- Email: [email protected]
A minimally invasive off-pump implantation technique for continuous-flow left ventricular assist devices: Early experience
Author's Accepted Manuscript
A minimally invasive “off pump” implantation technique for continuous flow left ventricular assist devices: early experience Martin Strueber MD, Anna L. Meyer MD, Markus Feussner MD, Joerg Ender MD, Joao-Carlos Correia MD, Friedrich-Wilhelm Mohr MD
http://www.jhltonline.org
PII: DOI: Reference:
S1053-2498(14)01153-X http://dx.doi.org/10.1016/j.healun.2014.05.016 HEALUN5786
To appear in:
J Heart Lung Transplant
Cite this article as: Martin Strueber MD, Anna L. Meyer MD, Markus Feussner MD, Joerg Ender MD, Joao-Carlos Correia MD, Friedrich-Wilhelm Mohr MD, A minimally invasive “off pump” implantation technique for continuous flow left ventricular assist devices: early experience, J Heart Lung Transplant, http://dx.doi.org/10.1016/j. healun.2014.05.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
A MINIMALLY INVASIVE “OFF PUMP” IMPLANTATION TECHNIQUE FOR CONTINUOUS FLOW LEFT VENTRICULAR ASSIST DEVICES: EARLY EXPERIENCE
Martin Strueber MD*, Anna L Meyer MD*, Markus Feussner MD**, Joerg Ender MD**, JoaoCarlos Correia MD*, Friedrich-Wilhelm Mohr MD*
*Heart Center Leipzig University, Clinic for Heart Surgery, Leipzig, Germany **Heart Center Leipzig University, Department of Anesthesiology, Leipzig, Germany
Corresponding author: Martin Strueber, MD Professor of Thoracic Transplantation Heart Center Leipzig University Clinic for Heart Surgery Struempellstr. 39, 04289 Leipzig, Germany phone: +49 341 865 1570; fax: +49 341 865 1586 Email: [email protected]
Short title: Off-pump Thoracotomy Approach for HVAD-Implantation
1
Abstract Background: The HeartWare® left ventricular assist device (HVAD) is approved for implantation via sternotomy with cardiopulmonary bypass. We report on our initial experience with this device implanted off-pump via thoracotomy. Methods: A total of 26 patients were included in this review. All patients were INTERMACS 2 or 3, and underwent implantation of an HVAD as an elective procedure via thoracotomy and mini sternotomy approach. Assessment of the ventricle was performed using 3D echocardiography, and was also used to facilitate proper pump positioning. Patients were managed during followup using anticoagulants at a target INR of 2.0-2.5 as well as antiplatelet agents. Results: Implantation was performed without the use of cardiopulmonary bypass, but one patient did require conversion to on-pump surgery. There were no perioperative deaths. There were no right heart failure events, and mean ICU stay was 1.5 days. Transfusions of 1 to 3 units were required in 16 patients, while 10 patients maintained a stable perioperative hematocrit of at least 30% and did not require transfusion, Survival through 90 days was 100%, and survival through 180 days was 87%. Conclusions: Our experience was favorable in respect to outcome, safety and use of blood products. It can be used as an alternative approach for left ventricular assist device (LVAD) implantation using the HVAD.
Key words: HeartWare®, HVAD, left ventricular assist device, thoracotomy
2
Introduction The gold standard for treatment of advanced heart failure is heart transplantation. However, this treatment is severely limited by the number of available donor organs. The use of mechanical circulatory support using a left ventricular device is becoming an indispensable alternative in these patients. HVAD Systems (HeartWare®, Inc., Framingham, MA, USA) have been implanted via sternotomy since 2007. However, the need for cardiac surgeries in this population, often requiring repeated sternotomies, lends to significant morbidity for the patients. Avoiding cardiopulmonary bypass (CPB) is also attractive since bypass itself can contribute to renal dysfunction and hemolysis. Device replacement has been done safely and effectively via anterolateral thoracotomy [1], but the first thoracotomy implants to the descending aorta began in 2009 [2]. On pump thoracotomy approaches have been performed in Hannover since 2011 [3], and Leipzig since 2012 [4]. Device replacement has been successfully performed off-pump [5], as well as off-pump implantation of LVADs [6]. However, the experience of off-pump LVAD implants using thoracotomy and ministernotomy has been limited to individual case reports [7]. We report here the data from 26 consecutive cases of HVAD implants using an off-pump thoracotomy approach performed since June, 2012 at our center.
Methods Patients Following informed consent of the patients, data of 26 patients who underwent implantation of an HVAD System as an LVAD since June 2012 were analyzed in a prospective manner.
3
Inclusion criteria Patients fulfilling INTERMACS categories 2 and 3 after evaluation and hemodynamic stabilization were included in the analysis. The surgery was scheduled as an elective procedure, so as informed consent for the procedure could be obtained.
