Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

18 RELATIONSHIP BETWEEN MULTIPLE OVULATIONS AND CONCEPTION IN LACTATING DAIRY COWS

The relationship between multiple ovulations and various factors involved in conception in lactating Holstein cows was investigated in this study. A total of 53 AI cows housed in a free-stall barn were assigned to this study. They were offered a balanced TMR ad libitum during the experimental period. Cows were milked at 0830 and 1900 h. Milk yields were recorded at each milking. Estrus was detected by radiotelemetric pedometers (Yoshioka et al. 2007 Reprod. Fertil. Dev. 19, 129). The body condition score (BCS) of cows was recorded at estrus. Artificial insemination was performed according to the pedometry data. Pregnancy was diagnosed 42 days post-AI by transrectal ultrasonography. Ovulation was assessed by transrectal ultrasonography of the ovary every 3 h from the end of estrus. Ovulation time was measured from the onset of estrus to ovulation. Milk production of each cow was determined from 14 days before the day of estrus. Blood samples for estradiol-17β (E2) were collected at the peak of estrus, and for progesterone (P4), samples were collected on Days 0, 3, 6, 9, and 12 (estrus = Day 0). The E2 and P4 concentrations were measured by enzyme immunoassay. Preovulatory follicles at estrus and CL on Day 0, 3, 6, 9, and 12 were monitored by transrectal ultrasonography. The overall incidence of multiple ovulations was 28.3% (15/53). There was no difference in duration of estrus between cows with multiple ovulations and cows with single ovulations (10.2 h, n = 15 v. 9.8 h, n = 38). Ovulation time was longer for cows with multiple ovulations than that for cows with single ovulations (30.4 h, n = 10 v. 28.7 h, n = 26; P = 0.0545). In all cases of multiple ovulations, 2 follicles ovulated simultaneously. The milk production of cows with multiple ovulations was higher than that of cows with single ovulations (40.1, n = 15 v. 36.2 kg d–1, n = 38; P = 0.0515); however, BCS showed the opposite results (2.86, n = 15 v. 3.13, n = 38; P < 0.05). There was a significant inverse correlation between milk production and BCS in cows with multiple ovulations (r = –0.768; P < 0.01). The E2 concentrations showed no difference between cows with multiple and single ovulations (9.6 pg mL–1, n = 8 v. 8.2 pg mL–1, n = 23). The diameters of preovulatory dominant follicles and secondary follicles at estrus in cows with multiple ovulations were significantly smaller than those in cows with single ovulations (18.2 and 14.2 mm, n = 14 v. 19.9 mm, n = 38, respectively; P < 0.05). Cows with multiple ovulations showed a significantly higher P4 concentration and a larger CL than those with single ovulations from Day 3 to 12. The conception rate for AI was significantly higher for cows with multiple ovulations than for cows with single ovulations (73.3%, n = 15 v. 36.2%, n = 38; P < 0.05). Our results showed that high conception rates, high levels of milk production, and low BCS were associated with multiple ovulations.

Possible association of ?-arrestin 2 gene with methamphetamine use disorder, but not schizophrenia

Recent investigations suggest that the AKT/glycogen synthase kinase 3 (GSK3) signaling cascade may be associated with the pathophysiology of schizophrenia and methamphetamine (METH) use disorder. One important molecule related to this cascade is beta-arrestin 2 (ARRB2). We therefore conducted a genetic case-control association analysis of the gene for ARRB2 with schizophrenia and METH use disorder in a Japanese population (547 people with schizophrenia, 177 with METH use disorder and 546 controls). A possible association of 'tag single nucleotide polymorphisms (SNPs)' was found in METH use disorder (rs1045280: P(genotype) = 0.0118, P(allele) = 0.00351; rs2036657: P(allele) = 0.0431; rs4790694: P(genotype) = 0.0167, P(allele) = 0.0202), but no association was found with schizophrenia. We also evaluated the gene-gene interactions among ARRB2, AKT1, and GSK3B, which we previously reported for each of these diseases. However, no interaction was seen in our samples. This is the first association analysis of ARRB2, and our results indicate that ARRB2 may play a role in the pathophysiology of METH use disorder.

Association study between kynurenine 3-monooxygenase gene and schizophrenia in the Japanese population

Several lines of evidence suggest that metabolic changes in the kynurenic acid (KYNA) pathway are related to the etiology of schizophrenia. The inhibitor of kynurenine 3-monooxygenase (KMO) is known to increase KYNA levels, and the KMO gene is located in the chromosome region associated with schizophrenia, 1q42-q44. Single-marker and haplotype analyses for 6-tag single nucleotide polymorphisms (SNPs) of KMO were performed (cases = 465, controls = 440). Significant association of rs2275163 with schizophrenia was observed by single-marker comparisons (P = 0.032) and haplotype analysis including this SNP (P = 0.0049). Significant association of rs2275163 and haplotype was not replicated using a second, independent set of samples (cases = 480, controls = 448) (P = 0.706 and P = 0.689, respectively). These results suggest that the KMO is unlikely to be related to the development of schizophrenia in Japanese.

No association of serotonin transporter gene (SLC6A4) with schizophrenia and bipolar disorder in Japanese patients: association analysis based on linkage disequilibrium

Serotonin transporter gene (SLC6A4) is one of the most promising candidate genes for psychiatric disorders such as schizophrenia (SCZ) and bipolar disorder (BP). Two functional polymorphisms, 5HTTLPR and 5HTTVNTR, have been a focus for genetic association analyses; however, no conclusive results have been obtained. We conducted, 1) a mutation search of SLC6A4, 2) LD mapping to select 'tagging' markers (10 SNPs and 5HTTVNTR, while 5HTTLPR was treated as an independent marker because of its allelic form), and 3) association analysis of these 'tagging' markers and independent markers (5HTTLPR and Asn605Lys) with SCZ and BP in Japanese patients. In this mutation search, a nonsynonymous SNP, Asn605Lys, was detected. No associations of 'tagging' markers and independent markers with such conditions were found. These results indicate that SLC6A4 might not play a major role in SCZ and BP in Japanese patients, a finding that agrees with both the common disease-common variant hypothesis and common disease-rare variant hypothesis.

Association study of the frizzled-3 (FZD3) gene with schizophrenia and mood disorders

Two research groups have recently reported a significant association between schizophrenia and genetic variants of Frizzled-3 (FZD3) gene. We examined a possible association in a Japanese sample of schizophrenia, bipolar disorder, unipolar depression and controls with four single nucleotide polymorphisms (SNPs), tested in previous reports. We failed to find significant association in the four SNPs or haplotype analysis. The FZD3 gene might not play a role in conferring susceptibility to major psychosis in our sample.

