Mechanical assist devices Flashcards
How does IABP improve myocardial oxygen supply to demand ratio
- reducing the tension-time index (systolic wall tension) by reducing the impedance to left ventricular ejection
- increasing the diastolic pressure-time index by increasing coronary blood flow during during diastole
List complications of IABP
Vessel perforation Arterial branch occlusion Acute aortic insufficiency Gas escape/catheter rupture peripheral thrombo-embolism acute aortic dissection wound problems chronic claudication femoral neuralgia femoral pseudo-aneurysm
How are LVAD classified
Pulsatile: Thoratec, Heart mate I,
Non-pulsatile (continuous) flow: Heart mate II, Jarvik,
Location:
Totally implantable
paracorporeal
percutaneous
List indications for advanced mechanical support
Post-cardiotomy cardiogenic shock post-MI cardiogenic shock High-risk PCI Hypothermia rewarming Bridge to transplantation Bridge to recovery Long-term destination therapy Backup for high risk cardiac surgery
What are the main uses of a LVAD
Bridge to Transplantation
Bridge to recovery
Bridge to destination therapy
Bridge to decision
List potential complications of LVAD
Operative mortality 10-20%
Major bleeding (20 to 60% require mediastinal reexploration
Right heart failure (20 to 40%)
Device Malfunction
Major infection (within 3 months about 28%)
Neurologic dysfunction 8 to 20%
List available ventricular assist devices
Heartmate I (thoratec) NovaCor Thoratec DeBakey VAD Heartmate II Jarvik Van Lionheart Abiocor TAH Cardiowest
What are considerations when placing a LVAD
potential reversibility of cardiac dysfunction
cause of the caridac dysfunction
degree of right and left ventricular dysfunction
amount of circulatory support needed
patient size
Importance of the device for myocardial functional recovery
Whether the patient is candidate for cardiac transplantation
Anatomic location of collapse or deterioration
Expected duration of support
The patient’s age and severity of comorbid conditions
What are theoretical advantage of VADs
Maintains end-organ perfusion and prevents end-organ damage. End-organ damage is a predictor of survival
Resting the stunned myocardium by unloading the ventricle
Promote “reverse remodeling” by improving myocardial contractility
What are indications to do BiVAD over just LVAD
Fitzpatrick from UPEN suggested do RVAD if
CI < 2.2
RV stroke work index < 0.25 mmHg/L/M2
severe preoperative RV dysfunction on eco
Pre-operative creatinine
previous cardiac surgery
systolic BP< 90
List 4 contra-indications for mechanical circulatory support as a bridge to tranplantation
Systemic life-threatening (serious) illness
irreversible renal dysfunction
irreversible hepatic dysfunction
patient is not a candidate for transplantation
The RECOVER I: multicenter prospective study of Impella 5.)LD for post cardiotomy circulatory support
JTCS Feb 2013
Howard Frazer
16 pts post being weaned off CPB enrolled in a prospective single-arm feasibility study.
The primary endpoint was survival of the patient to.
outcomes:
recovery of native heart function was obtained in 93% of patients with bridge to other therapy in 7%
Survival at 30 days, 3 months and 1 year was 94%, 81%, and 75%
List some factors for RVAD usage after LVAD
female gender small body surface area noishcemic etiology Low mean and diastolic pulmonary pressyres Low RVSWI Pre-operative circulatory support
Describe the Impella
Impella 5.0 (Abiomed) is a 21 French microaxial pump based 9 French catheter. It is capable of producing up to 5 L/min of flow.
The left peripheral (LP) is designed to be inserted peripherally.
The left direct (LD) is tended to be placed directly into the ascending aorta via a 10-mm vascular graft.
Details of Impella
The device straddles the aortic valve with inflow residing in the left ventricular cavity and the outflow at the level of the STJ.
Managed at beside and intended for 1 week duration.
Potential benefits of the impella
Improvement in cardiac output direct ventricular unloading (reduction in left ventricular end diatolic pressure and volume) reduced myocardial oxygen demand improved oxygen demand improved coronary perfusion infarct size limitation
ABIOMED5000
Pneumatically controlled temporary external pulsatile assist device.
