I. History of valve surgery The treatment of heart valve disease is still the main problem facing the medical community. It involves the selection of the most appropriate drug therapy, the optimal timing of intervention, the selection of the correct procedure, and the selection of the appropriate valve for valve replacement. Surgical treatment of heart valves has been performed for a century, with Theodore Tuffler successfully performing finger dilation in a patient with aortic obstruction on July 13, 1912. The first in situ aortic balloon valve replacement was performed by Harken and colleagues, and the first prosthetic heart valve meeting was held in September 1960, which led to tremendous progress in this field. Today, valve replacement surgery is a fundamental procedure in cardiac surgery. At the same time, the development of interventional disciplines has continued to explore new minimally invasive approaches to valve disease treatment. (1) Balloon Dilation 1. Percutaneous Mitral Valve Dilation: pioneered by Inoue 20 years ago, the application of the Inoue balloon allows for rapid, safe, and effective expansion of the mitral valve and is considered the standard procedure for closed mitral valve dilation. In a long-term follow-up study, 88% of patients had an orifice area of 1.5 cm2 or more, and valve function was significantly improved without severe mitral regurgitation [1]. 2, Percutaneous aortic valvuloplasty (PAV): percutaneous aortic valvuloplasty was first performed by Alain Cribier 20 years ago, mainly in those patients with contraindications to surgical valve replacement. It has been largely abandoned because it does not alter the natural course of the patient, and is used in the ACC/AHA guidelines as a transitional treatment before surgery in patients who are hemodynamically unstable. (b) Interventional angioplasty 1. Margin-to-edge technique: The margin-to-edge technique was developed to mimic the Alfieri double-port procedure, which uses an interventional approach to control mitral regurgitation by clamping a clip in the middle of the anterior and posterior mitral leaflets. In a statistic of 27 patients, mitral regurgitation was reduced to grade II or less in 67% of patients at the end of this procedure, with a mean MR level of 2.1 at 6 months. There is also an edge-to-edge technique using sutures, which is currently working well in animal studies. 2, Transcatheter valve mitral annulus annuloplasty: A restrictive device is implanted in the coronary sinus using catheter technology to reduce the mitral annulus, thereby achieving control of mitral regurgitation; however, it has not been reported for clinical application. 2, Percutaneous valve replacement Davies, Anderson performed the first trial with a valve stent 20 years ago, Bonhoffer performed the first percutaneous pulmonary valve implantation, and Alain Cribier performed the first balloon-expandable aortic valve stent implantation. A certain number of clinical applications have been reported. (C) Transcatheter valve implantation 1. Overview of transcatheter valve implantation Transcatheter valve implantation is an emerging technique that allows a minimally invasive approach to the treatment of heart valve disease. In the current transcatheter valve stent implantation research, it is mainly limited to the outflow tract heart valve research, that is, the study of aortic and pulmonary valve valve stent, the pulmonary valve stent was first studied by Bonhoeffer in France, and there are hundreds of cases of clinical applications reported. We are in the early stages of research in China, and we are still in the animal stage. The outflow tract valves, such as the mitral valve with valve stent valve, are less developed. 2, aortic valve implantation route According to the current experience of different researchers, different implantation routes have been used, the most commonly used are three: ① retrograde implantation route through the femoral vein by the venous system through the septum, this route in vivo travels a long distance, need to wear the septal injury, the guidewire to pass through the mitral valve, the injury is complicated, there are reports of mitral injury, but this route is one of the earliest methods of successful human implantation ② through the apical proximal implantation route, the first method of human implantation. This route is short, easy to master, and has relatively low technical requirements, but it requires open-heart surgery and loses the advantages of interventional treatment. However, in patients with severe aortic calcification, it is more difficult for the bare stent to pass through the