Medtronic Device Features & Algorithms

Comprehensive vocabulary flashcards covering Medtronic cardiac rhythm management (CRM) device features, pacing algorithms, tachyarrhythmia detection, CRT optimization, and diagnostic tools based on the lecture material.

Ventricular Safety Pacing (VSP)

A bradycardia feature operating in $\text{DDD/DDI + R}$ that detects ventricular crosstalk following an atrial pace ($\text{AP}$) within a $\text{VSP}$ window ($110\,\text{ms}$ at low pacing rates, $70\,\text{ms}$ at elevated rates) and delivers a ventricular pace ($\text{VP}$) at the end of the window to avoid inappropriate inhibition.

Post-Ventricular Atrial Blanking (PVAB)

A programmable interval ($150\,\text{ms}$ nominal for Partial/Partial+, $30\,\text{ms}$ for Absolute) following a ventricular event designed to eliminate far-field $R$-wave oversensing on the atrial channel.

Post-Ventricular Atrial Refractory Period (PVARP)

A refractory interval following any ventricular event where intrinsic atrial events are labeled as refractory ($\text{AR}$) to prevent tracking of retrograde $P$-waves that could trigger pacemaker-mediated tachycardia ($\text{PMT}$).

Rate Adaptive AV (RAAV)

A timing feature that mimics physiological conduction by shortening programmed $AV$ intervals as heart rate rises and lengthening them as heart rate slows, operating between a Start Rate ($90\,\text{bpm}$) and a Stop Rate ($140\,\text{bpm}$).

Managed Ventricular Pacing (MVP)

An atrial-based pacing mode ($\text{AAI + R}$) that promotes intrinsic conduction and switches to $\text{DDD + R}$ if $2$ of the last $4$ $A\text{-}A$ intervals lack a ventricular sensed event, scheduling backup ventricular pacing $80\,\text{ms}$ after scheduled atrial paces.

MVP 2.0

An enhancement to $\text{MVP}$ that monitors the last $5$ $AV$ intervals to prevent long $AV$ delays, reduces pauses after onset $AV$ block or PVCs, and prevents sensor-driven rate increases from shortening the $V\text{-}A$ interval to less than $40\%$ of the total $A\text{-}A$ interval.

Rate Hysteresis

A pacing feature in $\text{VVI}$ mode that provides an extended escape interval ($2000\,\text{ms}$ / $30\,\text{bpm}$ nominal) following a spontaneous ventricular sensed event ($\text{VS}$) to permit intrinsic ventricular conduction before resuming pacing at the lower rate.

Rate Drop Response (RDR)

A pacing feature designed for carotid sinus syndrome or vasovagal syncope that monitors for sudden heart rate drops via Drop Detection or Low Rate Detection and paces at a rapid Intervention Rate ($100\,\text{bpm}$) for a set Intervention Duration ($2\,\text{minutes}$).

Total Atrial Refractory Period (TARP)

The sum of the sensed $AV$ interval and the post-ventricular atrial refractory period ($\text{SAV} + \text{PVARP}$), which determines the 2:1 block point of dual-chamber pacing modes via the formula $\text{TARP (ms)} = \frac{60000\,\text{ms}}{\text{2:1 Block Point (bpm)}}$.

PVC Response

An algorithm that identifies a premature ventricular contraction ($\text{PVC}$) as any ventricular sensed event following another ventricular event without an intervening atrial event, extending $\text{PVARP}$ by $400\,\text{ms}$ and initiating one cycle of $\text{NCAP}$.

PMT Intervention

An algorithm that terminates pacemaker-mediated tachycardia by detecting $8$ consecutive $\text{VP-AS}$ intervals shorter than $400\,\text{ms}$, extending $\text{PVARP}$ to $400\,\text{ms}$ on the 9th cycle to block retrograde conduction, and suspending further intervention for $90\,\text{seconds}$.

Enhanced PMT Intervention

A confirmation algorithm for pacemaker-mediated tachycardia that extends the $\text{SAV}$ interval by $50\,\text{ms}$ across $3$ cycles to verify whether the $\text{VP-AS}$ interval remains fixed before declaring a $\text{PMT}$ and extending $\text{PVARP}$.

Atrial Chamber Reset (ACR)

An Atrial Capture Management method utilized during stable sinus rhythm ($\le 87\,\text{bpm}$) that evaluates capture by determining whether an atrial test pace resets the intrinsic atrium (yielding no refractory sensing, $\text{AR}$).

Ventricular Rate Stabilization (VRS)

A rate-smoothing algorithm that responds to a $\text{PVC}$ by temporarily increasing the ventricular pacing rate by a programmed Interval Increment ($150\,\text{ms}$) and gradually tapering back to the baseline rate up to a maximum of $100\,\text{bpm}$.

