RVADs/LVADs and all things mechanical by Dr Jayshree Lavana
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Survival in patients with advanced heart failure (AHF) has improved over the last 2 decades. An increasing number of patients however, are dying with progressive heart failure over the same duration. Optimal utilization of medical therapies and devices like implantable defibrillators and biventricular pacemakers are the likely reasons patients are surviving longer albeit with progressive HF. Evolution in mechanical circulatory support (MCS) devices has occurred over the same period, such that they can now be rapidly instituted providing support for pump failure, often percutaneously, with timely restitution of physiologic and metabolic derangements with fewer complications. MCS devices can be classified as Short term and Long term. Short term devices such as Intraaortic balloon pumps (IABP), Impella ®, TandemHeart® or Venoarterial extracorporeal membrane oxygenation (VA – ECMO) using a Cardiohelp® device, are usually employed as ‘Bridge to Recovery’(BTR) or Bridge to Decision’(BTD), usually in acute settings. Long term devices such as implantable left ventricular assist devices (LVADs) e.g. Heartmate II® & 3®, Heart ware HVAD® are implanted as ‘Bridge to transplant’ (BTT) or ‘Destination therapy’ (DT) usually in patients ‘sliding’ on inotropes when they are transplant eligible (BTT) or ineligible (DT) respectively. Ventricular assist devices have traditionally been developed for left ventricular support in case of severe left heart or biventricular dysfunction. Historically, right ventricular (RV) dysfunction following LVAD implantation or as a component of biventricular dysfunction was managed with either medical therapy, temporary VADs (i.e. ECMO configuration with continuous flow centrifugal pumps like CentriMag®, Rotaflow ®) or occasionally with LVADs placed on the right side. Recently the Impella RP® and ProtekDuo®, percutaneously placed pumps with inflow in the inferior vena cava & right atrium respectively and outflow in pulmonary artery, have become available as less invasive options, for short term RV support. The Syncardia® is the only approved total artificial heart system currently in use; however various biventricular, total heart systems (e.g. BiVACOR®) in development show promise. Mechanical circulatory devices provide attractive, viable, physiologically plausible ventricular support options that can be used effectively in carefully selected patients.
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RVADs/LVADs and all things mechanical by Dr Jayshree Lavana
- 1. RVADs/LVADs and all things mechanical Jayshree Lavana Adult Intensive Care Services The Prince Charles Hospital
- 2. Conflicts of Interest - none
- 3. • HF and Cardiogenic shock trends • Rationale • Types of pumps • Devices for Acute heart failure • Devices for Chronic heart failure • Devices for the Right side
- 4. Heart Failure trends • Burden of heart failure (HF) is increasing - 25 million people affected by HF worldwide - 670,000 new cases each year in US alone • Hospitalizations due to HF increasing • Overall Heart Failure survival has improved over last 2 decades Westaby J Thorac Cardiovasc Surg 2013: 145:24-31
- 5. Heart Failure trends - Australia Chen L, Booley S, Keates AK, Stewart S. Snapshot of heart failure in Australia. May 2017. Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia
- 6. Cardiogenic shock (CS) trends • Prevalence of AMI-CS - increased from 6-7 % to 10-12 % • Mortality from AMI – CS ~ 80% to 40% • AMI-CS • 1 in 3 pts die in hospital • 1 in 5 die within a year • 1 in 3 survivors develop recurrent HF within 1 year Esposito ML and Kapur NK Acute mechanical circulatory support for cardiogenic shock: the “door to support” 2017, (F1000 Faculty Rev):737
