Safety and acute performance of paroxysmal and early persistent atrial fibrillation ablation using temperature-controlled, very high power, short duration catheter with a new radiofrequency generator

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Biosense Webster Inc.

Background/Introduction

The temperature-controlled contact force radiofrequency (RF) ablation catheter (QDM) has 6 thermocouples to maintain target catheter tip temperature and 3 tip microelectrodes for high local signal resolution. It has an enhanced irrigation profile to reduce char formation. Three prospective multicenter trials demonstrated safety and effectiveness of the QDM catheter using very high-power, short duration (vHPSD; 90W/4s), conventional power (CP; ≤50W) or combined modes. These studies were performed with an older RF generator. A new generator was developed to support the full suite of legacy, temperature controlled and multichannel ablation catheters, but has not yet been formally tested in a clinical setting.

Purpose

Evaluate safety and acute performance of the QDM catheter with the new 90W-enabled generator.

Methods

This prospective, multicenter study (4 Canadian sites) used vHPSD as primary mode for Pulmonary Vein (PV) isolation with overlapping 3mm lesion tags for anterior, inferior and roof of left atrium. Adjacent, non-overlapping lesions were used posteriorly to avoid esophageal heating. CP mode was used at operator discretion for thicker atrial tissue, touch ups, and non-PV triggers (Figure). Primary endpoint was confirmed entrance block in all PVs after adenosine and/or isoproterenol challenge. Acute procedural and safety data were assessed. Systematic char evaluation was performed.

Results

Effectiveness analysis included 38/40 subjects with mean 110-day follow up (mean age, 61.7 ± 9.5 years; 63.2% male). Hypertension (47.4%) and congestive heart failure (15.8%) were the most common comorbidities. Fourteen subjects were treated with version V0 of the generator, and 24 subjects were treated using version V1c which included further software adjustments to the power titration, and current response to optimize performance. Combination vHPSD/CP workflow was used for PV isolation in 28 (75.7%) subjects and vHPSD was used solely in 10. A non-study catheter was used in 1 subject during connectivity troubleshooting. Primary endpoint of entrance block confirmation was achieved in 37/38 subjects and in all 37 subjects treated with study catheter only. No incidences of char or device-related adverse events were reported. There were no noted differences in the endpoints evaluated between the V0 and V1c groups. Median (Q1/Q3) RF application times for ablating PVs was 13.0 min (9.0/16.0) for the entire cohort. Median (Q1/Q3) time to achieve PV isolation in vHPSD-only group was 9 (7/12) min, and 14 (11/18) min, respectively.

Conclusion(s)

Consistent with data from prior 3 clinical studies, QDM catheter with the new 90W-enabled generator demonstrated the acute safety and effectiveness of temperature-controlled AF ablation with short PV ablation time and no char observed.

Value of VKORC1 (-1639G>A) rs9923231 genotyping in predicting warfarin dose: A replication study in South Indian population

OBJECTIVE

Warfarin is the most commonly prescribed oral anticoagulant, although having a narrow therapeutic index and wide interindividual variability. The aim of this study was to replicate the utility of VKORC1 (-1639G>A) rs9923231 genotyping in predicting the mean daily dose and to evaluate its ability to categorize warfarin-treated patients to high-, intermediate-, or low-dose categories in the South Indian population.

MATERIALS AND METHODS

A cohort of 222 warfarin-treated patients was genotyped using restriction fragment length polymorphism method. The influence of the rs9923231 polymorphism on the variations in the mean daily dose was compared using one-way analysis of variance and linear regression analysis. Discriminatory ability of the rs9923231 polymorphism to group the patients into ordered dose categories was assessed by estimating the proportional odds ratios using the ordered logit regression analysis.

RESULTS

The frequency of AA genotype and A allele in the study sample was found to be 1.8% and 9.23%, respectively, which was similar to reports from other South Indian populations. The mean daily dose required to achieve the optimum international normalized ratio was significantly lower in AA homozygous genotype carriers (3.99 ± 1.67 mg/day) and GA heterozygous (4.26 ± 1.57 mg/day) compared to the GG genotype carriers (5.51 ± 2.13 mg/day), p = 0.003. The A allele carriers (GA+AA genotypes) had a 3.23 higher odds of being grouped as a low-dose requiring category compared to non-carriers (95% CI 1.49-6.98, p = 0.003).

CONCLUSIONS

These preliminary results strongly support the use of VKORC1 (-1639G>A) rs9923231 polymorphism for genetically guided initial warfarin dosing in South Indian patients with heart valve replacements.

