Cardiac Resynchronization Therapy Offers New Hope
This article originally appeared in Pathways, a magazine
published for physicians and the community by UMass Memorial Medical
Center.
Cardiac resynchronization therapy (CRT), also called biventricular pacing,
offers new hope for appropriately selected patients with congestive heart
failure. In fact, Theo Meyer, MD, DPhil, director of the Heart Failure Wellness
Program at UMass Memorial, characterizes CRT as one of the major breakthroughs
in heart failure treatment over the past five years.
"CRT is a bright light in what has been a fairly dark environment," Dr. Meyer
said, referring to the treatment options for congestive heart failure which,
until recently, were limited to lifestyle changes, medications and, in some
cases, heart surgery. Patients with severe heart failure symptoms, however,
generally experienced modest, if any, relief from such measures.
"There have been improvements in medications," he acknowledged. "But CRT is
an added therapy that has made a significant impact on patients' quality of life
and outcomes. It definitely gives a boost to our armamentarium for treating
heart failure."
"CRT has the ability to improve symptoms, improve functional status and
reduce mortality," added Dennis Tighe, MD, associate director of noninvasive
cardiology and codirector of the CRT Clinic at UMass Memorial. "If a heart
failure patient with a low ejection fraction (less than 35 percent) is still not
doing well after an appropriate medical treatment program, CRT should certainly
be considered."
In an estimated 30 to 40 percent of patients with heart failure, an
abnormality called an intraventricular conduction delay or bundle branch block
causes the right and left ventricles to beat dyssynchronously. This further
reduces the efficiency of the pumping action of an already weakened heart
muscle.
CRT employs a biventricular pacemaker in an attempt to improve synchrony of
the action of the right and left ventricles, toward restoring their normal
coordinated pumping action by overcoming the delay in electrical conduction
caused by bundle branch block. While a regular pacemaker has two leads - one in
the right atrium and one in the right ventricle - the CRT device has a third
lead that is positioned in a vein on the surface of the left ventricle. This
enables the CRT device to simultaneously stimulate the left and right
ventricles, and restore a synchronous squeezing pattern. This biventricular
pacing reduces the conduction delay, resulting in a more coordinated and
effective heart beat. Like a regular pacemaker, the CRT device is implanted
under the skin in the upper chest.
"We continue to be amazed at the results from CRT," said Dr. Tighe, a
specialist in cardiac electrophysiology at UMass Memorial. This treatment has
been available at UMass Memorial since 2001. The Medical Center currently
implants more than 100 CRT devices annually, he continued.
"Patients with heart failure are seeing dramatic improvements in their
quality of life," he added, an observation that bears out earlier studies in
which CRT demonstrated the ability to improve exercise capacity and functional
status, allowing patients who were previously limited in their ability to
perform everyday tasks to resume a more normal daily routine.
CRT also has shown to reduce mortality. The recent CARE-HF (CArdiac
REsynchronization in Heart Failure) Study was conducted to assess the effect on
morbidity and mortality of adding CRT to optimized pharmacological therapy in
patients with moderate to severe heart failure due to left ventricular systolic
dysfunction complicated by cardiac dyssynchrony. It found that CRT administered
in combination with optimal medical therapy saved lives and reduced
hospitalizations. Further, CRT was found to improve both the anatomy and
function of the heart.
Another recent study - the Comparison of Medical Therapy, Pacing and
Defibrillation in Chronic Heart Failure trial - revealed that both CRT alone and
CRT plus an implantable cardioverter defibrillator (ICD) significantly reduced
combined all-cause mortality and hospitalization rates in patients with moderate
to severe heart failure.
"The CRT device is often coupled with an implantable cardioverter
defibrillator because this is the patient population most at risk for sudden
cardiac death," Dr. Tighe noted. In these patients, the ICD is incorporated with
a CRT pacemaker, creating a CRTD.
While CRT holds promise for many heart failure patients, not all of them are
candidates for implantation of the device, cautioned Drs. Meyer and Tighe.
"The ideal candidate falls into Class III and/or IV of the New York Heart
Association's classification for heart failure, and has an ejection fraction of
less than 35 percent," Dr. Tighe explained. In these stages, patients exhibit
evidence of cardiac dysfunction with symptoms and exhibit signs of heart failure
despite maximal therapy. The procedure is not recommended for patients who are
mildly symptomatic.
"Our clinic at UMass Memorial can help to identify appropriate patients for
CRT," he continued. We are on the forefront of advanced classification of
dyssynchrony by an echocardiographic approach, often the first step in
identifying patients who may respond well to this therapy." We also perform a
full assessment including administering and scoring the Minnesota Living with
Heart Failure® Questionnaire, measuring biomedical markers and determining other
baseline measurements. Our evaluation is very comprehensive and helps us decide
the best type of therapy for heart failure patients."
"More patients than you might think are eligible for CRT and its benefits,"
added Dr. Meyer, "which underscores the importance of a thorough evaluation."
Nor does cardiac resynchronization therapy end with implantation of the
device, Dr. Tighe noted. "Programming the CRT device - setting it at optimal
intervals - is critical in order the get the most out of this therapy," he
explained. "So regular follow-up is an essential part of treatment.
"Despite its benefits, however, there is still a lack of familiarity with
CRT," he continued. "And some people think that this treatment is still
experimental. It's anything but! CRT patients who once could barely walk to the
bathroom can now exercise on a regular basis. This therapy can take patients off
the heart transplant list. And it can keep them out of the hospital. I can't
stress enough how dramatically CRT can improve a patient's quality of life and
give someone a second lease on life."