SIngle-use blood pumps activated by a pneumatic drive console. Blood pump composed of dual chamber system that incorporates atrial (filling) chamber with a ventricular (pumping) chamber.
resistant again ventricular arrhythmias.
inserted sternontomy.
What is Levitronix CentriMag device
Ventricular assist system designed for treatment of patients with acute cardiogenic shock of any etiology
Can generate as much as 10L/min flow is capable of support for 30 days.
Unique in that it is driven with a bearingless motor that enables the spinning component within the pump to be magnetically leviatated and rotated without contact or wear.
More details of Levitronix
No bearings, shafts, and seals that are associated within centrifugal pump
Level of hemolysis and risk of thrombus accumulation within the pump are greatly reduced.
For LVAD the INFLOW cannula is placed in the left atrium via the interatrial spetal groove (adjacent to the right superior pulmonary vein) . The outflow is placed in the ascending aorta.
For RVAD the INFLOW is positioned in the right atrial appendage with the outflow cannula in the pulmonary artery.
ACT 160 to 180
What study is key with destination therapy LVAD
REMATCH
1 year survival 50% in LVAD and 25% in medical
2 year 23% in LVAD and 8 % in medical
quality of life was improved in LVAD
How do you calculate right ventricular stroke work index (RVSWI)
RVSWI = (mean PAP - mean RAP) x SVI
stroke volume index is calculated by the CI divided by the heart rate
RAP is the right atrial pressure
a low RVSWI is a significant risk for RVAD use
So is low PAP *this indicates poor intrinsic RV contractility
List indications for Destination therapy VAD
Only the Heart Mate XVE
Refer to the eligibility of the REMATCH trial
1. Class NYHA IV end-stage LV failure for at least 90 days with a life expectancy of 2 years
2. Non candidates for heart transplantation
3. Failed response to optimal medical therapy (including diuretics, beta-blockers, ACE for at least 60 of the 90 days
4. Patient has a LV ejection fraction of < 25%
5. Demonstrated function limitation with a peak oxygen consumption of < 12 ml/Kg/min
6
What are details of Heart mate II
internal blood pump with a percutaneous lead that connects the pump to an external system driver and power source
impeller is the only moving part, spins on a blood-lubricated bearings powered by an electric motor
implant volume of 63ml
generates flow at 10 L/min at a mean pressure of 100mmHg
What are implantation techniques of Heart Mate II
Median sternonotmy on CPB
inflow cannula is inserted into opening made in the apex of the left ventricle with a coring knife
outflow cannula on the ascending aorta
pump placed in the preperitoneal pack at the level of the diaphragm
adjust the pump speed (RPM) and maintain a PI of > 3.5 to 4
What is anticoagulation strategy for heart mate II
Initiation of intravenous UFW for 12 to 25 hours for a PTT 45 to 50 start antiplatelet (81 ECASA on day 2) On day 3 start warfarin for INR 2 to 3
- some groups have stopped warfarin all together and run the INR to 1.5 to 2.0.
What are adverese events of HeartMate II LVAD support
Neurologic (6.3%) Hemorrhagic GI bleed (15%) Infection drive line/pocket Right ventricular failure (6%) Device malfunction Device replacement Hemolysis Resp Failure
Theoretical advantage of LVADs:
Maintains end-organ perfusion and prevents end-organ damage. End-organ damage is a predictor of survival
Resting the stunned myocardium by unloading the ventricle
Promote “reverse remodeling” by improving myocardial contractility
List details of first generation VADs
HeartMate XVE-only FDA approved device for destination therapy
Pulsatile flow generated through a pusher plate placed in a large housing
Requires no anticoaulation
Long-term use is limited by high probability of device malfunction and infection
Major disadvantage is the exteriorized pump
The Thoratec PVAD and Berlin Heart Excore
What is a first generation LVAD
Pulsatile, volume displacement using a pusher plate system. Example is a heart mate XVE. The pump senses when the chamber is full and activates the pusher plate. It has porcine xenograft valves.
