Three implants to mend heart: Stent, Valve and a Defibrillator

Three implants for the heart have changed the outcomes of heart disease – namely stents, artificial valves, and an implantable defibrillator. Stents can now open a tiny blood vessel supplying the heart muscles (coronaries). Artificial valves can replace a damaged native valve inside the heart and can now also be inserted without opening up the chest. Implantable defibrillators can detect life-threatening a change in electric current in heart (arrhythmia) and automatically correct it too. This blog is a brief on these three.

Stents inside a vessel

While the term “stent” came in 1856 from Charles Thomas Stent, a British dentist who developed a material for dental impressions, intra-vascular stents came much later. In 1969, An American radiologist Charles Dotter performed experiments to insert metal coils into dog arteries. This was first use of the word stent in medical literature.

First coronary stent in a human came up two decades later in 1986. This implant was done by Jacques Puel and Ulrich Sigwart in Toulouse, France. Their 1987 report about ten initial stents changed the world of cardiology. Over the next decade the material used for the stents improved, and clinical trials established their utility. Today we mostly use drug eluting stents (DES). These stents are impregnated with a medicine, that prevents formation of clots within a stent, and prolongs its life. These came only in 2002. Today millions of stents are implanted in coronary vessels all over the world, about 2 million in USA and half a million in India.

Artificial valves

The history of the artificial heart valve began in 1950s. It was Dr Charles Hufnagel who came with a tube-ball valve. A decade later in 1960s Starr and Edwards cam with a cage and ball valve. The commonest artificial valve we use today – the bi-leaflet one came two decades later in 1980s. In addition to these artificial valves, we also started developing tissue valves in the 1970s. All these valves require a surgery to open up the chest and the heart to insert a valve.

In 1989 the first percutaneous heart valve (PHV) was implanted in an animal. The next revolution in artificial valves came in the year 2000 when Alain Cribier, a French cardiologist successfully implanted a valve through a blood vessel, into an animal, using a system of a balloon-expandable stent and biological leaflets. Two years later, they would do the first human procedure. It became possible to hav a new heart valve, without opening up the chest. Alain Cribier continued to popularize the percutaneous technique (known as TAVI), till he passed away in the year 2024.

Implantable defibrillators

In the early 1970s, Dr. Michel Mirowski, and others, developed the concept of an ICD to save patients from sudden death. His family had to flee from Poland during the holocaust. He trained in France, and later practiced medicine in Israel, before moving to United States in 1966. His idea of a miniaturized defibrillator had few takers.

For the next 12 years, Mirowski and his colleagues developed their device and miniaturized it to be implanted in patients. On February 4, 1980, the first patient received a defibrillator in John Hopkins. Subsequent clinical trials and significant technological advancements in size, battery life, and detection algorithms led to widespread acceptance and expanded indications for ICDs, ultimately transforming it into a crucial therapy for preventing sudden cardiac death. This advance led to development of subcutaneously implanted defibrillators, and cardiac re-synchronized therapy.