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Cardiac Resynchronisation Therapy
Guidant has invested more than 10 years of scientific and clinical research to show
that heart failure patients can benefit from restoring the co-ordinated pump function of
the heart through the implant of a resynchronisation device. Diverse studies have
shown that in most patients the diseased heart no longer pumps blood in an optimal
way for heart failure that resynchronises the contraction of the two ventricles:
resynchronisation therapy.
Nearly one-third to one-half of heart failure patients have out-of-sync hearts. In these
patients, the left and right sides of the heart contract slightly out of sequence, so blood
no longer circulates effectively. To improve this condition, patients can be treated
with resynchronisation devises, which use electric pulses to stimulate the four
chambers of the heart to work in sync.
The therapy consists of a stimulation device (comparable to a pacemaker) implanted
in the sub-pectoral region. The device delivers electrical impulses to the right and left
ventricles to enable the two chambers to contract in a co-ordinated manner. This
process is called biventricular stimulation. As a result of this therapy, the pumping
efficiency of the heart increases, as well as the exercise tolerance of the patient.
Guidant resynchronisation devices are implanted into the heart and act mechanically
in the chest. They have three wires called “leads” that run through the veins to the
interior wall of the right atrium, the interior wall of the right ventricle and the outside
wall of the left ventricle. The wires monitor the heart whenever the chambers start
beating unevenly and use electrical impulses to resynchronise the contractions.
In general, although resynchronisation devices can effectively treat bradycardia or
tachycardia, they do not prevent sudden cardiac death, or the sudden, abrupt loss of
heart function (i.e. cardiac arrest), unless they include an ICD backup.
An ICD, or implantable cardioverter-defibrillator, is a device designed to administer
an electric shock in instances of ventricular fibrillation or ventricular tachycardia -and restore a normal heartbeat. These devices are also used to treat sudden cardiac
death. The power source is implanted in a pouch beneath the skin of the chest or
abdomen and is connected to patches placed on the heart.
Underlying heart disease is almost always found in victims of sudden cardiac death.
Typically in adults this takes the form of artherosclerotic heart disease. Two or more
major coronary arteries are narrowed in 90 percent of cases; scarring from a prior
heart attack is found in two-thirds of victims. Therefore, it is believed that
predisposing factors for SCD are similar to those for atherosclerotic heart disease and
include cigarette smoking and high blood pressure.
People with scarred or enlarged hearts for any reason are prone to develop lifethreatening ventricular arrhythmias, which can lead to SCD. Additionally, the first
six months after a heart attack is a particularly high-risk period for SCD in patients
who also have atherosclerotic heart disease. A thickened heart muscle from any cause
(typically high blood pressure or valvular heart disease) is also an important
predisposing factor for SCD.
Survivors of unexpected cardiac arrest due to ventricular tachycardia or fibrillation
are at risk for recurrent arrest. This is especially true if they have underlying heart
disease, or heart failure. Patients with atherosclerotic heart disease are at risk for
recurrent cardiac arrests when the first, aborted sudden death episode occurs in the
absence of a new heart attack, because this implies a persistent underlying tendency
toward electrical instability.
Survivors of aborted SCD must have all causes corrected to prevent future episodes.
Possible tests and treatments to prevent future SCD are varied and may include one or
a combination of the following:
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Cardiac catheterisation, to show the heart and coronary blood vessels
Electrophysiologic tests
Coronary artery bypass surgery
Balloon angioplasty, or PTCA
Anti-arrhythmic medicines
Implantable cardioverter or defibrillator
Implantable pacemaker
Heart transplant
Implantable resynchronisation device an ICD backup.
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By the end of 1999, Guidant launched the CONTAK SYSTEM in Europe, which
stimulates the right and left ventricle in a synchronised manner. This product includes
an ICD backup to avoid and prevent sudden cardiac death (SCD). Research
completed in 2001, indicated that a post-market study of 1000 European heart failure
patients using Guidant's heart failure technology – including the CONTAK CD™
device, the CONTAK TR™ device and the EASYTRAK™ coronary venous lead
system – had marked improvement in their heart failure condition.
In July 2001 Guidant followed through with the next generation CRT device, the
RENEWAL. In addition to delivering increase flexibility in therapy delivery, this
system monitors heart rate variability, a tool designed to track and measure the status
of heart failure patients. The device also uses data from an accelerometer sensor to
track trends in each patient’s activity level. This capability addresses physicians’
desire to monitor activity levels as an indication of their patients’ ability to perform
activities of daily living. Additionally, the RENEWAL features reduced size and a
patient-friendly physiologic shape for ease of implant and increased patient comfort.
Combining resynchronisation therapies with a defibrillator capacity could improve the
functionality in and longevity of patients by preventing sudden cardiac death.
However, because they do not treat other symptoms of heart failure, there is a benefit
in combining this therapy with a resynchronisation device, which can effectively treat
bradycardia and tachycardia.
Current published studies on electrical-stimulation therapy have explored treating
heart failure patients through the use of resynchronisation therapy. These relatively
small clinical studies have primarily been uncontrolled and were designed to
demonstrate improvement in systolic performance of the left ventricle, an increase in
functional capacity or improvement in quality of life.
The first steps in the resynchronisation therapy for heart failure were taken by
Guidant in 1990. Ten years of intensive research have enabled Guidant to offer
innovative and efficient therapies to Heart Failure patients.
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