IBHRE CCDS flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

NBG pacemaker code

Five-position code: chamber paced, chamber sensed, response to sensing (I/T/D), rate modulation (R), and multisite pacing. Example DDDRO describes dual-chamber pacing and sensing with dual response, rate response, and no multisite pacing.

Pacing threshold

Minimum pacing output, expressed in voltage or pulse width, that consistently captures myocardium. Acute values are typically below 1.0 V at 0.4 ms; a significant rise suggests lead dislodgement, exit block, or maturation change.

Chronaxie

Pulse width at which threshold voltage equals twice the rheobase. For myocardium it is roughly 0.5 ms; programming near chronaxie minimizes energy while preserving capture and battery longevity.

Rheobase

The lowest voltage that captures myocardium at an infinitely long pulse width. It defines the strength-duration curve asymptote; shorter pulse widths require higher voltages than rheobase to achieve capture.

Sensing amplitude requirements

Acute signals typically need P wave above 1.5 to 2.0 mV and R wave above 5 mV for reliable sensing. Lower amplitudes risk undersensing, while excessively high sensitivity settings can cause oversensing of noise.

Lead impedance interpretation

Normal pacing impedance is roughly 300 to 1200 ohms. A doubling or rise above 2000 ohms suggests fracture or loose connection; a fall below 200 to 300 ohms suggests insulation breach or fluid ingress.

Defibrillation threshold

Lowest shock energy that reliably terminates ventricular fibrillation. A safety margin of at least 10 J below maximum device output is commonly targeted; inadequate margin prompts system revision such as lead repositioning or additional coils.

Upper limit of vulnerability

Highest shock energy that still fails to terminate VF when delivered during the vulnerable period. ICD testing demonstrating conversion at ULV and at maximum output supports an adequate safety margin.

Number of intervals to detect

NID is the count of consecutive tachyarrhythmia intervals required before therapy delivery. Higher NID reduces inappropriate shocks from brief SVT but delays therapy for true VT or VF.

SVT discriminators

ICD algorithms distinguishing supraventricular from ventricular tachycardia, including sudden onset, rate stability, and morphology criteria. They reduce inappropriate shocks but can withhold therapy for true VT if criteria are misapplied.

Biphasic ICD shock

Defibrillation waveform reversing polarity mid-shock, generally lowering DFT compared with monophasic shocks. Shock impedance typically 40 to 80 ohms; reversed polarity or high impedance can reduce first-shock success.

Pacemaker syndrome

Symptoms from loss of AV synchrony during ventricular pacing, including pulsatile neck veins, fatigue, and hypotension from cannon A waves. Managed by upgrading to dual-chamber pacing or reprogramming AV delay.

AV delay programming

Interval between atrial and ventricular pacing. Optimal delay preserves atrial contribution to filling; excessively long delay permits intrinsic conduction, while short delay may cause pseudofusion or reduced filling.

Hysteresis

Programming feature allowing the paced rate to drop below the base rate to permit intrinsic conduction. It reduces unnecessary ventricular pacing but can cause pauses and symptoms if intrinsic rate is unreliable.

Rate response sensor

Accelerometer or minute ventilation sensor adjusting pacing rate to activity. Sensitivity and slope settings determine response; inappropriate settings cause rate oscillations, palpitations, or inadequate rate support during exertion.

Mode switch

Algorithm changing from tracking to non-tracking mode (e.g., DDD to DDI or VVI) during atrial tachyarrhythmia. It prevents rapid ventricular pacing but may cause rate drop or AV dyssynchrony.

Far-field oversensing

Sensing of electrical signals from another chamber, such as R waves on the atrial lead. It can cause inappropriate mode switching or pacing inhibition; managed by reducing sensitivity or repositioning the lead.

T-wave oversensing

ICD sensing of the T wave as a ventricular event, potentially causing double counting and inappropriate shocks. Managed by adjusting sensitivity, decay settings, or lead position.

Lead dislodgement signs

Rising threshold, falling sensing amplitude, impedance change, or new pacing failure. Chest radiograph confirms position; management includes repositioning or replacement of the lead.

Pocket hematoma management

Post-implant bleeding into the device pocket. Small collections may resolve; expanding hematoma with tension or infection risk requires evacuation and hemostasis, with anticoagulation reviewed carefully.

Device infection

Pocket erosion, erythema, or positive cultures suggest infection. Complete system extraction is generally required because retained leads perpetuate biofilm; antibiotics alone rarely cure device-related infection.

Venous access complications

Pneumothorax, hemothorax, and subclavian vein thrombosis can follow axillary or subclavian access. Ultrasound guidance and contrast venography reduce risk; symptoms include dyspnea and arm swelling.

Magnet application

Placing a magnet over a pacemaker causes asynchronous pacing; over an ICD it suspends tachyarrhythmia detection and shocks. Used during MRI, surgery, or to stop inappropriate ICD therapy.

MRI-conditional device

System approved for MRI under specified conditions, including field strength, coil type, and lead configuration. Non-conditional systems may still be scanned with protocol review but carry higher risk.

Electromagnetic interference

External electrical sources can inhibit pacing, trigger mode switching, or cause inappropriate ICD shocks. Common sources include electrocautery, diathermy, and strong magnets; management includes reprogramming and monitoring.

Biventricular pacing

Cardiac resynchronization pacing both ventricles to correct dyssynchrony in heart failure with reduced ejection fraction and wide QRS. Response is assessed by QRS narrowing, symptoms, and echocardiographic measures.

Phrenic nerve stimulation

Diaphragmatic pacing from a lead near the phrenic nerve, causing hiccups or abdominal twitching. Managed by reducing output, reprogramming polarity, or repositioning the lead.

Pacing output safety margin

Programming output at least twice the measured threshold voltage is common practice to ensure capture despite threshold fluctuation. Higher outputs reduce battery longevity and may cause extracardiac stimulation.

Ventricular safety pacing

Feature delivering a ventricular pacing pulse shortly after an atrial event when crosstalk is sensed, preventing inhibition from far-field atrial signals. It avoids inappropriate pauses in dual-chamber systems.

Post-shock pacing

Pacing support delivered after ICD shocks, often at higher output because defibrillation can raise pacing thresholds temporarily. It ensures rate support during post-shock bradycardia or asystole.

Remote monitoring

Transmitted device data allowing early detection of lead failure, arrhythmia, or battery depletion. Alerts and scheduled transmissions reduce unnecessary clinic visits while improving safety surveillance.

Device end-of-life indicators

Elective replacement indicator (ERI) signals battery nearing depletion; end-of-life (EOL) indicates limited remaining service. Replacement planning should begin at ERI before EOL compromises therapy.