Biomedical Engineering Reference
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restrictive, right ventricular, and nonclassifiable cardiomyopathies with distinct
hemodynamic properties. Furthermore, the new WHO/WHF definition also com-
prises inflammatory cardiomyopathy, defined as myocarditis in association with
cardiac dysfunction. Idiopathic, autoimmune, and infectious forms of inflammatory
cardiomyopathy were recognized. Viral cardiomyopathy is defined as viral persistence
in a dilated heart. In recent years, there have been breakthroughs in understanding
the molecular and genetic mechanisms involved in this group of conditions, enabling
improvement of diagnostic strategies and introduction of new therapies. Ongoing
evaluation of antiviral, immunoglobulin, removal of antibodies by immunoadsorp-
tion, anticytokine and gene therapy, as well as the mechanical support devices may
provide new treatment options.
Cardiac Arrhythmias
The normal cardiac rhythm originates in the sinoatrial (SA) node, a patch of cells
called the pacemaker, which generates cardiac rhythms for coordinated contrac-
tions and blood pumping. Accelerated transmission of electrical impulses through
the atrioventricular (AV) node, a critical regulator of heart rate, is largely respon-
sible for the rapid heart rate during many atrial arrhythmias, such as atrial fibrilla-
tion, atrial flutter, and paroxysmal atrial tachycardias. Prompt slowing of AV nodal
conduction is often the immediate goal of treatment to slow the abnormally rapid
heart rate. Atrial arrhythmias are potentially life-threatening situations with such
consequences as stroke, heart attack, and low blood pressure, and require immedi-
ate treatment. Caffeine, tobacco and stress may trigger an increase in the speed of
conduction through the AV node resulting in atrial arrhythmias.
Cardiac arrhythmias are a leading cause of morbidity in the Western hemisphere.
The risk of developing malignant ventricular tachyarrhythmias is associated with
the extent of myocardial injury and is believed to be the primary cause of approxi-
mately 50% of all cardiovascular deaths. Bradycardia and heart block, which can
result from the normal aging process, further add to the morbidity associated with
cardiac arrhythmias and results in the permanent implantation of over 160,000
pacemakers annually in the USA.
Conventional medical therapy is predominantly palliative treatment and com-
monly fails to impede and prevent the morbidity and mortality associated with
cardiac arrhythmias. Radiofrequency catheter ablation of ischemic ventricular
tachycardia is considered adjuvant therapy rather than curative. The implantation of
defibrillators and pacemakers, while generally effective, do have problems which
include: (1) implantation of a mechanical device and its need for replacement every
4-7 years, (2) surgical and mechanical complications resulting from the implanta-
tion of the device, (3) negative physical and psychological effects of an implanted
mechanical device, (4) a prevalent need to use concurrent antiarrhythmic therapy
and/or radiofrequency modulation/ablation, and (5) a relatively high cost. Therefore,
there is a need to develop alternative therapies for treatment of conduction abnor-
malities that overcomes the negative aspects of current treatment methods.
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