Defibrillators and ICDs Quiz

Defibrillators & ICDs

• Defibrillators are used to treat life-threatening cardiac arrhythmias like ventricular fibrillation and pulseless ventricular tachycardia.
• These devices deliver electrical energy to the heart to restore normal rhythm.
• Defibrillators use high-voltage pulses to depolarize the myocardial fibers simultaneously.
• Arrhythmias are caused by problems in the heart's electrical impulse generation or conduction.
• Arrhythmias can lead to the impairment or disruption of coordination within the heart's muscle fibers, potentially causing fibrillation.
• Ventricular fibrillation is uncoordinated myocardial fibrillation, with no ejection of blood.
• On an ECG, ventricular fibrillation shows irregular and disorganized depolarizations.
• Pulseless ventricular tachycardia involves a regular and fast sequence of wide QRS complexes.

Ventricular Arrhythmias

• Ventricular fibrillation (VF) is a life-threatening arrhythmia characterized by irregular and disorganized electrical activity in the ventricles.
• In VF, the ventricles quiver instead of contracting effectively, preventing the heart from pumping blood.
• Pulseless ventricular tachycardia (VT) is another dangerous arrhythmia where the ventricles contract very rapidly, but without effective blood pumping.
• VT often shows a regular pattern of wide QRS complexes on an ECG.

Defibrillation

• The device has a charging circuit, and a separate circuit to discharge.
• The charging circuit fills a capacitor.
• The average time to charge the device is about 8 to 10 seconds.
• The device delivers an electrical current or pulse with variable preselectable levels typically between 2 to 360 Joules.
• The defibrillation pulse ranges between 3 to 8 milliseconds in current.
• Internal current varies between 10 - 27 amperes.
• The external current is between 22 - 60 amperes.
• Automatic safety discharge happens after approximately 10 seconds if there's no shock triggered, and when a new energy level is chosen as well as with technical malfunction.

Energy Waveform

• Energy waveforms are time-based sequences of energy output, attempting to minimize myocardial damage.
• The shape of the waveform determines the energy supplied to the patient.
• The duration of energy delivery is also crucial.

Waveform Types

• Monophasic waveforms deliver current in one polarity.
• Damped sinusoidal waveforms decrease gradually to zero.
• Truncated exponential waveforms decrease abruptly to zero.
• Biphasic waveforms deliver current in two phases—positive and negative—in a specific sequence during the electrical discharge.
• There are no studies of triphasic waveforms' use compared with biphasic.

Transthoracic Impedance (TTI)

• Transthoracic impedance (TTI) is the impedance between defibrillation paddles.
• It refers to energy dissipation in the chest during defibrillation; only a small proportion of energy reaches the heart.
• Common ranges for adults are 70-80 Ω.
• TTI is affected by factors like electrode size, distance, skin-electrode interface, electrode pressure, and body phase.

Defibrillator Types

• Transthoracic devices include manual, semiautomatic (AEDs), and fully automated defibrillators.
• Intracorporeal devices are implantable cardioverter-defibrillators (ICDs).
• ICDs have single, dual, or triple chamber systems or atrial defibrillators, depending on the arrhythmia(s) intended to be treated.

Technical Safety Aspects

• Direct contact with electrodes must be avoided.
• Moisture on the patient's skin is a no-no.
• Defibrillators are class IIb devices requiring an explosion-proof atmosphere if needed.
• The use of gel pads or conductive materials are needed to minimize impedance.
• All other devices connected to the patient should be defibrillation proof or disconnected for safety.
• Caution should be exercised with patients with energized implants.
• Trigger buttons should only be on the paddles.
• Maximum energy delivered is 360 Joules.
• Devices are to be plugged into a power source to ensure continuous and reliable usage.

Test your knowledge on defibrillators and implantable cardioverter-defibrillators (ICDs). This quiz will cover the functions, types, and the role these devices play in treating life-threatening arrhythmias, such as ventricular fibrillation and pulseless ventricular tachycardia. Get ready to enhance your understanding of cardiac care!