Aortic valve decalcification

Ultrasound Therapy as a Treatment for Valvular Aortic Stenosis: A Review

Calcific aortic stenosis is the most common form of aortic stenosis, and offers a poor prognosis in affected patients. Current treatment methods for aortic stenosis, including open surgical aortic valve repair and transcatheter aortic valve replacement, are invasive, and require the patient to undergo open-heart surgery with cardiopulmonary bypass. Ultrasound therapy offers a potential solution for patients ineligible for traditional surgical treatment. Noninvasive ultrasound therapy allows for decalcification of aortic valves without open sternotomy or cardiopulmonary bypass. This article reviews the use of ultrasound therapy for aortic stenosis, including this newer method of noninvasive ultrasound therapy.

The Genetic Regulation of Aortic Valve Development and Calcific Disease

Heart valves are dynamic, highly organized structures required for unidirectional blood flow through the heart. Over an average lifetime, the valve leaflets or cusps open and close over a billion times, however in over 5 million Americans, leaflet function fails due to biomechanical insufficiency in response to wear-and-tear or pathological stimulus. Calcific aortic valve disease (CAVD) is the most common valve pathology and leads to stiffening of the cusp and narrowing of the aortic orifice leading to stenosis and insufficiency. At the cellular level, CAVD is characterized by valve endothelial cell dysfunction and osteoblast-like differentiation of valve interstitial cells. These processes are associated with dysregulation of several molecular pathways important for valve development including Notch, Sox9, Tgfβ, Bmp, Wnt, as well as additional epigenetic regulators. In this review, we discuss the multifactorial mechanisms that contribute to CAVD pathogenesis and the potential of targeting these for the development of novel, alternative therapeutics beyond surgical intervention.

Ultrasonic Devices in Cardiac Surgery

Recent innovations in ultrasonic devices include high-frequency coagulating shears with piezoelectric ceramic electrostrictive transducers for both open and endoscopic procedures. Various ultrasonic devices have been used for the dissection of internal mammary, radial, and gastroepiploic arteries, aortic root, proximal right coronary artery, and left main coronary artery, as well as prior to surgical coronary ostial reconstruction and for elimination of stenotic induration in coronary arteries, release of muscle bridges, exposure of deep-seated coronary arteries, pericardiectomy, and removal of a cardiac tumor. Unlike valve decalcification, the required energy output of ultrasonic aspirators in coronary artery surgery is much lower and harvesting time of arterial conduits is significantly shortened. Ultrastructural studies of harvested internal mammary artery segments with scanning and transmission electron microscopy revealed no structural alteration of the wall or luminal surface when low energy output was used for dissection. On direct application of higher energy, subendothelial blistering may be detected occasionally. Ultrasonic devices help to remove thick fatty tissue and muscle bridges with almost no bleeding. Use of these devices may facilitate precise coronary artery surgery.

Aortic valve decalcification for severe aortic valve stenosis in the elderly: medium-term results

AIMS

To present the results of a novel technique of aortic valve decalcification (AVD) in a consecutive population of elderly patients with severe aortic valve stenosis (AVS) and small aortic annulus.

METHODS

Between January 2008 and December 2012, a consecutive series of 34 patients (mean age 80 ± 13 years) with severe AVS were operated on using AVD. They were compared with a matched population of 68 patients (mean age 82 ± 7 years) submitted to aortic valve replacement (AVR) with bioprosthesis. The two groups were comparable for cardiac risk factors and admission symptoms. Preoperatively, all patients presented with severe AVS, small aortic annulus (19 mm) and preserved left ventricular function.

RESULTS

Thirty-day mortality was 8.8 vs. 7.5% in the AVD and AVR groups, respectively (P = 0.88). Actuarial 2 and 5-year survival rates were 80 vs. 82% and 64 vs. 78% in the AVD and AVR groups, respectively (P = 0.27). Long-term valve-related events incidence was significantly higher in the AVD group (12%) compared with that in the AVR group (4%; P = 0.01). However, in the AVD group, patients with no or mild residual AR experienced 2 and 5 years of freedom from valve-related events, which is not significantly different from the patients submitted to the AVR group (P = 0.76). After AVD, a significant increase in the aortic valve area (from 0.8 to 1.9 cm) and a parallel reduction in the mean gradient (from 40 to 12 mmHg) was observed in all patients (P = 0.01). Postoperative aortic valve area (1.9 vs. 1.26 cm), as well as mean gradient (12 vs. 21 mmHg), were significantly better in the AVD group compared with that in the AVR group (P = 0.01).

