Andrea Mangini

Aortic root performance after valve sparing procedure: a comparative finite element analysis

David and Yacoub sparing techniques are the most common procedures adopted for the surgical correction of aortic root aneurysms. These surgical procedures entail the replacement of the sinuses of Valsalva with a synthetic graft, inside which the cusps are re-suspended. Root replacement by a synthetic graft may result in altered valve behaviour both in terms of coaptation and stress distribution, thus leading to the failure of the correction. A finite element approach was used to investigate this phenomenon; four 3D models of the aortic root were developed to simulate the root in physiological, pathological and post-operative conditions after the two different surgical procedures. The physiological 3D geometrical model was developed on the basis of anatomical data obtained from echocardiographic images; it was then modified to obtain the pathological and post-operative models. The effectiveness of both techniques was assessed by comparison with the first two simulated conditions, in terms of stresses acting on the root, leaflet coaptation and interaction between leaflets and the graft during valve opening. Results show that both sparing techniques are able to restore aortic valve coaptation and to reduce stresses induced by the initial root dilation. Nonetheless, both techniques lead to altered leaflet kinematics, with more evident alterations after David repair.

Assessment of an aortosaphenous vein graft anastomotic device in coronary surgery: Clinical experience and early angiographic results

BACKGROUND Until now technologic evolution in coronary bypass surgery has focused on extracorporeal circulation, on operation without extracorporeal circulation, and on the exposure of the operative site. Recently a one-shot anastomotic device for the proximal anastomosis in coronary surgery was developed. We investigated whether the use of the aortic connector system (ACS) could facilitate the creation of aortosaphenous vein graft anastomoses in myocardial revascularization. METHODS From November 2000, 40 ACS devices were used in 36 consecutive patients (mean age 70.7 +/- 8.9 years); 12 patients (33.3%) underwent surgery on pump and 24 patients (66.6%) off pump; 50 distal anastomoses were performed. In all cases the connection with the ascending aorta was created before the distal anastomoses because of the necessity to slide the saphenous vein graft (SVG) over the vein transfer sheath. Intraoperative graft function was tested measuring blood flow by Doppler analysis. Postoperative evaluation of the anastomotic patency was carried out by early angiography in 34 patients (94.7%) but was excluded in 5 patients (5.3%) with extensive extracardiac vascular occlusive disease. RESULTS Of 38 AC (95%) evaluated, 36 (94.7%) functioned properly. The end-to-side proximal anastomosis without aortic clamping is instantaneous, the quality of anastomoses was highly rated, no additional stitches were required, and all coronary arteries could be reached. Intraoperative quantity flow was measured by Doppler analysis and all but one showed good flow. Early postoperative angiography demonstrated good patency of the grafts in all cases but 2 (5.3%). At 1-year follow-up, 1 patient died of stroke; all other patients remained free of symptoms and no reoperation was required. CONCLUSIONS The use of ACS makes end-to-side anastomosis rapid, effective, and reproducible while eliminating aortic cross clamping; it opens a new era in beating or nonbeating coronary surgery. Long-term results are mandatory to confirm our favorable preliminary results.

Myocardial revascularization with multiple arterial grafts: comparison between the radial artery and the right internal thoracic artery

BACKGROUND Bilateral internal thoracic artery (ITA) harvesting is significantly underused, whereas the radial artery is being used with increasing frequency. We have retrospectively analyzed perioperative and short-term outcomes of patients receiving a radial artery versus those receiving a right ITA as a second arterial graft. METHODS Between February 1999 and May 2000, 250 patients underwent coronary artery bypass grafting using the radial artery (156 patients) or the right ITA (94 patients) in combination with the left ITA and, when required, the saphenous vein. RESULTS There was a higher prevalence of risk factors in the radial artery group. More coronary artery bypass graftings (p < 0.001) were performed with the radial artery. Operative mortality was not different (p = not significant). In the right ITA group there was more bleeding (p < 0.001) and a longer hospital stay (p < 0.001). Mean follow-up was 8.1 +/- 3.9 months. The probability of survival was similar (p = not significant). CONCLUSIONS The radial artery can extend the benefits of multiple arterial grafting to those patients who are usually excluded from bilateral ITA harvesting because of multiple risk factors. Perioperative and short-term results are good.

