C h a p t e r 1 9
Disorders of Cardiac Function
453
arrhythmias, limited infarct size, improved infarct heal-
ing, and myocardial remodeling.
12
These agents interact
with plasminogen to generate plasmin, which lyses fibrin
clots and digests clotting factors V and VIII, prothrom-
bin, and fibrinogen (see Chapter 12). The person must
be at low risk for complications caused by bleeding,
with no intracranial hemorrhage or significant trauma
within the last 3 months.
14
Percutaneous coronary intervention
(PCI) is indicated
as an early invasive procedure for patients with unstable
angina/NSTEMI.
19
Percutaneous coronary intervention
includes percutaneous transluminal coronary angioplasty
(PTCA) and stent implantation.
Balloon PTCA
involves
dilating the coronary artery with an inflatable balloon
positioned at the narrowing of stenotic atherosclerotic
plaque within the vessel (Fig. 19-7). Similar to an angio-
gram, the procedure is performed under local anesthesia
in the cardiac catheterization laboratory. Balloon PTCA
is almost exclusively used in conjunction with coronary
stenting. The addition of
coronary stenting
significantly
improved short- and long-term outcomes for patient with
ACS compared with PTCA alone but patients remain at
risk for restenosis and thrombosis following the procedure.
Persons undergoing stent procedures must be treated with
antiplatelet and anticoagulant drugs to prevent throm-
bosis and restenosis. Drug-eluting stents that provide
sustained delivery of an antiproliferative pharmacologic
agent may be used to decrease the risk of thrombosis.
19
Coronary artery bypass grafting
(CABG) may be the
treatment of choice for people with significant CAD
who do not respond to medical treatment and who are
not suitable candidates for PCI. It may also be indi-
cated as an emergent treatment for STEMI, in which
case the surgery should be done within 4 to 6 hours
of symptom onset if possible. The procedure involves
revascularization of the affected myocardium by attach-
ing a saphenous vein graft between the aorta and the
affected coronary artery distal to the site of occlusion,
or by using the internal mammary artery to revascular-
ize the left anterior descending artery or its branches
(Fig. 19-8). This procedure often involves one to five
distal anastomoses. Using emergent or urgent CABG as
a reperfusion strategy is indicated in situations such as
failed PCI with persistent pain or hemodynamic insta-
bility, or for patients who are not candidates for PCI or
fibrinolytic therapy.
Myocardial Postinfarction Recovery Period.
After a
MI, there usually are three zones of tissue damage: a
zone of myocardial tissue that becomes necrotic because
of an absolute lack of blood flow; a surrounding zone of
injured or hypoxic cells, some of which will recover; and
an outer zone in which cells are ischemic and can be sal-
vaged if blood flow can be reestablished. The boundaries
of these zones may change with respect to the timeliness
of treatment to successfully reestablish blood flow. If
blood flow can be restored within 20 to 40 minutes, loss
of cell viability is minimized.
6
The process of ischemic
necrosis usually begins in the subendocardial area of the
A
B
C
D
FIGURE 19-7.
Balloon-expandable stent insertion.
(A)
Insertion
of a guide catheter with a collapsed balloon-expandable
stent mounted over a guide wire into a coronary artery.
(B)
Advancement of guide wire across the coronary lesion.
(C)
Positioning of the balloon-expandable stent across the
lesion.
(D)
Balloon inflation with deployment of the stent. Once
the stent is expanded, the balloon system is removed.
Vein
graft
Left
subclavian
artery
Internal
mammary
artery
Anterior
descending
branch of the
left coronary
artery
FIGURE 19-8.
Coronary artery revascularization. (Top)
Saphenous vein bypass graft.The vein segment is sutured to
the ascending aorta and the right coronary artery at a point
distal to the occluding lesion. (Bottom) Mammary artery
bypass graft.The mammary artery is anastomosed to the
descending branch of the left coronary artery, bypassing the
obstructing lesion.
