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A modified implantation technique of the HeartWare ventricular assist device for pediatric patients
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The Journal of Heart and Lung Transplantation, Vol 34, No 1, January 2015
Limitations to our study include the lack of a control group or a different treatment arm. Owing to recurrent, lifethreatening, and refractory bleeding in these patients, we concluded that withholding a therapy that we had previously shown would benefit these patients would be unethical. We also did not assess the relative effect of thalidomide in reduction of LVAD-associated GIAD compared with other therapeutic agents. Other investigators have used agents, including octreotide, to reduce bleeding due to GIAD in LVAD patients, although octreotide is difficult to tolerate due to its mode of delivery (injection) and adverse effects, including nausea and bradycardia. Lenalidomide, a synthetic analog of thalidomide, has been shown to be as potent as the parent drug, with less of the non-hematologic adverse effects, and is another potential treatment option for these patients. In summary, thalidomide can be used safely in patients with LVAD-associated GIAD when prescribed as part of a treatment protocol. These findings must be replicated in multicenter, randomized studies to corroborate our results.
A modified implantation technique of the HeartWare ventricular assist device for pediatric patients Iki Adachi, MD,a Francisco A. Guzmán-Pruneda, MD,a Aamir Jeewa, MD,b Charles D. Fraser Jr, MD,a and E. Dean McKenzie, MDa From the aCongenital Heart Surgery; and the b Pediatric Cardiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, Texas
The last decade has witnessed significant maturation of durable ventricular assist device treatment. Among multiple contributing factors, the greatest effect would have certainly been derived from the emergence of implantable devices. Survival with an implantable, continuous-flow device has clearly been superior to that with an extracorporeal, pulsatile pump.1 In small children, however, a pulsatile device still remains the only viable option. This frustrating reality has compelled pediatric centers to explore the use of adult-sized implantable devices in adolescents. Although the HeartMate II (Thoratec Corporation Inc, Pleasanton, CA) represents an excellent option, its application is limited to larger children with a body surface area of approximately 1.3 m2 or greater.2 The HeartWare ventricular assist device (HVAD; HeartWare, Framingham, MA) has the potential to overcome this paradigm owing to its compact design. There exists, however, a concern for inflow cannula configuration with this particular device.3 If placed intrapericardially, as recommended by the manufacturer, the rotor housing may conform to the chest wall laterally, and the inflow cannula typically lies on a horizontal plane.
Disclosure statement None of the authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose.
References 1. Aggarwal A, Pant R, Kumar S, et al. Incidence and management of gastrointestinal bleeding with continuous flow assist devices. Ann Thorac Surg 2012;93:1534-40. 2. Demirozu ZT, Radovancevic R, Hochman LF, et al. Arteriovenous malformation and gastrointestinal bleeding in patients with the HeartMate II left ventricular assist device. J Heart Lung Transplant 2011;30:849-53. 3. Ge ZZ, Chen HM, Gao YJ, et al. Efficacy of thalidomide for refractory gastrointestinal bleeding from vascular malformation. Gastroenterology 2011:141:1629–37:(e1–4). 4. Kamalaporn P, Saravanan R, Cirocco M, et al. Thalidomide for the treatment of chronic gastrointestinal bleeding from angiodysplasias: a case series. Eur J Gastroenterol Hepatol 2009;21:1347-50. 5. Ray R, Kale PP, Ha R, Banerjee D. Treatment of left ventricular assist device associated arteriovenous malformations with thalidomide. ASAIO J 2014;60:482-3.