Lack of association of mirSNP rs11174811 in AVPR1A gene with arterial blood pressure and hypertension in South Indian population

Epigenetic regulation of arterial blood pressure mediated through mirSNPs in renin-angiotensin aldosterone system (RAAS) genes is a less explored hypothesis. Recently, the mirSNP rs11174811 in the 3'UTR of the AVPR1A gene was associated with higher arterial blood pressure in a large study population from the Study of Myocardial Infarctions Leiden (SMILE). The aim of the present study was to replicate the association of mirSNP rs11174811 with blood pressure outcomes and hypertension in a south Indian population. Four hundred and fifteen hypertensive cases and 416 normotensive controls were genotyped using a 5' nuclease allelic discrimination assay. Logistic regression was used to test the association of mirSNP rs11174811 with the hypertension phenotype. Censored normal regression was used to test the association of the polymorphism with continuous blood pressure outcomes such as systolic and diastolic blood pressure. The mirSNP rs11174811 did not show any significant association with hypertension. The adjusted odds ratio was 1.02, with 95% CI of 0.72 to 1.45 (p = 0.909). The mean systolic and diastolic blood pressure values were not significantly different across the three genotypic groups, between hypertensives and normotensives, or when stratified by gender. Despite having a similar minor allele frequency (MAF) of 14.5% compared with the SMILE cohort, our results did not support an association of the mirSNP rs11174811 with the hypertension phenotype or with continuous blood pressure outcomes in the south Indian population.

Evaluating genomic DNA extraction methods from human whole blood using endpoint and real-time PCR assays

The extraction of genomic DNA is the crucial first step in large-scale epidemiological studies. Though there are many popular DNA isolation methods from human whole blood, only a few reports have compared their efficiencies using both end-point and real-time PCR assays. Genomic DNA was extracted from coronary artery disease patients using solution-based conventional protocols such as the phenol-chloroform/proteinase-K method and a non-phenolic non-enzymatic Rapid-Method, which were evaluated and compared vis-a-vis a commercially available silica column-based Blood DNA isolation kit. The appropriate method for efficiently extracting relatively pure DNA was assessed based on the total DNA yield, concentration, purity ratios (A₂₆₀/A₂₈₀ and A₂₆₀/A₂₃₀), spectral profile and agarose gel electrophoresis analysis. The quality of the isolated DNA was further analysed for PCR inhibition using a murine specific ATP1A3 qPCR assay and mtDNA/Y-chromosome ratio determination assay. The suitability of the extracted DNA for downstream applications such as end-point SNP genotyping, was tested using PCR-RFLP analysis of the AGTR1-1166A>C variant, a mirSNP having pharmacogenetic relevance in cardiovascular diseases. Compared to the traditional phenol-chloroform/proteinase-K method, our results indicated the Rapid-Method to be a more suitable protocol for genomic DNA extraction from human whole blood in terms of DNA quantity, quality, safety, processing time and cost. The Rapid-Method, which is based on a simple salting-out procedure, is not only safe and cost-effective, but also has the added advantage of being scaled up to process variable sample volumes, thus enabling it to be applied in large-scale epidemiological studies.

An efficient in vitro propagation methodology for Annatto (Bixa orellana L.)

Efficient methods were developed for both in vitro seed germination and micropropagation of an economically important dye yielding multipurpose tree, Bixa orellana L. Mature seeds were inoculated onto Murashige and Skoog (MS) medium supplemented with different concentrations of gibberellic acid (GA3). Highest frequency of germination (93.3 %) was recorded on medium supplemented with 3 μM GA3 against 13.33 % in control. Nodal explants cultured on MS medium fortified with 5 μM isopentanyl adenine (2-iP) produced maximum explants response (93.3 %) and highest number of shoots (35.71). Addition of relatively higher concentration (15 μM) of benzyl adenine (BA) resulted in the production of significantly (P < 0.05) reduced number of shoots (12.66). Sucrose at 87.6 mM was found to be the best carbohydrate source for multiple shoot induction compared to glucose and fructose. Regenerated shoots (3-4 cm) were rooted (95.5 %) on agar gelled MS medium supplemented with 10 μM indole-3-butyric acid (IBA). In vitro developed plantlets with well-developed roots were potted and acclimatized initially in the growth chamber and then moved to a green house with 83.3 % survival. The present protocol avoids the use of auxins in shoot multiplication medium, which will lower the cost, avoid callus formation and thus reduces the possibility of somaclonal variation in the regenerated plants. The method is efficient to produce over 32,000 hardened plants within a 10-month culture period starting from a single nodal explant.

Antibacterial effects of Coscinium fenestratum

Antibacterial activity of Coscinium fenestratum is mainly due to the presence of berberine.

