Wolfgang A. Goetz

A four-dimensional study of the aortic root dynamics

OBJECTIVE Although aortic root expansion has been well studied, its deformation and physiologic relevance remain controversial. Three-dimensional (3-D) sonomicrometry (200Hz) has made time-related 4-D study possible. METHODS Fifteen sonomicrometric crystals were implanted into the aortic root of eight sheep at each base (three), commissures (three), sinuses of Valsalva (three), sinotubular junction (three), and ascending aorta (three). In this acute, open-chest model, the aortic root geometric deformations were time related to left ventricular and aortic pressures. RESULTS During the cardiac cycle, aortic root volume increased by mean+/-1 standard error of the mean (SEM) 33.7+/-2.7%, with 36.7+/-3.3% occurring prior to ejection. Expansion started during isovolumic contraction at the base and commissures followed (after a delay) by the sinotubular junction. At the same time, ascending aorta area decreased (-2.6+/-0.4%). During the first third of ejection, the aortic root reached maximal expansion followed by a slow, then late rapid decrease in volume until mid-diastole. During end-diastole, the aortic root volume re-expanded by 11.3+/-2.4%, but with different dynamics at each area level. Although the base and commissural areas re-expanded, the sinotubular junction and ascending aorta areas kept decreasing. At end-diastole, the aortic root had a truncated cone shape (base area>commissures area by 51.6+/-2.0%). During systole, the root became more cylindrical (base area>commissures area by 39.2+/-2.5%) because most of the significant changes occurred at commissural level (63.7+/-3.6%). CONCLUSION Aortic root expansion follows a precise chronology during systole and becomes more cylindrical - probably to maximize ejection. These findings might stimulate a more physiologic approach to aortic valve and aortic root surgical procedures.

Anterior mitral leaflet mobility is limited by the basal stay chords.

Background We hypothesize that 2 tendon‐like anterior basal stay chords, which remain taut during the entire cardiac cycle, limit the motion of the anterior mitral leaflet. Methods and Results Sonomicrometric crystals were implanted in 6 sheep at the insertion of stay chords at anterior mitral leaflet (S1 and S2), papillary muscle tips, fibrous trigones, mitral annulus, and the tip of the anterior leaflet (AL). Distances between crystals were recorded before and after section of stay chords. During the cardiac cycle, the angle &agr; between mitral annulus and AL changed by +54.2±12.4 degrees; the angles between mitral annulus and S1 (&bgr;1) changed by +25.7±14.6 degrees, and between mitral annulus and S2 (&bgr;2) by +20.4±7.8 degrees. During diastole, AL twice crossed the virtual plane formed by the stay chords: during E‐wave by a maximum of 6.5 mm (mean, 2.5±2.2 mm) and during A‐wave by a maximum of 3.2 mm (mean, 1.7±0.9 mm). After section of both stay chords, total anterior mitral leaflet motion increased as follows: AL, +6.9±3.4 degrees; S1, +13.1±4.4 degrees; and S2, +30.9±11.7 degrees (P<0.05). Conclusions Although the lateral movement of anterior mitral leaflet is limited by stay chords, the midportion moves unimpaired toward the septum, like a sail, between the 2 stay chords during diastole. A diastolic left ventricular‐inflow and systolic left ventricular‐outflow funnel mechanism is created. Stay chord section increased lateral anterior mitral leaflet movement. (Circulation. 2003;107:2969‐2974.)

Impairment of pericardial leaflet structure from balloon-expanded valved stents

OBJECTIVE Malpositioning is one of the major problems in transcatheter aortic valve implantation. To evaluate the influence of mechanical balloon inflation on aortic valve stent positioning, the expansion process and the impact on the valve leaflets structure were investigated. METHODS Custom-made stents were laser cut from a 22-mm diameter stainless steel tube and mounted with a glutaraldehyde-treated bovine pericardial valve. The valved stents were crimped onto a standard balloon catheter and expanded by inflation of the balloon with 2 bar for 3 seconds. Expansion was studied using a high-speed camera, and the histology of the pericardial tissue was analyzed. RESULTS The valved stents were fully expanded within 3 seconds. Balloon inflation was observed to be asymmetric starting proximally. At the beginning of expansion, the valved stents were pulled proximally. During further inflation, the stents slipped distally on the balloon and experienced a total displacement of 13.5 mm. Macroscopic examination showed severe imprinting of the stent struts into the pericardial tissue. Histology revealed disrupted tissue layers and collagen fibers. CONCLUSIONS Analysis of valved stent expansion showed a displacement of the stent on the catheter during balloon inflation. Therefore, precise placement of the valved stent cannot be accomplished. Histologic analysis of the expanded pericardial tissue revealed disruption of collagen fibers. Disruption of pericardial tissue structures due to balloon expansion may result in early functional valve failure.

