Giovanni Puppini

Comparative finite element model analysis of ascending aortic flow in bicuspid and tricuspid aortic valve.

In bicuspid aortic valve (BAV) disease, the role of genetic and hemodynamic factors influencing ascending aortic pathology is controversial. To test the effect of BAV geometry on ascending aortic flow, a finite element analysis was undertaken. A surface model of aortic root and ascending aorta was obtained from magnetic resonance images of patients with BAV and tricuspid aortic valve using segmentation facilities of the image processing code Vascular Modeling Toolkit (developed at the Mario Negri Institute). Analytical models of bicuspid (antero-posterior [AP], type 1 and latero-lateral, type 2 commissures) and tricuspid orifices were mathematically defined and turned into a volumetric mesh of linear tetrahedra for computational fluid dynamics simulations. Numerical simulations were performed with the finite element code LifeV. Flow velocity fields were assessed for four levels: aortic annulus, sinus of Valsalva, sinotubular junction, and ascending aorta. Comparison of finite element analysis of bicuspid and tricuspid aortic valve showed different blood flow velocity pattern. Flow in bicuspid configurations showed asymmetrical distribution of velocity field toward the convexity of mid-ascending aorta returning symmetrical in distal ascending aorta. On the contrary, tricuspid flow was symmetrical in each aortic segment. Comparing type 1 BAV with type 2 BAV, more pronounced recirculation zones were noticed in the latter. Finally, we found that in both BAV configurations, maximum wall shear stress is highly localized at the convex portion of the mid-ascending aorta level. Comparison between models showed asymmetrical and higher flow velocity in bicuspid models, in particular in the AP configuration. Asymmetry was more pronounced at the aortic level known to be more exposed to aneurysm formation in bicuspid patients. This supports the hypothesis that hemodynamic factors may contribute to ascending aortic pathology in this subset of patients.

Does the tuberous sclerosis complex include intracranial aneurysms? A case report with a review of the literature.

Background. Tuberous sclerosis is a protean, genetically determined disease that may involve any organ or tissue and lead to a great number of symptoms and clinical features. Objective. Diagnosis can be very difficult in cases with incomplete manifestations (formes fruste) lacking the classic signs of the disease. Materials and methods. We report a case fulfilling the diagnostic criteria for tuberous sclerosis (shagreen patches, hypomelanotic macules, renal cysts and angiomyolipomas, and “migration tracts” in the cerebral white matter) in association with a giant intracranial aneurysm, but lacking mental retardation, epilepsy and facial angiofibroma. Results. Fourteen other cases of tuberous sclerosis and intracranial aneurysms, all but one without any clear sign of polycystic kidney disease, were found in the literature. Conclusion. We suggest that vascular dysplasias in general and aneurysms (mainly intracranial) in particular can be added to the other non-primary diagnostic features for the clinical diagnosis of tuberous sclerosis.

Helical flows and asymmetry of blood jet in dilated ascending aorta with normally functioning bicuspid valve

Bicuspid aortic valve (BAV) is associated with aortic dilatation and aneurysm. Several studies evidenced an eccentric systolic flow in ascending aorta associated with increased wall shear stresses (WSS) and the occurrence of an helical systolic flow. This study seeks to elucidate the connections between jet asymmetry and helical flow in patients with normally functioning BAV and dilated ascending aorta. We performed a computational parametric study by varying, for a patient-specific geometry, the valve area and the flow rate entering the aorta and drawing also a tricuspid valve (TAV). We considered also phase-contrast magnetic resonance imaging of four BAV and TAV patients. Measurement of normalized flow asymmetry index, systolic WSS and of a new index (positive helix fraction, PHF) quantifying the presence of a single a single helical flow were performed. In our computation, BAV cases featured higher values of all indices with respect to TAV in both numerical and imaged-based results. Moreover, all indices increased with decreasing valve area and/or with increasing flow rate. This allowed to separate the BAV and TAV cases with respect to the jet asymmetry, WSS localization and helical flow. Interestingly, these results were obtained without modeling the leaflets.

