The overall goal of this procedure is to expeditiously restore cardiac output in patients with biventricular failure and to resuscitate or maintain end organ function. For subsequent plantation. The total artificial heart or TAH is operatively implanted into the patient during the implant.
The pericardial space must be maintained and protected for subsequent sternal reentry and transplantation. In the final step, the cardiac output is maximized for resuscitation, end organ perfusion is maintained and the patient is aggressively rehabilitated while they await transplantation. Ultimately, implantation of the TAH is used as a bridge to transplantation in patients with severe biventricular failure or other complex pathology that may preclude isolated left ventricular support.
The main advantage of the total artificial heart over left ventricular assist devices is the TAH allows for high flow biventricular support, as well as the ability to treat a wide range of complex cardiac pathology that may not be ideally treated with isolated left ventricular support. The patient is a 60-year-old male with hypertrophic cardiomyopathy. He has developed progressive heart failure symptoms over the past 10 years with recent multiple readmissions for decompensated heart failure despite chronic IV milrinone.
His PMH is notable for atrial arrhythmias, status post ablation, recurrent pulmonary embolism, pulmonary hypertension, left atrial thrombus, and prior stroke with no residual deficits. Cardiopulmonary exercise testing demonstrated a low maximal oxygen consumption. Preoperative hemodynamic testing on milrinone demonstrated low cardiac output and pulmonary hypertension with elevated filling pressures.
Echocardiography demonstrated concentric LV hypertrophy with moderate to severely reduce systolic function, a large left atrial thrombus in the appendage and possible LV thrombus. Due to his restrictive myopathy and small LV cavity, he was considered to be a poor candidate for isolated left ventricular assist device. Preoperative CT demonstrated a thoracic dimension measured from the spine to the 10th thoracic vertebrae of greater than 10 centimeters, which allows adequate space for the device.
The SynCardia total artificial heart is the only FDA approved total artificial heart in clinical use. Total volume displacement is around 400 milliliters. The device consists of two polyurethane ventricle chambers, each with a maximum stroke volume of about 70 milliliters and two tilting disc valves to direct blood inflow and outflow.
Each chamber is also pneumatically driven by a separate drive line connected to a driver externally. To prepare the device for surgery, first seal the Dacron aortic and pulmonary grafts with CSE, surgical sealant, and then soak the grafts and devices in Rifampin. After performing a routine chest and abdomen cardiac surgery prep and a median sternotomy medially, divide the left diaphragm and then dissect underneath the posterior rectus fascia, creating a left upper abdominal peritoneal pocket.
Next, make two two centimeter incisions, five centimeters apart below the left costal margin through the rectus fascia, and then create intramuscular tunnels for the pneumatic drive lines by incising the skin and fascia and passing a clamp through the rectus muscle into the mediastinum. Maintain the tunnels with two one inch Penrose drains. Hein is administered for cardiopulmonary bypass.
Cannulate the aorta, minimize unnecessary dissection and mobilization within the pericardium to preserve tissue planes for subsequent heart transplantation. Then cannulate the superior and inferior vena CVA through the right atrium. Flood the surgical field with carbon dioxide to minimize air embolization.
Cross clamp the aorta, divide the aortic root and the main pulmonary artery just above the valve commissures. Start the excision of the right ventricle along the acute margin, one to two centimeters distal and parallel to the atrial ventricular groove. Continue the incision anteriorly into the right ventricular outflow tract.
Divide the intracardiac portion of any defibrillator and or pacing wires and allow them to retract into the superior vena cva. Incise the interventricular septum to open the left ventricle. Similarly, extend the left ventricular incision laterally parallel to the atrial ventricular groove and into the left ventricular outflow tract.
Then divide and remove the remaining interventricular septum. Inspect the right atrium through the tricuspid valve, specifically looking for a patent foramen valle. If necessary, close any patent foramen Valle with three T proline to prevent intraatrial shunting.
Similarly overs, so the orifice of the coronary sinus with three T proline excise the tricuspid valve leaflets leaving a several millimeter cuff to the annulus. Similarly excised the mitral valve leaflets, again, leaving several millimeters to the annulus. This patient was known to have a large atrial thrombus and the left atrial appendage was amputated with a seam guard reinforced endo, GIA stapler trim the left and right ventricular cuffs, leaving a one centimeter rim of tissue over, so the cuffs with two aut proline sutures for hemostasis and to reduce the orifice size to match the TAH atrial quick connects the left and right TAH atrial quick connects are trimmed to 0.5 to one centimeter.
Invert the atrial quick connects and sew them to their respective left and right ventricular cuffs. Reinforce the anastomosis with additional two OTT proline. Note that a common area for leak is at the corners of the interventricular septum, which is also reinforced.
