Stroke: Better prevention in cases of atrial
fibrillation, minimally invasive surgery for blood clots in the brain
Better
drugs for stroke prevention for patients with atrial fibrillation, good results
in the removal of blood clots in the brain using keyhole surgery: researchers
reported progress in the fight against strokes, the second-largest cause of
death at the Meeting of the European Neurological Society (ENS) in Prague.
There is highly promising new research into the problem of stroke-related brain
damage sometimes continuing to spread despite treatment.
Prague,
11 June 2012 – "Strokes are the second most important cause of death, and
one of the most relevant public health problems altogether, with 16 million new
cases worldwide every year, and 5.5 million deaths," Prof Dr Guido Stoll
(Department of Neurology at the University Hospital of Würzburg) said today at
the 22nd Meeting of the European Neurological Society (ENS). "It is all
the more pleasing to be able to report significant progress both in preventive
medication and in treatment of acute cases.” The ENS Meeting has brought
together more than 3,000 experts in Prague.
Among
the most important recent developments is the emergence of new, more convenient
drugs to prevent thromboses developing in cases of atrial fibrillation, which
can lead to embolisation by blocking cerebral blood vessels (ischemic stroke).
There are also improved therapeutic options to report: the possibility of
minimally invasive removal of blood clots in acute infarction. There are also
new insights into the mechanisms involved in "reperfusion injury":
the continued progress of brain damage despite the removal or dissolution of
the blood clot.
Atrial
fibrillation: more convenient thromboprophylaxis, equally effective with
reduced risk of complications
Atrial
fibrillation, which affects well over 4.5 million people across the EU, is a
factor in about 10% of all ischemic strokes. As a result of irregular
heartbeats blood clots (thrombi) form in the left atrium of the heart. If these
dissolve and flow towards the brain the result can be a stroke.
"Prophylaxis against this risk factor has now become easier and safer, and
works just as effectively," said Prof Stoll. The current standard therapy
for the prevention of thrombosis, the blood-thinning agent MarcumarR, had great
disadvantages, he said. One was of a serious risk of bleeding and great variations
in absorption, sometimes dependent on nutrition, both compromising the drug's
effectiveness in preventing strokes. This meant regular monitoring of blood
coagulation and frequent dose adjustments were required.
"Two
recently approved drugs for this condition have set new standards," said
Prof Stoll. These were the thrombosis inhibitor Dabigatran and the coagulation
factor Xa inhibitor Rivaroxaban. "These are just as effective in
preventing cerebral embolism, but carry a much lower risk of cerebral haemorrhage,
which is particularly feared. We can also be confident of reliable levels of
affect at fixed doses, so that patients are spared the arduous coagulation
monitoring checks. A third drug, Apixaban also inhibits coagulation factor Xa
and is already being used as prophylactic against thromboses in hip and knee
surgery. Given excellent results from studies, this drug too may be poised to
be approved as a prophylaxis against embolism in patients with atrial
fibrillation."
New
alternatives: minimally-invasive removal of thromboses
It has
long been known that thrombolysis medication to treat larger thromboses,
especially in the area of the carotid artery or in a main branch of the middle
cerebral artery, is insufficiently effective in dissolving them, and can result
in severe strokes. But there is new hope: mechanical removal of thromboses
(thrombectomy) using micro-catheters and minimally invasive high-tech medicine.
The ENS Congress discussed the latest data on thrombectomy, which guides a tiny
"basket" via a catheter up to the occluded brain vessel. There, the
thrombosis is "captured" and withdrawn. There had been very promising
experiences, inter alia with 200 patients in Bern, reported Prof Stoll.
"It makes special sense to combine the highly innovative thrombectomy
procedure with blood-thinning medication within the first few hours after a
stroke."
In
suitably equipped centres it could become standard in the future for patients
with occlusion of large vessels supplying the brain. Another advantage of thrombectomy
lay in the fact that this method could be safely applied in the case of
patients suffering strokes immediately after surgery or other intervention
where thrombolysis was out of the question due too high risk of bleeding.
Reperfusion
injury: first promising research
However,
in a numerically significant number of cases, infarction-related brain damage
continues despite successful lysis and/or removal of the thrombosis; the reason
is a mysterious process known as reperfusion injury. "Our many years of
effort to discover the reasons for this paradox are at last bearing
fruit," said Prof Stoll. "The endothelium, the inner lining of the
cerebral vessels, can be so altered by a temporary interruption of the blood
supply that platelets suddenly stick to the vessel wall, are activated, and
reduce, or actually stop, the blood-flow, even in smaller connected cerebral
vessels. We have found that in addition to platelets other inflammatory
processes are responsible, in particular the complement system. In animal
experiments we have now been able to show that a drug that inhibits the
so-called complement factor C1 (C1-Esterase) and has already been approved for
other indications, reduced the size of the infarct by half if administered early
enough after a stroke. There is still a long road ahead before this discovery
can be used clinically, but it is a very promising road which will, one day,
result in us mastering reperfusion injury”.
Strokes
– medicine's problem child. Rising death toll despite successes
Every
six seconds someone dies of a stroke. It is the second-most common cause of
death in the world, the third-most in developed countries, and the most common
cause of acquired disability in adults and for the need for care in old age.
"Although in recent years it has been possible to cut the relative
frequency (prevalence) of strokes in western industrialized countries, thanks
to rising life expectancy the number of cases continues to rise here too, more
than offsetting these advances," said Prof Stoll. "The annual number
of new cases is rising dramatically in economically emerging countries in Asia
like China, but also in Eastern Europe, where living standards are catching up.
As early as 2030, world-wide there will be 23 million new strokes every year,
with maximum growth in low-income countries; the absolute number of stroke
patients will rise to 62 million. An interesting new finding is that the causes
are the same everywhere, with no evidence of cultural specifics."
Large-scale
epidemiological studies identified 10 factors which together account for 90 per
cent of individual stroke risks. These are: excessively high blood pressure,
followed by smoking (passive smoking too!), diabetes, obesity, poor diet, lack
of exercise, atrial fibrillation, excessive alcohol consumption, unfavourable
blood fat values, and psycho-social factors such stress and depression. This
list shows that we can significantly influence our risk of strokes by changing
our lifestyles, regular check-ups, and regular medication," said Prof
Stoll.
Source:
ENS Abstract O 294: C1-inhibitor protects from ischemic stroke in rodents by
combined anti-inflammatory and anti-thrombotic mechanisms
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