Prosthetic heart valves - Echocardiography Test

 

Echocardiographic assessment of prosthetic heart valves is a crucial aspect of cardiology, allowing clinicians to evaluate the function and integrity of artificial valves implanted in patients with heart valve diseases. Echocardiography offers a non-invasive and real-time imaging modality that provides valuable information about prosthetic valve function, structure, and potential complications. Here's a detailed note on the echocardiographic assessment of prosthetic heart valves:

1. Types of Prosthetic Heart Valves:

• There are two main types of prosthetic heart valves: mechanical and bioprosthetic (tissue) valves.
• Mechanical valves are typically made of durable materials like titanium or carbon and are characterized by excellent durability but require lifelong anticoagulation therapy due to the risk of thrombosis.
• Bioprosthetic valves are constructed from animal tissue (porcine or bovine) or human cadaveric tissue. They do not necessitate long-term anticoagulation but may have limited durability compared to mechanical valves.

2. Echocardiographic Techniques:

• Transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) are the two main modalities used for assessing prosthetic heart valves.
• TTE is non-invasive and more readily available but may have limitations in visualizing certain valve types or structures due to acoustic shadowing from the chest wall or lung tissue.
• TEE offers higher resolution imaging and is particularly useful for evaluating prosthetic valves implanted in challenging locations or assessing complications such as prosthetic valve endocarditis.

3. Parameters Assessed:

• Valve Function: Echocardiography assesses valve function by evaluating parameters such as transvalvular gradients, effective orifice area (EOA), and regurgitant volume.
• Transvalvular Gradients: Doppler echocardiography measures peak and mean pressure gradients across the prosthetic valve, providing information about valve obstruction or stenosis.
• Effective Orifice Area (EOA): EOA represents the cross-sectional area available for blood flow through the valve and is essential for assessing valve hemodynamics.
• Regurgitant Volume: Echocardiography detects and quantifies regurgitant flow across prosthetic valves, indicating valve insufficiency or incompetence.

4. Valve Morphology and Structure:

• Echocardiography allows visualization of prosthetic valve morphology, including leaflet motion, valve opening and closing dynamics, and the presence of any structural abnormalities such as leaflet thickening, calcification, or pannus formation.
• Assessment of valve prosthetic rings or struts is crucial for detecting potential issues such as dehiscence or paravalvular leaks.

5. Complications and Surveillance:

• Echocardiography plays a vital role in the surveillance of prosthetic valves for complications such as thrombosis, infective endocarditis, paravalvular leaks, and structural degeneration.
• Thrombus formation on mechanical valves or bioprosthetic valves, particularly in the setting of inadequate anticoagulation, can be detected using echocardiography.
• Prosthetic valve endocarditis often presents with periannular abscess formation or vegetations, which can be visualized and monitored using echocardiography.

6. Clinical Significance:

• Echocardiographic assessment of prosthetic heart valves guides clinical decision-making regarding anticoagulation therapy, the timing of valve replacement or intervention, and the management of complications.
• Regular surveillance with echocardiography is recommended for patients with prosthetic heart valves to monitor valve function and detect complications early, optimizing patient outcomes.

In conclusion, echocardiographic assessment of prosthetic heart valves is a fundamental component of the management of patients with heart valve diseases. It provides comprehensive information about valve function, structure, and potential complications, enabling clinicians to deliver individualized care and optimize patient outcomes.

