Fig. 6.1
The left ventricular (LV) apex is reflected in a cephalad direction to expose the diaphragmatic surface of the heart. The LV cavity is outlined by the dotted line, and the enclosed crosshair depicts “Frazier’s point,” the optimal location for transdiaphragmatic insertion of the inlet cannula (Modified from Gregoric ID et al. [6])
Next, the Silastic inflow cuff is secured in the standard fashion, using 12 pledgeted, full-thickness horizontal mattress sutures placed circumferentially around the coring site. Hemostasis around the inflow cannula is bolstered by using a large-caliber monofilament suture to place a full-thickness purse-string stitch through the pledgeted ring.
After a diaphragmatic myotomy has been created to correspond to the selected coring site, the inlet cannula is then guided through the diaphragm, inserted within the Silastic ring, and secured in place with two ratcheting cable ties. Proper orientation of the device is achieved by first pulling the pump housing into the abdomen until the heart lies flush with the diaphragm and then positioning the outflow graft to course above the left lobe of the liver. Our preference is to wrap the body of the pump in available omentum to protect the bowel from erosive injury.
The outflow graft then is measured and bevel cut with enough length to allow a gentle curve toward the right side of the chest without excessive redundancy. The outflow anastomosis is then performed in a standard end-to-side fashion with the aid of a partial occluding clamp along the ascending aorta. After externalization of the driveline, the system is thoroughly de-aired by using a 19-gauge needle placed at the highest point of the outflow graft. Cardiopulmonary bypass flows are gradually decreased, the heart is allowed to fill, and the pump is started at its lowest setting (6000 rpm). The patient is weaned from CPB, which is eventually terminated with the aid of transesophageal echocardiographic guidance to allow optimization of LVAD speeds, chamber size, interventricular septal position, and right ventricular function.
Once proper function and orientation are verified, protamine is administered, the CPB cannulas are removed, and drains are placed in the mediastinum and pleural spaces. The bare portion of the outflow graft is covered with a 20-mm-diameter ringed Gore-Tex graft (Gore Medical, Newark, DE) to prevent kinking and damage during future sternal reentry. The defect in the diaphragm is partially reapproximated, and the sternum and soft tissues are closed in the standard fashion.
Discussion
Early in the development of MCS , inflow cannulation was performed through the LV apex to accommodate lengthy inlet-cannula designs . Although inlet conduits were eventually shortened in response to excessive inflow-graft occlusion seen in experimental testing, device implantation techniques changed little over time [4]. As a result, apical cannulation became standard practice after widespread adoption of the HeartMate XVE LVAD (Thoratec Corp.). Although care had to be taken at the time of implantation to avoid mechanical inlet obstruction, few complications arose from this orientation because of the obligatory preservation of a ventricular reservoir with pulsatile devices. Familiarity with this implantation technique resulted in its subsequent application to CF LVADs―a practice bolstered by the inclusion of an inlet cannula identical to that of the HeartMate XVE in the design of the HeartMate II. However, the unique physiology associated with CF technology necessitates consideration of specific anatomic and mechanical challenges associated with the use of these pumps.
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