The science behind therapeutic ultrasound is proven
New method uses therapeutic ultrasound
The procedure is useful for those patients in whom hypertension is mainly maintained by hormonal means. The kidney catheter is able to obliterate the sympathetic nerve fibers on the kidney with electrical impulses. These are the cause of the release of blood pressure-increasing hormones. If these nerve fibers are switched off, the blood pressure can be lowered significantly. This has been known since the 1950s when a surgical procedure was used in severely hypertensive patients.
The publication of the results from the US SYMPLICITY-HTN-3 study in spring 2014 caused disillusionment. In this study, no difference in effectiveness with a comparison group could be demonstrated. In Germany, this led to treatment being stopped in many small centers. "The scientific discussion was so present that it was even conducted with the cost bearers, which now makes everything difficult," explains Professor Peter Trenkwalder from Starnberg. At his clinic, eight patients with resistant hypertension had been treated with renal denervation. "We had quite good successes, which was probably also due to the correct selection of patients," said Trenkwalder in retrospect. Five out of six patients had sufficient blood pressure lowering from the procedure after treatment at his clinic. And: He had made sure that no one with sleep apnea syndrome received the ablation with the patients. In these patients there is an additional factor that increases blood pressure.
Despite the setbacks, renal denervation is still an effective means of lowering blood pressure for him: if the sympathetic system is switched off, a therapeutic benefit on high blood pressure can be expected - however this happens. ”The German Society for Cardiology (DGK ) intervened in the spring with an assessment of the US study. She explains the outcome of the study with the patient selection. “The patient group treated in Simplicity HTN-3 differed in several respects from those patients who are eligible for renal denervation in Germany: 24% (denervation) and 29% (control group) were African-Americans. These patients showed no different decreases in blood pressure, with a particularly strong decrease in the placebo group. This could be because they were given slightly different medications (increased use of vasodilators). They could also have a slightly different pathophysiology of hypertension. ”A lack of experience on the part of the examiner is also cited. At the same time, however, the professional association states: “Simplicity HTN-3 clearly showed that the procedure was safe. The overall complication rate in the denervation group was 1.4%, it was mainly a matter of minor vascular complications. "
Critics felt confirmed
Proven high-pressure experts such as Munich Professor Heinrich Holzgreve were less considerate of the process. In the Deutsches Ärzteblatt he published something like a swan song for renal denervation. He also speculated that the big business was one of the main reasons for the initial success: “Every doctor who promised 15 to 20 potential patients and had access to a catheter slot could get the“ starter package ”with generator and 15 disposable catheters for 55,000 euros from Medtronic. In February 2012 there were 160 centers in Germany alone. The denervation catheters turned out to be a lucrative business, so that other manufacturers also pushed onto the market. The boom is also confirmed by the number of interventions worldwide, which is said to be 10,000. ”(Deutsches Ärzteblatt, Dtsch Arztebl 2014; 111 (18): A-794 / B-682 / C-648 (www.aerzteblatt.de/lit1814 )
In fact, there are currently 6 CE-certified catheter systems available for renal denervation (Medtronic® Symplicity / Spyral, St Jude® EnligHTN, Vessix® The V2, Terumo® Iberis, Cordis® Renlane and Recor® Paradies). However, the process has by no means come to an end. Progress continues and further studies with suitable patients have now shown that the method has been successful.
New studies are successful
Prof. Felix Mahfoud from Homburg / Saar has probably the longest experience in Germany with renal denervation. He sees high-frequency ablation and thus renal denervation generally on the upswing again. Three studies have now been published with positive results for the procedure, most recently the French DENERHTN study in the Lancet (online January 26, 2015) with 106 patients. SYMPLICITY-HTN3 is the only one so far that has not returned a result. "It comes from the US health system," he explains and repeats the criticism expressed in the literature of an inadequate procedure and inexperienced practitioners.
Ultrasound as therapy - a new non-invasive procedure
A new, completely non-invasive procedure, in which therapeutic ultrasound is to be used, is currently being tested. In October, the Federal Institute for Drugs and Medical Devices (BfArM) approved a phase II clinical trial. However, he sees a need for clarification regarding the now targeted denervation with focused ultrasound.
What is new is the non-invasiveness of this treatment, which can hypothetically also be carried out by medical professional groups such as nephrologists or internists. WAVE IV's study director is Professor Dr. Roland E. Schmieder from the University Hospital Erlangen. He works together with the university clinics in Hamburg-Eppendorf and Bonn, as well as the Clemenshospital in Münster, the CardioVascular Center and Sankt Katharinen-Hospital in Frankfurt am Main on scientific evidence of the safety and effectiveness of the procedure, which is new for cardiovascular medicine, which has so far only been used in orthopedics, for example for Achilles tendon ruptures. The design of the sham-controlled clinical trial WAVE IV was first presented at the TCT in Washington in 2014 and was presented by him at the high pressure league conference in December.
With the not yet approved “Surround Sound” ® therapy system from the US manufacturer Kona Medical, ultrasound energy is emitted in a targeted manner from the outside. Both diagnostic and therapeutic ultrasound are located in a single head. The nerve cords of the renal artery are focused, which are then ideally obliterated using heat. The increased hormone production caused by brain impulses, which contributes to the increase in blood pressure, is thereby reduced.
Pros and cons of the new procedure
Privatdozent Dr. Felix Mahfoud is not yet convinced of the external ultrasound. “The colleagues try to emit energy with focused ultrasound. WAVE I and II had been made with an intravascular receiver that was used for adjustment. The intravascular part is no longer necessary. The system is completely geared towards non-invasive treatment. ”From his point of view, it remains to be seen whether the German feasibility study WAVE IV proves that the procedure is safe and that it also reduces blood pressure, which can be read from 24-hour blood pressure values leaves.
What is particularly unclear to him is the type of clinical application and the question: How well is the ultrasound and the energy generated with it focused? The practical problem: “The kidney is a moving organ. It moves in the retroperitoneum with every breath. ”A coughing patient, for example, causes uncontrolled movements - how is this supposed to work with therapeutic ultrasound? Mahfoud asks himself. And further: How can collateral damage be prevented? Back pain reported from the pilot studies - presumably as a result of muscular damage - but disappeared again after a few days. There is also a common difficulty for both procedures: the nerve fibers in the renal artery cannot be seen as an image in either procedure, neither with X-rays nor with ultrasound. "The visible vessel is controlled and energy is then released where nerves are suspected to be in the vessel." Furthermore, a direct measurement of the result of the procedure - such as the nerve conduction velocity - is currently not possible.
Mahfoud sums up: The advantage of the now tested therapeutic ultrasound remains the completely non-invasive procedure, which may one day also be justified alongside the catheter procedure. Special indications exclusively for therapeutic ultrasound in renal denervation are conceivable. These include: high-pressure patients with impaired kidney function who are reluctant to give contrast media, or patients in whom the renal arteries cannot be cannulated. Or: patients with anatomical conditions who suggest ultrasound treatment. Finally, there are also patients who do not accept an invasive procedure.
The lack of experience of the practitioner - as in HTN-3 - is prevented in WAVE IV by the fact that an experienced interventionalist is present at every treatment. The few devices currently available are also loaded onto vans for study purposes and borrowed between the centers, according to a statement from the manufacturer. Treatment is therefore currently only possible under study conditions.
Press release Kona Medical (German) from 02/27/2015
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