Science Reporter; 19; The Heart-lung Chain

This is a valve of the heart. In five out of a hundred people in the United States, one of these valves is diseased. Until 1955, nothing could be done for these people. But now, because of open heart surgery and the heart lung machine, many of them can lead normal, healthy lives. This is our story today on Science Reporter. Hello, I'm John Fitch, MIT Science Reporter. This is the Veterans Administration Hospital in West Roxbury, Massachusetts. It's one of the six Veterans Hospitals in the country in which open heart surgery is performed. Open heart surgery is a job for experts. These men train for at least 15 years, four years of medical school, one year of internship,

five years of residency, two years in chest surgery, and additional time in cardiac surgery, with many examinations along the way. So it's not surprising that there are only about a hundred open heart surgeons in the country. One of these is Dr. Ernest Barcemian. He completed his training over seven years ago. He now performs an average of two open heart operations a week, and still he has a four -month waiting list. Dr. Barcemian is chief of thoracic surgery here. He's on the faculty of Harvard Medical School and on the surgical staff of Boston City Hospital. We met with Dr. Barcemian in one of the operating theaters here at Veterans Hospital and asked him what heart diseases require open heart surgery. Diseases that require open heart surgery are usually ones that cause these orders in the valves of the heart or in the walls that separate the chambers of the heart. This is a model of a heart. The heart is an organ the size

of a large fist. It has two receiving chambers and two pumping chambers. Now these diseases that require open heart surgery may be either congenital that is where born with them or they're acquired. An example of a congenital lesion that requires open heart surgery is a hole in the wall that separates the left from the right pumping chambers. This is that wall and this is where we may have a hole. Now this would require an open heart operation and the operation would be to close the hole. An example of an acquired disease is one that affects the aortic valve. This is the valve that communicates between the left pumping chamber and the aorta. This is the big vessel that takes the pure blood to the rest of our body. You can see this aortic valve right here. It's composed of three leaflets and the diseases that may cause these orders in it may either narrow

it or may cause a leak in it. Again we need open heart surgery to either correct the narrowing by widening it or correct the leakage usually by replacing the valve. Now how do you know whether a patient has one of these heart diseases? Well the patient that has a congenital heart disease is usually a child. Maybe born as a blue baby or gets a blue color later on he may fail to thrive. The doctor will hear a murmur in his heart. What do you mean by a murmur? Normally when the blood passes through the valves normal heart sounds are heard. When there is a deformity in the valve the blood causes turbulence and this results in a strange noise that we call murmur. In the acquired variety of heart disease the symptoms may be getting tired easily being short of breath or having chest pain or fainting. Again the heart may be enlarged or the doctor will hear a

murmur. Once a complete history and the complete physical examination are made then we take X -rays of the chest and the heart and electrocardiograms. All these however aren't enough. We do more elaborate tests and we are standing now in a room which is the cardiopulmonary laboratory of this hospital. By the way this is probably the best staff and best equipped laboratory of its kind in this area. Here the patient comes, is put on this table. A catheter or a little pipe is passed through his vein into the heart and samples of blood from the various chambers of the heart are taken. Pressures are measured, oxygen is measured and then a dye is injected and films are taken very rapidly to show the movement of the heart during one beat. This will refer to as cardiac catheterization and electrocardiograms. Now once you've determined that a patient has such a heart disease and how do you decide whether or not to operate? Well this can be sometimes a very difficult

decision but what we do is usually we hold a conference between the medical cardiologists in our hospital. This consists of Dr. Litman and Dr. Sasa Haram and us surgeons, Dr. Warren and myself. We decide whether the risks of the surgery are weighed against the incapacitation of the patient. What his long term outlook is against how much he will derive benefit from the surgery. All these are weighed and the judgment is made whether surgery should be offered to that patient or not. As I say sometimes this decision can be difficult. But once you have decided to go ahead with an operation you actually cut right into the heart, leave it open. Exactly. We have to cut right into the heart and leave it open. And this is why we need a heart lung machine to take over the functions of the lungs and the heart to give us a dry field without blood, give us a quiet heart where we can do the surgical correction accurately. How do you go about it? Well it's probably easier to see this and we have a movie to illustrate the technique using the heart lung

machine. This film was prepared by Dr. Gordon Scannell and Jerry Austin at the Massachusetts General Hospital in Boston. We are seeing a patient on the operating table and the operation has just started. The skin incision is made in the midline cutting the sternum which is the big bone in front of our chest. This has been cut and the chest is now open. You are seeing faintly the beat of the heart through its covering which is called the pericardium. This will next be cut. You see the lungs on both sides of the heart coming into view. Now this film is really a condensation of a six hour operation in the next six or eight minutes. The pericardium which is the covering of the heart has been opened and it's being attached to the edges of the skin

