Week 2

This week, I saw an aortic dissection surgery. As discussed last week, an arterial dissection is when there is a partial tear in the lumen of an artery, creating a second cavity. This second cavity in the artery, called the “false lumen,” propagates as blood pools and can form a second blood-flow pathway in the vessel. This second pathway can block flow in the true lumen (the original lumen of the vessel), or rupture and result in massive blood loss. The patient we saw had a dissection that blocked much of their aortic blood-flow and pressed against the aortic valve. Because of the pressure from the dissection, the patient’s valve could not open and close correctly. Additionally, the patient had substantial clotting around the dissection. The size of the clots removed was very surprising to me- there were pieces that were multiple inches thick!

Dr. Tranbaugh treated the dissection using a “sandwiching” technique, where two pieces of surgical felt are used to press the true lumen to the false lumen from the inside and outside of the aorta. He did not surgically close the entire dissection, just the section in the aorta. The hope with this treatment is that once the main tear of the lumen is repaired and blood-flow is re-established in the true lumen, the dissection will slowly heal or will at least cease to grow.

I also saw an aortic valve replacement surgery this week. The replacement valve was made from bovine pericardium and had a cloth-like material surrounding it for suturing. The suture technique for attaching the valve was very intricate- there were 20 thread lines inserted and each line had to be kept straight to avoid entanglement.

An aortic vascular graft was used to close the aorta for both surgeries I saw this week. The graft is made of a heavy cloth-like material called Dacron. One major challenge of the surgeries was controlling bleeding around the sutures connecting the graft to the native aorta. Many techniques were employed to stop the bleeding, including pressure, application of topical clotting agents, and administration of protamine, a drug that counteracts the anti-coagulation effects of heparin.

One interesting phenomenon that I saw this week was the left ventricle of the heart can contract when it fills up with blood, even though the electrical action potential of the heart has been disrupted using potassium. Dr. Tranbaugh also said that sometimes when the heart is blocked or in cardiac standstill he can tap the heart and the ventricles will contract. This mechanically induced heart contraction reminded me of two projects that I did in undergrad with cardiac stretch-activated ion channels. I wonder if there is a way using a mechanical stimulation pathway, possibly with electroactive mechanically-stimulated polymers instead of pacemaker lines, to restore contractility in post-op patients.  

I also started working on my research project this week. The project is comparing long-term survival of diabetic and non-diabetic patients from 2015-2018 who had varying treatments for multi-vessel disease (MVD). I will be looking at three groups- single left internal mammary artery (LIMA) graft CABG patients, multiple arterial CABG graft patients who had a LIMA graft and at least one radial artery (RA) graft, and patients that had drug eluting stents (DES) inserted instead of CABG. I spent most of this week learning medical record terminology and figuring out how to code conditions to automatically extract patients that fall under one of our treatment groups in excel. Eventually, this data will be combined with data that Dr. Tranbaugh had previously compiled from another hospital.