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Nappi et al. Vessel Plus 2021;5:40 https://dx.doi.org/10.20517/2574-1209.2021.06 Page 9 of 20

In one study, 1079 patients from 90 centers were randomized and treated with TMViV (n = 857) or TMViR
(n = 222) therapy. The primary endpoint was patient survival, while secondary endpoints were residual MS
(mean gradient ≥ 10 mmHg), residual MR (defined as regurgitation ≥ moderate) and rate of repeat MV
replacement. With a median echocardiographic follow up of 772.5 days, this study found that post-
procedural MS was more common in patients treated with TMViV procedure, while post-procedural MR
was more common in patients treated with TMViR. This analysis reported that residual MS was correlated
with smaller true internal diameter, younger age and larger body mass index, while post-procedural MR was
[38]
correlated only with TMViR procedure .
Surgical therapy: sternotomy or right thoracotomy?
Reoperative mitral valve (MV) procedures are increasingly common and represent over 10% of all MV
operations in the United States. There is no broad consensus regarding the optimal surgical approach. The
decision between a surgical approach via resternotomy or right thoracotomy represents one of the most
important steps of the surgical planning [11,24] [Figures 1 and 2].

Anatomical characteristics, concomitant pathologies, risk scores and type of MV degeneration (mitral repair
failure or prosthesis degeneration) can be useful for the decision between sternotomy and right
thoracotomy. Moreover, recognizing and analyzing the cause and mechanism of primary MV repair failure
with reliable intraoperative and predischarge echocardiography is important to improve the outcome of the
initial MV repair [23,25] [Figure 3].

Regardless of the type of repair failure/prosthesis degeneration, the presence of peripheral artery disease,
high stroke risk, concomitant or previous coronary artery bypass grafting (CABG) or aortic valve surgery
represents one of the first parameters that can guide the choice towards the safest surgical approach.
Thoracic CT can show anatomical characteristics, such as proximity of right ventricle or pericardium to the
sternum or the position of large vessels or graft used for previous CABG, which are useful to identify
patients with high or low risk for intraoperative injury in repeat sternotomy [Figure 2].

A publication from the Division of Cardiac Surgery of the University of Maryland School of Medicine in
[20]
Baltimore shows that repeat sternotomy MV operation can be performed with low perioperative
mortality (4.6%) and low re-entry injury rate (1.5%) and, moreover, that repeat sternotomy MV operation is
not an independent risk factor for operative mortality or morbidity. Furthermore, a recent review of
patients who underwent reoperative MV surgery between 2011 and 2017 at four institution within the
Northwell Health System confirms that reoperative mitral valve surgery via right anterolateral
minithoracotomy, when performed in centers with high experience in minimally invasive surgery, is safe,
reproducible and associated with shorter ventilation times, decreased hospital stay and faster postoperative
recovery. Furthermore, the type of MV reoperation (re-repair or re-replacement) is not affected by the
surgical approach used. These assessments are essential to adopt the safest and most effective surgical
approach for the patient’s benefit; therefore, we propose a flowchart that can guide the choice of the best
surgical approach [Figure 4]. Concomitant tricuspid valve surgery is not important for the decision between
sternotomy and right thoracotomy. As shown in a review performed by the Division of Cardiovascular
[21]
Surgery from Toronto , there are several independent predictors of mortality during redo mitral valve
replacement: renal failure (OR = 3.4), previous stroke/TIA (OR = 2.5), left ventricle dysfunction (FE < 40%;
OR = 1.6), urgent timing (OR = 1.5) and no subvalvular preservation during first surgery (OR = 3.4). These
data show the importance of careful patient selection and meticulous evaluation of the first surgery
[Table 3].