Chronic RV Lead Impedance of 160 Ohms
A chronic right ventricular lead impedance of 160 ohms is abnormally low and indicates a likely insulation breach or lead conductor problem that requires urgent evaluation and likely lead replacement.
Understanding Normal RV Lead Impedance Values
Normal pacing lead impedance typically ranges from 400-1200 ohms for chronic leads. 1, 2 Your measurement of 160 ohms falls well below this range, representing a significant deviation from expected values.
Clinical Significance of Low Impedance
Low impedance (<200 ohms) indicates:
- Insulation breach - The most common cause, where the lead insulation has broken down, allowing current to leak into surrounding tissue
- Lead conductor exposure - Direct contact between the conductor and body fluids
- Increased current drain - This will deplete the device battery faster
- Potential for pacing failure - The electrical circuit is compromised
What This Means for Device Function
Immediate Concerns:
- Accelerated battery depletion - The low resistance pathway causes excessive current drain from the generator
- Loss of effective pacing - Current may dissipate before reaching the myocardium
- Potential sensing abnormalities - Though less common with pure insulation defects
Contrast with High Impedance Problems:
Research shows that lead fractures (which cause high impedance >1000 ohms) often present with oversensing and inappropriate shocks. 1, 3, 4 Low impedance problems like yours typically present differently, with pacing ineffectiveness rather than sensing noise.
Recommended Actions
Immediate steps:
- Perform comprehensive device interrogation - Check pacing thresholds, sensing amplitudes, and battery voltage 3, 4
- Obtain chest X-ray - Look for obvious lead damage, though insulation defects may not be visible
- Test pacing capture at multiple outputs - Determine if effective pacing is still achievable
- Assess patient's pacing dependency - Critical for determining urgency of intervention
If pacing-dependent:
- Consider urgent lead revision or replacement 1
- Temporary external pacing may be needed if capture is lost
- Do not delay intervention in symptomatic patients
If not pacing-dependent:
- Schedule elective lead replacement within days to weeks
- Continue close monitoring with frequent device checks
- Watch for symptoms of pacing failure (syncope, fatigue, dyspnea)
Monitoring Considerations
Remote monitoring systems can detect lead problems early, though studies show that impedance changes alone miss up to 76% of lead failures, with arrhythmic events being more sensitive indicators. 5 However, your dramatically low impedance of 160 ohms is unambiguous and requires action regardless of other parameters.
Key monitoring parameters:
- Daily impedance trending if remote monitoring available 3, 4
- Pacing threshold changes
- Battery voltage decline rate
- Any new arrhythmic events or oversensing
Common Pitfalls to Avoid
- Do not wait for symptoms - Lead failure with low impedance can progress rapidly
- Do not rely solely on automated alerts - Many device alerts are set at thresholds (e.g., <200 or >1000 ohms) that may not trigger at 160 ohms depending on programming 2
- Do not assume the lead is functional - Even if pacing appears to work, the compromised circuit will fail
- Do not delay in pacing-dependent patients - This is a time-sensitive issue
Bottom Line
An impedance of 160 ohms is not a borderline finding requiring observation—it represents established lead failure requiring intervention. The only clinical decision is the timing: urgent (if pacing-dependent or symptomatic) versus semi-urgent (if not pacing-dependent). Lead replacement or revision should be planned immediately. 1, 3, 4