incision to improve the exposure to the heart. Just to keep it out of the way. That's right. Now you're looking at the heart. The hand was on the heart. You see the heart beating. Some of these movements may look crude to you. Somebody handling a delicate heart rather crudely. Actually these moves are all calculated and very deliberate. Now the patient is being prepared to be put on bypass. You can see this big catheter that was passed into one of the receiving chambers we talked about which is to drain the blood from the heart into the heart lung machine. This catheter now really is placed in what we call the right atrium and it will be connected to the oxygenator of the heart lung machine. Is this where the blood would normally be coming into the heart? This is the blood where the blood would be coming from all our body into the

heart before it goes to the right pumping chamber to go to the lungs to be oxygenated. This is a view of the oxygenator. This is one of the most common forms of oxygenator use. It's called the disc oxygenator. So the blood comes from that tube that we saw that was inserted in the vein and now is going to this machine? That's right. What you're seeing here like fingers moving is really the pump. This is referred to as a sigma motor pump and it's like fingers playing on a piano compressing that tubing in between and pumping the blood forward in that manner by a successive compression of the fingers against each other. I see since the heart is being bypassed you must actually pump the blood for the heart. That's right. The heart lung machine actually consists of the oxygenator and the pump. The oxygenator replacing the function of the lungs, removing carbon dioxide and giving oxygen and the pump replacing the function of the heart proper. These discs are adding the oxygen to the heart? Yes.

Each of these discs dips in a pool of blood at the bottom of the oxygenator. It picks up that film and is exposed to an atmosphere of oxygen and therefore oxygenation is accomplished in that manner. We're back to the heart now. This tip you see going in and out is the suction which is used to take out any excess blood. This is the aorta. This is the big blood vessel that carries the oxygenated blood from the left pumping chamber to our body. It's being opened now and right in the middle of the screen you're looking at the aortic valve. You can see that the heart has gradually stopped beating. Does it do that by itself? No, this is done by cooling it. When the temperature of the heart falls below 15 degrees centigrade it will

stop beating. But it's been bypassed now so the patient is alright. It has been bypassed and this is why you are able to open this big blood vessel without flooding the operating room with blood. What they're doing now very carefully is reaming the calcium which was involving the valve and really replacing most of the tissue of the valve causing the valve to be strictured. This is one of the valves where the main lesion is narrowing and they're trying to reem out this excess calcium and cut out the excess fiber tissue to open the valve. Now these valves are very rigid. When you remove the calcium they become pliable and you can see that they have removed it already and the cusp that was very rigid you see how it's moving when the instrument is placed over it. This is now irrigating it to remove all the excess calcium. So when this hole in the big blood vessel is closed there will not be calcium flying to the rest of our body especially the brain and it may cause what we call a stroke. So it's important to remove

all those calcium debris and the operation has just been concluded. The opening in the big aorta is being closed now. During this procedure the patient is given a drug which is called heparin. This drug prevents the clotting of the blood. This is important because although in our bodies we don't need something to prevent clotting of our blood. When we are taking the blood outside the body it will tend to clot unless we use the stroke so that this patient has the stroke now. When the operation finishes and the catheters are removed from the heart and another catheter which was connecting the pump to the arterial system when both are removed a counter drug will be given which is called protamine to restore the normal clotting mechanism of the blood. What was that little disc that I just saw in the picture which was pushed up against the heart? Was that to get it started again? Yes. Now the heart has been cooled when it is being rewarmed now it will first go into fibrillation which are little twitches like little worms, many worms playing in the muscle of

the heart. This hand now is massaging the heart to try to improve the blood supply to it and that little disc you saw was a defibrillator. This is an electric current that is passed quickly through the heart to remove all those little fibrillations and synchronize them into a regular beat. You saw it going into the screen again. Sometimes this has to be repeated a few times when you are fortunate the first time will do it and restore a good beat. You can see that when the heart starts beating the beat is not very orderly it takes a few beats before it will really restore good strong rhythm. The patient is taken on and off bypass as we say that means the patient's heart and lungs have been put to rest and the pump oxygenator is used. Before we do this completely we put the patient on partial bypass that is to say some of the blood still passes to the

patient's own lungs and through his own heart but some of it passes through the artificial heart lung machine. When we see that everything is set factory then we put the patient on total bypass which means all the blood goes through the artificial circuit consisting of the oxygenator and the pump. Now you can see that the heart has resumed a good beat and these are the catheters that have been put in the drain the veins. In the black and white I don't know that you could visualize the difference between the oxygenated blood that was returning to the patient and the impure blood that is darker in color but on a colored film this would be shown very clearly. Now you can see the beat of the heart improving in fact this is a rather fast rate normally the heart beats about 60 to 80 beats a minute. You know John all that long six hour operation did was remove a few specks of calcium that you could easily put on your finger yet

