14.1
Hemodynamic support: when and what device
Maintaining adequate tissue perfusion is critical for survival. PCI may result in decreased cardiac output and tissue hypoperfusion or may be performed in the setting of decreased or absent perfusion (such as in cardiogenic shock or cardiac arrest). Although no randomized trials have demonstrated a decrease in in-hospital mortality or major complications with use of hemodynamic support devices , such devices may increase the safety of high-risk PCI and potentially improve the outcomes of cardiogenic shock or cardiac arrest. There are 6 hemodynamic support devices currently available [intraaortic balloon pump (IABP), Impella, veno-arterial extracorporeal membrane oxygenator (VA-ECMO), Tandem Heart, Protek Duo, and Impella RP]. The first section of this chapter will discuss when such devices should be used, and the second will provide step-by-step instruction for use of IABP, Impella, VA-ECMO, and Tandem Heart.
14.1.1
Hemodynamics
The key parameters that determine the need for hemodynamic support are the patient’s ejection fraction and hemodynamics before, during or after PCI ( Fig. 14.1 ).
Before PCI :
The most important factor for determining the need for hemodynamic support are the baseline hemodynamics. In some settings the indication is clear. For example, in cardiac arrest, hemodynamic support with VA-ECMO is essential to prevent death (VA-ECMO supports both circulation and oxygenation). Similarly, in many patients with cardiogenic shock hemodynamic support is needed. In stable patients undergoing elective PCI, determining whether hemodynamic support is needed can be challenging and depends heavily on the anticipated risk of PCI ( Section 14.1.2 ).
Right heart catheterization can help determine the patient’s hemodynamic status and is strongly recommended in patients with low ejection fraction undergoing complex PCI or patients with unclear hemodynamic status. High pulmonary capillary wedge pressure (>18 mmHg) is suggestive of left ventricular failure and low pulmonary artery pulsatility index (PaPi<0.9) is suggestive of right ventricular failure. Patients with severely elevated pulmonary capillary wedge pressure (>25 mmHg) and low mixed venous oxygen saturation (<50%) are at high risk of periprocedural pulmonary edema and shock.
The Swan Ganz catheter can be left in place during the procedure to monitor hemodynamics (pulmonary artery pressure) during PCI and determine the need for escalation or de-escalation of support.
During and after PCI :
Hemodynamic support may be needed during or after PCI if the patient develops hemodynamic instability (such as hypotension or acute pulmonary edema). Sometimes the need for hemodynamic support may be anticipated, whereas in other cases it may be unexpected (such as acute vessel closure or left main dissection).
14.1.2
Risk of PCI
The risk of PCI depends on location and morphology of the target lesion(s) and anticipated PCI techniques.
- 1.
Lesion location:
- a.
Unprotected left main (especially in patients with occluded or diseased right coronary artery).
- b.
Last remaining vessel.
- a.
- 2.
Lesion morphology:
- a.
Severe calcification and tortuosity.
- b.
High-grade baseline stenosis that carries high risk of acute vessel occlusion during wiring attempts.
- c.
Bifurcation lesion with large side branches with high-grade stenoses that may be challenging to protect.
- d.
Large intracoronary thrombus.
- a.
- 3.
Procedural plan (complex, prolonged procedures resulting in significant ischemia):
- a.
Atherectomy.
- b.
Retrograde CTO PCI.
- a.
Prophylactic hemodynamic support is in most cases recommended (if feasible) in patients who have both abnormal hemodynamics and are need PCI of high-risk lesions .
Hemodynamic support is not used prophylactically in most patients with (1) abnormal hemodynamics undergoing a low-risk procedure or (2) normal hemodynamics undergoing high-risk PCI, but should be immediately available for use in case of hemodynamic decompensation. Many operators insert a 4 French femoral sheath so that they can rapidly insert a hemodynamic support device (IABP, Impella, VA-ECMO) if the need arises during the procedure. Prophylactic upfront hemodynamic support may be considered in some of these patients.
14.1.3
Contraindications for Impella
Where available, the most commonly used device for hemodynamic support in high-risk PCI is the Impella CP device .
Contraindications to Impella device use are: (1) mechanical aortic valve, (2) left ventricular thrombus, (3) severe aortic regurgitation, and (4) atrial or ventricular septal defect.
14.1.4
Femoral access
The Impella CP device requires insertion of a 14 French sheath, which in turn requires iliofemoral arteries >5 mm in diameter without severe calcification, tortuosity, or obstructive lesions. Iliac stenting can sometimes be performed to facilitate insertion of the Impella device (CTO Manual case 145 ) Intravascular lithotripsy can also be used to facilitate insertion of large bore sheaths and catheters through calcified iliofemoral arteries .
