What is the clinical evidence from this study?

Study design: Other. Population: Ventricular tachycardia ablation model (n=11). Intervention: Bipolar epicardial-to-endocardial ablation vs. Unipolar epicardial ablation. Primary outcome: Lesion depth from the epicardial surface (mm) (p=<0.001).

December 14, 2011Open Access

Epicardial Ablation With Irrigated Electrodes

Q: What are the key findings of this study?

Bipolar epicardial-to-endocardial ablation created significantly deeper lesions than unipolar epicardial ablation (10.6 mm vs 7.5 mm, P<0.001) and produced transmural lesions in 46% of cases compared to 0%.

Key Result

Bipolar epicardial-to-endocardial ablation created significantly deeper lesions than unipolar epicardial ablation (10.6 mm vs 7.5 mm, P<0.001) and produced transmural lesions in 46% of cases compared to 0%.

Structured PICO

Does bipolar epicardial ablation improve lesion depth compared to unipolar ablation in excised pig hearts?

Population

11 excised pig hearts superfused with saline

Intervention

Bipolar ablation (25 or 30 W for 120 s) between a 4-mm saline-irrigated-tip (20 ml/min) electrode on the LV epicardium and an opposing 10-mm non-irrigated-tip electrode on the LV endocardium (n = 38 lesions)

Comparator

Unipolar ablation (25 or 30 W for 120 s) between the LV epicardial saline-irrigated electrode and an indifferent electrode (n = 33 lesions)

Outcome

Lesion size (width and depth)surrogate

Bipolar ablation of the LV free wall creates significantly deeper epicardial lesions than unipolar ablation in an ex vivo porcine model.

Main Result

Absolute Event Rate: 10.6% vs 7.5%

p-value: p=<0.001

Limitations

The setting of this in vitro experiment was different from the actual clinical setting.
A constant 2 L/min of saline flow does not perfectly mimic the blood flow in the human LV (not pulsatile, different specific heat capacity and density).
The catheters were placed and held manually on the LV epicardium, and the contact force of the catheter-tip was not measured.
It may be difficult to exactly and continuously place a catheter on the LV epicardium and place the other catheter on the LV endocardium opposite the epicardial catheter in the beating human heart.

Abstract

BACKGROUND: Ablation of ventricular tachycardia originating from the left ventricular (LV) epicardium is often limited by the radiofrequency power delivery. We compared the effect of bipolar vs. unipolar epicardial ablation on lesion size. METHODS AND RESULTS: Eleven excised pig hearts were superfused with saline (2 L/min). Unipolar ablation (25 or 30 W for 120 s) was performed between the LV epicardial saline-irrigated electrode and an indifferent electrode (n = 33 lesions). Bipolar ablation (25 or 30 W for 120 s) was performed between a 4-mm saline-irrigated-tip (20 ml/min) electrode on the LV epicardium and an opposing 10-mm non-irrigated-tip electrode on the LV endocardium (n = 38 lesions). Wall thickness did not differ between experiments (15.4 ± 2.4 vs. 15.3 ± 2.1 mm). Impedance was lower at the beginning and end of unipolar ablation than at the beginning and end of bipolar ablation (163.2 ± 20.3Ω and 109.9 ± 16.0Ω vs. 194.6 ± 23.3Ω and 127.1 ± 16.4Ω, respectively) (P<0.001). Epicardial lesion width did not differ between unipolar and bipolar ablation (10.1 ± 2.7 vs. 10.2 ± 2.4 mm), but lesion depth was greater with bipolar ablation (10.6 ± 2.7 vs. 7.5 ± 1.0 mm) (P<0.001). Unipolar ablation produced no transmural lesion, but bipolar ablation produced 15 (46%) (P<0.001). Steam pop occurred in 11 (29%) and 3 (9%) cases, respectively (P = 0.036). CONCLUSIONS: Bipolar ablation of the LV free wall is highly effective at creating an appropriately deep epicardial lesion.

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