Haplotype association between GABAA receptor gamma2 subunit gene (GABRG2) and methamphetamine use disorder

Psychostimulant use disorder and schizophrenia have a substantial genetic basis. Evidence from human and animal studies on the involvement of the gamma-aminobutyric acid (GABA) system in methamphetamine (METH) use disorder and schizophrenia is mounting. As we tested for the association of the human GABA(A) receptor gamma 2 subunit gene (GABRG2) with each diagnostic group, we used a case-control design with a set of 178 subjects with METH use disorder, 288 schizophrenics and 288 controls. First, we screened 96 controls and identified six SNPs in GABRG2, three of whom we newly reported. Next, we selected two SNPs, 315C>T and 1128+99C>A, as representatives of the linkage disequilibrium blocks for further case-control association analysis. Although no associations were found in either allelic or genotypic frequencies, we detected a haplotypic association in GABRG2 with METH use disorder, but not with schizophrenia. This finding partly replicates a recent case-control study of GABRG2 in METH use disorder, and thus indicates that GABRG2 may be one of the susceptibility genes of METH use disorder.

Blood lead and erythrocyte protoporphyrin levels in association with smoking and personal hygienic behaviour among lead exposed workers

AIMS

To investigate the effects of smoking and personal hygienic behaviour on blood lead (BPb) and free erythrocyte protoporphyrin levels (FEP) in lead exposed workers.

METHODS

Subjects were 105 lead exposed male workers in a battery recycling plant during the years 2000-03. BPb and FEP were measured as part of the ongoing occupational surveillance. Each worker completed a questionnaire for assessment of smoking and four measures of personal hygienic behaviour (glove and mask use, hand and face washing before meals during working hours).

RESULTS

Statistically significant decreases in mean BPb and FEP occurred during the three years. The proportion of BPb reduction in the non-smoking workers was significantly higher (mean 24.3%) than in the smoking workers (15.3%). When the workers were classified into three groups (excellent, good, and poor) based on the four personal hygienic behavioural indicators, the greatest decreases of BPb and FEP were observed in the non-smoking workers of the excellent group.

CONCLUSIONS

The consistent use of protection devices and cleanliness at work appeared to contribute to the lowering of BPb and FEP. Cessation of smoking in the workplace was also of importance.

No association with the calcineurin A gamma subunit gene (PPP3CC) haplotype to Japanese schizophrenia

Calcineurin, one of the serine/threonine protein phosphatase, comprises more than 1% of the total protein content in brain. This evidence points towards important roles of calcineurin in neural function. Miyakawa et al. reported that forebrain-specific calcineurin knockout mice showed the behavioral abnormalities that are often observed in schizophrenia patients. Based on this evidence, they suggested that calcineurin dysfunction could be involved in schizophrenia pathogenesis. Thereafter this report, Gerber et al. performed transmission disequilibrium test (TDT) studies and showed an evidence for a nominally significant over-transmission of a common haplotype of the human calcineurin A gamma subunit gene (PPP3CC). We performed association analysis of PPP3CC in Japanese sample of 457 schizophrenia cases and 429 controls. To our regret, we could not confirm the association with Japanese schizophrenia to PPP3CC including core at-risk haplotype. Our result suggests that PPP3CC may not play a major role in Japanese schizophrenia.

Effect of propofol and isoflurane anaesthesia on the immune response to surgery

There are two major subpopulations of peripheral helper T lymphocytes: T helper 1 (Th1) and T helper 2 (Th2) cells. Surgical stress increases the number of Th2 cells, and decreases that of Th1 cells, resulting in a decrease in the Th1/Th2 ratio, and, consequently, in suppressed cell-mediated immunity. Since anaesthesia can suppress the stress response to surgery, it may inhibit the decrease in the Th1/Th2 ratio. Using flow cytometry, we studied whether propofol anaesthesia (n = 9) or isoflurane anaesthesia (n = 9) had more effect on the decrease in the Th1/Th2 ratio after surgery in patients undergoing craniotomy. The Th1/Th2 ratio decreased significantly after isoflurane anaesthesia (p = 0.011), while it did not change after propofol anaesthesia. The ratio was significantly lower with isoflurane than propofol (p = 0.009). Propofol anaesthesia attenuated the surgical stress-induced adverse immune response better than isoflurane anaesthesia.

Effect of DRD2, 5-HT2A, and COMT genes on antipsychotic response to risperidone

Risperidone is a widely used atypical antipsychotic with certain advantages over typical antipsychotics. Although variations in the efficacy of treatment with risperidone have been observed, no specific predictable marker has been identified as of yet. In all, 73 Japanese patients with schizophrenia were given risperidone for 8 weeks, and clinical symptoms were evaluated using the Positive and Negative Syndrome Scale (PANSS). Six candidate polymorphisms (HTR2A -1438G>A, 102T>C, H452Y; DRD2 -141delC, Taq I A; COMT V158M) were genotyped. The diplotype configuration for each individual was estimated by the maximum-likelihood method. Multiple linear regressions were used to analyze the effects of these haplotypes/genotype and other prognostic factors on PANSS scale performance. After adjustment for the effects of patient-related variables, HTR2A diplotype and COMT genotype, as well as other potential prognostic factors, did not significantly influence the clinical performance. A DRD2 haplotype tended to correlate with better clinical performance. Compared with patients who had Ins-A2/Ins-A2 diplotype (n=25), PANSS total scores of patients with Ins-A2/Del-A1 diplotype (n=10) showed 40% greater improvement (P=0.03). The PANSS total scores of patients with HTR2A A-T/A-T diplotype (n=22) tended to show 15% worse improvement compared with A-T/G-C diplotype (n=33) (P=0.06). These results should be treated with caution because of limitations due to small sample size, heterogeneity of patients with respect to past antipsychotic use history, and no correction for multiple corrections. However, the present findings generate important hypotheses in a sample of Japanese schizophrenia patients that may lay the foundation for future pharmacogenomics investigations in other populations.

Association analysis of the ?308G > A promoter polymorphism of the tumor necrosis factor alpha (TNF-?) gene in Japanese patients with schizophrenia

Two research groups have thus far reported a significant association between schizophrenia and a promoter polymorphism (-308G > A) of the gene encoding tumor necrosis factor alpha (TNF-alpha), while contradictive negative results have also been reported. We examined the possible association in a Japanese sample of 297 schizophrenia cases and 458 controls. Allele frequencies of both the patients and controls were very low (1.5% and 0.8%, respectively), and the difference was not statistically significant. We conclude that the effect of the -308G > A polymorphism on the development of schizophrenia is, if any, weak and the majority of Japanese schizophrenics are unrelated to the -308G > A polymorphism of the TNF-alpha gene.

Association of a haplotype in the serotonin 5-HT4 receptor gene (HTR4) with Japanese schizophrenia

The serotonin 5-HT(4) receptor (5-HT(4)) is implicated in cognitive function, of which impairment is hypothesized as one of the core disturbances of schizophrenia. Linkage analysis shows that 5q33.2, in which HTR4 is located, is schizophrenia-susceptibility loci. We therefore hypothesized that variation in the 5-HT(4) receptor gene (HTR4) modifies genetic susceptibility to schizophrenia. HTR4 coding regions and introns that include the branch sites of HTR4 were investigated in 96 unrelated Japanese schizophrenics using denaturing high-performance liquid chromatography analysis. One silent single nucleotide polymorphism (SNP) within the coding region and six intronic SNPs were detected. 353 + 6G > A was located in the branch site that could be effect to RNA splicing. None of the four SNPs, in which rare-allele frequencies were more than 10% was associated with 189 schizophrenics, in comparison to 299 controls. However, a highly significant association between schizophrenia and haplotype A-T (OR = 0.13 [0.03-0.58]) was detected. These findings suggest that haplotype A-T itself may inhibit the occurrence of schizophrenia, or that another susceptible genetic variants may exist within linkage disequilibrium.

