6-Month aortic valve implantation of an off-the-shelf tissue-engineered valve in sheep

Diseased aortic valves often require replacement, with over 30% of the current aortic valve surgeries performed in patients who will outlive a bioprosthetic valve. While many promising tissue-engineered valves have been created in the lab using the cell-seeded polymeric scaffold paradigm, none have been successfully tested long-term in the aortic position of a pre-clinical model. The high pressure gradients and dynamic flow across the aortic valve leaflets require engineering a tissue that has the strength and compliance to withstand high mechanical demand without compromising normal hemodynamics. A long-term preclinical evaluation of an off-the-shelf tissue-engineered aortic valve in the sheep model is presented here. The valves were made from a tube of decellularized cell-produced matrix mounted on a frame. The engineered matrix is primarily composed of collagen, with strength and organization comparable to native valve leaflets. In vitro testing showed excellent hemodynamic performance with low regurgitation, low systolic pressure gradient, and large orifice area. The implanted valves showed large-scale leaflet motion and maintained effective orifice area throughout the duration of the 6-month implant, with no calcification. After 24 weeks implantation (over 17 million cycles), the valves showed no change in tensile mechanical properties. In addition, histology and DNA quantitation showed repopulation of the engineered matrix with interstitial-like cells and endothelialization. New extracellular matrix deposition, including elastin, further demonstrates positive tissue remodeling in addition to recellularization and valve function. Long-term implantation in the sheep model resulted in functionality, matrix remodeling, and recellularization, unprecedented results for a tissue-engineered aortic valve.     

新鲜主动脉瓣与肺动脉瓣的解剖学观测及其临床意义

目的：从解剖学方面为自体肺动脉瓣替换主动脉瓣手术提供理论依据。方法：对１１例正常国人新鲜心脏标本的主、肺动脉瓣进行解剖学测量,并对结果进行对比研究。结果：①肺动脉瓣所能承受的压力虽小于主动脉瓣所能承受的压力,但其最小值（２８ｋＰａ）高于正常人体动脉压;②肺动脉瓣及肺动脉窦的各项测量数值均略大于主动脉瓣及主动脉窦,但无统计学意义（Ｐ＞０．０５）。结论：①肺动脉瓣能承受主动脉瓣位置的压力;②主、肺动脉瓣叶及主、肺动脉窦在形态、大小上是匹配的。     

The membranous portion of the interventricular septum and its relationship with the aortic valve in humans

Summary Investigation of the membranous portion of the interventricular septum (MPIS) and its relationship with the aortic valve was performed in 32 human hearts of adult individuals (19 Caucasians and 11 non-Caucasians). With transillumination of the MPIS the specimens were photographed and 35 mm slides obtained. These were digitized into Apple Macintosh II using a Dage Model 68 video camera and a Data Translations DT 2255 frame grabber. The areas and the distances were traced manually, using the NIH Image program (Wayne Rasband, NIH, Research Services Branch, NIHM). The following forms of MPIS were found: oval (31.3%), triangular (28.1%), quadrangular (18.8%), circular (15.6%) and semilunar (6.2%); its surface area varied from 5.65 mm² to 142.63 mm² (mean 48.82±29.17 mm²). The superior border of the MPIS was in close relationship with the aortic valve, and its upper part was usually (41%) in direct continuity with the attachments of both right (RAC) and posterior (PAC) aortic cusps, or with PAC (34%) or RAC (6%) only. Rarely (19%) the MPIS lay below the attachments of both cusps. The distance between the MPIS superior border and the attachment of the RAC was not greater than 5.89 mm (mean 1.69 mm±1.9 mm). The distance between the superior border of the MPIS and the attachment of the PAC was not greater than 5.63 mm (mean 0.77±1.49 mm). Differences between sex, race and age groups were not statistically significant.

