Impact of Catheter-Tissue Contact Force on Lesion Size During Right Ventricular Outflow Tract Ablation in a Swine Model

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Impact of Catheter-Tissue Contact Force on Lesion Size During Right Ventricular Outflow Tract Ablation in a Swine Model

Radiofrequency catheter ablation (RFCA) is a go-to treatment for people with idiopathic ventricular arrhythmias (VAs)—abnormal heart rhythms like frequent premature ventricular contractions or ventricular tachycardia. The most common spot for these arrhythmias? The right ventricular outflow tract (RVOT), a tube-like structure that carries blood from the right ventricle to the lungs. But here’s the catch: 7–20% of RVOT ablation procedures fail or lead to recurrences. Why? One big factor is how hard the ablation catheter presses against the heart tissue—called catheter-tissue contact force (CF).

While CF is known to affect how large the ablation lesion (damaged tissue that stops abnormal rhythms) grows, doctors still aren’t sure what range is safe and effective for RVOT ablation. To find out, researchers from Guilin People’s Hospital and The First Affiliated Hospital of Guangxi Medical University tested CF in a swine model—pigs are ideal because their hearts are similar in size and function to human hearts.

Why Contact Force Matters

When you ablate heart tissue, the goal is to create a lesion big enough to block faulty electrical signals—but not so big that it causes complications like steam pops (sudden bursts of gas that can tear tissue) or perforation. CF is key here: too little force means a small, ineffective lesion; too much means higher risk of harm.

Before CF-sensing catheters existed, doctors guessed at contact using indirect clues (like voltage readings or catheter movement on X-ray). But these aren’t reliable. Direct CF measurement—using tools like the ThermoCool SmartTouch catheter—gives real-time data, but its role in RVOT ablation was untested until this study.

How the Study Worked

The team used 12 Guangxi Bama miniature pigs (40–50 kg, similar to adult human heart size). They divided the pigs into four groups based on CF:

  • Group A: 3–9 g (low force)
  • Group B: 10–19 g (medium-low)
  • Group C: 20–29 g (medium-high)
  • Group D: 30–39 g (high force)

Using the CARTO 3 3D mapping system, they guided a SmartTouch catheter into the RVOT. They ablated three spots in the RVOT’s free wall (thin outer layer) and septum (thick inner wall) for 30 seconds at 30 watts, with saline irrigation (17 mL/min) to prevent overheating.

After the procedure, they measured lesion size (depth, diameter, volume) and checked for complications (steam pops, transmural lesions—damage that goes all the way through the heart wall).

Key Findings

The results, published in the Chinese Medical Journal, were clear:

  1. CF directly affects lesion size: The harder the catheter pressed, the bigger the lesion—especially in the septum. For the free wall, lesion depth and volume stopped growing once CF hit 20–29 g (because the wall is thin, the lesion became transmural and couldn’t get deeper). In the thicker septum, lesions kept growing with more force.

  2. Complications rise with higher CF: Steam pops—dangerous because they can cause perforation—only happened when CF exceeded 20 g. The average CF for steam pops was ~31 g (no difference between free wall and septum).

  3. Transmural lesions depend on location: In the thin free wall, transmural lesions (which can stop arrhythmias) appeared when CF was >10 g. But in the thicker septum, no transmural lesions formed—even at 39 g.

  4. Indirect clues aren’t reliable: Voltage readings and impedance (electrical resistance) weakly correlated with CF, but they overlapped too much to be useful for doctors in real time.

What This Means for Patients and Clinicians

The biggest takeaway? Keeping CF between 3–10 g is safe and effective for RVOT ablation. Here’s why:

  • This range creates lesions big enough to stop arrhythmias without risking steam pops or perforation.
  • For the septum (where arrhythmias can hide deeper), doctors might need to go up to 20 g—but never over 20 g (that’s when complications spike).

Compare this to previous studies: Most research on CF focused on atrial ablation (for AFib), where transmural lesions are needed. But RVOT arrhythmias usually come from just under the surface—so transmural lesions aren’t necessary, and lower CF is safer.

Limitations to Consider

Like all animal studies, this one has caveats:

  • Pig hearts aren’t identical to human hearts—anatomical differences might affect results.
  • The sample size was small (12 pigs, 72 lesions).
  • The team didn’t use advanced imaging (like echocardiography) to confirm catheter position, which could affect accuracy.
  • We still don’t know the exact safe CF range for humans—more clinical trials are needed.

Conclusion

CF is a critical factor in RVOT ablation: it predicts lesion size and complication risk. For now, the evidence suggests keeping CF between 3–10 g balances effectiveness and safety. This is a big win for patients with RVOT arrhythmias—doctors can use CF-sensing catheters to make ablation more reliable and less risky.

Original Study Details
Jing-Bo Jiang, Jin-Yi Li, Zhi-Yuan Jiang, et al. Impact of catheter-tissue contact force on lesion size during right ventricular outflow tract ablation in a swine model. Chinese Medical Journal 2020;133(14):1680–1687. doi:10.1097/CM9.0000000000000859

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