SUMMARY OF SAFETY AND PROBABLE BENEFIT

For The AbioCorÔ Replacement Heart

 

 

1.      General Information

 

Device Generic Name:                                               Implantable Replacement Heart

 

Device Trade Name:                                                   AbioCor Replacement Heart

 

Applicant’s Name and Address                                  ABIOMED, Inc.

                                                                                    22 Cherry Hill Drive

                                                                                    Danvers, MA  01923

 

Humanitarian Device Exemption Number:                 H040006

 

Date of Panel Recommendation:                               June 23, 2005

 

Date of Good Manufacturing Practices Inspection:   

 

Date of Notice to Applicant:

 

 

2.      Indications for Use

 

The AbioCor is indicated for use in severe end stage heart disease patients who

·        are less than 75 years old,

·        are not transplant candidates at the time of assessment,

·        require multiple inotropic support,

·        are in biventricular failure not treatable by LVAD destination therapy,

·        are not weanable from biventricular support if on such support and not awaiting transplantation.

 

3.  Contraindications

 

Contraindications include patients

·  with other irreversible end organ functions that would compromise survival,

·  with inadequate psychosocial support,

·  in whom preoperative noninvasive anatomical assessment reveals     inadequate fit.

 

4.      Warnings and Precautions

 

There are a few basic warnings and cautions:

·  Stay clear of MRI or high magnetic field environment

·  Do not place TET near metal elements

·  Internal low battery alarm requires immediate eTET attachment

·  Low flow alarm requires clinical attention

·  eTET decoupling alarm requires need to check eTET coupling

 

Other detailed warnings and cautions are given in the Instructions for Use.

 

5.      Device Description

 

The AbioCor is a pulsatile electrohydraulic implantable replacement heart

capable of delivering up to 8 L/min over a broad range of physiologic pressures. 

System control is achieved on a beat-by-beat basis targeting a constant stroke volume to insure repeated full filling and full ejection.

 

Except for the inflow cuffs and the outflow graft connectors, which are constructed from standard medical grade velour patches and grafts, the blood contacting components of the AbioCor are made from Angioflex, a polyether-urethane.  Titanium is used as the casing material to avoid corrosion.  Medical grade epoxy is used to provide rigidity to nonmoving portions of the blood pumps.  The flow paths through the pumps are designed to avoid regions of stasis.  The inflow and outflow valves are designed to maintain proper washout of the leaflets.  With the use of polyurethane valves, the AbioCor ventricles are quiet in operation.

 

The hydraulic system that powers the device consists of a miniature centrifugal pump and a reciprocating switching valve which reverses the direction of the fluid flow on every beat.  The hydraulic fluid actuating the flexing membranes, separating the fluid from the blood, simultaneously effects the filling of blood on one side while ejecting blood on the other side.  Systole on the left side is diastole on the right side and vice versa.

 

The AbioCor accommodates the difference in outputs required between the left and the right ventricles.  Physiologic shunts exist which normally require higher left side outputs compared to the right side.  In the AbioCor, a hydraulic balance chamber is used to shunt the right chamber volume, thus reducing the right side output relative to the left side.  This feature allows the maintenance of physiologic left atrial pressure.

 

Implantation of the AbioCor is achieved while on cardiopulmonary bypass (CPB).  The diseased ventricles are excised and cuffs are sewn to the two atrial remnants.  Aortic and pulmonary grafts are sewn in place.  The cuffs and grafts have mating connectors to the inflow and outflow ports of the device facilitating a snap on coupling.  De-airing completes the transition from CPB to the AbioCor.

 

The system can be divided into 3 subsystems: the Implantable, the External Console, and the Patient Carried Electronics (PCE) Subsystems.  The general description of their respective functions follows.

 

5.1 The Implantable Subsystem

 

The Implantable Subsystem consists of all of the components that are required to be implanted for normal operation of the AbioCor®.  The main components of this subsystem are described below.

 

5.1.1       Thoracic Unit (TU)

 

The thoracic unit (TU) converts the electrical power into blood motion to support the circulatory system of the patient.  The TU is implanted in the space vacated after excising the native ventricles.  The TU alternately ejects blood into the systemic and pulmonary circulation.

