Improved method for cardiac output determination in man using ultrasound Doppler technique

An existing ultrasound Doppler method for measuring cardiac output has been improved and refined, partly by locating the sampling volume higher up in the aorta while still using the aortic ring size as the effective transverse flow area. The basis for using this technique is the approximately rectangular systolic velocity profile in the aortic orifice in physiologically and anatomically normal subjects, and the fact that this profile velocity is conserved as the maximum velocity in the ascending aorta for some 3 to 4 cm above the valves. This higher location of the sampling volume improves Doppler signal quality, and does not reduce the accuracy of the method, as can be confirmed in each experimental subject. Together with automatic computer-based online signal analysis, the technique employed enables us to make continuous long-term beat-to-beat measurements of cardiac output in subjects without aortic valve disease or grossly deforming disease of the aortic root.     

Severe aortic valve stenosis in a 14-year-old boy with sitosterolemia

We report a 14-year-old boy finally diagnosed with sitosterolemia, presenting with severe aortic valve stenosis. Genetic analysis revealed homozygous null mutation c.1336 C > T (p.R446X) in ABCG5 gene. His cardiac ultrasound presented aortic valve stenosis and moderate aortic regurgitation. His whole aorta computed tomography angiogram scan revealed aortic stenosis superior to the aortic valve, followed by ascending aorta dilation, whereas his coronary and peripheral arteries appeared normal. His maximum total cholesterol and low-density lipoprotein-cholesterol levels dropped dramatically after diet control, and ezetimibe was prescribed for treatment. The current case indicated that sitosterolemia may be a heterogeneous disease in clinical phenotype.     

The bicuspid aortic valve and its relation to aortic dilation

BACKGROUND

A bicuspid aortic valve (BAV) is a common congenital heart disease, which affects 1–2% of the population. However, the relationship between BAVs and aortic dilation has not been sufficiently elucidated.

METHODS

A total of 241 BAV patients who were referred to this hospital for cardiac surgey over a 4.75-year period were included in this study. In addition to the clinical characteristics of the included patients, the morphological features of the aortic valve and aorta, the length of the left main coronary artery, and the laboratory findings (the coagulation and hematological parameters as well as the total cholesterol concentration) were determined and compared with those of the tricuspid aortic valve (TAV) patients.

RESULTS

The BAV patients were younger than the TAV patients for a valve surgery in the last 3 months of the study period. The BAV patients were predominantly male. Most of the BAVs that were surgically treated were stenotic, regurgitant, or combined, and only 19 (7.88%) were normally functioning valves. According to echocardiography or operative records, 148 (78.31%) were type A, 31 (16.40%) were type B, and 10 (5.29%) were type C. The left main coronary artery was much shorter in the BAV patients than it was in the TAV patients. There was no significant difference between BAV and TAV patients in the total cholesterol concentrations; whereas differences were noted between patients receiving lipid-lowering therapy and those not receiving lipid-lowering therapy. The dimensions of the aortic root, sinotubular junction, and ascending aorta were beyond normal limits, while they were significantly smaller in the BAV patients than in the TAV patients. They were also much smaller in patients receiving statin therapy than those not receiving statin therapy in both groups. Moreover, the aortic dilation in the BAV group was found to be significantly associated with patient age.

CONCLUSIONS

The BAV patients developed aortic wall and aortic valve disorders at a younger age than the TAV patients and were predominantly male. Aortic dilation was observed in the aortic root, sinotubular junction, and ascending aortic segments in both the BAV and TAV patients undergoing surgical aortic valve replacement, although the BAV patients had a smaller degree of dilation than the TAV patients, and dilation was also significantly age-related in this group. The shorter left main coronary artery that the BAV patients possess may contribute to the progressive course of aortic dilation that these patients experience. Statin therapy did not affect the aortic annulus in either group, but did decrease the dimensions of the aortic root, sinotubular junction and ascending aorta. In general, statin therapy had a better effect on the aortas of the TAV patients than it did on those of the BAV patients.     