- 7. Vicious Cycle of Cardiogenic Shock (CS) Cardiogenic shock Intra cardiac changes Systemic Changes LVEDP LV wall tension Coronary ischemia SV Tissue perfusion Acidemia Contractility
- 8. Progress of Cardiogenic Shock Esposito ML and Kapur NK Acute mechanical circulatory support for cardiogenic shock: the “door to support” 2017, (F1000 Faculty Rev):737
- 9. Types - Which Device? • Acute Heart Failure • IABP • VA ECMO • Percutaneous VAD’s • Temporary LVAD, RVAD, BiVAD • Chronic Heart Failure • Durable LVAD, RVAD, BiVAD • Total Artificial Heart • Bridge to Recovery ( or Decision) • IABP • VA ECMO • Percutaneous VAD’s • Bridge to Transplant • Durable LVAD, RVAD, BiVAD • Total Artificial Heart • Destination Therapy • Durable LVAD, RVAD, BiVAD • Total Artificial Heart
- 11. Devices for acute MCS therapies Esposito ML and Kapur NK Acute mechanical circulatory support for cardiogenic shock: the “door to support” 2017, (F1000 Faculty Rev):737
- 12. Intra Aortic Balloon Counter-pulsation (IABP) • AMI- CS use – controversial – SHOCK II – not supportive • Non AMI-CS – role exists e.g. acute decompensation of chronic HF, cardiac surgical, reversible CS • Adjunct to ECMO – assists with LV decompression
- 13. Percutaneous VADs TandemHeartImpella • Short term use • Only LV support
- 14. Impella • Axial flow pump placed into the LV from fem artery percutaneously • Inflow- LV and outflow -aortic root • 2.5 to 5.0 L /min flows
- 15. TandemHeart • Para-corporeal continuous flow centrifugal pump • Transeptal inflow cannula- LA via femoral vein • 3- 4 L/min flows
- 16. PVADs - Impella and TandemHeart Advantages • Percutaneous placement in cath lab – rapid institution • LV decompression • Rapid restitution of systemic and splanchnic perfusion Limitations • Trans-septal puncture required w TandemHeart • LV support only – no RV support • Patient mobility restricted • Limb ischaemia • Haemolysis • Acquired Von Willebrand reduced platelet aggregation • Bleeding, infection • Cost
- 17. VA (Veno-arterial) ECMO - peripheral
- 18. VA ECMO - Central
- 19. ECMO circuit as temporary VAD
- 20. VA (Veno-arterial) ECMO J.Donald Hill M.D and Maury Bramson BME, Santa Barbara, Ca, 1971 (Courtesy of Robert Bartlett M.D) Cardiohelp- image courtesy Maquet Getinge
- 21. Left ventricular assist device (LVAD) Total artificial heart (TAH) Devices for longer term MCS: BTT/ DT
- 22. Types of Long Term Devices Rigatelli et al, Journal of Geriatric Cardiology (2012) 9: 389-400
- 23. VAD use growing substantially
- 24. 1st Gen. 2nd Gen. 3rd Gen. Ventricular Assist Devices (VADs)
- 25. • Externally placed • Large drive consoles • Pulsatile • Heartmate I, Novacor VADs- 1st Generation
- 26. 1st Gen. 2nd Gen. 3rd Gen. Centrifugal AxialContinuous flow VADs – 2nd Generation
- 27. • Implantable • Continuous flow • Smaller • Electrically driven • Heartmate II, Heartware, Jarvik 2000 VADs- 2nd Generation
- 28. • Completely implantable • Continuous flow- centrifugal • Mechanical wear minimal – magnetic levitation • Heartmate 3, DuraHeart VADs – 3rd Generation
- 29. ‘Mag Lev’
- 30. VADs limitations • Thrombosis • Stroke • Right Heart dysfunction • Bleeding • Infection • Cost
- 31. Early VAD trials REMATCH 2001 – Pulsatile VADs in ESHF pts vs medical Rx improved survival at 1 year HeartMate II trial 2009 – CF axial VAD vs pulsatile VAD improved survival with axial VAD (HMII) at 1 year
- 32. Centrifugal vs Axial ENDURANCE (2015) Axial (HMII) Centrifugal (HVAD) ↓ ↓ Replacement RHF Explant Stroke Urgent Tx Infection OVERALL NON-INFERIOR
