Replacement of Paracorporeal Ventricular Assist Devices Douglas P. Lohmann, ME, Lawrence R. McBride, MD, D. Glenn Pennington, MD, and Marc T. Swartz, BA Department of Surgery, St. Louis University Medical Center, St. Louis, Missouri
In this communication we describe a technique to change paracorporeal ventricular assist devices after the development of mechanical complications. This procedure is technically simple and in our experience does not require a sternotomy or cardiopulmonary bypass. Paracorporeal ventricular assist devices can be safely changed allowing continued support and survival. (Ann Thorac Surg 1992;54:1226-7)
B
etween February 1988 and February 1992, 30 patients received investigational pulsatile ventricular assist devices (VADs) at St. Louis University. During this same period 4 patients required VAD replacement due to device-related problems. These patients had paracorporeal VADs of the Pierce-Donachy design [l](Thoratec Laboratories Corp, Berkeley, CA, and Sarns/3M, Ann Arbor, MI). There were 3 men and 1 woman ranging in age from 28 to 54 years (mean, 44 years). Two patients required VAD insertion after development of acute myocardial infarction shock, and the condition of 2 patients with cardiomyopathy (idiopathic, 1, and postpartum, 1) deteriorated while they were awaiting cardiac transplantation. The duration of support ranged from 52 to 89 days (mean, 69 days). The circumstances necessitating replacement of the VADs were varied and included severe hemolysis, a ruptured blood sac, destruction of the outer pump casing, and partial cannula obstruction. Ventricular assist device replacement occurred 6, 35, 45, and 79 days after insertion. Three of the 4 patients were ambulatory at the time of replacement. The first patient had severe hemolysis (serum hemoglobin level, 1.15 g/L) due to a previously unrecognized flaw in the design of the VAD valve housing clearances. The hemolysis was corrected within 12 hours by replacing the Sarns VAD with another more established VAD (Thoratec) of similar design. This man's heart recovered after 53 days of support, and he was weaned from the VAD and discharged from the hospital. The second patient is a 28-year-old woman who had a ruptured blood sac. This tear was due to an error in the quality control procedures on the part of the manufacturer. On the 45th day after left VAD implantation a large Accepted for publication July 28, 1992. Address reprint requests to Mr Lohmann, Department of Surgery, St. Louis University Medical Center, 3635 Vista Ave at Grand Blvd, St. Louis, MO 63110.
0 1992 by The Society of Thoracic Surgeons
thrombus appeared and was believed to be located within the blood sac. The thrombus did not interfere with VAD function and the patient remained in hemodynamically stable condition. After the VAD was removed, replaced, and disassembled the clot was found to be located between the blood sac and the rigid pump housing. Blood had leaked from the blood sac into this space through a small tear and clotted. During VAD replacement it appeared that native heart function had substantially improved; 9 days later the patient was weaned from the assist device and soon thereafter discharged. The third patient was a 46-year-old man with biventricular assist devices who required replacement of both pumps when acetone destroyed the outer pump casings [2]. The acetone did not come in direct contact with the VADs but was used to remove tape residue from an area adjacent to the devices. Acetone vapors, even in trace amounts, can cause fractures in polysulfone plastics and therefore should not be used in the vicinity of these materials. The last patient had decreasing flows (1.9 L/min) through his right VAD. ThiG(prob1em was presumed to be mechanical in nature; however, upon inspection of the removed right VAD, the valves were functioning properly with no obstructions and the Hall effect switch was operating correctly. A new VAD was connected, but there was no improvement in flow. The sternotomy was reopened and the right VAD removed. Because right heart function had recovered substantially only low-dose isoproterenol was necessary. It appeared that the lighthouse tip of the right atrial cannula had been intermittently and partially occluded by right atrial tissue. This man was successfully supported with the left VAD until a suitable donor heart was found; he was subsequently discharged after transplantation. Technique After the induction of general anesthesia, adequate intravenous lines are placed for drug delivery and volume replacement. An arterial line and a Swan-Ganz catheter are inserted; the patient is then anticoagulated with heparin (1 mg/kg). As the VAD to be replaced is not sterile, extreme diligence should be taken to ensure that the VAD and the cannulas are as clean as possible. To do this povidone-iodine solution is applied to all VAD surfaces, and the surfaces are wiped dry with sterile towels and then resprayed with povidone-iodine. All surfaces should still be considered contaminated, and separation of sterile 0003-4975/92/$5.00
HOW TO DO IT LOHMANN ET AL REPLACEMENT OF VADs
Ann Thorac Surg 1992:54:1226-7
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pulmonary bypass. The exchange of pumps took less than 30 minutes in all cases. Two patients were extubated within 24 hours, 1 received a cardiac transplant 24 hours after VAD replacement, and the remaining patient was extubated 13 days later. All patients survived the procedure without complications. One patient died 54 days later of unrelated complications, and 3 were discharged. Of the 3 survivors 1 received a cardiac transplant and the other 2 were weaned from the VAD after cardiac recovery. As of June 1992 the 3 survivors are doing well (New York Heart Association functional class I) and have survived an average of 2 years after VAD removal. Fig 1 . Removal of air from the replacement ventricular assist device.