 

5.1.2       Implantable Controller

 

The Implantable Controller is the brain of the entire system.  It is microprocessor based and provides control and monitoring of the TU.  It also has the capability to receive and transmit information to the external systems via a radio frequency (RF) communication link.

 

5.1.3       Implantable Battery

 

The Implantable Battery is a rechargeable, lithium ion based power source that can maintain normal operation of the implantable system in the absence of an external power source for more than 30 minutes.

 

5.1.4       Implantable Transcutaneous Energy Transmission Coil (iTET)

 

The Implantable Transcutaneous Energy Transmission Coil (iTET) receives power inductively from an external power source and converts it into DC to power the implantable subsystem.

 

5.1.5   Implantable Cable

 

The Implantable Cable connects the various components of the Implantable Subsystem together.  The cable also has an integral antenna that is used for the RF communications.

 

5.2   External Subsystem

 

The External Subsystem consists of all of the components that are required to support normal operation of the AbioCor® for implantation, ICU recovery, patient ambulation and out-of hospital use.  The main components of this subsystem are described below.

 

5.2.1       Console

 

The Console allows monitoring primarily of the Implantable Subsystem parameters and alarms as well as the ability to make changes in system run conditions.  There are several modes of access for system operation intended to insure patient safety.  For instance, the console can stop operation of the TU only during implantation.  This function, essential during de-airing of the TU in the operating room, is not accessible in any other functional mode.  In the home screen mode, the display is significantly simplified to avoid information overload, or potentially harmful actions by the user. 

 

The Console also has drive circuitry to power the External Transcutaneous Energy Transmission Coil (eTET).

 

5.2.1.1            External Transcutaneous Energy Transmission Coil (eTET)

 

The eTET allows delivery of energy to the iTET.  There are two different eTET cable lengths to accommodate various use environments.  A Duoderm based Velcro patch is used to anchor the eTET at the skin region overlying the iTET.

 

5.2.1.2            Radio Frequency Communications Assembly (RF Comm)

 

The Radio Frequency Communications Assembly (RF Comm) gives the console the wireless communication bi-directionally between the external and the Implantable Subsystems.

 

5.2.2       Patient Carried Electronics (PCE) Subsystem

 

The Patient Carried Electronics (PCE) Subsystem consists of all of the components that are required to support normal operation of the AbioCor® for periods of full patient ambulation.  It supplies power to the internal system via the eTET.  The main components of this subsystem are described below.

 

5.2.2.1            PCE TET Driver

 

The lightweight PCE TET Driver has the circuitries to drive the eTET and to enunciate simple alarms such as low battery, eTET decoupling, excess PCE temperature, and a general Implantable Subsystem alarm.

 

5.2.2.2            External Transcutaneous Energy Transmission (eTET) Coil

 

The PCE uses the same eTET coils as that used for the external console.

 

 

 

5.2.2.3            PCE Power and Bag

 

The PCE Batteries are the primary power source for the PCE TET Driver.  The PCE Batteries are discharged in pairs.  Two sets of batteries are provided to allow for appropriate backup.  The battery sets and the eTET are housed in a PCE bag specifically designed for portability.

 

5.2.3       Handheld Alarm Monitor

 

The Handheld Alarm Monitor allows the user to find out specific details regarding Implantable Subsystem alarms that are enunciated on the PCE TET Driver.  This device allows clearing of the alarm when the condition has resolved.   This unit relieves the patient from needing to be near the console to have full diagnostic capability.  This unit does not provide control of the internal system, that function requires the console.

 

5.2.4  PCE AC Converter

 

The PCE AC Converter is an alternate power source for the PCE TET Driver.  It permits a patient while stationary to be able to use the PCE TET Driver for an unrestricted amount of time without the need to actively manage PCE Batteries.

 

5.2.5       PCE Battery Charger

 

The PCE Battery Charger is a 10-bay charger that allows the patient to charge up to 5 sets of PCE Batteries.  It also provides diagnostic information on the state of charge of the PCE Batteries.

 

5.3       Implantation Accessories

 

Accessories to facilitate implantation include specially designed wrenches to tighten or loosen electrical connectors between implantable components, tools to connect the device to the atrial cuffs and arterial grafts, instruments to check the integrity of anastomoses, dummy models of electronic packs for pocket sizing, and dummy thoracic unit for sizing graft lengths needed for the anastomoses.