- 33. Centrifugal vs Axial MOMENTUM3 • HM II vs.HM3 • HM3 – better at 6 months – re operation and pump malfunction • 2018 HM3 > HMII – improved outcomes at 2 years
- 34. Syncardia >1400 implants Pulsatile pneumatics 2x 70 ml polyurethane ventricles AP chest diameter > 10cms Abiocor Taken off market Carmat Limited success so far TOTAL ARTIFICIAL HEARTS
- 35. Total Artificial Heart (TAH)- Which Patients? End stage heart disease patients with - • Small ventricles (hypertrophic, infiltrative, other restrictive cardiomyopathies) • Massive LV thrombus • Cardiac tumour • Concomitant repair required e.g., post-infarct ventricular septal defects, aortic root/ascending aortic aneurysms, congenital heart disease • Decompensated right heart failure on LVAD support
- 36. RVADs • No customised long term implantable devices for right heart • LVADs modified and implanted on the right side • Temporary RV support with ECMO or temporary VAD configuration using ECMO in patients with LVADs • Percutaneous RVADs - Impella RP and TandemLife Protek Duo
- 37. Impella RP and TandemLife Protek Duo Acute right heart failure following – • Post heart transplant • Post Left ventricular assist device implantation • Inferior /RV MI • Open-heart surgery
- 38. Impella RP • micro-axial pump catheter • IVC to PA • Up to 4.0 L/min flow
- 39. TandemLife Protek Duo • External centrifugal pump • Cannula placed via RIJV • Assists flow from RA to PA • Up to 4.5 L/min flows
- 40. Summary • HF remains a major cause of mortality, morbidity and economic burden • Mortality from CS remains disconcertingly high • Early recognition and management of CS pivotal in limiting death and dysfunction • MCS devices offer a viable option in improving QoL and survival • “Right device at the right time in the right patient” strategy
- 41. Future - Smaller, more efficient VADs, TAHs and PVADs • Heartware MVAD • Cleveland Heart • BivaCor • Procyrion Aortix
- 42. Thank you Acknowledgements • Dr Maneesha Tol • Prof Kiran Shekar • Dr Abhilasha Ahuja • Dr Bruce Thomson
- 43. • Westaby S, Cardiac transplant or rotary blood pump: Contemporary evidence J Thorac Cardiovasc Surg 2013: 145:24-3 • Chen L, Booley S, Keates AK, Stewart S. Snapshot of heart failure in Australia. May 2017. Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia • Esposito ML and Kapur NK Acute mechanical circulatory support for cardiogenic shock: the “door to support” 2017,(F1000 Faculty Rev):737 • Cove and Maclaren Critical care 2010, 14;235 • http://www.abiomed.com/resources • http://www.tandemlife.com/tandemheart-kit -now LivaNova LLC • CentriMag manufactured by Levitronix, now Abbot LLC • SynCardia Systems, LLC
Editor's Notes
- HF is a global pandemic. It is indeed a gathering storm. Number of HF pts will double in next 2 decades.10% HF pts have advanced stage D disease On a promising note the survival in this group of pts has improved over the last 2 decades. This is due to extensive institution of anti-HF therapy, use of AICDs/ CRT and mx in specialised HF units
- The HF trends in Australia mirror those across the globe, with > 65000 new pts each year. The burden to the health budget is 2 billion dollars in hospitalization alone in these pts each year.
- The incidence of CS from all causes has reduced in the last 2-3 decades, however that related to AMI has plateaued. CS related to AMI had a disconcertingly high mortality around ~80%; It has halved to about 40% in recent times due to widespread use of revascularisation strategies. 1nd 3 pts of this group die in hospital; 1 in 5 within 1 yr and 1 in 3 of survivors have recurrent HF within a yer ; very sobering numbers , indeed.