During the last year in the United States there were approximately 10,000 earthen heart operations performed in which one or more heart valves were removed and replaced with an artificial device and yet the era of prosthetic heart valves began less than 20 years ago in 1954 when dr. Charles huffnagle of Georgetown University introduced a mechanical device which partially relieved aortic regurgitation this prosthesis consisted of a plastic ball enclosed within a lucite cage which was designed to be rapidly placed in the descending thoracic aorta external fixation rings held this prosthesis in place although the plastic valve was extremely noisy thrombogenic and relief regurgitation from only the lower half of the body it was a benefit to many patients and represented the first attempt at referring cardiac valvular dysfunction with a mechanical device in the late 1950s several surgeons including huffnagle henry bahnson's and dwight magoons began replacing single damaged cusps of the aortic valve in 1958 in a two-stage procedure dr. William H Muller of the University of Virginia first totally removed in aortic valve and separately replace each custom early in 1959 dr. Muller performed the first successful operation in which the damaged heart valve was completely removed and replaced with an artificial device this tricuspid Teflon prosthetic heart valve was used for the next several years by many cardiac surgeons a later modification by doctors Muller and James Littlefield added more circumferential support to this teflon prosthesis hemodynamically this was a very acceptable alternate to the natural aortic valve it was not obstructive was totally free of embolic difficulties and was completely silent unfortunately after 12 to 24 months these teflon leaflets stiffened and cracked resulting in recurrent a aortic stenosis and regurgitation and most of these leak valves were eventually replaced with later models of artificial heart valves the first complete replacement of the mitral valve was performed at the National Heart Institute in 1960 by doctors Andrew G Morel and Nina Brown walls they employed an artificial heart valve constructed of polyurethane foam reinforced with Teflon fabric the leaflets were controlled by artificial chordae tendineae which were brought through the left ventricular free wall and then adjusted to proper length and tension laters dr. moody CCC and dr. morrow developed a by custom prosthesis made of Teflon fabric that was successfully implanted in South Africa these fabric micro valves suffered the same fate as those used in the aortic position it was becoming obvious that any artificial heart valve using flexible components was entirely dependent upon the flex life of the material used and so attention was redirected to the use of widget materials early in 1916 both dr. Dwight - of the Peter bent Brigham Hospital in Boston and dr. Albert Starr of the University of Oregon we're developing artificial heart valves utilizing the caged ball principle dr. star successfully implanted such a prosthesis in September of 1960 since that time rigid materials have been used in the manufacture of prosthetic heart valves the only exception to this was a Teflon coated by silicon tricuspid prosthetic valve which was developed by dr. huffnagel in the late 1960s this valve underwent extensive and fairly rapid leaflet damage with large depositions of thrombus above the leaflets and it's useless quickly discontinued in 1962 dr. Hart and outlined the basic design criteria for the optimal prosthetic heart valve it should have lasting physical and geometric features and it should be capable of permanent fixation in the normal anatomic site it should be chemically inert non thrombogenic harmless to blood elements and it must not annoy the patient patient annoyance can refer to many things it's some noise generated when two rigid materials strike each other and such factors as the nuisance of lifelong anticoagulation it must open and close promptly during the appropriate phase of the cardiac cycle and it should offer no resistance to physiologic flows since 1962 at the clinic of surgery of the National Heart and Lung Institute the vast majority of prosthetic heart valves placed in the aortic or Michael position have been of the star edwards caged ball variety before discussing the evolution of the design of the star Edwards valve a discussion of its anatomy is necessary at first glance the mechanics of this valve seems simple enough but it must be remembered that there are three distinct offices which must be considered when implanting this type of prosthesis the primary office represents the area of the inflow orifice at the seat of the valve the secondary orifice is encountered when the ball is fully open and represents the area Eitan traited comb between the ball and the valve seat the tertiary office represents the area between the diameter of the ball and the surrounding tissue be it a Horta or ventricular cavity the next two photographs show examples of aortic valves in which tertiary orifice obstruction was present both are viewed from above through sectioned aorta the area between the ball in the open position and the adjoining aortic wall is too small and a significant obstruction to forward flow as a third the first star Edward selves series 1000 for the aortic position and 6000 for the mitral position were implanted in 1961 the aortic model is recognizable by the silastic fall and the three metal studs that project from the valve seat this early aortic valve had a fumble embolism rate of about 20% the Michael prosthesis the 6000 series is recognizable by a heavy metal base and thick crust this valve had an incidence of thromboembolic complications which exceeded 50% the greatest complication of these early star Edwards valves was in the silastic fall this silastic underwent lipid infiltration which led to changes in the shape of the ball both the shrinkage with fall escapes and swelling with cracking of the ball which led to improper movement of the ball in the cage and a