Fluoroless cavotricuspid isthmus radiofrequency ablation of typical atrial flutter achieves success with zero radiation and shorter procedural duration

Funding Acknowledgements

Type of funding sources: None.

Background

Cavotricuspid isthmus (CTI) ablation in patients with typical atrial flutter (AFL) has improved in the past years, especially by the use of threedimensional (3D) electroanatomic mapping systems. These mapping tools contributed to reduce radiation exposure, but most ablation procedures still require varying amounts of fluoroscopy.

Purpose

We aim to examine whether fluoroless CTI ablation is effective and safe in reducing AFL recurrence, compared with CTI ablation using fluoroscopy and a 3D mapping system.

Methods

A retrospective analysis of CTI ablation procedures performed at a tertiary center between December 2008 and December 2020 was conducted. Cases were divided in two groups: fluoroless and fluoroscopic, according to the use of radiation. Procedural duration, fluoroscopy time (FT), use of 3D mapping system, complications and recurrence rate at one year were analyzed.

Results

A total of 324 CTI ablations performed on patients with documented typical AFL were included. Mean age was 62.3±14.0, with 78.1% male patients. Fluoroless ablations were performed based on a 3D mapping system, and all fluoroscopic procedures also used 3D electroanatomic mapping. The FT was zero in the fluoroless group - 31 cases (9.6%), and 7.0±4.4 minutes in the fluoroscopic group - 291 cases (90.4%) (p<0.001). There was no statistically significant difference between the two groups, regarding AFL recurrence at one year (21.7% in the fluoroless group versus 13% in the fluoroscopic group; odds ratio [OD] 0.54; 95% confidence interval [CI] 0.18-1.62; p=0.27). Total procedure duration was significantly shorter in the fluoroless group (1h07m versus 1h40m; t-test 4.261, p<0.001, CI 0h16m-0h50m). There were no acute complications for both groups.

Conclusion

Fluoroless CTI ablation avoids radiation exposure to the patient and operator and can be performed in patients with typical AFL, without compromising duration, safety or efficacy of the procedure.

Combined pulmonary vein isolation and cavotricuspid isthmus ablation shows no benefit in recurrence of atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

Pulmonary vein isolation (PVI) is the mainstay of catheter ablation (CA) for atrial fibrillation (AF). Strategies have been proposed to improve the success rate of CA, such as prophylactic cavotricuspid isthmus (CTI) ablation. Despite some studies providing no, or limited, incremental benefit of CTI ablation in patients with AF, it is still frequently performed worldwide.

Purpose

The aim of this study is to examine whether CTI ablation, combined with PVI, is associated with improvement in recurrence of AF, compared with PVI alone in AF patients with or without atrial flutter (AFL).

Methods

We conducted a retrospective analysis of CA for AF performed at a tertiary center between September 2004 and December 2020. The procedures were divided in two groups: "PVI alone" and "PVI plus CTI ablation". Demographic, clinical, and procedure related data was retrieved. Atrial fibrillation recurrence rate at one year was analyzed for both groups and compared using logistic regression.

Results

A total of 453 procedures were analyzed: PVI alone (n=378; 83.4%) and PVI with CTI ablation (n=75; 16.6%). In the PVI alone group, 12.9% of the patients had concomitant typical AFL and in the PVI plus CTI ablation, 45.8% had typical AFL. Mean age was 57.3±12.1 years, with 63.6% male patients. At one year, AF recurrence rate was higher in the combined PVI with CTI ablation group (30.4%; n=21), compared with the PVI alone group (28.4%; n=97), with no statistical difference between the two groups (Odds Ratio [OD] 1.10; 95% confidence interval [CI] 0.62-1.94; p=0.73). In the subgroup analysis, there was no difference in recurrence between patients with AF without AFL (OR: 1.9; 95% CI: 0.39-9.36; p=0.43), and in patients with AF with concomitant AFL (OR: 10.0; 95% CI: 0.9-110.3; p=0.06).

Conclusion

In AF patients, irrespective of the presence of typical AFL, additional CTI ablation, compared with PVI alone, was not associated with improvement in recurrence of AF.

Long-term impact of activation circuit-based ventricular tachycardia ablation on ventricular arrhythmia burden

Funding Acknowledgements

Type of funding sources: None.

Background

Ventricular arrhythmias (VA) are a major cause of morbidity and mortality in heart failure patients. Ventricular tachycardia (VT) ablation is an established treatment for the reduction of recurrent implantable cardioverter-defibrillator (ICD) therapies in this population. In patients with substrate-related VT, mapping of the entire tachycardia circuit, when feasible, may allow for more accurate targeting of the clinical VT.