In addition, because the pump occupies a space in the left chest cavity, atelectasis of the left lower lobe can occur. Ideally, the inflow cannula should be parallel to the interventricular septum,3 and the pump housing should not interfere with proper lung expansion. We describe a surgical technique that ensures optimal positioning of the HVAD pump for pediatric patients. A median sternotomy is created. Preceding the administration of heparin, a pre-peritoneal pocket is fashioned by dividing the left diaphragm anteriorly. The pocket for the HVAD is considerably smaller than that necessary for the HeartMate II, making pocket-related complications less likely. Cardiopulmonary bypass is established. A left atrial vent is placed via the Waterston groove. The LV is incised and the myocardium is resected to achieve an adequate opening for the inflow cannula. The optimal site should lie slightly anterior to the left ventricular (LV) apex and at least 5 mm off from the left anterior descending coronary artery to avoid compromising the coronary circulation by the sewing ring. Meticulous attention is given, particularly in LV noncompaction, to remove any excess muscle that could potentially obstruct the inflow cannula once the device is implanted (Figure 1). A mural thrombus is not uncommon in hearts with LV non-compaction and should be promptly removed if present. The use of a left atrial vent will aid in maintaining a bloodless surgical field. Once satisfied with the LV apical core, 12 pairs of 2-0 TiCron (Covidien, New Haven, CT) mattress stitches are placed around the apical opening through a suitably trimmed circular-shaped felt strip. The sutures are passed through the sewing ring and tied down. While the sutures are being tied, particular care is given to make certain that the center of the sewing ring is properly aligned with respect to the LV apical opening. To prevent malalignment of the sewing ring, the
Research Correspondence
135
Figure 1 (A) Coring of the left ventricular apex in a heart with non-compaction morphology. Apical trabeculations are removed, with a particular care not to damage the papillary muscles of the mitral valve. Meticulous attention is required to identify a potential mural thrombus, which needs to be removed if present. (Inset shows final appearance after completion of coring). (B) Tying the sutures on the sewing ring with (left) or without (right) snuggers. It is important to make certain that the center of the sewing ring is properly aligned with respect to the left ventricular apical opening. To facilitate such arrangement of the ring, a snugger is fixed on the suture at each quadrant.
sutures at each quadrant are fixed in place with a snugger before the rest of the sutures are tied down (Figure 1). Once the HVAD pump is inserted into and secured to the ring, the apex is reoriented caudally and medially by securing the HVAD pump in the infradiaphragmatic pump pocket prepared earlier. Careful manipulation will avoid distorting the right ventricular geometry during this maneuver. Several large Ethibond (Ethicon, Somerville, NJ) sutures, which are tied circumferentially around the neck of the pump and subsequently anchored to the rectus fascia, can be used to secure the proper position and orientation of the pump. With this maneuver, the axis of the inflow cannula becomes nearly parallel to the interventricular septum. Implantation is completed by an
end-to-side anastomosis of the outflow graft to the ascending aorta. Because children, particularly those with cyanotic heart disease, have more cardiac return through systemic-topulmonary shunts, it is crucial to ensure the left atrial vent properly decompresses the left heart while the outflow graft is being clamped. After deairing of the heart, HVAD support is initiated as cardiopulmonary bypass is weaned. This technique is feasible even in small children. The smallest patient we implanted with this technique was a 4-year-old boy with a weight of 13 kg and a body surface area of 0.6 m2. An optimal inflow configuration is pivotal to success for long-term ventricular assist device support, especially with
136
The Journal of Heart and Lung Transplantation, Vol 34, No 1, January 2015
Figure 2 Postoperative chest X-rays with (A) the standard intrapericardial placement and with (B) the infradiaphragmatic placement. A dotted line represents an imaginary line of the interventricular septum. With the intrapericardial technique, the inflow axis lies in a horizontal plane, resulting in a rather perpendicular orientation to the septum. By contrast, the inflow sits in a vertical plane and parallel to the septum with the infradiaphragmatic technique. Because the pump occupies the space in the left chest cavity with the intrapericardial technique, the lower lobe of the left lung remains atelectatic, as evidenced by an unclear boarder of the hemidiaphragm. With the infradiaphragmatic technique, the left lung is fully expanded.