35% device failure in 2 years
Only had to take ASA
What is second generation LVAD
Continuous flow, rotary pump. This continous rotary pump is smaller, eliminating the reservoir chamber and valves needed for first generation.
Rotary blood pump is typically an axial blood flow path, which has an internal rotor within the blood flow path that is suspended on bearings.
Inflow at apex of LV and outflow in ascending aorta.
Risk of negative intraventricular pressure. INT 2.5- 2.5
Heart mate II
What is a second generation VAD
axial flow rotors fewer moving parts lack pulsatile flow require anticoagulation does not completely empty the ventricle
What are details of second generation VAD
The pumps have become miniaturized
rotary pump of axial-flow design contributed to limiting the surface area exposed to blood for the elimination of valves, air vents, and compliance chambers.
What is 3rd generation LVAD
continuous-flow rotary device with an impeller or a rotor suspended in the blood flow path using a “non-contact” bearing design.
Heartware
Pump in the pericardial space
No points of mechanical contact
What are 3rd generation devices
main feature is that they eliminated bearing by using hydrodynamic or electromagnetic suspension of an impeller to reduce mechanical wear and trauma to blood cells
contact free rotation
What is recent outcomes for LVAD compared to transplant
At 2 years the survival of LVAD pts is about 70-80%. This is very close to transplant and the QOL is much improved.
TO date more then 1500 pts with Heart mate II
What is the primary endpoint of the HMII trial ( continuous-flow vs pulsatile)
Composite of survival free from disabling stroke and reoperation to repair or replace the device at 2 y
Primary outcome; HMII group 11%; HMXVE group 46%
Survival: HMII group 58% ; HMXVE group 24%
stroke: both about 11 and 12%
There was a predictable mode of failure for HMXVE at 12 to 18 months (bearing failure or dysfunction of the valves)
What was the survival in the rematch trial
Destination therapy
1yr survival
HM 52%
Meds 25%
2yr survival
HM 23%
Meds 8%
Signal of CHF decompensation
Symptoms Medication issues Hyponatremia Unresponsive to CRT Needs inotropes End organ dysfunction
Intermacs
Name 7 clinical profiles
- Crash and burn : hypoperfusion, shock
- Sliding on inotropes : inotropes support and deteriorating
- Stable on inotropes: failure to wean inotropes
- Frequent flyer: fluid retention, increasing dose of diuretics
- Housebound: only comfortable at rest
- Walking wounded: minor activities
- Limited to mild exertion
Intermacs
Name 3 modifiers
Arrhythmia
Temporary mechanical support
Frequent flyers
Risk factors for decline after VAD
Poor nutrition Poor renal function Low pulmonary pressure (failing RV) Low liver function Infection Small body size Anemia
Advantages and disadvantages of the axial pump
Advantages
Durability
Quiet
Smaller
Disadvantages
Suction events
Anticoagulation
What are indications for LVAD
- Class 4 Heart failure and failed OMT for at least 60 to 90 days
- Left ventricular ejection fraction of < 25%
- Functional limitation with a peak oxygen consumptions of < 12 ml/kg/min or
- Continued need for intravenous inotropic therapy owing to symptomatic hypotension, decreasing renal funtion, or worsening pulmonary congestion
- Appropriate body sise (BSA > 1.5)
1/3 of BTT pts are lose transplant candiancy
17% of DT receive transplant
What percentage of LVAD are placed in INTERMACS level 1 and 2
60 to 80%
What anatomical abnormalities need surgical correction at time of LVAD
PFO: creates negative pressure R-L shunting
AI: prevents a circuit from Ascending aorta back to LV
TR: prone to TR because of dilation of annulus, RV dysfunction, and pacing leading–repair TR to maximize RV forward flow
LV apical thrombus: must be removed to prevent systemic embolization
List specific problems with VAD
Right heart failure (20 to 40%)
Device malfunction (frequently at 18 months was high..now very low)
Major injection: most common cause of death about 30%!
Neurological dysfunction–8 to 20%
Describe the principles of an intra-aortic balloon pump and draw the tracing
counter-pulsation device timed to a inflate during diastole thereby augmenting organ perfusion and deflate just prior to systole, thereby reducing left ventricular afterload