14.1.5
Alternative access sites
In case of suboptimal femoral access or in case of failure to advance the Impella CP device, alternative access sites can be considered, such as axillary and transcaval. Both require expertise with large bore access and closure techniques.
14.1.6
Contraindications for VA-ECMO or IABP
- 1.
Severe aortic regurgitation.
- 2.
Aortic dissection.
- 3.
Uncontrolled bleeding (although VA-ECMO and IABP can be used without anticoagulation for a short period of time in patients with active bleeding).
14.1.7
Hypoxemia
In patients with cardiogenic shock and hypoxemia, VA-ECMO is used as it can support both oxygenation and circulation.
14.1.8
Right ventricular failure
Right ventricular function can be assessed using echocardiography (may not be immediately available in the cath lab) or using invasive hemodynamics (right atrial pressure >12 mmHg or Pulmonary Artery Pulsatility Index [PAPI]<0.9) .
PulmonaryArteryPulsatilityIndex(PAPI):=sPAP−dPAPRA
sPAP=systolic pulmonary artery pressure
dPAP=diastolic pulmonary artery pressure
RA=right atrial pressure
In patients with cardiogenic shock and isolated RV failure without LV failure, right ventricular support devices may be used, such as the Protek Duo and Impella RP.
In patients with cardiogenic shock and biventricular failure, VA-ECMO is usually used, although a combination of a left and a right ventricular support device can also be used.
14.1.9
Left ventricular failure
In preshock patients (cardiac index >2.0 L/min/m 2 ), use of IABP may suffice, although continuous hemodynamic monitoring, ideally with a Swan Ganz catheter, is needed to determine the need for escalating support.
In shock patients with isolated severe LV failure the Impella CP device is most commonly used (Tandem Heart can be used at centers experienced in its use).
In patients with LV failure and refractory shock (continued hypoperfusion) despite Impella CP or Tandem Heart use, escalation to VA-ECMO or Impella 5.0 may be required. The Impella is often left in place to provide left ventricular unloading (LV venting) during VA-ECMO support.
14.2
Hemodynamic support: device comparison
Four devices are currently available in the US for providing percutaneous left ventricular hemodynamic support: the intraaortic balloon pump (IABP), the Impella (2.5, CP, and 5.0, Abiomed Inc, Danvers, Massachusetts), the Tandem Heart (Liva Nova, Pittsburgh, PA), and veno-arterial extracorporeal membrane oxygenator (VA-ECMO) ( Fig. 14.2 , Table 14.1 ) . Two devices are available for right ventricular support, the Protek Duo (Liva Nova) and the Impella RP (Abiomed).
| IABP | Impella | Tandem Heart | VA-ECMO | |
|---|---|---|---|---|
| Feasibility | ||||
| Availability | +++ | ++ | + | + |
| Arterial access size required | 7–8 French | 12 French (Impella 2.5) | 15–19 French arterial | 15–19 French arterial |
| 14 French (Impella CP) | 21 French venous | 21–25 French venous | ||
| 21 French (Impella 5.0) | ||||
| Contraindications |
|
|
| |
| Efficacy | ||||
| Cardiac output increase (L/min) | 0.3–0.5 | ≈2.5 (Impella 2.5) | 4–5 c | 4–5 c |
| ≈3.5 (Impella CP) | ||||
| ≈5.0 (Impella 5.0) | ||||
| Affected by arrhythmias | Yes | Yes | Yes | No |
| Requires adequate right ventricular function | Yes | Yes | Yes | No |
| Can correct respiratory failure | No | No | Yes d | Yes |
| Complications | ||||
| Risk of lower limb ischemia | + | ++ | +++ | +++ |
| Transseptal puncture required | No | No | Yes | No |
| Risk of bleeding | + | ++ | ++ | ++ |
| Risk of hemolysis | + | ++ | ++ | ++ |
| Risk of stroke | ++ | ++ | ++ | +++ |
| Difficulty of insertion | + | ++ | ++++ | ++ |
a Except as bridge to surgery.
b Transcaval access can be used for placing the arterial cannula in case of severe peripheral arterial disease.
c Depending on arterial cannula size.
Intraaortic balloon pump (IABP) is the smallest device but also supplies the least hemodynamic support. IABP is usually inserted percutaneously through a 7–8 French femoral arterial sheath. The IABP mechanism of action is inflation of a balloon with helium in the aorta during diastole, increasing coronary perfusion, displacing blood peripherally and increasing cardiac output, while reducing left ventricular end-diastolic pressure and reducing afterload.
