BACKGROUND
Percutaneous mechanical circulatory support with Impella 5.0 (Abiomed,
Danvers, MA) is increasingly used in the treatment of cardiogenic shock
due to its effectiveness, userfriendlyness and the relatively easy
management in the ICU.1,2 However, the displacement of
Impella devices secondary to patient movement or transportation is a
known complication.3,4
Dislodgement of Impella can lead to migration of the device deep into
the ventricular cavity or out into the aortic root with subsequent
failure of ventricular unloading. Device repositioning is
resource-intense, requiring a hybrid operating room or catheterization
lab and a multidisciplinary team with close cooperation between trained
ICU physicians, nursing staff and cardiologist.5 Also,
improper Impella positioning can result in hemolysis related to
increased shear stress and mechanical irritation of adjacent cardiac
structures such as papillary
muscles.
We report a case of successful bedside repositioning of an Impella 5.0
without guidewire under TEE guidance, facilitated by rapid ventricular
pacing to cross the aortic valve. To the best of our knowledge this is
the first time that this technique is reported.
CASE PRESENTATION
A 70-year-old man was
re-hospitalized one month after initially suffering an anterior
non-ST-elevation myocardial infarction (NSTEMI) with pulmonary edema.
Coronary angiography revealed severe left main and triple vessel
disease, and echocardiography showed severe left ventricular dysfunction
with ejection fraction (EF) of 32%.
Therefore, the patient underwent coronary artery revascularization using
off-pump coronary artery bypass grafting (OPCABG). General anesthesia
was induced using propofol-remifentanil target-controlled infusion and
off-pump three-vessel CABG surgery was performed. The patient was
hemodynamically unstable during the procedure and received inotropes and
vasopressors (dobutamine 5 mcg /kg/min, norepinephrine and adrenaline
0.1 mcg/kg/min). Given the improving clinical conditions with stable EF,
pharmacological therapy was gradually reduced in the postoperative
period.
On postoperative day (POD) 2, the patient developed atrial fibrillation
with high ventricular rate, not responsive to any treatment, resulting
in a low cardiac output state with increasing lactate levels. The EF
rapidly worsened, and the patient was taken to the cardiac
catheterization laboratory for insertion of an Impella 5.0. The Impella
was positioned through a 10-mm Dacron graft anastomosed end-to-side to
the right common femoral artery. The position of device was confirmed by
fluoroscopy. The patient was then transferred in ICU. Following
transfer, the Impella system failed with a rapid hemodynamic
deterioration of the patient. The cardiology team performed a bedside
TEE to check the device position. TEE showed migration of the Impella
distal tip into the ascending aorta (Fig. 1).
Repositioning of the device was attempted at bedside under TEE guidance.
However, the biggest challenge was to pass the device through the aortic
valve without a guidewire. To overcome this challenge, we used a
procedural step usually employed during transcatheter valvuloplasty.
With the epicardial leads left in place after the operation, rapid
ventricular pacing to 200 bpm was induced to keep the aortic valve
almost motionless and in a “systolic” position. The Impella was then
directed through the aortic valve and advanced into the left ventricle.
The procedure was easy and fast, the position of the Impella was rapidly
optimized and support resumed with maximal flow (Fig. 2). Impella 5.0
was weaned after 8 days of optimal support without any other
complications. TEE performed after removal showed no any aortic valve
damage.
DISCUSSION AND CONCLUSIONS
The increased adoption of percutaneous ventricular assist devices in the
current era may be supported with a series of “tips and tricks” based
on clinical experience. While the use of Impella devices is increasing,
complications such as hemolysis and ventricular tachycardia are being
reported. An important requirement for prolonged optimal hemodynamic
support with Impella is therefore optimal ICU management and
positioning.
The Impella 5.0 is a microaxial pump that works based on the principle
of an Archimedes’ screw. It is a transvalvular pump positioned across
the aortic valve that propels blood from the left ventricle into the
ascending aorta. The pigtail located at the distal tip of the cannula
aids in stabilizing the catheter in the correct position. Impella 5.0 is
inserted via the femoral or axillary artery surgically using a side
graft anastomosed to the artery. In this case femoral artery was used
due to technical problems in approaching the axillary artery (obesity
and diffuse supra-aortic vessels atherosclerosis). The Impella is placed
in the catheterization laboratory under fluoroscopy or in the hybrid
operating room, if available. Evaluation of Impella position can be
performed using bedside TEE, and we report safe repositioning given the
adequate visualization of Impella in relation to cardiac structure such
as mitral sub-valvular apparatus or the aortic valve.6Typically, the patient is brought back to the catheterization laboratory
or a hybrid operating room, and the Impella is advanced over a guidewire
to cross the aortic valve.
In the present case, the guidewire was no longer in place, a hybrid
operating room was not available, and the patient’s clinical condition
deteriorated rapidly. The on duty team identified the challenge of
crossing the aortic valve and decided to use the technique of rapid
pacing to keep the aortic valve almost “motionless”. Following this
approach, the pigtail and cannula were introduced in the left ventricle
without a problem or injury to the aortic valve, as confirmed by TEE
(Fig. 2). The final positioning was confirmed on TEE with the inlet of
the device located in the left ventricle about 3.5 cm below the aortic
valve.
We acknowledge that this trick of repositioning a dislodged Impella 5.0
cannot be routinely employed in the clinical situation, given the risk
of rapid ventricular pacing and LV wall or aortic valve damage. This is
the first described case at our institution where an Impella 5.0 was
successfully repositioned across the aortic valve without a guidewire at
bedside under TEE guidance, and to our knowledge the first reported case
in the literature using this technique.
In case of accidental Impella dislodgement and fast deterioration of
patient’s hemodynamic status, rapid pacing may be an option to “open”
the aortic valve safely, thus aiding in placement of Impella 5.0 through
the aortic valve into the left ventricle. In case of epicardial leads
absence a transvenous temporary pacing lead can be positioned without
fluoroscopy but the “time consuming” must be evaluated.