Exclusion criteria Patients with hemodynamic instability (INTERMACS 1) were excluded from the analysis as well as patients being supported by extracorporeal membrane oxygenators (ECMO) prior to the VAD procedure. Aortic valve regurgitation > grade 1 was also an exclusion criterion as well as any indication for concomitant cardiac surgery. Patients with thrombus formations in the auricle of the left atrium or within the left ventricle were also excluded.
HVAD System The HeartWare® System and its implantation have been previously described [8, 9]. We do make a slight modification to the preparation of the pump in all implants in that we shorten the bend relief by removing all but two of the rings to ease flexibility for implantation at the apex and tunneling to the aorta (Figure 1).
Surgical Procedure A thorough assessment of the left ventricle is done by 3D Echocardiography. The right ventricle, including the auricle of the left atrial appendage is assessed for thrombus, and the intra-atrial septum is assessed for presence of patent foramen ovale (PFO). See Figure 2.
4
The upper hemisternotomy is performed similarly to the procedure for a minimally invasive aortic valve replacement, using a J shape incision. The anterolateral mini thoracotomy is performed similarly to a transapical valve implantation approach, via the fifth or sixth intercostal space. A 3D Echo is performed following attachment of the sewing ring to assess proper placement at the apex. Prior to fixation of the epicardial sewing ring, a needle is inserted from the apex into the left ventricle and 3D Echo is used to visualize the position of the needle in the ventricle. The sewing ring is attached with only four felt sutures (one in each quadrant), since in the off-pump procedure over manipulation or contact with the heart can be complicated by arrhythmias. A prolene running suture and bio-glue aid in final attachment of the sewing ring (see Figure 3A). Heparin is given to achieve an activated clotting time of 200 - 250 seconds. Before coring any implanted pacemaker is switched off. A two-step procedure is used for coring and pump implantation: an initial dose of adenosine is injected (mean 30 mg). Following onset of short asystoly or depressed blood pressure the apex is incised within the sewing ring using a number 11 blade and the coring knife is inserted into the ventricle (Figure 3B). Releasing the coring instrument without actual coring leads to a blood tight sealing of the device within the sewing ring. After a few seconds the circulation and cardiac function recovers. A second injection of adenosine is prepared and given after stable hemodynamics is achieved. During the second depression of cardiac function the actual coring is preformed, and the inflow of the pump is inserted into the ventricle. Fixation of the pump is performed using the screwdriver for tightening the sewing ring. For this off-pump thoracotomy implant procedure, we utilized the smaller, original coring tool is used to avoid excessive bleeding. Using the smaller coring device results in minimal blood loss, allowing time for safe and uncomplicated fixation of the VAD within the epicardial ring (Figure 3C). De-airing is performed immediately after pump insertion by removing about 100 cc of blood via suction out of the outflow graft. The outflow graft is then clamped.
5
The driveline is led out of the thoracotomy incision and tunneled subcutaneously to the right upper quadrant. Care is taken to keep the felt covered part of the driveline inside the body. The outflow graft is then tunneled trough the pericardium to the ascending aorta (Figure 3C). The aorta is partially clamped, and an end-to-side anastomosis is performed (Figure 3D). After starting the VAD at 1800 rpm a needle is used to remove remaining air from the outflow graft, before the clamp on the aorta is removed. Then the pump speed is increased according to echocardiography findings to adequately support the left ventricle, but allowing aortic valve opening. Typical pump speeds range from 2500 to 2700 rpm. In the case of a redo procedure the outflow graft is tunneled extrapericardially across the anterior wall of the LV and the right heart outflow. Care is taken not to compromise any open vascular grafts. Partial clamping of the ascending aorta may include vascular grafts. At the end of the procedure, a layer of Gore Tex is placed between the pump and the thoracic wall to avoid the possibility of erosions. Before closing of the incisions full reversal of heparin by protamine infusion is carried out.
Anticoagulation Protocol No anticoagulation is given during the first 24 hours after surgery. Then heparin infusion is started to achieve an activated clotting time of 160 - 200 seconds. Coumadin is started as well as platelet inhibitors thereafter. The maintenance protocol is a target INR of 2.0 - 2.5. The INR is measured twice weekly. For antiplatelet therapy, clopidogrel 75 mg is given three times per week. P2Y12-specific platelet inhibition is monitored by conventional aggregometry as well as the VASP assay [10].
6
Statistical Analysis Summary and descriptive statistics were used to describe patient demographics, perioperative data, adverse events, and early outcomes.
Results A total of 26 consecutive commercial implants were performed by an off-pump thoracotomy approach from June 2012 to April 2013. The overall number of isolated LVAD procedures at that time was 43. Baseline patient data for these 26 cases is presented in Table 1. Seven patients had prior cardiac surgery. Four of these had prior revascularizations with mostly patent grafts. The remaining three had mitral valve surgery. All patients fit INTERMACS criteria 2 or 3. Tables 2 and 3 show the operative characteristics and outcomes of these patients. The mean operative time was 132 minutes (range 102-171 minutes). There were no perioperative deaths, and one patient required conversion to on-pump surgery. This patient was status post anterior myocardial infarction. Imminent rupture of the ventricle was suspected at placement of the sewing ring, therefore CPB was used and the heart was fibrillated. Additional pledgeted sutures were used to ensure safe placement of the epicardial ring. There were no right heart failure events, and the ICU stay ranged from 1 to 4 days (mean 1.5 days). One patient required re-exploration for alignment of the ventricular assist device (VAD) inflow. She had hypertrophic heart disease with additional diastolic heart failure and a small left ventricular cavity. Intraoperative alignment of the VAD was achieved, but after extubation of the patient, movements of the diaphragm led to suction events. Therefore rethoracotomy was required and fixation of the VAD on the thoracic wall was carried out.
