Cardioplegia is the intentional stopping of the heart using cold temperature and chemicals for heart surgery. It was developed in the 1960s and has increased the number of people who can undergo and survive heart surgery. Some surgeons now perform heart surgery without it, using beating heart surgeries for complex procedures.
The expression “stopping the heart” is normally associated with tremendous fright or fear in general. In contrast to this, the idea of cardioplegia is a positive one, although whoever has said they might suffer this is likely to have some anxiety. In the standard definition, cardioplegia is the intentional stopping of the heart using usually cold temperature and chemicals, so that difficult surgery can be performed on it. An alternative definition of this term is when the heart stops due to significant trauma, a much less common event.
Performing complex heart surgery was extremely difficult in the past, and much experimentation eventually led to the development of cardioplegia at about the same time as heart-lung bypass machines were being perfected. London doctor Dennis Melrose is credited with creating the ultimate key to stopping the heart by proposing an injection that could be used to effectively halt its function. Yet there are many physicians along the way who have contributed to the sum total of knowledge needed to evolve this technique. For example, heart-lung bypass had to be developed simultaneously, so that the circulation of blood and oxygen could continue, even if the heart was not beating. Historically, these innovations enabled “stopping heart” surgery starting in the 1960s, dramatically increasing the number of people who could undergo and survive heart surgery.
What occurs during cardioplegia can vary depending on the surgeon’s preferences. Most people get cold after anesthesia and blocking the aorta cuts off circulation to the heart. Circulation is redirected to a heart-lung bypass machine. The surgeon gives an injection of a solution that stops the heart completely, creating “plegia” or paralysis. The essential purpose of inducing this state is to avoid life-threatening complications such as the development of blood clots or ischemia.
Of course, what is achieved in cardioplegia must be reversed after surgery. If hypothermia has been induced, the body is slowly warmed through a variety of methods and, when it is at the appropriate temperature, a shock is given to the heart to begin beating. Removing the clamp from the aorta and removing the person from heart-lung bypass restores normal circulation. In many circumstances, these difficult steps are accomplished with great ease, but there can be complications along the way.
In fact, although cardioplegia has existed as the standard method of heart surgery for nearly four decades, there are now many surgeons performing heart surgery without it. A number of beating heart surgeries are not preferred to complete induction of cardiac paralysis. Some of these are extremely complex, used to repair or mitigate some congenital heart defects. The Fontan extra-cardiac duct is one example, and there are many others, including some forms of arterial bypass or graft. It’s possible that cardioplegia, which once made most heart surgeries possible, could one day be seen as a technique that has outlived its usefulness, although it’s still common today.
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