High-affinity insulin binding: insulin interacts with two receptor ligand binding sites

The interaction of insulin with its receptor is complex. Kinetic and equilibrium binding studies suggest coexistence of high- and low-affinity binding sites or negative cooperativity. These phenomena and high-affinity interactions are dependent on the dimeric structure of the receptor. Structure-function studies of insulin analogs suggest insulin has two receptor binding sites, implying a bivalent interaction with the receptor. Alanine scanning studies of the secreted recombinant receptor implicate the L1 domain and a C-terminal peptide of the receptor alpha subunit as components of one ligand binding site. Functional studies suggest that the first and second type III fibronectin repeats of the receptor contain a second ligand binding site. We have used structure-directed alanine scanning mutagenesis to identify determinants in these domains involved in ligand interactions. cDNAs encoding alanine mutants of the holo-receptor were transiently expressed in 293 cells, and the binding properties of the expressed receptor were determined. Alanine mutations of Lys(484), Leu(552), Asp(591), Ile(602), Lys(616), Asp(620), and Pro(621) compromised affinities for insulin 2-5-fold. With the exception of Asp(620), none of these mutations compromised the affinity of the recombinant secreted receptor for insulin, indicating that the perturbation of the interaction is at the site of mutation and not an indirect effect on the interaction with the binding site of the secreted receptor. These residues thus form part of a novel ligand binding site of the insulin receptor. Complementation experiments demonstrate that insulin interacts in trans with both receptor binding sites to generate high-affinity interactions.

HIV protease genotype and viral sensitivity to HIV protease inhibitors following saquinavir therapy

OBJECTIVE

To examine the relationship between HIV protease genotype and altered protease inhibitor sensitivity of isolates from patients after therapy with saquinavir (SQV) in its hard gelatin formulation.

DESIGN

Forty-one post-therapy isolates and corresponding baseline samples were obtained from 37 patients in four different clinical trials after therapy with SQV for 16-147 weeks. Post-therapy isolates were selected on the basis of preliminary sequence or drug sensitivity data.

RESULTS

Fifteen out of 17 isolates without detectable Val-48 or Met-90 mutations retained sensitivity to SQV. (The remaining isolates showed only a marginal increase in median inhibitory concentration.) In addition, three out of 15 isolates with Met-90 retained sensitivity to all other protease inhibitors tested (indinavir, ritonavir, amprenavir, nelfinavir). Of the isolates showing reduced sensitivity to SQV, six out of 22 retained sensitivity to all other protease inhibitors, whereas only four out of 22 showed broad cross-resistance to all protease inhibitors tested. The reduction in sensitivity correlated closely with the presence of Val-48 or Met-90. Subsequent accessory substitutions were also linked to reduced sensitivity. However, significant linkage was observed only between mutations at residues 48 and 82 and between those at residues 82 and 74.

CONCLUSIONS

Recruitment of Val-48/Met-90 mutations was not found to be synonymous with cross-resistance. Indeed, the majority of isolates with these mutations retained sensitivity to at least one protease inhibitor (Val-48, 86%; Met-90, 77%). The recruitment of accessory mutations may occur only after the selection of key resistance mutations. Furthermore, Met-90 was found to be a poor marker of cross-resistance in SQV-treated patients.

Characterization of the Functional Insulin Binding Epitopes of the Full-length Insulin Receptor