- Cardiogenic shock, as we know, causes systemic changes due to hypoperfusion leading to acidemia and Intracardiac changes causing LV distension and impaired coronary perfusion.; both these conditions worsen contractility and in turn cardiogenic shock
- The hemodynamic pb transitions to a hemometabolic pb persistent impaired tissue perfusion, hyperlactatemia and multi-organ dysfn ; whereupon the changes may not be entirely reversible. Treatment of CS must therefore focus on early identification and use a multipronged goal directed approach. Inotropes may help with some of these objectives but that comes at a cost of increased cardiac workload and systemic + splanchnic vaso-constriction with their consequences. MCS devices can provide this support – without increasing the cardiac workload and by restoring the myocardial O2 supply/ demand balance.
- So which device is suitable in which situations? Very simply, in acutely and severely unwell patients with early end organ dysfn - temp short term support can be provided IABPs, Pvads , VA ecmo, They form a bridge to recovery or sometimes, decision. On the other hand, in patients who are declining slowly over days to weeks – long term devices such as durable LVADs , RVADs +- Bi VADs or TAHs are more suitable. These provide a bridge to transplant in transplant eligible pts or occasionally DT.
- The timing of MCS use is crucial. too early and the pt is exposed unnecessary risks of intervention and its cx; too late and the benefit desirable from the use of the device may be lost. The INTERMACS registry has devised clinical profiles that assist clinicians with determining the timing of MCS use. For e.g. level 1 pts are highly unsuitable for long term devices. They must first be stabilised on short term devices. Level 2,3 and 4 pts may be more suited to have longer term devices such as VADs
- These are the devices commonly used to rescue patients who are deteriorating more rapidly. IABPs have a limited role; increasingly VA ECMO or PVADs such as the Impella are being used in this setting.
- Intra-aortic balloons have been used for sometime in patients with acute cardiac dysfunction. Their role in CS related to AMIs has diminished after the SHOCK II trial ; however they still have a role in other settings such as acute decompensation of a CMP pt or in cardiac surgical setting. They also provide an option for LV decompression esp in concert with VA ECMO.
- Next are the percutaneous VADS. The Impella or the TandemHeart are 2 of the devices that are approved for use for < 5 days by the FDA for LV support , in addition to their use peri procedurally. They provide LV support only . The RH and lungs must have reasonable fn.
- The first of these is the Impella. This device consists of an axial flow pump catheter placed into the LV from the femoral artery percutaneously. The inflow in the LV sucks in blood and pushes it into the aortic root / asc aorta at 2.5- 5 L /min based on the size of the cath used. They are available in Australia and we have used in half a dozen situations. This device has FDA approval in the USA for peri-procedural support for high risk PCIs and as LVAS in acute situations for up to 5 days. There are reports of use for longer periods 2-3 weeks though apparently without any major adverse events. That brings us to the other PVAD used in similar situations….
- The next one is the Tandem heart, which is an extracorporeal continuous flow centrifugal pump. It consists of a cannula placed from the femoral vein into the RA and then LA via a transeptal puncture. The blood is returned from the pump into the femoral artery at flows of 3-4L /min. Lets look at some of the adv and disadv of PVADs.
- PVADs can be relatively rapidly instituted. They can be placed percutaneously under fluoroscopy, Provides reasonably efficient LV decompression and restitution of systemic and coronary perfusion thereby helping with correction of organ dysfn. The TandemHeart does require technical expertise for a transeptal placement. Also, given that they are decent sized cannulae placed via femoral vessels usually – mobility is restricted. Haemolysis and limb ischaemia remain issues that must be watched. And of course, the cost is not insignificant. Next we come to a circulatory support strategy that is gaining momentum.
- Peripheral VA ECMO also provides a realistic option for acutely failing hearts. P VA ECMO can be rapidly instituted by the bedside including in arrest situations. VA ECMO also provides improved flows and systemic perfusion thereby reversing organ dysfn.