7
Blood transfusions of 0-3 Units of PRBCs (mean 1.2 Units) were required in this patient population. Ten patients (38.5%) did not require transfusions, having maintained a hematocrit of at least 30% during the perioperative period. Follow up through 180 days was examined for these 26 patients. There was no perioperative or 90 day mortality observed. All but three patients completed the 180 follow-up, and overall 180 day survival was 87%. One patient expired after 120 days on VAD support following complications of bacterial septic shock. Late Right Heart failure was the cause of death in another patient after 167 days, and a third patient was lost due to intracranial bleeding after 176 days on the VAD. No additional cerebrovascular accident was observed in the group, therefore the incidence of CVA in this cohort was 4%. A pump thrombosis was found in one patient after day 82 and the device was exchanged. In addition, suspected pump thrombosis with increased power consumption and elevated LDH values led to thrombolytic therapy in one additional patient at day 136. All parameters returned to normal in this patient. Despite the fact that almost all patients fulfilled transplant criteria and were put on the transplant waiting list, no heart transplant procedure was performed in this cohort during 180 days due to scarcity of donor organs and the allocation principle in Germany, which gives no priority to stable LVAD patients.
Discussion This analysis demonstrates the safety and feasibility of implantation of the HeartWare® System as an LVAD by the off-pump thoracotomy approach. Despite the limited viewing field, there are no problems with proper placement of the inflow at the apex. Still, care must be taken
8
to ensure an appropriate size of the thoracotomy to allow rapid insertion of the HVAD into the ventricle. The use of advanced imaging modalities such as 3D Echo to visualize possible thrombus as well as pump placement is the key to what makes this approach safe and effective. Further miniaturization of devices may lead to further downsizing of the incisions. A similar less invasive approach was already suggested by Igor Gregoric and colleagues at the Texas Heart institute in 2008 [11]. Already at this time it could be shown that blood transfusions were less utilizating an off pump approach, as well as that avoidance of full sternotomy was feasible. In our series a remarkable further reduction of transfusions could be achieved compared to this early result. We observed that only 16 of 26 patients (61.5%) required a transfusion of PRBCs, ranging from only 1 to 3 Units. HVAD implant via sternotomy approach in clinical trials has reported transfusions >4 U PRBCs required by 8% of patients [12]. There are additional advantages to this approach. First, the pericardium remains intact, but for a small incision at the apex. We hypothesize that thereby an intact pericardium may serve to support the right ventricle and prevent distention. This hypothesis needs to be verified in further studies. Another potential benefit is, that the heart is not lifted out of the pericardium and the right ventricle is never torqued or disturbed during the implant procedure. The use of the off-pump thoracotomy approach allows the potential for a shorter surgical procedure time, and possibly a shorter ICU stay due to less sternal trauma and minimal surgical incisions. Indeed, we noted a mean ICU stay of 1.5 days, whereas in the clinical trial using the on-pump sternotomy approach the mean ICU stay was 13.1 days [13]. Complications associated with cardiopulmonary bypass and extracorporeal circulation, such as hemolysis and renal dysfunction, are also avoided.
9
Second, the pericardial placement of the pump via thoracotomy and hemisternotomy may reduce the incidence of post-operative bleeding and infection. We noticed a low rate of post-operative bleeding in patients when we used this approach. Looking at the 180 day followup, we see a safe perioperative outcome. The rate of CVAs seems low compared to other studies, and the rate of (suspected) pump thrombosis within acceptable rate and manageable. It must be noted here that our protocol, utilizing low antiplatelet inhibition, may benefit bleeding and contribute to the low incidence of cerebral bleedings, but perhaps at the cost of a higher pump thrombosis rate. However, the rate of pump thrombus events leading to exchange (4%) or all suspected or definite pump thrombus events, including those managed medically (8%) that we observed was similar to that reported recently by Najjar et al. in patients with an HVAD implanted using the standard sternotomy approach [14]. Lastly, all efforts to minimize perioperative right heart failure may lead to some patients developing late RV dysfunction as, we saw in one patient in our cohort. This potential late problem needs special attention in the outpatient management period. This study has several limitations. It represents the experience at a single center, therefore extrapolation of results across centers should be made with caution. There are also a small number of cases, which may limit the ability to determine infrequent, yet clinically relevant, adverse events. There also may be site-specific variations in patient management or clinical practice.