predisposition to thromboembolism or Meishan in 1966 the 1000 and 6000 series were discontinued the new aortic models 1200 and then 1260 featured new techniques of tearing the silastic wall and extended the cloth to cover the inflow orifice the 1260 aortic model and the 6120 micro prosthesis which has a greatly reduced metal base continue in fairly widespread use these models have a greatly lowered incidence of thromboembolism and are very quiet at the National Heart and Lung Institute we are personally reluctant to use any silastic fall and we are apprehensive that the newer cheering techniques will not eliminate that only delay lipid and fatty acid infiltration and eventual deterioration of the silastic in 1967 there was a major modification of the star Edwards prosthesis in an effort to reduce the incidence of formal embolism a completely cloth covered cage was introduced which utilized a hollow metal ball of Stella 21 which has the same specific gravity as floods the cloth-covered models series 2300 or aortic implantation and 6300 for the mitral position had several difficulties tissue ingrowth occurred about the primary orifice thus decreasing the area and establishing unacceptable gradients across the valve in actuality this tissue ingrowth at the valve seat can pile up and cause both primary and secondary orifice obstruction tears and fragmentation of the single layer of cloth cover also occurred with some frequency the 2300 and 6300 series were modified to the 2310 and 6310 series respectively this series incorporated a composite seat of metal studs projecting through the cloth upon which the ball sees these seams who have eliminated the problem of tissue ingrowth at the primary orifice this series also introduced a two-ply cloth cover which has decreased software in certain of the 2310 series a disastrous complication occurred a close lawrence model was introduced in 1970 in which the transverse distance between the prophet and the case was reduced these valves impacted in the open with the acute onset of massive aortic regurgitation and sudden death this complication was also seen in the 63 Ken series of mitral valves this flaw was quickly eliminated and the present 23 2008 and 63 20 Michael plus disease have evolved these models are currently in use in our clinic they feature a metal pocket the comprise of deceit a wide distance between cage and pop up which flares even more near the apex and a to fly cloth covered concern about the to fly cloth undergoing wear and fragmentation has led Edwards laboratory to introduce a new series twenty four hundred and sixty four hundred which features a thin inner metal track which is the only part of the covered cage which contacts the ball thus preventing damage to the cloth cover this model is in a developmental stage and its major drawback is an excessive amount of noise many other caged ball type artificial heart valves have been and are currently in use in the United States one of the most unique of these is the McGovern sue chalice prosthesis in this valve sharp metal spikes contained in the seat are circumferentially impacted into the aortic annulus to keep the valve in position this has the advantage of a shorter operating time but the disadvantage of a high incidence of Terra basilar leaks in the hands of the surgeon who is not thoroughly experienced improper implantation techniques it also uses a sigh last II fall one instance for which the McGovern prosthesis is particularly suited is when the aortic annulus is extremely friable secondary to either infection for extensive calcific or Mixel modesty generation in this situation the McGovern prosthesis can be wedged into position and secured with good chances of remaining in place the smell off cutter caged ball prosthesis is a double cage of titanium with a silastic fall this design allows a smaller ball to be used then as possible in the star Edwards models since the ball does not seat on the ring that passes through it to seat on the cage underneath the DeBakey caged ball prosthesis made by surgeon tool features a pyro light carbon ball - prosthesis has a cloth covered cage on metal balls and a plastic cover about the see another caged ball prosthesis which is in widespread use is the brown walled cutter valve the concept of a cloth cover for a caged ball prosthesis was developed by doctors Brown walled and Mauro in this clinic the rationale was to eliminate thromboembolic complications and was suggested to them by observation of a bend in growth of tissue which occurred in the early Muller valves dr. Brown walls investigative work which demonstrated the efficacy of the cloth cover in reducing thromboembolism led both cutter and Edwards laboratories to use cloth covering in their caged ball prosthesis the brown walls cutter valve features a complete thin fabric cover which permits an in growth of a very thin layer of autologous tissue which does not compromise the diameter of the inflow orifice a silicon ball is used when the ventricular cavity is large the caged ball prosthesis is a satisfactory valve however when the left ventricular cavity is small as it usually is in pure michael stenosis the caged ball is often not acceptable not only can the ball obstruct flow out of the left ventricle as pointed out in the middle diagram but if the ball is in contact with ventricular muscle inflow to the left ventricular cavity can be obstructed it is also possible for a micro prosthesis if it is large and placed too high to impede closing of an aortic prosthesis in a double valve replacement however the most common problem with a caged ball Michael well is simply that the ventricular cavity is too small to contain it and a form of tertiary orifice obstruction occurs in an effort to solve this problem of size the disc tight valvular prosthesis was developed this valve uses a lens shaped puppet which occupies a much smaller portion of the ventricular cavity early prototypes of these valves were developed by dr. Jerome T of the University of Southern California in Los Angeles doctors