Purpose

To assess the long-term impact of catheter ablation based on activation mapping of substrate-related VT on VA burden.

Methods

Consecutive patients submitted to VT ablation between January 2013 and October 2021 were included. A comprehensive review of clinical records and device monitoring was performed to assess VA burden, defined as all ICD therapies and clinically documented VTs, before and after ablation. The primary outcome was reduction in the overall burden of VA after ablation. The impact of ablation on VA burden was assessed by fixed-effects Poisson regression; comparison at fixed time intervals was performed with a paired-sample Wilcoxon signed-rank test (STATA 12, JASP).

Results

A total of 134 VT ablation procedures were performed during the study period. Of these, there were 21 procedures where complete mapping of the VT activation circuit was achieved, corresponding to 18 patients. Mean age was 56.7 years, 88% male sex, mean left ventricular ejection fraction 39 ± 13%, BNP 540 ± 627 pg/mL. Etiology was ischemic in 44%, non-ischemic dilated cardiomyopathy in 39%, arrhythmogenic right ventricular dysplasia in 11% and hypertrophic cardiomyopathy in 6%. Mechanical support was in situ in 3 patients (two with temporary VA ECMO and one with LVAD as destination therapy); all but one patient had an ICD. Procedural duration was 209 ± 61 minutes. One patient developed complete AV block; no other peri-procedural complications were observed. During follow-up two patients died due to heart failure, one patient died from refractory cardiogenic shock with refractory incessant VT and one patient underwent orthotopic heart transplant. The mean follow-up time after ablation was 2.2 ± 1.9 years. A significant reduction in VA burden was observed (Figure 1) at 3 months (92.5% reduction, p=0.002) and 6 months after ablation (83.3% reduction, p=0.041). After fixed-effects Poisson regression, there was an estimated long-term reduction of 75% (CI 12-93%, p=0.031) of VA burden after VT circuit ablation.

Conclusion

Targeted circuit ablation is feasible in a subset of patients referred to VT ablation and leads to a significant sustained decrease in VA burden and device therapies.

Left atrial strain imaging and integrated backscatter: predictors of recurrence in patients with paroxysmal, persistent and long-standing persistent atrial fibrillation undergoing catheter ablation

Introduction

Left atrial (LA) strain imaging by echocardiography (TTE) is a promising tool in the evaluation of LA mechanical function. The aim of this study was to compare LA longitudinal strain and integrated backscatter (IBS) between paroxysmal (PAF), persistent (PersAF) and long-standing persistent AF (LsAF) and evaluate its association with AF recurrence post-index catheter ablation.

Methods

Analysis of consecutive patients (P) with symptomatic PAF and PersAF who underwent index AF catheter ablation and had performed TTE in our centre prior to AF ablation. LA reservoir phase longitudinal strain (LASr) and strain rate was assessed by 2D speckle-tracking at baseline. LA volume index (LAVi) and IBS were analysed. AF recurrence was documented with 12-lead ECG, 24h Holter monitoring, external loop recorder or pacemaker analysis in a 12-month follow-up period.

Results

78 P, 69% PAF vs 31% PersAF (46% LsAF), 65% male, 40% with structural heart disease, who underwent pulmonary vein isolation were studied (cryoballoon ablation in 53% and radiofrequency ablation in 47%). P with PersAF had a higher LAVi (46±15 mL/m2 vs 36±13 mL/m2 p=0.004), particularly LsAF P (55±17 mL/m2) and impaired LASr (9.2±4.9% vs 23.9±9.3%, p<0.001) (especially LsAF 5.61±3.08% vs 12.20±4.04%, p<0.001) as well as strain rate (0.58±0.25 s–1 vs 1.08±0.40 s–1, p<0.001). There was no significant difference between groups regarding IBS (116.6±36.1 dB vs 106.6±21.5 dB, p=0.134), including LsAF (128.8±21.5 dB vs 102.1±45.1 dB, p=0.071). During follow-up there was a 28% (22P) AF recurrence rate, higher in PersAF (50% vs PAF 20%, adjusted HR 3.44 [95% CI 1.44–7.69], p=0.005), particularly in LsAF (72% vs 31%, adjusted HR 3.24 [95% CI 0.98–10.9], p=0.048). P with AF recurrence showed significantly impaired baseline LASr both in PersAF (6.44±3.26% vs 11.93±4.79%, p=0.003), as well as PAF (13.86±5.65% vs 26.29±8.47%, p<0.001). LsAF P with AF recurrence demonstrated a considerably impaired LASr (4.99±2.93% vs 9.34±1.40%, p=0.006) vs PersAF. Multivariate analysis showed that impaired baseline LASr was an independent predictor of AF recurrence both in PersAF (adjusted HR 0.82 [95% CI 0.68–0.98], p=0.028) and PAF (adjusted HR 0.78 [95% CI 0.68–0.88], p<0.001). Kaplan-Meier analysis (Fig. 1) showed that both PAF and PersAF P with baseline LASr below the 18% cut-off had a significantly higher rate of AF recurrence, with earlier recurrence in PersAF. PAF P with AF recurrence had a higher baseline IBS (109.3±22.1 dB vs 94.7±14 dB, p=0.016) vs non-recurring P, in contrast to PersAF P (117.8±31.1 dB vs 115.4±42.1 dB, p=0.876), however IBS was not a significant predictor of AF recurrence in PAF (HR 1.03 [95% CI 0.99–1.07], p=0.060) or PersAF.

