Giordano Tasca

Does the type of suture technique affect the fluid-dynamic performance of bioprostheses implanted in small aortic roots? Results from an in vitro study

BACKGROUNDnThe in vivo hemodynamic performance of a bioprosthesis implanted in an aortic position is affected by the characteristics of the prosthesis and the sizing strategy adopted. Recently, it has been hypothesized that the type of suture used to implant the prosthesis might influence hemodynamics.nnnMETHODSnBioprostheses with labeled sizes of 19 mm and 21 mm were implanted in 2 groups of 5 porcine aortic roots, with native annuli of 19 mm and 21 mm, by means of 2 different suture techniques: simple interrupted and noneverting mattress with pledgets. The aortic roots were tested in an in vitro mock loop. The stroke volume imposed by the mock loop was set at 40 mL, and was increased by steps of 15 mL until a stroke volume of 100 mL was attained. Main fluid-dynamic parameters were analyzed.nnnRESULTSnAt each level of stroke volume, ie, 40 mL, 55 mL, 70 mL, 85 mL, and 100 mL, the mean and peak pressure drops were significantly greater with the noneverting mattress suture with pledgets than with the simple interrupted suture. The effective orifice area behaved accordingly, being significantly smaller in the former case.nnnCONCLUSIONSnOur data show that the type of suture technique can influence bioprosthesis performance and that it is reasonable to assume that this is especially true in small annuli (≤ 21 mm). Thus, to optimize prosthesis performance and reduce the incidence of patient-prosthesis mismatch, the role of the suture technique should not be disregarded.

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

OBJECTIVESnSmall-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.nnnMETHODSnThe 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.nnnRESULTSnEffective 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.nnnCONCLUSIONnOur 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.

Aortic Root Biomechanics After Sleeve and David Sparing Techniques: A Finite Element Analysis

BACKGROUNDnAortic root aneurysm can be treated with valve-sparing procedures. The David and Yacoub techniques have shown excellent long-term results but are technically demanding. Recently, a new and simpler procedure, the Sleeve technique, was proposed with encouraging results. We aimed to quantify the biomechanics of the initially aneurysmal aortic root (AR) after the Sleeve procedure to assess whether it induces abnormal stresses, potentially undermining its durability.nnnMETHODSnTwo finite element (FE) models of the physiologic and aneurysmal AR were built, accounting for the anatomical asymmetry and the nonlinear and anisotropic mechanical properties of human AR tissues. On the aneurysmal model, the Sleeve and David techniques were simulated based on the corresponding published technical features. Aortic root biomechanics throughout 2 consecutive cardiac cycles were computed in each simulated configuration.nnnRESULTSnBoth sparing techniques restored physiologic-like kinematics of aortic valve (AV) leaflets but induced different leaflets stresses. The time course averaged over the leaflets bellies was 35% higher in the David model than in the Sleeve model. Commissural stresses, which were equal to 153 and 318 kPa in the physiologic and aneurysmal models, respectively, became 369 and 208 kPa in the David and Sleeve models, respectively.nnnCONCLUSIONSnNo intrinsic structural problems were detected in the Sleeve model that might jeopardize the durability of the procedure. If corroborated by long-term clinical outcomes, the results obtained suggest that using this new technique could successfully simplify the surgical repair of AR aneurysms and reduce intraoperative complications.

Comparison of the Performance of a Sutureless Bioprosthesis With Two Pericardial Stented Valves on Small Annuli: An In Vitro Study

BACKGROUNDnAortic valve replacement has evolved recently with the development of the sutureless bioprosthesis. One such valve is the Perceval bioprosthesis, which is built by mounting leaflets of bovine pericardium to a thin stent; this approach has the potential to provide an excellent fluid dynamic performance. We undertook an inxa0vitro study to compare the hydrodynamic performance of the sutureless bioprosthesis with two standard pericardial stented bioprostheses (Crown and Magna).nnnMETHODSnTests were conducted using a mock loop, testing on two sizes of the three prostheses. The prosthesis sizes were chosen to house the valves in porcine aortic roots with a native annulus diameter of 19 mm (nxa0= 6) or 21 mm (nxa0= 6). The stroke volume ranged from 25 mL to 105 mL at a simulated heart rate of 70 beats per minute.nnnRESULTSnMean pressure drop and energy loss rose with increasing stroke volume in all of the valves tested (pxa0<xa00.001), with the sutureless valve showing the lowest values for both variables (p < 0.001). Effective orifice area values were stable across the stroke volume intervals and were larger in the sutureless valves (p < 0.001).nnnCONCLUSIONSnAll of the valves tested provided good fluid dynamic performances. The sutureless bioprosthesis provided the best performance with the least hindrance to flow behavior. From the hydrodynamic perspective, the sutureless prosthesis may present an advance in the evolution of bioprostheses, ensuring low gradients and potential for low incidence of patient-prosthesis mismatch even in small annuli.