Surgical treatment of left ventricular post-infarction aneurysm with endoventriculoplasty: late clinical and functional results

OBJECTIVE The temporal response to endoventriculoplasty (EVP) has not been well defined. We have evaluated the long-term clinical and functional results of this technique. METHODS From 1988 to 1997, 121 patients underwent aneurysmectomy by EVP associated with myocardial revascularization for anteroapical left ventricular postinfarction aneurysm. Among these, 39 patients (43%) underwent early post-operative cardiac catheterization (within 3 months maximum), and were available to be revaluated after a mean follow-up time of 56+/-28 months, by means of a new hemodynamic study. Left ventricular silhouettes were analyzed by means of a special software. RESULTS The mean New York Heart Association functional class decreased from 2.5+/-0.9 to 1.6+/-0.8 (P<0.001) late postoperatively. The global ejection fraction improved early postoperatively from 43+/-13 to 61+/-13% (P<0.001), and late postoperatively slightly decreased to 42+/-13% (ns) versus preoperative values. Left ventricular end diastolic pressure early postoperatively fell from 16.8+/-7 to 15.7+/-6.7 (ns), and late postoperatively increased to 21.6+/-8.8 (ns) versus preoperative values. Pulmonary artery pressure rose early postoperatively from 31.5+/-6.4 to 32.1+/-6.7 (ns), and late postoperatively to 34.9+/-8.9 (ns). The global contractility score decreased early postoperatively from 42.3+/-9.6 to 28.4+/-13.6 (P<0.001); the global late postoperative contractily was 35+/-14 (ns) versus preoperative values. Patients who benefit most from the operation were those with a normal postoperative contraction pattern, where ejection fraction improved respectively early postoperatively from 43+/-13 to 63+/-11% (P<0.001), and late postoperatively to 49+/-10% (P<0.001) versus preoperative values. Occlusion or critical stenosis of bypass grafts occurred in 10 patients (25.6%). There were no significant differences in hemodynamic data and hypokinesis score changes between patients with patent or occluded bypass graft, and between patients with mono or multivessel disease. The operative mortality was 6.3%, and 8.8% needed intraaortic balloon counterpulsation. The actuarial survival rates at 5 and 7 years were 73+/-6 and 61+/-6%. The mean follow-up period was 68 months (with 112 months maximum). CONCLUSIONS We conclude that, in our patients group, EVP of left ventricular aneurysm associated with coronary grafting improves clinical status after operation. We registered a trend for a mild hemodynamic worsening, irrespective of coronary artery disease except in those patients who had shown a normal postoperative contraction pattern.

In vitro hemodynamics and valve imaging in passive beating hearts.

Due to their high complexity, surgical approaches to valve repair may benefit from the use of in vitro simulators both for training and for the investigation of those measures which can lead to better clinical results. In vitro tests are intrinsically more effective when all the anatomical substructures of the valvular complexes are preserved. In this work, a mock apparatus able to house an entire explanted porcine heart and subject it to pulsatile fluid-dynamic conditions was developed, in order to enable the hemodynamic analysis of simulated surgical procedures and the imaging of the valvular structures. The mock loops hydrodynamic design was based on an ad-hoc defined lumped-parameter model. The left ventricle of an entire swine heart was dynamically pressurized by an external computer-controlled pulse duplicator. The ascending aorta was connected to a hydraulic circuit which simulated the input impedance of the systemic circulation; a reservoir passively filled the left atrium. Accesses for endoscopic imaging were located in the apex of the left ventricle and in the aortic root. The experimental pressure and flow tracings were comparable with the typical in vivo curves; a mean flow of 3.5±0.1l pm and a mean arterial pressure of 101±2 mmHg was obtained. High-quality echographic and endoscopic video recordings demonstrated the systems excellent potential in the observation of the cardiac structures dynamics. The proposed mock loop represents a suitable in vitro system for the testing of minimally-invasive cardiovascular devices and surgical procedures for heart valve repair.

Effects of heart rate on phasic Y-graft blood flow and flow reserve in patients with complete arterial myocardial revascularizaton: an intravascular Doppler catheter study