Reparative surgery of the pulmonary autograft: experience with Ross reoperations

OBJECTIVE Autograft valve and root pathology is the leading cause of Ross procedure failure. To define risk and outcome of autograft valve/root repair at reoperation, a 17-year experience was analysed. METHODS One hundred and thirty-two consecutive late survivors underwent cross-sectional clinical and echocardiographic examination on average 10.8 ± 14.7 years (range 0.4-17) after Ross procedure. Study endpoints were hospital and late morbidity, freedom from autograft reoperation, freedom from root/valve replacement and functional outcome after valve/root repair. RESULTS Twenty-seven (20%) patients underwent 33 cardiac reoperations, the first on average 7.7 ± 4.5 years (range 0.08-16.2) after Ross operation. Nineteen had undergone root replacement, 5 inclusion cylinder and 3 subcoronary grafting. Indication was root pathology in 17 (63%) patients and isolated valve in 10. Surgery consisted in valve repair/sparing in 17 patients and valve/root replacement in 10, with no hospital mortality. Freedom from any autograft valve/root reoperation was 74 ± 5% at 15 years. No patient with valve/root replacement required second reoperation. Instead, 6/17 (35%) patients having autograft valve repair/sparing and followed for 4.2 ± 2.9 years (range 0.3-10.8) required re-repair/AVR, while 11 present mild AI or less. Freedom from autograft valve/root replacement was 83 ± 5% at 15 years. At multivariate analysis, predictors of reoperation were age at Ross (P = 0.002) and use of root technique (P = 0.049). Failure of autograft valve repair/sparing was associated with isolated valve pathology (P = 0.014) and earlier reoperation (P = 0.002). Pre-repair autograft insufficiency was significant at univariate analysis only (P = 0.01). CONCLUSIONS Autograft reoperation carries negligible hospital risk. Pulmonary valve sparing or repair is feasible in half of patients with Ross failure. Concomitant root remodelling and absence of preoperative severe valve dysfunction predict successful and durable repair.

Spike topography and functional magnetic resonance imaging (fMRI) in benign rolandic epilepsy with spikes evoked by tapping stimulation.

We performed a spike topography study and a functional magnetic resonance imaging (fMRI) in a female patient with benign rolandic epilepsy presenting single high-amplitude evoked spikes in response to somatosensory peripheral stimulation. The stimulus was delivered to the first finger of the right hand using a tendon hammer, which evoked a single spike followed by a slow wave, showing the maximal amplitude over the left central regions. fMRI showed that the contralateral sensory cortices (S1 and S2) and the motor cortex (M I) were activated during tapping stimulation. In 3 normal subjects, tapping stimulation produced no fMRI activation. This fMRI study documents a highly focal activation of sensorimotor areas related to subclinical evoked spikes in benign rolandic epilepsy.

Is it possible to assess the best mitral valve repair in the individual patient? Preliminary results of a finite element study from magnetic resonance imaging data

OBJECTIVES Finite element modeling was adopted to quantitatively compare, for the first time and on a patient-specific basis, the biomechanical effects of a broad spectrum of different neochordal implantation techniques for the repair of isolated posterior mitral leaflet prolapse. METHODS Cardiac magnetic resonance images were acquired from 4 patients undergoing surgery. A patient-specific 3-dimensional model of the mitral apparatus and the motion of the annulus and papillary muscles were reconstructed. The location and extent of the prolapsing region were confirmed by intraoperative findings, and the mechanical properties of the mitral leaflets, chordae tendineae and expanded polytetrafluoroethylene neochordae were included. Mitral systolic biomechanics was simulated under preoperative conditions and after 5 different neochordal procedures: single neochorda, double neochorda, standard neochordal loop with 3 neochordae of the same length and 2 premeasured loops with 1 common neochordal loop and 3 different branched neochordae arising from it, alternatively one third and two thirds of the entire length. RESULTS The best repair in terms of biomechanics was achieved with a specific neochordal technique in the single patient, according to the location of the prolapsing region. However, all techniques achieved a slight reduction in papillary muscle forces and tension relief in intact native chordae proximal to the prolapsing region. Multiple neochordae implantation improved the repositioning of the prolapsing region below the annular plane and better redistributed mechanical stresses on the leaflet. CONCLUSIONS Although applied on a small cohort of patients, systematic biomechanical differences were noticed between neochordal techniques, potentially affecting their short- to long-term clinical outcomes. This study opens the way to patient-specific optimization of neochordal techniques.

Risonanza magnetica funzionale cerebrale applicazioni cliniche

Functional MRI of the brain can provide detailed images of human brain that reflect localized changes in cerebral blood flow and oxygenation induced by sensory, motor or cognitive tasks. While more complex functions can be explored only by high-field magnets equipped with echo-planar (EPI) facilities and sophisticated statistical methods of analysis, motor and visual functional activation studies can also be performed with conventional magnets, considering that these conditions are associated with more pronounced signal increases. Experience obtained in patients with a series of lesions located in the para-central (rolandic) area are reported and analyzed.

