IABP

Question 1

IABP trace labelled

Answer 1

=>With correct timing and good augmentation-
* Assisted systoly and Assisted EDP < Unassisted systoly and EDP
* Augmented diastolic >Unassisted systoly
* Balloon inflation happens at Dicrotic notch which should appear as a sharp V on trace

Question 2

Inflation
Q. When does it occur?
Q. what is the physiological basis?
Q. where on ECG does the inflation happen
Q. Where on art line trace does it happen?
Q.correct shape of tracing on balloon inflation

Answer 2

• Inflation should occur at the onset of diastole(Isovolumetric Relaxation Phase)
  marked by the dicrotic notch on the arterial waveform (closure of aortic valve).
• When balloon inflates, blood is displaced retrograde under pressure into the coronary ostia and forward into systemic circulation.
• When timing is correct, the dicrotic notch is sharp and well-defined (“V-shape”) on the tracing.

Question 3

Q. Correct timing of balloon deflation
Q. Physiologic outcome of correct balloon deflation
Q.What is an adequate augmentation?

Answer 3

->Balloon deflation → during isovolumetric contraction, immediately before assisted systole, causing:
->↓ Assisted end-diastolic pressure (unloading LV).
->↓ Afterload → ↓ LV work

->Mechanism:
* Rapid deflation → creates low-pressure sink ahead of LV, reducing afterload.

⸻

Adequacy of augmentation can be measured by:
1. Degree of increase in diastolic augmented pressure
* Usually 30–70% above unassisted diastolic pressure.

Question 4

Factors affection Diastolic Augmentation

Answer 4

Diastolic assisted pressure is influenced by:
* Volume of the balloon.
* Size of the balloon.
* Position of the balloon tip (should be distal to left subclavian).
* Circulating blood volume.
* LV dysfunction.
* Medications

->Improvement in LV function over time will reduce the diastolic augmentation

Question 5

Timing of Balloon Inflation & Deflation
Q.Definition
Q. Application
Q. Significance of 1:2 timing

Answer 5

Definition:
Timing refers to synchronization of balloon inflation and deflation in relation to the cardiac cycle.

⸻

I. Modes of Assistance
* 1:1 → every diastole and systole are assisted.
* 1:2 → every alternate diastole and systole are assisted.
* 1:3 → used during weaning (further reduced assistance).

1:2 timing->halves the pressure in great cardiac veins and is often the Point of Failure in weaning process.

Question 6

Premature (Early) Inflation

(i.e. before dicrotic notch)

Answer 6

=>Waveform features:

->Diastolic augmentation (peak B) encroaches on the peak corresponding to unassisted systole (peak A) – the two peaks have merged and are barely distinguishable.
->There is no ‘sharp V’ or dicrotic notch between peaks A and B.

Question 7

Physiological Consequences of
Premature Inflation

Answer 7

• Premature closure of aortic valve
  → ↑ LV afterload and ↑ LV oxygen demand.
• Incomplete emptying of LV→There may be an increase in LVEDV, LVEDP and PCWP
• ↓ stroke volume and cardiac output (SV ↓ up to 20%).
• Aortic regurgitation may occur.
• ↓ LV ejection and ↓ coronary perfusion

To correct–>Delay the onset of IAB inflation, so that it inflates at the dicrotic notch resulting in a ‘sharp V’

Question 7

Late Inflation
Waveform features

Answer 7

=>Inflation of the IAB occurs after the dicrotic notch (B)
=>Absence of a sharp V at the point of IAB inflation (should occur at B – the dicrotic notch)
=>The augmented DBP (peak C) is less than the **unassisted SBP (peak A) **– it should be higher

Question 7

Late Inflation
Physiological consequences

Answer 7

Features:

• Reduced diastolic augmentation peak and its benefits (inadequate coronary perfusion).

Consequences:
* ↓ Mean diastolic pressure.
* ↓ Coronary artery perfusion.
* ↓ LV unloading → ↑ LV work.
* Patient may still receive retrograde blood flow, but markedly reduced.

To correct–>Adjust the timing so that the IABP inflates at the dicrotic notch.

Question 8

Early Deflation
Waveform abnormalities

Answer 8

=>Sharp drop in pressure immediately following the peak of diastolic augmentation (peak B).
=>Diastolic augmentation may be suboptimal
=>With early deflation a widened U-shaped trough is typically seen.
=>Assisted EDP not less than unassisted EDP.
=>Assisted systole not less than unassisted systole.

