Thursday, February 11, 2016

Unbreak My Heart: A Short History Of The Defibrillator and CPR

“Hearts cannot be broken, they're small squishy things
They don't break like glass but they bruise easily” – The Judybats

While hearts can’t be broken, their rhythmic beating can go awry – a condition we call arrhythmia. Many people don’t think of the heart as a muscle, but that’s what it is - a muscle that pumps blood around the body through a series of regular contractions. When the ventricles contract, oxygenated blood gets pumped out into circulation; when they relax, they fill back up with blood. Disruption of this routine delays delivery of blood to tissues and organs, including the brain.

Ventricular fibrillation is caused when a heart disorder leads to a problem with the electrical impulses running the cardiac muscles, which makes them quiver instead of contracting. A defibrillator basically sends an electric shock through the heart, stopping it in hopes that it starts back up with its normal rhythm restored. A remarkable feat that has saved tens of millions of lives, but how did we learn to do this?

Ventricular fibrillation usually occurs as a consequence of previous cardiac damage, such as a heart attack. But what about the pain that we feel when someone “breaks” our heart? Believe it or not, stress-induced cardiomyopathy, also known as “broken heart syndrome” is a real thing!
For centuries, it was believed that muscles used air or liquid to inflate. In the 1780s, Luigi Galvani “popped” this so-called “balloonist” theory by applying a newly discovered power called electricity to the leg muscles of a dead frog. In his experiments, Galvani stimulated limb muscles with heat, lancets, or chemical irritants…but only an electrified rod prompted those muscles to contract. This was a profound discovery that opened up a whole new field in medicine that studies the role of electricity in physiology (electrophysiology). And it raised an exciting question:  can electricity be used to reanimate life?   

Long ago, people used to believe muscles expanded and contracted because of air or fluid inside them. This was referred to as the “balloonist” theory.
Galvani’s nephew, Giovanni Aldini, set out to address that haunting question by performing what scientists were calling “Galvanic experiments”. In 1803, he freaked out a lot of people with a public demonstration involving the corpse of a freshly executed criminal and a pair of conducting rods hooked up to a battery. Aldini proceeded to touch the corpse at his mouth, ear, and, of course, his rectum. An eyewitness account documented the creepy results: “On the first application of the process to the face, the jaws of the deceased criminal began to quiver, and the adjoining muscles were horribly contorted, and one eye was actually opened. In the subsequent part of the process the right hand was raised and clenched, and the legs and thighs were set in motion.” (from the Newgate Calendar, January 18, 1803).

You might be wondering if Galvani or Aldini’s experiments inspired Mary Shelley’s 1818 classic, Frankenstein: or, The Modern Prometheus. While Shelley was aware of their work, electricity was not mentioned in her novel as the means by which Dr. Frankenstein’s creature was brought to life…that specific idea was incorporated later on when the story was made into a movie.
As dramatic as the “shocking” experiment was, the lesson was that electricity would not reanimate a corpse. So it wasn’t until 1930 that this sort of work was resurrected with simpler objectives:  using electric currents to kickstart a heart. Enter William Kouwenhoven, who invented the heart defibrillator, a device that essentially “restarts” the cardiac engine*. His experiments did not get off to a promising start. In 1928, high voltage shocks from electrodes placed on the head and one limb of a rat only resulted in a dead rat. But by 1933, he was able to restore normal heartbeats to dogs. However, this required direct contact with the dog’s heart muscle to work. This method of “open chest heart defibrillation” was practiced on patients until 1957, when Kouwenhoven built a device capable of delivering the electrical pulses from outside the body.

One of the first defibrillators by Kouwenhoven compared to what they look like today.
Kouwenhoven’s defibrillation studies also led to the development of cardiopulmonary resuscitation (CPR) as a critical life-saving technique. One fine Saturday – because all good scientists work through the weekends – a graduate student named Guy Knickerbocker noted a brief rise in blood pressure when he pressed those heavy copper defibrillator paddles onto the dog’s chest. This gave rise to the idea that by forcefully pressing on the chest, one could help circulate blood through the body until the heart started beating again.

*Kouwenhoven’s research stemmed from earlier findings, most notably those made by Jean-Louis Prevost and Frederic Batelli. In 1899, they observed that electrical shocks could induce ventricular fibrillation in dogs, but even larger shocks could restart their hearts.

Contributed by:  Bill Sullivan

Bresadola, M. (1998). Medicine and science in the life of Luigi Galvani (1737–1798) Brain Research Bulletin, 46 (5), 367-380 DOI: 10.1016/S0361-9230(98)00023-9

1 comment:

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