Design of a simple coronary impedance simulator for the in vitro study of the complex coronary hemodynamics

Several novel approaches were recently developed to treat aortic root pathologies. The alteration induced by some of these approaches to the biomechanics of the aortic root could possibly affect the coronary perfusion, compromising the procedural outcome. In this scenario, the need to replicate in vitro the coronary flow pattern in physiological and pathological conditions is becoming crucial for the functional assessment of novel devices and techniques. This article describes the design of an easy-to-use, left-and-right coronary impedance simulator, coupled with native aortic roots for in vitro pulsatile tests. Experiments were performed in order to assess the performances of the coronary impedance simulator when coupled with healthy aortic valves (cardiac output: 3.8u2009u2009±u2009u20090.26 l min-1; mean systemic pressure: 95u2009u2009±u2009u20091.3 mmHg; mean coronary flow rate: 272u2009u2009±u2009u200913.4u2009ml min-1) or with regurgitant valves (cardiac output: 1.9u2009u2009±u2009u20090.24 l min-1; mean systemic pressure of 45u2009u2009±u2009u20093.3 mmHg; mean coronary flow rate:149u2009u2009±u2009u200921.9u2009ml min-1). The acute systemic response to valve regurgitation was also replicated, with increased beat rate and afterload, aimed at restoring the systemic pressure (cardiac output: 2.5u2009u2009±u2009u20090.23 l min-1; mean systemic pressure of 109u2009u2009±u2009u20096.1 mmHg; mean coronary flow rate: 262u2009u2009±u2009u200935.5u2009ml min-1). In the test conditions, the system was able to replicate in vitro the main determinants of the coronary circulation with physiological left/right coronary flow rate repartition, and a realistic interaction between coronary and systemic hemodynamics. The coronary simulator appears to be a suitable platform to study and optimize the interactions between novel approaches to aortic valve pathology and the coronary perfusion.

Medical treatment of eng-stage heart failure

SummaryCongestive heart failure is a lethal condition that affects an increasing number of patients. In recent years a great amount of data have accumulated on the pathophysiology and medical and surgical therapy of this condition. In spite of the advances in its management and the great number of patients affected, common errors are still made by internists and cardiologists in the use of drugs and therapeutic strategies. Digitalis has only recently been shown to affect hemodynamics, exercise capacity, and clinical symptoms, but the effects on survival still have to be demonstrated. Loop diuretics, eventually combined with thiazides and antialdosterone drugs in patients with clinical signs and symptoms of fluid retention, are the mainstays of therapy of congestive heart failure. In order to make diuretic therapy efficacious, moderate salt and water intake restriction is mandatory. Angiotensin-converting enzyme (ACE) inhibitors are now considered unavoidable drugs in the management of heart failure, and an attempt to reach the doses that have been shown to be efficacious for survival in the large trials has to be made in every patient with this condition. Other vasodilators, such as hydralazine and nitrates, which show a less pronounced effect on survival but more effective hemodynamic actions than ACE inhibitors, may be used to control mitral insufficiency or to improve hemodynamics in very sick patients. Hemodynamic instability refractory to increasing doses of vasodilators and diuretics is a severe condition that requires hospital admission to administer drugs parenterally. These patients are usually treated with the combination of catecholamines and phosphodiesterase inhibitors associated with intravenous diuretics until clinical stability is again achieved and oral therapy is resumed and restructured. The use of aggressive pharmacological therapy and phosphodiesterase inhibitors has reduced the need for assisted circulatory support in these patients. Beta-blockers have shown promising results when administered to patients with heart failure, although a definitive demonstration of their effects on survival is still lacking. Other additional measures that need to be considered in patients with end-stage congestive heart failure are the use of antiarrhythmic drugs and anticoagulation.

Opening-closing pattern of four pericardial prostheses: results from an in vitro study of leaflet kinematics.