 

5.4       Safety Elements

 

Many safety elements are incorporated into the AbioCor system including:

 

            ·  24x7 clinical and technical support

            ·  complete backup system in each hospital

            ·  backup external Patient Carried Electronics for home use

            ·  Multiple alarm paths for low internal battery, low flow conditions

            ·  TET self shut down under overload condition

            ·  No skin penetration for external power transfer

            ·  Internal battery capacity of greater than 30 minutes

 

 

 

6.      Alternative Practices and Procedures

 

There are no other devices on the market that address the same patient population as the AbioCor.  None of the devices in clinical use today, BVS5000, AB5000, Heartmate, Thoratec PVAD, Novacor, or CardioWest can adequately support those patients that are AbioCor candidates. Neither can devices on the horizon, such as the Lion Heart, and a class of rotary pumps in clinical trials address the patient population addressed by the AbioCor.

 

7.      Marketing History

 

The AbioCor has never been marketed in or outside the United States.

 

8.      Potential Adverse Events

 

Based on the experience of the AbioCor initial clinical, the following adverse events can potentially occur in patients implanted with the AbioCor:

·  Bleeding

·  Reoperation

·  Hemolysis

·  Infection (all causes)

·  Renal dysfunction

·  Hepatic dysfunction

·  Respiratory dysfunction

·  Neurologic dysfunction

·  Thromboembolism

·  Mechanical failure

·  Electrical failure

·  Psychiatric event

·     Stroke

·     Death

 

9.      Summary of Preclinical Studies

 

Preclinical testing consisted of bench testing and animal testing.

 

9.1   Benching Testing

 

Benching testing consisted of performance, safety, and reliability testing.

 

 

9.1.1       In Vitro Testing

 

Performance testing was conducted over a physiologic range between 60 and 120 mmHg for AOP, 10-40 mmHg for PAP, 3-25 mmHg for LAP, 3-25 mmHg for RAP, and a shunt flow (left minus right flow) of 0 to 10 % of cardiac output.  Within these ranges, the system is capable of providing 4 to 8 L/min of cardiac output.  The TET system is capable of supporting system operation with radial and/or axial misalignments of ± 0.5”.  The internal battery is capable of supporting a 60 minute untethered operational at a cardiac output of 6 L/min and 100 mmHg systemic afterload.  The external Patient Carried Electronics can provide 60 minutes of operation from one set of batteries.  The internal-external RF communication module functions to provide alarms and inputs to the internal system.  All input requirements were tested and verified.

 

9.1.2       Safety Testing

 

The AbioCor system passed all Electromagnetic Interference and Electromagnetic Compatibility requirements based on FCC CFR 47 Parts 15 and 18, CISPR11, and IEC 60601-1-2 for intentional and unintentional radiators.  All implanted components of the AbioCor were tested for Biocompatibility to EN ISO 10993-1:1997.  The Implanted Components are ETO sterilized.  The process was verified according to ANSI/AAMI/ISO 11135-1994.  Sterility shelf life has been verified for 15 months.  Immunity to shock was tested according to NTIS/ECRI PB296-892 and vibration according to RTCA/DO-160C.  Packaging integrity for various parts was tested to ISTA 3C.  Components were subjected to fluid ingress testing (EN 60529).  The AbioCor system satisfied additional electrical and mechanical safety requirements of UL 2601.

 

9.1.3       Reliability

 

Twenty-five implantable subsystems have been placed on reliability testing.  Failure times have ranged between 8.2 to 40.5 months.  The average runtime time is 18.8 months (± 11.5).  System reliability is determined to be greater than 80% at a confidence level of 80% for a one-year operation.  Three major failure modes were observed: bearing, membrane wear, and fluid ingress.  Two of the three failure modes have been observed clinically, a bearing failure at 5 months and a membrane wear at 17 months.  Fluid ingress due to a breach of system hermiticity has not been encountered.  A needle puncture of a cable sheath was encountered and the cable was surgically exchanged without patient compromise.

 

Backup consoles are required in the hospital environment and backup PCEs and Handheld Monitors are required for discharged patients.

