Biomedical Engineering Reference
In-Depth Information
surgery will impact on the number of bypass operations performed world-
wide. Similarly, miniaturized perfusion circuits, if they are proved to be
benefi cial, will certainly impact on the amount of biomaterials employed
for the construction of CPB circuits. Therefore, the growth potential from
the point of view of the amount of biomaterials employed in CPB does not
look encouraging from the perspective of the core activity, that of the extra-
corporeal circulatory support for routine cardiac operations, but there are
other emerging areas associated with routine CPB where there is potential
for development and growth.
6.7.1 Cardiologic interventions
The increased popularity of surgical coronary revascularization was accom-
panied by the improved performance of diagnostic coronary angiography.
As the diagnostic technique evolved to a safe and easily performed proce-
dure, engineering advances offered the possibility of improving coronary
blood fl ow capacity using catheter-based transluminal methods. The prolif-
eration of techniques for expanding a coronary lumen has produced a
more broadly encompassing nomenclature, namely, percutaneous coro-
nary intervention or percutaneous coronary revascularization. Two major
failings that hamper balloon angioplasty are abrupt closure and restenosis.
These failings stimulated the development of a myriad of devices with the
goal of reducing either the risk of the procedure, the risk of restenosis,
or both.
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Drug eluting stent (DES) placement reduces the risk of angiographic
restenosis and the need for repeat revascularization procedures for native
coronary artery lesions, small vessels, chronic total occlusion, and saphenous
vein grafts in patients with myocardial infarction and diabetes mellitus.
However, the impact of DESs on failure of long-term treatment and repeat
procedures does not translate to a reduced risk of procedure-related com-
plications. Because of the effect of the eluted drug or perhaps the polymer
itself, endothelialization is delayed after DES implantation, peristent infl am-
mation is prolonged, and local production of tissue factor may be enhanced.
After one month, thrombosis caused by DES placement is seen in approxi-
mately 0.3-0.7% of patients. Late thrombosis is associated with the treat-
ment of complex lesions, diabetes mellitus, renal failure, depressed left
ventricular ejection fraction, and withdrawal of dual antiplatelet therapy.
Randomized trials have compared coronary artery bypass grafting and
percutaneous coronary intervention. However, results of these trials in
select patients may not accurately refl ect current clinical practice using DES
and off-pump surgery. Rates of repeat revascularization were signifi cantly
higher for percutaneous interventions than for surgery, but mortality and
myocardial infarction were the same. There were no signifi cant differences
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