A possible relation between pressure loading and thickened leaflets of the aortic valve: a model simulation

A much smaller percentage of thickened leaflets of the aortic valve have been found in the right or left coronary leaflet than in the noncoronary leaflet. This study investigated the pressure loading transferring to the leaflets of the aortic valve and their effects on the valvular thickening. A simple ascending aorta model was established, and a simulation was made. The pressure loading in the coronary and noncoronary leaflets then were estimated. The simulation results showed that 5.8% to 17.% percentage of pressure loading to the coronary leaflet may be decreased by the coronary perfusion in diastole. The coronary arteries play an important role on pressures in the sinuses of Valsalva. The smaller pressure loading transferring to the coronary leaflet than that to the noncoronary leaflet is one reasonable explanation related to the thickened leaflets of the aortic valve.     

Simulation of the fluid dynamics in artificial aortic roots: comparison of two different types of prostheses

As a consequence of the growing number of elderly people, the incidence of degenerative aortic diseases continues to increase. Often, artificial aortic roots are needed to replace the native tissue. Some physical characteristics of the artificial aortic root, however, are quite different from native aorta and need to be optimized. The supposed benefit of a prosthesis with artificial sinuses of Valsalva could first be checked by numerical calculations. Two simplified base geometries were used for simulating the flow and pressure distributions, especially in the coronary arteries. One model approximates the ascending aorta as a tube, and the other uses a design with toroidal dilation of the aortic root to approximate the native geometry of the sinuses of Valsalva. The flow and pressure distributions in both models were compared in the ascending aorta as well as in the right and the left coronary arteries. Both the pressure and the velocity distribution in the coronary artery region were not significantly higher in the model with the sinus design compared to the tube model. The sinus design only slightly increased the mean pressures and the velocities in both the ascending aorta and in the coronary arteries. Higher pressure in the coronary arteries should improve the blood circulation and decrease the risk of a surgery-related coronary incident. The sinus design did not show the hoped-for benefits, and therefore it is only a minor factor in optimizing future aortic root prostheses.     

A Study of Variations in Coronary Ostia

Introduction: The year 1928 saw the first human coronary angiograph when Werner Forssmann inserted a ureteral catheter into his left anticubital vein and advanced it to the heart. Today coronary angiographies and selective coronary angiographies are being done quite frequently. Presence of supernumerary ostia can make it difficult to correctly interpret angiographic films. Also during selective angiography such ostia are difficult to cannulate. The knowledge of position of coronary ostia with respect to aortic sinuses and possible variations in their locations will aid in carrying out these procedures as well as in interpreting them.High position of ostia in comparison to the aortic sinuses has been found to be related to poor filling of coronary arteries during diastole. The knowledge of position of ostia, could help in correct interpretation of patient's symptoms and could help in channalizing the further line of treatment.Aim: To study the variations in the number and position of coronary ostia in relation with aortic sinuses.Materials and Methods: A total of 50 human hearts were included in this study irrespective of sex. The hearts were procured from dissection room adult cadavers of Dr D Y Patil Medical College, Pune and were preserved in 10% formalin.The origins of both the coronary arteries were noted while looking out for presence of any extra ostia in either of the three aortic sinuses. Depending on whether the ostia were situated below, at or above the cuspal margin they were classified as those taking origin from the sinus, sinuaortic junction or ascending aorta.Results: In this study the ostium for right coronary artery was located in the anterior aortic sinus in 98% cases and in right posterior aortic sinus in 2% cases. The ostium for left coronary artery was located in the left posterior aortic sinus in 100% cases. The maximum height of ostium from the sinuaortic junction in case of coronary arteries taking origin directly from aorta was found to be 1.5mm.Regarding study of number of ostia found in the aortic sinuses-22% hearts showed presence of 2 ostia, 2% hearts showed 3 separate ostia and 2% hearts showed 5 ostia in the anterior aortic sinus region. No supernumerary ostia were found in the left posterior aortic sinus region. 2% incidence of circumflex artery taking origin from the anterior aortic sinus was observed.     

Finite element modeling of the thoracic aorta: including aortic root motion to evaluate the risk of aortic dissection

Objective: We propose that the aortic root motion plays an important role in aortic dissection.