Mutational analyses of the secreted recombinant insulin receptor extracellular domain have identified a ligand binding site composed of residues located in the L1 domain (amino acids 1-470) and at the C terminus of the alpha subunit (amino acids 705-715). To evaluate the physiological significance of this ligand binding site, we have transiently expressed cDNAs encoding full-length receptors with alanine mutations of the residues forming the functional epitopes of this binding site and determined their insulin binding properties. Insulin bound to wild-type receptors with complex kinetics, which were fitted to a two-component sequential model; the Kd of the high affinity component was 0.03 nM and that of the low affinity component was 0.4 nM. Mutations of Arg14, Phe64, Phe705, Glu706, Tyr708, Asn711, and Val715 inactivated the receptor. Alanine mutation of Asn15 resulted in a 20-fold decrease in affinity, whereas mutations of Asp12, Gln34, Leu36, Leu37, Leu87, Phe89, Tyr91, Lys121, Leu709, and Phe714 all resulted in 4-10-fold decreases. When the effects of the mutations were compared with those of the same mutations of the secreted recombinant receptor, significant differences were observed for Asn15, Leu37, Asp707, Leu709, Tyr708, Asn711, Phe714, and Val715, suggesting that the molecular basis for the interaction of each form of the receptor with insulin differs. We also examined the effects of alanine mutations of Asn15, Gln34, and Phe89 on insulin-induced receptor autophosphorylation. They had no effect on the maximal response to insulin but produced an increase in the EC50 commensurate with their effect on the affinity of the receptor for insulin.

In vitro Resistance to an Inhibitor of HIV Proteinase (Ro 31-8959) Relative to Inhibitors of Reverse Transcriptase (AZT and TIBO)

Serial passage of cell-free human immunodeficiency virus type 1 (HIV-1) strain GB8 on CEM cells was carried out in the presence of increasing concentrations of the HIV proteinase inhibitor Ro 31-8959 in parallel with representative reverse transcriptase (RT) inhibitors (AZT and the TIBO compound, R82150). In all instances, a significant increase in the concentration of compound required to produce a 90% reduction of syncytium formation (IC90) was found after seven to nine passages of virus. Reduced sensitivity to Ro 31 −8959 was confirmed by p24 ELISA. Virus passaged in the presence of RT inhibitors did not show a significant change in either the ability to grow in culture supplemented with step-wise increments of inhibitor concentration or the rate of growth in the presence of compound. In contrast, virus passaged in the presence of Ro 31 −8959 required, on average, more than 2.5-times the normal passage time and often did not replicate when increases in inhibitor concentration were applied during the initial passages.

The results show that reduced sensitivity to an inhibitor of HIV proteinase, Ro 31–8959, can be generated, but it would seem to arise less readily than that found with either of the RT inhibitors studied. While this study indicates the potential for a reduction in sensitivity to proteinase inhibitors, it does not necessarily reflect the ability of mutant virus either to be selected for or to be propagated in the clinic.

Supramolecular protein engineering: design of zinc-stapled insulin hexamers as a long acting depot

Bottom-up control of supramolecular protein assembly can provide a therapeutic nanobiotechnology. We demonstrate that the pharmacological properties of insulin can be enhanced by design of "zinc staples" between hexamers. Paired (i, i+4) His substitutions were introduced at an alpha-helical surface. The crystal structure contains both classical axial zinc ions and novel zinc ions at hexamer-hexamer interfaces. Although soluble at pH 4, the combined electrostatic effects of the substitutions and bridging zinc ions cause isoelectric precipitation at neutral pH. Following subcutaneous injection in a diabetic rat, the analog effected glycemic control with a time course similar to that of long acting formulation Lantus. Relative to Lantus, however, the analog discriminates at least 30-fold more stringently between the insulin receptor and mitogenic insulin-like growth factor receptor. Because aberrant mitogenic signaling may be associated with elevated cancer risk, such enhanced specificity may improve safety. Zinc stapling provides a general strategy to modify the pharmacokinetic and biological properties of a subcutaneous protein depot.

Mapping of the insulin-like growth factor II binding site of the Type I insulin-like growth factor receptor by alanine scanning mutagenesis

The Type I insulin-like growth factor receptor is a physiological receptor for insulin-like growth factor II (IGF-II). To characterize the molecular basis of the receptor's ligand binding properties, we have examined the effects of alanine mutations of residues in the ligand binding site of the receptor on its affinity for IGF-II. The functional epitope for IGF-II comprises residues in the N-terminal L1 domain and residues at the C-terminus of the alpha subunit. Cysteine rich domain residues do not appear to be critical for IGF-II binding.

