Percutaneous treatment for mitral regurgitation: the QuantumCor system.
OBJECTIVE
Percutaneous edge-to-edge techniques and annuloplasty have been used to treat mitral regurgitation (MR). However, neither intervention can be performed reliably a second time and, with annuloplasty, a foreign body is left behind. The mitral and tricuspid annuli are areas of dense collagen (Fig. 1); treatment with radiofrequency (RF) energy in sheep reduces their size, and can be repeated without affecting the coronary sinus. RF energy may also be used in leaflet procedures. Our aim was to improve mitral valve competence using techniques that can be incorporated into a minimally invasive approach.


METHODS
In open-heart procedures in 16 healthy sheep (6 with naturally occurring MR), we used a malleable probe (QuantumCor, Inc., Lake Forest, CA) that conforms to the annular shape to deliver RF energy via a standard generator to replicate a surgical mitral annular ring. Four segments of the posterior mitral valve annulus were treated while on cardiopulmonary support via a left thoracotomy with access via the atrial appendage. Seven sheep were followed chronically.


RESULTS
All sheep underwent intracardiac echocardiography (ICE) or direct circumferential measurement of the mitral annulus before and after RF therapy. RF therapy was administered in less than 4 minutes in each case, and the mean anteroposterior (AP) annular distance was reduced by a mean of 5.75 +/- 0.86 mm (23.8% reduction, P< 0.001). In the 6 sheep with nonischemic MR, regurgitation was eliminated. Acute histopathology (HP) demonstrated no damage to the leaflets, coronary sinuses, or coronary arteries. At 30 days, the AP distance continued to be reduced in the 7 surviving sheep (mean 5.0 +/- .6 mm, 21.4% reduction, P< 0.001).


CONCLUSIONS
In a sheep model, RF energy applied for less than 4 minutes per case at subablative temperatures in four quadrants of the posterior mitral valve annulus reduced the AP and circumferential annular distances significantly, and eliminated nonischemic MR. Results will need to be confirmed in follow-up studies to determine safety and efficacy. RF energy administered as a novel, percutaneous method of mitral valve annuloplasty may have the potential to reduce morbidity and mortality associated with current surgical techniques.
Heuser
Richard R
RR
St. Luke's Medical Center, University of Arizona, College of Medicine, Phoenix, Arizona 85006, USA. rheuser@affcard.com
Witzel
Thomas
T
Dickens
Duane
D
Takeda
Patricia A
PA
D015906:Angioplasty, Balloon, Coronary / Q000295:instrumentation* / Q000379:methods; D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods; D003094:Collagen; D019060:Minimally Invasive Surgical Procedures / Q000295:instrumentation; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging / Q000628:therapy*; D023421:Models, Animal; D012756:Sheep; D013997:Time Factors; D014463:Ultrasonography
D003094:Collagen