CONCLUSION

In this preliminary experience, AVD seems a good therapeutic option for elderly patients with severe AVS. Further studies with longer follow-up are needed in order to confirm these preliminary results and to ascertain the valve durability over time.

A new ultrasonic process for a renewal of aortic valve decalcification

Background

Aortic valve decalcification by ultrasound was given up. We evaluated a new ultrasound microhandpiece (Dissectron Penstyle^®) to rehabilitate this alternative treatment.

Methods

We used under magnifying lenses the ultrasound microhandpiece to decalcify 30 explanted aortic valves. In the cases with embedded calcifications the thin top of the probe could be introduced into the thickness of the leaflet preserving covering layers.

Results

The leaflets were totally decalcified and flexible, and surrounding structures were preserved as assessed by histological examination.

Conclusion

This new approach of ultrasonic aortic valve decalcification gives good in vitro results which allow to consider a clinical evaluation of this procedure.

The role of cavitation microjets in the therapeutic applications of ultrasound

The dynamics of a gas bubble situated in a sound-irradiated liquid and near a rigid boundary was studied theoretically to get a better understanding of the role of cavitation microjets in the therapeutic applications of ultrasound (US). The boundary integral method was adopted to simulate the temporal development of the bubble shape, jet formation during bubble collapse and bubble migration. It was found that the dynamic behaviour of the jet and the migratory characteristics of the bubble depend not only on the distance between bubble and boundary but, also, on the properties of the acoustic field. For frequencies of sound fields smaller than or equal to the resonance frequency of the bubble, jet formation and bubble migration toward the boundary are the main features of the interaction. No jet formation was observed for frequencies of sound fields larger than the resonance frequency of the bubble, and the bubble kept its initial position from the boundary throughout its motion. The pressure generated by the impact of the jet developed during bubble collapse close to the boundary may result in the fragmentation of brittle objects, such as renal calculi, dental tartar or intraocular lens.

Management of asymptomatic mild aortic stenosis during coronary artery operations

BACKGROUND

Management of asymptomatic mild aortic stenosis at the time of coronary artery bypass grafting (CABG) remains controversial. We have retrospectively analyzed a cohort of patients requiring aortic valve replacement (AVR) subsequent to CABG and compared their operative morbidity and mortality with that of a group receiving CABG and AVR simultaneously at the first operation.

METHODS

Analysis is drawn from 28 patients who required AVR 8 +/- 4 years subsequent to CABG (group A) and 175 patients receiving AVR along with CABG at the primary operation (group B). Groups were similar with respect to age, sex, risk factors for cardiac disease, extent of coronary artery disease, left ventricular function, New York Heart Association class, aortic valve area, number of grafts, and size of prosthesis inserted.

RESULTS

Patients having AVR subsequent to CABG had a significantly prolonged aortic cross-clamp time and global myocardial ischemic time and incurred a twofold increase in operative mortality. The actuarial survival at 10 years was not significantly different between cohorts. In the 28 patients in group A, the aortic valve area during the period between operations decreased 0.05 mm2/y.

CONCLUSIONS

The operative mortality and morbidity of a second operation for AVR is high, but there is no significant difference in survival at 10 years. In at least a portion of patients having mild aortic stenosis at the time of CABG there will be progression of the stenosis necessitating reoperation at a later date.

In vitro decalcification of aortic valve leaflets with the Er:YSGG laser, Ho:YAG laser, and the Cavitron ultrasound surgical aspirator

