the proteolipid protein (PLP) gene to produce two related isoforms occurs in Mammalia, Aves, and Reptilia, but not Amphibia. As part of a long-term investigation into the function of the different isoforms of PLP, embryonic development, myelination, and PLP gene expression in reptilian CNS were examined. PLP gene expression was already substantial by day 19 (stage 39) of the 27-day Eumeces fasciatus egg incubation period. By day 21 of incubation, also stage 39, PLP mRNA was at peak levels; there was a significant amount of CNS myelination as demonstrated by electron microscopy of the spinal cord; and the reflexive motor response was evident. Although most axons were myelinated by the time of hatching, myelin sheaths continued to increase in size and compactness after hatching. The correlation of physiological development, CNS myelination, and expression of the PLP gene in the lizard corresponded well with the developmental pattern seen in mammals.

MRI complements standard assessment of right ventricular function after lung transplantation

BACKGROUND

Changes in right ventricular mass and ejection fraction after single-lung transplantation for pulmonary hypertension are poorly understood.

METHODS

To complement functional data provided by echocardiography, radionuclide ventriculography, and right heart catheterization, magnetic resonance imaging was used to assess right ventricular function in 5 single-lung transplant recipients with preoperative pulmonary hypertension and right ventricular dysfunction (right ventricular ejection fraction, 0.21 +/- 0.09). The right and left ventricular mass, ejection fraction, and mass ratio (left ventricular mass/right ventricular mass) were calculated from the magnetic resonance images.

RESULTS

The mean pulmonary artery pressure fell from 72 +/- 18 to 21 +/- 8 mm Hg after transplantation. At 3 months after transplantation both the left ventricular and right ventricular ejection fractions approached normal values, as shown by both radionuclide ventriculography and magnetic resonance imaging, but the right ventricular mass remained abnormally high with slightly low mass ratios. By 1 year both the left ventricular and right ventricular masses had regressed to normal with near-normal mass ratios.

CONCLUSIONS

Right ventricular performance returns to nearly normal early after transplantation, but the right ventricular mass regresses over a more prolonged time. Cine magnetic resonance imaging provides a noninvasive means of assessing changes in right ventricular function and mass after lung transplantation.

Radiation injury to the heart

For the RTOG Consensus Conference on Late Effects of Cancer Treatment we summarize the clinical manifestations of cardiac complications appearing months to years following incidental irradiation of the heart during treatment of thoracic neoplasms. The most common effects present as pericardial disease, however, it is becoming more clear that precocious or accelerated coronary artery disease is an important late effect, especially in patients treated with radiation before the age of 21 years. To the extent it is known, the pathophysiology of the various syndromes is described and the extensive literature on dose, volume, and fractionation factors is reviewed. Based upon our current understanding of late cardiac effects, a clinical grading system has been developed and is published elsewhere in this issue.

Comparison of gating methods for the real-time analysis of left ventricular function in nonimaging blood pool studies

BACKGROUND

Gating methods developed for electrocardiographic-triggered radionuclide ventriculography are being used with nonimaging detectors. These methods have not been compared on the basis of their real-time performance or suitability for determination of load-independent indexes of left ventricular function. This work evaluated the relative merits of different gating methods for nonimaging radionuclude ventriculographic studies, with particular emphasis on their suitability for real-time measurements and the determination of pressure-volume loops.

METHODS AND RESULTS

A computer model was used to investigate the relative accuracy of forward gating, backward gating, and phase-mode gating. The durations of simulated left ventricular time-activity curves were randomly varied. Three acquisition parameters were considered: frame rate, acceptance window, and sample size. Twenty-five studies were performed for each combination of acquisition parameters. Hemodynamic and shape parameters from each study were compared with reference parameters derived directly from the random time-activity curves. Backward gating produced the largest errors under all conditions. For both forward gating and phase-mode gating, ejection fraction was underestimated and time to end systole and normalized peak ejection rate were overestimated. For the hemodynamic parameters, forward gating was marginally superior to phase-mode gating. The mean difference in errors between forward and phase-mode gating was 1.47% (SD 2.78%). However, for root mean square shape error, forward gating was several times worse in every case and seven times worse than phase-mode gating on average.

