What is the best course of action for a patient with permanent atrial fibrillation (AF), a history of atrioventricular junction (AVJ) ablation, and a Medtronic Cardiac Resynchronization Therapy Pacemaker (CRT-P) device, who is experiencing elevated left ventricular threshold, non-sustained ventricular tachycardia (NS-VT), and has a biventricular pacing percentage of approximately 82%?

Immediate Action Required: Optimize Biventricular Pacing Through AV Junction Ablation

Given your patient's permanent AF with prior AVJ ablation, device dependency, elevated LV threshold, and suboptimal BiV pacing at 82%, you should immediately reprogram the device to maximize biventricular capture and address the elevated LV threshold, while monitoring the NS-VT episodes which are likely benign in this context.

Critical Issue: Suboptimal Biventricular Pacing

Your patient's BiV pacing percentage of ~82% is below the therapeutic threshold needed for CRT benefit:

• Target BiV pacing should be ≥90-95% to achieve clinical benefit from CRT 1, 2
• The European Society of Cardiology emphasizes that complete biventricular capture is "warranted as a quality standard of practice" in AF patients with CRT 1
• Studies demonstrate that achieving nearly 100% biventricular pacing is necessary to derive benefit from CRT 3

Why this matters for your patient: Since AVJ ablation was already performed (making the patient device-dependent), the suboptimal pacing percentage suggests either:

1. Programming issues that need optimization
2. Lead dysfunction (given the elevated LV threshold)
3. Intrinsic conduction competing with paced beats

Immediate Device Reprogramming Steps

1. Address the Elevated LV Threshold

• Increase LV output voltage to ensure consistent capture despite the elevated threshold 1
• Check LV lead impedance trends to rule out lead fracture or insulation breach 1
• Consider threshold testing at multiple vectors if a quadripolar LV lead is present
• Document the specific threshold value and compare to baseline/prior interrogations

2. Optimize Programming for Maximum BiV Capture

Since the patient has permanent AF with prior AVJ ablation and is device-dependent, program the device as follows:

• Set to VVIR or DDIR mode (not DDDR, as patient has permanent AF) 1
• Base rate: 60-70 bpm to ensure adequate pacing and prevent intrinsic conduction 1
• Upper rate limit: 120-130 bpm to allow appropriate rate response
• Enable rate-adaptive pacing if chronotropic incompetence is present 1
• Maximize AV delay (if any residual AV conduction exists despite ablation) to prevent fusion beats
• Check BiV sense response settings to ensure proper sensing without inappropriate mode switching 1

3. Verify Complete AVJ Ablation

• Review device diagnostics for any evidence of conducted beats
• If intrinsic conduction is present (which would be unusual post-AVJ ablation), this explains the 82% pacing
• If incomplete AVJ ablation is discovered, refer back to EP for completion 1, 2

The NS-VT Episodes: Clinical Context

The 6 episodes of NS-VT (longest 10 seconds at 158 bpm) require assessment but are likely not immediately concerning in this context:

• NS-VT is common in patients with LV dysfunction and contributes to increased mortality risk when >10 PVCs per hour occur 1
• However, your patient has a CRT-P device (no defibrillator backup), which was the appropriate choice given the clinical indication
• The European Society of Cardiology notes that "ICD back-up should be considered in patients at high risk of sudden death" 1

Action items for NS-VT:

• Document the morphology and coupling intervals of the NS-VT episodes
• If PVC burden is >24% with short coupling intervals (<300 ms), this could represent PVC-induced cardiomyopathy requiring ablation 1
• Consider Holter monitoring to assess total ventricular ectopy burden 1
• If symptomatic or if contributing to reduced BiV pacing percentage, consider amiodarone or catheter ablation 1
• Reassess ICD indication if patient meets criteria (LVEF ≤35%, NYHA II-III on optimal therapy) 1, 2

Evidence Supporting Aggressive BiV Pacing Optimization

The evidence strongly supports maximizing BiV pacing in your patient population:

• Mortality benefit: A randomized trial showed that CRT with AVJ ablation in permanent AF patients reduced all-cause mortality (HR 0.26,95% CI 0.10-0.65, P=0.004) compared to pharmacological rate control 4
• Heart failure outcomes: The APAF-CRT trial demonstrated that ablation + CRT reduced the composite of death or HF hospitalization (HR 0.40,95% CI 0.22-0.73, P=0.002) 4
• Systematic review data: CRT with AVJ ablation showed substantial reduction in all-cause mortality (risk ratio 0.42) and cardiovascular mortality (risk ratio 0.44) compared to CRT without complete AVJ ablation 1

Follow-Up Plan

Within 1-2 weeks:

• Repeat device interrogation to confirm BiV pacing percentage has improved to ≥95%
• Verify LV threshold stability with increased output settings
• Review battery longevity given increased output requirements

Within 1-3 months:

• Clinical assessment for HF symptom improvement
• Consider echocardiogram to assess LV function and mechanical synchrony
• Holter monitoring if NS-VT burden remains concerning

Ongoing:

• Monitor BiV pacing percentage at every device check (target ≥95%) 1, 2
• Assess for symptoms related to ventricular arrhythmias
• Optimize heart failure medical therapy per guidelines 5, 2, 6

Common Pitfalls to Avoid

• Don't accept <95% BiV pacing in a device-dependent patient with prior AVJ ablation—this represents a programming or hardware issue that must be corrected 1, 2
• Don't ignore elevated LV thresholds—these can lead to loss of capture and treatment failure 1
• Don't overreact to brief NS-VT episodes in a CRT-P patient unless they're symptomatic or contributing to reduced BiV pacing 1
• Don't delay addressing suboptimal pacing—the mortality and morbidity benefits of CRT depend on achieving near-complete BiV capture 1, 2, 4