- Central VA ECMO provides similar support in the CS context. It shares similar risk profile as PVADs due to use of large cannulae in fem vessels; however with technological advancements in cannulae, circuits and pumps, the risks of institution and management are reducing. Limb ischemia is usually averted by placement of a backflow cannula with the arterial cannula. Bleeding and thrombosis risk would be somewhat similar across all acute MCS devices.
- Another emerging role for VA ECMO is as that of a temporary VAD. In this case, Dacron grafts are placed on major vessels and chambers of heart depending on the support desirable. Cannulae are then placed into these grafts and are then exteriorised and connected to pump consoles. They can therefore provide R sided or L sided or even biventricular support for intermediate periods for 4-5 few weeks. This strategy enables pts to be mobilised whilst still receiving circulatory support and maintain their condition so that they remain eligible for transplants.
- The newer ECMO have certainly evolved to be more compact and portable w more biocompatible circuits to minimise cx. As more and more centres acquire competencies and experience in the use of ECMO, it must certainly remain in the arsenal for acute MCS strategy.
- That brings us to devices that are available for chronic heart failure. These are devices that are used in the setting of LV support towards transplantation and occasionally as destination therapy. We have LVADs and TAHs. VADs have been primarily devised for L heart support. The devices I will discuss shortly are LVADs.
- Whilst there has been some development in the VAD arena, the same has not happened with total heart devices.
- VAD use worldwide growing exponentially; with huge improvements in pump design and a better understanding of the physiological changes associated with their use including hematological milieu, VADs are able to provide support for longer periods with fewer complications.
- VAD design and mechanics have evolved tremendously over the last 4 decades to the point that the current 3rd generation devices are smaller, lighter and highly efficient.
- 1st generation devices were bulkier pumps, placed outside the body , attached to washing machine sized drive consoles. More extensive surgical techniques were required for placement. These were volume displacement pumps. These pumps include a pusher plate in the pump housing with a motor, which pushed the blood coming in mechanically and pushed it towards the outflow. This generated a ‘ pulse’. They could generate up to 8 lpm flows.
- The 2nd generation VADs are more compact and implantable. They were continuous flow axial or centrifugal pumps.
- Second generation VADs are smaller and implanted in the pre-peritoneal space. They have smaller, more portable drive consoles and therefore pts have better mobility. Surgical implantation was relatively easier. The axial flow pumps use a corkscrew impeller with motor in the pump housing. Blood coming into the pump is propelled via turbine mechanism towards the outflow , parallel to the rotor quite smoothly and continuously. They generate up to 10 lpm flows. They do not generate a pulse. They were used in the next gen VADs like HMII
- The 3rd generation VADs are smaller still; they are implanted in the pericardium. The magnetic levitation mechanism reduces mechanical injury to blood cells considerably. In these pumps, the blood coming in via inflow channels is smoothly propelled in a circumferential manner by the cone shaped rotors. These devices also do not generate a pulse. The newer and more evolved version of the continuous flow centrifugal pumps have a free floating impeller that is magnetically levitated (elevated) in the pump housing. Current passing through the magnets on the impeller causes it to spin. And the rotating vanes then propel the incoming blood from the centre to the outer rim of the impeller very seamlessly. A simplistic analogy would be the maglev or bullet trains in Japan.
- These trains work on similar principles aimed at contactless motion at very high speeds.
- There are certain cx associated with Vads. In particular, thrombosis, stroke and RHF – whilst these have reduced with each gen, they remain an issue, nonetheless. The cost is not small.