Conclusions This analysis demonstrates the safety and feasibility of off-pump, anterolateral thoracotomy implantation of the HVAD system in selected patients with advanced heart failure. We have also demonstrated the value of 3D Echocardiography in this setting. This technique
10
has become our center’s preferred approach when implanting an HVAD in the absence intracardial thrombus or the need for a concomitant cardiac procedure. Using our inclusion criteria, this approach can be used for the majority of our patients.
Disclosure Martin Strueber, MD was a primary investigator in the HeartWare HVAD trial and is expert consultant for HeartWareTM (HeartWare, Inc.; Miramar, Florida). The other authors have no financial interest in any products presented in this work.
Acknowledgements The authors would like to thank Mary V. Jacoski of HeartWare®, Inc, for editorial support in preparation of this manuscript.
11
References 1. Sajjad M, Butt T, Oezalp F, et al. An alternative approach to explantation and exchange of the HeartWare left ventricular assist device. Eur J Cardiothorac Surg 2013;43:1247-50. 2. Stepanenko A, Potapov E, Dubaev A, et al. Impact of surgical approach on neurological adverse events: Single-center experience with HeartWare HVAD implanted via left lateral thoracotomy. Thorac Cardiovasc Surg 2011;59:V56. 3. Schmitto JD, Molitoris U, Haverich A, Strueber M. Implantation of a centrifugal pump as a left ventricular assist device through a novel, minimized approach: Upper hemisternotomy combined with anterolateral thoracotomy. J Thorac Cardiovasc Surg 2012;143:511-3. 4. Meyer AL, Hahn J, von Samson-Himmelstjerna P, et al. Minimal-Invasive LVAD Implantation, Is It Safe or Even Better? J Heart Lung Transplant 2013;32:S58. 5. Nakashima K, Kirsch MEW, Vermes E, Rosanval O, Loisance D. Off-pump Replacement of the INCOR Implantable Axial-flow Pump. J Heart Lung Transplant 2009;28:199-201. 6. Awad H, Abd El Dayem M, Heard J, Dimitrova G, Yu L, Sun B. Initial experience with offpump left ventricular assist device implantation in single center: retrospective analysis. J J Cardiothorac Surg 2010;5:123. 7. Cheung A, Lamarche Y, Kaan A, et al. Off-Pump Implantation of the HeartWare HVAD Left Ventricular Assist Device Through Minimally Invasive Incisions. Ann Thorac Surg 2011;91:1294-6. 8. LaRose JA, Tamez D, Ashenuga M, Reyes C. Design Concepts and Principle of Operation of the HeartWare Ventricular Assist System. ASAIO J 2010;56:285-9. 9. Slaughter MS. Implantation of the HeartWare Left Ventricular Assist Device. Semin Thorac Cardiovasc Surg 2011;23:245-7.
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10. Aradi D, Magyarlaki T, Tokes-Füzesi M, et al. Comparison of conventional aggregometry with VASP for monitoring P2Y12-specific platelet inhibition. Platelets 2010;21:563-70. 11. Gregoric ID, La Francesca S, Myers T, et al. A less invasive approach to axial flow pump insertion. J Heart Lung Transplant 2008;27:423-6. 12. Aaronson K, Slaughter M, Miller L, et al. Use of an intrapericardial, continuous-flow, centrifugal pump in patients awaiting heart transplantation. Circulation. 2012;125:31913200. 13. Strueber M, O'Driscoll G, Jansz P et al. Multicenter Evaluation of an Intrapericardial Left Ventricular Assist System. J Am Coll Cardiol 2011;57:1375-1382. 14. Najjar S, Slaughter M, Pagani F et al. An analysis of pump thrombus events in patients in the HeartWare BTT and CAP trial. Journal of Heart and Lung Transplantation 2014; 33: 2334.
13
Figure Legends Figure 1:
Image of the 10mm outflow graft with adjustable strain relief (A) and connection to the HVAD (B)
Figure 2:
3D Echocardiographic assessment of the right ventricle
Figure 3:
Intra-operative images of (A) sewing ring attachment to the apex, (B) coring of the apex prior to pump implantation (C) implanted HVAD, with outflow graft tunneled to aorta, and (D) anastomosis of the outflow graft.