Non-Competitive Atrial Pacing (NCAP)

An algorithm that prevents pacing the atrium during its vulnerable period by delaying a scheduled atrial pace if an intrinsic atrial event occurs in the refractory period ($\text{AR}$), enforcing an $\text{NCAP}$ interval of $300\,\text{ms}$.

Atrial Preference Pacing (APP)

An atrial arrhythmia prevention algorithm that continuously paces the atrium slightly above the intrinsic rate by decreasing the pacing interval by an Interval Decrement ($30\,\text{ms}$) following any non-refractory sensed atrial beat ($\text{AS}$).

AT/AF Mode Switch

A protection mechanism in tracking modes ($\text{AAI/DDD/VDD + R}$) that switches to non-tracking $\text{DDIR}$ when $3$ consecutive $V\text{-}V$ intervals contain $\ge 2$ atrial events and the median of the last $12$ $A\text{-}A$ intervals exceeds the $\text{AT/AF}$ Detection Rate ($171\,\text{bpm}$).

Conducted AF Response (CAFR)

An algorithm operating in non-tracking modes ($\text{DDIR/VVIR}$) that adjusts the pacing rate up or down on a beat-to-beat basis to promote ventricular rate regularity during episodes of conducted atrial fibrillation.

Post Mode-Switch Overdrive Pacing (PMOP)

An algorithm designed to prevent early recurrence of atrial fibrillation ($\text{ERAF}$) by maintaining overdrive pacing in $\text{DDIR}$ at a programmed rate ($80\,\text{bpm}$) for a programmed duration ($5\,\text{minutes}$) immediately after an $\text{AT/AF}$ episode terminates.

Reactive ATP

An atrial therapy feature that redelivers antitachycardia pacing sequences during an ongoing atrial tachyarrhythmia if the rhythm demonstrates a change in cycle length or regularity, or when a programmed time interval expires.

Probabilistic Counter

A detection counter utilized for irregular ventricular tachyarrhythmias ($\text{VF}$) requiring a specific proportion of fast intervals, nominally $30$ out of $40$ consecutive intervals ($75\%$), to satisfy episode detection criteria.

Combined Count (NCID)

A non-programmable tachyarrhythmia algorithm that prevents detection delays during zone fluctuations by triggering combined detection when $6\,\text{FS}$ events occur and satisfying the criterion $\text{NCID} = \text{VF NID} \times \frac{7}{6}$ ($35/40$ nominal).

Intrinsic ATP (iATP)

An automated antitachycardia pacing therapy for ventricular tachycardia that evaluates post-pacing interval ($\text{PPI}$) responses to adjust pulse counts and cycle lengths dynamically based on whether failure was caused by failure to reach, reset, or loss of capture.

Confirmation+

An algorithm for non-committed ventricular shocks that evaluates the last $4$ of $6$ intervals prior to capacitor completion to calculate rhythm regularity and aborts defibrillation/cardioversion if spontaneous termination or slowing occurs.

ATP Before/During Charging

A programmable ICD therapy option that delivers antitachycardia pacing before or during capacitor charging in the $\text{VF}$ zone, utilizing ChargeSaver and Smart Mode to abort unnecessary high-voltage shocks if converted.

Progressive Episode Therapies

An ICD algorithm rule ensuring that each redetected tachyarrhythmia therapy in an episode delivers equal or greater energy than the preceding therapy and skips slower or lower-tier therapies (e.g., skipping ATP after cardioversion).

PR Logic

A dual-chamber SVT discrimination algorithm that evaluates rate, AV conduction patterns (junctional, antegrade, retrograde), regularity, AV dissociation, far-field $R$-waves, and atrial fibrillation evidence to withhold inappropriate ventricular therapies.

Wavelet

An SVT discrimination morphology algorithm that compares presenting electrogram waveforms to a stored baseline normal sinus rhythm QRS template, withholding ventricular therapy if at least $3$ of the last $8$ complexes achieve a match threshold ($\ge 70\%$).

Onset

A single-chamber SVT discriminator that calculates the acceleration of ventricular rate by comparing the average of $4\,V\text{-}V$ intervals against the preceding $4$, withholding detection if the onset is gradual rather than sudden ($\le 81\%$ nominal).

Stability

An SVT discriminator evaluating beat-to-beat cycle length variability in the $\text{VT}$ zone to differentiate regular monomorphic ventricular tachycardia from irregular atrial fibrillation with rapid ventricular response ($\text{AF with RVR}$).