stenotic aortic valve, and a special design is needed to solve this problem. The first transcatheter valve implantation in humans was performed by Dr. Phillipp Bonhoeffer and published in the October 21, 2000 issue of Lancet. They sewed a bovine jugular vein valve onto a NuMed CP stent and introduced a balloon catheter into the pulmonary artery or right ventricular pulmonary artery duct to control pulmonary regurgitation. Eighty-eight cases of this procedure have been reported, with a 98% success rate. These patients were mainly after tetralogy of Fallot, pulmonary atresia combined with ventricular septal defect, d-TGA, permanent arterial trunk surgery and s/pROSS. ② Different aortic stents with valves Alain_Cribier was one of the first surgeons to perform transcatheter aortic valve interventions. He observed the poor long-term outcome of calcific aortic valve stenosis with the application of balloon dilation and began to experiment with a bioprosthesis embedded in a stent that would place this system over the calcific valve. Many cadaveric studies were performed for this purpose, and a stent length was determined that would effectively fix the valve without interfering with coronary blood flow. Based on a patent by Henning R. Anderson in February 2000, the percutaneous valve technique was developed as the first balloon-expandable stent that could be delivered transcatheter through the aortic valve. in April 2002, Alain Cribier performed the first transcatheter aortic valve stent implantation in a patient with severe aortic stenosis. The currently applied valve is a 14mm*23mm high quality stainless steel stent secured to a 23mm Z-MED II balloon valvuloplasty catheter. The stent valve can be delivered by a 24F sheath. In their early experience with 6 patients (J Am Coll Cardiol. 2004Feb ;43(4):698-703.), PHV release was successful in 5 patients. One patient died due to valve displacement in a patient whose own valve had torn. Acute hemodynamic and angiographic findings showed no transvalvular pressure difference, aortic regurgitation was mild (3 cases) or severe (2 cases), and coronary flow was patent in all cases. Echocardiography demonstrated an increase in aortic orifice area from 0.5±0.1 cm2 to 1.7±0.03 cm2, and aortic regurgitation was a perivalvular leak. Significant and durable hemodynamic and clinical signs improvement was observed after successful PHV release. The first three patients died of noncardiac disease at 18,4 and 2 weeks postoperatively, respectively. The other three patients are currently alive for 8 weeks without manifestations of heart failure. The possibility of percutaneous implantation of aortic stents with valves in patients with end-stage calcified aortic stenosis is considered to be an important option for those patients who are not candidates for surgical intervention. In their report of another 8 patients, they concluded that transcatheter aortic valve stenting was effective in reducing aortic transvalvular pressure difference and improving EF and systolic function in patients. Goerg Lutter [2] from Germany published in 2002 their animal experiments on a transcatheter implantable self-expanding aortic band valve stent designed by them. They made a collapsible aortic valve stent by suturing and fixing a porcine aortic valve under a self-expanding nickel-titanium alloy stent. The valve stent, with an outer diameter of 15-23 mm and a length of 21-28 mm, was tested by an extracorporeal circulation system before implantation. Only those with a transvalvular pressure difference of less than 7 mmHg and a regurgitation level of Ⅰ° or less were tested for in vivo implantation. They studied a total of 14 pigs. After anesthesia, the pigs were introduced extraperitoneally into the delivery system (22F) from the left iliac artery or subrenal aorta. 6 implantations were made in the descending aorta and 2 in the ascending aorta. Transvalvular pressure difference, valve opening and closing status, hemodynamic characteristics, regurgitation, and gross pathology were compared before and after implantation. One pig died of ventricular fibrillation and 2 pigs failed due to stent fracture. At the end point of observation, the transvalvular pressure difference was low in the 11 successfully implanted animals (mean end-diastolic Δρmax of 5.4±3.3 mm Hg in the descending aortic group and 5.4±1.2 mm Hg in the ascending aortic group) and did not differ from the in vitro transvalvular pressure difference. 