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La portion membraneuse du septum interventriculaire et ses rapports avec la valve aortique chez l'homme

Résumé L'étude de la portion membraneuse du septum interventriculaire (PMSIV) et de ses rapports avec la valve aortique a été réalisée sur 32 curs humains adultes (19 Caucasiens et 11 non-Caucasiens). Sous transillumination, la PMSIV est photographiée et les diapositives de 35 mm obtenues sont numérisées dans le Apple MacIntosh II, utilisant une caméra vidéo « Dage Model 68 » et un convertisseur d'images « DT 2255 frame grabber ». Les surfaces et les distances sont tracées manuellement, utilisant le « programme d'images NIH » (Wayne Rasband, NIH, Research Services Branch, NIHM). Les formes suivantes de la PMSIV ont été observées : ovale (31,3 %), triangulaire (28,1 %), quadrangulaire (18,8 %), circulaire (15,6 %) et semi-lunaire (6,2 %). Sa surface varie de 5,65 mm² à 142,63 mm² (moyenne 48,82±29). Le bord supérieur de la PMSIV contracte des rapports intimes avec la valve aortique; sa partie haute est habituellement en continuité directe avec les pieds d'insertion des valuvles aortiques : les deux valvules droite (VAD) et postérieure (VAP) dans 41 %; la VAP ou la VAD isolément, respectivement dans 34 et 6 % des cas. Rarement (19 %) la PMSIV se situe au-dessous des bords adhérents de ces valvules VAD et VAP. La distance entre le bord supérieur de la PMSIV et l'insertion de la VAD n'est pas supérieure à 5,89 mm (M : 1,69 mm±1,9 mm). La distance entre le bord supérieur de la PMSIV et l'insertion de la VAP n'est pas supérieure à 5,63 mm (M : 0,77±1,49 mm). Les différences entre sexes, races et âges ne sont pas statistiquement significatives.

     

A case in which biventricular assist device support was required after aortic valve replacement with a bioprosthetic valve

We report the case of a 45-year-old man with severe aortic regurgitation. The patient underwent aortic valve replacement with a bioprosthetic valve, but was unable to be weaned from cardiopulmonary bypass (CPB). Intraoperative coronary angiography revealed stenosis of the right coronary orifice, so an intra-aortic balloon pump was inserted and coronary artery bypass grafting to the right coronary artery was conducted; however, weaning from CPB again failed. Left ventricular assist using a Gyro centrifugal pump was performed between the left atrium and left femoral artery, along with right ventricular assist using a Nikkiso centrifugal pump between the right atrium and pulmonary artery. Flow rates averaged from 2.0 to 2.8l/min for the left-side ventricular assist device (VAD) and 2.1–3.8l/min for the right-side VAD. The bypass rate reached approximately 70% at maximum. No thromboembolic events were documented during VAD support. The patient underwent explantation of VADs on postoperative day 4. No thrombus was identified on the bioprosthetic aortic valve by transesophageal echocardiography. The left-side pump displayed no thrombus, while the right-side pump had a small thrombus at the shaft. The patient was discharged from the hospital and was alive as of 2 year postoperatively. To the best of our knowledge, no clinical study has yet compared the antithrombotic properties of two centrifugal pumps in one patient where mechanical support was performed for the same duration and flow rate.     

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs

A surgical protocol was designed to implant, in seven dogs, a programmable sequential atrioventricular pacemaker after destruction of the bundle of His to produce a chronic heart block. The heart rate and P-R interval were then varied independently and their influence on the spectra and acoustic transmission of the mitral M1 and aortic A2 valve closure sounds was studied. Results indicate that the major effects of varying the P-R interval are a strong change in the intensity of M1 and modifications of its acoustic transmission across the heart/thorax acoustic system. No similar influence is observed on the intensity and acoustic transmission of A2. Varying the heart rate has a small effect of the intensity of M1 but none on the intensity of A2. In addition, changes in either the P-R interval or the heart rate do not seem to modify the spectral profile of the intracardiac and thoracic M1 and A2 components.     

