Aortic screening is mandatory in minimally invasive valve surgery

In this issue of the journal, Nakamura et al. [1] investigated the impact of preoperative angio-CT scan for the planning of perfusion strategies in minimally invasive valve surgery (MIVS). Basically the authors used axillary artery cannulation in the case of thrombosis or calcification in the thoraco-abdominal aorta/iliac arteries and femoral cannulation in all the other cases. With this approach, they reported excellent results with no overall mortality and very low rate of complications. Specifically, they observed just 2 cases of perioperative stroke in the axillary cannulation group (2.1%) while the femoral artery group had no neurological complications. In addition to this, the authors investigated with pre- and post-MRI the incidence of asymptomatic brain injury, showing a significant higher incidence of this silent complication in the axillary artery group (26% vs 15%, P = 0.03). Considering that retrograde perfusion has been associated with worse neurological outcomes during MIVS when compared with antegrade perfusion, this result confirms the effectiveness of their policy of aortic screening. About 10 years ago, an analysis from the Society of Thoracic Surgeons database and a consensus statement from the International Society for Minimally Invasive Cardiothoracic Surgery showed a 1.96- and 1.79-fold increase in the risk of stroke with less-invasive mitral valve procedures, when compared with standard sternotomy operations [2, 3]. Although both studies had numerous confounding factors [4], these 2 papers raised concerns in the surgical community about a possible association between peripheral cannulation and neurological outcomes in MIVS. These concerns were increased by a series of papers from the New York University group, showing that the use of retrograde perfusion in patients with high-risk comorbidities undergoing MIVS [5, 6] was a significant risk factor for neurologic complications. Our group in Massa has investigated the same issue, reporting identical results [7, 8]. Interestingly, both our group and the NYU group found the association between retrograde perfusion and stroke particularly strong in older patients, whereas it became insignificant when analysing patients younger than 70 years old. These observations suggest that the common mechanism in all these papers reporting stroke risk is the burden of atherosclerosis of the study population. Indeed, it is well known that the prevalence of occult thoraco-abdominal aortic atherosclerosis increases with age in both sexes, and it is widely prevalent by the middle of the seventh decade of life [9]. Similar to what reported by Nakamura et al., in 2013 a study from the Cleveland Clinic [10] on 141 patients screened with angio-CT for robotic mitral procedure, found that 1 in 5 patients had significant subclinical aorto-iliac atherosclerosis. Taking this in mind, it would seem that a strategy of aortic screening could help to recognize a 20% of patients at increased risk of stroke with retrograde perfusion. Nevertheless, the use of MDCT angiography has to be weighed against some drawbacks such as nephrotoxicity, radiation exposure and costs. For this reason, we have developed an institutional protocol to screen the aorta of patients scheduled for MIVS. We use preoperative echographic examination of the iliac-femoral axis followed by the evaluation of the aortic arch and thoracic aorta with intraoperative transoesophageal echocardiographic scans in low atherosclerotic risk patients, reserving angio-CT screening for those patients with a clear atherosclerotic burden disease (age >70 or risk factors). If atherosclerotic aortic disease is diagnosticated, antegrade perfusion (direct ascending aorta or axillary artery) is chosen. In an era where surgical population is becoming older, strategies for stroke prevention are essentials and preoperative aortic screening is a key element. The study of Nakamura represents a step forward to understand and reduce the incidence of neurologic complications in MIVS.