ICD Programming

Definition

ICD programming is the configuration of detection zones, detection intervals, antitachycardia pacing (ATP) schemes, shock energies, supraventricular tachycardia (SVT) discriminators, bradycardia pacing and oversensing-rejection algorithms in an implantable cardioverter-defibrillator. Its goal is to deliver therapy for ventricular arrhythmias promptly while minimising inappropriate shocks and unnecessary ventricular pacing. Programming is device-specific: the same clinical principle is implemented with different parameter names and defaults across manufacturers (sources/icd-programming-hrs-2019, rating: high).

Key Concepts

The four programming domains

• Bradycardia programming: single-chamber devices are typically set to VVI 40 bpm; dual-chamber devices to DDD with an algorithm to avoid unnecessary RV pacing (MVP, VIP, IRS Plus/OPT, RYTHMIQ, AV Search+, SafeR); CRT devices to DDD ± rate response with device-specific AV/VV optimisation (sources/icd-programming-hrs-2019, rating: high).
• Why RV pacing is minimised: DAVID showed that DDDR at 70 bpm worsened heart failure and mortality compared with VVI-40 backup pacing, because of unnecessary RV pacing; MVP or extended AV delay reduces the burden, and AV intervals beyond 250–300 ms should be avoided. In CRT-D, the target is biventricular pacing ≥98% — MADIT-CRT found no CRT benefit below 90%, with every 1% increase associated with a 6% reduction in HF/death. After AV junction ablation for AF, programme a minimum rate of 80–90 bpm for the first 1–2 months to avoid QT prolongation and sudden death. (sources/icd-programming-hrs-2015, rating: high)
• Tachycardia detection: either a delayed-therapy strategy (high rate thresholds with long detection intervals, e.g. 30/40 intervals at ~188–231 bpm) or a high-rate strategy (a single high-rate zone, e.g. 8/10 intervals plus 2.5 seconds at 200 bpm). A monitor zone is optional (sources/icd-programming-hrs-2019, rating: high).
• Tachycardia therapy: ATP first, with at least one burst of 8 pulses at ~88% of the VT cycle length and a 10 ms scan decrement, followed by shocks; ATP during charging in the VF zone where available (sources/icd-programming-hrs-2019, rating: high).
• Defibrillation testing: the 2019 focused update preserves the 2015 position; manufacturer tables specify full-output shocks "unless DFT guided", so routine DFT is not mandated but remains a clinical option (sources/icd-programming-hrs-2019, rating: high).

ATP delivery site (investigational)

• Conventional ATP is delivered from the RV lead. The site is fixed by lead position rather than programmable, but it determines the geometry of myocardial capture during a train.
• In a canine ischaemia-reperfusion model, His-bundle ATP terminated VT as often as RV apical ATP (23 vs 25 trials of 64 each) but caused fewer VT accelerations (6 vs 14, p = 0.05) and fewer degenerations into VF (1 vs 7, p = 0.02). Incomplete epicardial capture was less frequent with His ATP (25% vs 43%, p = 0.05). (sources/his-atp-vt-jce-2023, rating: medium)
• LBBA ATP in the same model was more effective than RV ATP (70.2% vs 47.3%, risk ratio 1.44), without a safety penalty. (sources/lbbap-atp-jaccep-2026, rating: medium)
• Neither site is a programmable option in current ICDs; these data bear on lead selection — notably the emerging LBBA defibrillation lead — not on detection or therapy parameters.

Detection programming when the VT rate is known

• When a clinical VT cycle length is known, the VT detection zone is set 10–20 bpm below the clinical VT rate, with ATP as the first therapy and shocks reserved for failures (sources/icd-programming-hrs-2019, rating: high).
• When there is no VT history, programming VT zones to OFF (or monitor only) is acceptable, because treating slow, haemodynamically tolerated VT with shocks may cause more harm than benefit (sources/icd-programming-hrs-2019, rating: high).
• The Medtronic and Abbott translations switch the FVT zone OFF and rely on ATP during charging in the VF zone, which achieves similar functionality while permitting tiered ATP (sources/icd-programming-hrs-2019, rating: high).

SVT discriminators

• Single-chamber discriminators are morphology-based (wavelet, far-field morphology, MorphMatch); dual-chamber discriminators add AV association logic (PR Logic, SMART, PARAD+, RhythmID) plus interval stability and onset (sources/icd-programming-hrs-2019, rating: high).
• A SVT upper limit around 230 bpm is standard: above this rate, discriminators are not applied and therapy is delivered (sources/icd-programming-hrs-2019, rating: high).
• Discriminators are not required in complete heart block, where AV dissociation makes them uninformative (sources/icd-programming-hrs-2019, rating: high).

Oversensing rejection

• Lead-integrity alerts, T-wave oversensing filters and RV lead-noise discrimination are switched ON where available; these address the common causes of inappropriate shocks other than SVT (sources/icd-programming-hrs-2019, rating: high).
• The 2019 update exists precisely because some manufacturer-translated settings produced adverse outcomes; the writing group's principle is that randomised trials and large registries should outweigh anecdotal reports (sources/icd-programming-hrs-2019, rating: high).

Subcutaneous ICD programming

• The Boston Scientific translation specifies an S-ICD shock zone ≥230 bpm and a conditional zone ≥200 bpm (or 10–20 bpm below a known VT rate), with post-shock pacing considered ON (sources/icd-programming-hrs-2019, rating: high).
• S-ICD discrimination differs from transvenous devices: it relies on morphology and rate, and cannot use ATP (sources/icd-programming-hrs-2019, rating: high).