 

 

 

9.2   Animal Testing

 

Fourteen studies completed the 30-day duration. The AbioCor was implanted in calves weighing 90 to 120 kg.  The results of the studies indicated that after the one-month implants, blood pumps and end organs were generally clean without evidence of thromboembolic problems.  Based on the animal studies, no thermal injury problem was anticipated in the operation of the Transcutaneous Energy Transmission system (TET) in humans, and none has been encountered.

 

10.   Summary of Clinical Study

 

The goal of this initial trial is to assess the safety and potential efficacy of the fully implantable AbioCor replacement heart as a potential therapy for those cardiac patients whose therapeutic options have been exhausted. 

 

 

10.1 Objectives

 

For those patients implanted with the AbioCor, the initial evaluation of safety and potential efficacy is to be assessed at 60 days post-implantation.  For those who recover sufficiently on the AbioCor, heart transplantation could be reassessed after the initial 60-day period.  For those not eligible for transplantation, patients would be supported for life on the AbioCor.

 

The primary endpoint of this study is the absence of significant neurologic deficit at 60 days post implant.

 

10.2  Methods

 

Candidate selection proceeded in two stages, a screening stage and an implant consent stage.  During the screening stage, a basic medical assessment is performed.  This assessment involves the determination of the severity of a candidate’s heart failure and the potential fit of the device in the patient’s thoracic cavity.

 

Candidates eligible for the trial are those who are not eligible for heart transplantation based on the center’s criteria at the time of screening, are in biventricular failure not treatable with implantable LVAD, and are under optimal medical management yet unable to sustain continued life.  Alternatively, a patient who could not be weaned from biventricular cardiac support and is not a transplant candidate is eligible for the AbioCor.  Patients with irreversible end-organ failure, and inadequate psychosocial support are excluded from the trial.

 

Candidates are excluded if the prognosis for survival is greater than 30% within the next 30 days.  The prognosis of survival is based on a combination of hemodynamic status, cardiac conditions and end organ status.   

 

A screening tool is used to assess the potential for anatomic fit.  MRI or CT scans from candidates are used to reconstruct the internal chest dimensions and the anatomy of the patient.  A virtual surgery is performed to remove the ventricles and place the AbioCor in the vacated space.  Three critical observations are made to insure fit. The AbioCor must stay within the rib cage, while not interfering with the left bronchus and the left pulmonary veins.

 

If a candidate passes all the established criteria, a patient advocate would participate in the informed consent process.  Although direct patient consent is preferred, in cases where this is not practical, such as AMI shock patients, a legal surrogate can sign on the patient’s behalf.

 

10.3    Description of Patients

 

Fourteen patients have been enrolled in the trial.  All candidates were males due primarily to fit constraints.  Table 1 is a summary of patient demographics.  The mean age of this initial cohort is 67 ± 7.9 ranging between 51 and 79 years old.  The percentage of patients excluded from transplant due to age was 43% (6/14), to irreversible pulmonary hypertension was 29% (4/14), to malignancy was 14% (2/14), and to multiple factors, such as diabetes, neuropathy, renal dysfunction, hepatic dysfunction, etc was 14% (2/14).  The BSA, body weights, and heights are also given in the table.

 

Table 1   Patient Demographics (n=14)

 

 

Average

Stdev

Min

Max

Age      yo

67

7.9

51

79

BSA     M2

1.97

0.15

1.72

2.24

Height  cm

180.

6.2

170.2

189

Weight  kg

78.1

10.9

60.8

96.3

 

The preoperative cardiac conditions and comorbidities of patients are summarized in Table 2.  All patients were in NY Class IV heart failure primarily of ischemic origin (12/14) with two being idiopathic.  All patients were bedbound.  A majority of the patients had prior cardiac operations, pacer or AICD implanted, and/or required IABP support.  Pulmonary hypertension and renal dysfunction were the two primary comorbidities.