理想主动脉瓣模型闭合机制的研究

目的;分析理想状态下主动脉瓣关闭机制。方法：建立理想的主动脉瓣模型,用几何学的方法对不同瓣叶情况下的瓣膜受力情况进行分析。结果：二叶瓣无法开放,不符合生理要求。四叶瓣完全开放后,瓣叶完全贴于瓣环,在血液返流的方向上没有受力面积,不利于瓣膜的关闭。三叶瓣在完全开放的状态下,在血液返流的方向上有一个大小较为合理的截面积,有利于瓣膜的闭合受力。结论;在完全开放状态下,主动脉瓣在血液返流方向上的截面积是其关闭动力的重要来源,从关闭角度来讲,三叶瓣是唯一理想的瓣膜。     

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs

A system model based on the simultaneous recording and analysis of the intracardiac and thoracic phonocardiograms to estimate the time-varying properties of the heart/thorax acoustic system of the dog is described. The presence of instrumental noise in the recording of intracardiac phonocardiograms is characterised, and it is demonstrated that its effect on the estimate of the transfer and coherence functions of the system can be quantified and corrected. Application of the model to study the spectral characteristics and the acoustic transmission properties of the mitral component M1 of the first heart sound and of the aortic component A2 of the second heart sound in the dog shows that the heart/thorax acoustic system acts like a bandpass filter having a higher attenuation for A2 than for M1. Between 20 and 100 Hz, the mean attenuation of M1 is 30 dB while that of A2 is 46 dB. Above 100 Hz, the attenuation slope is—12 dB per octave for M1 and—6 dB per octave for A2.     

Non-invasive assessment of aortic mechanical properties

Echocardiography and sphygmomanometry were used to noninvasively assess the changes in aortic mechanical properties associated with aging. Fifty normal individuals were examined and were divided into three groups: young (<35 years of age), middle-aged (35–55), and old (>55). Experimental measurements indicated that elastic aortic stiffness in the circumferential direction increased with increased age. It was concluded that this was consistent with increased deposition of circumferentially oriented collagen within the media. Associated with increased elastic aortic stiffness in the circumferential direction was a decrease in the ability of the aorta to act as an auxiliary pump. The average work per unit length recovered from aortas of older individuals was only 44% of that recovered from the aortas of individuals in the young group. These studies suggest that increased elastic aortic stiffness results in decreased aortic pumping efficiency and may lead to a compensating increase in blood pressure. The authors would like to acknowledge grant support from the Whitaker Foundation and the National Institutes of Health (GMS 30425). Dr. Tsipouras is the recipient of a Clinical Investigator Award AM-01224 from the NIADDKD. We would also like to thank Dr. John Kostis for use of the echocardiographic equipment in the cardiodynamics unit of the Department of Medicine, Middlesex General Hospital, New Brunswick, New Jersey.     

Incidence and outcomes of infective endocarditis after transcatheter aortic valve implantation versus surgical aortic valve replacement

ObjectivesTranscatheter aortic valve implantation (TAVI) is an alternative to surgical aortic valve replacement (AVR) in aortic stenosis (AS). Infective endocarditis (IE) in patients with prosthetic heart valves is associated with significant morbidity and mortality. Data on the incidence, risk factors, and outcomes of IE after TAVI are conflicting. We evaluated these issues in patients with percutaneous TAVI vs. isolated surgical AVR (SAVR) at a nationwide level.MethodsBased on the administrative hospital discharge database, the study collected information for all patients with aortic stenosis treated with AVR in France between 2010 and 2018.ResultsA total of 47 553 patients undergoing TAVI and 60 253 patients undergoing isolated SAVR were identified. During a mean follow-up of 2.0 years (median (25th to 75th percentile) 1.2 (0.1–3.4) years), the incidence rates of IE were 1.89 (95% confidence interval (CI) 1.78–2.00) and 1.40 (95% CI 1.34–1.46) events per 100 person-years in unmatched TAVI and SAVR patients, respectively. In 32 582 propensity-matched patients (16 291 with TAVI and 16 291 with SAVR), risk of IE was not different in patients treated with TAVI vs. SAVR (incidence rates of IE 1.86 (95% CI 1.70–2.04) %/year vs 1.71 (95% CI 1.58–1.85) %/year respectively, relative risk (RR) 1.09, 95% CI 0.96–1.23). In these matched patients, total mortality was higher in TAVI patients with IE (43.0% 95% CI 37.3–49.3) than in SAVR patients with IE (32.8% 95% CI 28.6–37.3; RR 1.32, 95% CI 1.08–1.60).DiscussionIn a nationwide cohort of patients with AS, treatment with TAVI was associated with a risk of IE similar to that following SAVR. Mortality was higher for patients with IE following TAVI than for those with IE following SAVR.     