Methods and results: A finite element model of the aortic root, arch and branches of the arch was built to assess the influence of aortic root displacement and pressure on the aortic wall stress. The largest stress increase due to aortic root displacement was found at approximately 2 cm above the top of the aortic valve. There, the longitudinal stress increased by 50% to 0.32 MPa when 8.9 mm axial displacement was applied in addition to 120 mmHg luminal pressure. A similar result was observed when the pressure load was increased to 180 mmHg without axial displacement.

Conclusions: Both aortic root displacement and hypertension significantly increase the longitudinal stress in the ascending aorta, which could play a decisive role in the development of various aortic pathologies, including aortic dissection.     

The positions of coronary arterial ostia

The positions of the coronary arterial ostia were examined in the cadavers of 38 adults. All the ostia were related to the aorta and none to the pulmonary artery. The aortic valves in 37 specimens were normal and possessed three cusps, while one was bicuspid. In the normal specimens, the main right and left coronary ostia were confined to the anterior and left posterior aortic sinuses respectively, apart from one specimen in which the right ostium was related to the right posterior sinus. Six specimens had small accessory ostia, close to the main right ostium. The majority of ostia were situated on or immediately below the supravalvular ridge. Circumferentially, the ostia clustered near the maximum curvature of the sinus. In the single specimen where the aortic valve was bicuspid, both ostia lay more-or-less symmetrically in the sinus above an anterior cusp which showed evidence of formation from two components. The reasons for confinement of the coronary ostia to only two of the three aortic sinuses are not clear. Microscopic examination of serial sections through 22 human embryos of 5.0–17.5 mm CR length (Carnegie stages XIII–XIX) confirmed that the earliest vessels in the heart wall develop subepicardially near the apex at stage XV. The network extends centripetally and only at stage XVII could coronary arterial stems, communicating with the aortic lumen, be identified. The sequence suggests that confinement of the coronary ostia to the anterior and left posterior sinuses probably occurs because these represent the most accessible contact points for the centripetally growing vascular plexus. © 1996 Wiley-Liss, Inc.     

Mechanical properties of dilated human ascending aorta

Dilation of the ascending aorta, associated with Marfan Syndrome, bicuspid aortic valve, or advanced age, may lead to aortic dissection and rupture. Mathematical models can be used to assess the relative importance of increased wall stresses and decreased strength in these mechanical failures. To obtain needed inputs for such models, mechanical properties of dilated human ascending aorta were measured in vitro. Specimens for opening angle, biaxial elastic, and uniaxial circumferential strength tests were cut from excised tissue obtained from 54 patients (age 18–81 years) undergoing elective aortic graft replacement surgery. Opening angle was significantly greater in patients older than 50 years (262°±76°, n=21) compared to younger patients (202°±70°, n=13 All biaxial elastic specimens n=40 exhibited nonlinear stress-strain behavior. Rapid increases in circumferential and axial stresses occurred at lower strains in the older patient group than in the younger. Mean strength was significantly lower in older patients (1.35±0.37 MPa, n=14) than younger (2.04 ± 0.46 MPa, n=11, age <50 years). These changes in mechanical properties suggest that age may influence the risk of aortic dissection or rupture of dilated ascending aorta. © 2002 Biomedical Engineering Society. PAC2002: 8719Rr, 8719Hh     

Origins of the Coronary Arteries and Their Significance

OBJECTIVE:

To describe the normal and variant anatomy of the coronary artery ostia in Indian subjects.

INTRODUCTION:

Anomalous coronary origins may cause potentially dangerous symptoms, and even sudden death during strenuous activity. A cadaveric study in an unsuspected population provides a basis for understanding the normal variants, which may facilitate determination of the prevalence of anomalies and evaluation of the value of screening for such anomalies.

METHODS:

One hundred and five heart specimens were dissected. The number of ostia and their positions within the respective sinuses were observed. Vertical and circumferential deviations of the ostia were observed. The heights of the cusps and the ostia from the bottom of the sinus were measured.