New animal models for encapsulating peritoneal sclerosis--role of acidic solution

OBJECTIVE

Encapsulating peritoneal sclerosis (EPS), in which all or part of the intestine is enveloped in a fibrous ball resembling a cocoon, is a serious complication of peritoneal dialysis (PD). The aim of the present study was to investigate whether pH-neutral or acidic dialysis solutions induce peritoneal fibrosis.

DESIGN

We divided 18 male Wistar-Kyoto (WKY) rats into three groups and dialyzed them with various solutions as follows: group I, 10 mL acidic dialysis solution (pH 3.8, containing 1.35% glucose), n = 6; group II, 10 mL pH 5.0 dialysis solution, n = 6; and group III, 10 mL neutral dialysis solution (pH 7.0), n = 6. Peritoneal catheters were inserted, and dialysis solution was injected every day for 40 days. At the end of the experiment, a peritoneal equilibration test (PET) was performed. Expression of mRNA of aquaporins 1 and 4 (AQP-1 and AQP-4) in the peritoneum were studied by semiquantitative reverse-transcriptase polymerase chain reaction (RT-PCR).

RESULTS

In rats treated with pH 3.8 dialysis solution, necropsy findings revealed features identical to those of EPS. The typical appearance was of granulation tissue or fibrotic tissue (or both) covering multiple surfaces. Multiple adhesions were present. In microscopic examinations, peritoneal fibrosis and loss of mesothelium were found. In rats treated with pH 7.0 dialysis solution, no signs of EPS were seen. In rats treated with pH 5.0 dialysis solution, milder changes (subserosal thickening and partial adhesion of the peritonea) were observed. The mRNA of AQP-1 and AQP-4 were expressed in the peritonea of the rats. The expression of the AQPs was significantly suppressed in rats treated with pH 3.8 dialysis solution.

CONCLUSIONS

In rats, long-term intraperitoneal injection of acidic dialysis solution produced features typical of EPS in humans. Newly developed neutral dialysis solutions protected the against the development of EPS during peritoneal dialysis in rats.

A novel apolipoprotein E5 variant with a 24-bp insertion causing hyperlipidemia

A tandem 24-bp insertion in the apolipoprotein E (apo E) gene was detected in a patient with elevated triglyceride, apolipoprotein (apo) CII, and apo CIII levels. This novel variant, apo E5ss, showed in position apo E5 by isoelectric focusing and was of larger molecular weight than apo E3 during two-dimensional gel electrophoresis. Polymerase chain reaction-single strand conformation polymorphism analysis using the primer pairs that cover all the coding regions was useful for rapid detection of the variant of the apo E allele. Apo E5ss may have a 24-bp insertion caused by slipped mispairing, resulting in a tandem duplication of amino acid residues 135-142 [APOE, 24-BP INS, DUP CODONS 135-142]. The proband was the only person with apo E5ss among the 806 Japanese males that we examined. We inspected six other reported apo E5 variants in the literature.

Renin-angiotensin system plays an important role in the regulation of water transport in the peritoneum

The present study was carried out to investigate changes in the expression of aquaporins (AQPs) in the peritoneum. The effects of the renin-angiotensin system on the expression of AQPs with and without angiotensin converting enzyme inhibitor (ACEI) or angiotensin II type 1a receptor blocker (ARB) were then examined. We divided 20 male Wistar Kyoto (WKY) rats into four groups, dialyzed with these solutions: saline; 10% glucose (TZ); 10% glucose plus benazepril (ACEI: 4 mg/kg daily); and 10% glucose plus valsartan (ARB: 10 mg/kg daily). The ACEI and ARB were administered into the peritoneum for 7 days. Expression of AQP-1-AQP-4 mRNA was studied by semiquantitative reverse-transcription polymerase chain reaction (RT-PCR). Ultrafiltration volume (UFV) and peritoneal function were measured by peritoneal equilibration test (PET). In the TZ group, expression of AQP-1 and AQP-4 was enhanced in parallel with an increment in UFV. Expression of AQP-1 and AQP-4 was also observed in the mesothelium by immunofluorescence microscopy. On the other hand, in ACEI- and ARB-treated rats, expression of AQP-1 and AQP-4 was significantly suppressed, accompanied by loss of UFV. Our results suggest that the renin-angiotensin system plays an important role in the regulation of water transport in the peritoneum. Administration of ACEI or ARB in patients undergoing continuous ambulatory peritoneal dialysis should be carried out with caution.

The mechanisms of the vulnerable window: the role of virtual electrodes and shock polarity

Vulnerability and defibrillation are mechanistically dependent upon shock strength, polarity, and timing. We have recently demonstrated that shock-induced virtual electrode polarization (VEP) may induce reentry. However, it remains unclear how the VEP mechanism may explain the vulnerable window and polarity dependence of vulnerability. We used a potentiometric dye and optical mapping to assess the anterior epicardial electrical activity of Langendorff-perfused rabbit hearts (n = 7) during monophasic shocks (+/-100 V and +/-200 V, duration of 8 ms) applied from a transvenous defibrillation lead at various coupling intervals. Arrhythmias were induced in a coupling interval and shock polarity dependent manner: (i) anodal and cathodal shocks induced arrhythmias in 33.2 +/- 30.1% and 53.1 +/- 39.3% cases (P < 0.01), respectively, and (ii) the vulnerable window was located near the T-wave. Optical maps revealed that VEP was also modulated by the coupling interval and shock polarity. Recovery of excitability produced by negative polarization, known as de-excitation, and the resulting reentry was more readily achieved during the relative refractory period than the absolute refractory period. Furthermore, anodal shocks produced wavefronts propagating in an inward direction with respect to the electrode, whereas cathodal shocks propagated in an outward direction. Wavefronts produced by anodal shocks were more likely to collide and annihilate each other than those caused by cathodal shocks. The probability of degeneration of the VEP-induced phase singularity into a sustained arrhythmia depends upon the gradient of VEP and the direction of the VEP-induced wavefront. The VEP gradient depends upon the coupling interval, while the direction depends upon shock polarity; these factors explain the vulnerable window and polarity-dependence of vulnerability, respectively.

[Electrophysiological mechanism of combination therapy with disopyramide and propranolol for paroxysmal atrial fibrillation]

OBJECTIVES

Combined administration of propranolol and disopyramide treatment often leads to better results in patients with atrial fibrillation refractory to only disopyramide administration. The electrophysiological mechanism of this combination therapy was investigated.

METHODS

Nineteen patients with paroxysmal atrial fibrillation without organic heart disease were studied. The indices for atrial vulnerability were compared in the control state, 10 min after injection of disopyramide (2 mg/kg) and 10 min after additional administration of propranolol (0.2 mg/kg).