CONCLUSIONS

Both forward and phase-mode gating are suitable for real-time hemodynamic measurements by nonimaging techniques. The small statistical difference between the methods is not clinically significant. The true shape of the time-activity curve is maintained most accurately by phase-mode gating.

Effects of procainamide and lidocaine on defibrillation energy requirements in patients receiving implantable cardioverter defibrillator devices

INTRODUCTION

In acute canine studies, lidocaine, but not procainamide, increases defibrillation energy requirements. We evaluated the effects of lidocaine or procainamide on defibrillation energy requirements in 27 patients undergoing intraoperative testing for implantable cardioverter defibrillator device placement.

METHODS AND RESULTS

Patients were tested off antiarrhythmic drugs and again following either lidocaine (200 to 250 mg loading and 3 mg/min maintenance infusions) or procainamide (1 gm loading and 3 to 4 mg/min maintenance infusions). The defibrillation testing protocol consisted of initial testing at 15 J, followed by higher or lower energies to determine the lowest energy producing three consecutive successful defibrillations. Overall, the mean defibrillation energy increased from 14 +/- 5 J to 18 +/- 7 J during lidocaine (plasma concentration 5.1 +/- 1.6 micrograms/mL; P < 0.02) but were similar at baseline (12 +/- 5 J) and during procainamide infusion (13 +/- 6 J) (plasma concentration: procainamide 10.7 +/- 7.2 micrograms/mL; N-acetyl procainamide 1.0 +/- 0.4 micrograms/mL). A positive linear correlation was found between lidocaine plasma concentration and percent change in defibrillation energy (lidocaine: r = 0.61; P = 0.01). Procainamide raised the defibrillation energy in three patients, two with supratherapeutic plasma concentrations. The increase in defibrillation energy equaled or exceeded 25 J in four patients after lidocaine and in one patient after procainamide.

CONCLUSION

The data suggest that at high plasma concentrations, lidocaine and procainamide adversely affect defibrillation energy requirements consistent with an adverse, concentration-dependent effect of sodium channel blockade on defibrillation energy requirements in patients.

Operative risk factors and durability of repair of coarctation of the aorta in the neonate

The risk factors for the operative mortality and long-term durability of repair after surgical correction of coarctation of the aorta in neonates remain controversial. Between January 1970 and January 1993, 139 patients under 1 month of age underwent repair of coarctation of the aorta. Complex intracardiac defects were present in 59 patients. Another 44 patients had an associated ventricular septal defect. Subclavian artery flap repair was performed in 92 patients; end-to-end anastomosis (38 patients) and patch angioplasty (9 patients) were performed less commonly. The hospital mortality was significantly higher in patients with complex intracardiac defects (9 of 59 patients; 15.2%) than in those with a ventricular septal defect (1 of 44 patients; 2.3%) or with isolated coarctation (none of 36 patients; p = 0.007). Elevated pulmonary artery diastolic pressure (p = 0.041) and complex intracardiac anomalies (p = 0.048) were found to be independent predictors of hospital mortality. The presence of a complex cardiac defect (p < 0.001) was an independent predictor of poor long-term survival. Recurrent stenosis requiring reoperation had occurred or balloon dilation had been necessary in 27.9% of the children at 5 years postoperatively. In patients followed up for at least 5 years, the recurrence-free survival was better in those who had undergone subclavian artery flap repair than in those who had undergone end-to-end repair (p = 0.017). When coarctation of the aorta must be repaired in the neonate, operative mortality and long-term survival are affected by the complexity of associated intracardiac anomalies.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the efficacy of HI6 and 2-PAM against soman, tabun, sarin, and VX in the rabbit

This study compared the efficacy of HI6 and 2-PAM against nerve agent (soman, tabun, sarin, and VX)-induced lethality in the atropinesterase-free rabbits pretreated with vehicle (controls) or pyridostigmine. Treatment was administered at signs or 2 min after agent challenge and consisted of oxime (100 mumol/kg) + atropine (13 mg/kg) (alone or together with diazepam). Twenty-four-h LD50 values were calculated for soman- and tabun-intoxicated animals, whereas 24-h survival was noted in animals given 10 LD50s of sarin or VX. In pyridostigmine and control rabbits intoxicated with soman and treated with oxime + atropine (alone or together with diazepam), HI6 was 3-5 times more effective than 2-PAM. In contrast, HI6 was less effective than 2-PAM against tabun poisoning. In pyridostigmine-pretreated animals exposed to tabun, efficacy was increased more than 3-fold when compare to tabun-challenged animals treated with atropine + HI6 alone. Both oximes were highly effective against sarin and VX. These findings suggest that HI6 could replace 2-PAM as therapy for nerve agent poisoning, because it is superior to 2-PAM against soman, and when used in pyridostigmine-pretreated animals, it affords excellent protection against all four nerve agents when used in combination with atropine (alone or together with diazepam) therapy.

