Advances in
Vascular Medicine
Improve Patient Outcomes
July / August 2004
Noninvasive and minimally invasive medical and surgical
care is a growing trend in all areas of medicine, particularly
vascular medicine. Research, including various clinical trials,
further demonstrates that noninvasive techniques can be used
for both diagnosis and treatment of patients with vascular
disease.
At Penn Vascular Services,
a unique group of specialists from interventional cardiology,
interventional radiology, neurology, neurosurgery, vascular
medicine and vascular surgery, provide state-of-the-art advances
in vascular medicine and surgery. These physicians also work
closely with rehabilitation medicine specialists and hematologists.
Comprehensive vascular services are available at the Hospital
of the University of
Pennsylvania, Pennsylvania Hospital, and Penn Presbyterian
Medical Center.
Noninvasive Vascular Medicine
“Our goal is to prevent disease progression by treating
cholesterol, diabetes, hypertension and any other risk factor
that affects patients with vascular disease,” says Emile
R. Mohler, III, MD, associate professor and director of
vascular medicine at the University of Pennsylvania Health
System.
Advancements in vascular imaging assist with diagnosis and
treatment and often help patients avoid catheterization. A
recent clinical trial focused on MS325, a new contrast agent
for Magnetic Resonance Imaging (MRI) that allows physicians
to view the arterial and venous system (including the very
small vessels of the feet) to determine if there is a blockage.
“The currently used imaging agent, gadolinium, only
circulates for four to five minutes. MS325 links to the protein
albumin in the bloodstream and circulates for up to an hour
providing the time and ability to obtain excellent pictures,”
says Dr. Mohler, principal investigator for the trial. MS325
is currently awaiting FDA approval for use in the peripheral
vascular system. Studies are also underway at Penn to evaluate
MRI imaging before and after either revascularization or
treatment
with cholesterol-lowering drugs.
The veins are an important element of circulation and a dysfunction
can be functionally debilitating. “When possible, we
treat blockages in the veins and degeneration of the valves
in the veins with minimally invasive surgical or interventional
approaches to more selectively reconstruct or remove the veins
that are problematic,” says Peter
R. McCombs, MD, associate professor of vascular surgery
and chair of the Department of Surgery at Pennsylvania Hospital.
Claudication and Deep Venous Thrombosis Research
The results of the recent PREVENT study are changing the
way patients with idiopathic deep venous thrombosis are
treated.
Penn participated in the study in which patients receiving
low-dose Coumadin indefinitely were compared to patients
given
the standard six months of therapy. “Patients who continued
the low-dose therapy had less recurrent blood clots in their
legs and less instance of a second pulmonary embolism compared
to participants who received the placebo. The results of this
study have dramatically changed the way we approach these
patients,” adds Dr. Mohler.
“Each year, a quarter million patients are diagnosed
with symptomatic deep venous thrombosis. We treat this condition
via thrombolysis, a minimally invasive technique that dissolves
a clot in the veins,” says Scott
Trerotola, MD, professor of radiology and surgery and
chief of vascular and interventional radiology at the Hospital
of the University of Pennsylvania. Penn will be participating
in the TOLEDO study, designed to further clarify the role
of thrombolysis in deep venous thrombosis. Thrombolysis also
pays an important role in thrombosis of arteries and arterial
bypass grafts.
At Penn, there are ongoing research protocols investigating
novel treatments for claudication and to improve blood flow,
including the recently approved drug Pletal™. Another
ongoing study is focused on prostacyclin, a natural molecule
produced by the arteries. Although prostacyclin has not been
found useful in relieving claudication, researchers are investigating
its ability to reduce pain and improve walking ability in
patients with critical limb ischemia. Penn vascular medicine
specialists are also investigating gene therapy for angiogenesis.
The newest protocol involves using adult stem cells to study
how they influence the growth of new blood vessels.
Minimally Invasive Stenting for Aortic Aneurysms
An aortic aneurysm is a leading cause of death in America
and a major indication for vascular intervention. Interventional
radiologists have a particular focus on angioplasty and
stenting
for peripheral vascular disease. Penn vascular surgeons are
performing clinical trials evaluating new stent grafts
for
the abdominal aortic aneurysm and several additional stent
grafts have been recently approved.
