Biomedical Engineering Reference
In-Depth Information
valves with substantial enhancement of both survival and quality of life. Vascular
stents inserted with the help of catheters have provided new dimensions in the
treatment of coronary artery disease. Synthetic vascular grafts used to repair
weakened blood vessels, while bypass blockages have saved many from massive
bleeding or have resulted in enhanced blood fl ow to severely ischemic organs and
limbs. Devices to aid or replace the pumping function of the heart include intra-
aortic balloon pump, ventricular assist device, and total implantable artifi cial
heart. Pacemakers and automatic internal defi brillators are widely used to over-
ride or correct aberrant, life-threatening cardiac arrhythmias.
Most of these devices either alleviate the conditions for which they were used
or provide otherwise enhanced function. Nevertheless, device failure and/or other
tissue material interactions frequently cause clinically observable complications.
Some important mechanisms of tissue material interactions are similar across
device types, and several generic types of device related complications can occur
in recipients of nearly all cardiovascular implants [see Table 21.1]. These include
thromboembolic complications, infections, dysfunction owning to materials
degeneration and improper healing of the luminal surfaces etc. These problems
arise from the fact that even after six decades of research, no material has been
found to be truly blood compatible and many devices function with low or accept-
able risks of complications. The understanding of the complex mechanisms of
blood materials interactions is still far from complete.
TABLE 21.1. Major Failure Modes of Cardiovascular Devices
Heart valve
•
Thrombus/embolism
•
Anti coagulant related hemorrhage
•
Infection (Endocarditis)
•
Structural dysfunction
•
Non - structural dysfunction
Vascular graft
•
Thrombus/embolism
•
Graft infection
•
Perigraft seroma
•
False aneurysms
•
Intimal fi brous hyperplasia
•
Structural failure
Circulatory assist devices
•
Thrombus/embolism
•
Infection (endocarditis)
•
Extra luminal infection
•
Hemolysis
•
Structural dysfunction
Coronary stents
•
Thrombus/embolism
•
Restenosis
•
Neointimal proliferation
•
Aneurysm formation
•
Structural dysfunction
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