The Impella is a non-pulsatile axial flow pump that is advanced through the aortic valve and moves blood from the left ventricle into the aorta. Use of the Impella results in left ventricular unloading with reduction in left ventricular end-diastolic pressure and volume. The Impella is available in two percutaneous types (2.5 and CP), and one type that requires surgical cut down (5.0).
The Tandem Heart is a centrifugal pump that propels blood from the left atrium into the femoral artery. It uses a 21 French cannula placed through a transseptal puncture and a 15–19 French arterial cannula. With an appropriately sized arterial cannula, full perfusion can be achieved. The Tandem Heart requires continuous monitoring to prevent displacement of the transseptal cannula into the right atrium. In isolation, the Tandem Heart does not oxygenate the blood, but an oxygenator can be placed into the circuit to allow full cardiopulmonary support.
VA-ECMO consists of a centrifugal, non-pulsatile pump that circulates the blood and has a membrane oxygenator. Venous blood is aspirated through a venous cannula, advanced through the oxygenator and returned to the patient through an arterial cannula. Similar to Tandem Heart, VA-ECMO requires large size cannulae and a perfusionist to manage the system. VA-ECMO can generate adequate flows to maintain systemic perfusion, but also increases myocardial oxygen demand due to increase of left ventricular end diastolic pressure and volume, that could adversely impact myocardial recovery .
The Protek Duo dual-lumen cannula ( Fig. 14.3 , available in 29 and 31 French sizes) contains two lumens. The inflow lumen has several inflow vents across the superior vena cava and the right atrium and drains blood into an extracorporeal centrifugal pump that delivers blood through the outflow lumen into the main pulmonary artery bypassing the right ventricle.
The Impella RP device can provide right ventricular support by pumping blood from the inferior vena cava to the pulmonary artery and consists of a 22 French motor mounted on an 11 French catheter.
14.3
IABP insertion: step-by-step
14.3.1
Step 1: Obtain femoral access
Goal : Safely obtain arterial access to insert the IABP
How ? As described in Chapter 4 : Access. The femoral sheath is provided with the IABP kit.
14.3.2
Step 2: Prepare IABP for use
Goal : Prepare IABP for insertion and use.
How ?
- 1.
Select IABP size (usually done by height, Table 14.2 ).
Table 14.2
Intraaortic balloon pump size selection.
30 cc
40 cc
50 cc
Height
147–162 cm
162–182 cm
>182 cm
4′10″–5′4″
5′4”–6′0”
>6′0″
- 2.
Attach one-way valve to the gas lumen (do not remove until IABP is in position in the aorta).
- 3.
Use the provided syringe to apply vacuum off the IABP helium lumen. The syringe is then removed, while keeping the one-way valve in place.
- 4.
Remove the IABP catheter from the tray (immediately prior to insertion).
- 5.
Remove stylet from IABP catheter wire lumen.
- 6.
Flush IABP wire lumen with normal saline.
- 7.
Connect fiber-optic cable to the console and zero fluid transducer.
14.3.3
Step 3: Advance guidewire to aortic arch
Goal : Advance IABP guidewire (0.025 inch, provided in the IABP kit), over which the IABP will be inserted.
How ? IABP wire is advanced under fluoroscopy to the aortic arch.
Challenges and troubleshooting for advancing the guidewire can be overcome as described in Chapter 5 : Coronary and Graft Engagement.
14.3.4
Step 4: Advance IABP catheter to aortic arch
Goal : Advance IABP catheter to optimal position.
How ? The IABP is advanced under fluoroscopy until the tip of the catheter is at the level of the tracheal bifurcation.
14.3.5
Step 5: Start IABP function
Goal : Initiate IABP function.
How ?
- 1.
The guidewire is removed and the wire lumen is connected to an arterial pressure monitoring system.
- 2.
The helium port is connected with the IABP console.
- 3.
Counterpulsation is initiated.
14.3.6
Monitor IABP function
14.3.6.1. Goal : Ensure IABP optimal functioning.
14.3.6.2. How ( Fig. 14.4 )?
- 1.
Use 1:2 augmentation and ensure that timing of balloon inflation is optimal.
- 2.
Monitor systemic pressure
- 3.
Monitor IABP position.
- 4.
Ensure therapeutic anticoagulation is administered. If anticoagulation cannot be administered, 1:1 augmentation should be used to minimize the risk of thrombus formation on the IABP balloon.
- 1.