Conclusion

P with PersAF (and particularly LsAF) showed significantly impaired LASr, and PAF P with AF recurrence had superior baseline IBS vs non-recurring P. Reduced baseline LASr was an independent predictor of AF recurrence both in PAF and in PersAF P.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Left atrial strain imaging evaluation: a strong predictor of atrial fibrillation recurrence after single-procedure catheter ablation

Funding Acknowledgements

Type of funding sources: None.

Introduction

Identification of predictors of arrhythmia recurrence after catheter ablation of atrial fibrillation (AF) is a clinically relevant issue. Transthoracic echocardiography (TTE) is a readily accessible exam that can be useful in estimating left atrial (LA) mechanical function. The aim of this study was to evaluate LA structure and LA strain imaging at baseline and its association with AF recurrence after an index AF catheter ablation. Methods: Analysis of patients with symptomatic paroxysmal and persistent AF who underwent a single-procedure for AF ablation between 2015 and 2019 and had performed TTE in our centre prior to AF ablation. LA parameters were assessed by 2D speckle-tracking at baseline. LA diameter index (LAVi), LA ejection fraction, LA phasic strain: reservoir (LASr), conduit (LAScd) and contraction phases (LASct), as well as integrated backscatter (IBS) values were analysed. AF recurrence was documented with 12-lead ECG, 24h Holter monitoring, external loop recorder or pacemaker analysis during a 12-month follow-up period. Results: Of a total of 106 patients, 28 patients were excluded due to poor image quality. We studied 78 patients who underwent pulmonary veins isolation (PVI) (age 59 ± 14 years, 65% male, 40% with structural heart disease, 69% paroxysmal AF) with cryoballoon ablation in 53% and radiofrequency ablation in 47%. In a 12-month follow-up there was a 28% (22 patients) AF recurrence rate. Patients with AF recurrence had a baseline significantly superior LAVi (47 ± 17 mL/m2 vs. 36 ± 12 mL/m2, adjusted HR 1.04 [95% CI 1.01-1.06], p = 0.002) and lower estimated LA ejection fraction (25 ± 19.7% vs. 45.4 ± 21%, adjusted HR 0.96 [95% CI 0.94-0.98], p = 0.001). Multivariate analysis showed that baseline LA strain parameters were independent predictors of AF recurrence, as patients with AF recurrence showed impaired LASr (9.81 ± 5.79% vs 22.94 ± 9.98%, adjusted HR 0.81 [95% CI 0.73-0.89], p < 0.001) and LAScd (-6.74 ± 4.11% vs. -11.85 ± 7%, adjusted HR 1.11 [95% CI 1.03-1.19], p = 0.004). In patients in sinus rhythm during baseline TTE, LASct also correlated with AF recurrence, as patients with recurrence also showed impaired baseline LASct (-7.49 ± 3.65% vs -13.74 ± 5.4%, adjusted HR 1.39 [95% CI 1.11-1.75], p = 0.005). LASr <18% showed a sensitivity of 86% and specificity of 70% to predict AF recurrence. Kaplan-Meier curves (figure 1) showed that patients with LASr below the 18% cut-off had a significantly higher rate of AF recurrence. Baseline IBS did not reveal significant differences in AF recurrence (111.2 ± 23.9 dB vs. 105.9 ± 33.5 dB, HR 1.007 [0.993-1.002], p = 0.349). Conclusion: Baseline LA strain imaging parameters, including reservoir phase LA strain, were demonstrated to be independent predictors of AF recurrence after PVI. A LASr <18% showed good accuracy to predict AF recurrence. Abstract Figure. Kaplan-Meier curves - time to recurrence