RESULTS:

No openings were present in the pulmonary artery or the non-coronary sinus. The number of openings in the aortic sinuses varied from 2–5 in the present series; multiple ostia were mostly seen in the anterior sinus. The majority of the ostia lay below the sinutubular ridge (89%) and at or above the level of the upper margin of the cusps (84%). Left ostial openings were mainly centrally located (80%), whereas the right coronary ostia were often shifted towards the right posterior aortic sinus (59%).

DISCUSSION:

The preferential location of the ostia was within the sinus and above the cusps, but below the sinutubular ridge. On occasion, normal variants like multiple ostia, vertical or circumferential shift in the position, and slit-like ostia may create confusion in interpreting the images and pose a difficulty during procedures like angiography, angioplasty, and coronary artery bypass grafting.     

Severe valvular and aortic arch calcification in a patient with Gaucher's disease homozygous for the D409H mutation

Gaucher's disease is an autosomal recessive inherited defect of the lysosomal enzyme glucocerebrosidase, which leads to glucocerebroside accumulation in the reticuloendothelial system. Homozygosity for the D409H mutation has been associated with cardiovascular valvular disease. We present a case of a 17-year-old Palestinian patient who presented with severe aortic and mitral valvular calcification, as well as calcification of the ascending aorta, the aortic arch and the ostia of his coronary arteries. The patient was confirmed to be homozygous for the D409H mutation in the glucocerebrosidase gene. The patient's enzyme assay for glucocerebrosidase activity was 5 nm/h/mg protein (normal 13-22 nm/h/mg). The patient presented with symptoms of dyspnea and chest pain. He had a 6-year history of documented aortic valve calcification by echocardiogram after two of his older brothers died of congestive heart failure and severe valvular calcification. Cardiac catheterization showed a severely calcified aorta with almost no motion of the aortic valve leaflets and severe calcification of the mitral valve and the mitral valvular apparatus. The patient underwent extensive cardiac surgery with aortic and mitral valve replacements and intraoperative findings confirmed calcification of the entire aortic root. Electron microscopy of the valves confirmed the presence of Gaucher's cells. Enzyme therapy with imiglucerase was initiated. The patient is in stable condition, 20 months post-operatively.     

冠状动脉的起源与意义

目的 观察中国人冠状动脉开口的变异情况,为临床冠状血管造影和介入术提供解剖学参考。 方法 选择 55例保存完好的心脏标本,探查每例标本的主动脉窦,观察各个窦中冠状动脉开口的数目和位置,测量从窦底分别到瓣尖、冠状动脉开口以及窦管交界的高度,并对所得结果进行记录和分析。 结果 主动脉窦中冠状动脉开口总数为2～5个不等,多数情况下右冠状动脉开口于主动脉右窦,回旋支和左冠状动脉合并开口于主动脉左窦,肺动脉窦或主动脉后窦中未发现开口。大多数开口位于窦管交界以下（94.5%）和瓣尖上缘以上（80%）,5例标本存在高位开口,即开口位置高于窦管交界。 结论 多数冠状动脉开口的位置在主动脉右窦和主动脉左窦内,瓣尖之上,窦管交界之下。一些变异比如多开口、纵向或环向的位置偏移及裂隙状开口会对解释图像带来困难,对临床进行血管造影、血管成形术、冠状动脉旁路移植术等操作造成不利影响。     

Changes in turbulence with rotation of the omnicarbon prosthesis

This study was performed to determine whether annular plane orientation of the Omnicarbon aortic valve influences forward flow turbulence. The Omnicarbon prostheses was modified to allow in situ manual rotation of the valve when implanted in the aortic position of eight 90 kg pigs. Pulsed Doppler ultrasound was used to acquire velocity measurements at 17 locations within the cross-sectional area of the ascending aorta. In each animal, 12 valve rotations were tested in this manner. Reynolds normal stresses were estimated from the velocity measurements. High Reynolds normal stresses were concentrated between left and posterior-right sides of the aortic wall for all orientations studied. No trends in mean or maximum Reynolds normal stresses with respect to valve rotation were consistent in the experiments. Unlike previous experiments with the Medtronic-Hall tilting disc valve, these experiments showed no notable changes in Reynolds normal stress with respect to orientation of the Omnicarbon valve. This suggests that the tendency of turbulent stresses to change with tilting disc valve orientation may be dependent on valve design.     

