Use of HASTE MRI in the evaluation of acute injury to left atrial wall caused by RF ablation

Introduction

Atrial fibrillation (AF) is the most common cardiac rhythm disturbance affecting more than 2 million people in the United States. Pulmonary vein isolation (PVI) procedure using RF ablation has emerged as a new promising treatment of AF. Reported procedure success rates vary significantly with recurrences ranging from 40-86%. With introduction of EP-MRI suites, patients may be re-ablated immediately after assessment of the extent of LA wall injury, if necessary. Late gadolinium enhancement (LGE) [1, 2] and double inversion recovery (DIR) prepared T2-weighted (T2w) fast/turbo spin echo (FSE/TSE) [3–5] were proposed to evaluate acute LA wall injury. The main disadvantages of these sequences are a long scan time and a strong dependence of image quality on heart rate regularity.

Purpose

Develop a fast imaging technique for assessment of acute injury in patients undergoing RF ablation treatment of atrial fibrillation (AF).

Methods

HASTE is a single shot imaging technique with strong T2-weighting. These features of the pulse sequence make it a good candidate for assessment of the extent of LA wall injury immediately after ablation. Twenty-five AF patients underwent pulmonary vein isolation and debulking of the septal and posterior walls. All patients were imaged pre- and immediately post ablation using a 3 Tesla MRI scanner (Verio, Siemens Healthcare). Acute injury was assessed using a DIR-HASTE, DIR-TSE, and LGE sequence coving the entire LA. HASTE parameters were: TE = 73 ms, TR = one respiratory cycle, fat suppression using spectral adiabatic inversion recovery (SPAIR), in-plane resolution of 1.25 × 1.98 mm, slice thickness of 5 mm, GRAPPA with R = 2 and 34 reference lines. DIR-TSE parameters were: TE = 83 ms, TR = 2RR, fat suppression using SPAIR, in-plane resolution of 1.25 × 1.25 mm, and slice thickness of 4 mm. All sequences were respiratory navigated, ECG gated with data acquisition during LA diastole.

Results

Typical DIR-TSE and DIR-HASTE are shown in Fig. 1. Both sequences visualize post-ablation edema clearly. Typical scan time for HASTE sequence was about 2 minutes whereas scan time for DIR-TSE exceeded 6 minutes. Image quality for DIR-TSE was strongly dependent on regularity of heart rate while HASTE sequence gave good images regardless.

Figure 1

Visualization of acute injury of LA wall caused by RF ablation. Top row: DIR-HASTE. Bottom row: DIR-TSE

Conclusion

The proposed HASTE sequence enables a good visualization of injury to left atrial wall immediately post-ablation.