Optimisation of a silicon/silicon dioxide substrate for a fluorescence DNA microarray

This paper presents a comprehensive theory and experimental characterisation of the modulation of the fluorescence intensity by the construction of optical interferences on oxidised silicon substrates used for DNA microarrays. The model predicts a 90-fold variation of the fluorescence signal depending on the oxide thickness. For a Cy3 dye, the signal is maximal for a 90 nm oxide thickness corresponding to a 7.5-fold enhancement with respect to a standard glass substrate. For experimental validation of the model, we have prepared Si/SiO2 substrates with different parallel steps of decreasing oxide thicknesses on the same sample using a buffered oxide etch (BOE) etching process after thermal oxidation. The SiO2 surface has been functionalized by a silane monolayer before in situ synthesis of L185 oligonucleotide probes. After hybridisation with complementary targets, the variations of the fluorescence intensity versus oxide thickness are in very good accordance with the theoretical model. The experimental comparison against a glass substrate shows a 10-fold enhancement of the detection sensitivity. Our results demonstrate that a Si/SiO2 substrate is an attractive alternative to standard glass slides for the realisation of fluorescence DNA microarrays whenever detection sensitivity is an important issue.

Programmed cell death via mitochondria: Different modes of dying

Programmed cell death (PCD) is a major component of normal development, preservation of tissue homeostasis, and elimination of damaged cells. Many studies have subdivided PCD into the three categories of apoptosis, autophagy, and necrosis based on criteria such as morphological alterations, initiating death signal, or the implication of caspases. However, these classifications fail to address the interplay between the three types of PCD. In this review, we will discuss the central role of the mitochondrion in the integration of the cell death pathways. Mitochondrial alterations such as the release of sequestered apoptogenic proteins, loss of transmembrane potential, production of reactive oxygen species (ROS), disruption of the electron transport chain, and decreases in ATP synthesis have been shown to be involved in, and possibly responsible for, the different manifestations of cell death. Thus, the mitochondria can be viewed as a central regulator of the decision between cellular survival and demise.

Preimplantation genetic diagnosis of spinocerebellar ataxia 3 by (CAG)n repeat detection

Spinocerebellar ataxia 3 (SCA3) is an autosomal dominant neurodegenerative disorder characterized by variable expression and a variable age of onset. SCA3/MJD (Machado-Joseph disease) is caused by an expansion of a (CAG)(n) repeat in the MJD1 gene on chromosome 14q32.1. A single cell PCR protocol has been developed for preimplantation genetic diagnosis (PGD) of SCA3 to select unaffected embryos on the basis of the CAG genotype. Single leukocytes and blastomeres served as a single cell amplification test system to determine the percentage of allelic drop-out (ADO) and PCR efficiency. Out of 105 tested heterozygous single leukocytes, 103 (98.1%) showed a positive amplification signal, while five cells (4.9%) showed ADO. Amplification in single blastomeres was obtained in 13 out of a total of 14, and ADO was observed in two out of the 13 single blastomeres. PGD of SCA3 was performed in a couple with paternal transmission of the SCA3 allele. Seven embryos were available for biopsy, all biopsied blastomeres showed amplification and no ADO occurred. One embryo was diagnosed as affected whereas six embryos were diagnosed as unaffected. Two unaffected embryos were transferred and resulted in a singleton pregnancy and the birth of a healthy girl.

Embryo development and chromosomal anomalies after ICSI: effect of the injection procedure

Intracytoplasmic sperm injection (ICSI) is a delicate procedure requiring considerable skills of the person performing it. Theoretically, the injection procedure could damage cytoplasmic structures in the oocyte, resulting in sublethal cellular injury and/or numerical chromosomal abnormalities that could lead to impaired embryonic development. In the present study, features of the injection procedure were evaluated in a total of 2924 oocytes from 305 cycles. Development to the blastocyst stage was found to be compromised in a group of surplus embryos originating from oocytes in which >6 pl of cytoplasm was aspirated into the injection pipette during the ICSI procedure. Characteristics of the injection procedure as well as blastocyst development of surplus embryos was shown to be significantly different between the four technicians performing the ICSI. Neither the volume of cytoplasm aspirated during the injection procedure, nor the position of the polar body (6 o'clock or 12 o'clock) influenced the mean incidence of disomic cells per blastocyst as revealed by fluorescence in-situ hybridization using probes specific for chromosomes X, Y and 18. In conclusion, certain technical aspects of the injection procedure can affect subsequent embryonic development to the blastocyst stage, but do not seem to influence the rate of chromosomal abnormalities that occur in human pre-implantation embryos.

