| Strategy |
Advantages |
Limitations |
|
Positive pressure ventilation:
the use of positive pressure to decrease LV preload and afterload (by manipulating transmural pressure)
|
- Easy to apply
- Minimally invasive
- Added benefit of improved oxygenation and gas exchange
- Invasive ventilation has the added benefit of anaesthesia +/- paralysis, which decreases whole-body oxygen demand
|
- Preload reduction may result in hypotension in the volume-depleted patient
- Increased intrathoracic pressure increases RV afterload, exacerbating right heart failure
- Positive pressure may result in barotrauma and volutrauma
- All the risks of mechanical ventilation apply, eg. VAP
|
| Temporary transcutaneous pacing: |
- Requires minimal skill to apply
- Minimally invasive
- Cardiac output will increase in proportion to
|
- Requires a substantial amount of analgesia and sedation
- Uncomfortable for the patient
- May cause significant tissue damage
- Not a long-term solution
- Poor A-V synchrony
|
| Temporary transvenous pacing |
- Comparatively easy to insert
- Dual-chamber pacing may improve A-V synchrony and restore the "atrial kick".
- Not only does it work in bradycardia, but also by "overdrive pacing" in tachycardia, where the slowed heart rate allows for longer diastolic filling
|
- Requires some expertise to manage and troubleshoot
- Invasive, with all the risks of large-bore central venous access
- Generally, one can only pace the ventricle, which means A-V synchrnoy will be lost; the "atrial kick" may be sorely missed by patients with severe valve dysfunction
|
| Cardiac resynchronisation therapy: biventricular pacing |
- Restores synchrony to ventricular contraction in patients with severe heart failure
- There is strong evidence that CRT reduces mortality and hospitalisation (i.e. it is superior to AICD or medical therapy).
|
- Requires specialist skill to insert and adjust; hardly an emergency procedure
- To benefit, one must have LBBB, a wide QRS, and an LVEF less than 35%.
- Generally, only about 5-10% of heart failure patients will benefit
- There is a "heterogeneity of effect" in patients who do not meet the recognised criteria (read: it does them no good)
|
| Intra-aortic balloon pump: |
- Decreases LV afterload
- Improves coronary arterial filling in diastole
- Improves forward flow though defective mitral valves
- Nowadays, little adjustment is required (automatic timing is usually satisfactory)
- "Severe" cardiogenic shock is still not very well investigated, and there may be an unrecognised mortality benefit in this group.
|
- Violently invasive
- Requires a certain level of expertise to place correctly.
- Significant complications are associated with its use, including a non-zero rate of death and limb loss.
- The mortality benefit in most patients might either be marginal or altogether absent, depending on what you read. Certainly, the IABP-SHOCK II trail did not demonstrate any survival improvement.
- Does not benefit the right ventricle.
- Contraindicated in aortic regurgitation
- Poor effect in AF, particularly rapid AF
|
| Ventricular assist devices: |
- Decreases myocardial workload
- Offers a bridge to heart transplantation
- Effective temporary support for myocardial stunning
- May afford a period of outpatient management
|
- Highly invasive
- Requires surgical expertise to implement
- Requires significant anticoagulation
- Substantial risk of infection (50%)
- In spite of anticoagulation, there is a significant risk of thrombosis
|
| VA- ECMO |
- Not only decreases myocardial workload- it may take over all of the circulatory workload.
- Attends to both circulation and gas exchange
- Easier to implement (percutaneous technique does not require surgical expertise)
|
- Highly invasive
- Requires expertise to implement
- Requires significant anticoagulation
- In spite of anticoagulation, there is a significant risk of thrombosis
- All the complications of large-bore arterial and venous access
- Can increase LV afterload and cause LV dilatation
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