How does
"clot buster" treatment compare with emergency
angioplasty and coronary stenting? This
is an excellent question for which there is no easy
answer. Let us first look at intravenous thrombolytic
(clot buster) treatment which became one of the
more important advances in the treatment of heart
attacks since its introduction. It offers the following
advantages (Reference: ACC/AHA Guidelines for Patients
with Acute Myocardial Infarction: Executive Summary,
Circulation, Nov 1, 1996):
In comparison with standard medical
treatment, thrombolytic therapy reduces the 35-day
mortality (death rate) by 21%
This corresponds to an overall reduction of 21
deaths per 1000 patients treated in this manner.
Time is of essence with
the use of thrombolytic treatment. Higher benefits
are achieved when it is given within 6 hours of
the onset of heart attack symptoms. Best results
are observed within two to three hours but continues
to be beneficial even if started within 12 hours.
35 per 1000 lives are saved when
it is used within the first hour of symptoms.
This drops to 16 lives saved per thousand if treatment
is delayed for 7 to 12 hours.
Thrombolytic therapy benefits
the patient regardless of age, sex or presence
of risk factors for coronary artery disease.
Disadvantages include a small
risk of a stroke (2%) with a little over half
of them (1.1%) being due to bleeding. To place
this in the proper perspective, the risk of a
stroke due to thrombolytic treatment is far outweighed
by the number of lives that are saved
Next, let us examine the advantages
of angioplasty performed as a primary procedure
in the treatment of a heart attack. According to
the recommendations of the American College of Cardiology
and the American Heart Association Guidelines (above),
primary angioplasty may be performed as an alert
native to thrombolytic therapy in the following
circumstances:
It can be accomplished in a timely
manner by skilled and experienced staff.
There is prompt access to coronary
bypass graft surgery.
Advantages
of Primary Angioplasty:
About half the patients treated
with thrombolytic therapy continue to have a significant
blockage (since the treatment breaks up blood
clots but does nothing for the underlying blockage)
and reduced blood flow in the affected artery.
In comparison, blood flow is brisk and a mild
or no blockage is left behind in over 90% of cases
treated with primary angioplasty with or without
stenting.
The mortality or death rate with
primary angioplasty is 60% lower (Reference: JAMA
278:2093, 1997) than that achieved with thrombolytic
therapy (4.4% compared to 6.5%).
The risk of stroke is reduced
by more than 50%, compared to thrombolytic therapy.
The probability of having an open
artery at 6 months with thrombolytic therapy alone
is 59%. The odds improve to 87-91% at 3-6 months
with primary angioplasty (References: NEJM: 328,
1993 and Circulation 90:156, 1994).
In studies where patients were
randomized to thrombolytic therapy versus primary
angioplasty, those treated with thrombolytic therapy
required subsequent PTCA or bypass surgery in
30% of cases. In contrast, only 5% of patients
treated with primary angioplasty required a subsequent
procedure or surgery during the 3-6 month follow-up
(Reference: Circulation 10[Suppl A] 12A, 1998).
With Primary Stenting in heart
attacks, the success rate of the procedure is
increased to >95% with less than 1% (0.8%)
mortality (death rate) within the hospitalization
period (Reference: Cathet Cardiovasc Diag 44,
118, 1998).
The restenosis rate (chance of
blockage returning at same site) is around 25%
at 7 months in cases of primary stenting for heart
attacks (Reference: J Am Coll Cardiol 31, 23,
1998).
If Primary Angioplasty
and Stenting is so good why is it not used in every
patient with a heart attack? Excellent
question! Since only 18% of hospitals are equipped
to perform emergency angioplasty and stenting in
patients with heart attacks, this form of treatment
is not available in the remaining 82% of hospitals
that admit patient's with chest pain. Remember that
time is of essence in getting rid of obstructing
blood clots and salvaging heart muscle. In most
cases, the patient is far better off in receiving
a "clot buster" medication in the emergency
room if access to a hospital with a cardiac cath
lab is not readily available.
The x-ray video on the left shows
a normal left ventricle as it fills and empties.
The study was obtained during cardiac catheterization.
Note how the top (anterior wall) and bottom (inferior
wall) move towards each other as the heart pumps
blood to the body.
The video
on the right shows the same left ventricle after
a heart attack involving total blockage of the right
coronary artery (RCA). Compared to the video above,
please note that the inferior (bottom) wall, which
is supplied by the RCA, is now barely moving.