内皮素-1水平与单纯行主动脉瓣置换术患者术后新发房颤的相关性分析

目的探讨内皮素-1水平与单纯行主动脉瓣置换术患者术后新发房颤的关系。 方法回顾性分析2017年6月至2019年6月于首都医科大学附属北京安贞医院结构性心脏病外科中心单纯行主动脉瓣置换术的119例患者的临床资料,根据患者术后是否新发房颤分为术后房颤组(n＝28)和无术后房颤组(n＝91)。2组患者均于全身麻醉成功后取仰卧位,常规消毒铺巾,作胸部正中切口并劈开胸骨。切开心包并悬吊,肝素化后升主动脉、右心房二阶梯引流管插管建立体外循环,转机、降温,阻断循环,切开主动脉,探查主动脉瓣病变情况,剪除病变主动脉瓣,选择合适大小的人工主动脉瓣(机械瓣或生物瓣)进行置换,全周间断缝合。关闭主动脉切口。复温、排气,开放循环。并行稳定后停止体外循环,拔出动静脉管路。常规止血关胸,结束手术。统计患者术前各项资料中最可能影响术后房颤发生的因素[性别、年龄、体重指数、内皮素-1水平、基础疾病、美国纽约心脏病协会(NYHA)心功能分级、超声心动图指标]、术中资料(术中体外循环时间、主动脉阻断时间)及术后资料[术后机械通气时间、术后住院时间、行开胸止血术例数、使用何种类型人工瓣膜(机械瓣或生物瓣)]。数据比较采用t检验、非参数检验、χ²检验;通过受试者工作特征(ROC)曲线确定内皮素-1预测术后新发房颤的截断值;采用单因素和多因素Logistic回归分析与术后新发房颤相关的危险因素。 结果(1)术后房颤组患者的年龄为(53.0±12.1)岁,高于无术后房颤组[(47.1±13.6)岁],术前内皮素-1水平为0.43±0.19,高于无术后房颤组(0.27±0.14),NYHA分级≥3级患者比例为14.3%(4/28),高于无术后房颤组[4.4%(4/91)],左心房直径为(40.6±4.8) mm,大于无术后房颤组[(36.7±5.2 ) mm],主动脉瓣狭窄患者比例为39.3%(11/28),低于无术后房颤组[60.4%(55/91)],2组比较差异均有统计学意义(P<0.05);其他术前资料比较差异均无统计学意义(P>0.05)。(2)术后房颤组患者术中体外循环时间为(113.9±41.7) min,主动脉阻断时间为(75.3±24.1) min,无术后房颤组患者术中体外循环时间为(108.6±46.3) min,主动脉阻断时间为(72.5±31.4) min,2组比较差异均无统计学意义(t＝－0.547、－0.432,P＝0.59、0.67)。(3)术后房颤组患者术后机械通气时间、术后住院时间分别为(24.7±14.3) h、(9.1±3.6) d,均大于无术后房颤组[(19.6±9.5) h、(7.6±2.9) d];置换机械瓣患者比例为85.7%(24/28),低于无术后房颤组[96.7%(88/91)],置换生物瓣膜患者比例为14.3%(4/28),高于无术后房颤组[3.3%(3/91)],2组比较差异均有统计学意义(P<0.05);术后房颤组患者术后行开胸止血术的比例为3.6%(1/28),高于无术后房颤组[2.2%(2/91)],2组比较差异无统计学意义(P>0.05)。(4)采用ROC曲线对内皮素-1预测术后新发房颤的价值进行分析可得,曲线下面积为0.76,95%CI：0.66～0.85,截断值0.265 pmol/L,特异度0.75,敏感度0.63。根据截断值将患者分为内皮素-1>0.265组(n＝55)和内皮素-1<0.265组(n＝64),对2组患者术前、术中资料和术后资料进行比较,结果可得内皮素-1>0.265组患者左心房直径大于内皮素-1<0.265组患者,主动脉瓣狭窄患者比例低于内皮素-1<0.265组患者,术后新发房颤的发生率(38.2%)明显高于内皮素-1<0.265组(10.9%),差异均有统计学意义(P<0.05),其他各项比较差异均无统计学意义(P>0.05)。对收集到的患者资料进行单因素Logistic回归分析,发现年龄、NYHA分级≥3级、左心房直径、主动脉瓣狭窄、术后机械通气时间、置换生物瓣及内皮素-1>0.265 pmol/L均与术后新发房颤的发生相关;对以上指标进行多因素Logistic回归分析结果可得左心房直径、置换生物瓣和内皮素-1>0.265 pmol/L与患者术后新发房颤的发生呈独立相关。 结论在单纯行单纯主动脉瓣置换术的患者中,除左心房直径、置换生物瓣外,较高的内皮素-1水平也是患者发生术后新发房颤的独立危险因素。     