that was enough to make a well patient out of a sick patient. Dr. Barçamian one thing I notice is that this is a heart lung machine now since you're only operating on the heart why can't you use the patient's own lungs. Well the heart has two pumping chambers really one pumps blood to the lungs to be oxygenated and the blood that comes back has to be pumped again to the rest of the body. If we only bypass the heart we have to use two pumps two circuits for connections by bypassing the heart and lungs together we use one pump and one circuit and only two connections to the patient. Well now does this heart lung machine that we've seen in the film meet all of your expectations. Well I think it does a fairly adequate job in elective surgery but it doesn't meet all our expectations. It has several drawbacks one of them is that it needs eight points of blood just to prime it. Now that means you have to have eight donors just before operation to give blood. You prefer to use a fresh blood? Yes.

Now with the blood being used that large amount the hazards of mismatching the hazards of serum hepatitis later on are all compounded. In addition the pump is too big to be assembled and sterilized in the assembled form. This plus the blood factor make it impractical for use in emergencies. I think heart lung machines have a great field to be used in emergencies. Well now what would you like to see in an ideal heart lung machine? I think an ideal heart lung machine would be one that would be able to oxygenate large quantities of blood and pump large quantities of blood yet do this gently without injuring the blood. I think it would be one that would be portable that would be compact that would be sterilized in the assembled form so that it's ready to use at the moment's notice. I think it would be one that is safe and simple to operate, easy to clean. It would be inexpensive, no maintenance and it shouldn't have too much supervision at the time

of surgery to watch it. It should have built in intrinsic safety mechanisms. Now how does a surgeon who sort of realizes what an ideal machine would be like go about getting one developed and built? Some surgeons have gone through the trouble of designing and building and operating one themselves. I think this accounts for some of the shortcomings of the present heart lung machines. I was fortunate in meeting Professor Samuel Collins of MIT and during our conversations I expressed to him some of my thoughts on heart lung machines and he was kindly enough to volunteer to build one for me. This is Dr. Samuel Collins, Professor of Mechanical Engineering at MIT. The designing and building of a new heart lung machine has been one of his personal projects for several years and to this project he has brought his Yankee ingenuity and considerable patience. This machine is the seventh model Dr. Collins has built to be tested by Dr. Barcemian working with dogs. Between them they have simplified the design and have reduced the number of parts. It will

soon be ready for use in an open heart operation. For the purpose of this demonstration let's imagine this bottle as a man. His chest has been open for heart surgery and we've connected this large tube to a large vein entering the heart and this tube to the arterial system. Blood flows by gravity through this tube into this stainless steel tank, the oxygenator which replaces the lungs during the operation. And from the oxygenator through the float chamber down into the pump which is located here and the blood goes from the pump into this instrument, the deep bubbler. And from the bottom of the deep bubbler to this tube back into the patient. But Dr. Collins, if the blood is just trickling along the bottom of this trough, isn't there danger of getting air bubbles

mixed in with it which that would be fatal to the patient? Yes it would and we've taken special precaution to make sure that doesn't happen. We have a float here which has a valve on the bottom and this falls down into a circular hole and stops the flow of blood when the level gets below a certain predetermined level which is about here. Whenever the blood falls to that level no more blood can go through so it is always sealed. The pump is always sealed against gas by the float valve. I suppose also that means that if you can shut it off you don't have to have a great deal of blood in a reservoir up here. That's right. It makes it possible to get along very much less blood within the machine. It does not require close supervision. Therefore you can get along with a very minimum of blood in the machine. Now after it goes through the float valve it comes down to this pump, I believe you said, now how does that work? Well this pump, you see a stainless steel cylinder

here and within it is a very heavy wall rubber tube closed at the bottom end. We have here a connection for oxygen gas. When the pressure in here is low the rubber tube is extended and it fills with blood. When the pressure is turned on here the rubber tube collapses such as we have here. Squeezes tube, we reduce the internal volume to zero or approximately and the blood is contained and it is forced out into this debubber assembly here. Now why doesn't it just go right back up into the float chamber? Because of valves located one here which permits blood to flow into the pump and one valve here which permits blood to flow out. So this pump is really like a heart then it's complete with valves and everything? Yes, it's very similar to a heart. And then it comes into this debubbler now. What does that do? This

instrument really performs three functions. One being the debubbler, there is a chamber there containing a certain amount of blood. The gas initially in the machine must come through here, it collects at the top and is drawn off through this tube. The blood sinks to the bottom and flows out at the bottom. Once you're in operation there should be no bubbles but in case one should turn up they will float come to the top and come into this tube. Does it have some other functions? I believe that you mentioned three altogether. Yes, there is a strainer here made of fine mesh stainless steel screen. The function of the strainer of course is to remove foreign matter that may biomex them again into the blood. The chief source of such material might be from the scene of the operation where blood which has leaked out is sucked into the system and sometimes there are sutures, sometimes blood clots which must be taken out. What about these pieces of