and nonsterile fields should be maintained as much as possible. In addition, prophylactic antibiotics should be given to all patients undergoing this procedure. The VAD is halted and the cannulas are clamped. If necessary, administration of inotropic drugs is started to maintain adequate perfusion. If the heart is unable to support the circulation, VAD pumping should resume until cardiopulmonary bypass can be instituted. Femorofemoral cardiopulmonary bypass may be used to avoid reopening the sternal incision. With both the VAD inflow and outflow cannulas clamped, the old VAD is removed. The new VAD is then connected to the VAD inflow cannula. The VAD inflow cannula is slowly unclamped, allowing the blood sac to fill with blood. The VAD inflow cannula is reclamped. When the blood sac is nearly full of blood and evacuated of air, the VAD is partially connected to the VAD outflow cannula (Fig 1).Heparinized normal saline solution is then squirted on the connection while the outflow cannula and VAD are joined. The VAD is inspected to assure that all air is completely removed before the connections are tightened and VAD operation resumed.
Results All of these patients received heparin during the exchange, and 3 received protamine at the end of the procedure. Two patients were receiving only dextran (25 mL/h) in the period before VAD replacement, and the remaining 2 were receiving a combination of warfarin (prothrombin time, 1.5 times control) and aspirin or warfarin and dipyridamole. There was no significant difference in the preoperative and postoperative activated partial thromboplastin time or prothrombin time. Transfusions averaged five units of packed red blood cells per patient. One patient required six units of packed red blood cells to replace blood lost before this procedure from a subclavian vein perforation. The patient who had his right VAD removed through a sternotomy received seven units of packed red blood cells in part to raise his right atrial pressure and increase left VAD output. We believe that patients without other complications should require little or no blood products. Inotropic drugs were necessary for a short period during the exchange in 3 patients; however, none of these patients required cardio-
Comment Most of the circumstances that would require VAD replacement can be avoided by meticulous manufacturing quality control and care for these devices. However, should the necessity arise due to clinical needs, replacement remains a reasonable option. Although there are some limitations to this VAD design, the ability to replace it without much difficulty is encouraging. It is possible to exchange VADs without the need for cardiopulmonary bypass. Minimal additional anticoagulation is required to avoid thrombus formation during the brief period while the blood is stagnant in the cannulas. Inotropic drugs may be necessary for a short time (30 minutes) during the exchange of the VADs. As the periods of VAD support increase, the amount of time that external VADs are exposed to potentially harmful environmental factors also increases. Some of those dangers have been identified in the ongoing clinical trials, such as our experience with acetone. As experience grows we can expect to see more complications such as those mentioned in this article. These devices were designed and tested for durations of support of less than 14 days. They certainly are versatile and have proved themselves capable of much longer periods of support (225 days, University of Pittsburgh; R. Kormos, personal communication, May 1992). Only one of these complications could have been avoided by the use of an implantable VAD, the acetone incident. Blood sac perforation, cannula obstruction, and hemolysis could have just as easily occurred with an implantable pump; however, the resolution of the problem would have been considerably more difficult. As clinical experience grows, complications associated with these devices will continue to be identified. The ability to replace temporary paracorporeal pneumatic pumps without surgical intervention should be considered a noteworthy asset.
References 1. Donachy JH, Landis DL, Rosenburg G, Prophet GA, Ferrari 0, Pierce WS. Design and evaluation of a left ventricular assist device: the angle port pump. In: Unger F, ed. Assisted circulation. Berlin: Springer-Verlag, 1979:138-46. 2. Lohmann DP, Pennington DG, McBride LR. Acetone: a hazard to plastic medical p r o d u c t s a case report [Letter]. J Thorac Cardiovasc Surg 1991;102:937-8.