Characterization of a second ligand binding site of the insulin receptor

Insulin binding to its receptor is characterized by high affinity, curvilinear Scatchard plots, and negative cooperativity. These properties may be the consequence of binding of insulin to two receptor binding sites. The N-terminal L1 domain and the C-terminus of the alpha subunit contain one binding site. To locate a second site, we examined the binding properties of chimeric receptors in which the L1 and L2 domains and the first Fibronectin Type III repeat of the insulin-like growth factor-I receptor were replaced by corresponding regions of the insulin receptor. Substitutions of the L2 domain and the first Fibronectin Type III repeat together with the L1 domain produced 80- and 300-fold increases in affinity for insulin. Fusion of these domains to human immunoglobulin Fc fragment produced a protein which bound insulin with a K(d) of 2.9 nM. These data strongly suggest that these domains contain an insulin binding site.

Aromatic anchor at an invariant hormone-receptor interface: function of insulin residue B24 with application to protein design

Crystallographic studies of insulin bound to fragments of the insulin receptor have recently defined the topography of the primary hormone-receptor interface. Here, we have investigated the role of Phe(B24), an invariant aromatic anchor at this interface and site of a human mutation causing diabetes mellitus. An extensive set of B24 substitutions has been constructed and tested for effects on receptor binding. Although aromaticity has long been considered a key requirement at this position, Met(B24) was found to confer essentially native affinity and bioactivity. Molecular modeling suggests that this linear side chain can serve as an alternative hydrophobic anchor at the hormone-receptor interface. These findings motivated further substitution of Phe(B24) by cyclohexanylalanine (Cha), which contains a nonplanar aliphatic ring. Contrary to expectations, [Cha(B24)]insulin likewise exhibited high activity. Furthermore, its resistance to fibrillation and the rapid rate of hexamer disassembly, properties of potential therapeutic advantage, were enhanced. The crystal structure of the Cha(B24) analog, determined as an R6 zinc-stabilized hexamer at a resolution of 1.5 Å, closely resembles that of wild-type insulin. The nonplanar aliphatic ring exhibits two chair conformations with partial occupancies, each recapitulating the role of Phe(B24) at the dimer interface. Together, these studies have defined structural requirements of an anchor residue within the B24-binding pocket of the insulin receptor; similar molecular principles are likely to pertain to insulin-related growth factors. Our results highlight in particular the utility of nonaromatic side chains as probes of the B24 pocket and suggest that the nonstandard Cha side chain may have therapeutic utility.

Antiviral Synergy between Inhibitors of HIV Proteinase and Reverse Transcriptase

Ro 31–8959, a potent and specific inhibitor of HIV proteinases, is shown to interact synergistically in combination with nucleoside analogue inhibitors of HIV reverse transcriptase (AZT, ddC, 2′-FddC). Ninety per cent inhibition endpoints (IC90), obtained from checkerboard titrations of compound mixtures on CEM-T4 cells infected with HIV-i strain GB8, have been further analysed. Compared with concentrations needed when inhibitors are used individually, reductions of between 2- and 30-fold were observed in combination, depending on the nucleoside analogue and the ratio of concentrations employed. The results suggest that combinations of AZT or ddC with Ro 31–8959 should be considered for development as candidate antiviral treatments of patients with HIV infection.

Appendicitis risk prediction models in children presenting with right iliac fossa pain (RIFT study): a prospective, multicentre validation study

BACKGROUND

Acute appendicitis is the most common surgical emergency in children. Differentiation of acute appendicitis from conditions that do not require operative management can be challenging in children. This study aimed to identify the optimum risk prediction model to stratify acute appendicitis risk in children.

METHODS

We did a rapid review to identify acute appendicitis risk prediction models. A prospective, multicentre cohort study was then done to evaluate performance of these models. Children (aged 5-15 years) presenting with acute right iliac fossa pain in the UK and Ireland were included. For each model, score cutoff thresholds were systematically varied to identify the best achievable specificity while maintaining a failure rate (ie, proportion of patients identified as low risk who had acute appendicitis) less than 5%. The normal appendicectomy rate was the proportion of resected appendixes found to be normal on histopathological examination.