Pericardial and porcine stented aortic valves have different leaflet kinematics. To study the biomechanics of a prosthesis thoroughly, the in vitro setting is the most appropriate. The aim of our study was to find out whether the prosthesis design in which the pericardial sheet is outside the stent post might influence the opening and closing patterns of the leaflets. Four pericardial prostheses (Magna Ease [MG] 21, Trifecta [TRI] 21, Soprano-Armonia [SA] 20 and Mitroflow [MF] 23) that fitted aortic roots with a native annulus diameter of 2.1xa0cm were implanted and their leaflet kinematics was studied by a high-speed digital camera. In the opening phase, MG showed the shortest RVOT and the highest RVOVI, with values of 12xa0±xa02 and 209xa0±xa017xa0ms, respectively. The RVOT of MG was significantly shorter than that of MF (pxa0<xa00.01), but not than that of TRI (pxa0=xa00.286). Both TRI and SA showed similar opening patterns (TRI: RVOT of 15xa0±xa03xa0ms and RVOVI of 132xa0±xa025xa0ms; SA: 17xa0±xa02xa0ms and 126xa0±xa019xa0ms), without statistically significant difference. Conversely, MF showed the slowest profile, with an RVOT of 23xa0±xa03xa0ms and an RVOVI of 94xa0±xa08xa0ms (Tablexa01; Fig.xa03). The opening/closing profile is not influenced by the position of the pericardial leaflets, but depends on other intrinsic structural characteristics related to the material used for the stent and leaflets. Moreover, the kinematics does not affect the valve performance.Tablexa01Kinematics and hydrodynamic results, reported as means and standard deviations, evaluated over the tested heart samplesTRISAMGMFANOVATRI versus SATRI versus MGTRI versus MFSA versus MGSA versus MFMG versus MFp Valuep Valuep Valuep Valuep Valuep Valuep ValueET (ms)1.01.01.01.0RVOT (ms)15xa0±xa0317xa0±xa0212xa0±xa0223xa0±xa03<0.011.00.286<0.010.03<0.01<0.01SVCT (ms)247xa0±xa014231xa0±xa015256xa0±xa026241xa0±xa0110.1700.4630.8530.9310.2131.01.0RVCT (ms)35xa0±xa01952xa0±xa01332xa0±xa01752xa0±xa040.070.4741.00.4940.2361.00.247TVCT (ms)283xa0±xa010283xa0±xa019289xa0±xa010293xa0±xa0110.5841.001.01.01.01.01.0RVOVI (ms−1)132xa0±xa025126xa0±xa019209xa0±xa01794xa0±xa08<0.010.959<0.010.02<0.010.07<0.01SVCVI (ms−1)−0.9xa0±xa00.3−1.1xa0±xa00.4−0.57xa0±xa00.1−0.55xa0±xa00.1<0.011.00.3530.2920.0450.041.0RVCVI (ms−1)−16xa0±xa04−10xa0±xa02−18xa0±xa06−10xa0±xa01<0.010.3961.00.5130.0251.00.03Δp (mmHg)6.7xa0±xa03.610.6xa0±xa05.515.2xa0±xa07.910.7xa0±xa06.1<0.010.01<0.010.010.041.0<0.01EOA (cm2)2.2xa0±xa01.21.7xa0±xa00.91.5xa0±xa00.81.7xa0±xa00.9<0.010.03<0.010.010.2610.6170.11El xa0%7.3xa0±xa0111.9xa0±xa0115.4xa0±xa0211.8xa0±xa03<0.01<0.01<0.01<0.010.041.000.03CO (L/min)3.1xa0±xa00.42.8xa0±xa00.53.1xa0±xa00.33.0xa0±xa00.50.5340.2820.7920.7020.1060.5520.559ET ejection time, RVOT rapid valve-opening time, SVCT slow valve-closing time, RVCT rapid valve-closing time, TVCT total valve-closing time, RVOVI rapid valve-opening velocity index, SVCVI slow valve-closing velocity index, RVCVI rapid valve-closing velocity index, Δp mean pressure drop, EOA effective orifice area, Elxa0% energy loss, CO cardiac output

Opening/closing pattern of Trifecta and Freestyle valves versus native aortic valve: Are stentless valves more physiologic than a stented valve?

Stentless valves have long been considered the ideal valves in terms of hemodynamics. Recently, the Trifecta valve, a stented bioprosthesis with excellent fluid dynamic characteristics, has become available. The aim of the study was to compare the opening/closing pattern of the Freestyle stentless valve and the Trifecta valve with that of the native aortic valve.