Supported Contribution
The Promise of Leadless Pacing Based on Presentations at Nanostim Sponsored Symposium Held at the European Society of Cardiology Congress 2013, Amsterdam, The Netherlands, 2 September 2013 K a trina Mou n t f o r t , M e d i c a l Wr i t e r , R a d c l i f f e Ca r d i o l o g y R ev iewed for a c c ura c y b y : Re i n o u d Kn o p s , 1 J o h a n n e s S p e r z e l 2 a n d P e t r N e u z i l 3 1. Electrophysiologist, Academic Medical Centre, University of Amsterdam, The Netherlands; 2. Director, Department of Cardiology, Kerckhoff Heart Centre, Bad Nauheim, Germany; 3. Chairman, Department of Cardiology, Homolka Hospital, Prague, Czech Republic
Abstract Pacemaker technologies have advanced dramatically over the decades since they were first introduced, and every year many thousands of new implants are performed worldwide. However, there continues to be a high incidence of acute and chronic complications, most of which are linked to the lead or the surgical pocket created to hold the device. A leadless pacemaker offers the possibility of bypassing these complications, but requires a catheter-based delivery system and a means of retrieval at the end of the device’s life, as well as a way of repositioning to achieve satisfactory pacing thresholds and R waves, a communication system and low peak energy requirements. A completely self-contained leadless pacemaker has recently been developed, and its key characteristics are discussed, along with the results of an efficacy and safety trial in an animal model. The results of the LEADLESS study, the first human trial to look at safety and feasibility of the leadless device, are discussed and the possible implications for future clinical practice examined.
Keywords Leadless pacemaker, cardiac arrhythmias, pacemaker-related complications, surgical pocket, venous thrombosis Disclosure: Reinoud Knops, Johannes Sperzel and Petr Neuzil have no conflicts of interest to declare Acknowledgement: The speaking panel acknowledge Radcliffe Cardiology for providing writing and editorial support. Received: 7 October 2013 Accepted: 24 April 2014 Citation: Arrhythmia & Electrophysiology Review 2014;3(1):51–5. Access at: www.AERjournal.com
Support: The publication of this article was supported by St Jude Medical
Why Leadless Pacing? Re i n o u d Kn o p s Academic Medical Centre, University of Amsterdam, The Netherlands
In 1958, the world’s first patient was implanted with a pacemaker. It brought numerous benefits, the most important of which was increased survival. Since then, pacemaker technology has evolved with the development of improved device longevity, by including a high-energy density battery and utilising high impedance, low threshold leads. Implantable pulse generators (IPGs) for cardiac arrhythmias are now a proven and widely used treatment method. A worldwide cardiac pacing and implantable cardioverter-defibrillator (ICD) survey found that in 2009 there were over 700,000 new implants, with the majority of these implants being performed in the US and Europe, but the greatest growth occurring in Asia.1 Despite new developments in pacemaker technology, there is still a high incidence of pacemaker-related complications.2 A large prospective multicentre study found that after two months 12 % of patients present with acute complications (see Figure 1).3 Chronic
© RADCLIFFE CARDIOLOGY 2014
Nanostim_editedTL.indd 51
complications subsequently occur in 10 % of patients. Most of these complications are related to the lead or the surgical pocket created to hold the pacemaker. Local pocket-related complications include haematoma, wound pain, decreased mobility, pocket erosion and infection. Pocket infection can be a serious complication, which occurs in 0.5–1.5 % of implants, but has a mortality of 10 %. Staphylococcus aureus is the main source of infection and is becoming increasingly antibiotic resistant. Pocket haematoma is also a relatively common complication. It is usually benign and treated conservatively but sometimes requires repeated surgery, which can be a major issue in patients who use anticoagulant drugs.4,5 However, the greatest potential for a complication in a pacemaker procedure is related to the lead. The overall incidence of clinical problems related to the lead is around 8 %.6 Mechanical failure and lead dislodgement are relatively common complications.
