Structural heart intervention is not a new field in the percutaneous cardiac intervention. Interventions like balloon mitral valvoplasty, balloon atrial valvoplasty, atrial septal or ventricular septal defect closure and similar procedures for valves and congenital defects are a routine affair at cardiac centres. But what this new buzz in cardiology is a totally new paradigm shift in looking at valvular disease surgical treatment. It all started with the perpetual realisation of the need for safer alternatives than surgical treatment in patients who are too sick to be operated but who are likely to be benefitted by corrective surgery. We are talking about this unmet need where treatment is needed but the procedure is prohibitively risky or having high risk. Research and innovations have now brought us to a stage where we are at the verge of offering a superior and safer option at least for Aortic valve stenosis (AS).
The aortic valve is the valve through which all of the blood goes from the heart to the systemic circulation. Any narrowing affects cardiac output and is compensated by increased hypertrophy and contractility. For a long time, the patient may be asymptomatic but with the development of symptoms, the prognosis changes adversely. Around 34% of the patients may die suddenly. Surgical Aortic valve replacement (SAVR) carries a surgical mortality risk of around 3-8%. It is prohibitively higher in high-risk patients. The degenerative AS patients are elderly, they often carry serious comorbidities like renal disease, pulmonary disease, liver disease, previous heart surgeries or they be severely frail. All these factors may make the surgical AVR high risk or prohibitive. It is not a surprise that about 30% of elderly AS patients never undergo SAVR because of these reasons, portending unfortunate outcomes. Transcatheter Aortic Valve Replacement (TAVR) has come as a boon for all such patients. TAVR is a procedure where Aortic valve is implanted via peripheral arterial access. Most commonly femoral artery (major artery present in the groin), but in unfavourable cases, may be done from Subclavian artery, Carotid artery or at times direct Aortic access or transapical access. Broadly there are two categories of valves, balloon-expandable and self-expandable valves, with almost similar outcomes. In this procedure a catheter is passed and through which the specially designed aortic valve is implanted at the aortic annulus under fluoroscopy over the native aortic valve. Later it is optimized to produce good seal so that there is no leakage and achieve maximum effective orifice area. Generally, it is done in conscious sedation and most of the patients can be discharged in 2-3 days. The initial development was aimed at patients not fit for SAVR, the trials showed favourable results. And TAVR has now established itself as the treatment of choice for such patients and the international guidelines endorse this with class I recommendation. The initial devices and technique had some limitations that resulted in some risks of bleeding and a significant risk of the need for permanent pacemakers. Still, they proved to be better in prohibitive risk, high risk and even intermediate-risk patients. Over the years the technique has improved, the device itself has improved tremendously reducing the complication rates to acceptable levels. Now it is being done at centres which even do not have a surgical backup. Most recently TAVR has been found to be either at par or superior to SAVR in even low-risk real-world patients. This paves the way for designating TAVR as the therapy of choice for AS patients. There are some issues like higher cost and concerns regarding the longevity of the valve. But these valves are haemodynamically better and we have 7-year results available which show good valve performance. And it is expected that these valves would have comparable longevity to SAVR valves.
Now with success in AS patients, similar technology is being evolved for the mitral valve, pulmonary valve and even the tricuspid valve. The initial results are encouraging. Mitral valve replacement and pulmonary valve replacements are already being done in selected patients.
Similarly, encouraging evidence is coming up for mitral valve repair procedure through Mitra clip system. It is a procedure to correct mitral valve leakage deploying about 15 mm clips over the leaflet giving a double-barrel appearance to the orifice. Mitral valve leakage can be due to primary valve abnormality or secondary to chamber dilatation in patients with heart dysfunction. Recently Mitra clip showed a decrease in mortality in heart dysfunction patients. This system is even being used in tricuspid valve repair with mixed results. It is hoped that further innovation and experience will refine the system. Overall these innovations require a learning curve and are costlier than the presently available surgery. It is expected that with wider application and availability the costs would come down. Without doubt, such newer therapies are much needed particularly with the ageing world we are bound to have much more patients with multiple comorbidities.
To conclude we are seeing a future where most of the heart valves could be repaired or replaced without open-heart surgery. What we will achieve is a safer procedure, lower morbidity, shorter hospital stay and lesser burden to health infrastructure. The game-changer is that high risk sicker patients could be operated fulfilling the unmet need for limited surgical options in such patients. The best part is that worldwide surgeons and interventionist both are aggressively pursuing this field, making it more of a team game.
