Keywords
circulatory-assist devices - myocardial infarction - heart failure - mitral valve
surgery - myocardial infarction
Introduction
A ruptured papillary muscle precipitates cardiogenic shock requiring immediate surgical
intervention. Temporary mechanical circulatory support (tMCS) has increasingly been
used as a bridge to cardiac surgery, which allows the team to safely stabilize the
patient prior to surgery, reduce perioperative mortality, and improve postoperative
recovery.[1]
[2] The Impella 5.5 (Abiomed, Danvers, Massachusetts, United States) is the latest axial-flow
pump device that increases antegrade flow resulting in decreased mitral regurgitation
(MR) and pulmonary congestion. Device support has been described in patients after
post-myocardial infarction (MI) mechanical complications.[3]
[4] However, use of the Impella 5.5 in the setting of a ruptured papillary muscle has
not been reported.
We describe the successful perioperative use of Impella 5.5 for hemodynamic optimization
of two patients in cardiogenic shock after post-MI papillary muscle rupture.
Case 1
A 62-year-old female (body surface area [BSA]: 1.46 m2) presented with dyspnea, lightheadedness, and syncope. She was found to have ST elevations
in the inferior leads, severe MR, and a left ventricular ejection fraction (LVEF)
of 35%. Given advanced shock, she was transferred to our center for urgent tMCS.
The patient was taken to the operating room (OR) for placement of an Impella 5.5.
On intraoperative transesophageal echocardiogram (TEE), a ruptured posterior papillary
muscle was noted. The decision was made to continue with implantation using the right
axillary artery and an 8-mm Gelweave graft (Terumo Aortic, Somerset, New Jersey, United
States). The patient left the OR with a mean arterial pressure of 70 mm Hg on moderate
inotropic support; the Impella was set to P6 with a flow of 3.8L/min. In the intensive
care unit (ICU), the cardiac index improved, urine output increased, and lactate cleared.
After resolution of presenting shock, improvement in end-organ function, successful
diuresis, and completion of goals-of-care discussions, the patient was felt to be
an acceptable operative candidate.
On postoperative day (POD) 2, the patient returned to the OR for a mitral valve replacement
(MVR). A standard sternotomy was performed. The mitral valve was exposed through a
left atriotomy and replaced with a 25-mm St. Jude Epic (Abbott, Chicago, Illinois,
United States) bioprosthetic valve. Postoperative TEE revealed functioning valves
with an LVEF of 35%. The Impella was kept in place for postcardiotomy support and
set to P4 with a flow of 1.7 L/min. The patient was extubated the following morning.
Once perioperative diuresis was achieved and the patient appeared clinically stable,
Impella support was decreased while chemical and vasopressor support was titrated
to maintain a cardiac index > 2.2 L/min/m2. The patient was maintained on minimal mechanical support to prove sufficient cardiac
function prior to Impella removal (POD 6).
Her postoperative course was complicated by pneumonia and subsequent respiratory failure
requiring reintubation and tracheostomy on POD 13. Ultimately, the patient was discharged
to a skilled-nursing facility where she stayed for an additional week before returning
home. She is now doing well.
Case 2
A 65-year-old male (BSA: 2.22 m2) presented to an outside hospital with dyspnea and radiographic pulmonary congestion.
He was initially diagnosed with pneumonia and was placed on veno-venous extracorporeal
membrane oxygenation (VV-ECMO) for profound hypoxic failure. Further workup revealed
a subacute inferior STEMI and cardiogenic shock. Thus, the patient was transferred
directly to the OR for Impella 5.5 placement. Intraoperative TEE showed posterior
mitral valve papillary muscle rupture with torrential MR ([Supplementary Videos S1], [S2]). The Impella was placed and set to P8 with 3.9 L/min of flow and VV-ECMO flow was
set to 4.8 L/min. In the ICU, the patient remained on moderate doses of pressors while
showing signs of improvement in cardiac index (2.23 L/min/m2) and clearance of lactate from 6 to 1.1 mmol/L.
