New in Barcelona: a battery-free pacemaker, local anaesthesia in TAVI, and mapping AEDs
Drawing on their clock-making heritage, Swiss scientists are adapting technology from automatic watches to power pacemakers with nothing more than the motion of the beating heart. Their animal experience of ‘batteryless’ pacing will be described in an Abstract Session today.
‘Pacemakers have two weak spots,’ explained Adrian Zurbuchen, from the University of Bern. ‘Leads are prone to fracture and the lifetime of batteries is limited. Replacing batteries with alternative power sources would spare patients from repeated interventions and make leads obsolete.’
He explained that an automatic watch ‘harvests’ its energy from the wrist by transforming mechanical energy into electrical energy. Thus, attaching a pacemaker to the epicardium would allow the same system to be directly exposed to the accelerations of myocardial muscle. The motion of the heart winds a spring which accumulates mechanical energy.
In today’s study the harvesting device was extracted from an automatic wrist watch and encased in plastic housing with eyelets to allow suture to the epicardium of a 60 kg pig. Results showed that the device generated a mean output power of 52 microwatts - the energy consumption of modern pacemakers is known to be around 10 microwatts.
‘This answers our core question that heart motion can be converted into electrical energy that exceeds power requirements of modern pacemakers,’ said Zurbuchen, whose group now plans to reduce the size and weight of the prototype to make it more sensitive to heart motion. Zurbuchen added that the technology has potential for use in a multitude of devices, including defibrillators, loop recorders and drug delivery pumps.
Local anaesthesia (LA) is as safe and effective for TAVI as general anaesthesia (GA), according to new registry results. Initially TAVI procedures were cautiously performed under GA, but, with growing experience, more heart teams are switching to LA. This is considered suitable for the transfemoral route, but not for transapical and transaortic routes, which require mini thoracotomy and sternotomy.
In a study to be presented on Tuesday, Romain Chopard and colleagues recorded outcomes for 2871 consecutive patients undergoing TAVI in 34 French centres in the FRANCE 2 registry between January 2010 and December 2011. They showed that implantation was considered ‘successful’ in 97% of patients receiving LA and 97.6% receiving GA (p=0.12); immediate mortality occurred in 3.6% of patients in the LA group and 2.8% in the GA group (p=0.30); and the duration of hospital stay was 9.8 days in the GA group and 8.8 days in the LA group (p<0.001).
Over time there was a progressive increase in the use of LA, which rose from 32% of registry procedures in the first six months to almost 50% in the last six months.
‘The advantages of performing TAVI under local anaesthetic includes more accurate clinical assessments of patients during the procedure, optimisation of the TAVI process and enhanced patient recovery,’ said Chopard, from University Hospital of Besancon, France. ‘Our results would argue in favour of considering wider use of LA, even among high risk patients undergoing TAVI with transfemoral access.’
‘Geographic optimisation modelling’ can be used for identifying the best locations for automatic external defibrillators (AEDs), according to French investigators. ‘Systematic placement in well known and accessible public facilities accompanied by public information campaigns would make lay rescuers much more aware of AED locations,’ said Benjamin Dahan, from Paris Sudden Death Expertise Center, INSERM.
Currently, there is no standardised approach for optimal placement of AEDs. North American guidelines recommend sites with a ‘high likelihood of witnessed cardiac arrest’; European guidelines suggest locations where out-of-hospital cardiac arrests (OHCAs) occur at least once every two years.
In their study reported yesterday in an Abstract Session, Dahan and colleagues identified all the OHCAs managed by the Paris Emergency Medical Services between 2000 and 2010, and calculated median distances between the events and a range of different potential locations for AEDs.
Results showed that, of the 4176 OHCAs recorded, 1415 (34%) took place outside the home; 1355 had identifiable geographic co-ordinates amenable to mapping in geographic information systems. The median distance between OHCA and different locations was 324 metres for post offices, 239 metres for subway stations, 137 metres for bike-sharing stations and 142 metres for pharmacies.
‘Despite the high number of pharmacies in Paris, their irregular distribution doesn’t make them the best candidates for AEDs,’ said Dahan. ‘Instead we preferred public facilities like metro stations or bike-sharing stations. They also have the advantage of good visibility and public accessibility at night and during weekends.’
31 August, 11:00-12:30
Vilnius - Village 9
A batteryless cardiac pacemaker powered by cardiac motion
2 September, 11:00-12:30
Valetta (The Hub) - Central Village
Safety and efficacy of local versus general anaesthesia in patients undergoing transcatheter aortic valve implantation using a transfemoral approach: VARC-defined outcomes in the FRANCE 2 registry