The Impella 5.0 (Abiomed, Inc, Danvers, MA USA) is a 21-Fr microaxial pump based on a 9-Fr catheter. It is capable of producing up to 5 L/min of flow. The left peripheral (LP) model is designed to be inserted peripherally using a vascular cut down while the left direct (LD) model is intended to be placed directly into the ascending aorta via a 10-mm vascular graft. The device straddles the aortic valve with the inflow residing in the left ventricular cavity and the outflow at the level of the sinotubular junction. The pump is managed by a bedside console and intended for short-term use (1 week). The safety, efficacy and clinical applicability of the Impella device in the treatment of acute cardiogenic shock of numerous etiologies has been well documented.1,2 The benefits of the device include the improvement in cardiac output (systemic hemodynamic support). An additional benefit is related to the direct ventricular unloading effect (reduction of left ventricular end diastolic pressure and volume) and includes reducing myocardial oxygen demand, improved coronary perfusion, and infarct size limitation.3
A 52-year-old man presented to an outside institution with chest pain and met criteria for an acute ST elevation myocardial infarction (STEMI). Urgent coronary angiography revealed total occlusion of the left anterior descending (LAD). After successful stent deployment, the patient was unstable and an intra-aortic balloon pump placed. The patient was transferred to our institution for consideration of a left ventricular assist device (LVAD). On admission, the initial cardiac index (CI) was 1.5 L/min/m2 with a systolic blood pressure in the 90s (mm Hg) and a heart rate of 115 beats per minute. The CI increased to 1.8 with the addition of two inotropes. Transesophageal echocardiography (TEE) revealed diffuse hypokinesis of the left ventricle with akinesis of the anterior wall and septum. The ejection fraction was estimated at <25%. Upon reviewing the angiogram, there was evidence of significant iliofemoral atherosclerotic disease which would preclude the peripheral insertion of the Impella device. As no sternotomy was required for cardiac intervention, we elected to proceed with the implantation of the device via a right anterior mini-thoracotomy. This has been our incision of choice for less invasive aortic valve replacement, and we felt the exposure would be adequate.
A 4-cm transverse incision was made in the third intercostal space adjacent to the sternum. The second rib was disarticulated medially. The pericardium was opened, and the origin of the inominate artery was identified. Pericardial stays were used to deliver the aorta. After administration of systemic heparin, a partial occlusion clamp was applied to the right lateral aspect of the ascending aorta and a 10-mm Hemashield graft (Maquet, Rastatt, Gemany) was anastomosed to the aorta. A separate stab incision in the right lower lateral chest wall was used to introduce the Impella device into the chest. The pump was placed into the graft and positioned retrograde into the left ventricle across the aortic valve. Placement was documented with TEE and using the positioning sensor on the catheter. LVAD support was initiated and flows over 4 L/min achieved (CI 2.3 L/min/m2). TEE noted left ventricular decompression and global improvement in function. The second rib was reapproximated and the wound closed (Fig. 1).
Postoperatively, inotropic support was reduced to a minimum. Systemic heparin was used with a target activated clotting time (ACT) of 180 seconds. The patient was extubated on postoperative day 1. By day 3, the patient's cardiac enzymes were normalizing as was his volume status. Flow on the device was decreased incrementally over 24 hours and hemodynamics observed. Transthoracic echo noted global recovery of cardiac function with lesser degrees in the anterior wall and septum. The hemodynamics remained stable. The patient was taken back to the operating room for device removal. The surgical incision was opened, and the device was withdrawn. The graft was divided with a surgical stapler. Intraoperative TEE demonstrated an ejection fraction of 40%. The patient was awakened and extubated. The remainder of the patient's postoperative course was uncomplicated with the exception of a right pleural effusion which required drainage. The patient was discharged home on hospital day 8.
