A French registry study shows that few complications occur in younger and less sick patients implanted with the Edwards Sapien valve (abstract no 85810), while a German study showed no deterioration in echocardiographic functional measurements taken three years after implantation with the Medtronic CoreValve (abstract no 82314).
TAVI - first introduced by Alain Cribier in 2002 - is currently performed in patients with severe aortic stenosis considered at high risk for surgical valve replacement. Aortic stenosis is a disease in which a long latency is followed by rapid progression after the appearance of symptoms; more than half the patients die within two years.
It is estimated that over the age of 65 years 26% of the population has mild, moderate or severe aortic stenosis, with 2% having symptomatic disease needing treatment.
"With the current ageing population it’s thought that over the next 15 years the number of patients with aortic stenosis will double,” said Mathieu Godin from the University Hospital of Rouen, France, and first author of the French study. “This makes it increasingly important to have non-surgical techniques more widely available".
The TAVI procedure, which has been performed in around 40,000 patients worldwide, involves percutaneously placing a metallic stent frame containing valvular tissue within the damaged aortic valve, with access for retrograde implantation gained from the femoral artery, subclavian artery and ascending aorta or antegradly from the apex of the left ventricle.
Today, two different CE-mark TAVI devices are available- the Edwards Sapien valve and the Medtronic CoreValve. The former is a balloon expandable system with a bovine pericardium valve in a cobalt-nickel stent, available in three sizes; while the CoreValve is a self expandable system with a porcine pericardium valve in a nitinol stent available in two sizes (with a third expected). Many next generation valves are currently under development.
Publication of the PARTNER trial last year represented the coming of age for TAVI (NEJM : 2010; 363:1597- 1607). In this study, from Columbia University Medical Center in New York, 358 patients with aortic stenosis who were not considered candidates for surgery were randomised to TAVI or the standard therapy of balloon aortic valvuloplasty.
Results at one year showed that the death rate from any cause was reduced by 45% among patients randomised to TAVI.
While TAVI is considered an alternative option to surgery in high-risk patients, long-term data on TAVI outcomes have been limited, making clinicians reluctant to carry out the procedure in patients in lower risk patients.
“One crucial test for TAVI will be the question of whether the durability of transcatheter valve prostheses is comparable to other biological prostheses,” said Anke Opitz, first author of the German study.
In the French study Godin and colleagues investigated the outcomes of patients with low EuroSCOREs (a system developed to predict the operative mortality of coronary surgery) who nevertheless had other contraindications to thoracic surgery - such as thorax deformity, porcelain aorta (with calcification), and mediastinal radiotherapy.
“These patients were often less sick and younger,” said Godin, “making it interesting to assess results of TAVI in this population.” So far, he added, most registries have only included patients at high risk of complications.
The investigators performed a retrospective study of 177 patients implanted with the Edwards prosthesis in Rouen between May 2006 and January 2011. The patients were divided into two groups according to their EuroSCOREs: high-risk patients were defined as having a predictive logistic EuroSCORE >20%, while low risk patients were defined as having a predictive logistic EuroSCORE <20%.
Results showed that procedural success was 100% in the low risk group, and 95.3% in the high risk group (p=0.1). Results also showed that at one month no deaths were observed in the low risk group and 11.1 % in the high risk group (P<0.04), and that at one year the mortality rate was 5% in the low risk group and 24.8% in the high risk group (P<0.01).
“While we were expecting a lower mortality among patients with low EuroSCOREs, the observed difference was much greater than anticipated,” said Godin. “In fact, the mortality rate was comparable to results with conventional surgery. The results represent a first step towards a broader assessment of percutaneous techniques in populations at lower surgical risk. However, we must state that to date, surgery remains the gold standard treatment for this population.”
In the German study Opitz and colleagues from the German Heart Centre in Munich performed an echocardiographic evaluation of 393 patients consecutively implanted with the Medtronic CoreValve between June 2007 and June 2011. Transthoracic echocardiography was performed preoperatively then at discharge and at 6, 12, 24 and 36 months, with readings taken to evaluate the transaortic valve mean and peak gradient (P mean, P max) and the effective orifice area (EOA).
Results showed that EOA increased significantly, but that pressure gradients decreased significantly (the higher the gradient, the higher the severity of the stenosis, p<0.0001 for all readings). In addition, there was no observable change in EOA or pressure gradients at 6, 12, 24 and 36 months.
“The results show that after three years follow-up patients treated with the CoreValve prosthesis demonstrated a sustained reduction in transaortic valve gradients and improvements in EOA,” said Opitz. “And the good news is that we didn’t have any unexpected early valve deterioration. He added that the next planned survey will be after five years.