Function of the left cardiac ventricle in "pure" aortic insufficiency prior to and following valve replacement with a biological prosthesis

Contractibility of the left ventricle was investigated in 15 patients with chronic aortic insufficiency with class II and III NYHA lesions. The patients were examined prior to and 6 months-2 years after valve replacement with biological prosthesis. The following parameters have been determined: end-systolic and end-diastolic left ventricular volumes, ejection fraction, mean rate of circular muscle fibers shortening, and segmental contractibility of the left ventricle. Valve replacement with biological prosthesis improved contract ability of the left ventricle in the great majority of the operated patients with chronic aortic insufficiency. Assessed parameters did not correlate well with those obtained following valve replacement.     

Left ventricular function early after aortic valve replacement for aortic regurgitation: Assessment by gated radionuclide ventriculography

This study characterizes left ventricular performance early after aortic valve replacement for severe isolated aortic regurgitation. Gated radionuclide ventriculography studies in 13 patients showed that left ventricular end-diastolic volume was reduced after surgery and that ejection fraction dropped significantly. Despite the fall in ejection fraction, the postoperative cardiac index was significantly greater than the preoperative value. Radionuclide ventriculography is a useful and reliable means of noninvasively assessing left ventricular function soon after aortic valve replacement for aortic regurgitation.     

Uncommon acquired Gerbode defect following extensive bicuspid aortic valve endocarditis

Gerbode defect is a rare type of left ventricle to right atrium shunt. It is usually congenital in origin, but acquired cases are also described, mainly following infective endocarditis, valve replacement, trauma or acute myocardial infarction. We report a case of a 50-year-old man who suffered an extensive and complex infective endocarditis involving a bicuspid aortic valve, the mitral-aortic intervalvular fibrosa and the anterior leaflet of the mitral valve. After dual valve replacement and annular reconstruction, a shunt between the left ventricle and the right atrium - Gerbode defect, and a severe leak of the mitral prosthesis were detected. Reintervention was performed with successful shunt closure with an autologous pericardial patch and paravalvular leak correction. No major complications occurred denying the immediate post-surgery period and the follow-up at the first year was uneventful.     

An approach to the simulation of fluid-structure interaction in the aortic valve

A pair of finite element models has been employed to study the interaction of blood flow with the operation of the aortic valve. A three-dimensional model of the left ventricle with applied wall displacements has been used to generate data for the spatially and time-varying blood velocity profile across the aortic aperture. These data have been used as the inlet loading conditions in a three-dimensional model of the aortic valve and its surrounding structures. Both models involve fluid-structure interaction and simulate the cardiac cycle as a dynamic event. Confidence in the models was obtained by comparison with data obtained in a pulse duplicator. The results show a circulatory flow being generated in the ventricle which produces a substantially axial flow through the aortic aperture. The aortic valve behaves in an essentially symmetric way under the action of this flow, so that the pressure difference across the leaflets is approximately uniform. This work supports the use of spatially uniform but temporally variable pressure distributions across the leaflets in dry or structural models of aortic valves. The study is a major advance through its use of truly three-dimensional geometry, spatially non-uniform loading conditions for the valve leaflets and the successful modelling of progressive contact of the leaflets in a fluid environment.     

Dynamics of left ventricular wall and mitral valve mechanics--a model study

The relation between global left ventricular pumping characteristics and local cardiac muscle fiber mechanics is represented by a mathematical model of left ventricular mechanics in which the mitral valve papillary muscle system is incorporated. The wall of the left ventricle is simulated by a thick-walled cylinder. Transmural differences in fiber orientation are incorporated by changing the direction of material anisotropy across the wall. The cylinder is free to twist. The upper end of the cylinder is covered by a thin, flexible sheet, representing the base of the left ventricle. The mitral valve is incorporated in this sheet. The tips of the mitral leaflets are connected by chordae tendineae to the papillary muscles which are attached to the bottom of the cylinder. Canine cardiac cycles were simulated for various end-diastolic values of left ventricular volume (25-120 ml, control 60 ml), left atrial pressure (0-2.7 kPa, control 0.22 kPa) and aortic pressure (5-11 kPa, control 11 kPa). In this wide range of preload and afterload mechanical loading of the muscle fibers appeared to be distributed quite evenly (SD: +/- 5% of control value) over all muscular structures of the left ventricle, including the papillary muscles.     