Relationship to clinical outcomes

• Programming is a modifiable determinant of shock burden: inappropriate shocks are associated with worse quality of life and, in observational data, worse outcomes, while unnecessary RV pacing causes pacing-induced cardiomyopathy (sources/pacing-induced-cmp-hrs-2014, rating: medium).
• The evidence base for programming recommendations comes largely from trials of high-rate versus conventional detection and ATP versus shock-first strategies, which the 2015 consensus synthesised and the 2019 update preserved (sources/icd-programming-hrs-2019, rating: high).

Evidence base for detection and therapy programming

• Prolonged detection (30/40 intervals or an equivalent time delay) is the default, supported by PREPARE, RELEVANT, MADIT-RIT, ADVANCE III and PROVIDE (~7,000 patients): a 50% reduction in inappropriate shocks, a 30% reduction in all-cause mortality in meta-analysis, and no increase in syncope. (sources/icd-programming-hrs-2015, rating: high)
• VF zone rate cutoff ≥200 bpm for primary prevention: MADIT-RIT arm B (200 bpm) reduced inappropriate therapy by 80%, with mortality 3.2% vs 6.6% against conventional 170 bpm programming; SVT and VT rates overlap most between 181 and 213 bpm. (sources/icd-programming-hrs-2015)
• ATP first for all VT, including fast VT (CL 240–320 ms): PainFREE Rx II showed a 71% relative reduction in shocks, a second burst raised first-burst efficacy from 64% to 83%, an 8-pulse burst was as effective as 15 (ADVANCE-D), and burst outperformed ramp for fast VT (PITAGORA ICD). ATP during capacitor charging is safe and effective. (sources/icd-programming-hrs-2015)
• Shocks are not benign: appropriate shocks were associated with a 5-fold mortality increase in SCD-HeFT and inappropriate shocks with a 2-fold increase, which is why shock minimisation is a primary programming goal rather than a secondary one. (sources/icd-programming-hrs-2015)

Defibrillation threshold testing

• Routine DT can be safely omitted for a standard left-sided transvenous ICD with a confirmed lead position (R wave ≥5–7 mV): SIMPLE (n=2,500) was non-inferior without testing, and NORDIC-ICD (n=1,077) showed 3.0% non-inferior first-shock efficacy. (sources/icd-programming-hrs-2015, rating: high)
• DT remains reasonable for the S-ICD, where there are no safety data without testing, when lead position or system integrity is uncertain, and at operator discretion in HCM, channelopathies or right-sided implants.
• DT is contraindicated with intracardiac thrombus, with AF without ≥3 weeks of therapeutic anticoagulation, and in haemodynamic instability.
• Anodal shock polarity is preferred: cathodal polarity carried an odds ratio of 2.37 for shock failure in the MODALITY registry. (sources/icd-programming-hrs-2015)

Contradictions / Open Questions

• How much of the trial evidence transfers across manufacturers is uncertain. The 2015 recommendations were derived from trials performed in specific device platforms, and Appendix B's translations were approximations; the 2019 update corrected settings that had caused harm but did not generate new outcome data confirming the revised values are safer (sources/icd-programming-hrs-2019, rating: high).
• The optimal rate threshold for the high-rate strategy is unresolved. Rates of 200 bpm (Boston Scientific option 2) and >255 bpm (MicroPort) are both proposed; no head-to-head trial establishes a single best threshold (sources/icd-programming-hrs-2019, rating: high).
• Routine defibrillation testing remains contested. The consensus retains it as optional, but the balance between detecting inadequate safety margins and the small procedural risk of testing is not settled by randomised data in this document (sources/icd-programming-hrs-2019, rating: high).
• Programming recommendations lag device innovation. Conduction-system pacing, leadless pacemakers and extravascular ICDs are not addressed, and their detection/therapy trade-offs may differ substantially (sources/icd-programming-hrs-2019, rating: high).
• S-ICD programming evidence is thinner than for transvenous devices; the ≥230 bpm shock zone and conditional zone recommendations rest on registry and manufacturer data rather than dedicated randomised comparisons (sources/icd-programming-hrs-2019, rating: high).
• The value of non-RV ATP delivery sites is untested in humans. The His and LBBA data come from the same small canine ischaemia-reperfusion model, with induced VT and non-selective capture at twice diastolic threshold; no human study has compared ATP success or adverse outcomes by lead position. (sources/his-atp-vt-jce-2023, rating: medium) (sources/lbbap-atp-jaccep-2026, rating: medium)

Connections

• Related to entities/ICD — the device being programmed
• Related to entities/S-ICD — subcutaneous system with distinct programming constraints
• Related to concepts/Sudden-Cardiac-Death — the outcome programming seeks to prevent
• Related to concepts/Pacing-Induced-Cardiomyopathy — why unnecessary RV pacing is avoided in dual-chamber devices
• Related to concepts/Antiarrhythmic-Drugs — drug therapy alters detection rates and arrhythmia inducibility
• Related to entities/Heart-Failure — CRT programming is integrated in the same device

Sources

• sources/icd-programming-hrs-2015
• sources/icd-programming-hrs-2019
• sources/pacing-induced-cmp-hrs-2014
• sources/his-atp-vt-jce-2023
• sources/lbbap-atp-jaccep-2026