Electrical cardioversion during cryoballoon pulmonary vein isolation predicts long-term ablation success in persistent atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

Cryoballoon pulmonary vein isolation (cryoPVI) is an established option for treatment of atrial fibrillation (AF) but many periprocedural events influencing long-term outcome and procedural safety of ablation remain unclear. In radiofrequency ablation studies, failure to convert to sinus rhythm and electrical cardioversion (ECV) have been associated with increased recurrence rates. In this context, the influence of ECV during cryoPVI on long-term ablation efficacy is unclear.

Objective

A prospective comparison of AF recurrence after cryoballoon ablation in patients who were in AF or atrial tachycardia at the beginning of cryoPVI requiring ECV during procedure with patients who underwent ablation therapy without ECV.

Methods

We analyzed consecutive patients who underwent cryoPVI in a single-center cohort between 2018 and 2020. Follow-up was performed at 3, 6, 12, 18 and 24 months after ablation. Primary endpoints were: symptomatic AF recurrence for efficacy and bleeding, phrenic nerve injury, stroke or death for safety.

Results

472 consecutive patients who underwent ablation in a single-center cohort were analysed. Mean follow-up time was 15 months. In 195 patients (74 paroxysmal AF vs. 121 persistent AF, age 69 ± 10 years, 57% male, CHA2DS2-VASc 2.6 ± 1.4) at least one ECV was performed following ablation, while no cardioversion was necessary in 277 patients (214 paroxysmal AF vs. 63 persistent AF, age 69 ± 10 years, 55% male, CHA2DS2-VASc 2.7 ± 1.5). After 24 months, primary efficacy endpoint occurrence was significantly higher in persistent AF requiring cardioversion during procedure than for persistent AF without cardioversion and paroxysmal AF with/ without cardioversion (56.1 % vs. 31.2%, 33.6%, 32.9%, log-rank p = 0.009, figure). Primary safety endpoint occurred in form of pericardial effusion or transient phrenic nerve injury in two patients in cardioversion group (1.0%) and three patients without cardioversion (1.1%). No deaths or strokes were observed in either group. Total procedure duration (55.6 ± 17min vs. 57.7 ± 15.9min, P = 0.17) and left-atrial dwell time (39.7 ± 14.9min vs. 42 ± 15.6min, P = 0.11) were similar.

Conclusion

In patients with persistent AF, the need for ECV during cryoPVI predicts a poorer long-term outcome during 2-year follow-up. Future studies should focus on this specific patient population. Abstract Figure.

Cryoballoon pulmonary-vein isolation for atrial fibrillation with heart failure: results from a single-center cohort

Background

Atrial fibrillation (AF) and heart failure (HF) are of growing prevalence and increasing mortality. Radiofrequency ablation is safe and effective for patients with AF and HF. Prognosis might be improved in patients treated. However, there is no prospective trial investigating efficacy and safety of cryoballon ablation in patients with AF and HF.

Objective

To prospectively compare cryoballoon ablation in patients with and without HF (defined as LVEF ≤40%) in terms of safety and efficacy.

Methods

Ongoing POLAR-HF trial is a prospective, investigator-initiated, single-center, non-inferiority, open-label study. We analyzed 244 consecutive patients who underwent cryoballoon ablation. Of these 217 had normal LVEF (age 68.1±9.6 years, CHA2DS2-VASc Score 2.5±1.3, 55.3% male) while 27 patients (11%) suffered from HF (age 70.4±8.6 years, CHA2DS2-VASc Score 3±1.2, 70.4% male). Follow-up was performed at 3, 6 and 12 months after ablation. Kaplan-Meier method was used to calculate 12-month event-rate estimates. Log-Rank Test to estimate hazard ratios in the primary analysis. Endpoints were: symptomatic AF relapse for efficacy and bleeding, stroke or death for safety.

Results

Analysis showed no difference in AF-free survival rate between patients with and without HF (81% vs. 76.3%, Log-Rank-Test P=0.81, Figure). Primary safety end point occurred in 5 patients with normal LVEF (2.3%) and none in the HF-group. No deaths were observed.

Conclusion

Results of POLAR-HF indicate that cryoballoon ablation is an effective ablation method for patients suffering from AF and HF.

Event-Free Survival (Efficacy Endpoint)

Funding Acknowledgement

Type of funding source: None

Leydig cell hypoplasia: cases with new mutations, new polymorphisms and cases without mutations in the luteinizing hormone receptor gene

BACKGROUND

Defective male sex differentiation in patients with hypoplasia of Leydig cells (LCH) is caused by deficient LH receptor signal transduction. To further investigate the variety of LH receptor gene mutations present in LCH patients and their influence on the phenotype, we examined 10 nonrelated patients with the clinical presentation of LCH.