Question 9

Physiological effects of Early Deflation

Answer 9

=>Inadequate coronary perfusion, with the potential for retrograde coronary blood flow(coronary steal)–>angina due to decreased myocardial oxygen supply.

=>Suboptimal afterload reduction and increased myocardial oxygen demand

To correct–> Prolong the IAB inflation time, so that it deflates at the end of diastole, just before the onset of isovolumetric systolic contraction.

Question 10

Late Deflation
Waveform abnormalities

Answer 10

=>The peak corresponding to diastolic augmentation (peak C) is widened.
=>Assisted aortic EDP (trough E) NOT lower than, the unassisted aortic EDP (trough G).
=>The upstroke of assisted systolic BP (peak F) has a gentle gradient resulting in a prolonged rise.

Question 11

Late Deflation
Physiological consequences

Answer 11

=>Physiologically:

Myocardial oxygen consumption will increase
* Afterload will be ↑
* Myocardial O₂ requirements will ↑ because the left ventricle experiences a longer period of isovolumetric contraction (when most myocardial oxygen consumption occurs) and has to contract against greater resistance (afterload).

=>To correct, Shorten the IAB inflation time, so that the IAB deflates at the end of diastole – just before isovolumetric contraction of the left ventricle.

Question 12

TRIGGER

Answer 12

->It is the physiological signal from the patient identified to the beginning of a new cardiac cycle.
->Most common trigger used is ECG – R wave = denotes onset of systole (electrical events occur slightly before the corresponding mechanical events).
=>Other triggers can be used – Aortic pressure waveform
* only detects systole & diastole as they occur, ↓ the efficiency of the response.
->Pacemaker can be used as another trigger –
* may need to be changed depending upon:
* Rhythm
* Type of pacemaker (atrial / ventricular).
and patient’s response to therapy

=>In Arrhythmias
* Best option is to attempt to restore a regular rhythm
→ e.g. correction
→ cardioversion
→ antiarrhythmics
* If arrhythmia persists → AFIB trigger can be used to deflate the balloon on every R wave that occurs, R/R wave or real-time deflation.

Question 13

Inadequate Diastolic Augmentation – Causes

Answer 13

1. Patient Factors

i) Tachyarrhythmias
* ↓ LV filling time → ↓ SV.
* Less blood volume injected into aorta→Less blood displaced by balloon inflation.
* ↓ amount of time that balloon remains inflated → ↓ amount of blood displaced during diastole.

ii) Hypovolemia
iii) Very poor LV function
iv) Vasodilatation

⸻

2. Catheter Factors
   
   • Position
   • Size
   • Balloon volume

→ The pressure waveform changes (weakly augmented diastolic peak).
→ Leak in circuit / balloon rupture → ↓ augmentation.

Question 14

Confirming position

Answer 14

• Confirm intra-arterial position with arterial waveform
• Fluoroscopic guidance: tip 2 cm below L subclavian take-off.
• CXR: tip at 2nd ICS / just above L main bronchus.
• Echocardiogram: distal tip origin of L subclavian artery.
• Manual check: Measure length prior to insertion -> Landmarks: site of insertion–>Umbilicus–>Sternal angle.
• Clinical check: diastolic augmentation.

Question 15

Anticoagulation post IABP insertion

Answer 15

• Evidence from IABP-SHOCK II: anticoagulation did not ↑ risk of bleeding but also no anticoag → ↑ thrombotic risk.
• Overall, conflicting evidence – most units use fixed-dose anticoagulation without measuring APTT.

Question 16

Indications

Answer 16

=>Absolute:
1)* Failure to come off bypass.
2)* Acute MR / VSD & haemodynamic compromise->decreases regurgitant flow in acute MR.
3)* Severe low output state / waiting for surgery.

=>Relative:
* High-risk CABG / PCI patients pre-op.
* Cardiogenic shock while waiting for CABG / PCI.
* Takotsubo CMP.
* Neurogenic / severe sickness CMP or SAH.

Question 17

Contraindications

Answer 17

Absolute:
* AR.
* Aortic aneurysm.
* Aortic dissection.
* LVOT obstruction.
* Severe sepsis.
* Uncontrolled coagulopathy.

Relative:
* Atherosclerosis.
* Tortuous arteries.
* C.I. to anticoagulation.

Question 18

Complications

Answer 18

• Ischaemic limb.
• Pseudoaneurysm
• Haemorrhage.
• Aortic dissection.
• Embolic / cholesterol / helium.
• CVA.
• Thrombocytopenia / haemolysis.
• Balloon leak.

Question 19

Summary of inappropriate timing

Answer 19