Multiplex PCR of polymorphic markers flanking the CFTR gene; a general approach for preimplantation genetic diagnosis of cystic fibrosis

Cystic fibrosis (CF) is the first monogenic disorder for which single cell preimplantation genetic diagnosis (PGD) has been successfully applied. The spectrum of mutations in CF is extremely heterogeneous, and hence, the development of mutation-specific PGD protocols is impracticable. The current study reports the development and evaluation of a general multiplex marker polymerase chain reaction (PCR) protocol for PGD of CF. Four closely linked highly polymorphic (CA)(n) repeat markers D7S523, D7S486, D7S480 and D7S490, flanking the cystic fibrosis transmembrane regulator (CFTR) gene, were used. In 99% of the single cells tested (100 leukocytes and 50 blastomeres), multiplex PCR results were obtained and the overall allelic drop out (ADO) rate varied from 2 to 5%. After validation for the presence of ADO and additional alleles, 95% of the multiplex PCR results were accepted to construct the marker genotypes. Depending on the genotype of the couple, and taking into account the embryos lost for transfer due to validation criteria (5%), ADO (0-2%) and single recombination (1.1-3%), in general >90% of the embryos could be reliably genotyped by PGD using a single blastomere. The risk of misdiagnosis equals the chance of a double recombination between informative flanking markers and is <0.05%. Therefore, this polymorphic and multi-allelic marker system is a reliable and generally applicable alternative for mutation-directed PGD protocols. Furthermore, it provides a test for the origin of the detected genotype and also gives an indication of the chromosomal ploidy status of the blastomere tested.

Comparison of in-vitro development of embryos originating from either conventional in-vitro fertilization or intracytoplasmic sperm injection

In this retrospective study on 1628 consecutive cycles performed during a period of 4 years, development in vitro is compared of embryos obtained after either conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). At 39-42 h after insemination or injection, embryos obtained after ICSI were significantly (P < 0.01) further developed (mean cell number 3.48 +/- 0.03) as compared with those obtained after IVF (3.22 +/- 0.03), whereas after 63-66 h of in-vitro development this difference was no longer present (mean cell number 6.11 +/- 0.15 versus 6.09 +/- 0.13 respectively). Culture of surplus embryos obtained after IVF resulted in a significantly higher (P < 0.001) mean incidence of blastocyst formation per cycle as compared with the ICSI group (31.8 +/- 1.9 versus 23.0 +/- 1.4 respectively). Blastocysts from both groups consisted of comparable numbers of cells. Blastocyst formation was also significantly higher when embryos were cultured in groups (31.2 +/- 1.8) compared to single culture (23.1 +/- 1.5; P < 0.01), in human tubal fluid (HTF) medium (29.2 +/- 1.7) compared with IVF-50(TM) medium (24.2 +/- 1.6; P < 0.01), and when they were cultured under 5% O(2) (30.3 +/- 1.5) compared with 20% O(2) (21.7 +/- 1.7; P < 0.01). In all culture conditions used, the mean incidence of blastocyst formation per cycle showed comparable differences in favour of the IVF group as compared with the ICSI group.

Effect of oxygen concentration on human in-vitro fertilization and embryo culture

In this prospective randomized study on 1380 consecutive in-vitro fertilization (IVF) treatments, the results were compared of culture of human oocytes and embryos for the first 2 or 3 days of development in microdroplets of medium under oil using a gas phase containing either atmospheric (approximately 20%) or reduced (5%) O2 concentrations. No significant differences were found between the two groups cultured under either 5% or 20% O2 in rates of fertilization (60 versus 61%, respectively), embryo development at day 2 or 3, pregnancy (26.6 versus 25.4%, respectively), and implantation (13.4 versus 14.0%, respectively). Culture of surplus embryos under 5% O2 resulted in a significantly higher mean incidence of blastocyst formation per cycle as compared to the 20% O2 group (25.8 +/- 2.0 versus 20.4 +/- 1.9, respectively). The mean number of cells of embryos classified as blastocysts by microscopic observation of a blastocoel was significantly higher in the 5% O2 group as compared to the 20% O2 group, both in blastocysts fixed on day 5 (39.8 +/- 1.7 versus 31.9 +/- 1.9, respectively), as well as those fixed on day 6 (45.6 +/- 2.6 versus 33.7 +/- 3.4, respectively). This difference was due to the fact that significantly more blastocysts of the 20% O2 group had an abnormal low cell number of < 25 as compared to the 5% O2 group, both in blastocysts fixed on day 5 (39 versus 22%, respectively), as well as those fixed on day 6 (43 versus 22%, respectively). To conclude, although culture under 5% O2 leads to slightly improved preimplantation embryonic viability, this effect is either too marginal to result in higher pregnancy rates, or low O2 concentrations exert an effect during the later stages of preimplantation development only.