RESULTS

Administration of both drugs did not significantly change the percentage fragmented atrial activity and the interatrial conduction delay. Disopyramide increased the atrial effective refractory period and the wavelength index, defined as the ratio of the atrial effective refractory period to the interatrial conduction delay and represented the length of the reentry circuit. Additional injection of propranolol caused further increases in both values.

CONCLUSIONS

Combination therapy with disopyramide and propranolol improves atrial vulnerability by increasing the wavelength.

Direct evidence of the role of virtual electrode-induced phase singularity in success and failure of defibrillation

INTRODUCTION

We recently demonstrated that virtual electrode-induced phase singularity is responsible for arrhythmogenesis during T wave shocks and explains the upper and lower limits of vulnerability. Furthermore, we suggested that the same mechanism might be responsible for defibrillation failure. The aim of this study was to experimentally support this hypothesis.

METHODS AND RESULTS

We used the voltage-sensitive dye di-4-ANEPPS and fast imaging to assess electrical activity in Langendorff-perfused rabbit hearts. Ventricular arrhythmias were induced by monophasic shocks applied during T wave. Three types of defibrillation shocks (n = 79) were delivered from an intravenous right ventricular electrode: monophasic (8 msec), optimal biphasic (8/8 msec, 2/1 leading-edge voltage ratio), and nonoptimal biphasic (8/8 msec, 1/1 leading-edge voltage ratio). We found that a monophasic shock extinguished arrhythmic pattern of electrical activity via a virtual electrode polarization effect. However, the virtual electrode polarization was likely to produce phase singularities, leading to another arrhythmia and defibrillation failure. Nonoptimal biphasic shocks produced similar effects. Optimal biphasic shocks were successful because the first phase of the shock erased the arrhythmia via the virtual electrodes effect, whereas the second phase canceled the virtual electrodes, eliminating the substrate for phase singularities and arrhythmia resulting from them.

CONCLUSION

Our data provide the first experimental support of the hypothesis implicating virtual electrode-induced phase singularity in defibrillation failure in the Langendorff-perfused rabbit heart. Optimal biphasic shock has a higher defibrillation efficacy because it does not produce virtual electrode-induced phase singularities.

New approach to biphasic waveforms for internal defibrillation: fully discharging capacitors

INTRODUCTION

The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform.

METHODS AND RESULTS

Eight full-discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase-1 capacitors (30, 60, and 90 microF) and phase-2 capacitors (1/3, 2/3, and 1.0 times the phase-1 capacitor) were tested and compared to a single-capacitor waveform (120 microF, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23+/-2 kg). In the full-discharge waveforms, phase-2 peak voltage was equal to phase-1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten-step Bayesian process. Full-discharge waveforms with phase-2 capacitors of < or =40 microF had the same E50 (6.7+/-1.7 J to 7.3+/-3.9 J) as the single-capacitor truncated waveform (7.3+/-3.7 J), whereas waveforms with phase-2 capacitors of > or =60 microF had an extremely high E50 (14.5+/-10.8 J or greater, P < 0.05). Moreover, of the former set of energy-efficient waveforms, those with phase-1 capacitors of > or =60 microF additionally exhibited V50s that were equivalent to the V50 of the single-capacitor waveform (344+/-65 V to 407+/-50 V vs 339+/-83 V).

CONCLUSION

Defibrillation efficacy can be maintained in a full-discharge, two-capacitor waveform with the proper choice of capacitors.

Structural analysis of a rare rearranged Y chromosome and its bearing on genotype-phenotype correlation

We report on a 9-year-old boy with a rare rearranged Y chromosome and borderline short stature (-2.0 SD). Standard metaphase chromosome analysis indicated a 46,X,i(Y)(q1O) karyotype, but high resolution G-banding showed an asymmetric band pattern for the rearranged Y chromosome. FISH and DNA studies for a total of 15 different Y chromosomal loci or regions showed that the rearranged Y chromosome was accompanied by: 1) a partial deletion of the short arm pseudoautosomal region (PAR1) involving SHOX, with the breakpoint distal to DXYS85; and 2) a partial duplication of Yq, with the breakpoint proximal to DAZ. The karyotype was determined as 46,X,?i(Y)(q1O).ish der(Y)(Yqter--> Yp11.3::Yq11.2-->Yqter)(DAZ++,DYZ3+,SRY +, SHOX-). The X chromosome and the autosomes were normal. The results suggest that haploinsufficiency of SHOX is primarily responsible for the borderline short stature, and that the deletion of the PAR1 may result in spermatogenic failure due to defective X-Y pairing and recombination in the PAR1.

Girl with accelerated growth, hearing loss, inner ear anomalies, delayed myelination of the brain, and del(22)(q13.1q13.2)

We report on an 18-month-old Japanese girl with 46,XX,del(22)(q13.1q13.2). To our knowledge, this is the first report of a case of interstitial deletion of a 22q13.1-q13.2 segment. Clinical features included hearing loss accompanied by inner ear anomalies, hypotonia and minor anomalies, such as a long philtrum, full eyelids, epicanthus, left transverse palmar crease and psychomotor developmental delay. Despite the chromosomal deletion, her physical growth was accelerated: her height was between the 75th and 90th percentiles for her age. Her brain MRI showed signs of delayed myelination. The three-dimensional MRI of the inner ear showed abnormalities of the cochlea and vestibule in both ears. Clinical features of the patient are similar to those of a patient with a del(22)(q13.1q13.33) karyotype previously reported by Romain et al.

Voltage dependence of ICD lead polarization and the effect of iridium oxide coating

Nonthoracotomy leads (NTLs) with an iridium oxide (IROX) coating exhibit lower defibrillation thresholds (DFTs) than uncoated NTLs. We tested whether adding an IROX coating to an active pectoral can would influence defibrillation efficacy. However, the primary purpose of this study was to examine the impedance changes that occur at different voltages for uncoated titanium NTLs and identical NTLs with an IROX coating. We studied anesthetized pigs with an NTL placed in the right ventricle and coupled this to an active pectoral can. Biphasic waveform DFTs were obtained for the four NTLs and can combinations: uncoated NTL and uncoated can, uncoated NTL and IROX can, IROX NTL and uncoated can, and IROX NTL and IROX can. The respective energy DFTs were: 23.6 +/- 6.9, 24.1 +/- 6.7, 21.3 +/- 6.0, and 21.4 +/- 7.0 J. The IROX NTL DFTs were significantly lower (P < 0.05) than the uncoated NTL DFTs (either can), confirming our previous study. We then used a low tilt monophasic waveform to assess impedance changes. The impedance rise for each NTL/can combination was measured at 50, 100, 300, and 700 V. Comparisons of impedance changes between voltage levels showed that the impedance rise was inversely related to voltage and was greatest with uncoated NTLs. The IROX coating of the NTL reduced the impedance rise at all shock voltages, but was particularly beneficial at the lower voltages. No advantage was seen when the pectoral can was coated with IROX regardless of which NTL was used. Our results suggest that low voltage applications, such as atrial defibrillation, would benefit most from the IROX-coated NTL, and further studies are warranted in this area.