51
25/04/2014 16:44
Supported Contribution
Survival free from any pacemaker complication
Figure 1: Kaplan–Meier Curve with Survival Free from Any Pacemaker Complication
Figure 3: Leadless Cardiac Pacemaker Delivery Catheter
1.00
0.95
12.4 % at 2 months 0.90
0.85
0.80
Figure 4: Positioning of the Leadless Cardiac Pacemaker in the Myocardium
0.75 0
2
4
6
8
Years after implantation Patients at risk
1,517
1068
815
271
Source: Udo, et al. 2012.3
Figure 2: Design of the Leadless Pacemaker Docking Button
Battery
Electronics
Fixation Sutures
Helix
Manufacturers’ databases report fracture or failure numbers of about 0.1–0.5 % per year,7–9 but in Danish pacemaker registry data, rates of 1.5 % per year were reported.10 Other potential complications include puncture of the lung with a pacemaker lead (incidence is around 2 %).11 The lead may also perforate the right ventricle, leading to pericardial infusion and necessitating surgery.12,13 Severe complications require lead extraction, which is performed percutaneously with a laser sheath or mechanical snare. This is a complex surgical procedure, with unavoidable risks, including possible tearing of the surrounding blood vessel or perforating the heart.14–16 The concept of a self-contained leadless pacemaker (LP) was first reported in 1970.17 However, the battery did not last more than a few weeks. Following advances in battery technology, endocardial fixation and delivery systems, the concept has been revisited. The requirements of a LP are a catheter-based delivery system and a dependable fixation design. It is also important to be able to reposition the device acutely to achieve satisfactory pacing thresholds and R waves, and then retrieve the device chronically after the device has reached end of service. The device should be small to enable percutaneous delivery, with low power electronics and a high-density energy source. This requires a novel communication scheme with low peak energy requirements. The device must be biocompatible and have features comparable to conventional pacemakers in terms of electrical output, battery longevity and other functions such as rate response. Recently, a completely self-contained LP has been developed by St. Jude Medical (see Figure 2). The 1 cc and 2 g device is delivered percutaneously via the femoral vein through a Nanostim™ 18 F introducer with a steerable
52
Nanostim_editedTL.indd 52
catheter. It has a docking feature, which allows attachment of the device to a catheter for delivery, repositioning and retrieval. The chemical cell is a lithium carbon monofluoride (Li-CFx) battery, with an equivalent longevity compared with conventional pacemakers. The single integrated circuit chip senses, paces and communicates to a programmer. The chip uses a quarter of the current of standard chips, providing the same longevity as a conventional pacemaker, while reducing battery volume. The device is fixed into the right ventricle (RV) without leads or a surgical pocket. The primary fixation mechanism is provided via a helix and tines add secondary fixation. The distal tip features a steroid-eluting electrode that paces from the tip to the can. The pacemaker functions are the same as standard single chamber rate responsive pacemakers (VVIR) with hysteresis. The standard means of communication via radiofrequency (RF) requires an antenna or a coil and a high active current (5 mA). The Nanostim™ leadless pacemaker therefore features conducted communication involving small electric pulses through the human body that are picked up with standard surface electrocardiogram (ECG) electrodes. This eliminates the need for an antenna or a coil; there is no added circuit module and the system communicates in the refractory period of the heart, and it has low active current of
The Promise of Leadless Pacing Based on Presentations at Nanostim Sponsored Symposium Held at the European Society of Cardiology Congress 2013, Amsterdam, The Netherlands, 2 September 2013 K a trina Mou n t f o r t , M e d i c a l Wr i t e r , R a d c l i f f e Ca r d i o l o g y R ev iewed for a c c ura c y b y : Re i n o u d Kn o p s , 1 J o h a n n e s S p e r z e l 2 a n d P e t r N e u z i l 3 1. Electrophysiologist, Academic Medical Centre, University of Amsterdam, The Netherlands; 2. Director, Department of Cardiology, Kerckhoff Heart Centre, Bad Nauheim, Germany; 3. Chairman, Department of Cardiology, Homolka Hospital, Prague, Czech Republic
Abstract Pacemaker technologies have advanced dramatically over the decades since they were first introduced, and every year many thousands of new implants are performed worldwide. However, there continues to be a high incidence of acute and chronic complications, most of which are linked to the lead or the surgical pocket created to hold the device. A leadless pacemaker offers the possibility of bypassing these complications, but requires a catheter-based delivery system and a means of retrieval at the end of the device’s life, as well as a way of repositioning to achieve satisfactory pacing thresholds and R waves, a communication system and low peak energy requirements. A completely self-contained leadless pacemaker has recently been developed, and its key characteristics are discussed, along with the results of an efficacy and safety trial in an animal model. The results of the LEADLESS study, the first human trial to look at safety and feasibility of the leadless device, are discussed and the possible implications for future clinical practice examined.
