The human heart

The cockroach has survived every civilization known to man.Evolution has favored cockroaches above human beings, at least when it comes to the functioning of the heart. A cockroach’s heart will continue to beat even when one of its chambers has failed; in similar circumstances, a man will die. Thus the lowly cockroach is at the heart of successful research by scientists who are developing an artificial heart. Using the roach’s heart as a model, the new prototype promises to be much cheaper and more reliable for implantation in humans than models currently in use.

The key to the new heart involves the insect’s unique breathing system. The cockroach is blessed with thirteen blood-pumping chambers while humans only have four. When a chamber fails in a human heart, it usually leads to a fatal cardiac arrest but in a cockroach with its 13 chambers,linked like a string of sausages, it can keep pumping even if one breaks down!A cockroach’s heart is a tube that runs the length of its body. As each chamber contracts, the blood within is pumped to a higher pressure. Each successive chamber increases the pressure. A human heart, by contrast, has four chambers. Two of these pump blood to the lungs, where it picks up oxygen, then the other two pump this oxygenated blood throughout the body. One of these four chambers—the left ventricle—contracts most strongly to pressurize the blood.

The artificial hearts developed so far have mostly mimicked human ones. The first devices, developed in the 1950s and 1960s, were large machines placed on trolleys next to the patient and attached by tubes. Modern artificial hearts are less cumbersome, but they are still rather unwieldy because they use compressed air to pump the blood and are powered by heavy batteries. They are used temporarily, usually for a few days or weeks, until a real heart is available for transplant.

Instead of trying to mimic the action of the left ventricle, Dr Guha’s design uses a multi-step approach borrowed from the cockroach. His device, made from plastic and titanium, is the same size as a human heart but with five chambers arranged like the layers of an onion. Each chamber acts in succession to increase the pressure of the blood. The contraction of each chamber is controlled by a motor driven by bulky batteries. "Our model is based on the cockroach system, where we build up the pressure in smaller steps. So even if one chamber fails, a person can still live. This model does not stress the other components (pumping elements) and there is less stress on the blood cells”, says team leader Professor Sujoy Guha.The artificial heart, named TAH ( total artificial heart) is being tested on goats, with human trials scheduled for next year. If these are successful, the device could be on the market in three to five years.

The multi-step approach makes this artificial heart much cheaper to build than those that use compressed air to pump the blood. Dr Guha says it would cost $2,000-2,500 about thirty times cheaper than the present models.

I read these reports with great pleasure for a number of reasons. First the research was led by an Indian. Secondly it was done in India. And even more importantly the work was done at the Indian Institute of Technology at Kharagpur, my alma mater. I graduated from this IIT in 1961 and visited the institute only last year- as the institute had decided to honor me as a Distinguished Alumnus. But the most inspiring news was that the leader of the team was Sujoy Guha who graduated with me in 1961! Wow indeed.

On a more personal note, I spent the better part of 2007 in Johns Hopkins hospital in Baltimore being evaluated for a heart transplant.I was not approved for a human heart transplant, but perhaps the cockroach inspired TAH of Professor Guha would be the replacement! To have your heart redesigned by your own classmate- how cool is that!