Tutorial
A novel technique to exclude the left ventricle with an assist device
Left ventricular assist device implantation disrupts the natural intracavitary blood flow path through the heart, introducing flow patterns potentially associated with thrombosis, especially around the inflow cannula. We describe a novel technique for completely excluding the left ventricle with an assist device by using a cone-shaped ring-reinforced prosthesis.
PLEASE BE AWARE:
On 03 June 2021 the US Food and Drug Administration asked surgeons to stop all new implants of the HeartWare Ventricular Assist Device (HVAD) because “observational clinical comparisons … demonstrate a higher frequency of neurological adverse events and mortality associated with the system when compared to other commercially available devices, as well as complaints that the internal pump may delay or fail to restart”.
For more information please see the announcements from the FDA and Medtronic US.
------------------------------------------------------------------------------------------------------------------
Implantation of left ventricular assist devices (LVAD) in patients with end-stage heart failure is a well-accepted and guideline-established therapy . We previously showed flow disturbances around the inflow cannula in the left ventricular (LV) apex in an ex vivo animal model with 4D-Flow MRI . We assumed that the standard implantation technique might carry a risk of thrombus formation in the commonly dilated and poorly contracting LV cavity. Therefore, we propose a novel implantation technique excluding the LV cavity by implanting a cone-shaped prosthetic tube connecting the mitral valve annulus and the LVAD inflow cannula.
This technique should be considered still experimental, with limited clinical feasibility until long-term results are made available.
Cone-shaped prosthesis
The first step is the preparation of a cone-shaped ring-reinforced prosthetic tube. The tube was made out of polytetrafluoroethylene (PTFE), where the distal part was ring-reinforced with an inner diameter of exactly 2 cm, in order to fit perfectly on the inflow cannula of the HeartWare ventricular assist device (HVAD) (HeartWare Inc., Framingham, MA, USA). The proximal part was made cone shaped with PTFE to fit the mitral valve annulus diameter (Figure 1).
1 – Apical preparing for the inflow cannula (0:00)
After left-sided thoracotomy and opening of the pericardium, the animal (in this case a calf, 120 kg), was connected to the heart-lung-machine via the femoral artery and the right atrium using a standard technique. After luxation of the heart a full-thickness cruciate incision at the typical LVAD insertion side at the LV apex was made using an 11-blade scalpel. Using the Heartware© apical coring tool, the apical core was created using a standard technique. Subsequently, 8-12 pledged, double-armed polypropylene sutures were inserted for the HVAD sewing ring at the LV apex (Video 1). The HVAD sewing ring was then connected to the previous prepared HVAD pump and fixed with the Heartware© sewing ring wrench. The cone-shaped prosthesis was pushed over the inflow cannula and fixed with a silk ligature (Figure 1).
2 – Implantation of the HVAD with the prosthesis in the LV cavity (1:53)
The fixation sutures of the HVAD suture ring were placed through the Dacron part of the ring and the prosthesis and the inflow cannula were inserted in the LV. Next, the sutures of the sewing ring were tightened down (Video 2).
3 – Opening the left atrium and suturing the prosthesis to the mitral valve annulus (4:41)
After reluxation of the heart, the left atrium was opened via the left atrial appendage and the cone shaped part of the prosthesis was sutured to the mitral valve annulus using a 4-0 prolene running suture (Ethicon Inc., Somerville, NJ). With this suture we excluded the LV completely and transformed the original LVAD into an LV replacement device (Video 3). Here it is crucial to measure the right annulus diameter and the length of the LV cavity from mitral valve annulus to the LV apex beforehand via cardiac computed tomography (CT) or transesophageal echocardiography (TEE) to avoid kinking in a too-long prosthesis or tractive forces of a too short prosthesis.
4 – End-to-side anastomosis of the outflow graft to the aorta (6:39)
After closure of the left atrium with a 4-0 prolene running suture the ascending aorta was side clamped and the outflow-graft of the HVAD was end-to-side anastomosed with a 4-0 prolene running suture in standard fashion after cutting to the right length (Video 4).
5 – Final result after decannulation of the heart-lung machine (7:24)
After de-airing via the clamped outflow graft the heart-lung machine was reduced while the LVAD rpm was increased accordingly. Decannulation of the arterial and venous line was performed and protamine was given in standard fashion. In the initial phase it is crucial to regulate the LVAD flow beside arterial pressure and echocardiography via central venous pressure and a left atrial pressure catheter (Video 5). As with every LVAD system, it is crucial to maintain good right ventricular function with optimal fluid status, continuous TEE monitoring during weaning of the heart-lung machine, optimal pacing with the epicardial pacing wires, and prevention of arrhythmia.