OBJECTIVE It is not well established whether the blood flow of arterial composite Y-grafts can efficiently respond to the flow demand of the coronary system early postoperatively. The aim of this study was to evaluate if soon after the operation, arterial composite Y-grafts can increase blood flow in response to an increase in myocardial oxygen consumption (MVO2). METHODS Twenty-seven patients who received complete arterial myocardial revascularization using the left internal thoracic artery (LITA) and the radial artery (RA) as composite Y-graft gave their consent to a pre-discharge coronary angiography and intravascular flow velocity measurements using a Doppler guide wire. Flow measurements were performed in the LITA main stem, the distal LITA and the RA, both at rest and during atrial pacing at the 85% of the patient age-predicted maximum. The heart rate-systolic blood pressure product was considered as an indirect index of MVO2. Hyperemic flow was determined after injection of adenosine. The flow reserve (FR) was defined as the ratio of blood flow during maximal hyperemia (Qmax) to baseline flow (Qbasal). RESULTS Atrial pacing increased MVO2 significantly (P<0.000). None of the patients developed ischemic S-T segment modifications or complained of chest pain. Q(basal) increased significantly in the LITA main stem (P=0.001), distal LITA (P=0.041) and RA (P=0.004) while Qmax did not change significantly. As a consequence, the FR decreased in the LITA main stem (P=0.002), distal LITA (P<0.000) and RA (P<0.000) but was not completely exhausted. CONCLUSIONS Soon after the operation, arterial composite Y-grafts can significantly increase blood flow in response to conditions of increased MVO2, keeping normal the myocardial O2 supply-to-demand ratio.

In vitro study of the aortic interleaflet triangle reshaping.

Aortic interleaflet triangle reshaping (AITR) is a surgical approach to aortic valve incontinence that involves placing three stitches at half of the interleaflet triangles height. In this work, the relationship between the actual stitch height and valve functioning, and the safety margin that the surgeon can rely on in applying the stitches were systematically investigated in vitro. AITR surgery was applied to six swine aortic roots placing the stitches empirically at 50%, 60% and 75% of the triangle heights. Then the actual stitch heights were measured and the hydrodynamic performances were evaluated with a pulsatile hydrodynamic mock loop. Actual stitch heights were 45±2%, 61±4% and 79±6%. As compared to untreated conditions, the 50% configuration induced a significant variation in the effective orifice area. With stitches placed at 60%, the mean systolic pressure drop increased significantly with respect to the untreated case, but no significant changes were recorded with respect to the 50% configuration. At 75%, all the hydrodynamic parameters of systolic valve functioning worsened significantly. Summarizing, the AITR technique, when performed in a conservative manner did not induce significant alterations in the hydrodynamics of the aortic root in vitro, while more aggressive configurations did. The absence of a statistically significant difference between the 50% and 60% configurations suggests that there is a reasonably limited risk of inducing valve stenosis in the post-op scenario due to stitch misplacement.

Bicuspid aortic valve: differences in the phenotypic continuum affect the repair technique

OBJECTIVE Bicuspid aortic valve (BAV) may be considered in the context of a phenotypic continuum of the aortic valve configuration, ranging from severe forms of unicuspid valve to rare forms of quadricuspid valve. In this article, we report our results with BAV repair using surgical techniques tailored to the specific features of the BAV phenotypic continuum. PATIENTS AND METHODS Between September 2003 and May 2009, 31 patients with BAV (mean age 49.9+/-17.3 years; five female; 26 male) were prospectively enrolled for aortic valve repair. The surgical strategy was tailored depending on the anatomical and structural characteristic of the BAV continuum: type 1 real bicuspid (five patients), type 2 bicuspid with raphe (24 patients) and type 3 clefted bicuspid (two patients). An echocardiographic analysis was performed preoperatively, postoperatively, at discharge and every 6 months during follow-up. Kaplan-Meier analysis was used to assess the freedom from re-operation. RESULTS One patient died in the intensive care unit due to aortic wall rupture. After BAV repair there was an increase of leaflet coaptation length (from 2.0+/-0.5 mm to 8.2+/-1.9 mm, p<0.01) and a decrease of the diameters of the virtual basal ring (from 24.6+/-3.6 mm to 21.5+/-0.71 mm, p<0.01), of the aortic root (from 43.12+/-13.23 mm to 31.0+/-3.2 mm, p<0.01) and of the sino-tubular junction (from 40.1+/-6.95 mm to 33.5+/-9.19 mm, p<0.05). The aortic regurgitation echocardiographic grade > or =II was found preoperatively in 30 patients and postoperatively in one patient (p<0.01). Six patients underwent an associated aortic valve-sparing procedure (three re-implantation and three remodelling). Kaplan-Meier analysis showed a 96.6% freedom from re-operation at 5 years, with a single new repair procedure and a 100% freedom from aortic valve replacement. CONCLUSIONS BAV repair provides a feasible therapeutic option in selected patients with good medium-term results. The surgical techniques should be applied after a careful analysis of the BAV considered in the context of the phenotypic continuum.