PATIENTS AND METHODS

Ten patients with a clinical phenotype of LCH were analysed for mutations in the complete coding region of the LH receptor gene. Exons 1-10 and two overlapping fragments of exon 11 of the LH receptor gene including all intron-exon boundaries were amplified by polymerase chain reaction and sequenced. To screen for frequencies of DNA changes, mutation analysis was performed on 45-59 healthy persons using denaturation high-performance liquid chromatography.

RESULTS

Six new DNA alterations were identified. Three of them appear to be new polymorphisms. A G to C change at the 28th nucleotide of intron 1 on one allele and a heterozygous CGA to CAA transition at codon 124 (R124Q) were found. Both findings in these two patients are polymorphisms that occur with a frequency of 17% and 1.7%, respectively. A silent heterozygous CTA to TTA change at codon 204 was identified. In a patient with micropenis, the analysis revealed a homozygous missense mutation at codon 625 (I625K). As reported previously, this alteration significantly impaired signal transduction and explains the partial phenotype. Finally, in one compound heterozygous patient, two different mutations were discovered. At the polymorphic site in exon 1, a 27-bp insertion (CTG)2 AAG (CTG)5 CAG and a premature stop codon in the transmembrane segment 4 (W491*) were found. Both mutations disrupt signal transduction and explain the complete phenotype of this patient. In five patients, no DNA alterations could be identified.

CONCLUSIONS

Three mutations (33 bp insertion in exon 1; W491* and I625K) were identified that explain the phenotype in two patients. In addition, most of the patients with the clinical phenotype of LCH did not have causative mutations, suggesting that changes in other regions of the LH receptor gene, such as the large introns or the promoter region, may be responsible for the majority of cases. Alternatively, the displayed phenotype may be the result of other genetic defects. Our work further underscores the importance of thorough clinical analysis of patients before molecular analysis of a particular gene is performed.

Tyrosine phosphorylation of GSalpha and inhibition of bradykinin-induced activation of the cyclic AMP pathway in A431 cells by epidermal growth factor receptor

An increasing amount of experimental data suggest that cross-talk exists between pathways involving tyrosine kinases and heterotrimeric G proteins. In a previous study, we demonstrated that bradykinin (BK) increases the intracellular accumulation of cAMP in the human epidermoid carcinoma cell line A431 by stimulating adenylate cyclase activity via a stimulatory G protein (Gsalpha) (Liebmann, C., Graness, A., Ludwig, B., Adomeit, A., Boehmer, A., Boehmer, F.-D., Nürnberg, B., and Wetzker, R. (1996) Biochem. J. 313, 109-118). Here, we present several lines of evidence indicating the ability of epidermal growth factor (EGF) to suppress BK-induced activation of the cAMP pathway in A431 cells via tyrosine phosphorylation of Gsalpha. Gsalpha was specifically immunoprecipitated from A431 cells using the anti-alphas antiserum AS 348. Tyrosine phosphorylation of Gsalpha was detectable in EGF-pretreated cells with monoclonal anti-phosphotyrosine antibodies. Additionally, A431 cells were labeled with [32P]orthophosphate in vivo and treated with EGF, and the resolved immunoprecipitates were subjected to amino acid analysis. The results clearly indicate that EGF induces tyrosine phosphorylation of Gsalpha in A431 cells. Treatment of A431 cells with EGF decreased BK-induced cAMP accumulation in intact cells as well as the stimulation of adenylate cyclase by BK, NaF, and guanyl nucleotides, but not by forskolin. Also, EGF treatment abolished both the BK- and isoprenaline-induced stimulation of guanosine 5'-O-(3-[35S]thiotriphosphate) binding to Gsalpha. In contrast, the BK-evoked, Gq-mediated stimulation of inositol phosphate formation in A431 cells was not affected by EGF pretreatment. Thus, EGF-induced tyrosine phosphorylation of Gsalpha is accompanied by a loss of its susceptibility to G protein-coupled receptors and its ability to stimulate adenylate cyclase via guanyl nucleotide exchange. We propose that Gsalpha may represent a key regulatory protein in the cross-talk between the signal transduction pathways of BK and EGF in A431 cells.