Transmural gradients of cardiac myofiber shortening in aortic valve stenosis patients using MRI tagging

Aortic valve stenosis impairs subendocardial perfusion with a risk of irreversible subendocardial tissue damage. A likely precursor of damage is subendocardial contractile dysfunction, expressed by the parameter TransDif, which is defined as epicardial minus endocardial myofiber shortening, normalized to the mean value. With the use of magnetic resonance tagging in two short-axis slices of the left ventricle (LV), TransDif was derived from LV torsion and contraction during ejection. TransDif was determined in healthy volunteers (control, n = 9) and in patients with aortic valve stenosis before (AVSten, n = 9) and 3 mo after valve replacement (AVRepl, n = 7). In the control group, TransDif was 0.00 +/- 0.14 (mean +/- SD). In the AVSten group, TransDif increased to 0.96 +/- 0.62, suggesting impairment of subendocardial myofiber shortening. In the AVRepl group, TransDif decreased to 0.37 +/- 0.20 but was still elevated. In eight of nine AVSten patients, the TransDif value was elevated individually (P < 0.001), suggesting that the noninvasively determined parameter TransDif may provide important information in planning of treatment of aortic valve stenosis.     

Mitral valve prolapse detected during hemodynamic studies

To estimate frequency of the posterior mitral valve leaflet prolapse in routinely performed left ventriculography, 1000 consecutive ventriculograms of the right anterior oblique projection were analyzed. A group of patients consisted of 511 women and 489 men at mean age 46,5 years. Clinical diagnosis of heart lesions, myocardial disease, pulmonary hypertension or arrhythmias were indications for hemodynamic studies. In the investigated group of patients, there were no patients with clinical diagnosis of the coronary artery disease. Prolapse of the posterior mitral valve leaflet was diagnosed in 59 patients. Idiopathic mitral valve prolapse was diagnosed in 10 patients. Prolapse of the posterior mitral valve leaflet was most frequent in atrial septal defect (16.6%), myocardial lesion (12.5%), and after mitral commissurotomy (8.9%). Posterior mitral valve leaflet prolapse is not a frequent anomaly in routinely performed left ventriculography. Relatively often occurrence of the mitral valve prolapse in atrial septal defect and only occasional in the aortic lesions and dilated cardiomyopathy seems to point out at a role of the left ventricle size in pathogenesis of this syndrome.     

Exuberant accessory mitral valve tissue with possible true parachute mitral valve: a case report

ABSTRACT: INTRODUCTION: A parachute mitral valve is defined as a unifocal attachment of mitral valve chordae tendineae independent of the number of papillary muscles. Data from the literature suggests that the valve can be distinguished on the basis of morphological features as either a parachute-like asymmetrical mitral valve or a true parachute mitral valve. A parachute-like asymmetrical mitral valve has two papillary muscles; one is elongated and located higher in the left ventricle. A true parachute mitral valve has a single papillary muscle that receives all chordae, as was present in our patient. Patients with parachute mitral valves during childhood have multilevel left-side heart obstructions, with poor outcomes without operative treatment. The finding of a parachute mitral valve in an adult patient is extremely rare, especially as an isolated lesion. In adults, the unifocal attachment of the chordae results in a slightly restricted valve opening and, more frequently, valvular regurgitation. CASE PRESENTATION: A 40-year-old Caucasian female patient was admitted to a primary care physician due to her recent symptoms of heart palpitation and chest discomfort on effort. Transthoracic echocardiography showed chordae tendineae which were elongated and formed an unusual net shape penetrating into left ventricle cavity. The parasternal short axis view of her left ventricle showed a single papillary muscle positioned on one side in the posteromedial commissure receiving all chordae. Her mitral valve orifice was slightly eccentric and the chordae were converting into a single papillary muscle. Mitral regurgitation was present and it was graded as moderate to severe. Her left atrium was enlarged. There were no signs of mitral stenosis or a subvalvular ring. She did not have a bicuspid aortic valve or coarctation of the ascending aorta. The dimensions and systolic function of her left ventricle were normal. Our patient had a normal body habitus, without signs of heart failure. Her functional status was graded as class I according to the New York Heart Association grading. CONCLUSIONS: A recently published review found that, in the last several decades, there have been only nine adult patients with parachute mitral valve disease reported, of which five had the same morphological characteristics as our patient. This case presentation should encourage doctors, especially those involved in echocardiography, to contribute their own experience, knowledge and research in parachute mitral valve disease to enrich statistical and epidemiologic databases and aid clinicians in getting acquainted with this rare disease.     