Effect of Ca2+/Mg2+-free medium on the biopsy procedure for preimplantation genetic diagnosis and further development of human embryos

In this study, the use of Ca2+/Mg2+-free medium for biopsy of human embryos at the 4- to 10-cell stage on the third day of development was evaluated. When compared with control medium containing normal concentrations of Ca2+ and Mg2+ ions, the use of Ca2+/Mg2+-free medium allows an easier removal of blastomeres as illustrated by a lower rate of cell lysis as well as by a shorter time needed to perform the procedure. Subsequent embryo development to the blastocyst stage is not affected by the choice of biopsy medium, not even when embryos are exposed to the medium for 45 min. The use of Ca2+/Mg2+-free medium thus allows for an easier biopsy procedure during pre-implantation genetic diagnosis, while it does not result in a loss of developmental potential of the embryo to the blastocyst stage.

Preimplantation genetic diagnosis of spinal muscular atrophy

After Duchenne muscular dystrophy, spinal muscular atrophy (SMA) is the most common severe neuromuscular disease in childhood. Since 1995, homozygous deletions in exon 7 of the survival motor neuron (SMN) gene have been described in >90-95% of SMA patients. However, the presence of a highly homologous SMN copy gene complicates the detection of exon 7 deletions. This paper describes the adjustment and evaluation of an established SMN exon 7 polymerase chain reaction (PCR) protocol at the single cell level, and the first preimplantation genetic diagnosis (PGD) of SMA with this PCR protocol. To determine PCR efficiency and allelic loss, 200 leukocytes of normal individuals, SMA carriers and patients, and 25 blastomeres were tested. The PCR efficiency of the SMN exon 7 and the adjacent copy gene sequence, tested in the leukocytes, were 90% and 91% respectively. No allelic loss was detected. One out of 25 blastomeres tested revealed a negative PCR signal for the SMN exon 7 sequence. All 25 showed the copy gene sequence. PGD of SMA was offered to a couple with an affected child homozygous for the SMN exon 7 deletion. After intracytoplasmic sperm injection, four and five embryos could be genotyped for the SMN exon 7 in two cycles respectively. After embryo transfer in the second PGD cycle an ongoing gemelli pregnancy was achieved. This study demonstrates that PGD for SMA is feasible when a previous child is homozygous for the SMN exon 7 deletion.

Modulation of embryonic Na(+)-K(+)-ATPase activity and mouse preimplantation development in vitro in media containing high concentrations of potassium

The effect of various potassium concentrations (ranging from 1.4 mM to 30 mM K+) in modified Tyrode's medium on the culture of mouse zygotes obtained after in vitro fertilization to the blastocyst stage was examined. A clear dose-dependent negative effect of increasing K+ concentrations on the preimplantation embryonic development in vitro was found. We have previously shown that significantly more two-cell embryos reach the blastocyst stage when cultured during the second day postinsemination in medium supplemented with taurine. Because taurine, an amino acid that abounds in the reproductive tract, has been reported to inhibit the enzyme Na(+)-K(+)-adenosine triphosphatase (Na(+)-K(+)-ATPase), we used two other conditions known to inhibit the Na(+)-K(+)-ATPase to study their effect on mouse embryo development. Culturing embryos during a short period (the second day postinsemination) in low extracellular K+ concentrations (1.4 mM) or in medium supplemented with ouabain (50 microM) showed positive effects similar to those of culturing in medium with taurine (10 mM). This beneficial effect of ouabain was found in various K+ concentrations tested, including the high concentrations present in the oviduct. Although the effects of low K+ and taurine can possibly be ascribed to their other cellular effects, the effect of ouabain shows that inhibition of the Na(+)-K(+)-ATPase during the two-cell stage in the mouse is beneficial for further embryonic development to the blastocyst stage.

Temporal effects of ouabain on in-vitro development of mouse zygotes

Ouabain is a specific inhibitor of Na(+)-K(+)-ATPase, an enzyme which controls the intracellular Na+ and K+ levels. In this study, in-vitro fertilized zygotes from a hybrid mouse strain were used to examine the temporal effects of 50 microM ouabain on embryonic development in vitro during the preimplantation period. A higher incidence of blastocyst formation at the end of the culture period was found when embryos were cultured in the presence of ouabain from 22 to 46 h post-insemination, or any other period that included this time period. When zygotes from randomly bred mice were used, inhibition of Na(+)-K(+)-ATPase with ouabain clearly promoted development through the 2-cell block in vitro. As Na(+)-K(+)-ATPase is the most important regulator of intracellular electrolyte concentrations in mammalian cells, these results suggest that an ionic imbalance exists in embryos cultured in conventional media which can be positively influenced by inhibiting this enzyme.

