Transcatheter Mitral Valve Replacement for Native and Failed Bioprosthetic Mitral Valves

Transcatheter mitral valve replacement (TMVR) is a novel approach for treatment of severe mitral regurgitation. A number of TMVR devices are currently undergoing feasibility trials using both transseptal and transapical routes for device delivery. Overall experience worldwide is limited to fewer than 200 cases. At present, the 30-day mortality exceeds 30% and is attributable to both patient- and device-related factors. TMVR has been successfully used to treat patients with degenerative mitral stenosis (DMS) as well as failed mitral bioprosthesis and mitral repair using transcatheter mitral valve-in-valve (TMViV)/valve-in-ring (ViR) repair. These patients are currently treated with devices designed for transcatheter aortic valve replacement. Multicenter registries have been initiated to collect outcomes data on patients currently undergoing TMViV/ViR and TMVR for DMS and have confirmed the feasibility of TMVR in these patients. However, the high periprocedural and 30-day event rates underscore the need for further improvements in device design and multicenter randomized studies to delineate the role of these technologies in patients with mitral valve disease.

Transcatheter mitral valve replacement with a novel self-expandable prosthesis: single institutional experience procedural outcomes and follow-up

AIMS

We report our experience with the CardiAQ prosthetic valve using both transapical and transseptal access. Aim of our study was proving the feasibility, safety and effectiveness of a novel transcatheter mitral valve bioprosthesis.

METHODS

Four patients with severe mitral regurgitation, not eligible for mitral valve surgery, were treated with the CardiAQ valve. The procedures were performed under general anaesthesia, fluoroscopic and transesophageal echocardiographic guidance. We used a transapical approach in two patients and transseptal access in the others.

RESULTS

Procedural success was obtained in all patients without extracorporeal circulation support. Mean procedure time was 128 min (range 90-180) and mean hospitalization duration was 12 days (range 4-24). The transseptal approach resulted in significantly shorter in-hospital stay with quick recovery. One patient died on day 35 from septicaemia and another one died after 5 months from major bleeding. The survival patients are presently in New York Heart Association I-II with improved left ventricular ejection fraction and normal quality of life.

CONCLUSION

CardiAQ valve placement is safe using a transapical or transseptal approach. Following valve replacement, there was a marked functional improvement in survivors. Transcatheter mitral valve replacement is a promising therapy for mitral regurgitation in a selected patient population.

Shortening cardioplegic arrest time in patients undergoing combined coronary and valve surgery: results from a multicentre randomized controlled trial: the SCAT trial

OBJECTIVES

Combined coronary artery bypass grafting and valve surgery requires a prolonged period of cardioplegic arrest (CA) predisposing to myocardial injury and postoperative cardiac-specific complications. The aim of this trial was to reduce the CA time in patients undergoing combined coronary artery bypass grafting and valve surgery and assess if this was associated with less myocardial injury and related complications.

METHODS

Participants were randomized to (i) coronary artery bypass grafting performed on the beating heart with cardiopulmonary bypass support followed by CA for the valve procedure (hybrid) or (ii) both procedures under CA (conventional). To assess complications related to myocardial injury, we used the composite of death, myocardial infarction, arrhythmia, need for pacing or inotropes for >12 h. To assess myocardial injury, we used serial plasma troponin T and markers of metabolic stress in myocardial biopsies.

RESULTS

Hundred and sixty patients (80 hybrid and 80 conventional) were randomized. Mean age was 66.5 years and 74% were male. Valve procedures included aortic (61.8%) and mitral (33.1%) alone or in combination (5.1%). CA time was 16% lower in the hybrid group [median 98 vs 89 min, geometric mean ratio (GMR) 0.84, 95% confidence interval (CI) 0.77-0.93, P  = 0.0004]. Complications related to myocardial injury occurred in 131/160 patients (64/80 conventional, 67/80 hybrid), odds ratio 1.24, 95% CI 0.54-2.86, P  = 0.61. Release of troponin T was similar between groups (GMR 1.04, 95% CI 0.87-1.24, P  = 0.68). Adenosine monophosphate was 28% lower in the hybrid group (GMR 0.72, 95% CI 0.51-1.02, P  = 0.056).

CONCLUSIONS

The hybrid procedure reduced the CA time but myocardial injury outcomes were not superior to conventional approach.

TRIAL REGISTRATION

ISRCTN65770930.

Single In x Ga1-x As nanowire/p-Si heterojunction based nano-rectifier diode

Nanoscale power supply units will be indispensable for fabricating next generation smart nanoelectronic integrated circuits. Fabrication of nanoscale rectifier circuits on a Si platform is required for integrating nanoelectronic devices with on-chip power supply units. In the present study, a nanorectifier diode based on a single standalone In _x Ga_1-x As nanowire/p-Si (111) heterojunction fabricated by metal organic chemical vapor deposition technique has been studied. The nanoheterojunction diodes have shown good rectification and fast switching characteristics. The rectification characteristics of the nanoheterojunction have been demonstrated by different standard waveforms of sinusoidal, square, sawtooth and triangular for two different frequencies of 1 and 0.1 Hz. Reverse recovery time of around 150 ms has been observed in all wave response. A half wave rectifier circuit with a simple capacitor filter has been assembled with this nanoheterojunction diode which provides 12% output efficiency. The transport of carriers through the heterojunction is investigated. The interface states density of the nanoheterojunction has also been determined. Occurrence of output waveforms incommensurate with the input is attributed to higher series resistance of the diode which is further explained considering the dimension of p-side and n-side of the junction. The sudden change of ideality factor after 1.7 V bias is attributed to recombination through interface states in space charge region. Low interface states density as well as high rectification ratio makes this heterojunction diode a promising candidate for future nanoscale electronics.