Keywords Leadless pacemaker, cardiac arrhythmias, pacemaker-related complications, surgical pocket, venous thrombosis Disclosure: Reinoud Knops, Johannes Sperzel and Petr Neuzil have no conflicts of interest to declare Acknowledgement: The speaking panel acknowledge Radcliffe Cardiology for providing writing and editorial support. Received: 7 October 2013 Accepted: 24 April 2014 Citation: Arrhythmia & Electrophysiology Review 2014;3(1):51–5. Access at: www.AERjournal.com
Support: The publication of this article was supported by St Jude Medical
Why Leadless Pacing? Re i n o u d Kn o p s Academic Medical Centre, University of Amsterdam, The Netherlands
In 1958, the world’s first patient was implanted with a pacemaker. It brought numerous benefits, the most important of which was increased survival. Since then, pacemaker technology has evolved with the development of improved device longevity, by including a high-energy density battery and utilising high impedance, low threshold leads. Implantable pulse generators (IPGs) for cardiac arrhythmias are now a proven and widely used treatment method. A worldwide cardiac pacing and implantable cardioverter-defibrillator (ICD) survey found that in 2009 there were over 700,000 new implants, with the majority of these implants being performed in the US and Europe, but the greatest growth occurring in Asia.1 Despite new developments in pacemaker technology, there is still a high incidence of pacemaker-related complications.2 A large prospective multicentre study found that after two months 12 % of patients present with acute complications (see Figure 1).3 Chronic
© RADCLIFFE CARDIOLOGY 2014
Nanostim_editedTL.indd 51
complications subsequently occur in 10 % of patients. Most of these complications are related to the lead or the surgical pocket created to hold the pacemaker. Local pocket-related complications include haematoma, wound pain, decreased mobility, pocket erosion and infection. Pocket infection can be a serious complication, which occurs in 0.5–1.5 % of implants, but has a mortality of 10 %. Staphylococcus aureus is the main source of infection and is becoming increasingly antibiotic resistant. Pocket haematoma is also a relatively common complication. It is usually benign and treated conservatively but sometimes requires repeated surgery, which can be a major issue in patients who use anticoagulant drugs.4,5 However, the greatest potential for a complication in a pacemaker procedure is related to the lead. The overall incidence of clinical problems related to the lead is around 8 %.6 Mechanical failure and lead dislodgement are relatively common complications.
51
25/04/2014 16:44
Supported Contribution
Survival free from any pacemaker complication
Figure 1: Kaplan–Meier Curve with Survival Free from Any Pacemaker Complication
Figure 3: Leadless Cardiac Pacemaker Delivery Catheter
1.00
0.95
12.4 % at 2 months 0.90
0.85
0.80
Figure 4: Positioning of the Leadless Cardiac Pacemaker in the Myocardium
0.75 0
2
4
6
8
Years after implantation Patients at risk
1,517
1068
815
271
Source: Udo, et al. 2012.3
Figure 2: Design of the Leadless Pacemaker Docking Button
Battery
Electronics
Fixation Sutures
Helix
Manufacturers’ databases report fracture or failure numbers of about 0.1–0.5 % per year,7–9 but in Danish pacemaker registry data, rates of 1.5 % per year were reported.10 Other potential complications include puncture of the lung with a pacemaker lead (incidence is around 2 %).11 The lead may also perforate the right ventricle, leading to pericardial infusion and necessitating surgery.12,13 Severe complications require lead extraction, which is performed percutaneously with a laser sheath or mechanical snare. This is a complex surgical procedure, with unavoidable risks, including possible tearing of the surrounding blood vessel or perforating the heart.14–16 The concept of a self-contained leadless pacemaker (LP) was first reported in 1970.17 However, the battery did not last more than a few weeks. Following advances in battery technology, endocardial fixation and delivery systems, the concept has been revisited. The requirements of a LP are a catheter-based delivery system and a dependable fixation design. It is also important to be able to reposition the device acutely to achieve satisfactory pacing thresholds and R waves, and then retrieve the device chronically after the device has reached end of service. The device should be small to enable percutaneous delivery, with low power electronics and a high-density energy source. This requires a novel communication scheme with low peak energy requirements. The device must be biocompatible and have features comparable to conventional pacemakers in terms of electrical output, battery longevity and other functions such as rate response. Recently, a completely self-contained LP has been developed by St. Jude Medical (see Figure 2). The 1 cc and 2 g device is delivered percutaneously via the femoral vein through a Nanostim™ 18 F introducer with a steerable
52
Nanostim_editedTL.indd 52
catheter. It has a docking feature, which allows attachment of the device to a catheter for delivery, repositioning and retrieval. The chemical cell is a lithium carbon monofluoride (Li-CFx) battery, with an equivalent longevity compared with conventional pacemakers. The single integrated circuit chip senses, paces and communicates to a programmer. The chip uses a quarter of the current of standard chips, providing the same longevity as a conventional pacemaker, while reducing battery volume. The device is fixed into the right ventricle (RV) without leads or a surgical pocket. The primary fixation mechanism is provided via a helix and tines add secondary fixation. The distal tip features a steroid-eluting electrode that paces from the tip to the can. The pacemaker functions are the same as standard single chamber rate responsive pacemakers (VVIR) with hysteresis. The standard means of communication via radiofrequency (RF) requires an antenna or a coil and a high active current (5 mA). The Nanostim™ leadless pacemaker therefore features conducted communication involving small electric pulses through the human body that are picked up with standard surface electrocardiogram (ECG) electrodes. This eliminates the need for an antenna or a coil; there is no added circuit module and the system communicates in the refractory period of the heart, and it has low active current of