This study was designed to compare the efficacy of the erbium:yttrium-scandium-gallium-garnet (Er:YSGG) laser and the holmium:yttrium-aluminum-garnet (Ho:YAG) lasers in debriding calcium from freshly explanted aortic valve leaflets and to compare the Er:YSGG laser with the Cavitron ultrasonic surgical aspirator (CUSA). Aortic valve leaflets were freshly explanted from patients undergoing aortic valve replacement for aortic stenosis. Initially, 4 leaflets each were debrided with the Er:YSGG and the Ho:YAG lasers to attempt removal of calcium deposits while preserving the underlying integrity of the leaflets and minimizing thermal damage. The Er:YSGG laser was more effective in doing so with less thermal and photoacoustic damage when compared with the Ho:YAG laser. Twelve more leaflets each were then debrided with the Er:YSGG laser and the CUSA. The Er:YSGG laser again proved less injurious to the underlying leaflet. The CUSA-treated leaflets demonstrated shattering and disruption of adjacent tissue as well as collagen fiber exposure. These changes were not seen with the Er:YSGG laser. Because of these properties, the Er:YSGG laser merits further evaluation as a tool for aortic valvuloplasty procedures in selected patients with senescent calcific aortic stenosis.

Repair of asymptomatic aortic valve disease during other cardiac surgery

Repair of asymptomatic aortic valve disease was performed in 12 patients (9 female, 3 male, mean age 57.5 years) undergoing other cardiac surgery. Stenosis was the predominant aortic valve lesion in 7 (group A) with a mean gradient of 33.4 mmHg and regurgitation of mean grade 1.4 was predominant in 5 (group B). Cusp debridement +/- commissurotomy was performed in 9; commissural resuspension in 6 and repair of cusp perforation in 2. Perioperative transoesophageal echocardiography was used to assess the adequacy of repair in 4 patients. Prospective precordial echocardiographic follow-up is complete (mean 4.3 months). In group A there has been a significant reduction is peak aortic pressure gradient (33.4 vs 22.1 mmHg, p less than 0.05) and in cusp thickness (2.25 to 1.64 mm, p less than 0.05). In group B the degree of incompetence has improved in 3 of the 5 patients. Three patients have worsened valve disease following repair; in all these there was mixed valve disease of rheumatic origin. Aortic valve repair of asymptomatic disease during other cardiac surgery is a feasible technique which does not accelerate the disease process in the short term. Long-term follow-up is in progress to assess the prognosis of this preventive intervention.

Combined conventional mechanical and ultrasonic debridement for aortic valvular stenosis

Ultrasound decalcification of aortic valve stenosis was performed in 31 patients. There were 16 men and 15 women with a mean age of 71.03 +/- 9.6 years (range, 51 to 89 years). Each had severe calcific aortic stenosis with an aortic valve gradient greater than 40 mm Hg, aortic valve area (AVA) less than 0.6 cm2, and no serious insufficiency. Feasibility of aortic valve debridement was determined under direct vision. Intraoperative epicardial or transesophageal color Doppler two-dimensional echocardiography was used before and after the aortic valve debridement to evaluate aortic cusp motion and aortic regurgitation. Direct transseptal aortic valve gradient was measured on all patients before and after aortic valve debridement, and the AVA was determined. Aortic valve debridement was performed as the primary procedure in 17 cases and combined with other cardiac procedures in 14 patients. Preoperative aortic valve gradient was reduced from 72.5 +/- 22.5 mm Hg (range, 40 to 130 mm Hg) to 15.5 +/- 11.9 mm Hg (range, 2 to 50 mm Hg), and the average AVA of 0.41 +/- 0.10 cm2 (range, 0.22 to 0.63 cm2) was increased to 1.55 +/- 0.58 cm2 (range, 0.65 to 3.50 cm2) after ultrasound decalcification. There were two early deaths in octogenerian, high-risk patients, and two late deaths (6.45% early and 6.45% late mortality), none of them related to AVD. Postoperative follow-up included clinical evaluation and color Doppler echocardiography every 6 months. The aortic valve gradient was measured using a continuous-wave Doppler probe, and the AVA was calculated by the simplified continuity equation: AVA = aAOA x vLVOT/vAV.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrasonic decalcification of the aortic annulus during aortic valve replacement

Aortic valve replacement for calcifica aortic stenosis requires meticulous debridement of the aortic annulus to effect optimal valve seating. Since 1987, we have used ultrasonic energy to debride the aortic annulus during aortic valve replacement in 56 patients. In our experience, ultrasonic debridement of the annulus is superior to traditional methods of debridement, affords improved seating of the valve, and may allow placement of a larger valve. Our follow-up ranges from 2 to 32 months (mean follow-up, 13 +/- 9 months) with 0% incidence of paravalvular leak or valve failure. We advocate the use of ultrasonic debridement as an adjunctive tool in aortic valve replacement.