Undiagnosed hypertrophic obstructive cardiomyopathy during transcatheter aortic valve replacement: a case report

Background

Transcatheter aortic valve replacement is indicated for severe symptomatic aortic stenosis in patients who have a very high or prohibitive surgical risk as assessed pre-procedurally by the Society of Thoracic Surgery Risk Score, EuroSCORE (II), frailty testing, and other predictors. When combined with another left ventricular outflow tract obstruction, careful consideration must be taken prior to proceeding with transcatheter aortic valve replacement because an additional masked left ventricular outflow tract pathology can lead to challenging hemodynamics in the peri-deployment phase, as reported in this case.

Case presentation

A 56-year-old Caucasian man with multiple comorbidities and severe aortic stenosis underwent transcatheter aortic valve replacement under monitored anesthesia care. During the deployment phase, he developed dyspnea that progressed to pulmonary edema requiring emergent conversion to general anesthesia, orotracheal intubation, acute respiratory distress syndrome-type ventilation, and vasopressor medications. Intraoperative transesophageal echocardiography was performed and hypertrophic obstructive cardiomyopathy with systolic anterior motion of the mitral valve was discovered as an underlying pathology, undetected on preoperative imaging. After treatment with beta blockers, fluid resuscitation, and alpha-1 agonists, he stabilized and was eventually discharged from our hospital without any lasting sequelae.

Conclusions

Patients with aortic stenosis most often develop symmetric hypertrophy; however, a small subset has asymmetric septal hypertrophy leading to left ventricular outflow tract obstruction. In cases of severe aortic stenosis, however, evidence of left ventricular outflow tract obstruction via both symptoms and echocardiographic findings may be minimized due to extremely high afterload on the left ventricle. Diagnosing a left ventricular outflow tract obstruction as the cause of hemodynamic instability during transcatheter aortic valve replacement, in the absence of abnormal findings on echocardiogram preoperatively, requires a high index of clinical suspicion. The management of acute onset left ventricular outflow tract obstruction intraoperatively consists primarily of medical therapy, including rate control, adequate volume resuscitation, and avoidance of inotropes. With persistently elevated gradients, interventional treatments may be considered.

     

A method for the measurement of left ventricular overload for aortic valve insufficiency

BackgroundThe degree of left ventricular overload in patients with aortic valve insufficiency (AI) plays an important role in determining the need and timing of surgical intervention. Because hemodynamic evaluation of AI may potentially predict the effects of an insufficient valve on the ventricle before they occur, it would be useful to guide valve surgery with such a diagnostic tool. The purpose of this study was to test the performance of a new hemodynamic index based on mechanical energy loss for the measurement of the effects of insufficiency on ventricular workload.Methods and resultsAn intact and subsequently perforated aortic bioprosthesis was tested within an in vitro model of the left heart, varying cardiac output, diastolic aortic pressure, and the size of perforation. Regurgitant orifice area (ROA), regurgitant volume (RV), regurgitant fraction (RF), and energy loss index (ELI) were measured for each experimental condition and plotted against the increase in workload per unit volume net forward flow (ΔWPV) due to perforation. ROA, RV, and RF showed good correlations with ΔWPV, but the relationship between these variables and ΔWPV became ambiguous as their magnitudes increased. ELI had a near perfect linear relationship with ΔWPV (slope=1.00, r²=0.98) independent of the experimental condition.ConclusionsRV, RF, and ROA do not by themselves fully describe the increase in difficulty the ventricle has in moving the blood across an insufficient valve. ELI, in contrast, was found to be a very good measure of the decrease in pump efficiency due to aortic valve insufficiency.     