14
15
16
17
Table 1: Baseline Patient Characteristics (N= 26)
Demographics
N (%)
Male
22 (85)
Female
4 (15)
Mean Age Type of Cardiomyopathy:
57 + 11 years (range: 32-74 years) N (%)
Dilated Cardiomyopathy
14 (54)
Ischemic Cardiomyopathy
11 (42)
Other Prior Cardiac Surgery
1 (4) 7 (27)
18
Table 2: Operative Characteristics (N= 26)
Mean Total Time in OR
Range
132 minutes
102-171 minutes
Blood Transfusions (PRBCs)
1.2 Units
0-3 Units
Total ICU Stay
1.5 days
1-4 days
19
Table 3: Outcomes N=26
Outcome
# of Patients (%)
Perioperative death
0 (0%)
Conversion to on-pump procedure
1 (4%)
Right Heart Failure
0 (0%)
Re-operation (VAD realignment)
1 (4%)
Cerebrovascular Accident
1 (4%)
Pump thrombus requiring exchange
1 (4%)
20
A minimally invasive “off pump” implantation technique for continuous flow left ventricular assist devices: early experience Martin Strueber MD, Anna L. Meyer MD, Markus Feussner MD, Joerg Ender MD, Joao-Carlos Correia MD, Friedrich-Wilhelm Mohr MD
http://www.jhltonline.org
PII: DOI: Reference:
S1053-2498(14)01153-X http://dx.doi.org/10.1016/j.healun.2014.05.016 HEALUN5786
To appear in:
J Heart Lung Transplant
Cite this article as: Martin Strueber MD, Anna L. Meyer MD, Markus Feussner MD, Joerg Ender MD, Joao-Carlos Correia MD, Friedrich-Wilhelm Mohr MD, A minimally invasive “off pump” implantation technique for continuous flow left ventricular assist devices: early experience, J Heart Lung Transplant, http://dx.doi.org/10.1016/j. healun.2014.05.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
A MINIMALLY INVASIVE “OFF PUMP” IMPLANTATION TECHNIQUE FOR CONTINUOUS FLOW LEFT VENTRICULAR ASSIST DEVICES: EARLY EXPERIENCE
Martin Strueber MD*, Anna L Meyer MD*, Markus Feussner MD**, Joerg Ender MD**, JoaoCarlos Correia MD*, Friedrich-Wilhelm Mohr MD*
*Heart Center Leipzig University, Clinic for Heart Surgery, Leipzig, Germany **Heart Center Leipzig University, Department of Anesthesiology, Leipzig, Germany
Corresponding author: Martin Strueber, MD Professor of Thoracic Transplantation Heart Center Leipzig University Clinic for Heart Surgery Struempellstr. 39, 04289 Leipzig, Germany phone: +49 341 865 1570; fax: +49 341 865 1586 Email: [email protected]
Short title: Off-pump Thoracotomy Approach for HVAD-Implantation
1
Abstract Background: The HeartWare® left ventricular assist device (HVAD) is approved for implantation via sternotomy with cardiopulmonary bypass. We report on our initial experience with this device implanted off-pump via thoracotomy. Methods: A total of 26 patients were included in this review. All patients were INTERMACS 2 or 3, and underwent implantation of an HVAD as an elective procedure via thoracotomy and mini sternotomy approach. Assessment of the ventricle was performed using 3D echocardiography, and was also used to facilitate proper pump positioning. Patients were managed during followup using anticoagulants at a target INR of 2.0-2.5 as well as antiplatelet agents. Results: Implantation was performed without the use of cardiopulmonary bypass, but one patient did require conversion to on-pump surgery. There were no perioperative deaths. There were no right heart failure events, and mean ICU stay was 1.5 days. Transfusions of 1 to 3 units were required in 16 patients, while 10 patients maintained a stable perioperative hematocrit of at least 30% and did not require transfusion, Survival through 90 days was 100%, and survival through 180 days was 87%. Conclusions: Our experience was favorable in respect to outcome, safety and use of blood products. It can be used as an alternative approach for left ventricular assist device (LVAD) implantation using the HVAD.
Key words: HeartWare®, HVAD, left ventricular assist device, thoracotomy
2
Introduction The gold standard for treatment of advanced heart failure is heart transplantation. However, this treatment is severely limited by the number of available donor organs. The use of mechanical circulatory support using a left ventricular device is becoming an indispensable alternative in these patients. HVAD Systems (HeartWare®, Inc., Framingham, MA, USA) have been implanted via sternotomy since 2007. However, the need for cardiac surgeries in this population, often requiring repeated sternotomies, lends to significant morbidity for the patients. Avoiding cardiopulmonary bypass (CPB) is also attractive since bypass itself can contribute to renal dysfunction and hemolysis. Device replacement has been done safely and effectively via anterolateral thoracotomy [1], but the first thoracotomy implants to the descending aorta began in 2009 [2]. On pump thoracotomy approaches have been performed in Hannover since 2011 [3], and Leipzig since 2012 [4]. Device replacement has been successfully performed off-pump [5], as well as off-pump implantation of LVADs [6]. However, the experience of off-pump LVAD implants using thoracotomy and ministernotomy has been limited to individual case reports [7]. We report here the data from 26 consecutive cases of HVAD implants using an off-pump thoracotomy approach performed since June, 2012 at our center.
Methods Patients Following informed consent of the patients, data of 26 patients who underwent implantation of an HVAD System as an LVAD since June 2012 were analyzed in a prospective manner.
3
Inclusion criteria Patients fulfilling INTERMACS categories 2 and 3 after evaluation and hemodynamic stabilization were included in the analysis. The surgery was scheduled as an elective procedure, so as informed consent for the procedure could be obtained.
Exclusion criteria Patients with hemodynamic instability (INTERMACS 1) were excluded from the analysis as well as patients being supported by extracorporeal membrane oxygenators (ECMO) prior to the VAD procedure. Aortic valve regurgitation > grade 1 was also an exclusion criterion as well as any indication for concomitant cardiac surgery. Patients with thrombus formations in the auricle of the left atrium or within the left ventricle were also excluded.