 

 

 

 

 

 

 

 

Table 2   Pre-Operative Conditions

 

Pre-implant Cardiac Condition or Comorbidity

# of Patients with Condition (n=14)

Re-op

10

Pacer/AICD

10

IABP

10

Ventilator Support

4

Pulmonary Hypertension

8

Renal Dysfunction

9

Liver Dysfunction

4

Diabetes

6

 

Pre-operative hemodynamics is summarized in Table 3.  All data were collected within two weeks of implantation.  Ten of the fourteen candidates required IABP support.  In addition, high levels of inotropic support averaging 2.5 ± 1.0 drug types were needed to maintain marginal cardiac output and systemic pressure.  Mean systemic pressure was 75 ± 9 mmHg.  The mean cardiac index was 2.1 ± 0.5 L/min·M2 under such maximal inotropic support concurrent with counterpulsation support.  Table 4 shows the mean dosages for the inotropes used.  The dosages were in the medium to high range.  Wedge pressure was elevated (LAP = 20 ± 6 mmHg) characteristic of these end stage heart failure patients.  The central venous pressure (CVP = 13 ± 7 mmHg) spanned a broad range (2-24 mmHg) reflecting patients being actively volume managed by infusion, diuresis, and vasoactive drugs.  The systemic vascular resistance (SVR) was 1231 ± 349 dyne·sec/cm5 spanning a broader range than normal indicative of hypotensive to hypertensive conditions of multiple etiologies.  The pulmonary vascular resistance (PVR) was 305 ± 106 and nearly three to four times higher than normal reflecting the pulmonary hypertensive condition of the patients.

 

Table 3   Pre-operative Hemodynamics

 

 

Average

Stdev

N

PAP        mmHg

34

6.6

14

AoP        mmHg

74

6

14

CVP        mmHg

11

6.4

14

PCWP    mmHg

19.9

5.5

14

Cardiac Index  L/min-M2

2.1

0.5

14

Cardiac Output L/min

4.3

1.2

14

Ejection Fraction %

18.6

3.5

14

PVR  

dynes-sec/cm5

305

107

12

SVR

dynes-sec/cm5

1231

349

14

 

 

Table 4   Pre-operative Inotrope Dosages (n=14)

 

Inotrope

Mean Dosage

Standard Deviation

Number of Patients

Dobutamine - mg/kg/min

7.89

4.08

8

Dopamine -    mg/kg/min

9.16

10.53

6

Primacor -      mg/kg/min

0.43

0.24

12

Epinephrine - mg/min

3.3

--

1

Levophed -     mg/min

9.11

--

1

Digoxin –        mg/day

0.14

0.05

7

 

 

Pre-operative blood chemistry is summarized in Table 5.  The low albumin level (2.8 ± 0.7 g/dl) is indicative of cachexia common to severe end stage heart failure patients.  The low sodium level (132 ± 6 meq/L) is another end of life indicator.  The elevated creatinine (1.7 ± 0.7 mg/dl) and BUN (45 ±  30 mg/dl) levels reflect renal dysfunction.  Similarly, total bilirubin (1.7 ± 1.8 mg/dl), AST (73 ± 126 mg/dl), and ALT (64 ± 100 mg/dl) reflect liver dysfunction common to these patients.

 

                        Table 5  Pre-operative Blood Chemistry

 

 

Average

Stdev

Min

Max

N

Na       mEq/L

131.7

6.4

120

141

14

Albumin  g/dl

2.8

0.7

2

3.9

11

Creat      mg/dl

1.7

0.7

1

3

14

BUN       mg/dl

45.1

30.2

16

110

14

Tbil         mg/dl

1.7

1.8

0.5

7.4

14

ALT        mg/dl

63.5

100.2

3

333

14

AST       mg/dl

73.1

125.8

10

491

14

Glucose mg/dl

116.7

39.5

59

186

14

 

All patients entered into the trial met the inclusion criterion of biventricular failure as the basis for exclusion from potential implantable LVAD support.  In addition, all patients met the exclusion criterion of less than 70% probability of dying within 30 days based on the AbioScore or AMI Shock Index.  The inotrope requirements of AbioCor patients averaged 2.5 inotropes, suggesting that based solely on inotropic needs, mortality would have been high, averaging around 60% within 30 days.  Accounting for additional comorbid conditions, the mortality would be further increased as is anticipated of the AbioCor candidates. 

