Author + information
- Francesco Nappi, MD∗ (, )
- Cristiano Spadaccio, MD, PhD and
- Massimiliano Fraldi, PhD
- ↵∗Cardiac Surgery Centre Cardiologique du Nord de Saint-Denis, 36 Rue des Moulins Gémeaux, Saint-Denis 93200, France
We are very thankful to Dr. Padala for his comments and congratulations.
We would like, in turn, to express our gratitude to his own group for all the pioneering pre-clinical and clinical works on this argument that fostered our interest and stimulated our reflection on the significance of papillary muscle (PM) and subvalvular apparatus geometry in our clinical practice.
The contradictory results recently published on mitral repair in ischemic mitral regurgitation (IMR) pose a veil of uncertainty on the future of this procedure (1). However, sharing the thoughts of Dr. Padala’s group, we believe that the apparently neglected importance of the subvalvular apparatus in this context might be the cause of the dark light shed on mitral reparative surgery. We firmly believe in the role of the PM for the maintenance of mitral geometry, and we think a comprehensive approach, including not only the annular but also the subvalvular part of the mitral apparatus, would be the future “direction of travel.” Work done by Padala and colleagues, as well as our group, might prove this concept and potentially lead to reconsideration of the major trials published on the argument that demand another type of surgical comparison—a “complete mitral repair” (i.e., involving both the valvular and subvalvular apparatuses) versus chordal-sparing mitral replacement.
In this context, the advancement in cardiac imaging would lend a hand to a novel approach in the pre-operative evaluation of IMR patients, which would therefore include the consideration of a number of different parameters, such as the interpapillary distance, the tenting area or volume, the symmetry of mitral tethering, the regional left ventricular wall function, and so on. In this framework, we also think that PM anatomy and morphology deserve a more specific consideration.
Pioneering work in mitral anatomy showed a range of morphological diversity of PM anatomy and led to an anatomical classification (2) with important implications in IMR surgery (3). Also, the uneven coronary distribution and the features of PM microcirculation (4) imbricate this anatomical variability, justifying the different characteristics and the sensibility of ischemic injury of PM in the course of IMR. Clearly, these determinants of PM also sustain IMR pathogenesis and progression, and therefore, require rigorous consideration when evaluating the role of surgery in this context. A “reductionist” approach to IMR repair is not suitable in these conditions, and for this reason, we believe that the development of a mathematical model, including the different parameters involved in this framework, would be the answer to solve the issues of IMR.
We thus developed a biomechanical model that elucidated the key interactions between closing and tethering forces, by taking into account geometry of valvular and subvalvular apparatuses. Leaflets are modeled as elastic beams, with joints representing the mitral annulus structure and the “chorda tendinea” as a tie rod exerting pulling forces in the subvalvular apparatus. Geometrical parameters are selected to be identified with those actually related to the MR pathological state to the surgical choices to be taken. Tenting height (connected to tenting area), post-operative interpapillary distance, and displacement resulting from PM approximation (PMA) are therefore all combined through equilibrium, constitutive, and kinematical equations, with both tendon forces and the mitral valve opening used for estimating force reduction and valve-support structure remodeling (Figure 1). It is believed that this could be a first step toward a biomechanical geometry–oriented modeling of PMA, which might pave the way for decisional algorithms that support surgical choices in the related surgical procedure.
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2016 American College of Cardiology Foundation