5 animals with complete valve opening were detected by ultrasound. Imaging suggested only physiological regurgitation (0°) in 8 of 11 animals and mild regurgitation (I°) in 3. Color Doppler results of the five animals in which ultrasonography was performed showed no valve regurgitation and only one animal had a slight perivalvular leak. Grube E [3] reported the first case of implantation using a self-expanding stent in 2005 (Catheter Cardiovasc Interv. 2005). Their valved stent consisted of three bovine pericardial valve leaflets anchored to a self-expanding nitinol. The case was a 73-year-old woman with symptomatic severe aortic stenosis (mean transvalvular pressure difference of 45 mmHg and orifice area of 0.7 cm2). Due to previous bypass surgery and other comorbidities, surgical valve replacement was difficult to perform. The valve was implanted retrograde through the common iliac artery. Extracorporeal circulation was performed in the contralateral femoral vessel to reduce the left ventricular load during stent release. Clinical, hemodynamic, and echocardiographic monitoring were performed intraoperatively, and clinical and ultrasound observations were performed at 1, 2, and 14 days postoperatively to evaluate the recent results. The valve stent was successfully and accurately released in situ in the aortic valve without damage to the coronary artery or venous bridge. Two-dimensional ultrasound immediately after stenting demonstrated a significant decrease in mean transvalvular pressure difference (from 45 to 8 mmHg) and no signs of mitral valve insufficiency. The patient’s clinical symptoms were significantly improved. No worsening of clinical symptoms occurred at 14 days of follow-up. This is the first report of the clinical use of a self-expanding aortic stent with valve. Christoph H. Huber [4] evaluated their development of a self-expanding aortic band valve stent and its effect on coronary blood flow in animal studies. They fixed equine pericardium to a nickel-titanium alloy self-expanding stent (3F TherapeuticsTM, CA, USA) with an external diameter of 23 mm, and evaluated it in group A by power-simulated pulsatile cycling in vitro and in group B by implantation in six calves (75±2.5 kg). four animals underwent in vitro cycling without release and two animals underwent non-in vitro release after ventricular fibrillation induction. The target site was the aortic valve in situ. In vivo evaluation included intracardiac ultrasound and intravascular ultrasound of leaflet motion, orifice measurements and residual coronary sinus stent index (RCSSI, stent-to-aortic distance/coronary internal diameter), coronary flow characteristics, transvalvular pressure difference, and continuous cardiac row measurements. Gross observations were performed at autopsy. RESULTS: Two-dimensional intracardiac ultrasound demonstrated good valve leaflet motion and complete valve opening and closing in all 6 animals. The valve orifice area was 1.75±0.4 cm2.RCSSIo 1.8±1.2, and there was no sign of impaired coronary flow. Direct measurements of the implanted valves showed a low transvalvular difference of 5.3±3.9 mmHg (mean, peak-to-peak) and 2-dimensional intracardiac ultrasound measurements of 4.7±2.5 mmHg. One of the six valves had mild to moderate regurgitation and one had a mild to moderate perivalvular leak due to valve mismatch. Self-expanding stents were found to be implantable in situ under extracorporeal circulation or non-extracorporeal circulation without affecting coronary blood flow and with good valve function at the right size. Paniagua D [5] performed a clinical observation of aortic stent implantation with a valve in 2005. The patient was a 62-year-old male with a severely calcified aortic valve that could not be treated surgically due to multiple severe comorbidities. The Cook sheath was introduced into the abdominal aorta via the right femoral artery. A pigtail tube was guided through the aortic valve via a guide wire into the left ventricle for pressure step measurement and anatomical examination. An 18-mm dilating balloon was applied to pre-dilate the aortic valve. Transient cardiac arrest occurred during the attempted valve positioning. Stenting with a valve was performed by prepositioning the right coronary artery in the same radiographic plane. The valve was released by applying a balloon to dilate the stent. The patient was extubated on the second postoperative day and reintubated 12 hours later due to respiratory failure and pulmonary hypertension. His condition continued to deteriorate and he died on postoperative day 5 due to biventricular insufficiency and intractable hypotension. In addition to hypotension, ultrasound Doppler showed satisfactory valve function. Retrograde release of the valved aortic stent valve can produce good hemodynamic