 

Figure 1 illustrates the survival probability of our study population compared with those recruited in the REMATCH trial(3.2).  The Kaplan Meier plot for the REMATCH group is based on the control group from that trial.  The plot for the AbioCor group was based on patients that met all medical inclusion and exclusion criteria but did not enter the trial due either to identifiable anatomic fit problem or failure to consent.  These patients were followed to 60 days.  The median survival of the REMATCH patients was around five months while that for

the AbioCor candidates were two weeks.  This comparison illustrates the very much sicker patient population recruited for the AbioCor compared to any other patient cohort.  Due to the small sample size, no statistical significance is implied.




Figure 1   Survival Plots of REMATCH and AbioCor Reference                                                            Candidates

 

 

10.4      Results

 

Twelve patients survived surgery.  For these twelve patients, ten survived beyond the 60-day endpoint for evaluation in this initial trial.  Support for two patients was withdrawn prior to 60 days at the request of the respective family. For the ten patients that survived beyond 60 days, seven reached 60 days with no neurologic incidents, the principal end point of the trial.  One did not recover from the incident, while the other two patients recovered from their respective incident.  The mean support duration for the ten patients that reached 60 days of support is 6.0 months (± 4.3).

 

Of the fourteen patients, 86% (12/14) survived surgery.  This rate is not unlike that of transplant acute survival rate.  For those that survived surgery, 83% (10/12) survived beyond 60 days, twice the expected survival duration for these patients. 

 

 

 

 

10.4.1     Adverse Events

 

Recovery has been a lengthy process for these patients.  Table 6 lists the major adverse event types experienced by the patients during the course of recovery.  Event rates are given in reported incidents per patient per month.  The CVA category includes embolic strokes confirmed by CT scans.  The TIA category includes events that were transient or showed no clinical evidence of embolic strokes.  There were many surgical bleeding events, such as tamponade, occurring during the first few weeks post operatively.  The leading event rates were bleeding, infection unrelated to the device, and respiratory complications.  These were followed by neurologic, renal, and hepatic complications.

 

Table 6.  Adverse Event Rate (n=12)

 

Event Type

Event Rate  (per patient·month)

Total Number of Events

Event Rate – Approved Devices

CVA – CT confirmed

0.22

14

0.01-0.28

TIA or non-clinical

0.09

6

0.01-0.2

Non-surgical bleeding

0.41

26

0.04-0.27

Surgical bleeding

-

42

-

Sepsis

0.03

2

0.03-0.17

Infection

0.52

33

0.02-0.24

Hepatic

0.11

7

0.02-0.26

Renal

0.13

8

0.02-0.16

 

The ranges of reported adverse event rates for approved cardiac support devices are also listed in Table 6.  Patients supported by these devices were mostly for bridge to transplant indication requiring the patients to be in better condition to be qualified for transplantation.  In addition, the results of these devices represent recent experiences following decades of learning and improvements in clinical use.  For the AbioCor, this represents the first clinical experience. 

 

Only two adverse event types appear to be outside the reported range for other devices.  These are bleeding and infection.  The propensity for bleeding has been high for AbioCor patients due to comorbidities.  This has been the reason why 10 of 12 patients could not tolerate the recommended level of anticoagulation (INR>2.5 or PTT>50 sec) more than 60% of the time, and of these 10 patients, seven of them could not tolerate more than 80% of the time.  The higher infection rate is due to the long hospital stay due to the debilitated condition of the patients coming into the trial.  Long hospital stay exposes patients to higher risk of infection.

 

 Despite the sicker condition of AbioCor patients, renal and hepatic complications did not appear to be more pronounced than the mature devices.  Septic event rate experienced with the AbioCor was at the low end of those of established devices.  The fully implantable AbioCor has a beneficial feature in not leading to septic conditions despite the higher observed infection rate.  There were two septic events associated with the AbioCor patients, one as a sequella to an abdominal massive bleeding episode.  This episode was caused by a femoral vein puncture during a dialysis catheter exchange.  The second event occurred in a patient whose suture line did not heal following surgery.  Although the infection rate was high, none of the incidents were related to device infection.

 

Following the reintroduction of the modified caged cuff as an option, three patients were implanted with the AbioCor using caged cuffs sewn to atrial tissue avoiding tissue contact of the cages.  Two patients have not suffered CVA events.  One patient has had an event attributable to the inability to anticoagulate.