External exponential biphasic versus monophasic shock waveform: efficacy in ventricular fibrillation of longer duration

Ventricular fibrillation (VF) duration may be a factor in determining the defibrillation energy for successful defibrillation. Exponential biphasic waveforms have been shown to defibrillate with less energy than do monophasic waveforms when used for external defibrillation. However, it is unknown whether this advantage persists with longer VF duration. We tested the hypothesis that exponential biphasic waveforms have lower defibrillation energy as compared to exponential monophasic waveforms even with longer VF duration up to 1 minute. In a swine model of external defibrillation (n = 12, 35 +/- 6 kg), we determined the stored energy at 50% defibrillation success (E50) after both 10 seconds and 1 minute of VF duration. A single exponential monophasic (M) and two exponential biphasic (B1 and B2) waveforms were tested with the following characteristics: M (60 microF, 70% tilt), B1 (60/60 microF, 70% tilt/3 ms pulse width), and B2 (60/20 microF, 70% tilt/3 ms pulse width) where the ratio of the phase 2 leading edge voltage to that of phase 1 was 0.5 for B1 and 1.0 for B2. E50 was measured by a Bayesian technique with a total often defibrillation shocks in each waveform and VF duration randomly. The E50 (J) for M, B1, and B2 were 131 +/- 41, 57 +/- 18,* and 60 +/- 26* with 10 seconds of VF duration, respectively, and 114 +/- 62, 77 +/- 45,* and 72 +/- 53* with 1 minute of VF duration, respectively (*P < 0.05 vs M). There was no significant difference in the E50 between 10 seconds and 1 minute of VF durations for each waveform. We conclude that (1) the E50 does not significantly increase with lengthening VF durations up to 1 minute regardless of the shock waveform, and (2) external exponential biphasic shocks are more effective than monophasic waveforms even with longer VF durations.

Fully discharging phases. A new approach to biphasic waveforms for external defibrillation

BACKGROUND

Phase-2 voltage and maximum pulse width are dependent on phase-1 pulse characteristics in a single-capacitor biphasic waveform. The use of 2 separate output capacitors avoids these limitations and may allow waveforms with lower defibrillation thresholds. A previous report also suggested that the optimal tilt may be >70%. This study was designed to determine an optimal biphasic waveform by use of a combination of 2 separate and fully (95% tilt) discharging capacitors.

METHODS AND RESULTS

We performed 2 external defibrillation studies in a pig ventricular fibrillation model. In group 1, 9 waveforms from a combination of 3 phase-1 capacitor values (30, 60, and 120 microF) and 3 phase-2 capacitor values (0=monophasic, 1/3, and 1.0 times the phase-1 capacitor) were tested. Biphasic waveforms with phase-2 capacitors of 1/3 times that of phase 1 provided the highest defibrillation efficacy (stored energy and voltage) compared with corresponding monophasic and biphasic waveforms with the same capacitors in both phases except for waveforms with a 30-microF phase-1 capacitor. In group 2, 10 biphasic waveforms from a combination of 2 phase-1 capacitor values (30 and 60 microF) and 5 phase-2 capacitor values (10, 20, 30, 40, and 50 microF) were tested. In this range, phase-2 capacitor size was more critical for the 30-microF phase-1 than for the 60-microF phase-1 capacitor. The optimal combinations of fully discharging capacitors for defibrillation were 60/20 and 60/30 microF. Conclusions-Phase-2 capacitor size plays an important role in reducing defibrillation energy in biphasic waveforms when 2 separate and fully discharging capacitors are used.

Autonomic modification of the atrioventricular node during atrial fibrillation: role in the slowing of ventricular rate

BACKGROUND

Postganglionic vagal stimulation (PGVS) by short bursts of subthreshold current evokes release of acetylcholine from myocardial nerve terminals. PGVS applied to the atrioventricular node (AVN) slows nodal conduction. However, little is known about the ability of PGVS to control ventricular rate (VR) during atrial fibrillation (AF).

METHODS AND RESULTS

To quantify the effects and establish the mechanism of PGVS on the AVN, AF was simulated by random high right atrial pacing in 11 atrial-AVN rabbit heart preparations. Microelectrode recordings of cellular action potentials (APs) were obtained from different AVN regions. Five intensities and 5 modes of PGVS delivery were evaluated. PGVS resulted in cellular hyperpolarization, along with depressed and highly heterogeneous intranodal conduction. Compact nodal AP exhibited decremental amplitude and dV/dt and multiple-hump components, and at high PGVS intensities, a high degree of concealed conduction resulted in a dramatic slowing of the VR. Progressive increase of PGVS intensity and/or rate of delivery showed a significant logarithmic correlation with a decrease in VR (P<0.001). Strong PGVS reduced the mean VR from 234 to 92 bpm (P<0.001). The PGVS effects on the cellular responses and VR during AF were fully reproduced in a model of direct acetylcholine injection into the compact AVN via micropipette.

CONCLUSIONS

These studies confirmed that PGVS applied during AF could produce substantial VR slowing because of acetylcholine-induced depression of conduction in the AVN.

Enhancing effects of salicylate on tonic and phasic block of Na+ channels by class 1 antiarrhythmic agents in the ventricular myocytes and the guinea pig papillary muscle

OBJECTIVE

To study the interaction between salicylate and class 1 antiarrhythmic agents.

METHODS

The effects of salicylate on class 1 antiarrhythmic agent-induced tonic and phasic block of the Na+ current (INa) of ventricular myocytes and the upstroke velocity of the action potential (Vmax) of papillary muscles were examined by both the patch clamp technique and conventional microelectrode techniques.

RESULTS

Salicylate enhanced quinidine-induced tonic and phasic block of INa at a holding potential of -100 mV but not at a holding potential of -140 mV; this enhancement was accompanied by a shift of the hinfinity curve in the presence of quinidine in a further hyperpolarized direction, although salicylate alone did not affect INa. Salicylate enhanced the tonic and phasic block of Vmax induced by quinidine, aprindine and disopyramide but had little effect on that induced by procainamide or mexiletine; the enhancing effects were related to the liposolubility of the drugs.

CONCLUSIONS

Salicylate enhanced tonic and phasic block of Na+ channels induced by class 1 highly liposoluble antiarrhythmic agents. Based on the modulated receptor hypothesis, it is probable that this enhancement was mediated by an increase in the affinity of Na+ channel blockers with high lipid solubility to the inactivated state channels.

Mechanism of inhibition of the Na current by tocainide in guinea-pig isolated ventricular cells

Tocainide blocked the Na current (I(Na)) in ventricular myocytes in either a tonic or a phasic block manner, having a higher affinity for the inactivated state (K(di) = 18 microM) than for the rested state (Kd(rest) = 606 microM). The degree of phasic block was enhanced and the onset of phasic block was faster with an increase in pulse duration as well as at less-negative holding potential (HP). The recovery-time constant from the phasic block of I(Na) induced by tocainide was independent of either the HP or the removal of fast inactivation. After removal of fast inactivation, tocainide showed the pulse-duration dependency of phasic block but not the voltage dependency. These results suggest that tocainide could bind to the inactivated-state receptor through the hydrophilic pathway and leave the receptor through the hydrophobic pathway, producing the tonic and phasic block of I(Na).