Gepulste Doppler-Echokardiographie bei Aortenvitien

Summary The diagnostic value of pulsed Doppler echocardiography (PDE) had not been sufficiently assessed up until now. Invasive catheter velocitometric measurements in the central vessels give quantitative information on the blood movement across the aortic and pulmonary valves. It is particularly useful in the quantification of aortic regurgitation. We successfully investigated 52 patients by means of PDE (ATL 500 A); 20 were suffering pure aortic incompetence, 11 pure stenosis and 21 had combined stenosis and regurgitation. Fifteen patients without aortic valvular disease served as controls. Our findings were compared with the results of cardiac catheterization and angiography in each case. In addition, 14 patients with aortic regurgitation were studied invasively by catheter velocitometry. The obtained regurgitation values were compared to the PDE method. In the PDE the underlying criteria for the assessment of the recordings were as follows: formal analysis of the analog signal and of the turbulence content during systole and diastole; in the flow velocity tracings aortic incompetence showed a steep increase with high peak to peak aortic velocities and scant turbulence formation; the reverse flow during regurgitation was accompanied by a high grade turbulent velocity pattern. The area under the diastolic (regurgitant) flow velocity curve (the time-amplitude integral) corresponded significantly with the angiographic severity of aortic insufficiency (r=0.87). In aortic stenosis, turbulence formation leads to an approximately flat velocity profile across the ascending aorta, if the region in the vicinity of the valve is omitted. The flow velocity analog signals are considerably disturbed. However, the turbulence content which can be qualitatively estimated from the recordings, correlates well with the calculated valve area. In combined aortic valve stenosis and incompetence, the prevailing turbulent pattern does not always permit one to assess sufficiently the severity of the stenotic component, whereas the grade of incompetence can be, in general, evaluated. PDE complements the existing non-invasive techniques and probably essentially enriches non-invasive diagnostics.

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Abkürzungsverzeichnis A Vorwärtsfluß - AI Aorteninsuffizienz - Ao Aorta ascendens - AS Aortenstenose - B Rückwärtsfluß - CTV Katheter-Tip-Velocitometrie - Flow Flußgeschwindigkeit - H positive Amplitude der Strömungskurve - LA linker Vorhof - LV linker Ventrikel - MAT Maximale Amplitude der Turbulenz - O Strömungsnull - PDE Gepulste Doppler-Echokardiographie - RPA Rechte Pulmonalarterie - RV Rechter Ventrikel - SV sample volume - T _syst systolisches Zeitintervall - U _max Strömungsgeschwindigkeit - _max Blutbeschleunigung     

升主动脉后二尖瓣显露途径的临床应用

目的 从临床上证明升主动脉后二尖瓣显露途径的可行性,为二尖瓣与主动脉瓣联合手术寻找合理的手术途径。方法 对9例二尖瓣与主动脉瓣联合手术的病人使用升主动脉后二尖瓣显露途径。于主动脉瓣环上方1．5cm处横断升主动脉以显露主动脉瓣,于升主动脉后方切开左心房顶部以显露二尖瓣。结果 9例病人主动脉瓣及二尖瓣均有良好的显露效果,手术顺利,无并发症发生。结论 升主动脉后二尖瓣显露途径对于二尖瓣与主动脉瓣均需手术的病人是一种理想的手术途径。     

Non-invasive monitoring of central blood pressure by electrical impedance tomography: first experimental evidence

