How to optimize biventricular (BiV) pacing in an elderly male with a history of aortic stenosis status post Transcatheter Aortic Valve Replacement (TAVR), nonischemic cardiomyopathy, Left Bundle Branch Block (LBBB), Congestive Heart Failure (CHF), Premature Ventricular Contractions (PVCs), and chronic atrial fibrillation on warfarin, with a biventricular pacing percentage of 88%?

Optimizing Biventricular Pacing in a Patient with Chronic Atrial Fibrillation and 88% BiV Pacing

In this patient with chronic atrial fibrillation and suboptimal 88% BiV pacing, the primary strategy is to achieve >95% BiV pacing through AV nodal ablation, as pharmacologic rate control has already failed and this is the only intervention proven to ensure effective CRT in permanent AF. 1

Immediate Priority: Achieve Near-Complete BiV Pacing

The target BiV pacing percentage should be >95% (ideally approaching 100%), as the current 88% is inadequate for optimal CRT benefit. 1 In patients with permanent atrial fibrillation, rapid ventricular conduction is the leading cause of inadequate BiV pacing percentages. 1

Step 1: Comprehensive Device Interrogation

Perform detailed device analysis to identify the specific cause of the 12% non-BiV paced beats: 1

• Analyze device counters to determine whether the loss of BiV pacing is due to:

  • High atrial fibrillation burden with rapid ventricular response (most likely in this patient) 1
  • Frequent PVCs (already noted in history) 1
  • Ventricular oversensing or undersensing 1
  • Inappropriate mode switches 1

• Review rate histograms to assess ventricular rate distribution during AF 1

• Check lead parameters: impedance, sensing thresholds, and pacing thresholds to rule out lead malfunction 1

Step 2: Optimize Device Programming for AF

Since the patient is in permanent AF, program the device to VVIR or DDIR mode (inhibited mode preferred for permanent AF): 1

• Set an appropriate base rate that balances adequate rate support during AF with allowing intrinsic conduction when ventricular rates are acceptable 1

• Shorten the AV delay maximally to capture more ventricular beats before intrinsic conduction occurs during rapid AF 1

• Consider enabling device-based fusion pacing features (where RV sense triggers LV pacing), though this should not substitute for definitive rate control 1

Step 3: Definitive Intervention - AV Nodal Ablation

AV nodal ablation is indicated when pharmacologic therapies fail to achieve >95% BiV pacing in permanent AF. 1 This patient has already failed antiarrhythmic therapy, making AV nodal ablation the appropriate next step.

Evidence supporting this approach: 1

• Gasparini et al. demonstrated that CRT patients in permanent AF only achieved improvement in LV function and functional capacity when AV junction ablation was performed 1

• AV junction ablation reduces inappropriate ICD interventions 1

• Guidelines recommend AV junction ablation (or pulmonary vein isolation if indicated) when incomplete (<90-95%) BiV pacing persists despite medical therapy 1

Step 4: Address PVC Burden

After ensuring complete BiV pacing through AV nodal ablation, reassess PVC burden: 1

• Obtain 24-hour Holter monitoring to quantify PVC burden and morphology, as device counters may not detect all QRS-fused beats 1

• If PVCs remain frequent enough to reduce BiV pacing percentage, consider catheter ablation of PVCs as a secondary intervention 1

Additional Optimization Measures

Device Programming Refinements

• Consider VV interval optimization (interventricular timing) to maximize hemodynamic benefit, particularly given the LBBB substrate 1

• Assess for rate-adaptive AV optimization to ensure persistent BiV pacing at higher heart rates if the patient has any chronotropic response 1

• Verify absence of phrenic nerve stimulation at maximal LV output to ensure programming flexibility 1

Diagnostic Workup

• 12-lead ECG to confirm BiV-paced QRS morphology and rule out LV lead displacement (look for loss of negative QRS in V1) 1

• Echocardiography to assess for reverse remodeling and evaluate mitral regurgitation 1

• Laboratory assessment including NT-proBNP to track response to optimization 1

Medical Therapy Optimization

Continue guideline-directed medical therapy (GDMT) for heart failure, as CRT efficacy depends on concurrent optimal medical management 1

Critical Pitfalls to Avoid

• Do not rely solely on device-based fusion pacing features as an alternative to AV nodal ablation in permanent AF with inadequate BiV pacing 1

• Do not accept <95% BiV pacing as adequate in this patient, as observational data consistently show worse outcomes with lower BiV pacing percentages 1

• Do not delay AV nodal ablation once pharmacologic rate control has demonstrably failed, as this prolongs suboptimal CRT delivery 1

• Ensure warfarin is appropriately managed perioperatively for AV nodal ablation procedure

Expected Outcomes

Following AV nodal ablation and achievement of 100% BiV pacing, this patient should experience: 1

• Improved left ventricular function
• Enhanced functional capacity
• Reduced heart failure hospitalizations
• Decreased inappropriate ICD therapies

The combination of CRT-D with complete BiV pacing through AV nodal ablation represents the most evidence-based approach to optimize outcomes in this complex patient with multiple comorbidities including post-TAVR status and nonischemic cardiomyopathy.