Effects of amlodipine on native cardiac Na+ channels and cloned alpha-subunits of cardiac Na+ channels

The inhibitory effects of amlodipine besilate (CAS 11470-99-6) on the native Na+ current (INa) and cloned human cardiac Na+ channel alpha subunit (hH1) were studied by whole cell patch clamp techniques. Amlodipine produced tonic block of INa in a concentration- and holding potential (HP)-dependent manner with hyperpolarization of H infinity. Amlodipine produced phasic blockade of INa, which was dependent on HP and pulse duration. Amlodipine produced tonic blockade of hH1 in a concentration-dependent manner with 1 : 1 stoichiometry, and phasic blockade of hH1 which was dependent on the pulse duration. Amlodipine blocked INa in a voltage- and frequency-dependent manner via affinity to the resting as well as inactivated conformations of the alpha subunit.

Biventricular shocking leads improve defibrillation efficacy

INTRODUCTION

A single lead active can configuration has been widely used in patients with life-threatening ventricular arrhythmias. Occasionally, however, such a defibrillation lead configuration may not achieve adequate defibrillation threshold (DFT). The purpose of this study was to determine whether addition of a left ventricular (LV) lead can improve defibrillation efficacy.

METHODS AND RESULTS

Three transvenous defibrillation leads (8.3-French with a 5-cm long unipolar coil) were placed in the right ventricle (RV), LV, and superior vena cava (SVC), along with an active can (92 cm2) in the left subpectoral area. The DFT stored energy of seven combinations of these defibrillation leads were compared in a pig ventricular fibrillation model using a biphasic defibrillation waveform (125 microF, 6.5/3.5 msec). A biventricular leads active can configuration in which the RV and LV leads were of the same polarity reduced the DFT stored energy by approximately 35% when compared to a single RV lead active can configuration (9.6 +/- 3.0 J vs 15.0 +/- 7.2 J, respectively, P = 0.02). Moreover, adding a SVC lead further reduced the DFT energy (8.4 +/- 3.3 J).

CONCLUSION

A biventricular leads active can configuration can significantly improve defibrillation efficacy as compared to a single lead active can configuration. In such a defibrillation lead configuration, the polarity of RV and LV leads should be the same.

XX-male syndrome bearing the sex-determining region Y

The case of a 25-year-old man who presented for evaluation of infertility is described. The physical examination revealed testicular atrophy without gynecomastia. Repeated seminal analyses showed azoospermia, and serum hormonal levels suggested a state of a hypergonadotropic hypogonadism. Chromosomal analysis demonstrated 46XX. Polymerase chain reaction revealed the existence of a sex-determining region Y. The etiology of this rare sex reversal syndrome is discussed and cases reported in Japan are reviewed.

Isoproterenol induced cardiovascular hypersensitiviy in nonpheochromocytoma patients with paroxysmal hyperadrenergic symptoms

The objective of this study was to determine whether graded isoproterenol infusion test identifies a specific hypersensitivity response of the LV diastolic relaxation properties in nonpheochromocytoma patients with paroxysmal symptoms of hyperadrenergic surges. We hypothesized that patients with hyperadrenergic surges, not due to pheochromocytoma, have hypersensitivity of cardiac beta-adrenergic receptor responses to exogenous catecholamines, resulting in enhancement of LV relaxation. We assessed the physiological beta 1 and beta 2 receptor responsiveness to graded isoproterenol infusion (0.01, 0.02, 0.03 and 0.04 microgram/kg per min) in 32 patients presented with hyperadrenergic surges not due to pheochromocytoma. Two major observations were made. First, systemic hemodynamic evaluation using 99m Technetium first pass method revealed hyperkinetic state only in 21 patients (20 females and 1 male; aged 31 +/- 9 years); the other 11 patients were without hyperkinetic circulatory state (10 females and 1 male; aged 41 +/- 9 years). At baseline, plasma catecholamines were not significantly different between the two groups. The baseline corrected LV peak filling and ejection rates (cPFR and cPER) were significantly higher in hyperkinetic group (cPFR: 10 +/- 2 vs 8 +/- 2 x 10(-2) Hz/ms, P = 0.03; cPER: 11 +/- 2 vs 8 +/- 1 x 10(-2) Hz/ms, P = 0.002) and their baseline HR was faster (85 +/- 16 vs 70 +/- 9 beats/min, P = 0.006). Second, the cardiac and vascular responses to isoproterenol infusion were compared between these two groups. During the graded isoproterenol infusion, the response of HR, systolic, and diastolic BP were not significantly different between the two groups at all doses of isoproterenol, but cPFR and cPER had a more marked response to the lowest dose of 0.01 mg/kg per min in the hyperkinetic group. Thus, the graded isoproterenol infusion test can differentiate between two groups of nonpheochromocytoma patients presenting with paroxysmal symptoms of hyperadrenergic surges. Only patients with baseline hyperkinetic hemodynamic profile had accentuated cardiac hyperresponsiveness to a low dose of isoproterenol. We concluded that cPFR and cPER is a more sensitive index to assess the response to isoproterenol, because of metabolic determinants affecting the rate of change in LV volume.

Development of primary hypothyroidism with the appearance of blocking-type antibody to thyrotropin receptor in Graves' disease in late pregnancy

Spontaneous remission of Graves' disease with a decrease of thyroid stimulating antibody (TSAb) activity is commonly observed in pregnancy. In this article, however, a Graves' patient who developed primary hypothyroidism with an appearance of thyroid stimulation-blocking antibody (TSBAb) activity in late pregnancy is reported. A 25-year-old woman presented with clinical and biochemical hyperthyroidism with an elevation of 99mTcO4- thyroid uptake (4.7%; normal range, 0.7%-3.0%) and mildly elevated activity of thyrotropin-binding inhibitory immunoglobulin (TBII; 30.4%). She was euthyroid with normal TBII (8.0%) and TSAb (126%) before pregnancy, when the patient was taking a 5-mg daily dose of methimazole (MMI). MMI was stopped by the patient when she became pregnant. Subsequently, the patient progressed into primary hypothyroidism with a marked elevation of TBII activity (78.4%) in the third trimester of the pregnancy (at that time, TSAb activity was not detected). TSBAb measured 2 weeks later was detected at the activity of 85.0%. Replacement therapy was initiated with levothyroxine (LT4) (0.05-0.1 mg/day), which was discontinued on the 55th day postpartum because of the onset of mild thyrotoxicosis followed by short-term euthyroid state despite high TSBAb activity. Subsequently, because the patient developed primary hypothyroidism 5 months after delivery, replacement therapy with LT4 (0.1-0.125 mg/day) was readministered. Thus, it is suggested that the development of hypothyroidism with the appearance of TSBAb in Graves' patients can occur even in late pregnancy.

Optimal small-capacitor biphasic waveform for external defibrillation: influence of phase-1 tilt and phase-2 voltage

BACKGROUND

Biphasic waveforms have been reported to be more efficacious than monophasic waveforms for external defibrillation. This study examined the optimal phase-1 tilts and phase-2 leading-edge voltages with small capacitors (60 and 20 microF) for external defibrillation. We also assessed the ability of the "charge-burping" model to predict the optimal waveforms.