Crofts and Jones and doctors are okay and Suzuki Hall of Cleveland dr. Dwight Horton was also a pioneer in the development of disc valves as was dr. Marceau serval of first there is only a small pressure gradient between the atrium and ventricle during diastole and thrombosis has been a great difficulty in these disc valves efforts to decrease the amount of experience metal as seen in the recent case I leave valve and the recent Parkin valve have decreased but not eliminated the problem of Fromm BOCES another difficulty with disc valves is muscle in growth from the left ventricle wall which prevents normal function of the disc Euskadi have also obstructed the low-profile valve in an effort to prevent muscle from the left ventricular free wall from obstructing the disc a recent modification of the case I leave valve has a muscle guard which protects the disc from this type of obstruction Edwards laboratory has also made a disk valve the early model series 6500 used the semi metal disk which had a very high incidence of thromboembolism and this has been modified to the 6520 series thromboembolism with this prosthesis has been reduced but not eliminated the Cooley blood well-thought thesis has also been discontinued because of an unacceptable incidence of crumble embolism a very popular mitral valve prosthesis which is currently in widespread use is the bell valve manufactured by Sergio tool this prosthesis features a Dacron velour covering initial experience shows a very low incidence of thromboembolism with this prosthesis recently the cutter disc prosthesis has been introduced in this valve the disc is smaller than the internal orifice of the prosthesis and sits on the upstream retaining struts this principle allows small amounts of controlled regurgitation which washes the disc and minimizes the chances of discontentment the retaining struts have no cross members which eliminates a focus for thrombosis this illustration demonstrates the potential for improved all in the Cooley cutter prosthesis one can see the symmetrical but restricted flow that occurs when the disc is larger than the primary orifice on the bottom is seen the increase in central flow that is afforded by use of the smaller disc regardless of the low-profile principle of disc valves tertiary orifice obstruction due to small size of the ventricular cavity can still occur one other type of artificial heart valve employs a disk on a pivot which gives unobstructed central flow an early model of dis principle was used by Vander's faith in this cloth covered toilet seat valve the spring pivot point above the valve represented an area of stagnant flow and offered great potential for thrombus formation the tilting disc valves which are popular today all have projecting pivot points with eccentric openings and areas of turbulence and stasis the water valve has recently been taken off the market because of a high incidence of thromboembolism the disc in this valve is fixed and thrombosis occurred at these fixed points we are impressed with the Buell Charlie prosthesis which employs the same basic principle but in which the selling dish is not fixed hence it can rotate and is in that respect self-cleaning tube your Charlie prosthesis is our choice in aortic valve replacement in children or when the annulus or aortic root are small it is also quite acceptable for use within an arterial graft besides artificial materials there has been a large amount of time directed at the use of biological tissues in the manufacture of prosthetic heart valves biological valves have been made of fresh alotta and pericardium and heart valves from human cadavers and animals have been employed in most cases late fibrosis and calcification with recurrent stenosis and regurgitation have been the rule an exception to this has been the Reece Hancock foreseen xenograft this valve which was designed by dr. Robert Rees here at the National Heart and Lung Institute for the micro or tricuspid position uses a pig a Orteig valve which is fixed and sterilized with glutaraldehyde and mounted on a flexible stent the valve has a low gradient cannot be obstructed by the left ventricle in diastole and requires no anticoagulation our experience with this prosthesis is into the fourth year and to date there have been no instances of thromboembolism or other sign of valve failure here at the valve which was removed at eight months because of a flow of a slow leak which demonstrates no sign of deterioration of the tissue leaflets these then represent most of the attempts at artificial construction of heart valves it is obvious that none of them can compare with our natural valves nor have dr. Harkins criteria laid down in 1962 been met progress in technical developments and modifications of these valves will continue and at the next 15 years are as fruitful as the last then we shall see many more exciting developments in artificial heart valves after this motion picture was completed a historical inaccuracy and a significant omission were discovered by the authors in September of 1958 three months prior to the first day or week valve replacement by dr. Muller dr. C Walton Lily hi of the University of Minnesota successfully replace a cardiac valve in the normal anatomic position following an unsuccessful Commissioner otta me and debridement an aortic valve was excised and a silastic flap plates in the subfloor nary position as depicted above the patient survived for at least 23 months one other such procedure was successfully performed by dr. lily hi the following year we also failed to mention the silastic butterfly leaflet prosthetic heart valve designed by doctors Vincent Cox and Ronald Daggett of the University of Wisconsin these valves were implanted clinically from 1963 to 1965 in both the aortic and micro position a number of these valves that were inserted eight to ten years ago are still folks well there are useless discontinued because of an unacceptable incidence of harm vocês that occurred on the downstream side of the leaflet at the area of the hinge site.