T-Wave Oversensing (TWOS) Discrimination

A non-arrhythmic discriminator that applies differential filtering to identify recurring high-frequency $R$-wave and low-frequency $T$-wave patterns, withholding ventricular therapy if at least $4$ of the last $20$ 6-beat sets demonstrate $T$-wave oversensing.

RV Lead Noise Discrimination

An algorithm that identifies lead fracture or artifact by comparing high-frequency signals on the near-field EGM ($V_{\text{tip}}\text{ to }V_{\text{ring}}$) against the far-field EGM ($\text{Can to RVcoil}$), withholding therapy if the far-field amplitude averages $<1\,\text{mV}$.

SVT V. Limit

A programmed cycle length boundary ($240\,\text{ms}$ nominal) below which SVT discriminators like PR Logic and Wavelet are overridden, preventing the device from withholding ventricular therapies at dangerously rapid rates.

High-Rate Timeout

A safety override timer that terminates therapy withholding and delivers programmed therapies if a tachyarrhythmia persists beyond a specified duration despite SVT discrimination.

VectorExpress

An automated testing feature in CRT devices that rapidly determines pacing thresholds, lead impedances, and relative battery longevity across all available left ventricular pacing vectors (including electrical delay in version 2.0).

Multiple Point Pacing (MPP)

A CRT pacing feature capable of delivering two distinct left ventricular pacing pulses per cardiac cycle across quadripolar electrodes within an $80\,\text{ms}$ maximum window to improve left ventricular resynchronization.

CardioSync

A diagnostic optimization tool that records intrinsic $AV$ intervals, $P$-wave widths, and $QRS$ durations during extended pacing at $40\,\text{bpm}$ and $80\,\text{bpm}$ to calculate patient-specific recommendations for $AV$ and $V\text{-}V$ delays.

AdaptivCRT

A dynamic CRT pacing algorithm that automatically alternates between Adaptive LV Only pre-pacing (synchronizing with intrinsic RV conduction) and Adaptive BiV pacing based on periodic assessments of intrinsic $AV$ conduction and $QRS$ duration.

Atrial Tracking Recovery (ATR)

An algorithm that identifies loss of CRT tracking due to fast atrial rates or PVCs ($8$ consecutive $VS\text{-}AR$ intervals) and temporarily shortens $\text{PVARP}$ on the 9th cycle to restore biventricular tracking.

Ventricular Sense Response (VSR)

A CRT feature that delivers an immediate ventricular pace following an intrinsic ventricular sensed event ($\text{VS}$) occurring below the Maximum Rate ($130\,\text{bpm}$) to preserve resynchronization therapy.

EffectivCRT During AF

A CRT algorithm that analyzes the morphology of paced beats on the left ventricular electrogram (requiring an initial negative deflection) to adjust ventricular pacing rates and ensure effective CRT capture during atrial fibrillation.

Sensing Integrity Counter (SIC)

A diagnostic monitor that logs short ventricular intervals ($\le 20\,\text{ms}$ post-sense blanking); an accumulated count exceeding $300$ triggers a Quick Look II alert for possible lead fracture, loose setscrew, or oversensing.

Lead Integrity Alert (LIA)

A safety surveillance algorithm that triggers an alert and extends detection counters if $2$ of $3$ criteria are met: out-of-range RV lead impedance, an $\text{SIC}$ score $\ge 30$ within $3\,\text{days}$, or $2$ High Rate-NS episodes with average cycle length $\le 220\,\text{ms}$.

Cardiac Compass

A long-term clinical diagnostic report that plots daily trends over up to $14\,\text{months}$, tracking fluid indices, arrhythmia burden, heart rate variability, patient activity, and pacing percentages.

PARTNERS HF

A heart failure diagnostic risk-stratification model that calculates a combined score from device diagnostics (including OptiVol fluid index, AT/AF burden, and pacing percentages), where a score $>2$ identifies a 5.5-fold higher risk of hospitalization.

TriageHF

A clinical tool that evaluates multiple trended diagnostic parameters (OptiVol 2.0, activity, AT/AF burden, ventricular pacing, shocks, heart rate variability) to categorize a patient's 30-day likelihood of heart failure hospitalization into Low, Medium, or High risk.

Lorenz Plot (Sinus Rhythm Pattern)

A scatterplot representation of consecutive $R\text{-}R$ intervals where points cluster tightly in the center origin, demonstrating low interval variability indicative of regular normal sinus rhythm.

Lorenz Plot (Atrial Fibrillation Pattern)

A scatterplot representation of consecutive $R\text{-}R$ intervals where points are widely dispersed across peripheral segments and absent from the central origin, demonstrating high irregularity and incoherence indicative of atrial fibrillation.