Several reports have described the performance of bench mitral repair when MR was identified in the donor heart prior to transplantation [1,2,3,4,5,6,7,8,9]. Prieto et al. [5] described bench repair on donor hearts without significant preoperative MR but with mitral annular dilation. However, the occurrence of severe MR following aortic declamping has been rarely reported in a normal donor heart. In this case, the preoperative cardiac function of the donor heart was evaluated as normal with trivial MR, and there was no evidence suggestive of coronary artery disease or significant myocardial injury. Additionally, there was no abnormality of the mitral valve structure, including the annulus and subvalvular apparatus.

Functional severe MR can reportedly occur after declamping during open heart surgeries other than mitral valve procedures, such as coronary artery bypass grafting and aortic valve replacement, even when cardiac function is normal [10]. One possible cause is dyssynchrony due to right ventricular pacing. In some cases, however, reestablishment of cardiopulmonary bypass and additional concomitant mitral valve surgery are necessary when severe MR remains. This suggests that impaired myocardial function following cardiopulmonary bypass might contribute to diastolic dysfunction. In the current case, although the postoperative CK-MB level was within the normal range, indicating no myocardial necrosis, the extended cold ischemia time of 3.5 h suggested that myocardial stunning due to prolonged ischemia was the most likely cause of functional mitral regurgitation. The widespread adoption of continuous perfusion systems could help maintain myocardial protection even during anticipated prolonged ischemic times, potentially preventing cases such as the present case. And other possible reason for the lack of detection of MR in the preoperative evaluation is the decrease in LV afterload due to decreased sympathetic activity after brain death, resulting in underestimation of the MR.

Conventional approaches such as transseptal or right-sided left atrial approaches are commonly used for mitral valve surgery during the post-transplant period [11, 12]. However, in this case, the approach was achieved by detaching the inferior vena cava anastomosis and partially left atrial suturing. This approach allowed for rapid and good visualization by simply cutting the sutures, and it provided the advantage of being able to promptly address any interference between the left atrial suture line and the mitral valve. Despite the need for re-anastomosis, this approach was considered useful. The benefits of a right-sided left atrial incision or a transseptal approach are that the sutures do not need to be dissected, and surgeons are already familiar with the usual method. However, a disadvantage is that if there is distortion of the geometry of the mitral annulus caused by left atrial anastomosis, it cannot be released. The current approach, which involves dissecting the IVC anastomosis, has the advantage of providing a clear view, even in cases where the left atrium is not enlarged, as in this case. This approach also allows for simultaneous repair of the distortion of the mitral annulus caused by atrial anastomosis. Additionally, the right-sided left atrial incision or transseptal approach can be preserved for future use. On the other hand, disadvantages include the large number of suture points and unfamiliar approach method in routine surgery.

While heart transplantation is an established treatment for severe heart failure, the shortage of donor hearts is a major concern owing to the increasing number of patients with heart failure. One solution is to broaden the criteria for accepting donor hearts [13, 14]. Bench valve repair [1,2,3,4,5,6,7,8,9] may be a preferable option when simple valvular disease is identified preoperatively, as reported in the literature. However, this often requires the use of prosthetic valves or rings, which should be minimized due to the high risk of infection from post-implantation immunosuppressive drugs. In cases where preoperative valvular disease is not obvious, as in our case, it may be beneficial to proceed with transplantation and assessment of valvular disease after declamping. This simultaneous intervention for valvular disease in the donor heart could potentially expand the donor eligibility criteria and alleviate donor shortages.

Even if the preoperative donor heart evaluation is normal and MR is not observed, attention should be paid to the occurrence of functional MR after declamping, if the cold ischemic time is prolonged. Although spontaneous improvement is possible, MAP may be a good method of MR control. In addition, it may be possible to secure a good view of the mitral valve in the normal-diameter left atrium by removing the IVC and part of the left atrial anastomosis.