rubber that are sticking through there? That is a part of our surge chamber, the third function which softens the pulse of the pump. It is spring loaded so that when the pump sends out a strong pulse of blood it is softened somewhat by this. The blood collecting in the chamber, pushing the diaphragm out and that is returned later in the system. Getting back to this large trough here, how do you actually get oxygen into the blood itself? We have a rotating number which fits inside this, the oxygenator. It is a stainless steel cylinder which has been covered with nylon tool. We have two varieties of material, one has been gathered up to make a fluffy arrangement. These are wound on, these are strips about one foot wide and about 12 feet long. They are wound on, rounded around

and tied in position. These provide a lot of surface. Now this rotating cylinder touches the bottom of the trough. This rotates, we will put it in place now and there it is. The nylon material touches the bottom and this little trickle of blood coming down the trough is picked up by this, carried over and over again. This material becomes film with a very thin layer of blood. We have an oxygen atmosphere inside this vessel and there is an exchange of oxygen with the blood through this purpose. You couldn't just get oxygen to go into blood that wasn't in the form of a very thin film. It would be like the lungs itself then. Yes, we are trying to make it as much like the lungs as possible. The rated which oxygen can be taken up by the blood is a function of the area. The greater the area, the more rapid the transfer of blood. This is simply a

means of providing a very great area just as the lungs provide an enormous area by all the little air cells in the lungs. Exactly, how much area would you say you have? There are about 50 square feet here in this surface. As this rotates then, the tool, this nylon material, picks up the trickle of blood from the bottom, brings it up into the oxygen atmosphere at the top and then deposits its back in to go on through the pump. How do you drive all of this? You have to rotate this and you have to pump down there and I believe you said there was another pump. What do you use to drive it? We have a little steam engine here. It can return us around. A steam engine? Yes, for all intents and purposes it is a steam engine. Although we do not use steam to drive it, we have oxygen under pressure here. We need the oxygen for oxygenation. It's capable of doing a lot of work and we make use of a little bit of this work. Because it's under pressure you make it run the machine first and then use it to oxygenate the blood. That's right. Could we see the machine in operation?

Sure, let's turn it around. Back to the way it was. This won't be able to see the oxygen in a rotate. I'll crank up the engine. Sounds just like a steam engine. Normally we would check for air in the system but that's done so I'll turn on the venous blood. That just flows by gravity. That's right. The blood comes from the veins oxygenated here in our artificial lung. Through the pump it is the heart and then back up into the arterial system of the pain. I can even feel a pulse. Thank you very much Dr. Gough. Dr. Barsamy, you've tested this machine. What do you think of it? I've tested it extensively on animals. I think it has fulfilled all the requirements we set for it. I like it. I'm confident it will perform well. I plan to use it soon on a patient in open heart surgery. Well now earlier you mentioned its use in

emergencies. What did you have in mind? One of the commonest causes of death after any operation is what we call pulmonary embolism. This is a clot that goes into the main vessel of the lung and often quickly kills the patient. If we had a heart lung machine that was available for emergency use we could go in, remove the clot from this patient and possibly save it. Do you foresee its use in other types of operations other than open heart surgery? Yes. This week we had a patient at the Boston City Hospital that had a cancer in her leg. What we did is we disconnected the main artery and vein to that leg, hooked them to this machine, put in a strong chemical there to kill the cancer, yet preventing that chemical from circulating throughout the rest of her body. We hope we can use this machine in what we call cancer perfusion. We're having an inexpensive readily available machine. Will that make it possible for more people to have open heart surgery? The machine is only one of many other

factors. You have the factor of well trained surgeons, well trained teams, well trained hospitals to handle this kind of surgery, blood, cardiopulmonary labs, good cardiologists. Simplifying the machine I think is a good first step forward. Thank you very much. We've been talking with Dr. Ernest Barcemian and Dr. Samuel Collins at the Veterans Administration Hospital in West Roxbury. I'm John Fitch, MIT Science Reporter. Dr. John Fitch, MIT Science Reporter. Dr. John Fitch, MIT Science Reporter. Dr. John Fitch, MIT Science Reporter.

Dr. John Fitch, MIT Science Reporter. Dr. John Fitch, MIT Science Reporter. Dr. John Fitch, MIT Science Reporter. Dr. John Fitch, MIT Science Reporter. Dr. John Fitch, MIT Science. Dr. John Fitch, MIT Science. Dr. John Fitch, MIT Science. You