HVAD System The HeartWare® System and its implantation have been previously described [8, 9]. We do make a slight modification to the preparation of the pump in all implants in that we shorten the bend relief by removing all but two of the rings to ease flexibility for implantation at the apex and tunneling to the aorta (Figure 1).
Surgical Procedure A thorough assessment of the left ventricle is done by 3D Echocardiography. The right ventricle, including the auricle of the left atrial appendage is assessed for thrombus, and the intra-atrial septum is assessed for presence of patent foramen ovale (PFO). See Figure 2.
4
The upper hemisternotomy is performed similarly to the procedure for a minimally invasive aortic valve replacement, using a J shape incision. The anterolateral mini thoracotomy is performed similarly to a transapical valve implantation approach, via the fifth or sixth intercostal space. A 3D Echo is performed following attachment of the sewing ring to assess proper placement at the apex. Prior to fixation of the epicardial sewing ring, a needle is inserted from the apex into the left ventricle and 3D Echo is used to visualize the position of the needle in the ventricle. The sewing ring is attached with only four felt sutures (one in each quadrant), since in the off-pump procedure over manipulation or contact with the heart can be complicated by arrhythmias. A prolene running suture and bio-glue aid in final attachment of the sewing ring (see Figure 3A). Heparin is given to achieve an activated clotting time of 200 - 250 seconds. Before coring any implanted pacemaker is switched off. A two-step procedure is used for coring and pump implantation: an initial dose of adenosine is injected (mean 30 mg). Following onset of short asystoly or depressed blood pressure the apex is incised within the sewing ring using a number 11 blade and the coring knife is inserted into the ventricle (Figure 3B). Releasing the coring instrument without actual coring leads to a blood tight sealing of the device within the sewing ring. After a few seconds the circulation and cardiac function recovers. A second injection of adenosine is prepared and given after stable hemodynamics is achieved. During the second depression of cardiac function the actual coring is preformed, and the inflow of the pump is inserted into the ventricle. Fixation of the pump is performed using the screwdriver for tightening the sewing ring. For this off-pump thoracotomy implant procedure, we utilized the smaller, original coring tool is used to avoid excessive bleeding. Using the smaller coring device results in minimal blood loss, allowing time for safe and uncomplicated fixation of the VAD within the epicardial ring (Figure 3C). De-airing is performed immediately after pump insertion by removing about 100 cc of blood via suction out of the outflow graft. The outflow graft is then clamped.
5
The driveline is led out of the thoracotomy incision and tunneled subcutaneously to the right upper quadrant. Care is taken to keep the felt covered part of the driveline inside the body. The outflow graft is then tunneled trough the pericardium to the ascending aorta (Figure 3C). The aorta is partially clamped, and an end-to-side anastomosis is performed (Figure 3D). After starting the VAD at 1800 rpm a needle is used to remove remaining air from the outflow graft, before the clamp on the aorta is removed. Then the pump speed is increased according to echocardiography findings to adequately support the left ventricle, but allowing aortic valve opening. Typical pump speeds range from 2500 to 2700 rpm. In the case of a redo procedure the outflow graft is tunneled extrapericardially across the anterior wall of the LV and the right heart outflow. Care is taken not to compromise any open vascular grafts. Partial clamping of the ascending aorta may include vascular grafts. At the end of the procedure, a layer of Gore Tex is placed between the pump and the thoracic wall to avoid the possibility of erosions. Before closing of the incisions full reversal of heparin by protamine infusion is carried out.
Anticoagulation Protocol No anticoagulation is given during the first 24 hours after surgery. Then heparin infusion is started to achieve an activated clotting time of 160 - 200 seconds. Coumadin is started as well as platelet inhibitors thereafter. The maintenance protocol is a target INR of 2.0 - 2.5. The INR is measured twice weekly. For antiplatelet therapy, clopidogrel 75 mg is given three times per week. P2Y12-specific platelet inhibition is monitored by conventional aggregometry as well as the VASP assay [10].
6
Statistical Analysis Summary and descriptive statistics were used to describe patient demographics, perioperative data, adverse events, and early outcomes.
Results A total of 26 consecutive commercial implants were performed by an off-pump thoracotomy approach from June 2012 to April 2013. The overall number of isolated LVAD procedures at that time was 43. Baseline patient data for these 26 cases is presented in Table 1. Seven patients had prior cardiac surgery. Four of these had prior revascularizations with mostly patent grafts. The remaining three had mitral valve surgery. All patients fit INTERMACS criteria 2 or 3. Tables 2 and 3 show the operative characteristics and outcomes of these patients. The mean operative time was 132 minutes (range 102-171 minutes). There were no perioperative deaths, and one patient required conversion to on-pump surgery. This patient was status post anterior myocardial infarction. Imminent rupture of the ventricle was suspected at placement of the sewing ring, therefore CPB was used and the heart was fibrillated. Additional pledgeted sutures were used to ensure safe placement of the epicardial ring. There were no right heart failure events, and the ICU stay ranged from 1 to 4 days (mean 1.5 days). One patient required re-exploration for alignment of the ventricular assist device (VAD) inflow. She had hypertrophic heart disease with additional diastolic heart failure and a small left ventricular cavity. Intraoperative alignment of the VAD was achieved, but after extubation of the patient, movements of the diaphragm led to suction events. Therefore rethoracotomy was required and fixation of the VAD on the thoracic wall was carried out.