Simultaneous papillary fibroelastomas of the pulmonary and aortic valves

Cardiac papillary fibroelastomas (PFEs) are uncommon valve tumors. Multiple PFEs at the same or different locations in the heart account for less than 10% of patients with PFE. We herein describe a case of an asymptomatic PFE of both pulmonary and aortic valves which was incidentally diagnosed by echocardiography in a 60-year-old woman. Both PFEs were removed surgically without valve replacement. To our knowledge, this combination of lesions has not been previously reported. Even though PFEs are classified as benign cardiac tumors, they can present serious complications, such as embolic episodes, mechanical obstruction or valvular dysfunction. Valve-sparing shave excision of the lesions can be readily accomplished in most instances with good long-term results. All surgically removed valvular lesions should be histopathologically examined to confirm the echocardiographic diagnosis.     

Incidental in vivo detection of an isolated hemangioma of the aortic valve in a man with a history of renal transplantation

Hemangiomas of the cardiac valves are exceptional. To our knowledge, only ten cases of valve hemangiomas, six in the mitral and four in the tricuspid valve, have been reported in the English literature. We describe an incidentally detected aortic valve hemangioma of a 62-year-old man with chronic, degenerative aortic valve stenosis, who underwent renal transplantation 7 years before. We believe that this is the first report of a hemangioma in this localization and the first one in association with solid organ transplantation. The review of the literature of the adult cases of valve hemangioma, including this report, revealed that the average age was 47.2 years (range, 24 to 68 years). No clear sex predominance has been noted. Patients can be asymptomatic or experience sudden death. Symptomatic patients have complaints of palpitations, dyspnea, or syncopal episodes. Histologically, these valve tumors are classified as capillary, cavernous, and mixed. Mean tumor size is 1.1 cm (range, 0.6 to 2 cm). In 50% of cases the hemangioma is an incidental finding at autopsy or in a removed valve. Valve aortic hemangioma, despite its rarity, should be considered in the differential diagnosis of vascular lesions of this cardiac valve.     