Molecular basis of androgen insensitivity

Male sexual differentiation and development proceed under direct control of androgens. Androgen action is mediated by the intracellular androgen receptor, which belongs to the superfamily of ligand-dependent transcription factors. In the X-linked androgen insensitivity syndrome, defects in the androgen receptor gene have prevented the normal development of both internal and external male structures in 46, XY individuals. The complete form of androgen insensitivity syndrome is characterized by 46, XY karyotype, external female phenotype, intra-abdominal testes, absence of uterus and ovaries, blindly ending vagina, and gynecomastia. There is also a group of disorders of androgen action that result from partial impairment of androgen receptor function. Clinical indications can be abnormal sexual development of individuals with a predominant male phenotype with severe hypospadias and micropenis or of individuals with a predominantly female phenotype with cliteromegaly, ambiguous genitalia, and gynecomastia. Complete or gross deletions of the androgen receptor gene have not been frequently found in persons with the complete androgen insensitivity syndrome, whereas point mutations at several different sites in exons 2-8 encoding the DNA- and androgen-binding domain have been reported in both partial and complete forms of androgen insensitivity, with a relatively high number of mutations in two clusters in exons 5 and 7. The number of mutations in exon 1 is extremely low, and no mutations have been reported in the hinge region, located between the DNA-binding domain and the ligand-binding domain. The X-linked condition of spinal and bulbar muscle atrophy (Kennedy's disease) is characterized by a progressive motor neuron degeneration associated with signs of androgen insensitivity and infertility. The molecular cause of spinal and bulbar muscle atrophy is an expanded length (> 40 residues) of one of the polyglutamine stretches in the N-terminal domain of the androgen receptor.

Dual bradykinin B2 receptor signalling in A431 human epidermoid carcinoma cells: activation of protein kinase C is counteracted by a GS-mediated stimulation of the cyclic AMP pathway

Cell membranes of the human epidermoid cell line A431 express classical bradykinin (BK) B2 receptors, as assessed by [3H]BK binding studies. Furthermore, stimulation by BK induced a time-dependent modulation of protein kinase C (PKC) activity in A431 cells: a rapid activation (t1/2 approximately 1 min) is followed by a slow inhibition (t1/2 approximately 20 min) of PKC translocation measured by [3H]phorbol 12,13-dibutyrate binding. In addition, BK stimulated both adenylate cyclase activity in A431 membranes and accumulation of intracellular cyclic AMP (cAMP) in intact cells in a retarded manner. A possible BK-induced activation of the cAMP pathway mediated via PKC, phospholipase D, prostaglandins or Ca2+/calmodulin was excluded. A 35 kDa protein was found in A431 membranes to be specifically phosphorylated in the presence of both BK and protein kinase A (PKA). An anti-alpha s-antibody, AS 348, abolished stimulation of adenylate cyclase activity in response to BK, cholera toxin and isoprenaline, strongly suggesting the involvement of Gs proteins in the BK action. The BK-activated cAMP signalling system might be important for the observed inactivation of PKC slowly evoked by BK: the BK-induced rapid activation of PKC is decreased by dibutyryl cAMP, and the slow inhibition of PKC is prevented by an inhibitor of PKA, adenosine 3':5'-monophosphothioate (cyclic, Rp isomer). The inhibition of PKC translocation might be exerted directly at the level of PKC activation, since stimulation of phosphoinositide hydrolysis by BK was affected by neither dibutyryl cAMP nor forskolin. Thus our results provide the first evidence that A431 cells BK is able to activate two independent signal-transduction pathways via a single class of B2 receptors but two different G proteins. The lagging stimulation of the cAMP signalling pathway via Gs might serve to switch off PKC, which is rapidly activated via Gq-mediated stimulation of phosphoinositide hydrolysis.

A complex bilateral polysyndactyly disease locus maps to chromosome 7q36

We demonstrated that the gene responsible for a congenital limb deformity (polysyndactyly) maps to chromosome 7q36 in a large family. Pre- and postaxial anomalies of the extremities are inherited in this family as an autosomal dominant trait. The disease locus is closely linked to D7S550 (maximum lod score = 6.85, theta = 0). This region is homologous to a segment of mouse chromosome 5, where the mutations hammer toe (HM) and hemimelic extra toes (HX) have been mapped. These data suggest that human chromosome 7q36 and the homologous region of mouse chromosome 5 contain genes involved in limb pattern formation.

How could canal-pluggings result in intensive direction changing type of positional nystagmus?

The objectives of this study in Rhesus monkeys is to observe the sequences which appear in the oculo-spinal-motor system after selected semicircular canals had been plugged. The left anterior and the right posterior canals in a monkey "LARP", the left anterior and posterior canals in "LALP", and the left lateral canal in "LL" were plugged under intubation general anesthesia. Three-dimensional eye recordings were performed, using two scleral coils. Behavior, posture, and vestibulo-ocular reflex were studied. Compensation was established in the light within 2 days. In darkness, no spontaneous nystagmus was recorded in the sitting position. The monkey "LALP" developed marked positional nystagmus. When the head position was changed up to 360 degrees in 15 degrees steps, horizontal, vertical and torsional eye movements showed remarkable changes. Spontaneous direction changing nystagmus in darkness was also recorded in "LALP". To conclude, direction changing positional nystagmus, which was seen for several months after the canal plugging, was difficult to explain by the damage to the adjacent ampullary and/or otolithic endorgans, but may be explained by the limited otolithic compensation in the earth parallel plane for the defective dynamic canal inputs. These observations and conclusions were from experiments using three monkeys only and should still be confirmed in more extended experiments.