How intra-aortic balloon pumps and microaxial flow pumps work, current evidence and indications, setting up and troubleshooting, and the checks each shift.
At the bedside
Timed steps- 1
Know when each device is used
IndicationIABP: mechanical complications of MI (acute MR, VSR) as a bridge, refractory ischaemia, selected high-risk PCI, LV unloading on VA ECMO. Routine IABP in AMI shock is NOT recommended after IABP-SHOCK II. Impella CP: selected STEMI cardiogenic shock (DanGer Shock), high-risk PCI, LV venting on VA ECMO ('ECPELLA'); Impella RP for RV failure.
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Confirm position
PositionIABP tip 2–3 cm below the origin of the left subclavian artery — on CXR around the level of the carina / 2nd–3rd intercostal space. Impella: inlet in the LV below the aortic valve (about 3.5 cm for CP), outlet above the valve; confirm with echo and the console position waveform.
- 3
IABP timing (check on 1:2)
TimingInflate at the dicrotic notch (aortic valve closure) → diastolic augmentation; deflate just before systole → assisted end-diastolic pressure lower than unassisted, and assisted systole lower than unassisted systole. Trigger: ECG (R wave) or arterial pressure.
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Anticoagulation
AnticoagulateImpella: systemic heparin plus heparinised (or bicarbonate-based) purge per manufacturer/protocol. IABP: heparin commonly used, especially at 1:2–1:3 or prolonged support; unit protocols vary.
- 5
Hourly device checks
MonitorLimb: distal pulses/Doppler, colour, temperature, sensation hourly. Left radial pulse and urine output (IABP migration can occlude the subclavian or renal arteries). Haemolysis (Impella): urine colour, plasma free Hb, LDH. Console alarms, purge pressure (Impella), helium supply (IABP).
- 6
Wean and remove
WeanIABP: reduce ratio 1:1 → 1:2 → 1:3 (or reduce augmentation) while haemodynamics and lactate stay stable; avoid prolonged 1:3 (thrombosis). Impella: reduce P-level stepwise with echo and haemodynamic checks. Remove with a haemostasis plan; check the limb afterwards.
Temporary mechanical circulatory support compared
| Device | Flow added | Access | Main benefit | Main risks |
|---|---|---|---|---|
| IABP | ~0.5 L/min | Femoral (7–8 Fr); axillary for longer use | Afterload reduction, coronary perfusion; simple, cheap, widely available | Limb ischaemia, migration, balloon rupture, thrombocytopenia; no mortality benefit in AMI-CS |
| Impella CP | ~3.5–4 L/min | Femoral (14 Fr) | Direct LV unloading; DanGer Shock mortality benefit in selected STEMI-CS | Haemolysis, bleeding, limb ischaemia, AKI, malposition; high cost |
| Impella 5.0/5.5 | ~5–5.5 L/min | Surgical axillary cut-down | Fuller LV support, allows mobilisation | Surgical access, bleeding, haemolysis |
| Impella RP | ~4 L/min (right side) | Femoral vein | RV failure (e.g. RV infarct, post-LVAD) | Haemolysis, thrombosis, malposition |
| VA ECMO | 3–6 L/min | Femoral artery + vein | Biventricular + respiratory support | LV distension, bleeding, limb ischaemia, stroke |
Flows are approximate manufacturer ranges.
IABP timing errors
| Error | Waveform clue | Consequence |
|---|---|---|
| Early inflation | Inflation before the dicrotic notch; augmentation encroaches on systole | Premature aortic valve closure, ↑ LVEDV, ↑ afterload |
| Late inflation | Inflation well after the dicrotic notch; notch visible | Reduced coronary perfusion benefit |
| Early deflation | Sharp drop after augmentation; assisted end-diastolic pressure may equal unassisted; U-shaped | Sub-optimal afterload reduction, possible retrograde coronary flow |
| Late deflation | Assisted end-diastolic pressure ≥ unassisted | Increased afterload and myocardial O₂ demand — most harmful |
IABP balloon size by patient height (typical manufacturer guide)
| Height | Balloon volume |
|---|---|
| <152 cm | 25–30 mL |
| 152–163 cm | 34 mL |
| 163–183 cm | 40 mL |
| >183 cm | 50 mL |
Manufacturer charts differ slightly; check the device insert. Many Indian adults need 34 mL rather than 40 mL.
Calculators for this topic
References
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Escalating mechanical support in cardiogenic shock
Step 1 of ~3
Simplified decision tree for temporary MCS (heart-team decisions).
Decision: Mechanical complication of MI (acute MR, VSR, free-wall rupture)?
Based on Thiele H, Zeymer U, Neumann FJ, et al; Møller JE, Engstrøm T, Jensen LO, et al; Byrne RA, Rossello X, Coughlan JJ, et al; Lorusso R, Shekar K, MacLaren G, et al. Educational use; follow local protocol.
Pathophysiology
IABP: diastolic inflation displaces ~30–50 mL of blood, raising aortic diastolic pressure (coronary perfusion); deflation lowers aortic end-diastolic pressure and LV afterload. Its effect needs a native rhythm and some LV function, and is blunted in tachyarrhythmias.
Impella: draws blood from the LV into the aorta continuously, lowering LV end-diastolic pressure and volume (myocardial O₂ demand) while increasing forward flow — 'unloading'. Suction events occur with hypovolaemia, RV failure or malposition against the LV wall.
Evidence
- IABP-SHOCK II (2012): 600 patients with AMI-CS undergoing early revascularisation; IABP did not reduce 30-day mortality (39.7% vs 41.3%), and later follow-up showed no long-term benefit.
- DanGer Shock (2024): 360 STEMI-CS patients; Impella CP reduced all-cause death at 180 days (45.8% vs 58.5%; HR 0.74). The composite of serious adverse events (severe bleeding, limb ischaemia, haemolysis, device failure, worsening aortic regurgitation) was more frequent, as was RRT.
- ESC 2023 ACS: routine IABP not recommended in CS without mechanical complications; short-term MCS may be considered in selected patients.
- SCAI stages guide timing: escalation is usually considered at stage C not responding, or D.
Controversies
- Impella outside the DanGer Shock population (e.g. NSTEMI-CS, comatose OHCA) remains uncertain.
- Routine LV venting on VA ECMO: observational data suggest benefit; randomised evidence is limited.
- IABP retains a role in resource-limited settings for mechanical complications and as a bridge, given low cost and familiarity.
🇮🇳 India notes
- IABP is widely available in Indian cath labs and is often the only device in tier-2 cities; use it for evidence-based indications (mechanical complications, bridge) rather than routinely.
- Impella is limited and expensive in India; mainly found in large cardiac centres.
- Many Indian adults are of shorter stature: check balloon size against height (34 mL is common).
References
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Test yourself
Module quiz · score 70% to complete the module
Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.