small hearts. It has been described that even adult patients’ hearts with a smaller LV cavity have a more limited tolerance for minor imperfections regarding inflow cannula positioning.4 In other words, the standard implantation technique that has proven effective for adult patients may not be the best option for children that essentially have device-patient size mismatch. Among several important surgical considerations for device placement, one of the most critical is the axis of the inflow cannula relative to the interventricular septum.3,5 The infradiaphragmatic technique we describe here will result in a more favorable angle of the inflow cannula than the standard intrapericardial placement (Figure 2). Although the inflow cannula with the infradiaphragmatic placement sits in a vertical plane (i.e., parallel to the interventricular septum), the intrapericardial placement typically results in a horizontally oriented inflow angle (i.e., perpendicular to the interventricular septum). Furthermore, due to the location of the pump housing, proper expansion of the left lung tends to be impaired with the intrapericardial placement, resulting in atelectasis. The large experience with the HeartMate II has shown that a horizontal orientation of the inflow cannula predisposes to pump thrombogenesis.5 Although one can argue that a lesson learned from the HeartMate II may not directly be applicable to the HVAD, we believe that both devices share a fundamental principle: the inflow cannula should be parallel, rather than perpendicular, to the interventricular
septum. Certainly, the angle of the inflow cannula with an implantable centrifugal VAD and its relation to clinical outcomes, such as pump thrombosis, demands more attention. We hope this report will incite further discussion and research in this important subject matter.
Disclosure statement None of the authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose.
References 1. Kirklin JK, Naftel DC, Kormos RL, et al. Fifth INTERMACS annual report: risk factor analysis from more than 6,000 mechanical circulatory support patients. J Heart Lung Transplant 2013;32:141-56. 2. Cabrera AG, Sundareswaran KS, Samayoa AX, et al. Outcomes of pediatric patients supported by the HeartMate II left ventricular assist device in the United States. J Heart Lung Transplant 2013;32: 1107-13. 3. Gregoric ID, Cohn WE, Frazier OH. Diaphragmatic implantation of the HeartWare ventricular assist device. J Heart Lung Transplant 2011;30: 467-70. 4. Kirklin JK, Naftel DC, Kormos RL, et al. Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) analysis of pump thrombosis in the HeartMate II left ventricular assist device. J Heart Lung Transplant 2014;33:12-22. 5. Taghavi S, Ward C, Jayarajan SN, Gaughan J, Wilson LM, Mangi AA. Surgical technique influences HeartMate II left ventricular assist device thrombosis. Ann Thorac Surg 2013;96:1259-65.
The Journal of Heart and Lung Transplantation, Vol 34, No 1, January 2015
Limitations to our study include the lack of a control group or a different treatment arm. Owing to recurrent, lifethreatening, and refractory bleeding in these patients, we concluded that withholding a therapy that we had previously shown would benefit these patients would be unethical. We also did not assess the relative effect of thalidomide in reduction of LVAD-associated GIAD compared with other therapeutic agents. Other investigators have used agents, including octreotide, to reduce bleeding due to GIAD in LVAD patients, although octreotide is difficult to tolerate due to its mode of delivery (injection) and adverse effects, including nausea and bradycardia. Lenalidomide, a synthetic analog of thalidomide, has been shown to be as potent as the parent drug, with less of the non-hematologic adverse effects, and is another potential treatment option for these patients. In summary, thalidomide can be used safely in patients with LVAD-associated GIAD when prescribed as part of a treatment protocol. These findings must be replicated in multicenter, randomized studies to corroborate our results.
A modified implantation technique of the HeartWare ventricular assist device for pediatric patients Iki Adachi, MD,a Francisco A. Guzmán-Pruneda, MD,a Aamir Jeewa, MD,b Charles D. Fraser Jr, MD,a and E. Dean McKenzie, MDa From the aCongenital Heart Surgery; and the b Pediatric Cardiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, Texas
The last decade has witnessed significant maturation of durable ventricular assist device treatment. Among multiple contributing factors, the greatest effect would have certainly been derived from the emergence of implantable devices. Survival with an implantable, continuous-flow device has clearly been superior to that with an extracorporeal, pulsatile pump.1 In small children, however, a pulsatile device still remains the only viable option. This frustrating reality has compelled pediatric centers to explore the use of adult-sized implantable devices in adolescents. Although the HeartMate II (Thoratec Corporation Inc, Pleasanton, CA) represents an excellent option, its application is limited to larger children with a body surface area of approximately 1.3 m2 or greater.2 The HeartWare ventricular assist device (HVAD; HeartWare, Framingham, MA) has the potential to overcome this paradigm owing to its compact design. There exists, however, a concern for inflow cannula configuration with this particular device.3 If placed intrapericardially, as recommended by the manufacturer, the rotor housing may conform to the chest wall laterally, and the inflow cannula typically lies on a horizontal plane.