FINDINGS

15 risk prediction models were identified that could be assessed. The cohort study enrolled 1827 children from 139 centres, of whom 630 (34·5%) underwent appendicectomy. The normal appendicectomy rate was 15·9% (100 of 630 patients). The Shera score was the best performing model, with an area under the curve of 0·84 (95% CI 0·82-0·86). Applying score cutoffs of 3 points or lower for children aged 5-10 years and girls aged 11-15 years, and 2 points or lower for boys aged 11-15 years, the failure rate was 3·3% (95% CI 2·0-5·2; 18 of 539 patients), specificity was 44·3% (95% CI 41·4-47·2; 521 of 1176), and positive predictive value was 41·4% (38·5-44·4; 463 of 1118). Positive predictive value for the Shera score with a cutoff of 6 points or lower (72·6%, 67·4-77·4) was similar to that of ultrasound scan (75·0%, 65·3-83·1).

INTERPRETATION

The Shera score has the potential to identify a large group of children at low risk of acute appendicitis who could be considered for early discharge. Risk scoring does not identify children who should proceed directly to surgery. Medium-risk and high-risk children should undergo routine preoperative ultrasound imaging by operators trained to assess for acute appendicitis, and MRI or low-dose CT if uncertainty remains.

FUNDING

None.

In vitro anti-HIV and Cytotoxicological Evaluation of the Triple Combination: AZT and ddC with HIV Proteinase Inhibitor Saquinavir (Ro 31-8959)

A combination of three anti-HIV compounds (AZT, ddC and saquinavir) has been studied in vitro. In confirmation and extension of previous studies, a greater than additive effect was found against both HIV-1GB8 and HIV-1N1T, when any two compounds were combined. Synergy of action was also found against both virus strains when all three compounds were employed together. Cytotoxicological studies indicated that a high therapeutic index could be maintained for this treatment. The potential benefits of improved anti-HIV surveillance, reduced risk of the development of resistance to the treatment and reduced requirement for drugs in quantities that produce toxic side-effects support the extension of clinical trials of saquinavir to investigate this combination.

Rescue of ligand binding of a mutant IGF-I receptor by complementation

The IGF-I receptor binds IGF-I with complex kinetics characterized by a curvilinear Scatchard plot, suggesting receptor heterogeneity and apparent negative cooperativity. To explore the molecular mechanisms underlying these properties, we have characterized the binding of a hybrid receptor formed from a wild-type receptor monomer and a mutant receptor monomer devoid of binding activity. Receptor hybrids were generated by transient co-transfection of cDNAs encoding wild-type and mutant receptors with unique epitope tags. Hybrid receptors were purified from transfected cells by sequential immuno-affinity chromatography and their ligand-binding properties were determined. Complementation produced a hybrid with near wild-type affinity. Dissociation studies demonstrated that the hybrid did not exhibit negative cooperativity.

Design of an insulin analog with enhanced receptor binding selectivity: rationale, structure, and therapeutic implications