 

10.4.2.1         Device Related Adverse Events

 

There were two device related patient deaths.  A patient passed away due to a membrane wear out at 17 months, an anticipated wear out mode at operating times of around one and one-half years.  The patient declined the option for a device replacement.  A second patient  died due to a motor bearing stoppage at 4.8 months.  The cause was traced to a combination of factors leading to system operation outside of the system design.  Corrective actions have been implemented to avoid such combination of circumstances.  The system has been tested to an 80% reliability at an 80% confidence level for a 12 month operation.  Excluding the anticipated wearout at 17 months, the cumulative clinical runtime was ~ 47 device-months.  The 4.8 months to failure of the one device represented an overall probability of survival to 12 months of ~ 85% (1- (12-4.8)/47) consistent with our demonstrated reliability of 80%.

           

10.4.2   Outcome

 

For AbioCor patients, the majority of them lived or will live out the remaining portions of their lives on the device.  In this initial trial, transplantation was considered an option following AbioCor support provided patient condition has improved to a level that transplantation may be considered.  None of the candidates enrolled in the trial had potentially reversible contraindications to transplantation to be considered for this treatment in the future.  There were two operative deaths.  Support to five patients was withdrawn secondary to CVA events.  There were two device failures.  Four patients died of MOF or sepsis, unrelated to the device.  Support was withdrawn in one patient based on family wishes.

 

 

 

 

10.4.3       Patient Activity

 

 Due to the preexisting debilitated state of the patients coming into the trial, time to recovery has been long.  There have been a total of ~50 in-hospital excursions, ~50 PCE uses, and ~30 out-of hospital excursions.  Out-of-hospital excursions included normal activities such as attending sports events, religious services, shows, eating in restaurants, visiting parks, etc.

 

Two patients were discharged from the hospital.  One was discharged to home for nine months.  Six patients lived to see their next birthday.  Two lived to enjoy anniversaries.  One patient lived to welcome the first member of the fourth family generation.  The trial to date has demonstrated that the AbioCor can restore quality life to the recipients. 

 

10.4.4        Post-operative Clinical Performance

 

Clinical performance of the AbioCor is given in Figures 3 to 6, including parameters representative of hemodynamics, renal function, hepatic function, coagulation, hematology, and nutritional status.  The figures contain data for the twelve supported patients.  Every figure includes the preoperative average of each parameter () as the first datum plotted.  Daily averages are plotted along with the respective standard deviations.  The number of contributing patients decreased as time progressed.  Aggregate data are presented here to illustrate the general course of recovery. 

 

Figure 2 shows the cardiac output provided by the AbioCor.  Cardiac output increased by 50% on the AbioCor.


 


                                    Figure 2   Cardiac Output

 

Physiologic pressures are monitored only for a short duration post operatively mainly to avoid complications associated with extended use of indwelling lines.  Table 7 shows the mean pre vs post AOP, LAP, and CVP for the patients.  The increased AOP and the reduction in the LAP were expected on the AbioCor.  CVP did not show significant change due primarily to the need for fluid management in these patients.  However, the standard deviation is tighter post AbioCor implant than pre-implant, suggesting that while patients were supported on the AbioCor, fluid management was more routine than under heart failure condition.

 

                 Table 7.   Physiologic Pressures (mmHg) Across Patients

 

Pre-op Mean and Stdv

Post-op Mean and Stdv

p-value

AOP 

74 ± 6

86.9 ± 6.4

0.0001

LAP

19.9 ± 5.4

13.6 ± 5.4

0.001

CVP

11 ± 6.4

13.7 ± 2.8

N.S.

 

Return of renal function is shown in Figure 3 for creatinine (Cr in mg/dl).  Pre-operative mean was 1.7 mg/dl ± 0.7.  There was a postoperative overshoot with a gradual return to pre-operative over a 2-week period followed by a gradual return to high normal over a one-month period followed by further normalization over the second post operative month.  A similar behavior was seen in the BUN trend (not shown).


