Question 13

Created on Wed, 05/27/2015 - 19:14
Last updated on Sat, 05/12/2018 - 19:50
Pass rate: 71%
Highest mark: ?

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Compare and  contrast the advantages and  limitations  of the intra-aortic balloon  pump  (IABP)  and  ventricular assist  devices (VAD). (You  may tabulate your answer).                 

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College Answer

IABP

VAD

Can be inserted percutaneously  in ICU  or CCU

While percutaneous insertion is possible, frequently require
anaesthesia and  a surgeon for insertion and removal.

Indications

Used post cardiac surgery /
cardiogenic                  shock following an infarct

Frequently  used   in   post 
cardiac surgical patients.
Used   as     a     bridge     to transplantation.

Logistics

Intensivists  more  familiar
with  IABP

Can   be  used during transport

Less familiar  with  VAD, 
greater degree  of complexity, more  difficult to use during transport

Anticoagulation

Usually     no       need      for anticoagulation

Need for anticoagulation

Not effective in the setting of      CI       <      1.2       and 
tachyarrhythmias

Greater control on  overall
cardiac output  as  well  as
Rt    and     Lt     ventricular output

Complications

Lower       limb       ischemia,
hematoma,   aortic   trauma are complications

Bleeding,             infection,
hemolysis, device failure

Discussion

I love it when they invite you to tabulate your answer.

Among the things worth mentioning is the horrific rate of infectious complications with the VAD (up to 50% of patients have an LVAD-associated infection) and the fact that its not merely anticoagulation, but insane anticoagulation that is required (APTT target is 150-200).

It is difficult to compare the two therapies, of course. An IABP is a supportive treatment to assist the recovering cardiac patient. The VAD is essentially a mechanical heart. There are reports of people who were awake, and asystolic, with a VAD in situ.

Beyond the tabulated answer offered here, the following chapters may be meaningful:

A slightly expanded answer, with more detail, is also offered:

LV Assist Device vs Intra-Aortic Balloon Counterpulsation
 

IABP

VAD

Indications

No choice but pump

  • Failure to come off bypass
  • Severe aortic stenosis
  • Mitral regurgitation
  • Ventricular septal defect 

Probably harmless, but probably not useful

  • High-risk PCI patients (pre-op) - IABP-SHOCK II
  • High-risk pre-CABG patients (low LVEF)
  • Cardiogenic shock while waiting for PCI (i.e. bridge to definitive intervention)
  • Pulmonary oedema in spite of maximal medical management

Totally experimental

  • Takotsubo cardiomyopathy
  • Neurogenic stress cardiomyopathy of subarachnoid haemorrhage

Known to be pointl

Firm indications:

  • Failure to come off bypass
  • Cardiogenic shock
  • Cardiac arrest
  • Fulminant myocarditis

Potential indications:

  • High risk CABG patients (pre-op)
  • High-risk PCI patients (pre-op)

Contraindications

Absolute contraindications

  • Aortic regurgitation
  • Aortic aneurysm
  • Aortic dissection
  • Severe sepsis
  • Uncontrolled coagulopathy

Relative contraindications

  • Atherosclerosis and arterial tortuosity
  • Left ventricular outflow tract obstruction
  • Contraindications to anticoagulation
  • Aortic regurgitation
  • Aortic aneurysm
  • Aortic dissection
  • Severe sepsis
  • Uncontrolled coagulopathy
  • Left heart thrombus

Advantages

  • Bedside insertion
  • Familiarity among ICU staff
  • Less invasive
  • Flow is pulsatile; organ perfusion benefits
  • Able to compensate for all cardiac function (i.e. useful in the setting of asystole)
  • May remain in situ for longer than the IABP
  • Contrary to the college answer above ("more difficult to use during transport") most patients with VADs can be mobilised normally (Mohiyaddin, 2018)

Disadvantages

  • Useless if the cardiac index is less than 1.5
  • Insertion may be frustrated by poor peripheral arterial anatomy
  • Non-pulsatile flow; poor organ perfusion
  • Requires sternotomy for insertion (for most except the TandemHeart device, which can be inserted percutaneously)
  • Unfamiliarity among ICU staff

Anticoagulation

May not require anticoagulation

Requires mandatory anticoagulation

Complications

  • Common complications
    • Mild limb ischaemia - 2.9%
    • Balloon leak - 1.0%
    • Major limb ischaemia - 0.9%
    • Haemorrhage - 0.8%
    • Leg amputation due to ischaemia - 0.1%
  • Rare complications
    • Atheromatous cholesterol emboli
    • Aortic or arterial dissection
    • Cerebrovascular accident
    • Thrombocytopenia
    • Haemolysis
    • Helium embolism
  • Infection is the major cause of morbidity; something like 50% of the implanted devices get infected.
  • The LV gets (understandably) irritated by the presence of an LVAD, and in 25% of patients ventricular arrhythmias develop
  • Thrombi form on the walls of the device in spite of anticoagulation, and 10-16% of people have thrombotic complications.
  • Some degree of haemolysis and thrombocytopenia occur in everybody

Even more broadly, the chapter on mechanical haemodynamic support strategies contains a comparison of several other mechanical methods of increasing cardiac output.

References

To the tabulated answer presented here, I would add a reference or two to aid those (like me) who have never even seen a VAD.

UpToDate has a nice chapter on VADs.

My own barebones summary of the VAD is available here. IABP receives a slightly more elaborate treatment here.

EMCrit brandishes the expertise of somebody who works with these things, and I take that seriously.

Additionally, there is an insanely colourful brochure which has device-specific recommendations.