Disclosure statement None of the authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose.
References 1. Aggarwal A, Pant R, Kumar S, et al. Incidence and management of gastrointestinal bleeding with continuous flow assist devices. Ann Thorac Surg 2012;93:1534-40. 2. Demirozu ZT, Radovancevic R, Hochman LF, et al. Arteriovenous malformation and gastrointestinal bleeding in patients with the HeartMate II left ventricular assist device. J Heart Lung Transplant 2011;30:849-53. 3. Ge ZZ, Chen HM, Gao YJ, et al. Efficacy of thalidomide for refractory gastrointestinal bleeding from vascular malformation. Gastroenterology 2011:141:1629–37:(e1–4). 4. Kamalaporn P, Saravanan R, Cirocco M, et al. Thalidomide for the treatment of chronic gastrointestinal bleeding from angiodysplasias: a case series. Eur J Gastroenterol Hepatol 2009;21:1347-50. 5. Ray R, Kale PP, Ha R, Banerjee D. Treatment of left ventricular assist device associated arteriovenous malformations with thalidomide. ASAIO J 2014;60:482-3.
In addition, because the pump occupies a space in the left chest cavity, atelectasis of the left lower lobe can occur. Ideally, the inflow cannula should be parallel to the interventricular septum,3 and the pump housing should not interfere with proper lung expansion. We describe a surgical technique that ensures optimal positioning of the HVAD pump for pediatric patients. A median sternotomy is created. Preceding the administration of heparin, a pre-peritoneal pocket is fashioned by dividing the left diaphragm anteriorly. The pocket for the HVAD is considerably smaller than that necessary for the HeartMate II, making pocket-related complications less likely. Cardiopulmonary bypass is established. A left atrial vent is placed via the Waterston groove. The LV is incised and the myocardium is resected to achieve an adequate opening for the inflow cannula. The optimal site should lie slightly anterior to the left ventricular (LV) apex and at least 5 mm off from the left anterior descending coronary artery to avoid compromising the coronary circulation by the sewing ring. Meticulous attention is given, particularly in LV noncompaction, to remove any excess muscle that could potentially obstruct the inflow cannula once the device is implanted (Figure 1). A mural thrombus is not uncommon in hearts with LV non-compaction and should be promptly removed if present. The use of a left atrial vent will aid in maintaining a bloodless surgical field. Once satisfied with the LV apical core, 12 pairs of 2-0 TiCron (Covidien, New Haven, CT) mattress stitches are placed around the apical opening through a suitably trimmed circular-shaped felt strip. The sutures are passed through the sewing ring and tied down. While the sutures are being tied, particular care is given to make certain that the center of the sewing ring is properly aligned with respect to the LV apical opening. To prevent malalignment of the sewing ring, the
Research Correspondence
135
Figure 1 (A) Coring of the left ventricular apex in a heart with non-compaction morphology. Apical trabeculations are removed, with a particular care not to damage the papillary muscles of the mitral valve. Meticulous attention is required to identify a potential mural thrombus, which needs to be removed if present. (Inset shows final appearance after completion of coring). (B) Tying the sutures on the sewing ring with (left) or without (right) snuggers. It is important to make certain that the center of the sewing ring is properly aligned with respect to the left ventricular apical opening. To facilitate such arrangement of the ring, a snugger is fixed on the suture at each quadrant.