METHODS AND RESULTS

Two groups of studies were performed. In group 1, 9 biphasic waveforms from a combination of 3 phase-1 tilt values (30%, 50%, and 70%) and 3 phase-2 leading-edge voltage values (0.5, 1.0, and 1.5 times the phase-1 leading-edge voltage, V1) were tested. Phase-2 pulse width was held constant at 3 ms in all waveforms. Two separate 60- microF capacitors were used in each phase. The energy value that would produce a 50% likelihood of successful defibrillation (E50) decreased with increasing phase-1 tilt and increased with increasing phase-2 leading-edge voltage except for the 30% phase-1 tilt waveforms. In group 2, 9 waveforms were identical to the waveforms in group 1, except for a 20- microF capacitor for phase 2. E50 decreased with increasing phase-1 tilt. Phase-2 leading-edge voltage of 1.0 to 1.5 V1 appeared to minimize E50 for phase-1 tilt of 50% and 70% but worsened E50 for phase-1 tilt of 30%. There was a significant correlation between E50 and residual membrane voltage at the end of phase 2, as calculated by the charge-burping model in both groups (group 1, R2=0.47, P<0.001; group 2, R2=0.42, P<0.001).

CONCLUSIONS

The waveforms with 70% phase-1 tilt were more efficacious than those with 30% and 50%. The relationship of phase-2 leading-edge voltage to defibrillation efficacy depended on phase-2 capacitance. The charge-burping model predicted the optimal external biphasic waveform.

Activation mapping from the coronary sinus may be limited by anatomic variations

The purpose of this study was to examine the anatomic relationship between the mitral annulus (MA) and the coronary sinus (CS). Fifty consecutive hearts of 31 men and 19 women, 63.5 +/- 13.7 years of age, were examined at autopsy. MA was divided perpendicularly to the annular plane into an anteromedial block and a posterolateral block by sectioning from the CS ostium through the center of MA. The posterolateral block was subdivided radially into five equal sections at 36 degrees, 72 degrees, 108 degrees, 144 degrees, and 180 degrees. The distance from the ventricular endocardium under MA to the nearest wall of CS (D) was measured in each cross-section. D measured 9.7 +/- 2.3, 10.9 +/- 3.3, 10.2 +/- 3.6, 9.2 +/- 3.4, and 8.2 +/- 2.9 mm at 36 degrees, 72 degrees, 108 degrees, 144 degrees, and 180 degrees, respectively. D at 72 was significantly longer than at 144 degrees and 180 degrees (P < 0.01). Likewise, D at 108 degrees was significantly longer than at 144 degrees and 180 degrees (P < 0.05). The population was divided according to the morphology into five patterns. "Type C," the pattern that separated in the middle section and then reapproximated, was more common (66%) than any other pattern. D was confirmed to be longest at the level of the 72 degrees section, corresponding to a left posterolateral free-wall location. The potential mapping in CS would be easily modified by this anatomic feature. When mapping activation from the CS, the electrophysiological data should be interpreted in light of these anatomic findings.

Excess urate excretion correlates with severely acidic urine in patients with renal hypouricemia

We evaluated the renal handling of urate in 12 Japanese renal hypouricemia patients, and studied the relationship between the renal handling of urate and the urinary pH. The patients were classified into the 4 subtypes of renal hypouricemia: (defective presecretory reabsorption (Pre), defective postsecretory reabsorption (Post), enhanced tubular secretion (Secretion), and defective presecretory and postsecretory reabsorption (Pre&Post) as based on a pharmacological test. Seven patients showed acid urine with a urinary pH of less than 5.9, although this was not accompanied by any abnormality of blood pH, partial pressure of carbon dioxide (PaCO2), or blood HCO3-. The urinary pH in the morning significantly correlated with the ratio of urate clearance to creatinine clearance in the morning, whereas the urinary urate concentration in the morning did not correlate with the urinary pH in the morning. In the Pre&Post patients, the urate excretion was higher and the urinary pH was more acidic compared to the other subtypes. The administration of K+-, Na+-citrate significantly alkalized the urinary pH in the patients with renal hypouricemia. These results suggest that the acidic urine was significantly related to the Pre&Post subtype of renal hypouricemia with the higher urate excretion, and that this subtype might be a risk factor for complications in renal hypouricemia. The alkalization of urine might be a useful treatment for the complication of renal hypouricemia.

Idiopathic left ventricular tachycardia with block between purkinje potential and ventricular myocardium

We performed radiofrequency current catheter ablation in a patient with idiopathic LV. While mapping the inferoapical LV septum during tachycardia, spontaneous termination of tachycardia was observed with block between Purkinje (P) potential and ventricular electrogram (P-V block). The cycle length of the tachycardia was associated with prolongation of P-P interval and P-V interval. P potential recording at this site was earliest and at very low amplitude during tachycardia. The radiofrequency current at this site was successful. These findings indicated that Purkinje fiber was a critical part of the tachycardia circuit. Ablation was successful at a site where both an earliest and low amplitude P potential was recorded during tachycardia, and where P-V block that was induced by catheter manipulation was observed during tachycardia.

Usefulness of plasma catecholamines during head-up tilt as a measure of sympathetic activation in vasovagal patients

Vasovagal syncope is a common clinical disorder which has been traditionally related to a vasovagal reflex precipitated by an initial excess sympathetic stimulation. We hypothesized that the increase in plasma catecholamines during head-up tilt is more accentuated in patients with tilt induced vasovagal syncope. To test this hypothesis, plasma catecholamines were measured in supine posture and during head-up tilt in patients with a history suggestive of vasovagal syncope. Of these, 13 had a normal response to tilt (nonvasovagal group; age 41 +/- 19 [SD]years) and 11 had a vasovagal response to tilt (vasovagal group; 39 +/- 20 years). In the supine posture at rest, plasma epinephrine and norepinephrine were not significantly different between the nonvasovagal and the vasovagal groups (39 +/- 28 ng/L vs 46 +/- 38 ng/L, P = 0.5792, 335 +/- 158 ng/L vs 304 +/- 124 ng/L, P = 0.6007, respectively). Furthermore, the tilt induced changes in plasma epinephrine and norepinephrine were not different between the two groups (20 +/- 20 ng/L vs 35 +/- 55 ng/L, P = 0.3562, 264 +/- 158 ng/L vs 242 +/- 205 ng/L, P = 0.7724, respectively) suggesting that differences in the hemodynamic response to tilt are not predictable by the supine levels of circulating plasma catecholamines, and that the extent of plasma catecholamines increase during tilt does not determine the hemodynamic outcome of the tilt test. Since orthostatic changes of plasma catecholamines could be influenced by volume factors, we assessed plasma renin activity and aldosterone as surrogates of blood volume. Baseline plasma renin activity and aldosterone were not significantly different between the two groups. We conclude that inasmuch as plasma catecholamines reflect the status of sympathetic activity, our data do not support the hypothesis that accentuation of sympathetic activity precedes necessarily the tilt induced vasovagal syncope. However, one should take in consideration that multiple factors may influence catecholamine levels and catecholamines kinetics. A hyperresponsiveness of beta-receptors to catecholamines in patients with vasovagal syncope may be suggested but needs to be tested.