Trim the aortic graft quick connect to about two centimeters. Trim the pulmonary graft. Quick connect to leave it several centimeters longer than the aortic graft to allow room for the aortic graft to pass below.
Sew the pulmonic graft to the pulmonary artery, then sew the aortic graft to the aorta. Now line the pericardium to facilitate reentry and reduce blood loss during subsequent explan for transplantation. Tack a Gore-Tex sheet to the left lateral pericardium prior to connecting the pump as access to this space afterwards will be limited.
Place a strip of Gore-Tex in the transverse sinus to help protect the right pulmonary artery during reentry for transplant. Pass a 13 millimeter Hagar dilator through the Penrose drains to dilate the tract and help guide the pneumatic drivelines through the abdominal wall. Ligate the D airing nipples on the TAH left and right ventricles suction and irrigate the left and right atrium to ensure no residual embolic debris.
Use two heavy needle drives to grab the pliable quick connects and stretch them over the hard plastic connectors of the artificial ventricles to tightly connect the ventricles to their respective orifices. Then place an aortic root vent. Replace the original metal connectors of the external console driveline with plastic connectors.
That will also connect with the portable discharge driver. Connect the large male connector to the left or red big blue driveline tubing and the large female connector to the right or blue. Big blue driveline tubing.
Reinforce the connections with plastic zip ties. Initiate low rate. Low pressure pumping for ding.
Flow through the right side is initially passive resume lung ventilation, and then remove the cross clamp. Despite the limited visualization provided by TEE, it remains a useful modality to assess ding and unobstructed caval and pulmonary venous return to the atria. Similar to normal physiology, TAH output is sensitive to changes in preload, afterload and contractility or pneumatic ejection.
The pneumatic airflow and pressure within the left and right artificial ventricles are displayed graphically on the console here. Typical early initial TAH parameters are shown. The left drive pressure is typically between 180 to 200 millimeters of mercury.
Note that the pneumatic drive pressure is measured at the console and does not reflect the actual blood pressure generated. Once the artificial ventricle has fully ejected. Further pressurization of the artificial ventricle is not transmitted to the patient.
The right drive pressure is typically between 30 and 60 millimeters of mercury. Patients with biventricular failure often have an elevated pulmonary vascular resistance. While increasing the right drive, pressure can overcome the resistance.
Higher drive pressures increases the risk for significant pulmonary edema. The heart rate should be between 100 and 120 beats per minute. The percent systole should be 50, and the vacuum should be left at zero until the chest is sealed.
To reduce and training air once sealed, increase the vacuum to about 10 to 15 millimeters of mercury to improve the ventricular filling, and thus the cardiac output remove the cannulas and administer protamine to reverse the heparin anticoagulation. Once hemostasis has been obtained and the chest is ready to be closed line the remainder of the pericardium with Gore-Tex preclude membrane, the TAH can compress the vena CVA or pulmonary veins and obstruct inflow. This is particularly true of the IVC and left pulmonary veins if necessary.
Place a heavy suture around the artificial right ventricle and secure it to the left costal margin. Reinforce anastomotic connections with coe. The centrally placed TAH does not maintain the normal pericardial space.
Place a smooth saline breast implant filled with 200 to 250 milliliters of saline at the apex. To maintain the pericardial space for a subsequent transplant. Place a strip of scholastic beneath the sternum to protect the pump during reentry for transplantation.
Close the chest with interrupted steel wire, followed by routine multilayer closure of the fascia subcutaneous tissue and skin. From April, 2006 through July, 2012, 66, patients were implanted with a TAH at Virginia Commonwealth University Medical Center. Patients were critically ill.
18%were on other mechanical support. 58%were on an intraaortic balloon pump. 58%were on inotropic medications.
17%were mechanically ventilated, and 17%were on hemodialysis. The patients were supported for a total of 7, 863 days, and the median duration of support was 87.5 days ranging from one to 602 days. 10 patients were discharged home on a portable discharge driver.
As part of a clinical trial, 50 patients were successfully bridged to transplantation. Seven remained on the device awaiting transplantation, and nine died while on the device. Three of the deaths occurred in the first week following implantation of the device and were related to progressive multi-system organ failure.
The other six deaths occurred from 32 to 169 days post-implant, three from sepsis, one from mediastinal bleeding, one from intracranial hemorrhage, and one from hypertensive crisis. The most frequent perioperative adverse event was bleeding, which required mediastinal re exploration in 30%of the patients Since the JARVIK seven was first introduced in the 1980s. Overall implantation implantation techniques for the TH have not changed significantly.
However, refinements in the current generations in cardiac TAH patient selection management of the pericardial space, as well as perioperative management of the patients have led to a marked improvement in patient outcomes.
