A 65-year-old male with nonischemic cardiomyopathy, recent ventricular tachycardia-induced cardiac arrest, supported by inotropic medications and intraaortic balloon pump, presented for biventricular assist device placement. Preoperative echocardiographic findings showed left ventricular (LV) ejection fraction of 15%, previous mitral valve annuloplasty, moderate-to-severe right ventricular (RV) dysfunction and moderate tricuspid regurgitation (TR). He underwent placement of HVAD (HeartWare International Inc, Framingham, MA), left ventricular assist device (LVAD), percutaneous right ventricular assist device (RVAD), tricuspid valve (TV) annuloplasty, and removal of intraaortic balloon pump. The HVAD was inserted first and the correct position of cannulas was confirmed with transesophageal echocardiography (TEE). The Impella RP (Right Peripheral, Abiomed, Danvers, MA) sheath, followed by microaxial pump were advanced via femoral venous access into the pulmonary artery (PA) under direct surgical visualization of the pig-tailed guidewire in the left PA. Post bypass TEE confirmed LVAD inflow and outflow cannulas in good position, RVAD inlet opening in the inferior vena cava (IVC) and the RVAD outlet opening 2.5 cm distal to the pulmonic valve (PV), and a well-seated tricuspid ring with mild TR and pulmonary regurgitation (PR). Impella RP was seated well in the RV without interfering with papillary muscles, chordae, pacer wires or PA catheter, or displacing the leaflets as it crossed the TV and PV (Figure 1; Supplemental Digital Content 1, Video 1, http://links.lww.com/AA/B883; Supplemental Digital Content 2, Video 2, http://links.lww.com/AA/B884). At the end of the surgery, the patient was left with open chest, on low dose inotropic and vasopressor support, and inhaled epoprostenol. The HVAD flow was maintained 4.6 L/min and the Impella RP flow was 3.6 L/min. On postoperative day 1, the patient presented with systemic hypotension, increased pressor and inotropic support, reduced flows from both devices (HVAD flow 3.2 L/min; Impella 3.2 L/min) and elevated serum lactate. He was taken to the operating room with concern for cardiac tamponade; however, other causes of hemodynamic compromise such as RV failure, LV suck down effect or cannula malposition were considered as well. In addition to a moderate size pericardial effusion, TEE showed severely dilated RV, and underfilled LV with leftward-shifted interventricular septum. The Impella RP outlet was visualized in the proximity of the pulmonic root (Supplemental Digital Content 3, Video 3, Part A, http://links.lww.com/AA/B885). The RV dilation was attributed to moderate PR, as a result of leaflet tenting by the Impella RP. The device was advanced by 2 cm, assuring parallel alignment with the main PA, which resulted in subsequent improvement in the LV filling, return of the interventricular septum position to midline, and noticeable decrease in PR (Supplemental Digital Content 3, Video 3, Part B, http://links.lww.com/AA/B885). Subsequently, the RV systolic function recovered and the Impella RP was removed on postoperative day 6.
RV failure after LVAD placement is defined as inotropic support for at least 14 days or RV mechanical support,1 with 10% of patients requiring temporary mechanical support.2,3 Compared with traditional RVADs which require surgical intervention for placement and reoperation for removal,4 Impella RP is a percutaneous intracardiac device placed over a guidewire under fluoroscopic guidance and allows for chest closure.5 It consists of an S-shaped 23 Fr microaxial pump mounted on an 11 Fr catheter delivering up to 4 L/min blood flow (Figure 2). It provides temporary RV support for patients with acute RV failure secondary to LVAD placement, myocardial infarction, or postcardiotomy. This device is contraindicated in patients with thromboembolic disease involving IVC and pulmonary arteries, and presence of mechanical TV and PV. In our case, since the chest was open for LVAD insertion, the placement technique was modified and pulmonary arteriotomy was performed to help position the pig-tailed guidewire, thus obviating the need for fluoroscopy. In 8% of the patients, Impella RP may not be positioned correctly due to anatomic variations (ie, tricuspid-to-pulmonary valve angle determined by computer tomography). When properly positioned, the outlet opening is located in the mid portion of the main PA, with the pig-tailed wire tip located in the left PA, confirmed by fluoroscopy and chest X ray (Figure 3). TEE can be used to assist placement and to confirm the appropriate position of the cannula, as it was described previously for assessment of other percutaneous RVADs.6 It also provides important information about the hemodynamic effect from preload reduction on the size and geometry of the RV, and the function of the right-sided valves. However, TEE does not allow visualization of the entire catheter assembly, specifically the pig tail in the left PA.7
Several TEE modalities are helpful for Impella RP placement and function assessment (Table). In the IVC long axis view, the inlet opening should be 1 to 2 cm below the diaphragm in the intrahepatic portion of the IVC, where the vein is less prone to collapse from suction event. The assessment of the S-shaped cannula is best performed in midesophageal RV inflow/outflow view. It is important to assess for any interference of the device with TV or PV leaflets, papillary muscles or existing hardware, such as pacing wires and PA catheter. The cannula may cause or worsen TR, although RV decompression decreases its severity. Ultimately, the amount of TR is largely irrelevant in high flows and its quantitative assessment is unreliable because most of the blood flow from IVC bypasses the RV through the device. Similarly unreliable are the interrogation of TV gradient and hepatic venous flow pattern. The Impella RP outlet should be positioned in the main PA 2 to 4 cm distal from the PV, utilizing color-flow Doppler to visualize the blood flow exiting the outlet opening into the main PA. Outlet positioning past the PA bifurcation results in ipsilateral lung hyperperfusion and edema. As in our case, if positioning is close to the PV, it may result in distortion of the PA root, malcoaptation of the PV leaflets, and significant PR. If there is more than mild PR, the cannula position needs to be revised. In our patient, worsening RV dilation coexisted with the outlet opening imaged closer to the PV. Grading PR is challenging in the presence of continuous flow RVAD and may be underestimated in the setting of elevated RV end diastolic pressure. Importantly, the RV is not completely decompressed by the Impella RP, since there is flow from the superior vena cava which flows through the RV and not through the RVAD.
In summary, even though there are no TEE guidelines for Impella RP assessment, TEE provides valuable information for correct positioning of the device and for hemodynamic assessment. While the clinical deterioration in our patient was partly attributed to tamponade, worsened PR and RV dilation contributed to the hemodynamic instability and improved after correct repositioning of the cannula.
Name: Mariya A. Geube, MD.
Contribution: This author helped in the data acquisition and manuscript preparation.
Name: Andrej Alfirevic, MD, FASE.
Contribution: This author helped in the data acquisition and manuscript preparation.
Name: Michael Tong, MD.
Contribution: This author helped with manuscript preparation.
This manuscript was handled by: Nikoloas J. Skubas, MD, DSc, FACC, FASE.
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. Accessed August 16, 2016.
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