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New approaches in devices for heart failure

Reshaping the heart with biomaterials and intricate anchor systems

Reshaping the heart using biomaterials and anchor systems and undertaking cardiac contractility modulation (CCM) are all new approaches in heart failure treatment, according to presentations at a Symposium on Monday.

Heart Failure

Gerd Hasenfuss described new developments in cardiac contractility modulation. Despite advances in therapy, morbidity and mortality from HF remain unacceptably high, with five-year mortality rates exceeding 50%. For this growing population of patients there clearly remains an unmet need for new therapeutic approaches.

Gerd Hasenfuss from the Heart Centre of Göttingen, Germany, described how CCM devices are being used to enhance natural contractions of the heart. While the Optimizer IV looks much like a pacemaker, its mode of action is very different. Unlike the pacemaker, CCM, which is implanted under the skin with wires threaded into the right part of the septum of the heart, delivers its electrical impulses precisely when the heart cells are fully depolarised during systoles and does not respond by initiating contractions. Studies, explained Hasenfuss, suggest CCM signals have a direct impact on cellular physiology, increasing phosphorylation of key proteins and modulating calcium handling by the sarcoplasmic reticulum.

A recent meta-analysis of three studies involving 641 participants showed CCM significantly improved peak V0² (a measure of performance capacity during exercise), 6-minute walk test distances and quality of life measured by the Minnesota Living with Heart Failure Questionnaire (p<0.0001).

The Revivent system uses titanium anchor heads to reduce the size of the left ventricle.The CCM system, said Hasenfuss, is the only device-based treatment option for 60% of HF patients with advanced symptoms and normal QRS durations, who are not suitable for cardiac resynchronisation therapy.

Currently ongoing is the Fix-HF- 5c study exploring CCM in 230 moderate to severe HF patients with LVEF of 25-45% and a QRS<130ms. ‘If this study proves positive, I believe it will be time for CCM to be indicated in guidelines for patients with a narrow QRS who still have symptoms under optimal drug therapy,’ said Hasenfuss. In theory, he said, the system could be used in addition to other implantable devices.

Stefan Anker, from the University of Göttingen, explained how a number of new approaches are being based upon a well-defined law of physics. The law of Laplace states that ventricular wall stress/tension is proportional to the radius and pressure within the left ventricular chamber and inversely proportional to the left ventricular wall thickness.

The Revivent system has been designed to reduce wall tension by restoring a more natural conical shape with a reduced radius. The approach involves a number of pairs of polyester fabric-covered anchor heads made of titanium and implanted on the left ventricular epicardium and right ventricular septum via a catheter-based approach.

The anchor pairs have a ‘flexible tether’ running between them that functions like a ‘zip tie’, squeezing the anchors together and holding them in place. The effect is to create a fold of tissue excluding the non-functioning scar created by a myocardial infarction. For the procedure, Anker said, the external anchors are positioned by transmural catheters, avoiding the need for cardiopulmonary bypass and making incisions in the heart. Data presented at the 2014 EuroPCR study by Olaf Wendler suggested that the efficiency of the remaining heart muscle was immediately improved by as much as 30-40%.

‘The technology also helps reshape the anatomy of the mitral valve, making more patients eligible for mitral clip procedures,’ said Anker.

Another approach using Laplace’s law is to inject the ventricular wall with inert alginate-hydrogel. This acts as a permanent prosthetic scaffold making it thicker. The procedure, Anker explained, involves performing a left thoracotomy to expose the heart and the pericardium, and then undertaking 10-19 injections of alginate-hydrogel into the beating left ventricular wall. ‘It’s a one-time procedure that does not require a power source and only minimal care following implantation,’ Anker said.

In the phase 2 AUGMENT-HF trial, 78 patients were randomised to alginate-hydrogel in combination with standard medical therapy through a limited left thoracotomy approach (n = 40) or standard medical therapy alone (n = 38). Results published online in the European Heart Journal in June showed at six months that alginate-hydrogel treatment was associated with improved peak V0², six-minute walk test distance, and NYHA functional class (P<0.001). Furthermore, the six month MACE rate excluding the index hospitalisation was lower for patients receiving alginate-hydrogel and appears to have been mostly attributable to lower rates of hospitalisations for worsening HF.

‘These results provide proof of concept that intracardiac injection of alginate-hydrogel leads to beneficial effects in patients with advanced chronic HF,’ said Anker, adding that the absence of any increase in ventricular arrhythmias was reassuring. Future developments, he said, might include the possibility that the invasive procedure could be supplanted by percutaneous approaches, allowing hydrogel delivery by catheters, and the possibility that the inert material could be used as a transport system for locally acting drugs.