Effect of auxins on berberine synthesis in cell suspension culture of Coscinium fenestratum (Gaertn.) Colebr--a critically endangered medicinal liana of Western Ghats

Cell suspension culture of critically endangered Coscinium fenestratum was established from young leaf segments on WPM supplemented with auxins. Effect of 2,4-D, IAA, IBA and NAA was examined on cell growth and berberine production. Berberine was synthesized and released continuously into the liquid medium. Presence of 2,4-D stimulated cell growth, but was not inhibitory on berberine synthesis. On the contrary, NAA stimulated berberine biosynthesis, but was not favourable for cell growth. Among the auxins tested, highest yield of berberine (5.79 mg/30 ml; 4.14 times to that of control) was obtained with 4 mg/l of NAA, while the best cell growth (214.43 mg dry wt., 1.96 times to that of control) was observed in the presence of 2 mg/l of 2,4-D. IAA and IBA were not favourable for cell growth and berberine synthesis.

Combinatorial techniques for M/G/1-type queues

The application of the generalised ballot theorem to queueing theory leads to elegant results for the simple M/G/1 queue. It is thought that such results are not possible for more general M/G/1-type queues. We, however, derive a batch ballot theorem which can be applied to derive the first passage distribution matrix, G, for the general M/G/1-type queue.

Somatic embryogenesis from leaf derived callus of Tylophora indica (Burm. f.) Merrill

Mature leaf explant derived callus of Tylophora indica (Burm. f.) Merrill yielded somatic embryos on MS medium supplied with BA(1-2 mg/L) or kinetin(1-5 mg/L) or kinetin/BA (1-2 mg/L) used along with IAA(0.1-1 mg/L). Maximum somatic embryos (30) could be recovered from 100 mg of embryogenic callus within 60 days at an optimum concentration of 2 mg/L of BA which was also best suited for providing the maximum conversion rate (90%) of embryoids to plantlets. Kinetin (1-5 mg/L), used as the sole growth hormone, induced the development of embryoids showing either shoot or root primordia in 30% of the cultures. However, embryoids with shoot primordia developed roots upon transfer to medium containing IAA(0.1 mg/L) and kinetin(2 mg/L). Embryoids from all cultures germinated in the initiation medium and were transplanted to sterile vermiculite for hardening. After two weeks of hardening, the plantlets were transferred to the green house where they grew and established well showing a high rate of survival (90%).

Treatment of true bifurcation stenosis by elective stent implantation in parent vessel and non-stent dilatation of side branch: immediate and follow-up results

Data of 67 consecutive patients who underwent stent implantation in the parent vessel and non-stent dilatation of the side branch of a true bifurcation stenosis was retrospectively analysed. The mean age was 53.2 +/- 9.7 years, with majority (89.6%) being males. Forty-seven (70.1%) lesions involved the bifurcation of left anterior descending artery and its major diagonal branch. The parent vessel was treated using balloon angioplasty in 50 (74.6%), rotational atherectomy in 15 (22.4%) and directional coronary atherectomy in 2 (3.0%) patients. All the patients subsequently received an intracoronary stent in the parent vessel. Depending upon the treatment strategy for the side branch, the patients were divided into two groups: (1) Percutaneous transluminal coronary angioplasty group, which included 37 patients in whom the side branch was dilated by plain balloon angioplasty, and (2) Debulking group, in which 30 patients underwent debulking of the side branch using rotablation or directional coronary atherectomy. Overall, the procedure was successful in 64 (95.6%) patients. One (1.5%) patient developed non-Q wave myocardial infarction during the hospital stay. There were no Q-wave myocardial infarction, need for emergency coronary artery bypass surgery or death. Clinical follow-up of at least six months was available in all patients with a mean duration of 9.5 +/- 3.2 months. Recurrence of symptoms developed in 19 (28.4%) patients. Fourteen (20.9%) patients required target vessel revascularisation, of which 11 (29.7%) belonged to the percutaneous transluminal coronary angioplasty group and 3 (10.0%) to the debulking group, the difference being statistically significant (p = 0.045). The freedom from target vessel revascularisation was 93.1 and 89.4 percent at 6 and 12 months in the debulking group, compared to 78.4 and 68.9 percent at the same time in the percutaneous transluminal coronary angioplasty group. This study thus demonstrates that percutaneous intervention for true bifurcation stenosis with stent implantation in the parent vessel and non-stent dilatation in the side branch provides favourable immediate and follow-up results. Debulking in comparison to plain balloon angioplasty of the side branch results in further improvement in clinical outcome and need for target vessel revascularisation on follow-up.