Saturday, April 30, 2016
OF THE HEART
In surgery there have been certain periods when advancement in knowledge and technical inventions have had a marked effect on our life and the surgeon’s ability.
Two "quantum leaps" occurred in the late 19th century, which together allowed the transition to modern surgery. The first great advancement was the discovery and use of anesthesia especially Ether to enable the surgeon to work without causing pain and the inevitable accompanying shock which would be life threatening. Subsequent new agents and newer delivery methods have eliminated the bad effects of the original drugs.
An appreciation of the germ theory of disease led rapidly to the development and application of antiseptic techniques in surgery. Antisepsis, which soon gave way to asepsis, reduced the overall morbidity and mortality of surgery to a far more acceptable rate than in previous eras.
The next major advancement was as the result of the Spanish Civil War when an understanding of shock and its treatment in traumatic injuries proved to be lifesaving.
In the post WWII era starting in the late 50s a combination of better anesthesia techniques and shock support plus a better understand of the body’s hemostasis led to greater surgical advances to the point where we can now even transplant organs. Included in these advancements were the use of new visual tools as well as the computer and micro-surgical development; so called minimal or non-invasive.
The first Heart valve replacement happen in the 1960’s It was a rather brutal procedure and took a such a great toll on the body that the majority who needed the operation the most; especially the elderly (over 70) had little chance of surviving the operation. I am unawares of anyone in the 80s being offered the procedure.
The operation was done by splitting the sternum (breast bone) down the middle. Then the heart is exposed, the pericardium is opened, and the patient is put on a cardiopulmonary bypass machine, also known as the heart-lung machine. This machine takes over the task of breathing for the patient and pumping their blood around while the surgeon replaces the heart valve. Before its invention the heart continued to beat and made it difficult to place the valve. A further advancement was the addition of the use of hypothermia; lowering the body temperature.
Early adoption of this technique proceeded slowly based on the limitations of available replacement valves and relatively primitive techniques for protecting the heart during surgery which were available at the time. With the evolution of mechanical heart valves and gradual developments in cardiopulmonary bypass (the heart lung machine) and cardioplegia which allow the heart to be stopped safely during surgery, aortic valve replacement became accepted therapy for patients with severe aortic insufficiency and /or regurgitation.
Once the patient is on bypass, a cut is made in the aorta and a cross clamp applied. The surgeon then removes the patient's diseased aortic valve and a mechanical or tissue valve is put in its place. Once the valve is in place and the aorta has been closed, the patient is taken off the heart-lung machine. Transesophageal echocardiogram (TEE, an ultra-sound of the heart done through the esophagus) can be used to verify that the new valve is functioning properly. Pacing wires are usually put in place, so that the heart can be manually paced should any complications arise after surgery. Drainage tubes are also inserted to drain fluids from the chest and pericardium following surgery. These are usually removed within 36 hours while the pacing wires are generally left in place until right before the patient is discharged from the hospital.
Recovery from this operation usually takes about 3 months or more.
As medical procedures evolved cardiac cauterization became standard and not only could the heart’s blood vessels be visualized but the placing of stents instead of open heart coronary heart surgery became possible and a common treatment.
In 2011 only 5 years ago, the first aortic valve was replaced by using a catheter inserted through the femoral artery and passed into the heart. Hospitalization was now no more than 5 days if there were no complications which were much less than in open heart replacement. Now those in the 80s could be treated instead of facing rapid progressive heart failure. Within a week or two the patient could depending on his/heir’s status resume normal life.
These valves folded up so that they could be passed through the catheter and were then open when in the area of the valve to be replaced and anchored into position. They consisted of a metal framework covered with a “plastic" and the valve itself was usual from pig tissue. The metal frame help anchor the valve in place.
The operation is called Trans Aortic Valve replacement (TAVR).
Today a new and better valve for many reasons is undergoing clinical trial in the USA although it has been in use in Europe for about 2 years. It has no metal and is secured in place by expanding it as if it were a balloon and then hardening polymer is injected to fix it in place. If the surgeon does not like its initial positioning he deflates the balloon and reposition it under the ultrasound and fluoroscope guidance before injecting the fixing agent.
It will be only be a matter of time when all valve replacement will be done by this less traumatic method.