Artficial Heart Valves (인공 심장 판막)
The heart contains four valves that open and close to maintain the flow of blood in one direction. If one or two of those valves become diseased, narrowed, or unable to close all the way, bloodflow can become limited and pressure can build up in the lungs. Sometimes a valve can be repaired, but often it needs to be replaced to keep the heart pumping smoothly.
심장에는 혈액의 흐름을 한 방향으로 유지하기 위해 열리고 닫히는 4 개의 판막이 있습니다. 이러한 판막 중 하나 또는 두 개가 병에 걸리거나 좁아 지거나 완전히 닫히지 않으면 혈류가 제한되어 폐에 압력이 쌓일 수 있습니다. 때로는 밸브를 수리 할 수 있지만 심장이 원활하게 펌핑되도록하려면 종종 교체해야합니다
In the early 1950s, scientists began replacing diseased heart valves with acrylic ones. Surgeons performed the procedure on several patients, but the valves failed to regulate bloodflow properly and clotting and swelling often occurred. Over the next few years, scientists attempted other artificial implants to replace the mitral and aortic valves―the two harder-working valves on the left side of the heart, which pumps blood through the body. Design criteria were important: The materials had to be compatible with human tissue, and the valves had to open and close rapidly and be able to function for many years.
1950 년대 초 과학자들은 병에 걸린 심장 판막을 아크릴 판으로 교체하기 시작했습니다. 외과의는 여러 환자에게 시술을 시행했지만 판막이 혈류를 제대로 조절하지 못하고 응고 및 부기가 종종 발생했습니다. 그 후 몇 년 동안 과학자들은 다른 인공 임플란트를 사용하여 승모판과 대동맥 판막 (심장 왼쪽에있는 두 개의 더 강하게 작동하는 판막)을 대체하여 혈액을 신체로 펌핑했습니다. 설계 기준이 중요했습니다. 재료는 인체 조직과 호환되어야하고 밸브는 빠르게 열리고 닫히고 수년 동안 작동 할 수 있어야했습니다.
The advantages of using human tissue to create heart valves became evident in 1962, when the English surgeon Donald Ross implanted the first heart valve harvested from a dead body: The immune system proved less likely to reject human tissue, and clotting was less likely to occur. The limited supply of cadavers, however, necessitated a search for other tissue substitutes, and in 1965, scientists first reported on five successful surgeries in which they'd implanted heart valves made from pig organs.
영국의 외과 의사 인 도널드 로스 (Donald Ross)는 시체에서 수확 한 최초의 심장 판막을 이식했을 때 1962 년에 인간 조직을 사용하여 심장 판막을 만드는 이점이 분명해졌습니다. 면역 체계는 인간 조직을 거부 할 가능성이 적었고 응고가 덜 발생했습니다. . 그러나 시체의 제한된 공급은 다른 조직 대체물에 대한 검색을 필요로했으며 1965 년 과학자들은 처음으로 5 개의 수술로 돼지 장기로 만든 심장 판막을 이식했다고보고했습니다.
Today, patients have a choice between mechanical and biological valves. Mechanical valves are made from synthetic materials such as carbon, polyester, and titanium. They are durable and reliable and they last a long time, although patients need to take blood-thinning drugs to prevent clots from forming. Biological valves, made from cow or pig tissue (called a xenograft) or a donated human heart (called an allograft or homograft), must be replaced every 10 to 15 years. They are generally recommended for elderly patients or patients who cannot take blood-thinning medication. Sometimes a patient's own tissue can be used for valve replacement (called an autograft or a Ross prodedure).
The noise made by the acrylic heart valve replacements of the early 1950s was disconcerting to patients―reminiscent, some said, of a ticking time bomb.
The average heart beats 60 to 90 times per minute, or more than 31 million times a year.
Before the heart-lung machine was developed (see page 280), surgery on heart valves could attempt repair but not replacement. The surgery had to be done very rapidly on a still-beating heart.