6 – Hemodynamic monitoring (7:34)
Hemodynamic monitoring with adequate mean arterial pressure (red line), left atrial pressure (yellow line) and heart frequency (green line). The pulseoxymetry (blue line) could not be measured due to the laminar continuous flow.
7 – Postoperative imaging (7:49)
Echocardiographic view of the permanently closed aortic valve.
8 – Exercised heart with opening of the left atrium and the LV cavity (8:03)
Outcome
So far 4 animals (3 pigs, 1 calf) have undergone this novel LV-excluding technique. All 4 animals survived the procedure and the heart-lung-machine could be weaned successfully (Video 5). In all animals protamine was given and no thrombosis was seen before terminating the experiment after 1 to 3 hours with the pump running. The hemodynamic monitor shows stable hemodynamics with adequate mean arterial pressure (Video 6). Transthoracic echocardiography showed a closed aortic valve and maintained flow in the aorta (Video 7). The excised heart showed no thrombus formation in the prosthesis with a small amount of thrombotic material in the excluded LV cavity (Video 8).
Discussion
LVAD support changes the natural blood flow path through the heart, introducing different flow patterns, which result in stasis . After a proof-of-concept paper with an MR-compatible LVAD inflow cannula in an ex vivo porcine heart failure circulation model, which was the first to derive LVAD flows by 4D Flow MRI acquisitions , the aim was now to set the stage for testing the approach in in vivo animal experiments. In these acute animal models our technique maintained an adequate hemodynamic. The left ventricle contracted around the ring-reinforced prosthesis without output, because the aortic valve was constantly closed. No shifting of the septum was seen and the right ventricular function was preserved all times. Further, no arrhythmia developed. However, further chronic in vivo studies are warranted to further investigate the efficacy of the function of the LV-excluding approach in the long run.
In conclusion, this novel approach has the potential to implant a conventional LVAD system as a single left heart replacement without affecting right heart function.
- McMurray JJ, Adamopoulos S, Anker SD, Auricchio A, Bohm M, Dickstein K, et al. ESC guidelines for the diagnosis and treatment of acute and chronic heart failure 2012: The Task Force for the Diagnosis and Treatment of Acute and Chronic Heart Failure 2012 of the European Society of Cardiology. Developed in collaboration with the Heart Failure Association (HFA) of the ESC. European journal of heart failure 2012;14:803–869.
PubMed Abstract | Publisher Full Text - Klotz S, Meyer-Saraei R, Frydrychowicz A, Scharfschwerdt M, Putman LM, Halder S, et al. Proposing a novel technique to exclude the left ventricle with an assist device: insights from 4-dimensional flow magnetic resonance imaging. European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery 2016.
PubMed Abstract | Publisher Full Text - May-Newman K, Wong YK, Adamson R, Hoagland P, Vu V, Dembitsky W. Thromboembolism is linked to intraventricular flow stasis in a patient supported with a left ventricle assist device. ASAIO J 2013;59:452–455.
PubMed Abstract | Publisher Full Text - Wong K, Samaroo G, Ling I, Dembitsky W, Adamson R, del Alamo JC, et al. Intraventricular flow patterns and stasis in the LVAD-assisted heart. Journal of biomechanics 2014;47:1485–1494.
PubMed Abstract | Publisher Full Text - Wong KK, Cheung SC, Yang W, Tu J. Numerical simulation and experimental validation of swirling flow in spiral vortex ventricular assist device. The International journal of artificial organs 2010;33:856–867.
PubMed Abstract
This study is supported, in part, by grant no. F/45/13 from the German Foundation for Cardiac Research.
The authors have no competing interests.
Authors
Stefan Klotza, Roza Meyer-Saraeia, Alex Frydrychowiczb, Michael Scharfschwerdta, Andreas Koertgea, Leon M. Putmana, and Hans-Hinrich Sieversa
Author Affiliations
aDepartment of Cardiac and Thoracic Vascular Surgery, University Hospital of Luebeck, Germany
bClinic for Radiology and Nuclear Medicine, University Hospital of Luebeck, Germany
Corresponding Author
Stefan Klotz, MD
Dept. of Cardiac and Thoracic Vascular Surgery
University of Luebeck
Ratzeburger Allee 160
23538 Luebeck
Germany
Phone: +49-451-500-2108
Fax: +49-451-500-2051
Email: stefan.klotz@uksh.de
© The Author 2016. Published by MMCTS on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