The Effects of Preoperative Volume Replacement in Diabetic Patients Undergoing Coronary Artery Bypass Grafting Surgery: Protocol for a Randomized Controlled Trial (VeRDiCT Trial)

Background

Diabetes mellitus is a major risk factor for prolonged hospital stays, renal failure, and mortality in patients having coronary artery bypass grafting (CABG). Complications pose a serious threat to patients and prolong intensive care and hospital stays. Low glomerular filtration rate (GFR) due to existing renal impairment or volume depletion may exacerbate acute renal impairment/failure in these patients. Preoperative volume replacement therapy (VRT) is reported to increase the GFR and we hypothesize that VRT will reduce renal impairment and related complications in diabetic patients.

Objective

The objective of this study is to establish the efficacy of preoperative VRT in reducing postoperative complications in diabetic patients undergoing CABG surgery. Time to “fit for discharge”, incidence of postoperative renal failure, cardiac injury, inflammation, and other health outcomes will be investigated.

Methods

In this open parallel group randomized controlled trial, 170 diabetic patients undergoing elective or urgent CABG surgery received 1 mL/kg/hour of Hartmann’s solution for 12 consecutive hours prior to surgery, versus routine care. The primary outcome was time until participants were “fit for discharge”, which is defined as presence of: normal temperature, pulse, and respiration; normal oxygen saturation on air; normal bowel function; and physical mobility. Secondary outcomes included: incidence of renal failure; markers of renal function, inflammation, and cardiac damage; operative morbidity; intensive care stay; patient-assessed outcome, including the Coronary Revascularization Outcome Questionnaire; and use of hospital resources.

Results

Recruitment started in July 2010. Enrolment for the study was completed in July 2014. Data analysis commenced in December 2016. Study results will be submitted for publication in the summer of 2017.

Conclusions

VRT is a relatively easy treatment to administer in patients undergoing surgical procedures who are at risk of renal failure. This experimental protocol will increase scientific and clinical knowledge of VRT in diabetic patients undergoing elective or urgent CABG surgery. Findings supporting the efficacy of this intervention could easily be implemented in the health care system.

Trial Registration

International Standard Randomized Controlled Trial Number (ISRCTN): 02159606; http://www.controlled-trials.com/ISRCTN02159606 (Archived by WebCite at http://www.webcitation.org/6rDkSSkkK)

Transcatheter aortic valve implantation through distal axillary artery: novel option for vascular access

AIMS

We describe an alternative access approach for patients undergoing transcatheter aortic valve implantation (TAVI) using surgical cut down of the distal axillary artery, in cases wherein transfemoral access is not feasible.

METHODS

From January 2012 to July 2013, 61 patients (59% men; mean age 81 ± 8 years) underwent TAVI at our institution. The mean logistic EuroSCORE and EuroSCORE II were 36 ± 24 and 14 ± 10, respectively. We assessed device success, 30-day safety and clinical efficacy using VARC II criteria.

RESULTS

TAVI was performed with the CoreValve Revalving System (CRS) (Medtronic Inc., Minneapolis, Minnesota, USA) in all cases, using transfemoral approach in 57 patients and distal trans-axillary route in four patients. A device was successfully implanted in 94%, without any major intraprocedural complications. One case of acute kidney disease, four cases of minor vascular complication and two cases of life-threatening bleeding occurred after the procedure for pericardial bleeding requiring pericardiocentesis. Permanent pacemaker was implanted in 26% of patients. There was no instance of in-hospital mortality, while two deaths (3%) occurred in the first 30 days. The total procedure time (skin-to-skin) was longer in the trans-axillary group secondary to surgical management of access site (P = 0.027), whereas revalving and fluoroscopy time were similar (P = 0.95 and P = 0.83, respectively).

CONCLUSION

The location and anatomical relations of the distal axillary artery make it a safer, reproducible and operator friendly access option for TAVI.

Current status of transcatheter aortic valve replacement

The advent of transcatheter aortic valve replacement (TAVR) has modified the treatment of severe aortic stenosis (AS). Large randomized trials and multicenter registries have endorsed the efficacy of TAVR in improving outcomes in patients with severe AS who are inoperable or high surgical risk. There has been a noticeable shift in using TAVR in patients with AS who are not at a high surgical risk. Appropriate diagnosis, patient selection, and referral remain cornerstones to achieving optimal outcomes after TAVR or SAVR (surgical aortic valve replacement).

Synthesis of graphene oxide–silver nanocomposite with photochemically grown silver nanoparticles to use as a channel material in thin film field effect transistors

The transport of charge carriers in a graphene oxide–silver nanoparticle composite is found to be controlled by nanoparticle dose.

Leakage current characteristics in MOCVD grown InAs quantum dot embedded GaAs metal-oxide-semiconductor capacitor

Carrier transport vis-a-vis leakage current in GaAs MOS capacitors with various structures; quantum dot embedded devices show the lowest leakage.