There is a strong clinical demand for devices allowing continuous non-invasive monitoring of central blood pressure (BP). In the state of the art a new family of techniques providing BP surrogates based on the measurement of the so-called pulse wave velocity (PWV) has been proposed, eliminating the need for inflation cuffs. PWV is defined as the velocity at which pressure pulses propagate along the arterial wall. However, no technique to assess PWV within central arteries in a fully unsupervised manner has been proposed so far. In this pilot study, we provide first experimental evidence that electrical impedance tomography (EIT) is capable of measuring pressure pulses directly within the descending aorta. To obtain a wide range of BP values, we administrated noradrenalin and nitroglycerine to an anesthetized pig under mechanical ventilation. An arterial line was inserted into the ascending aorta for measuring reference BP. EIT images were generated from 32 impedance electrodes placed around the chest at the level of the axilla. Regions of Interest (ROI) such as the descending aorta and the lungs were automatically identified by a novel time-based processing algorithm as the respective EIT pixels representing these structures. The correct positions of these ROIs were confirmed by bolus injections of highly conductive concentrated saline into the right heart and into the ascending aorta. Aortic pulse transit time (PTT) values were determined as the delay between the opening of the aortic valve (obtained from arterial line) and the arrival of pressure pulses at the aortic ROI within the EIT plane. For 11 experimental conditions, with mean BP ranging from 73 to 141 mmHg, strongly significant correlation (r = −0.97, P < 0.00001) between central BP and aortic PTT was observed, suggesting that EIT-derived aortic PTT is a potential non-invasive surrogate of central BP.     

Transcatheter aortic valve implantation: status and challenges

Calcific aortic valve disease of the elderly is the most prevalent hemodynamically-significant valvular disease, and the most common lesion requiring valve replacement in industrialized countries. Transcatheter aortic valve implantation is a less invasive alternative to classical aortic valve replacement that can provide a therapeutic option for high-risk or inoperable patients with aortic stenosis. These devices must be biocompatible, have excellent hemodynamic performance, be easy to insert, be securely anchored without sutures, and be durable, without increased risk of thrombosis or infection. To date, complications are related to the site of entry for insertion, the site of implantation (aorta, coronary ostia, base of left ventricle), and to the structure and design of the inserted device. However, as with any novel technology unanticipated complications will develop. Goals for future development will be to make the devices more effective, more durable, safer, and easier to implant, so as to further improve outcome for patients with severe aortic stenosis. The pathologist participating in research and development, and examination of excised devices will have a critical role in improving outcome for these patients.     

Left coronary artery occlusion caused by a large thrombus on the left coronary cusp in a patient with a continuous-flow ventricular assist device

Despite continual improvements in ventricular assist device (VAD) therapy, various clinical issues are emerging. Importantly, various types of thromboembolic complications have been reported to date. Recently, we encountered a rare continuous-flow VAD-related thromboembolic event that resulted in acute myocardial infarction. A 26-year-old female who just underwent HeartMate II^® VAD implantation suddenly developed widespread anterolateral myocardial infarction on postoperative day 16. Echocardiography and aortography revealed a large thrombus on the left coronary cusp of the aortic valve that almost completely occluded the left coronary ostium. After VAD implantation, her aortic valve did not open, even at relatively low pump speeds; this was thought to be one of the causes for thrombus formation. Continuous suction of blood from the left ventricle and non-pulsatile flow into the ascending aorta resulted in a continuously closed aortic valve and stagnation of blood in the coronary cusp. Furthermore, both small body size (body surface area <1.3 m²) and postoperative right ventricular failure may have exacerbated blood stagnation and thrombus formation in this patient. We should have adjusted the anticoagulation and antiplatelet therapy protocols based on the patient’s condition. She underwent off-pump coronary artery bypass surgery and remained in clinically stable condition afterwards.     

Abdominal aortic aneurysm and stent graft phantom manufactured by medical rapid prototyping

A novel human aorta phantom built by medical rapid prototyping for use in computed tomography (CT) scanning is described. The phantom contained a stent graft that was deployed internally to mimic a repaired aortic aneurysm. The phantom was produced to allow assessment of the CT appearance of a stent graft inside an aorta using the new virtual intravascular endoscopy image presentation technique. The stent graft utilized contained suprarenal components (metal fixation struts), and these were placed with these struts covering the renal artery ostia. The phantom was filled with iodinated contrast medium at a concentration that produced a density similar to that found in normal CT angiographic scanning. The model was scanned at a variety of slice thicknesses, pitch and image reconstruction intervals. Visualization of the stent suprarenal components in relation to the renal artery ostia is shown and the overestimation of stent wire strut diameter demonstrated.