Supplementary Video S1 Intraoperative TEE of ruptured papillary muscle. TEE, transesophageal echocardiogram.
Supplementary Video S2 Intraoperative TEE after Impella placement. TEE, transesophageal echocardiogram.
Following initial clinical stability, elevated pulmonary artery pressures and new
right heart dysfunction were noted. It was felt, given his size, the Impella offered
inadequate forward flow for full right-sided decompression. As such, veno-arterial-venous
ECMO was initiated and the Impella was transitioned to use as a vent on POD 5. The
patient was taken to the OR on POD 7 for an MVR. In standard fashion, a 33-mm St.
Jude Epic valve was implanted. The postoperative LVEF was 25 to 30% with right ventricle
function suitable for arterial decannulation. The patient returned to the ICU on VV-ECMO
and Impella at P8 with 4.8 L/min of flow. The patient continued to improve with a
significant reduction in pulmonary congestion and a return of native cardiac function
noted on subsequent days.
He underwent tracheostomy on POD 21 for prolonged ventilator-dependent respiratory
failure. He was successfully decannulated from VV-ECMO on POD 24, and the Impella
was subsequently removed on POD 26.
The patient developed pseudomonal pneumonia and candida fungemia on POD 29. Despite
prolonged antimicrobial and vasopressor support, the patient progressed to refractory
septic shock. Ultimately, the family requested transition to comfort care, and the
patient expired.
Discussion
MI predisposes the structures supplied by the corresponding coronary vasculature to
further damage in the recovery period. Rupture of the papillary muscle is a rare mechanical
complication that can lead to torrential MR with associated pulmonary edema and shock.[5] It is essential to recognize and intervene to prevent rapid clinical deterioration
and death.
The management of a post-MI complication is challenging given the complex presentation
of cardiogenic shock and severe MR. Thus, a strategy that can offload the LV, decongest
the lungs, and provide sufficient cardiac output is essential. An axial-flow pump
can achieve these clinical goals. The theoretical risk of device thrombosis or embolic
dislocation of debris has not previously been reported. Both patients in this study
were maintained on a heparin drip with a partial thromboplastin time goal of 40 to
50 seconds as well as the standard Impella purge solution. Consistent with existing
literature, no device complications or neurologic deficiencies were seen while on
Impella support.[6] Of note, previous models with longer motor units have caused papillary rupture and
mitral valve damage, but this has not been reported in the Impella 5.5 literature.[7] Therefore, surgical teams should consider isolated Impella as an option for these
patients.
ECMO has been the standard for acutely increasing cardiac output and may have a role
in acute shock following an MI. However, ECMO increases LV afterload resulting in
an increase in LV end-diastolic pressure and associated left atrial dilation and pulmonary
edema.[8] In the setting of torrential MR, these complications are particularly harmful requiring
additional LV unloading. Concomitant use of the Impella with ECMO (ECPella) has been
used to mitigate these ECMO-related complications by increasing forward flow.[3] The quality of support provided by the Impella may depend on the patient's BSA with
the device capturing sufficient cardiac output in smaller patients.[9] In our report, the patient with a BSA of <2.0 m2 was only supported with an Impella, whereas the patient with a BSA of >2.0 m2 required additional ECMO support. Additionally, the Impella, being designed to offload
the LV, may not be sufficient in the setting of biventricular failure. Although the
ECPella can provide significant benefit through hemodynamic stabilization, ECMO use,
and its associated complications, may be avoided by utilizing the Impella in certain
patient populations.
In this case, we report the successful use of Impella 5.5 for preoperative optimization
for MVR in the setting of a ruptured papillary muscle. We discussed the pathophysiology
of post-MI complications as well as the considerations of utilizing the ECPella model.
These cases emphasize the multipurpose use of novel technologies to benefit patients
with varied underlying pathologies. In conclusion, ruptured papillary muscles should
not be seen as a contraindication for axial-flow pump devices.