Interaction between the aortic valve leaflets and a Millar dual-micromanometer catheter during recording of the aortic component of the second heart sound in dogs

The influence of the closure of the aortic valve leaflets on a dual-micromanometer Millar catheter is investigated with respect to the power spectrum of the aortic component (A2) of the second heart sound in dogs. The catheter inserted through the aortic valve is used to simultaneously record A2 in the left ventricle and in the aorta and to study the transmission of A2 up to the body surface. Results indicate that the interaction of the valve leaflets with the Millar dual-micromanometer catheter during the closure and vibration of the aortic valve does not produce a clapping artefact. The main effect is a change in the natural modes of vibration (resonant frequencies) of the aortic valve resulting from a modification of the vibrating structure (combined structure composed of the catheter, the aortic valve and the surrounding blood and tissues) because of the tight mechanical coupling between the aortic valve leaflets and the catheter. In addition, this modification of the natural modes of resonance does not invalidate the estimation of the frequency response of the transfer function between the aortic root and the thoracic recording site, even if the mean gain of the transfer function is affected and the phase slightly increased with frequency. On the contrary, the interaction of the aortic valve leaflets with the catheter seems to slightly increase the spectral contribution (coherence) of the intra-aortic A2 to the thoracic A2.     

Effects of decellularization on the mechanical and structural properties of the porcine aortic valve leaflet

The potential for decellularized aortic heart valves (AVs) as heart valve replacements is based on the assumption that the major cellular immunogenic components have been removed, and that the remaining extracellular matrix (ECM) should retain the necessary mechanical properties and functional design. However, decellularization processes likely alter the ECM mechanical and structural properties, potentially affecting long-term durability. In the present study, we explored the effects of an anionic detergent (sodium dodecyl sulfate (SDS)), enzymatic agent (Trypsin), and a non-ionic detergent (Triton X-100) on the mechanical and structural properties of AV leaflets (AVLs) to provide greater insight into the initial functional state of the decellularized AVL. The overall extensibility represented by the areal strain under 60 N/m increased from 68.85% for the native AV to 139.95%, 137.51%, and 177.69% for SDS, Trypsin, and Triton X-100, respectively, after decellularization. In flexure, decellularized AVLs demonstrated a profound loss of stiffness overall, and also produced a nonlinear moment-curvature relation compared to the linear response of the native AVL. Effective flexural moduli decreased from 156.0+/-24.6 kPa for the native AV to 23.5+/-5.8, 15.6+/-4.8, and 19.4+/-8.9 kPa for SDS, Trypsin, and Triton X-100 treated leaflets, respectively. While the overall leaflet fiber architecture remained relatively unchanged, decellularization resulted in substantial microscopic disruption. In conclusion, changes in mechanical and structural properties of decellularized leaflets were likely associated with disruption of the ECM, which may impact the durability of the leaflets.     

Diagnosing aortic valve stenosis by correlation analysis of wavelet filtered heart sounds

Traditional auscultation performed by the general practitioner remains problematic and often gives significant results only in a late stage of heart valve disease. Valve stenoses and insufficiencies are nowadays diagnosed with accurate but expensive ultrasonic devices. This studyaimed to develop a new heart sound analysis method for diagnosing aortic valve stenoses (AVS) based on a wavelet and correlation technique approach. Heart sounds recorded from 373 patients (107 AVS patients, 61 healthy controls (REF) and 205 patients with other valve diseases (OVD)) with an electronic stethoscope were wavelet filtered, and envelopes were calculated. Three correlations on the basis of these envelopes were performed: within the AVS group, between the groups AVS and REF and between the groups AVS and OVD, resulting in the mean correlation coefficients r_AVS, r_AVSv.REF and r_AVSv.OVD. These results showed that r_AVS (0.783±0.097) is significantly higher (p<0.0001) than r_AVSv.REF (0.590±0.056) and r_AVSv.OVD (0.516±0.056), leading to a highly significant discrimination between the groups. The wavelet and correlation-based heart sound analysis system should be useful to general practitioners for low-cost, easy-to-use automatic diagnosis of aortic valve stenoses.     