 

 


Figure 3. Creatinine

Figures 4 and 5 show respectively the total bilirubin, and a representative liver enzyme, AST (in mg/dl).  Immediately post-operatively, total bilirubin jumped higher due to the surgical insult.  Relatively high mean levels (~6 mg/dl) followed with large standard deviations.  Subsequent large drops near POD 56, POD 86, and POD 115 each represents the withdrawal of patient support.  The first case was a patient in acute liver failure due to fluid overload and was deemed reversible by the medical team.  However, the family requested the withdrawal of support.  The patient in the second case had chronic liver failure with cirrhosis.  His total bilirubin reached a peak of around 35 mg/dl.  The patient in the third case went into septic shock and acute liver failure prior to the withdrawal of support.  The AST data paralleled the bilirubin data both reflecting liver condition.


 

 


Figure 4.  Total Bilirubin

 


 

 


Figure 5.   AST

 

10.4.5  Special Clinical features of the AbioCor

 

During the course of the clinical trial, the AbioCor has demonstrated performance in some areas that surpassed those of the native heart.  Figure 6 shows plot of a patient undergoing extreme acidosis with pH<7 for a period of ~ 3 hrs.  The AbioCor continued to pump while the patient was treated with veno-veno ECMO which reversed the hypoxic condition.  A native heart would have failed under such extreme acidosis.


 

 


Figure 6 Reversal of Extreme Acidosis

 


Figure 7 shows a patient with an extreme case of malignant hyperthermia lasting for ~ 40 hrs.  The AbioCor continued to perform during this extreme temperature of 106-107 oF.  The patient’s temperature was controlled by the used of Dantrolene.  Again a native heart in failure would not likely have survived under such extreme condition.

 

 


Figure 7.  Hemodynamics Maintained During Hyperthermia

 


Figure 8 shows signs of recovery of a patient with identified pre-operative ascites.  Although total bilirubin rose post-operatively, over a one-month duration, with reliable cardiac output, the liver recovered.

 


Figure 8  Recovery from Liver Dysfunction

 

A final condition in which the AbioCor could function without compromise while the native heart might have problem maintaining adequate output is illustrated in Figure 9.  In the figure, the Abiocor was able to maintain 6-8 L/min of cardiac output despite having to pump against a pulmonary pressure of ~ 60 mmHg.  A native heart in cardiac failure would not have been able to provide the adequate flow to the patient.

 


Figure 9.   AbioCor Can Pump Against Pulmonary Hypertension

 


The AbioCor has demonstrated that under abnormal physiologic states such as extreme acidosis, hyperthermia, elevated PAP, and severe liver dysfunction, the system can continue to perform while medical treatment can be implemented without concerns for cardiac function to reverse the abnormality.

 

 

11.   Safety and Probable Benefit

 

The results of the initial fourteen patients implanted with the AbioCor provided sufficient data to demonstrate that the AbioCor is a safe device in patients with severe end-stage heart failure facing imminent risk of death.  Only one device failure occurred unexpectedly, representing ~ 92% (11/12) failure-free device operation clinically for the demonstrated one year bench operation.  The observed stroke rate is within the bounds observed in VADs approved for use in a much less sick patient population.  No device related infection problems, common to exteriorized implantable VADs have caused complications in AbioCor patients.  This safety feature is a substantial advantage for fully implantable devices such as the AbioCor.  Safety features for power management have been built into the system to avoid unintentional misuses that may result in hazards.   The system has been shown to be safe in a broad range of settings, inside the hospital, outside the hospital in various ordinary locales, such as restaurants, theaters, sports arenas, stores and shops, the home environment and in vehicles.

 

The probable benefits of the AbioCor are many.  The device restores normal hemodynamics and affords dysfunctional end organs, such as kidneys and livers, a fair chance of recovery as have been seen in a number of cases in the trial.  The AbioCor has demonstrated that it can support patients with chronic pulmonary hypertension, a condition that would cause heart transplant failures and could not be overcome with LVAD support.  Most importantly, clinical experience has shown that patients and caregivers can manage the system outside of the hospital environment, in their home and community settings.  The probable benefits are that patients with no chance of survival from end stage heart failure could be offered the opportunity to return home to their loved ones.

 

12.   Panel Recommendation

 

 

13.   CDRH Decision

 

 

 

14.  Approval Specifications