Intracardiac echocardiographic guidance for hemodynamic assessment in a patient with congenital abnormalities and a prosthetic aortic valve

In this case report, we present the use of intracardiac echocardiography (ICE) for guiding the cardiac catheterization and subsequent hemodynamic investigation in an unusual patient case with multiple congenital abnormalities (bicuspid aortic valve, left cervical aortic arch, two aortic coarctations) and two aortic valve replacement operations in the past. The ICE catheter (AcuNav) permitted us to accurately and safely puncture the interatrial septum and place the Swan-Ganz catheter in the left ventricle; additionally, visualization of the aortic coarctation in the ascending aorta was also achieved.     

Respective impacts of aortic stenosis and systemic hypertension on left ventricular hypertrophy

It has been reported that 30-40% of patients with aortic stenosis are hypertensive. In such patients, the left ventricle faces a double (i.e. valvular and vascular) pressure overload, which results in subsequent wall volume hypertrophy. From a clinical standpoint, it is difficult to separate the respective contributions of aortic stenosis and systemic hypertension to left ventricular burden and patient's symptoms and thus to predict whether valve replacement would be beneficial. The objective of this theoretical study was therefore to investigate the relative effects of valvular and vascular afterloads on left ventricular hypertrophy. We used a ventricular-valvular-vascular mathematical model in combination with the Arts' model describing the myofiber stress. Left ventricular wall volume was computed for different aortic blood pressure levels and different degrees of aortic stenosis severity. Our simulations show that the presence of concomitant systemic hypertension has a major influence on the development of left ventricular hypertrophy in patients with aortic stenosis. These results also suggest that mild-to-moderate aortic stenosis has a minor impact on left ventricular wall volume when compared with hypertension. On the other hand, when aortic stenosis is severe, wall volume increases exponentially with increasing aortic stenosis severity and the impact of aortic stenosis on left ventricular hypertrophy becomes highly significant.     

二尖瓣置换术后左心室破裂2例并文献复习

目的：总结二尖瓣置换术后左心室破裂2例临床经验教训,方法：回顾性分析我院2006,1．2009,12二尖瓣置换术后左心室破裂2例的临床资料,两例均在监护室里发生突然大出血,紧急输血,输液,机械呼吸,抗休克治疗,并行开胸手术。结果：一例心外修补抢救成功,术后2周顺利出院,一例CPB下心内外修补,因低心排综合症死亡。结论：左心室破裂是二尖瓣置换术最严重的并发症,一旦发生死亡率极高,因此预防,避免其相关因素更关键：     

"Ring pledget": a new concept for secure apex closure during transapical aortic valve implantation

Transapical aortic valve implantation requires puncture of the left ventricle apex and insertion of a 32-French delivery sheath. A critical step in the procedure consists of secure closure of the ventricular apex. We describe 2 cases of apical rupture of 42 transapical aortic valve implantations. Furthermore, we describe the use of a newly designed single circular Teflon pledget that can help to avoid this complication. This pledget provides a more secure and uniform shrinkage of the entire apex to close the defect left by the delivery sheath.     

Raloxifene attenuates Gas6 and apoptosis in experimental aortic valve disease in renal failure

Renal failure is associated with aortic valve calcification. Using our rat model of uremia-induced reversible aortic valve calcification, we assessed the role of apoptosis and survival pathways in that disease. We also explored the effects of raloxifene, an estrogen receptor modulator, on valvular calcification. Gene array analysis was performed in aortic valves obtained from three groups of rats (n = 7 rats/group): calcified valves obtained from rats fed with uremic diet, valves after calcification resolution following diet cessation, and control. In addition, four groups of rats (n = 10 rats/group) were used to evaluate the effect of raloxifene in aortic valve calcification: three groups as mentioned above and a fourth group fed with the uremic diet that also received daily raloxifene. Evaluation included imaging, histology, and antigen expression analysis. Gene array results showed that the majority of the altered expressed genes were in diet group valves. Most apoptosis-related genes were changed in a proapoptotic direction in calcified valves. Apoptosis and decreases in several survival pathways were confirmed in calcified valves. Resolution of aortic valve calcification was accompanied by decreased apoptosis and upregulation of survival pathways. Imaging and histology demonstrated that raloxifene significantly decreased aortic valve calcification. In conclusion, downregulation of several survival pathways and apoptosis are involved in the pathogenesis of aortic valve calcification. The beneficial effect of raloxifene in valve calcification is related to apoptosis modulation. This novel observation is important for developing remedies for aortic valve calcification in patients with renal failure.     

