10/19/16

Things have been very busy recently, and it's now more difficult for me to make time to craft lengthy, in-depth weekly posts, or get the OR time to put them together at all. This is a departure from eight or so months of (what I'd call, at least) consistent content, and I hate to be abandoning that. I'll be moving to a bi-monthly schedule proceeding into the winter--save for special announcements and things of that nature. However, there's no shortage of posts on this blog, so if you're new here, feel free to browse around!

Today's case was a redo mitral valve replacement. I'm not sure about the context, or why Dr. Nguyen decided to repeat the procedure, but the patient's condition must have been concerning enough to merit it. Having never seen a redo before, this case was interesting-- the fallout from the previous surgery was very visible. Still-recovering myocardial tissue showed blackened marks from the last case's cautery burns. I arrived before bypass, and progress was still being made to expose the aorta for the start of that procedure. I did a general overview of mitral replacements last post, so I thought it'd be fun to get into the true details of the surgery-- for example, bypass prep (e.g., cardioplegia use). To start on that, Dr. Nguyen usually uses retrograde cardioplegia instead of antegrade-- the difference being cannulation through the right-atrium-feeding coronary sinus, instead of the aortic root's coronary artery. Today was no outlier, and he went retrograde; this was done in hopes of maintaining certain heart conditions proceeding into the replacement. Retrograde delivery arrests the heart more slowly, and generally, antegrade is only safe for all patients (especially those suffering from aortic regurgitation) if administrated in tandem with retrograde. Myocardial damage can occur if it is used alone.

After bypass is wrapped up, the tissue surrounding the heart is held open with lengths of suture thread, pressed against the chest cavity, to make room to maneuver about the myocardium and secure an opening for the pump(s). Saline sprays and a vacuum are used to facilitate the removal of blood, and ensure a clear attachment from the pump to the opening.The draw pump tube, situated at the inferior vena cava's opening into the right atrium, is noticeably wider in diameter than the push pump at the aortic arch; I'm not sure why this is. I found a lot of good information about the more detail-heavy aspects of bypass on this website, so definitely take a look at that. It probably does a better overview of it than I have over the course of my many posts, and is all in one place to boot:

 https://www.openanesthesia.org/technical_aspects_of_cardiopulmonary_bypass/

Jumping further into the case, the mitral entrance Dr. Nguyen picked  was...interesting. Three scoop-like metal supports, ringing the chest retractor and extending into the sternal incision, were used to hold the heart up and rotate it to the left in its cavity. This provides a very narrow pathway from under the right side of the heart to the mitral valve, and it's probably the most difficult-looking task I've seen in the OR (yet). Standard tools can't be used to remove the valve, simply because of how deep down it is-- the task calls for specialized elongated cutting instruments.

The next phase of the Heartwell Project is set up and ready to go, though I'm a bit tired of giving "soon, guys!" updates about it. Early November is our target launch window, and has been for a few weeks now. I might not talk about it until then.  

9/28/16

Despite being quite a standard day at the HVI, I got to see (a part of) a case that I haven't seen in a while-- an open-heart mitral valve replacement. A mitral replacement is performed to counter calcification or other interruptions to blood flow in the mitral valve, and replaces the defective valve with a prosthetic or biological one. This is a fun surgery to watch, as its procedure doesn't leave much to the imagination. First, the sternum is split with a saw in an incision 3-4 inches in length, and underlying tissues are then bisected length-wise to get a decent view of the heart. Cardioplegia is administered to slow the heart and prepare for bypass. The cardiopulmonary bypass machine is used to pump blood throughout the body in place of the heart, and reoxygenate it without the use of the lungs; it does this by cannulating the vena cava or right atrium to draw out deoxygenated blood, oxygenating it outside of the body, and then feeding it back into the ascending aorta. This allows for the attending surgeons to operate on a still heart and chest, which is pretty useful. Going further, an incision is made in the heart's left atrium, exposing the mitral valve. After removing the diseased valve leaflets and annular tissue, there is a long preparation for the new valve's insertion into the mitral space. I like to call it "scaffolding": a ring of sutures is sewn into the tissue, and then used to lower in the replacement valve. I'll include a picture of this (a).

Arriving at the tail end of the surgery, I missed all of this, and saw more of the cleanup process than anything else. The patient soon finished being weaned off of the bypass machine, and the final sutures were performed in the chest cavity. Shortly after, chest tubes were inserted into the mediastinal cavity to help with post-op fluid drainage. In the days following an invasive surgical procedure, a mixture of body fluids will leak from the damage done to the tissue inside the chest-- the chest tubes provide a place for that fluid to drain to, preventing against nasty infections and other complications. Valuable, but a bit gross nonetheless. One might also wonder how the sternum is pieced back together after being sawed in half, which yields a more complicated answer than one would expect. Well, metal wires are looped through the tissues directly adjacent to the center of the sternum, then cut before another loop is made. This results in multiple horizontal lines of wire, running under both sides of the sternum and out through the left and right breast.These lines are then crossed and twisted until the two pieces of the sternum meet. After this, the excess pieces are clipped, and the performing surgeon tightens the twisted wires as they see fit. The wire-ties are then pressed down and into the surrounding tissue. It's almost like heavy duty suturing, but is a bit hard to explain without a picture-- see below (b). A standard sealing/suture procedure reattaches  the tissue above the sternal plate back together, ending the surgery. 

The solicitation letter for the next phases of the Heartwell Project has been finished, but Dr. Nguyen has been rather busy recently, and hasn't had a chance to give any input. We aim to use his minivalve web domain to host information about fundraising, and use as an ancillary viewing platform to our YouTube channel if/when the videos are ready.


Ex. A.

Ex. B.