Insulin binds with high affinity to the insulin receptor (IR) and with low affinity to the type 1 insulin-like growth factor (IGF) receptor (IGFR). Such cross-binding, which reflects homologies within the insulin-IGF signaling system, is of clinical interest in relation to the association between hyperinsulinemia and colorectal cancer. Here, we employ nonstandard mutagenesis to design an insulin analog with enhanced affinity for the IR but reduced affinity for the IGFR. Unnatural amino acids were introduced by chemical synthesis at the N- and C-capping positions of a recognition alpha-helix (residues A1 and A8). These sites adjoin the hormone-receptor interface as indicated by photocross-linking studies. Specificity is enhanced more than 3-fold on the following: (i) substitution of Gly(A1) by D-Ala or D-Leu, and (ii) substitution of Thr(A8) by diaminobutyric acid (Dab). The crystal structure of [D-Ala(A1),Dab(A8)]insulin, as determined within a T(6) zinc hexamer to a resolution of 1.35 A, is essentially identical to that of human insulin. The nonstandard side chains project into solvent at the edge of a conserved receptor-binding surface shared by insulin and IGF-I. Our results demonstrate that modifications at this edge discriminate between IR and IGFR. Because hyperinsulinemia is typically characterized by a 3-fold increase in integrated postprandial insulin concentrations, we envisage that such insulin analogs may facilitate studies of the initiation and progression of cancer in animal models. Future development of clinical analogs lacking significant IGFR cross-binding may enhance the safety of insulin replacement therapy in patients with type 2 diabetes mellitus at increased risk of colorectal cancer.

Weak transcriptional activation is sufficient for transformation by v-Myb

The v-myb oncogene causes monoblastic leukemia in chickens and transforms avian myelomonocytic cells in vitro, v-Myb is a short-lived nuclear protein which binds to DNA in a sequence-specific manner and can activate gene expression in transient DNA transfections. Analysis of a series of v-Myb mutants has shown that the ability to activate transcription appears to be required for leukemic transformation. We have systematically investigated transcriptional activation by v-Myb and have made several new observations: (i) v-Myb is a very weak activator when compared to GAL4; (ii) very weak transcriptional activation by v-Myb is sufficient for transformation, whereas very strong transcriptional activation by a v-Myb-VP16 fusion protein is not; and (iii) v-Myb can activate transcription by two genetically distinct mechanisms, only one of which requires the presence of Myb-binding sites.

The measurement of pupil cycling time

PURPOSE

To assess the influence of pupil size on pupil cycling time (PCT), a measure which may be elongated in cases of neurological disease.

METHOD

Clinically, pupil "cycling" is produced by focusing a slit-lamp beam on the pupil margin. A rhythmic contraction and dilation of the pupil is produced, as changes in pupil size alternately prevent and allow the light beam to reach the retina. In this study, however, the light beam was controlled electronically so that cycling could be produced around different pupil sizes. Measurements of the variation of PCT with pupil size were taken from 22 young normal subjects.

RESULTS

PCT was seen to depend upon pupil size, increasing monotonically but non-linearly as size increased. The wave-form of pupil cycling is typically sawtooth, contraction being much faster than dilation. There was considerable variation amongst subjects in the range of pupil sizes where pupil cycling could be elicited.

CONCLUSIONS

The results point to the need for a standardised procedure for the measurement of cycling time, because differences in clinical conditions will themselves influence pupil size, as will other external variables such as ambient light level. The results also bring into question neurological explanations for increased PCT in those diseases where pupil size is affected, because normal subjects have PCTs well beyond the accepted limits of normality when their pupils are enlarged.

A comparison of enprostil and ranitidine in treatment of duodenal ulcer

Enprostil is a new synthetic prostaglandin E2 with antisecretory and mucosal-protective effects. We compared it with ranitidine in the healing of duodenal ulcer and also examined the subsequent relapse rate. Three hundred thirteen patients were recruited in 15 centers in Europe, of whom 158 were treated with enprostil (E) 35 micrograms twice daily and 155 with ranitidine (R) 150 mg twice daily for up to 6 weeks, using a double-blind method. Patients in both groups were of comparable demography. Healing was significantly quicker with ranitidine. Of patients randomized to treatment, healing (intention-to-treat analysis) at 4 weeks was E 47% and R 69%, and at 6 weeks it was E 66% and R 88%. In patients who met all protocol criteria and completed treatment, healing at 4 weeks was E 58% and R 80%, and at 6 weeks it was E 81% and R 92%. Early relief of pain, both during the day and at night, was significantly quicker with ranitidine. Nausea, diarrhea, vomiting, and abdominal pain occurred more often with enprostil. There were no clinically important abnormalities in hematology or biochemistry. Relapse rates were similar. In conclusion, enprostil is not as effective as ranitidine in healing duodenal ulcers.

