history of icds
Post on 18-Dec-2014
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The Electrical Management of Cardiac Rhythm Disorders
Tachycardia
History of ICDs
The Genesis of ICDs
● The idea of the ICD came to Dr. Michel Mirowski when his friend died of SCD
● Concept: could a defibrillator be implanted in the body?
● Technological challenges○ Could an implantable device
deliver sufficient energy?
○ Could leads be developed to carry that much energy?
○ How would the device detect arrhythmias?
○ How could defibrillation become “automated”?
Dr. Michel Mirowski● Dr. Harry Heller died of SCD in 1966● His friend, Dr. Michel Mirowski, knew that he might have
lived had he received defibrillation immediately● Technological and even ethical hurdles
○ Was it ethical to even test such a device on humans?● By 1969, Dr. Mirowski was working on the first
experimental models of what would later become the ICD● But it would be almost 20 years before the device was
commercially available!
Time Line
● Sinai Hospital of Baltimore recruited Dr. Mirowski and offered him opportunity to work on ICD idea
● At Sinai, Mirowski teamed up with Martin Mower in the research lab
● In 1969, experimental model● First transvenous defibrillation
(1969)● Canine implants (1970s)● First human implant: 1980
(Johns Hopkins, Baltimore)
Technological Challenges● Capacitor technology allowed small battery to store and
deliver large amount of energy● Transvenous defibrillation leads could carry defibrillation
energy to the inside of the heart● Circuitry could sense cardiac rhythms and interpret
potentially dangerous ventricular tachyarrhythmias● Device could be downsized enough to implant in the body
Early Devices
● 1980-1985 clinical trial of first ICDs
● 1985 FDA approved first ICD for human use
● Those first devices were 10 times the size of modern ICDs!
● Their large size mandated an abdominal implant
● Thoracotomy required to implant leads
Road to ICDs
ICD Evolution● Cardioversion (lower-energy shocks) and “tiered therapy”● Programmability (1988)
○ First ICDs were custom-built since cutoff rates were set at the factory!
● Biphasic waveforms● Multiple zones (VT/VF)● Transvenous ICD leads● Radically downsized generators (pectoral implants)● Full-featured integrated pacemakers
Defibrillation Leads
Single-Coil Defib Leads
● Pacing requires one or more electrodes on the lead to pace sense
● Shocking requires one or more “coils” on the lead to defibrillate● A single-coil lead has one coil on the lead and forms the
electrical circuit by using the ICD can as the other pole to complete the circuit
Modern Defibrillation Leads● Integrated bipolar and true bipolar leads
○ Refers to sensing cardiac signals○ Integrated bipolar uses distal shocking coil to sense
cardiac signals○ True bipolar has dedicated distal sensing electrode
● Single-coil and dual-coil designs● Very thin, comparable to some pacing leads!● Choice of lead fixation mechanisms
○ Active fixation (helix, corkscrew)○ Passive fixation (fins, tines)
● Steroid elution option
Progress: The Implant Procedure
THEN● Open-chest● Took several hours● General anesthesia● Several days hospital stay● Large device● Abdominal implant● No or very limited
programmability
NOW● Minimally invasive implant● Can take < 1 hour● Conscious sedation● May be done outpatient● Devices ~ size of
pacemaker● Pectoral implant● Extensive
programmability
Progress: Device Functionality
THEN● Very few programmable
options● Short service life● Only one therapy (defib)● No pacing capability (if pacing
was needed, a second device might be required)
● Could only be monitored in-clinic
NOW● Lots of programmability,
including advanced features● Four to six years service life● Tiered therapy, even ATP● Full pacing capability including
some dual-chamber rate-responsive pacing with advanced features
● Remote patient monitoring
Device Acceptance● The first ICDs were considered a device of last resort
○ Patients had to be drug-refractory and survived at least two episodes of SCD
● Early concepts pitted drugs against devices as if they were mutually exclusive
● Devices became acceptable as first-line therapy for certain types of secondary-prevention patients
● Today, we know devices can provide additive benefits to drug therapy and that combination therapy (drugs plus devices) is ideal for most patients
● Recent studies have shown the mortality benefits of primary prevention therapy
The Future of ICDs
● Smaller, flatter devices (improved capacitor technology)
● Longer-lived devices (improved battery technology)
● CRT (addition of a third lead)● Remote patient monitoring● Wireless patient monitoring● Special algorithms● Expanded memory● More automatic features● Built-in monitors
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