Dynamic Cardiomyoplasty - Support for a failing heart
Dateline: 11/02/97
End stage heart failure is a serious condition, and just a few years ago there was no medical cure.
Today, with the growth of technology and adoption of innovative approaches by surgeons and
cardiologists, there is light at the end of the tunnel. In an earlier article, I had described Randas
Batista's novel operation for heart failure. In this one, the spotlight is turned onto Dynamic
Cardiomyoplasty which is another revolutionary approach to the solution of this vexing problem.
What is Dynamic Cardiomyoplasty ?
Cardiomyoplasty literally means "repair of heart muscle" ("cardio" = heart, "myo" = muscle, "plasty
= repair). In dynamic cardiomyoplasty (dCMP), muscle from the chest wall is wrapped around the
heart, and it assists the heart in its contraction.
Principle underlying dCMP
Heart failure is the end result of many different disease processes. In most cases, however, the
heart muscle is stretched beyond normal limits and is weakened. In dCMP, a muscle from the chest
wall called Latissimus Dorsi (LD) is detached, and rotated inwards and wrapped around the heart.
As the LD muscle contracts, it squeezes the heart and helps it in the pumping of blood. Also, by
restraining the heart, it prevents excessive dilatation, and keeps the heart muscle length within
normal limits. In both these ways, dCMP helps to improve heart contraction and relieve failure.
Steps involved in dCMP
The essential difference between heart muscle and all others is that heart muscle is
- involuntary - its contraction is not under our control
- automatic - the heart keeps contracting automatically
- non-fatigued - it keeps working minute after minute, hour after hour, day after day, and year after year without becoming tired !
If skeletal muscle like LD from the chest wall is to be used to assist the heart, it needs to be
"trained" first to work like heart muscle.
Training Latissimus Dorsi muscle
Once a patient is selected for dCMP, the first step is to "train" the LD muscle. LD is a powerful
bulky muscle that moves the arm. At the first operation, this muscle is detached from its attachment
leaving only a narrow pedicle in which the artery and nerve supply to the muscle is preserved. An
electrode (piece of metal conducting electricity) is implanted into it. This electrode is connected to a
device called an "impulse generator". This device generates a weak electric shock at regular
intervals, that makes the muscle twitch repeatedly. After some weeks of this stimulation, the LD
becomes almost automatic and resistant to fatigue. It can then work almost as efficiently as heart
muscle, and for long periods of time.
The Cardiomyoplasty operation
Once the LD is adequately trained, the next step is to wrap it around the heart. The operation is
done through an incision in the left side of the chest - a lateral thoracotomy. The protective covering
of the heart - the pericardium - is opened, and the LD muscle turned in and wrapped around the
heart. It is held in position by a few stitches. The impulse generator is implanted in a pocket created
under the skin. It is attached using electrodes to the heart muscle too. This is to synchronize
contraction of the heart and the LD muscle so that the combined effect of their action is used to
pump blood.
How good an operation is dCMP ?
Opinion is divided about the usefulness of this operation. Long term survival and outcome data are
awaited, but intermediate term results are encouraging. Quality of life in survivors is certainly
improved. While many return to ambulant lifestyles, there are very few who are as active as they
were before developing heart failure. Modifications of the technique are still being made to train the
LD better, to shorten the period of training, and make the operation suitable to a wider range of
patients.
Comparison of dCMP with assist devices and transplantation
As an alternative for end stage heart failure, dCMP is an option along with left ventricular assist
devices (LVAD) and heart transplantation. LVADs are becoming better and more efficient, but
involve use of blood thinning medication, and are expensive. While newer models allow ambulant
lifestyle using a back-pack battery, most patients need to be tethered to a hospital for maintenance.
In contrast, a heart transplant recipient needs to be on life-long medication to prevent rejection, and
is always at risk of late (chronic) rejection of the transplanted heart. An added attraction of dCMP
is that it does not exclude the use of these options at a later stage in case of failed dCMP.
In succeeding articles, I will discuss the other options for heart failure as well. If you have any
questions or suggestions, please write to me.
