On the road to immersion (Week 3)

 

This week I learned about the different methods of performing surgery to implant ventricular assist devices (VADs). Implantation of VADs requires access to the heart, and the methods to do so are median sternotomy, bilateral thoracotomy, and (rarely) mini-sternotomy/L thoracotomy. Understanding these procedures requires having in mind the final configuration of the left ventricular assist device (LVAD) in the body (Fig. 1). Figure 1 shows a patient hooked to an LVAD and its supporting components. The LVAD in the figure is the pump (cap-like structure attached at the apex of the heart) which re-routes the blood from the left ventricle to the ascending aorta (essentially, the device takes over the function of the native heart’s ventricular contraction).  

Figure 1: The HeartMate 3 left ventricular assist device (LVAD) from Abbott laboratories. Note that except for the LVAD (marked a 1 in the image) all other components are extracorporeal. Image source: https://www.cardiovascular.abbott/us/en/hcp/products/heart-failure/left-ventricular-assist-devices/heartmate-3/about/system-overview.html

Of the three techniques mentioned above, median sternotomy is the most common surgical procedure to perform VAD surgery. Median sternotomy is a surgical procedure by which an opening in the middle of the chest at the breastbone (sternum) is created to access the chest cavity (see Fig. 2a). Post sternotomy, several complications include sternal wire fracture or rotation, osseous fracture, cartilaginous fracture, sternal dehiscence (reopening of the sternal incision made during the procedure), post-operative hematoma (pool of clotted blood in the body space), and infectious complications. In addition, many patients undergoing median sternotomy for heart surgery suffer from persistent pain in the sternal area, defined as chronic post-sternotomy pain. The pain may extend well past the rehabilitation period. In light of the post-operative problems of sternotomy, the other two non-sternotomy techniques are increasingly gaining interest among surgeons. In these procedures, the sternum is intact, and instead of one big incision, two small incisions are made to access the heart apex and aorta. A qualitative estimate of the location of the incisions is shown in Fig. 2 (b & c). Due to their many advantages like fewer sternal adhesions, postulated preservation of right ventricular function by preventing distension, less bleeding, and faster recovery procedure. 


Fig. 2: Accessing the heart and ascending aorta through different surgical techniques. A) Median sternotomy; B) partial upper-sternotomy and left anterolateral thoracotomy; C) Bilateral thoracotomy. Image Source: Nersesian G, Potapov E, Starck CT, Nazari-Shafti TZ, Kofler M, Kempfert J, Falk V, Van Praet KM. Surgical Implantation Techniques of Modern Continuous Flow Ventricular Assist Devices. Surg Technol Int. 2021 May 20;37:263-269. PMID: 33463696.

In recent years, inflow cannula angle of the LVAD has been attributed to the increased prevalence of strokes in patients with VADs. Therefore, it will be interesting to see whether a specific surgical procedure influences the inlet cannula placement and angle. In the next few weeks, my job will be to look at CXRs (chest X-rays) of a particular group of patients (who have undergone one of the three types of surgeries discussed here) and figure out the inlet cannula angle relative to the axis of the heart. The aim is to start a pilot study in this direction, and for this, I have been brainstorming with Dr. Yoshifumi Naka and Dr. Irina Sobol (my mentor) on the best way to proceed with our project. In particular, we are contemplating whether 1-view CXRs (anterior-posterior view) is sufficient for the correct deduction of cannula angles, or do we also need lateral views? I am very excited about this project, and will be posting more on this in the upcoming weeks.   


-Abhishek




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