Cluster of influenza A cases in vaccinated population of adults in Virology Laboratory in Glasgow in December 2012

BACKGROUND AND AIMS

The majority of influenza infections during the 2012/2013 influenza season in Scotland have been due to influenza A H3N2. We report an outbreak of influenza A H3N2 in a vaccinated population of adults in the Regional Virology Laboratory in Glasgow. This investigation was carried out to confirm the epidemiological link between cases.

METHODS AND RESULTS

Staff with clinical symptoms of influenza-like illness were included. Samples were tested by real-time polymerase chain reaction and sequencing. Staff were interviewed to obtain information regarding symptom onset and vaccination status. Eight confirmed cases and six clinically diagnosed cases were reported, which all occurred within 4 days of a lunchtime Christmas quiz. The eight samples subtyped as H3 virus. The haemagglutinin gene in the confirmed cases was sequenced and shown to be identical. Most of the attendees had been immunised against influenza with the same vaccine batch at least 6 weeks earlier.

CONCLUSION

This outbreak appears to have been an isolated incident, which arose due to a social event that provided the ideal conditions for transmission of a respiratory disease. It may have been compounded by low-vaccine effectiveness this season. Sequence data supported the epidemiological link.

Do Patients with Critical Limb Ischaemia Undergo Multiple Amputations after Infrainguinal Bypass Surgery?

BACKGROUND

it has been suggested that an aggressive policy of bypass for limb salvage in critical ischaemia may result in patients subsequently undergoing multiple amputations. The aim of this study was to test this suggestion in the context of a dedicated Vascular Surgical Unit in a U.K. teaching hospital.

METHODS

three hundred and sixty-eight patients undergoing lower limb bypass operations for critical limb ischaemia between April 1991 and March 1999 were studied retrospectively. Their median age was 69 years (IQR 64--75) and 243 (66%) were men.

RESULTS

seventy-five operations were followed by one or more amputation (20%). Only 2% were multiple amputations. Age and sex had no effect on amputation rates, but emergency bypass operations led to a higher rate of amputation in those with critical limb ischaemia.

CONCLUSION

patients with critical limb ischaemia who undergo lower limb bypass surgery rarely have subsequent multiple amputation.

Ovarian intraepithelial neoplasia and ovarian cancer

Ovarian cancer accounts for only 4% of cancers in women, but it is the leading cause of death from gynecologic malignancies in the United States. In the general population, a woman's lifetime risk of ovarian cancer is 1.4% but this risk can increase substantially in women with a strong family history of the disease. The high mortality rate from ovarian cancer is due primarily to the difficulty in detecting the disease in early stages; the disease tends to be asymptomatic until it is well advanced. The primary care physician needs to be alert to the possibility of an ovarian malignancy in all women with an intact ovary or ovaries who present with abdominal or pelvic complaints. There are no current recommendations for routine screening for ovarian cancer in the general population. Even in high-risk women, there are currently no convincing data to support extensive screening, although a number of studies looking at this issue are under way. Despite this lack of conclusive evidence, a consensus panel on ovarian cancer convened by the NIH recently issued guidelines for screening high-risk women. They recommend annual rectovaginal pelvic examination, testing of CA 125 level, and transvaginal ultrasonography. Color flow Doppler analysis of the ovarian vessels is also being studied as a possible screening modality. BRCA1 gene testing may soon play a role in women with a strong family history of the disease. Given its high mortality rate, primary prevention strategies for ovarian cancer should be used whenever possible. Oral contraceptive use appears to reduce the risk of ovarian cancer. Prophylactic oophorectomy may be suggested for women at particularly high risk of the disease. Here, too, the primary care physician can play an important role in helping a patient understand the risks and benefits of these options.

