STIMULATION OF EXCITABLE TISSUES - Design and Development of Medical Electronic Instrumentation - page 357

OTHER CLINICAL APPLICATIONS OF ELECTRICAL
CURRENT DELIVERY TO TISSUES

There are many clinical applications for the delivery of electrical currents to the body that
do not involve the activation of excitable tissue. Unfortunately, the marketplace is also lit-
tered with all sorts of “energy medicine” contraptions and procedures that claim to “bal-
ance the flow of vital energy in the body” using currents delivered to the body. Needless

to say, the latter are all either extremely controversial or totally unproven. Some, such as
electroacupuncture, are simply old “alternative” treatments with an electrical twist. Others
are without doubt the electrical equivalents of snake oil. Let's take a look at what is real
and what is quack.

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Electrosurgery and RF Ablation

The use of alternating currents for surgical techniques was attempted by D'Arsonval in
1891. However, the technique did not become practical until 1928, when physicist William
T. Bovie developed an RF electrosurgical unit (ESU) for use in the operative environment.
Developments in solid-state circuitry and advances in the methodology of RF signal mod-
ulation as well as inventions related to the precise control of tip temperature have enabled
all sorts of interventional applications for RF-based surgical tools (Table 7.3).
Depending on how RF is applied, as well as the crest factor (the ratio of peak voltage
to root mean square voltage), the waveform (damped or unmodulated sinusoid), and the
power output, three di

ff erent electrosurgical e ff ects can be achieved:

1. Electrosurgical cutting : electric sparking to tissue with a cutting e ff ect

2. Electrosurgical fulguration : electric sparking to tissue without signi fi cant cutting, also

use bleeding
3. Electrosurgical desiccation 8 : low-power coagulation without sparking, also known
as contact coagulation mode; used to control local bleeding and enables point coag-
ulation of tissues

known as noncontact coagulation or spray mode ; used to control di ff

flows from a tip electrode into the tissue, producing ionic agitation in
the tissue about the electrode tip as the ions attempt to follow the changes in direction
of the alternating current. This agitation drives water from the cells, leading to desiccation
and coagulation (which occurs at a temperature of approximately 48°C). Further increases
in temperature due to ionic frictional heating in the tissue surrounding the electrode are
responsible for cutting and fulguration.
Today, RF energy delivered via catheters to the heart is being used to treat cardiac
arrhythmias. RF ablation (selective destruction) has replaced traditional surgical procedures
in the treatment of refractory supraventricular arrhythmias and ventricular tachycardia by
delivering energy to selectively destroy the accessory conduction pathways responsible for
the arrhythmia.

The RF current fl

Iontophoresis

Iontophoresis is an accepted method of drug delivery similar to the passive transdermal
medication patches now on the market for smoking cessation and hormone therapy.
However, iontophoresis uses low-level electrical current to speed up delivery of the drug
ions into the skin and surrounding tissues (Table 7.4). Iontophoretic drug delivery systems

8 Not to be confused with electrocautery , which is the coagulation of blood or tissue by means of an electrically
heated wire, where the current heats only the wire and does not pass through the patient's body.