The first generations of VADs have suffered from size limitations and the requirement for invasive implant techniques. This has resulted in an increase in the morbidity and mortality associated with their use and a reluctance for referral by cardiologists, and to implantation by surgeons. As such VADs are often used too late or not at all. One solution has been the development of miniature LVADs suitable for less invasive insertion. The Impella device is a microaxial pump that is small enough to be inserted via a peripheral artery. Femoral insertion is dependent on peripheral vasculature that is of adequate size and quality to accept a 21-Fr device. Also, a cut down is required, and fluoroscopy is recommended as the device is positioned over a wire. Removal requires vascular repair. An additional consideration with this technique is the inability of the patient to be out of bed or ambulatory following placement. Central insertion via sternotomy requires anastomosing a 10-mm vascular graft to the ascending aorta and ∼7 cm between the aortic valve and the graft site. Central placement can be confirmed using TEE without fluoroscopy. Removal is performed via repeat sternotomy.
The standard operative technique for inserting the Impella 5.0 device has been described.4 An alternative placement technique via the right axillary artery has also been reported.5 In this approach, a vascular cut down is performed and a graft sewn to the axillary artery. A wire is introduced into the left ventricle and the catheter advanced. The graft is exteriorized or tunneled to the anterior chest. As with the femoral approach, the diameter of the axillary or subclavian arteries may be insufficient. In addition, there may be a space limitation as the pump traverses the clavicle first rib junction.
Alternatively, the anterior thoracotomy has been shown to be safe and practical in performing various cardiac surgical procedures, and implantation of a VAD via a right thoracotomy has been studied in animals.6 Potential drawbacks to this technique may include inadequate access to the aorta. From our experience with less invasive aortic valve replacement (AVR) procedures, it is clear that when appropriately placed pericardial stay stitches are used, the aorta can be delivered to the wound. The exception may be reoperative cases. An additional limitation may be the inability to position the partial occlusion clamp. While placement of the device without a graft is possible, it is not recommended because securing the catheter and management of the resultant aortotomy may be problematic. If additional space is necessary for clamp placement, the third rib may also be disarticulated providing adequate room. Also, as the aortic root is inaccessible, the ability to manually facilitate positioning is limited and placement of the LD device may be difficult. As with the femoral or axillary approach, the use of the LP device with advancement over a wire will facilitate placement in this setting. The wire may be introduced via the graft, and placement of a wire across the valve does not require manipulation of the aortic root. The use of the shafted instruments designed for less invasive valve surgery may also facilitate this maneuver. This (wire placement) may represent the technique of choice in all nonsternotomy cases.
Advantages with a central insertion technique include that it provides the shortest fixation distance between the insertion site and the aortic valve. This results in the lowest potential for device migration. Also, there are no vessel size limitations or concerns regarding peripheral vascular disease and limb ischemia. Patients can also be freely mobilized. Explantation of the device is simple. As experience with the Impella miniature LVAD grows, the optimal implant technique will become clearer. The right anterior mini-thoracotomy approach is a useful technique that should be considered when evaluating patients for placement of the Impella miniature LVAD.
1. Granfeldt H, Hellgren L, Dellgren G, et al. Experience with the Impella recovery axial-flow system for acute heart failure at three cardiothoracic centers in Sweden. Scand Cardiovasc J.
2. Siegenthaler MP, Brehm K, Strecker T, et al. The Impella Recover microaxial left ventricular assist device reduces mortality for postcardiotomy failure: a three-center experience. J Thorac Cardiovasc Surg.
3. Meyns B, Stolinski J, Leunens V, et al. Left ventricular support by catheter-mounted axial flow pump reduces infarct size. J Am Coll Cardiol.
4. Rossiter-Thornton M, Arun V, Forrest AP, et al. Left ventricular support with the Impella LP 5.0 for cardiogenic shock following cardiac surgery. Heart Lung Circ.
5. Sassard T, Scalabre A, Bonnefoy E, et al. The right axillary artery approach for the Impella Recover LP 5.0 microaxial pump. Ann Thorac Surg.
6. Son HS, Sun K, Hwang CM, et al. Ventricular assist device implantation using a right thoracotomy. ASAIO J.