Coronary artery anomalies and aortic valve morphology in the Syrian hamster

In the Syrian hamster, anomalies in the origin of the left coronary artery are significantly associated with the bicuspid condition of the aortic valve. In this species, bicuspid aortic valves are expressions of a trait, the variation of which takes the form of a phenotypic continuum, ranging from a tricuspid aortic valve with no commissural fusion to a bicuspid aortic valve with the aortic sinuses located in ventrodorsal orientation and devoid of any raphe. The intermediate stages of the continuum are represented by tricuspid aortic valves with a more or less extensive fusion of the ventral commissure and bicuspid aortic valves with a more or less developed raphe located in the ventral aortic sinus. The present study was designed to decide whether there is a gap between tricuspid and bicuspid aortic valves regarding the incidence of coronary artery anomalies, or whether this incidence varies according to the different tricuspid and bicuspid morphotypes of the continuum. The study was carried out in Syrian hamsters belonging to a single inbred family with a high incidence of tricuspid aortic valves with fusion of the ventral commissure, bicuspid aortic valves, and anomalies in the origin of the left coronary artery, i.e. single right coronary artery ostium in aorta, anomalous origin of the left coronary artery from the pulmonary artery, and anomalous origin of the left coronary artery from the dorsal aortic sinus. The specimens were examined by means of a stereomicroscope and, in several cases, scanning electron microscopy was also used. The relationships between anomalous coronary artery patterns and aortic valve morphologies were tested using a logistic regression model. The results obtained indicate that there is no discontinuity between tricuspid and bicuspid aortic valves regarding the incidence of coronary artery anomalies. The probability of occurrence of anomalous coronary artery patterns increases continuously according to the deviation degree of the aortic valve from its normal (tricuspid) design. The present findings suggest that in the Syrian hamster, the morphogenetic mechanisms involved in the formation of congenital anomalous aortic valves and anomalies in the origin of the left coronary artery, respectively, are strongly related from an aetiological viewpoint.     

A ventricular-vascular coupling model in presence of aortic stenosis

In patients with aortic stenosis, the left ventricular afterload is determined by the degree of valvular obstruction and the systemic arterial system. We developed an explicit mathematical model formulated with a limited number of independent parameters that describes the interaction among the left ventricle, an aortic stenosis, and the arterial system. This ventricular-valvular-vascular (V(3)) model consists of the combination of the time-varying elastance model for the left ventricle, the instantaneous transvalvular pressure-flow relationship for the aortic valve, and the three-element windkessel representation of the vascular system. The objective of this study was to validate the V(3) model by using pressure-volume loop data obtained in six patients with severe aortic stenosis before and after aortic valve replacement. There was very good agreement between the estimated and the measured left ventricular and aortic pressure waveforms. The total relative error between estimated and measured pressures was on average (standard deviation) 7.5% (SD 2.3) and the equation of the corresponding regression line was y = 0.99x - 2.36 with a coefficient of determination r(2) = 0.98. There was also very good agreement between estimated and measured stroke volumes (y = 1.03x + 2.2, r(2) = 0.96, SEE = 2.8 ml). Hence, this mathematical V(3) model can be used to describe the hemodynamic interaction among the left ventricle, the aortic valve, and the systemic arterial system.     

