Reoperative mitral valve surgery is conventionally performed via resternotomy, which is associated with higher morbidity and mortality compared to primary surgery. Indications for mitral valve reintervention are typically linked to degeneration or complications of previous prostheses (e.g., endocarditis, thrombosis), failure of previous repairs, or progression of native mitral valve disease that did not warrant surgery during the initial treatment of cardiac disease. New mitral interventions can be challenging due to interference with previous surgical techniques (e.g., aortic prostheses, coronary grafts). To avoid an analogous route to the original intervention and reduce the risk of injury to the right heart chambers, the right thoracotomy approach was traditionally described as an alternative to resternotomy. This technique limits the interaction of pericardial adhesions with the procedure, as these adhesions are often more robust anteriorly. The miniaturization of this approach through peripheral cannulation, videothoracoscopy, and specialized surgical tools via ports has allowed the development of the minimally invasive approach as an alternative to the conventional technique. While this approach can be used for initial mitral valve surgery, it is technically advantageous in reoperative settings by combining the benefits of thoracotomy and minimized tissue trauma.

The Dutch school includes pioneering centers with extensive experience in minimally invasive mitral valve surgery. This study presents findings from their national registry, focusing on patients who underwent isolated reoperative mitral valve surgery between 2013 and 2018. A total of 290 patients, initially treated through median sternotomy, were classified based on whether they underwent resternotomy (205 patients) or minimally invasive surgery (85 patients). Of these, 158 patients (54%) had previously undergone mitral surgery. Valve intervention consisted of repair in 59 cases (28.8%) and prosthetic replacement in 144 (70.2%), with no differences between groups. Perioperative variables were adjusted using propensity score analysis to achieve comparability between groups. However, patients who underwent resternotomy were significantly younger (66 vs. 70 years), had lower rates of previous coronary revascularization (36.1% vs. 49%) or mitral surgery (22.9% vs. 42%), and underwent tricuspid valve repair at a higher rate (33.2% vs. 12%).

No significant differences in 30-day mortality were observed between groups (3.4% for minimally invasive vs. 2% for resternotomy). Perioperative morbidity was also comparable, with similar postoperative stays (7 days), rates of cerebrovascular accident (1%), renal failure (4-6%), and surgical reintervention due to bleeding (5% for resternotomy and 10% for minimally invasive approach). Only the incidence of postoperative atrial fibrillation differed, favoring the minimally invasive approach (21% vs. 41%), which may be attributed to reduced manipulation and lower inflammatory response within the pericardial cavity. Five-year survival was 86.3% in the resternotomy group and 89.4% in the minimally invasive group, with no statistically significant differences. Multivariable analysis showed no association between surgical approach and mid-term mortality.

COMMENTARY:

Mitral valve reoperative surgery outcomes in Dutch centers align closely with results in our own context, with similar repair rates and perioperative morbidity and mortality. The authors suggest that outcomes, particularly in terms of survival, might have been better if smaller centers with less repair experience had been excluded, as repair procedures can enhance survival outcomes in mitral valve surgery.

The study concludes that there were no significant differences in outcomes related to the chosen surgical approach, a finding consistent across numerous comparative studies of minimally invasive and conventional approaches. Differences in secondary outcomes did not translate to clinically relevant outcomes like survival or major complications. Despite reduced tissue trauma, once the learning curve for both techniques is surpassed, they become equivalent in expert hands, as extracorporeal circulation remains the primary factor affecting patient physiology. Various transcatheter procedures are currently under development to find their therapeutic niche within the spectrum of mitral valve disease. In the future, these new tools will likely play a central role, enabling truly minimally invasive correction of mitral valve disease, especially in high-risk surgical patients who have undergone prior cardiac surgery.

REFERENCE:

Olsthoorn JR, Heuts S, Houterman S, Maessen JG, Sardari Nia P; Cardiothoracic Surgery Registration Committee of the Netherlands Heart Registration. Minimally invasive approach compared to resternotomy for mitral valve surgery in patients with prior cardiac surgery: retrospective multicentre study based on the Netherl Eur J Cardiothorac Surg. 2022 Oct 4;62(5). doi: 10.1093/ejcts/ezac420.