Human ULK1, a novel serine/threonine kinase related to UNC-51 kinase of Caenorhabditis elegans: cDNA cloning, expression, and chromosomal assignment

The unc-51 gene, isolated from mutants of Caenorhabditis elegans exhibiting abnormal axonal extension and growth, encodes a novel serine/threonine kinase (K. Ogura, et al., 1994, Genes Dev. 8: 2389-2400). Here we report the molecular cloning and characterization of the human homologue of UNC-51, designated ULK1, for UNC-51 (C. elegans)-like kinase 1. Sequence analysis of the human ULK1 cDNA showed that an open reading frame is composed of 1050 amino acids with a calculated MW of 112.6 kDa and a pI of 8.80. Homology search analysis showed that ULK1 has 41% overall similarity to UNC-51 and 29% similarity to Apg1p of Saccharomyces cerevisiae. Phylogenetic analysis of ULK1, UNC-51, and Apglp suggested that they constitute a novel subfamily of serine/threonine kinases. Southern blot analyses suggested that the ULK1 gene spans 30-40 kb in the human genome as a single-copy gene. Zoo blot analysis indicated that ULK1 kinase is conserved among vertebrates including mammals, birds, reptiles, amphibians, and fish. Northern blot analysis revealed that ULK1 is ubiquitously expressed in adult human tissues such as skeletal muscle, heart, pancreas, brain, placenta, liver, kidney, and lung, whereas UNC-51 is specifically detected in the nervous system of C. elegans. Both FISH and RH mapping confirmed the regional localization of ULK1 to human chromosome 12q24.3.

Effects of respiration phase on ventricular defibrillation threshold in a hot can electrode system

The impedance of defibrillation pathways is an important determinant of ventricular defibrillation efficacy. The hypothesis in this study was that the respiration phase (end-inspiration versus end-expiration) may alter impedance and/or defibrillation efficacy in a "hot can" electrode system. Defibrillation threshold (DFT) parameters were evaluated at end-expiration and at end-inspiration phases in random order by a biphasic waveform in ten anesthetized pigs (body weight: 19.1 +/- 2.4 kg; heart weight: 97 +/- 10 g). Pigs were intubated with a cuffed endotracheal tube and ventilated through a Drager SAV respirator with tidal volume of 400-500 mL. A transvenous defibrillation lead (6 cm long, 6.5 Fr) was inserted into the right ventricular apex. A titanium can electrode (92-cm2 surface area) was placed in the left pectoral area. The right ventricular lead was the anode for the first phase and the cathode for the second phase. The DFT was determined by a "down-up down-up" protocol. Statistical analysis was performed with a Wilcoxon matched pair test. The median impedance at DFT for expiration and inspiration phases were 37.8 +/- 3.1 omega, and 39.3 +/- 3.6 omega, respectively (P = 0.02). The stored energy at DFT for expiration and inspiration phases were 5.7 +/- 1.9 J and 6.0 +/- 1.0 J, respectively (P = 0.594). Shocks delivered at end-inspiration exhibited a statistically significant increase in electrode impedance in a " hot can" electrode system. The finding that DFT energy was not significantly different at both respiration phases indicates that respiration phase does not significantly affect defibrillation energy requirements.

Venous dysfunction and the change of blood viscosity during head-up tilt

The precise stimulus that induces vasovagal syncope is still unclear. We have previously demonstrated that the peripheral distribution of blood volume (venous pooling) is a strong predictor of tilt induced vasovagal reaction. We hypothesized that an increase in venous pooling during tilt accentuates the measured increase in blood viscosity. This hypothesis is based on the previously demonstrated increase in venous pressure and subsequent increase in transcapillary fluid transudation during tilt. The increased blood viscosity, in turn, increases vascular shear rate, which may alter the vasoconstrictive and other cardiovascular responses to decreased preload. We measured blood viscosity (supine and tilt) in 56 patients with a history of orthostatic intolerance (37 with venous pooling [VP] and 19 without venous pooling [non-VP]). VP and non-VP were separated into subgroups based on blood pressure and heart rate response to tilt. There was a positive correlation between blood viscosity and plasma aldosterone in the supine. In the group as a whole, neither supine blood viscosity nor its increase during tilt differed between VP and non-VP. However, the tilt induced increase of blood viscosity was significant only in patients with tilt provoked tachycardia plus normal blood pressure response in VP group. We suggest that the increase of blood viscosity in this group led to the normal blood pressure response. The positive correlation between supine blood viscosity and supine plasma aldosterone indicates that the normal blood pressure response in this group possibly was via stimulation of the renin-angiotensin-aldosterone system.

Intracranial dural cyst

Intracranial dural cyst is a very rare congenital malformation. The presence of such a cyst was confirmed by means of computed tomography and magnetic resonance findings in a child with an enlargement of the head and developmental retardation and confirmed histologically in surgically obtained specimens of cyst wall.

Additional lead improves defibrillation efficacy with an abdominal 'hot can' electrode system

BACKGROUND

Although the left prepectoral site is preferred for "hot can" placement, this site is unavailable in some patients. We evaluated the influence of electrode location on defibrillation thresholds with alternative hot can and transvenous lead configurations.

METHODS AND RESULTS

Three interrelated studies were performed. In group 1, the importance of hot can location was investigated by pairing a right ventricular lead to five different hot can placement sites in seven pigs. The defibrillation energies for right pectoral, left pectoral, left subaxillary, and right and left abdominal hot can sites were 20.3+/-2.7,* 15.9+/-3.8, 14.9+/-2.5, 32.0+/-3.4,* and 30.0+/-3.4 J,* respectively (*P<.005 versus left pectoral and left subaxillary sites). In group 2, the value of a three-electrode configuration with an abdominal hot can placement was investigated by adding a subclavian vein lead to the pectoral or abdominal hot can configurations in seven pigs. The defibrillation energies for left pectoral and abdominal sites were 18.6+/-4.2 and 29.0+/-5.8 J (P=.0001), respectively. The addition of a right or left subclavian vein lead with an abdominal hot can reduced the threshold to 19.3+/-4.2* or 18.8+/-3.2,* respectively (*P=.0001 versus abdominal site). In group 3, the contribution of the abdominal hot can electrode to the three-electrode configuration was tested by a comparison with two purely transvenous two-electrode configurations in six pigs. The defibrillation energy (19.9+/-3.2 J) for the abdominal hot can with a subclavian vein lead was lower than the transvenous lead configurations with a subclavian vein (29.0+/-2.5 J, P=.0001) or a superior vena cava lead (30.7+/-3.7 J, P=.0001). The right ventricular lead was the sole cathode during the first phase of the biphasic shock in all experiments.

CONCLUSIONS

Defibrillation energy depends on the hot can placement site. The addition of a subclavian vein lead with an abdominal hot can improves defibrillation efficacy to the level of the pectoral placement and is better than a purely transvenous lead configuration.