Preoperative determination of the loop length for mitral valve repair using 4-dimensional computed tomography

K. Tsuda¹, N. Washiyama¹, D. Takahashi¹, M. Hirano², Y. Ohashi¹, K. Natsume¹, Y. Takeuchi¹, N. Shiiya^1
1Hamamatsu University school of Medicine, Hamamatsu, Shizuoka ²Hamamatsu University School of Medicine, Hamamatsu city, Shizuoka

Purpose: The loop technique has been used for mitral valve repair to avoid knot-tying of the slippery ePTFE neochordae. The loop bundles have been created during cardiac arrest after chordal length measurements. We determined the loop length preoperatively using 4-dimensional computed tomography. We report the measurement method and preliminary outcomes.

Methods: Using a medical image post-processor (Synapse Vincent, Fujifilm, Tokyo), the commissural and long-axis views were created from the DICOM data in late systole. The prolapsed leaflet and papillary muscle morphology were assessed. We marked the tip of the papillary muscle and the portion of the prolapsed leaflet edge to which the loops would be secured, and the edge of the opposite non-prolapsing leaflet corresponding to the marked point of the prolapsed leaflet. Then the distance between the marked points (papillary muscle tip and the edge of the opposite leaflet) was measured. The loop length was set at this distance. The loop bundles were created immediately before surgery. Reference measurements were also made in the operative field to confirm consistency. This technique was used in 25 patients who underwent mitral valve repair with the loop technique since April 2021.

Results: The patient age ranged from 36 to 79 (median 59) years. 16 were men. Operations were performed through a right mini-thoracotomy in 16 and through a sternotomy in 7. A total of 32 loop bundles were created; in 7 cases loop bundles were fixed to both anterior and posterior papillary muscles. There were 11 posterior, 10 anterior, and 4 bi-leaflet prolapse. The loop length was set at 16-26 mm (median 20 mm). In 23 cases, the loop bundles were used successfully. Operation time was 176 to 379 (median 226) minutes and cross-clamp time was 67 to 170 (median 90) minutes in these 23. Among the remaining 2 cases, the loop length was changed from 18 mm to 21mm in one, based on the intraoperative measurement, because the tip of the papillary muscle did not seem strong enough and the loop bundle was secured to the papillary muscle belly. In the other case, surgical procedure was changed to the sliding leaflet technique because of systolic anterior movement. Postoperative echocardiography revealed no regurgitation in 7, trivial regurgitation in 14, and mild regurgitation in 4.

Conclusion: Loop length determination using preoperative 4-dimensional computed tomography is feasible. Use of loop bundles with predetermined loop length may contribute to improve the reproducibility of repair and to shorten the cross-clamp time.

Identify the source of the funding for this research project: Not to declear.