7
Blood transfusions of 0-3 Units of PRBCs (mean 1.2 Units) were required in this patient population. Ten patients (38.5%) did not require transfusions, having maintained a hematocrit of at least 30% during the perioperative period. Follow up through 180 days was examined for these 26 patients. There was no perioperative or 90 day mortality observed. All but three patients completed the 180 follow-up, and overall 180 day survival was 87%. One patient expired after 120 days on VAD support following complications of bacterial septic shock. Late Right Heart failure was the cause of death in another patient after 167 days, and a third patient was lost due to intracranial bleeding after 176 days on the VAD. No additional cerebrovascular accident was observed in the group, therefore the incidence of CVA in this cohort was 4%. A pump thrombosis was found in one patient after day 82 and the device was exchanged. In addition, suspected pump thrombosis with increased power consumption and elevated LDH values led to thrombolytic therapy in one additional patient at day 136. All parameters returned to normal in this patient. Despite the fact that almost all patients fulfilled transplant criteria and were put on the transplant waiting list, no heart transplant procedure was performed in this cohort during 180 days due to scarcity of donor organs and the allocation principle in Germany, which gives no priority to stable LVAD patients.
Discussion This analysis demonstrates the safety and feasibility of implantation of the HeartWare® System as an LVAD by the off-pump thoracotomy approach. Despite the limited viewing field, there are no problems with proper placement of the inflow at the apex. Still, care must be taken
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to ensure an appropriate size of the thoracotomy to allow rapid insertion of the HVAD into the ventricle. The use of advanced imaging modalities such as 3D Echo to visualize possible thrombus as well as pump placement is the key to what makes this approach safe and effective. Further miniaturization of devices may lead to further downsizing of the incisions. A similar less invasive approach was already suggested by Igor Gregoric and colleagues at the Texas Heart institute in 2008 [11]. Already at this time it could be shown that blood transfusions were less utilizating an off pump approach, as well as that avoidance of full sternotomy was feasible. In our series a remarkable further reduction of transfusions could be achieved compared to this early result. We observed that only 16 of 26 patients (61.5%) required a transfusion of PRBCs, ranging from only 1 to 3 Units. HVAD implant via sternotomy approach in clinical trials has reported transfusions >4 U PRBCs required by 8% of patients [12]. There are additional advantages to this approach. First, the pericardium remains intact, but for a small incision at the apex. We hypothesize that thereby an intact pericardium may serve to support the right ventricle and prevent distention. This hypothesis needs to be verified in further studies. Another potential benefit is, that the heart is not lifted out of the pericardium and the right ventricle is never torqued or disturbed during the implant procedure. The use of the off-pump thoracotomy approach allows the potential for a shorter surgical procedure time, and possibly a shorter ICU stay due to less sternal trauma and minimal surgical incisions. Indeed, we noted a mean ICU stay of 1.5 days, whereas in the clinical trial using the on-pump sternotomy approach the mean ICU stay was 13.1 days [13]. Complications associated with cardiopulmonary bypass and extracorporeal circulation, such as hemolysis and renal dysfunction, are also avoided.
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Second, the pericardial placement of the pump via thoracotomy and hemisternotomy may reduce the incidence of post-operative bleeding and infection. We noticed a low rate of post-operative bleeding in patients when we used this approach. Looking at the 180 day followup, we see a safe perioperative outcome. The rate of CVAs seems low compared to other studies, and the rate of (suspected) pump thrombosis within acceptable rate and manageable. It must be noted here that our protocol, utilizing low antiplatelet inhibition, may benefit bleeding and contribute to the low incidence of cerebral bleedings, but perhaps at the cost of a higher pump thrombosis rate. However, the rate of pump thrombus events leading to exchange (4%) or all suspected or definite pump thrombus events, including those managed medically (8%) that we observed was similar to that reported recently by Najjar et al. in patients with an HVAD implanted using the standard sternotomy approach [14]. Lastly, all efforts to minimize perioperative right heart failure may lead to some patients developing late RV dysfunction as, we saw in one patient in our cohort. This potential late problem needs special attention in the outpatient management period. This study has several limitations. It represents the experience at a single center, therefore extrapolation of results across centers should be made with caution. There are also a small number of cases, which may limit the ability to determine infrequent, yet clinically relevant, adverse events. There also may be site-specific variations in patient management or clinical practice.