Effect of the number of inseminated spermatozoa on subsequent human and mouse embryonic development in vitro

It has been shown, in both human and mouse in-vitro fertilization (IVF), that an excess number of spermatozoa in the insemination medium leads to reduced fertilization rates. In this study, we evaluated human embryonic development after dividing the oocytes of each of 62 IVF attempts into two groups on the basis of insemination with two widely used concentrations (50,000 and 100,000 spermatozoa/ml). The embryonic growth was retarded in the group inseminated with 100,000 spermatozoa/ml: significantly fewer fast developing embryos (4-cell and 5- to 8-cell stages) were found (53.4% in the 100,000/ml group and 65.5% in the 50,000 group; P less than 0.05). In two experimental series, mouse embryonic development was evaluated in the presence of 0, 50,000, 100,000 and 500,000 spermatozoa per ml. In the first series, the spermatozoa were present during 5-20 h after insemination, while in the second series, the spermatozoa were present during the whole culture period of 120 h. The development of mouse embryos was impaired when 500,000/ml spermatozoa were present during the whole culture period. In contrast with human IVF results, the presence of up to 500,000 spermatozoa during the first 20 h after insemination did not have any significant detrimental effect on blastocyst formation in the mouse.

Positive effect of taurine on preimplantation development of mouse embryos in vitro

The effect of various taurine concentrations in modified Tyrode's medium on in vitro fertilization of mouse oocytes was examined. No significant difference in fertilization rate was found at concentrations of 0, 0.1, 1, 5, 10 and 20 mM taurine. In a second series of experiments, the effect of taurine on preimplantation embryonic development after fertilization in vitro was studied. At concentrations of 1, 5, 10 and 20 mM taurine, significantly more two-cell embryos reached the blastocyst stage compared with medium without taurine. Culture in the presence of 5 mM or 10 mM taurine resulted in blastocysts with the highest mean number of cells. The positive effect of taurine on embryonic development was found to be more pronounced both in a second medium (human tubal fluid medium) which has a higher potassium concentration than Tyrode's medium, and in a modified Tyrode's medium with an increased potassium concentration. In addition to these in vitro studies, it is reported that taurine comprised about 59% of the total free amino acid content in mouse oviduct flushings, compared with 17% in mouse serum.

Temporal effects of taurine on mouse preimplantation development in vitro

Previously it has been shown that significantly more 2-cell mouse embryos reach the blastocyst stage when cultured in medium supplemented with taurine. In this study, in-vitro fertilized zygotes from a hybrid mouse strain were used to examine the temporal effects of 10 mM taurine on embryonic development in vitro during the preimplantation period. Taurine exerted its beneficial effect exclusively during the first 2 days post-insemination. The effect of taurine on blastocyst formation appeared to be restricted mostly to the period 20-48 h after fertilization, during which time mouse embryos are at the two-cell stage. Although more blastocysts were found when embryos were cultured in taurine-containing medium from 5 to 20 h post-insemination, this difference was not significant compared to the number of blastocysts when embryos were cultured without taurine. Taurine did not appear to affect the two-cell block of mouse embryos from random-bred strains.

Triploidy after in vitro fertilization: cytogenetic analysis of human zygotes and embryos

Tripronuclear zygotes obtained from a clinical IVF program were studied cytogenetically. Successful analysis was possible of 42 specimens at the zygote stage and 21 embryos after the first or second cleavage division. In the majority of zygotes (88%) the expected triploidy was confirmed, whereas only 14% of embryos had solely triploid cells. Therefore it is concluded that after tripolar cleavage division, many different types of mosaicism may originate from irregular chromosome distributions. Since the findings in individual blastomeres in embryos resulting from multipronuclear zygotes do not reflect the genetic content of the whole embryo, these embryos are less suitable in a model system for preimplantion diagnosis. The distribution of the sex chromosomal types (XXX, XXY, and XYY) confirmed theoretical expectations. Since in abortion material or in liveborn triploidy cases, the XYY karyotype is hardly ever observed, this indicates that most likely the 69,XYY karyotype has a very high embryonic mortality.

Immaturity and aneuploidy in human oocytes after different stimulation protocols

OBJECTIVE

To study immaturity and aneuploidy in human oocytes after two different stimulation protocols.