Functional and Biomechanical Effects of the Edge-to-Edge Repair in the Setting of Mitral Regurgitation: Consolidated Knowledge and Novel Tools to Gain Insight into Its Percutaneous Implementation

Mitral regurgitation is the most prevalent heart valve disease in the western population. When severe, it requires surgical treatment, repair being the preferred option. The edge-to-edge repair technique treats mitral regurgitation by suturing the leaflets together and creating a double-orifice valve. Due to its relative simplicity and versatility, it has become progressively more widespread. Recently, its percutaneous version has become feasible, and has raised interest thanks to the positive results of the Mitraclip® device. Edge-to-edge features and evolution have stimulated debate and multidisciplinary research by both clinicians and engineers. After providing an overview of representative studies in the field, here we propose a novel computational approach to the most recent percutaneous evolution of the edge-to-edge technique. Image-based structural finite element models of three mitral valves affected by posterior prolapse were derived from cine-cardiac magnetic resonance imaging. The models accounted for the patient-specific 3D geometry of the valve, including leaflet compound curvature pattern, patient-specific motion of annulus and papillary muscles, and hyperelastic and anisotropic mechanical properties of tissues. The biomechanics of the three valves throughout the entire cardiac cycle was simulated before and after Mitraclip® implantation, assessing the biomechanical impact of the procedure. For all three simulated MVs, Mitraclip® implantation significantly improved systolic leaflets coaptation, without inducing major alterations in systolic peak stresses. Diastolic orifice area was decreased, by up to 58.9%, and leaflets diastolic stresses became comparable, although lower, to systolic ones. Despite established knowledge on the edge-to-edge surgical repair, latest technological advances make its percutanoues implementation a challenging field of research. The modeling approach herein proposed may be expanded to analyze clinical scenarios that are currently critical for Mitraclip® implantation, helping the search for possible solutions.

Repair of mitral valve prolapse through ePTFE Neochordae: A finite element approach from CMR

Patient-specific finite element (FE) modeling is largely used to quantify mitral valve (MV) biomechanics associated to pathological and post-surgical conditions. We used this approach, integrated with non-invasive cardiac magnetic resonance (CMR) imaging data, to numerically perform the repair of the isolated mitral valve leaflet prolapse through expanded-polytetrafluoroethylene (ePTFE) sutures and quantitatively compare the effects of different techniques of neochordal implantation (NCI). CMR-derived FE models well reproduced MVP-related alterations and were able to assess the efficacy of each repairing technique and its biomechanical effects on MV apparatus; the quantification of biomechanical differences between NCI techniques, especially in terms of both chordal tensions and leaflet stresses redistribution, may impact on the short- and long-term the clinical outcome, potentially opening the way to patient-specific optimization of NCIs and, if extensively and successfully tested, improve surgical planning.

Aortic root physiology late after a "perfect" ross operation: magnetic resonance imaging study of three operative techniques.

In order to define physiological properties of the autograft root, magnetic resonance imaging (MRI) findings relative to three different operative techniques were compared with those of control subjects. Twenty-three patients, 18/5 M/F, aged 32 ± 9 years, underwent MRI assessment of the aortic root. Patients with normally functioning autograft valve and at least 4 years of follow-up (average 5.6 ± 1.9, range 4-10 years) were selected for each technique: six subcoronary (Group 1), nine inclusion (Group 2), and eight freestanding root (Group 3). Results were compared among patient groups and with seven control subjects, 6/1 M/F, aged 30 ± 2 years (P = ns). Morphological and functional properties were defined using transverse and paracoronal views, during systole and diastole. Mean aortic size in each group was greater than control, except for the LV-aortic junction and the sinus of Valsalva in Group 1 (26 ± 5 vs. 23 ± 3 mm, P = 0.2 and 33 ± 6 vs. 30 ± 5 mm, P = 0.3). Aortic valve plane rotation (P = 0.02) and root dilatation (P = 0.02) were more common in Group 3. Altered valve opening dynamics and asymmetrical aortic flow profile were also more common in Group 2 (P = 0.03) and Group 3 (P = 0.04). Distensibility was significantly reduced at sinus level in Group 2 and 3 compared with control (4.1 ± 3.5% and 3.6 ± 4.4% vs. 9.0 ± 4.7%, P = 0.03). Asymmetrical aortic flow profile was more common in patients with aortic dilatation (P = 0.05) and with severely reduced (<4%) root elasticity (P = 0.06). Among the three techniques, only subcoronary grafting allows preservation of physiological autograft valve dynamics, aortic flow and distensibility, at all root levels, late after operation. These findings may have relevant implications in the selection of the ideal Ross technique.