Medium-term cardiovascular effects of high-dose growth hormone treatment in growth hormone-deficient children

AIM: To investigate the possible cardiac morphofunctional alterations inducd by prolonged and high-dose GH therapy in a group of 14 children with isolated GH deficiency. PATIENTS AND METHODS: Patients were evaluated at phase 1, after 1.1 +/- 0.6 years of treatment with GH 0.93 +/- 0.13 U/kg/week, and at phase 2, after 5.5 +/- 2.1 years of therapy 0.89 +/- 0.11 U/kg/week. At each phase left ventricular volume, mass and systolic function were evaluated by two-dimensional guided M-mode echocardiography; left ventricular diastolic function was assessed by PW-Doppler sampling of transmitral flow. RESULTS: Phase 1: diastolic blood pressure was lower (p < 0.05) and fractional shortening was not adequate for the level of afterload (stress shortening index p < 0.05) in patients compared to controls. Phase 2: diastolic blood pressure was lower (p < 0.01) and mass and mass/volume ratio were increased (mass index p < 0.05, mass/ volume ratio p < 0.05) in patients compared to controls. The increased mass/volume ratio, together with the normal systolic blood pressure, explains the reduction in peak systolic stress (p < 0.005). Among the parameters of left ventricular diastolic function, the peak E velocity/total area under mitral valve tracing and the area under E velocity/total area under mitral value tracing ratios were significantly decreased (p < 0.05). CONCLUSION: After a mean period of 5 years on high-dose GH treatment in GH-deficient children, subclinical morphofunctional alterations in the left ventricle were found.     

Assessment of valve implantation in the descending aorta as an alternative for aortic regurgitation patients not treatable with conventional procedures

Background:

Aortic Regurgitation (AR) produces the entrance of an abnormal amount of blood in the left ventricle. This disease is responsible for high morbidity and mortality worldwide and may be caused by an aortic valve dysfunction. Surgical and transcatheter aortic valve replacement (TAVR) are the current options for treating AR. They have replaced older procedures such as Hufnagel’s one. However, some physicians have reconsidered this procedure as a less aggressive alternative for patients not eligible for surgical or TAVR. Although Hufnagel suggested a 75% regurgitation reduction when a valve is placed in the descending aorta, a quantification of this value has not been reported.

Methods:

In this paper, CFD/FSI numerical simulation is conducted on an idealized geometry. We quantify the effect of placing a bileaflet mechanical heart valve in the descending aorta on a moderate-severe AR case. A three-element Windkessel model is employed to prescribe pressure outlet boundary conditions. We calculate the resulting flow rates and pressures at the aorta and first-generation vessels. Moreover, we evaluate several indices to assess the improvement due to the valve introduction.

Results and conclusions:

Regurgitation fraction (RF) is reduced from 37.5% (without valve) to 18.0% (with valve) in a single cardiac cycle. This reduction clearly shows the remarkable efficacy of the rescued technique. It will further ameliorate the left ventricle function in the long-term. Moreover, the calculations show that the implantation in that location introduces fewer incompatibilities’ risks than a conventional one. The proposed methodology can be extended to any particular conditions (pressure waveforms/geometry) and is designed to assess usual clinical parameters employed by physicians.

     

Patient-specific modeling of biomechanical interaction in transcatheter aortic valve deployment

The objective of this study was to develop a patient-specific computational model to quantify the biomechanical interaction between the transcatheter aortic valve (TAV) stent and the stenotic aortic valve during TAV intervention. Finite element models of a patient-specific stenotic aortic valve were reconstructed from multi-slice computed tomography (MSCT) scans, and TAV stent deployment into the aortic root was simulated. Three initial aortic root geometries of this patient were analyzed: (a) aortic root geometry directly reconstructed from MSCT scans, (b) aortic root geometry at the rapid right ventricle pacing phase, and (c) aortic root geometry with surrounding myocardial tissue. The simulation results demonstrated that stress, strain, and contact forces of the aortic root model directly reconstructed from MSCT scans were significantly lower than those of the model at the rapid ventricular pacing phase. Moreover, the presence of surrounding myocardium slightly increased the mechanical responses. Peak stresses and strains were observed around the calcified regions in the leaflets, suggesting the calcified leaflets helped secure the stent in position. In addition, these elevated stresses induced during TAV stent deployment indicated a possibility of tissue tearing and breakdown of calcium deposits, which might lead to an increased risk of stroke. The potential of paravalvular leak and occlusion of coronary ostia can be evaluated from simulated post-deployment aortic root geometries. The developed computational models could be a valuable tool for pre-operative planning of TAV intervention and facilitate next generation TAV device design.