DESIGN

Retrospective.

SETTING

Outpatient IVF clinic/laboratory.

PATIENTS

One hundred forty-three patients of whom 65 were stimulated with clomiphene citrate (CC)/human menopausal gonadotropin (hMG) and 78 were stimulated with gonadotropin-releasing hormone agonist (GnRH-a)/hMG. Only patients with at least one oocyte unfertilized were included in this study.

RESULTS

Stimulation with GnRH-a/hMG, as compared with CC/hMG stimulation, resulted in larger numbers of oocytes (P less than 0.00001), a higher fertilization rate (P less than 0.02), and oocyte retrieval at a later average cycle day (P less than 0.000005). Cytogenetic findings of immaturity were observed in 33.9% of unfertilized oocytes after CC/hMG stimulation, compared with only 17.8% after GnRH-a/hMG stimulation (P less than 0.0005). Aneuploidy findings were the same for both groups.

CONCLUSION

In GnRH-a/hMG stimulation, oocytes approach the normal day of ovulation more closely. This may allow for better oocyte maturation and higher fertilization and pregnancy rates.

Evaluation of human sperm morphology using strict criteria after Diff-Quik staining: correlation of morphology with fertilization in vitro

New, very strict criteria were used after Diff-Quik staining for evaluating sperm morphology. The results of morphology scoring were correlated with the fertilization rate in vitro. Semen samples from 64 men participating in an in-vitro fertilization programme were used for this study. All men had to have a sperm concentration of greater than or equal to 20 million/ml and a progressive motility of greater than 30%. The morphology evaluation using strict criteria was performed on the same aliquot of semen as that used for in-vitro insemination. If strict criteria showed that normal morphology was less than or equal to 4%, the fertilization rate per oocyte was 23%. If normal morphology was greater than or equal to 11%, 77% fertilization occurred. For proportions of normal morphology between 4 and 11%, the fertilization rate per oocyte was 59% (P less than 0.000001). Among all these morphology groups, classical semen parameters, such as the mean volume, the mean concentration and the mean motility, did not differ significantly, except for the morphology evaluation using WHO criteria. The correlation with fertilization was better for morphology evaluation using strict criteria than for WHO. In conclusion, the method of evaluating sperm morphology based on very strict criteria allows a more accurate prediction of the chance of fertilization in vitro. Further studies should be done to establish the most appropriate cut-off points for severely impaired, intermediate and high fertilization rates.

The effects of endotoxins on gametes and preimplantation embryos cultured in vitro

Culture media used for human in-vitro fertilization (IVF) can be contaminated with bacterial endotoxins. All five tested types of commercially available albumin, sometimes used as a protein supplement to IVF media, were shown to contain endotoxins in varying concentrations. Endotoxins are suspected to cause embryo fragmentation and low pregnancy rates in human IVF. However, human sperm viability and the IVF of mouse oocytes and subsequent culture of the zygotes were shown to be unaffected by relatively high endotoxin concentrations. Therefore these techniques cannot be used as quality control assays to detect endotoxins in the IVF culture media.

Human in vitro fertilization using spermatozoa capacitated in hyperosmotic media

In two separate prospective randomized series of 38 and 16 attempts of human in vitro fertilization (IVF), respectively, the fertilizing abilities of human spermatozoa capacitated in hyperosmotic media and in normosmotic medium were compared. Oocytes from each IVF attempt were divided into two equal groups and inseminated with spermatozoa incubated for 2 h in medium with an osmolality of 285 mosm/kg or in hyperosmotic medium of 315 (first experiment) or 345 mosm/kg (second experiment). The fertilizing capacity of the spermatozoa was not affected by incubation in medium of 315 mosm/kg as compared to spermatozoa incubated in medium of 285 mosm/kg. However, the fertilizing capacity of the spermatozoa incubated in medium of 345 mosm/kg was significantly reduced. The present study indicates that there is no advantage in the use of hyperosmotic media of 315 or 345 mosm/kg for capacitation of spermatozoa in human IVF.

Cytogenetic analysis of in vitro fertilization (IVF) failures

Cytogenetic studies were carried out on 150 oocytes obtained in a human in vitro fertilization (IVF) program. Although all cells lacked signs of fertilization at light microscopy, 46 (30.7%) appeared to show cytological evidence of fertilization. At least one-third of these cells (with development arrested before first cleavage) had chromosomal aberrations. An aneuploidy rate of 35% was found in unfertilized oocytes. The results of this study explain some of the fertilization failures and of the failures of postfertilization development.