Aortic valve hydrodynamics: considerations on the absence of sinuses of Valsalva.

BACKGROUND AND AIM OF THE STUDY: The study aim was to compare the hydrodynamics of the Carpentier-Edwards Magna 21 (CEM) and St. Jude Medical Biocor-Epic-Supra 21 (SJME) valves at increasing stroke volume and pulse rate in two different aortic conduits, namely straight and with sinuses of Valsalva present. METHODS: Both valve types were tested in the aortic chamber of the Sheffield pulse duplicator, at rates of 70, 80 and 90 beats/min, and stroke volumes of 50 and 60 ml. The systolic and diastolic performances were each recorded. The leaflet coaptation time, ventricle isovolumetric time and maximum instantaneous flow rate were also recorded. RESULTS: Regardless of the aortic conduit, CEM valves showed a significantly lower gradient than SJME valves (p < 0.05), and a significantly larger effective orifice area (EOA) (p < 0.05); the latter parameter was unaffected for both valves, at an increasing pulse rate (p > 0.05). The maximum transvalvular flow velocity was significantly higher in the straight conduit for both valves (p < 0.05). With regards to diastole, the SJME valve showed the lowest regurgitant volume (p < 0.05). The leaflet coaptation time was significantly shorter for the SJME valve than for the CEM valve (p < 0.05), but when tested in a straight conduit it was shortened significantly for both valves (p < 0.05). CONCLUSION: An absence of the sinuses of Valsalva may modify the diastolic and systolic behaviors of the tissue valve leaflets by reducing the time required for leaflet coaptation, and increasing the valve closing volume and maximum transvalvular flow velocity. It is speculated that these hydrodynamic changes may increase the working stress on the valve tissue, leading to possible premature structural valve deterioration.

The changing hydrodynamic performance of the decellularized intact porcine aortic root: considerations on in-vitro testing.

BACKGROUND AND AIM OF THE STUDY: The most effective method for decellularization of the intact porcine aortic root remains controversial. Additionally, the hydrodynamic effect that such treatment may have on aortic roots has never been previously investigated. The study aim was to compare the in-vitro hydrodynamic performances of intact porcine aortic roots, both before and after decellularization treatment. METHODS: Fifteen fresh porcine aortic roots were tested in the aortic chamber of the Sheffield pulse duplicator (SPD). For study purposes, the roots were first sutured to a silicone aortic root and then hydrodynamically tested. After in-vitro testing, the fresh porcine aortic roots, while still fixed within the silicone root, were decellularized according to various protocols (TRI-COL, TRI-DOC, sodium dodecyl sulfate (SDS) 0.03%, and SDS 0.1%). After decellularization, the valve roots were re-tested, adopting identical testing conditions. Forward flow pressure drop, closing leakage volumes, effective orifice area (EOA), and stroke work loss were each monitored. Three roots, used as a control group, were tested in identical fashion before and after storage (without decellularization) for comparative purposes. RESULTS: The TRI-COL- and TRI-DOC-treated porcine aortic roots showed significantly lower transvalvular gradients, lower stroke work loss, lower valve resistance, and higher EOA than fresh intact porcine roots. In contrast, SDS 0.1%-treated porcine aortic roots showed opposing results, with the transvalvular gradients, stroke work loss and valve resistance each higher, and the EOA lower, than pre-treatment values. SDS 0.03% treatment had no significant effect on the hydrodynamic performance. After decellularization in all treatment groups, the diastolic parameters, total regurgitant volume and valve closing volume were each non-significantly increased. The aortic roots used as a control group showed similar results before and after storage. CONCLUSION: Based on these results using the SPD, all treatments except for SDS 0.03% modified the systolic and diastolic functions of intact porcine aortic roots.

Nitinol flexigrip sternal closure system and standard sternal steel wiring: insight from a matched comparative analysis.

OBJECTIVE: We sought to assess the efficiency of two different sternal closure techniques in preventing sternal wound instability in high-risk patients. MATERIALS AND METHODS: Between January 2009 and February 2012, 2068 consecutive cardiac patients were prospectively collected in our database. The 561 patients in whom the thermoreactive nitilium clips (Flexigrip) have been used (group A) were matched 1 : 1 with 561 patients who received a standard parasternal wiring technique (group B) on 10 available risk factors known to affect sternal wound healing (age, age >75 years, sex, diabetes mellitus, cardiac procedure, obesity, re-intervention, cross-clamp, and total operative times). The study was completed with a cost analysis. RESULTS: The two groups were well matched, although different for bilateral internal thoracic harvesting, chronic obstructive pulmonary disease, renal insufficiency, and congestive heart failure, which were significantly more frequent in group A. At 30 days of follow-up, the association of wound complication and sternal instability was significantly less frequent in group A versus group B (0.2 versus 1.6%) (P = 0.04). Overall incidence of sternal wound complication was lower in group A (2 versus 3.5%) (P = 0.28). In the presence of wound infection, a sternal wound instability was never observed in group A (P = 0.06). Overall costs were €8,701,854 and €9,243,702 in groups A and B, respectively; thus the Flexigrip closure technique offered a €541,848 cost saving. CONCLUSIONS: Flexigrip use in high-risk patients showed a lower incidence of sternal wound instability with no need for sternal re-wiring in any case, even in the presence of wound infection.

Nitinol flexigrip sternal closure system and chest wound infections: insight from a comparative analysis of complications and costs.

BACKGROUND: We sought to assess the efficiency of two different sternal closure techniques in preventing sternal wound complications (SWC). A cost analysis was also considered. METHODS: Between January 2008 and April 2010, 1,644 consecutive cardiac surgery patients who underwent cardiac surgery in our institute were prospectively collected. A total of 1,072 patients received a standard parasternal wiring technique (group A), and 572 patients received a new method of sternal closure based on the use of thermoreactive nitillium clips (Flexigrip; Praesidia SRL, Bologna, Italy [group B]). We investigated, by a propensity matched analysis, whether the use of standard or nitinol clip closure would impact on sternal wound outcome. RESULTS: In all, 464 patients of each group were matched for 17 available risk factors. Overall incidence of SWC was significantly higher in group A (4.1% versus 1.7%; p=0.03). Sternal surgical revision to treat a thoracic instability was required in a significantly higher number of patients in group A (9 patients, 1.9%) and in none of group B (p=0.004). The incidence of sternal instability, secondary to wound infection, was significantly lower in group B (p=0.05). Overall costs were €7,407,296 and €6,896,432 in group A and group B, respectively. Thus, nitinol clip closure technique offered a €510,864 cost saving compared with standard steel wiring technique. CONCLUSIONS: The Flexigrip assured a lower incidence of SWC. The use of the nitinol clip favored an improved sternal closure technique preventing mediastinitis. Additionally, the nitinol clip system proved to be cost effective in cardiac surgery.