In this communication we describe a technique to change paracorporeal ventricular assist devices after the development of mechanical complications. This procedure is technically simple and in our experience does not require a sternotomy or cardiopulmonary bypass. Paracorporeal ventricular assist devices can be safely changed allowing continued support and survival. (Ann Thorac Surg 1992;54:1226-7)
B
etween February 1988 and February 1992, 30 patients received investigational pulsatile ventricular assist devices (VADs) at St. Louis University. During this same period 4 patients required VAD replacement due to device-related problems. These patients had paracorporeal VADs of the Pierce-Donachy design [l](Thoratec Laboratories Corp, Berkeley, CA, and Sarns/3M, Ann Arbor, MI). There were 3 men and 1 woman ranging in age from 28 to 54 years (mean, 44 years). Two patients required VAD insertion after development of acute myocardial infarction shock, and the condition of 2 patients with cardiomyopathy (idiopathic, 1, and postpartum, 1) deteriorated while they were awaiting cardiac transplantation. The duration of support ranged from 52 to 89 days (mean, 69 days). The circumstances necessitating replacement of the VADs were varied and included severe hemolysis, a ruptured blood sac, destruction of the outer pump casing, and partial cannula obstruction. Ventricular assist device replacement occurred 6, 35, 45, and 79 days after insertion. Three of the 4 patients were ambulatory at the time of replacement. The first patient had severe hemolysis (serum hemoglobin level, 1.15 g/L) due to a previously unrecognized flaw in the design of the VAD valve housing clearances. The hemolysis was corrected within 12 hours by replacing the Sarns VAD with another more established VAD (Thoratec) of similar design. This man's heart recovered after 53 days of support, and he was weaned from the VAD and discharged from the hospital. The second patient is a 28-year-old woman who had a ruptured blood sac. This tear was due to an error in the quality control procedures on the part of the manufacturer. On the 45th day after left VAD implantation a large Accepted for publication July 28, 1992. Address reprint requests to Mr Lohmann, Department of Surgery, St. Louis University Medical Center, 3635 Vista Ave at Grand Blvd, St. Louis, MO 63110.
0 1992 by The Society of Thoracic Surgeons
thrombus appeared and was believed to be located within the blood sac. The thrombus did not interfere with VAD function and the patient remained in hemodynamically stable condition. After the VAD was removed, replaced, and disassembled the clot was found to be located between the blood sac and the rigid pump housing. Blood had leaked from the blood sac into this space through a small tear and clotted. During VAD replacement it appeared that native heart function had substantially improved; 9 days later the patient was weaned from the assist device and soon thereafter discharged. The third patient was a 46-year-old man with biventricular assist devices who required replacement of both pumps when acetone destroyed the outer pump casings [2]. The acetone did not come in direct contact with the VADs but was used to remove tape residue from an area adjacent to the devices. Acetone vapors, even in trace amounts, can cause fractures in polysulfone plastics and therefore should not be used in the vicinity of these materials. The last patient had decreasing flows (1.9 L/min) through his right VAD. ThiG(prob1em was presumed to be mechanical in nature; however, upon inspection of the removed right VAD, the valves were functioning properly with no obstructions and the Hall effect switch was operating correctly. A new VAD was connected, but there was no improvement in flow. The sternotomy was reopened and the right VAD removed. Because right heart function had recovered substantially only low-dose isoproterenol was necessary. It appeared that the lighthouse tip of the right atrial cannula had been intermittently and partially occluded by right atrial tissue. This man was successfully supported with the left VAD until a suitable donor heart was found; he was subsequently discharged after transplantation. Technique After the induction of general anesthesia, adequate intravenous lines are placed for drug delivery and volume replacement. An arterial line and a Swan-Ganz catheter are inserted; the patient is then anticoagulated with heparin (1 mg/kg). As the VAD to be replaced is not sterile, extreme diligence should be taken to ensure that the VAD and the cannulas are as clean as possible. To do this povidone-iodine solution is applied to all VAD surfaces, and the surfaces are wiped dry with sterile towels and then resprayed with povidone-iodine. All surfaces should still be considered contaminated, and separation of sterile 0003-4975/92/$5.00
HOW TO DO IT LOHMANN ET AL REPLACEMENT OF VADs
Ann Thorac Surg 1992:54:1226-7
1227
pulmonary bypass. The exchange of pumps took less than 30 minutes in all cases. Two patients were extubated within 24 hours, 1 received a cardiac transplant 24 hours after VAD replacement, and the remaining patient was extubated 13 days later. All patients survived the procedure without complications. One patient died 54 days later of unrelated complications, and 3 were discharged. Of the 3 survivors 1 received a cardiac transplant and the other 2 were weaned from the VAD after cardiac recovery. As of June 1992 the 3 survivors are doing well (New York Heart Association functional class I) and have survived an average of 2 years after VAD removal. Fig 1 . Removal of air from the replacement ventricular assist device.