- There is some evidence for LVAD use . Initially , compared to medical therapy , then comparison between pulsatile and axial -1st and 2nd gen vads REMATCH 2001 – Pulsatile VADs in ESHF pts vs medical Rx improved survival at 1 year HeartMate II trial 2009 – CF axial VAD vs pulsatile VAD improved survival with HMII at 1 year
- Then came 2nd vs 3 rd gen vads Endurance trial in 2015 – largest trial for long term use of LVAD as destination therapy – 55 % pts had stroke free survival at 2 years Cf control HMII; ENDURANCE supplemental trial in 2017 demonstrated that improved BP control resulted in reduction in stroke incidence by 24% cf previous study; and survival at 12 months free from disabling stroke, death, device malfunction requiring exchange, removal of the device or urgent transplant - HVAD was better than HMII
- And finally the latest 3rd gen Vads for upto 2 yrs Momentum 3 investigators first showed that CF centrifugal were better than CF axial ( HM 3 vs HM II) at 6 months – less reop and pump malfn Momentum 3 investigators further showed that at 2 yrs HM3 was better than HMII wrt survival free from disabling stroke or reop or malfn
- Total artificial hearts are implantable cardiac assist devices that essentially replace the ventricles and provide complete bivent support. They are capable of generating 5-10 lpm flows. Most devices on market are pulsatile first generation devices. The Syncardia Cardiowest is the only 2nd gen device. These devices need considerable surgical expertise for implantation. The syncardia consists of 2x 70 ml polyurethane ventricles; there are 2 mechanical single leaflet tilting disc valves in each chamber to regulate direction of flow. It is pneumatically actuated via drive lines percutaneously attached to an external pump. Given the larger size of these devices the AP chest diam in the pt has to be at least >= 10 cms While no head-to-head prospective randomized controlled trials have compared these two types of mechanical circulatory support, one small retrospective study showed no difference in mortality for patients implanted with a TAH compared with BiVADs (20). Conversely, although the number of implants remains too small to draw conclusions, analysis of the INTERMACS registry has suggested improved short term survival of patients implanted with a TAH compared to BiVADs (3).
- Indications for TAHs at this stage includes transplant eligible patients with biventricular dysfunction deemed not suitable for LVAD. – such as pts with small ventricles, or those w LV thrombus or tumors that preclude LVAD implantation. ; or they could be patients who require concomitant sx repair for their CHD or aortic dysfn where again LVAD implantation is unsuitable. Lastly they may be pts w refractory RHF on LVAD support that does not improve with therapy.
- Finally coming to RVADs. Firstly there are no customised implantable devices for the R side; LVADS have been modified and implanted on the R side. Temporary RV support can also be provided with ECMO or using temporary ‘VAD configuration’ using ECMO, in patients with LVADs There is some hope however with development of percutaneous RVADS – 2 of these devices are gaining some attention. Percutaneous RVADs - Impella RP and TandemLife Protek Duo
- The impella RP is available for use in Australia in conditions where RH needs support e.g. after tx, or LVAD implantation or cardiac sx
- This is the Impella for the R side – it is a micro-axial pump catheter, percutaneously inserted via the femoral vein ; It assists flow from an inlet in IVC to the outlet at the tip, in the PA. It is available in Australia and we have used in a patient in context of RV dysfn associated w LVAD implantation
- And the next one is the Tandem Life Protek Duo. This is an extracorporeal centrifugal pump; where a dual lumen cannula is placed via R IJV and it takes blood from the IVC and propels it via the pump into the PA’ t can generate 4- 4.5L /min flows. Clearly some expertise is reqd for placement of both devices – usually under fluoroscopy and Echo guidance; frequent echo assessments will be reqd to ensure adequate position whilst they are in use.
- The future holds some exciting prospects. Next generations of VADs are becoming much smaller. TAHs will follow the same path with revolutionary devices under development. The Procyrion device has been successfully deployed, tested, and retrieved in vivo in large-animal heart failure models (n=10) and human cadaver studies across multiple investigator sites. Data from the large animal experiments confirms reduced cardiac load and cardiac oxygen consumption, improved ejection fraction and cardiac output, and increased renal perfusion and urine output. A subset of these results has been published in a peer-reviewed journal (ASAIO J. 2013 May-Jun;59(3): 240-5).