Conclusions This analysis demonstrates the safety and feasibility of off-pump, anterolateral thoracotomy implantation of the HVAD system in selected patients with advanced heart failure. We have also demonstrated the value of 3D Echocardiography in this setting. This technique
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has become our center’s preferred approach when implanting an HVAD in the absence intracardial thrombus or the need for a concomitant cardiac procedure. Using our inclusion criteria, this approach can be used for the majority of our patients.
Disclosure Martin Strueber, MD was a primary investigator in the HeartWare HVAD trial and is expert consultant for HeartWareTM (HeartWare, Inc.; Miramar, Florida). The other authors have no financial interest in any products presented in this work.
Acknowledgements The authors would like to thank Mary V. Jacoski of HeartWare®, Inc, for editorial support in preparation of this manuscript.
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References 1. Sajjad M, Butt T, Oezalp F, et al. An alternative approach to explantation and exchange of the HeartWare left ventricular assist device. Eur J Cardiothorac Surg 2013;43:1247-50. 2. Stepanenko A, Potapov E, Dubaev A, et al. Impact of surgical approach on neurological adverse events: Single-center experience with HeartWare HVAD implanted via left lateral thoracotomy. Thorac Cardiovasc Surg 2011;59:V56. 3. Schmitto JD, Molitoris U, Haverich A, Strueber M. Implantation of a centrifugal pump as a left ventricular assist device through a novel, minimized approach: Upper hemisternotomy combined with anterolateral thoracotomy. J Thorac Cardiovasc Surg 2012;143:511-3. 4. Meyer AL, Hahn J, von Samson-Himmelstjerna P, et al. Minimal-Invasive LVAD Implantation, Is It Safe or Even Better? J Heart Lung Transplant 2013;32:S58. 5. Nakashima K, Kirsch MEW, Vermes E, Rosanval O, Loisance D. Off-pump Replacement of the INCOR Implantable Axial-flow Pump. J Heart Lung Transplant 2009;28:199-201. 6. Awad H, Abd El Dayem M, Heard J, Dimitrova G, Yu L, Sun B. Initial experience with offpump left ventricular assist device implantation in single center: retrospective analysis. J J Cardiothorac Surg 2010;5:123. 7. Cheung A, Lamarche Y, Kaan A, et al. Off-Pump Implantation of the HeartWare HVAD Left Ventricular Assist Device Through Minimally Invasive Incisions. Ann Thorac Surg 2011;91:1294-6. 8. LaRose JA, Tamez D, Ashenuga M, Reyes C. Design Concepts and Principle of Operation of the HeartWare Ventricular Assist System. ASAIO J 2010;56:285-9. 9. Slaughter MS. Implantation of the HeartWare Left Ventricular Assist Device. Semin Thorac Cardiovasc Surg 2011;23:245-7.
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10. Aradi D, Magyarlaki T, Tokes-Füzesi M, et al. Comparison of conventional aggregometry with VASP for monitoring P2Y12-specific platelet inhibition. Platelets 2010;21:563-70. 11. Gregoric ID, La Francesca S, Myers T, et al. A less invasive approach to axial flow pump insertion. J Heart Lung Transplant 2008;27:423-6. 12. Aaronson K, Slaughter M, Miller L, et al. Use of an intrapericardial, continuous-flow, centrifugal pump in patients awaiting heart transplantation. Circulation. 2012;125:31913200. 13. Strueber M, O'Driscoll G, Jansz P et al. Multicenter Evaluation of an Intrapericardial Left Ventricular Assist System. J Am Coll Cardiol 2011;57:1375-1382. 14. Najjar S, Slaughter M, Pagani F et al. An analysis of pump thrombus events in patients in the HeartWare BTT and CAP trial. Journal of Heart and Lung Transplantation 2014; 33: 2334.
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Figure Legends Figure 1:
Image of the 10mm outflow graft with adjustable strain relief (A) and connection to the HVAD (B)
Figure 2:
3D Echocardiographic assessment of the right ventricle
Figure 3:
Intra-operative images of (A) sewing ring attachment to the apex, (B) coring of the apex prior to pump implantation (C) implanted HVAD, with outflow graft tunneled to aorta, and (D) anastomosis of the outflow graft.
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Table 1: Baseline Patient Characteristics (N= 26)
Demographics
N (%)
Male
22 (85)
Female
4 (15)
Mean Age Type of Cardiomyopathy:
57 + 11 years (range: 32-74 years) N (%)
Dilated Cardiomyopathy
14 (54)
Ischemic Cardiomyopathy
11 (42)
Other Prior Cardiac Surgery
1 (4) 7 (27)
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Table 2: Operative Characteristics (N= 26)
Mean Total Time in OR
Range
132 minutes
102-171 minutes
Blood Transfusions (PRBCs)
1.2 Units
0-3 Units
Total ICU Stay
1.5 days
1-4 days
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Table 3: Outcomes N=26
Outcome
# of Patients (%)
Perioperative death
0 (0%)
Conversion to on-pump procedure
1 (4%)
Right Heart Failure
0 (0%)
Re-operation (VAD realignment)
1 (4%)
Cerebrovascular Accident
1 (4%)
Pump thrombus requiring exchange
1 (4%)
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