and nonsterile fields should be maintained as much as possible. In addition, prophylactic antibiotics should be given to all patients undergoing this procedure. The VAD is halted and the cannulas are clamped. If necessary, administration of inotropic drugs is started to maintain adequate perfusion. If the heart is unable to support the circulation, VAD pumping should resume until cardiopulmonary bypass can be instituted. Femorofemoral cardiopulmonary bypass may be used to avoid reopening the sternal incision. With both the VAD inflow and outflow cannulas clamped, the old VAD is removed. The new VAD is then connected to the VAD inflow cannula. The VAD inflow cannula is slowly unclamped, allowing the blood sac to fill with blood. The VAD inflow cannula is reclamped. When the blood sac is nearly full of blood and evacuated of air, the VAD is partially connected to the VAD outflow cannula (Fig 1).Heparinized normal saline solution is then squirted on the connection while the outflow cannula and VAD are joined. The VAD is inspected to assure that all air is completely removed before the connections are tightened and VAD operation resumed.
Results All of these patients received heparin during the exchange, and 3 received protamine at the end of the procedure. Two patients were receiving only dextran (25 mL/h) in the period before VAD replacement, and the remaining 2 were receiving a combination of warfarin (prothrombin time, 1.5 times control) and aspirin or warfarin and dipyridamole. There was no significant difference in the preoperative and postoperative activated partial thromboplastin time or prothrombin time. Transfusions averaged five units of packed red blood cells per patient. One patient required six units of packed red blood cells to replace blood lost before this procedure from a subclavian vein perforation. The patient who had his right VAD removed through a sternotomy received seven units of packed red blood cells in part to raise his right atrial pressure and increase left VAD output. We believe that patients without other complications should require little or no blood products. Inotropic drugs were necessary for a short period during the exchange in 3 patients; however, none of these patients required cardio-
Comment Most of the circumstances that would require VAD replacement can be avoided by meticulous manufacturing quality control and care for these devices. However, should the necessity arise due to clinical needs, replacement remains a reasonable option. Although there are some limitations to this VAD design, the ability to replace it without much difficulty is encouraging. It is possible to exchange VADs without the need for cardiopulmonary bypass. Minimal additional anticoagulation is required to avoid thrombus formation during the brief period while the blood is stagnant in the cannulas. Inotropic drugs may be necessary for a short time (30 minutes) during the exchange of the VADs. As the periods of VAD support increase, the amount of time that external VADs are exposed to potentially harmful environmental factors also increases. Some of those dangers have been identified in the ongoing clinical trials, such as our experience with acetone. As experience grows we can expect to see more complications such as those mentioned in this article. These devices were designed and tested for durations of support of less than 14 days. They certainly are versatile and have proved themselves capable of much longer periods of support (225 days, University of Pittsburgh; R. Kormos, personal communication, May 1992). Only one of these complications could have been avoided by the use of an implantable VAD, the acetone incident. Blood sac perforation, cannula obstruction, and hemolysis could have just as easily occurred with an implantable pump; however, the resolution of the problem would have been considerably more difficult. As clinical experience grows, complications associated with these devices will continue to be identified. The ability to replace temporary paracorporeal pneumatic pumps without surgical intervention should be considered a noteworthy asset.
References 1. Donachy JH, Landis DL, Rosenburg G, Prophet GA, Ferrari 0, Pierce WS. Design and evaluation of a left ventricular assist device: the angle port pump. In: Unger F, ed. Assisted circulation. Berlin: Springer-Verlag, 1979:138-46. 2. Lohmann DP, Pennington DG, McBride LR. Acetone: a hazard to plastic medical p r o d u c t s a case report [Letter]. J Thorac Cardiovasc Surg 1991;102:937-8.
