Half a Heart to save your life !
Dateline: 07/11/99
The Berlin Heart Institute. 1994
Dr.Johannes Muller's patient had just died. The EEG monitor that traced brain function showed a
flat line. Despite the artificial heart pump surgeons had implanted to support his circulation.
But to Dr.Muller's surprise, when he turned off the heart pump (Novacor LVAD) the patient's HEART continued to beat. This was the same heart that, a few weeks back, had been judged too weak to support the circulation. That was why the assist device had to be implanted. Then what made it beat well now ?
The observation, and the question it triggered off, obsessed Dr.Muller's team, and spawned extensive research into the phenomenon now called "bridge to recovery". In its simplest sense, what this means is that the patient's heart is allowed to rest for some time. During this period the blood circulation is maintained by an artificial pump, called a Ventricular Assist Device (VAD). As the heart rests, it heals. Sometimes to an extent that it can return to near-normal function. At this time, the VAD could be removed !
What are Ventricular Assist Devices ?
Heart failure is a common condition. About 250,000 people die of congestive heart failure (CHF) every year. One in five patients (20%) with CHF will succumb to it within three months of diagnosis.
CHF may occur due to many different causes - coronary atherosclerosis, valve disease, cardiomyopathy and others. While most cases are treated with medicines, some do not respond to drugs. In these patients, a heart transplant was the only option.
But heart transplantation had some limitations. Suitable donor hearts are not easy to come by. Age, blood and tissue types, body size and other genetic factors determine whether or not a particular donor heart would be suitable for transplant.
But what to do in the meantime ?
Heart surgeons and researchers came up with a solution - a totally ARTIFICIAL heart. But the dream remained unfulfilled. Despite many experiments, it was not possible to design a totally artificial heart that would work effectively and improve quality of life in the long term. Also, the costs were prohibitive.
Puzzled, surgeons began to wonder whether it might be possible to support only the LEFT side of the heart. The left ventricle is the major power pump, distributing blood to all other parts of the body. If this could be supported - or replaced - using a mechanical device, heart failure might be averted. The result is today's LEFT VENTRICULAR ASSIST DEVICE (LVAD).
What are LVADs ?
In its simplest form, an LVAD is a mini-heart. Like a normal heart, it has an inflow tube through which blood enters it. It has a pumping chamber which propels this blood. And it has an outlet tube through which this blood then re-enters the body's circulation.
The different models of LVAD apply this principle in slightly varying methods. Design, size, composition and power supply are unique to each model, but the end result is the same - to support the left ventricle in its pumping function.
When are LVAD used ? Stay tuned for the next article.
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