Fluid-dynamic results of in vitro comparison of four pericardial bioprostheses implanted in small porcine aortic roots

OBJECTIVES Small-sized aortic bioprostheses may cause high postoperative gradients. In clinical practice, it is difficult to compare bioprostheses from different manufactures, owing to the discrepancy between the true size and the nominal size of the prosthesis and the inter-patient variability in aortic root characteristics. In vitro studies provide accurate data, and using a system in which it is possible to implant bioprostheses in a true aortic root should enable a fair comparison to be made. The present study compared the four most widely used pericardial stented bioprostheses from different manufacturers surgically implanted in small annulus, to detect any differences in their fluid-dynamic performance. METHODS The four types of bioprostheses, each implanted in a randomized sequence in eight porcine aortic roots, with a native annulus of 2.1 cm, were tested in a mock loop at 65 ml of stroke volume by calculating hydrodynamic parameters, namely mean pressure drop and effective orifice area, performance index, valve resistance and % of energy loss. The prostheses that fitted the aortic root after sizing were as follows: a Magna Ease 21, a Trifecta 21, a Soprano-Armonia 20 and a Mitroflow 23. RESULTS Effective orifice areas were 1.57 ± 0.2, 1.77 ± 0.2, 2.3 ± 0.3 and 1.75 ± 0.2 cm(2) (P < 0.001) for Magna Ease, Mitroflow, Trifecta and Soprano-Armonia, respectively. The mean gradients were 13.2 ± 3, 10.2 ± 3, 6.1 ± 2 and 9.6 ± 2 mmHg (P < 0.001) for Magna Ease, Mitroflow, Trifecta and Soprano-Armonia, respectively. The performance indices were 0.50 ± 0.06, 0.63 ± 0.08, 0.89 ± 0.13 and 0.56 ± 0.07 (P < 0.001) for Magna Ease, Mitroflow, Trifecta and Soprano-Armonia, respectively. The valve resistance, expressed in (dyn*s/cm(5)), was 69 ± 16, 55 ± 13, 33 ± 10 and 51 ± 11 (P < 0.001) for Magna Ease, Mitroflow, Trifecta and Soprano-Armonia, respectively. The percent of energy loss was 13.5 ± 0.5, 10.7 ± 2.5, 6.6 ± 1.6, 10.9 ± 1.8 (P < 0.001) for Magna Ease, Mitroflow, Trifecta and Soprano-Armonia, respectively. CONCLUSION Our study combined the fluid-dynamic reproducibility of the in vitro study with, by using porcine aortic roots, the specificity of surgery. The results confirmed that bioprostheses are inherently obstructive compared with the native aortic valve and showed that bioprostheses with the pericardium outside the stent are more efficient.

A geometric approach to aortic root surgical anatomy

OBJECTIVES The aim of this study was the analysis of the geometrical relationships between the different structures constituting the aortic root, with particular attention to interleaflet triangles, haemodynamic ventriculo-arterial junction and functional aortic annulus in normal subjects. METHODS Sixteen formol-fixed human hearts with normal aortic roots were studied. The aortic root was isolated, sectioned at the midpoint of the non-coronary sinus, spread apart and photographed by a high-resolution digital camera. After calibration and picture resizing, the software AutoCAD 2004 was used to identify and measure all the elements of the interleaflets triangles and of the aortic root that were objects of our analysis. Multiple comparisons were performed with one-way analysis of variance for continuous data and with Kruskal-Wallis analysis for non-continuous data. Linear regression and Pearsons product correlation were used to correlate root element dimensions when appropriate. Students t-test was used to compare means for unpaired data. Herons formula was applied to estimate the functional aortic annular diameters. RESULTS The non coronary-left coronary interleaflets triangles were larger, followed by inter-coronary and right-non-coronary ones. The apical angle is <60° and its standard deviation can be considered an asymmetry index. The sinu-tubular junction was shown to be 10% larger than the virtual basal ring (VBR). The mathematical relationship between the haemodynamic ventriculo-arterial junction and the VBR calculated by linear regression and expressed in terms of the diameter was: haemodynamic ventriculo-arterial junction = 2.29 VBR (diameter) + 47. DISCUSSION Conservative aortic surgery is based on a better understanding of aortic root anatomy and physiology. The relationships among its elements are of paramount importance during aortic valve repair/sparing procedures and they can be useful also in echocardiographic analysis and in computed tomography reconstruction.