outcomes, making it an exploratory work for future application of such techniques in high-risk patients. Hanzel GS [6] also performed a clinical trial of retrograde implantation of aortic stents with valves. During stenting with a valve in an 84-year-old patient with intractable heart failure with acute aortic valve obstruction, the anterior mitral leaflet became entangled with the guidewire during attempted implantation of the valve stent through the septal route in a retrograde fashion, resulting in severe mitral regurgitation and electro-mechanical separation. After successful cardioversion, the stent was successfully implanted in the area between the coronary opening and the mitral valve by switching to the retrograde route. The aortic orifice was raised from 0.55 cm2 to 1.7 cm2 with only a mild perivalvular leak. Despite the significant improvement in aortic valve function, the patient died the next day from severe mitral regurgitation and cardiogenic shock caused by a tear in the anterior mitral leaflet. However, his experience also demonstrated that retrograde implantation of PHV can be performed successfully and can effectively increase the aortic orifice area with an acceptable degree of aortic regurgitation. Although the retrograde implantation route may have the potential for vascular complications at the implantation site, it is relatively safe by avoiding mitral valve damage from the guidewire. Further refinement of this technique may allow for preferential use of this approach for PHV implantation in patients with inoperable acute aortic stenosis. There are also other types of aortic stents with valves in the literature, such as the ball-cage valve designed by Pavcnik D [7] (Radiology. 1992). We designed and manufactured a ball-cage aortic valve that can be implanted by transcatheter technique and performed an early evaluation of this technique using 12 mongrel dogs. The implant consists of a ring, cage, and a ball. The ring is made of stainless steel curled into a spiral shape and covered with an expandable nylon mesh. The cage is supported by a self-expanding Gianturco holder with a stainless steel wire attached to the head end. The ball is a removable silicone ball filled with an x-ray-impermeable silicone polymer. The self-expanding ball cage valve can be implanted into the descending aorta via the internal carotid artery using an 11 or 12F sheath. The stability and effectiveness of this valve is evaluated with X-rays during the functional phase (1-3 hours). However, no progress in their study has been reported for more than a decade. There are also other studies of valves with new materials. Such as the joint application of tissue-engineered valves as valve inactive scaffolds capable of being resorbed or shaped, as proposed by Dr. John Mayer of Harvard University in Boston and Maygdi Yacoub of Imperial University in London. and a mechanical valve developed by Dr. Steven Balley of the University of San Antonio Texas, which can be so thin as to be negligible (above). 4. Current Issues and Evaluations The progress of interventional therapy in valve disease is reviewed in this article. Mitral valve balloon dilatation is relatively mature, while mitral repair surgery requires further clinical evaluation, and pulmonary artery with valve stents have more clinical experience due to the relative simplicity of the local anatomy. The current hot spots and difficulties of research are focused on the development of aortic with valve stents. The limitations of the stent system and valve material of aortic valve stents, the release route, the mastery of surgical technique, the problem of embolization due to pre-expansion during valve stent implantation, valve durability and stability, and the influence of local anatomy are the biggest problems in the development of aortic valve stents. However, the results of early valve interventions and replacements are encouraging. III. FUTURE OUTLOOK: From the initial idea of the main stent valve to the first clinical application, there has been tremendous technical development in just over a decade. Despite the difficulties in the development process, as one valve surgeon prophetically pointed out in his valve surgery study, “we must not be totally defeated by these setbacks, but rather encouraged by this limited success. We must not forget the earliest results of prosthetic valve implant research in the early days of cardiac surgery and keep these in mind as we evaluate the results of today’s new transcatheter technology. There is no doubt that this technology will overcome its current limitations and develop into a safe and effective technique.