sutures at each quadrant are fixed in place with a snugger before the rest of the sutures are tied down (Figure 1). Once the HVAD pump is inserted into and secured to the ring, the apex is reoriented caudally and medially by securing the HVAD pump in the infradiaphragmatic pump pocket prepared earlier. Careful manipulation will avoid distorting the right ventricular geometry during this maneuver. Several large Ethibond (Ethicon, Somerville, NJ) sutures, which are tied circumferentially around the neck of the pump and subsequently anchored to the rectus fascia, can be used to secure the proper position and orientation of the pump. With this maneuver, the axis of the inflow cannula becomes nearly parallel to the interventricular septum. Implantation is completed by an
end-to-side anastomosis of the outflow graft to the ascending aorta. Because children, particularly those with cyanotic heart disease, have more cardiac return through systemic-topulmonary shunts, it is crucial to ensure the left atrial vent properly decompresses the left heart while the outflow graft is being clamped. After deairing of the heart, HVAD support is initiated as cardiopulmonary bypass is weaned. This technique is feasible even in small children. The smallest patient we implanted with this technique was a 4-year-old boy with a weight of 13 kg and a body surface area of 0.6 m2. An optimal inflow configuration is pivotal to success for long-term ventricular assist device support, especially with
136
The Journal of Heart and Lung Transplantation, Vol 34, No 1, January 2015
Figure 2 Postoperative chest X-rays with (A) the standard intrapericardial placement and with (B) the infradiaphragmatic placement. A dotted line represents an imaginary line of the interventricular septum. With the intrapericardial technique, the inflow axis lies in a horizontal plane, resulting in a rather perpendicular orientation to the septum. By contrast, the inflow sits in a vertical plane and parallel to the septum with the infradiaphragmatic technique. Because the pump occupies the space in the left chest cavity with the intrapericardial technique, the lower lobe of the left lung remains atelectatic, as evidenced by an unclear boarder of the hemidiaphragm. With the infradiaphragmatic technique, the left lung is fully expanded.
small hearts. It has been described that even adult patients’ hearts with a smaller LV cavity have a more limited tolerance for minor imperfections regarding inflow cannula positioning.4 In other words, the standard implantation technique that has proven effective for adult patients may not be the best option for children that essentially have device-patient size mismatch. Among several important surgical considerations for device placement, one of the most critical is the axis of the inflow cannula relative to the interventricular septum.3,5 The infradiaphragmatic technique we describe here will result in a more favorable angle of the inflow cannula than the standard intrapericardial placement (Figure 2). Although the inflow cannula with the infradiaphragmatic placement sits in a vertical plane (i.e., parallel to the interventricular septum), the intrapericardial placement typically results in a horizontally oriented inflow angle (i.e., perpendicular to the interventricular septum). Furthermore, due to the location of the pump housing, proper expansion of the left lung tends to be impaired with the intrapericardial placement, resulting in atelectasis. The large experience with the HeartMate II has shown that a horizontal orientation of the inflow cannula predisposes to pump thrombogenesis.5 Although one can argue that a lesson learned from the HeartMate II may not directly be applicable to the HVAD, we believe that both devices share a fundamental principle: the inflow cannula should be parallel, rather than perpendicular, to the interventricular
septum. Certainly, the angle of the inflow cannula with an implantable centrifugal VAD and its relation to clinical outcomes, such as pump thrombosis, demands more attention. We hope this report will incite further discussion and research in this important subject matter.
Disclosure statement None of the authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose.
References 1. Kirklin JK, Naftel DC, Kormos RL, et al. Fifth INTERMACS annual report: risk factor analysis from more than 6,000 mechanical circulatory support patients. J Heart Lung Transplant 2013;32:141-56. 2. Cabrera AG, Sundareswaran KS, Samayoa AX, et al. Outcomes of pediatric patients supported by the HeartMate II left ventricular assist device in the United States. J Heart Lung Transplant 2013;32: 1107-13. 3. Gregoric ID, Cohn WE, Frazier OH. Diaphragmatic implantation of the HeartWare ventricular assist device. J Heart Lung Transplant 2011;30: 467-70. 4. Kirklin JK, Naftel DC, Kormos RL, et al. Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) analysis of pump thrombosis in the HeartMate II left ventricular assist device. J Heart Lung Transplant 2014;33:12-22. 5. Taghavi S, Ward C, Jayarajan SN, Gaughan J, Wilson LM, Mangi AA. Surgical technique influences HeartMate II left ventricular assist device thrombosis. Ann Thorac Surg 2013;96:1259-65.