Thymectomy for the myasthenia gravis patient: factors influencing outcome

Thymectomy is a therapeutic option for patients with myasthenia gravis with moderate to severe disability. To document the efficacy of thymectomy coupled with medical therapy to treat this disease and to identify clinical factors that influence outcome, the clinical courses of all 46 patients (12 male and 34 female; mean age, 30 +/- 16 years) with myasthenia gravis who underwent thymectomy through a median sternotomy at a single institution over a 21-year period were reviewed. Clinical staging was determined preoperatively, at 1 month, 6 months, and 12 months postoperatively, and at last follow-up (mean time, 75 months postoperatively) using the Oosterhuis classification. Changes in severity of illness were graded as "deteriorated," "unchanged," "improved," or "much improved." Preoperative Oosterhuis classification was 3.3 +/- 1.1 and at last follow-up, 1.4 +/- 1.2 (p = 0.022). At last follow-up, 40 patients (87%) were in the improved or much improved category, and 6 patients were in the deteriorated or unchanged category. Status at 1 month, 6 months, and 12 months after operation predicted outcome at last follow-up visit (p = 0.007, p = 0.005, and p = 0.001, respectively). Clinical factors that positively influenced outcome were age less than 45 years (p = 0.004), female sex (p = 0.0309), and preoperative stage (p = 0.021).

Single lung transplantation: a temporal look at rejection, infection, and survival

Single lung transplantation (SLT) has emerged as routine therapy for selected patients with end-stage lung disease. This study examines the incidence of rejection, infection, and survival during the first posttransplant year. Twenty-one patients (12 male, 9 female; mean age 46 +/- 13 years) underwent 23 SLT procedures (12 left, 11 right lung). Indications were pulmonary fibrosis in six, emphysema in seven, primary pulmonary hypertension in three, Eisenmenger's syndrome in one, pulmonary veno-occlusive disease in one, a-1 antitrypsin deficiency in two, CREST syndrome in one, and retransplantation (graft failure and bronchiolitis obliterans) in two. All were maintained on triple immunotherapy. Survival at 1 year was 100%. The five patients with preoperative pulmonary hypertension had normal hemodynamics at follow up. Freedom from event at 1 year was rejection 23 per cent, all infections 6 per cent, viral 40 per cent, bacterial 55 per cent, fungal 74 per cent. At 1 year, cumulative incidence (events/patient-year) was rejection 1.61, all infections 2.18, viral 0.78, bacterial 1.12, fungal 0.28. Two of 21 patients have developed bronchiolitis obliterans at 1 and 2 years posttransplant. SLT provided safe, effective treatment for a wide variety of end-stage lung diseases. Rejection and infection, although common, may be safely treated with resolution.

Electron arc therapy of the postmastectomy prosthetic breast

PURPOSE

Reconstructive surgery of the postmastectomy breast presents new challenges to postoperative radiation therapy. This paper evaluates the dosimetric significance of oblique incidence of the electron field on the reconstructed mound during arc therapy.

METHODS AND MATERIALS

Using film densitometry, the relative dose distributions resulting from electron arc therapy incident on phantoms simulating the breast and chest wall dimensions of an actual patient are evaluated.

RESULTS

Irradiation of the breast phantom in normal supine position results in constriction of the dose distribution at the junction of the reconstructed mound with the chest wall. Angulation of the phantom to provide a more normal incidence of the electron beam during arc reduces the constriction by minimizing obliquity of the incident electrons.

CONCLUSION

These measurements suggest that, with proper positioning of the patient relative to the incident electron beam, electron arc therapy may be used as an alternative treatment technique for treatment of the postmastectomy reconstructed breast and chest wall.