Mechanical circulatory support Flashcards
What are the 4 mains types of mechanical circulatory support
Intra aortic baloon pump
Impella device
Tandem heart
ECMO
IABP how does it work? CO?
Essentially a balloon on a stick in the aorta
Inserted into femoral artery -> tip in descending aorta
Inflates in diastole
Deflates in systole
-> reduces vascular resistance and increase CO (up to 0.5L/min)
What is the impella device? CO?
Small pump -> inserted transfemorally into LV
Has external pump outside body
Sucks blood from LV -> external pump -> Aorta
Increases CO by 1-5L/min
What is the tandem heart? CO?
2 catheters
1st removes blood from LA
- Femoral vein -> Right atrium -> septal puncture -> Left atrium
- 2nd pumps blood into common iliac artery
- Femoral artery puncture
Increase CO by 2.5-5L/min
VAECMO vs VVECMO
Venous - arterial ECMO
- Catheter in vein removes blood -> gets oxygenated and put back in artery eg descending aorta
Venous venous ECMO
Blood taken from femoral vein
-> returned into superior vena cava
Which ECMO might worsen LV failure?
VA ECMO
As blood pumped retrograde into Aorta
-> Increases afterload
Key contraindication to all MCS
Unable to tolerate anticoagulation eg Haemorrhagic stroke
Severe peripheral arterial disease
IABP contraindications
significant AR (as will worsen)
Aortic aneurysm / dissection
Main indications for IABP
Increase coronary blood flow in patients awaiting revascularisation
Reduce afterload in acute heart failure / papillary muscle rupture + MR
[no data to say it improves outcomes in pure cardiogenic shock]
Contraindications for impella
Mechanical AVR
LV thrombus
VSD
Severe preipheral arterial disease
[Has to pass through AV]
AS / AR and the impella
AS - may be harder to place and may cause calcium embolism
AR - Less effective as blood pumped to ascending aorta
How does balloon pump increase coronary blood flow
‘Diastolic augmentation’
Coronary blood flow mainly in diastole
Balloon inflates in diastole -> increased blood in proximal aorta -> increased to coronaries
What does the dicrotic notch on ABP trace represent?
Aortic valve closure
What do aortic pressures look like in relation to ECG timings? What happens with a IABP?
Increase in systole then slow decrease in diastole
With pump pressures high in diastole
How does IABP affect systole
Deflates in presystole
-> creates a vacuum effect which helps pull blood out LV
How does IABP know when to inflate / deflate?
Uses ECG
Inflates in middle of T wave (start of diastole)
What does each part of this correspond to with IABP? What setting is this one
1:1 - inflates with each cardiac cycle
Where is the systolic and diastolic pressures on this IABP
Systolic lower
Augmented diastolic - higher and broader
What does an augmented pressure of 116mmHg mean?
Pressure inside balloon + early diastolic pressure
What does this IABP pressure tracing show?
1:2 - inflates on every second cardiac cycle
What happens to peak systolic pressure with ballon pump?What does this mean
Assisted peak systolic pressure is lower
-Because unassisted end diastolic pressure is lower [due to deflation and vacuum effect]
-> Reduces Afterload
What does the diastolic reporting on the console represent with the IABP
end diastolic pressure
[NOT the augmented pressure]
Common complications of IABP
Thrombocytopenia
Bleeding
Vascular injury including aortic dissection
Femoral arery occlusion -> limb ischemia
Why might someone develop acute kidney failure after insertion of IABP?
Balloon too big and occludes renal arteries
IABP whats happened here
Balloon rupture
There should be no blood in IABP tubing as it is filled with air
What are ABCD on this graph of IABP
A augmented diastolic pressure
B systolic pressure
C end diastolic pressure
D end systolic pressure
What does the parts of the impella represent
Red tracing pressure at outlet of device (in aorta)
Green pressure tracing is the motor current
-How much energy the motor is using
If impella outlet tracing looks like this whats happened
Its moved into LV
[LV pressure waveform]
If the motor pressure tracing looks like this whats happened?
Inlet and outlet in the same chamber
Either Aorta / LV
Impella - whats do you need to do?
Retract the impella as Inlet and outlet in LV
- Green non pulsatile - both inlet and outlet in same chamber
- Outlet (red) LV pressure tracing
Impella - whats do you need to do?
Push impella further in as both in Aorta
-Green non pulsitile -> inlet/outlet in same chamber
-Red outlet - Aortic tracing
On Echo whats the ideal place of impella
inflow cannula 3.5cm below aortic valve
Not touching the MV leaflets / chordae
What is used along with an impella to assess haemodynamics?
Pulmonary artery PA catheter
Assesses
- central venous pressure
-pulmonary capillary wedge pressure (adequate preload)
What can be used for patients with heparin induced thrombocytopenia and an impella divice
Bivalirudin
Cardiac arrest -> LAD stent
Remains hypotensive despite inotropes and has low sats
What device would you choose?
Impella
Allow the LV to rest post revascularisation
Chest pain and this ecg
On apixaban for known AF and loaded with clopi in ED
L main stenosis on cath
Which device and what option
Balloon pump while awaiting CABG
Which MCS devices use a pump external to the body
Tandem heart
ECMO
In terms of heart pressure complications what is unique to ECMO vs other MCS options
Volume loads left ventricle
-> Can worsen function
What does ECMO need to function? How does it affect afterload
Requires adequate preload (volume)
No effect on afterload -
- Ie needs to be treated seperately with pressors / tropes
With a PA catheter, when do you want to measure pressures?
End expiration
What do these bits of RA pressure correspond to?
Which bit do you use to estimate CVP?
a - Atrial contraction
c - TV ‘Cusps’ buldge
x - Atrial relaXation
v - Venous blood fills RA
y - atrial emptYing
Measure just before systole and end expiration - at C
Usual RV pressures with PA catheter in healthy person
20 systole
0 diastole
What do these pressures indicate during insertion of PA catheter ? How do you know you’re in the PA
RA -> RV -> PA
In PA when
-systolic pressures remain similar to RV but diastolic pressures are higher
-Dicrotic notch from closure of PV
What is and How to you calculate pulmonary capilliary wedge pressure?
Usual value in healthy?
Estimate of LA pressure
Inflate ballon in PA and slowly advance in PA until you get a venous pressure tracing
[Therefore get static blood between catheter and LA ]
Should be <12mmHg
2 methods of using PA catheter to measure CO
Thermodilution
Fick method
How does thermodilution in PA catheter work?
Inject room temp NaCl
->measure change of temp of blood
If CO
-High -> less time for mixing -> minimal temp change
-Low ->more time for mixing -> bigger temp change
When would themodilution be very unreliable
Tricuspid regurg
-cool saline flows back
VSD
How does the Fick method work
Use mixed venous %SPO2 from PA catheter
Arterial %SPO2
Hb
Calculate SVR? Where can you get the values from?
(MAP - CVP)/CO
What does a high SVR indicate
Approx pressures in
RA?
RV?
PA?
LA / PCWP?
RA - 5mmHg
RV - 5 diastolic, 20 Systolic
PA - 10 diadolic, 20 systolic
LA - 10
Pt with sepsis and LVEF 30%
Shocked.
MAP 55
CVP 13
PCWP 18
Venous O2 45%
spo2 99%
Hb 15g/dl
What can you take from this?
CVP is high
PCWP high
venous SPO2 low
CO = 1.8L
Likely cardiogenic shock