Subjects with familial hypercholesterolemia have lower aortic valve area and higher levels of inflammatory biomarkers

BackgroundReduction of the aortic valve area (AVA) may lead to aortic valve stenosis with considerable impact on morbidity and mortality if not identified and treated. Lipoprotein (a) [Lp(a)] and also inflammatory biomarkers, including platelet derived biomarkers, have been considered risk factor for aortic stenosis; however, the association between Lp(a), inflammatory biomarkers and AVA among patients with familial hypercholesterolemia (FH) is not clear.ObjectiveWe aimed to investigate the relation between concentration of Lp(a), measurements of the aortic valve including velocities and valve area and circulating inflammatory biomarkers in adult FH subjects and controls.MethodsIn this cross-sectional study aortic valve measures were examined by cardiac ultrasound and inflammatory markers were analyzed in non-fasting blood samples. The study participants were 64 FH subjects with high (n = 29) or low (n = 35) Lp(a), and 14 healthy controls.ResultsAortic valve peak velocity was higher (p = 0.02), and AVA was lower (p = 0.04) in the FH patients compared to controls; however, when performing multivariable linear regression, there were no significant differences. Furthermore, there were no significant differences between the high and low FH Lp(a) groups regarding the aortic valve. FH subjects had higher levels of platelet-derived markers CD40L, PF4, NAP2 and RANTES compared to controls (0.003 ≤ P ≤ 0.03). This result persisted after multiple linear regression.ConclusionsMiddle-aged, intensively treated FH subjects have higher aortic valve velocity, lower AVA, and higher levels of the platelet-derived markers CD40L, PF4, NAP2 and RANTES compared to healthy control subjects. The aortic valve findings were not significant after multiple linear regression, whereas the higher levels of platelet-derived markers were maintained.     

Presence of a smooth muscle system in aortic valve leaflets

Summary The location and the spatial arrangement of smooth muscle cells in aortic valves have been assessed by a systematic analysis of serial semithin sections of plastic embedded porcine and human aortic leaflets, combined with an electron microscope study.The investigation showed that smooth muscle cells, either single and arranged in thin bundles, and other cell types such as myofibroblasts are constantly present in the aortic valve leaflets. In addition, it was possible to devise a model of the three dimensional, specific organization of the smooth muscle bundles which can be interpreted as an intrinsic muscle system of the leaflets. As the muscular elements might play an active role in the normal functioning of the valve, their presence should be taken into account in designing (bio) prosthetic leaflets and in the evaluation of valve pathology.This work was supported by grant CT76 01159904 from CNR (Rome)     

Prevalence of pannus formation after aortic valve replacement: clinical aspects and surgical management

Pannus formation after aortic valve replacement is not common, but obstruction due to chronic pannus is one of the most serious complications of valve replacement. The causes of pannus formation are still unknown and effective preventive methods have not been fully elucidated. We reviewed our clinical experience of all patients who underwent reoperation for prosthetic aortic valve obstruction due to pannus formation between 1973 and 2004. We compared the initial 18-year period of surgery, when the Björk–Shiley tilting-disk valve was used, and the subsequent 13-year period of surgery, when the St. Jude Medical valve was used. Seven of a total of 390 patients (1.8%) required reoperation for prosthetic aortic valve obstruction due to pannus formation. All seven patients were women; four patients underwent resection of the pannus and three patients needed replacement of the valve. The frequency of pannus formation in the early group was 2.4% (6/253), whereas it was 0.73% (1/137) in the late group (P < 0.05). Pannus was localized at the minor orifice of the Björk–Shiley valve in the early group and turbulent transvalvular blood flow was considered to be one of the important factors triggering its growth. We also consider that small bileaflet valves have the possibility of promoting pannus formation and that the implantation of a larger prosthesis can contribute to reducing the occurrence of pannus.