A highly conserved cysteine in the v-Myb DNA-binding domain is essential for transformation and transcriptional trans-activation

The v-Myb protein is nuclear, binds to DNA in a sequence-specific fashion, regulates the transcription of various reporter gene and transforms myelomonocytic cells. Cysteine is one of the most conserved residues during protein evolution and has been implicated in DNA binding, protein-protein interaction and redox regulation of various proteins. Therefore, we have now individually substituted each of the seven cysteines of v-Myb with a serine. All seven mutant proteins bound to DNA when they were expressed in E. coli. However, mutant C65S neither trans-activated transcription in vivo nor transformed myeloid cells, although it was transported into the nucleus. This cysteine is conserved in the Myb-related proteins of animals, plants, yeast and the cellular slime mold Dictyostelium discoideum. The C65S mutation and a nearby codon insertion mutation also abolished trans-activation by fusion proteins containing the v-Myb DNA-binding domain and the strong constitutive activation domain of herpes simplex virus (HSV) VP16. Because this domain of VP16 appears to activate transcription whenever it is bound upstream of an appropriate promoter, these results imply that C65 may be required for high-affinity DNA binding in vivo. In support of this hypothesis, we have also shown that, in contrast to wild-type v-Myb, mutant C65S is unable to block transcription from a reporter gene in which Myb binding sites overlap the initiation site.

P425Single procedure pace and ablate. evaluation of efficacy and safety comparing three different vascular routes

Funding Acknowledgements

No financial support for this study

Introduction

Permanent pacemaker implantation combined with AVN ablation is a well-established treatment for rate control in patients with atrial fibrillation refractory to medical therapy. At the same sitting, this has been achieved in a single procedure via the subclavian vein (SCV) for both pacemaker implantation and AVN ablation, by pacemaker implantation via the SCV with femoral access for AVN ablation or by using the femoral vein (FV) for leadless pacemaker implantation and AVN ablation with a coaxial single-puncture technique.

We evaluated all combined procedures (pacemaker implantation and AVN ablation at the same sitting) performed in a single centre over 9 years comparing clinical outcomes, complications rates and procedure times.

Statistical methods: 

Continuous variables are described as mean ± standard deviation (SD), and statistical differences between groups were evaluated by one-way ANOVA. A X2 test was used for categorical variables, with Fisher’s exact test for any field where the expected frequency was ≤5 with pvalue < 0.05 considered as statistically significant. The statistical analysis was performed using SPSS software package. 

Results

 

141 patients underwent AVN ablation at our institution as part of a ‘pace and ablate’ single procedure strategy between 14/2/11 and 10/6/19. 61 patients had a combined procedure via the SCV, 66 patients had pacemaker implanted via the SCV and AVN ablation via the FV in the same sitting and 14 patients had leadless pacemaker (Micra) implantation and AVN ablation via the FV. Our findings suggest that the fluoroscopy time as well as the total catheter laboratory time were much less in the Micra group compared to the other groups. In the conventional pacemaker groups (group 1 and 2), the fluoroscopy time was not statistically different between the two. There was a trend towards acute procedural failure, switching to another access as well as a higher complication rate in the SCV group, however this has not reached statistical significance. 

Conclusion

 

Our early data suggests that pacemaker implantation and AVN ablation with a coaxial single femoral vein puncture technique is safe and takes less fluoroscopy time as well as total laboratory time.

Procedural outcomes All (n = 141) Group 1: SCV (n = 61) Group 2: FV (n = 66) Group 3: Micra (n = 14) P-value Total cath-lab time (mins) 113.1 ± 40.4 106.2 ± 37.2 125.7 ± 42.5 86.9 ± 23.1 0.001 Total fluoroscopy time (mins) 8.8 ± 7.6 11 ± 7.8 7.7 ± 7.6 4.5 ± 3 0.0001 Acute procedural failure, n (%) 9 (6.4) 7 (11.5) 2 (3) 0 (0) **0.6 Complications, n (%) 7 (4.9) 5 (8.2) 2 (3) 0 (0) **0.62 **Fisher"s exact test applied to analysis of Micra VS Other methods