Vascular surgeons are also investigating the placement of
stents to treat aneurysms of the thoracic aorta which require
a small incision in the groin. “The impact of this trial
is even more compelling than the advancements involving abdominal
aortic aneurysms, because aneurysms in the thoracic aorta
are associated with greater morbidity and potential mortality
than those in the abdomen,” says Ron
M. Fairman, MD, associate professor and chief of vascular
surgery at the Hospital of the University of Pennsylvania.
Dr. Fairman is the national principal investigator for the
Talent ValorTM endovascular trial.
By using the thoracic stent-graft, vascular surgeons eliminate
most of the pain and discomfort associated with an operation
in the chest, and reduce many pulmonary and cardiac complications,
including the need to collapse a lung. Most importantly, this
procedure minimizes the risk of paraplegia, which can be anywhere
from five to 20 percent. Currently in Phase II, Dr. Fairman
expects this trial to demonstrate that using the thoracic
stent is a superior approach. “We have successfully
treated many patients who were too frail to undergo the open
procedure, including many who were on home oxygen,”
adds Dr. Fairman. “Any patient who has a thoracic aortal
aneurysm or thoracoabdominal aortic aneurysm may be eligible.”
Carotid Angioplasty and Stenting
In occlusive arterial disease, the arteries become blocked
due to the accumulation of atherosclerotic plaque inside the
arteries. This accumulation of plaque restricts blood flow
to critical areas of the body such as the brain, kidneys,
bowel and legs. Today, aggressive technology enables many
of these blockages to be opened via catheter-directed angioplasty
and stenting.
As part of another ongoing FDA clinical trial, the vascular
division at Penn has performed more than 100 carotid angioplasty
and stenting procedures. A risk of this approach is that
the
procedure itself can dislodge some of the plaque material
and cause an embolism to the brain. According to Dr. Fairman,
during the research protocol, vascular surgeons, interventional
neuroradiologists and neurologists utilize distal protection
devices to reduce this risk. In the short term the results
have been comparable to the results achieved during the traditional
carotid endarterectomy. Participants in the trial are not
candidates for the standard open approach.
Stroke and Subarachnoid Hemorrhage
Similarily, stroke is often related to atherosclerotic blockages
that develop in the carotid arteries. There are approximately
700,000 strokes per year in the United States, of which 150,000
are recurrent strokes. While working very closely with
neurosurgery
and neurology, Penn interventional neuroradiologists provide
endovascular treatment for cerebrovascular disease which
is
often best treated through the blood vessels. “We treat
a large group of patients who have intracranial aneurysms,
which often present with a subarachnoid hemorrhage, a devastating
form of stroke that affects approximately 30,000 patients
in the United States each year,” says Robert
W. Hurst, MD, professor and interventional neuroradiologist
in the Departments of Neurosurgery and Radiology at the
Hospital
of the University of Pennsylvania.
“In patients who suffer a subarachnoid hemorrhage,
it is critical to treat or close the aneurysm so a second
bleed in the brain is avoided. After we identify the aneurysm
location via angiogram, we utilize catheters to close the
aneurysms with platinum coils. This allows us to isolate the
aneurysm from the brain circulation and avoid an often fatal
second bleed,” explains Dr. Hurst. At times, brain aneurysms
are found incidentally on MRI and it is often better to treat
them before bleeding occurs.
“If you suspect your patient has carotid disease, it
is critical that he or she be evaluated by a neurologist.
This is the protocol that is followed when these patients
are enrolled in a clinical trial,” adds Dr. Hurst. “There
are a large number of people with carotid disease who do worse
with treatment, therefore an objective evaluation is crucial.”
Neurologists such as Scott
E. Kasner, MD, associate professor and director of the
Comprehensive Stroke Center at the Hospital of the University
of Pennsylvania, provide high-quality care to patients who
have had a stroke and evaluate a patient’s eligibility
for thrombolytic therapy. Research to advance stroke prevention,
treatment and the identification of high-risk conditions is
ongoing.
“We can’t emphasize enough the importance of
early acute therapy to reverse or limit the damage incurred
by stroke. In addition to administering tissue plasminogen
activator (t-PA) within three hours of the onset of stroke
symptoms, we are studying other clot-dissolving medications
for stroke that may offer a longer window of time than t-PA
and medications such as neuroprotectives that we believe might
prevent additional damage to the brain if administered early,”
states Dr. Kasner.
There are also a number of advanced treatment options for
stroke prevention. Dr. Kasner and his colleagues are participating
in a number of clinical trials that are investigating various
combinations of drugs to determine if they are more effective
in preventing stroke.
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