A differentiable, periodic function for pulsatile cardiac output based on heart rate and stroke volume

Many mathematical models of human hemodynamics, particularly those which describe pressure and flow pulses throughout the circulatory system, require as specified input a modeling function which describes cardiac output in terms of volume per unit time. To be realistic, this cardiac output function should capture, to the greatest extent possible, all relevant features observed in measured physical data. For model analysis purposes, it is also highly desirable to have a model function that is continuous, differentiable, and periodic. This paper addresses both classes of needs by developing such a function. Physically, the present function provides an accurate model for flow into the ascending aorta. It is completely specified by a minimal number of standard input parameters associated with left ventricle dynamics, including heart rate, mean cardiac output, and an estimation of the peak-to-mean flow ratio. Analytically, it can be expressed as a product of two continuous, differentiable and periodic factors. Further, the Fourier expansion of this model function is shown to be a finite Fourier series, and explicit closed-form expressions are given for the non-zero coefficients in this series.

Truly stentless molded autologous pericardial aortic valve prosthesis with single point attached commissures in a sheep model.

OBJECTIVE Aortic valve cusp extension and free-hand aortic valve replacement with autologous pericardium has been described. The long-term results were shown to be comparable with commercially available aortic bioprostheses. Nevertheless the relatively demanding surgical technique could not find wide acceptance. We developed a new design of a molded aortic valve, fashioned from autologous pericardium, treated briefly with glutaraldehyde, and simplified the implantation technique using single point attached commissures (SPAC). METHODS Molded autologous valve prostheses were implanted in the subcoronary aortic position in 10 sheep with the commissures connected to the aortic wall at three single commissural points (SPAC). The prosthesis mean size was 21.6+/-1.3 mm and the construction time (excluding 10 min glutaraldehyde treatment) was 6.2+/-1.2 min. Cardiopulmonary bypass and cross-clamp time was 111.1+/-12.4 min and 75.0+/-16.3 min, respectively. Six sheep were euthanized after 201.2+/-10.3 days (6 months) and four sheep were euthanized after 330.8+/-6.5 days (11 months) postoperatively. RESULTS In all sheep, the valve was immediately competent. At sacrifice, SPAC has proven to be well anchored to the aortic wall and the pericardial valve to be pliable in all cases. The maximum transvalvular gradient after cardiopulmonary bypass and at sacrifice was 3.7+/-2.2 mmHg and 10.6+/-5.2 mmHg, respectively. CONCLUSIONS This new truly stentless molded autologous aortic valve with simplified implantation technique (SPAC) makes a reliable implantation in a standard timeframe possible. The simplicity of construction, low cost and absent need for anticoagulation of this molded autologous aortic bioprosthesis offers an attractive alternative and not only for patients in the developing world.

Kinking of the atrioventricular plane during the cardiac cycle.

Systolic descent of the atrioventricular plane toward the relatively stationary left ventricular apex is well described. As the atrioventricular plane includes two separate valvular units, systolic atrioventricular plane displacement should not be homogenous. In 6 sheep, sonomicrometric crystals were implanted at the base of the right coronary sinus, anterolateral and posteromedial fibrous trigones, posterior mitral annulus, left ventricular apex, and the tips of the anterior and posterior mitral leaflets. The aortomitral angle was calculated and related to simultaneous left ventricular and aortic pressures and mitral valve movement. The aortomitral angle was largest at end diastole (150.73° ± 15.48°). During isovolumic contraction, it narrowed rapidly to 144.90° ± 16.64°, followed by a slower narrowing during ejection until it reached its smallest angle at end systole (139.66° ± 16.78°). During isovolumic relaxation, the aortomitral angle increased to 143.66° ± 16.02° at the beginning of diastole. During the first third of diastole, it narrowed again to 141° ± 16.24° before re-expanding to maximum at end diastole. During systole, the atrioventricular plane descended non-homogeneously toward the apex, with kinking at the hinge between the aortic and mitral annulus plane. This deformation of the atrioventricular plane has relevance in valve surgery.

Mitral valve repair with the new semirigid partial Colvin-Galloway Future annuloplasty band.

OBJECTIVE Various devices have been proposed for ring stabilization in patients with mitral valve disease. This study reports the intermediate-term results of mitral valve repair with a new semirigid partial annuloplasty ring in a large series of patients. METHODS A total of 437 consecutive patients were analyzed who underwent mitral valve reconstruction with annuloplasty using the Colvin-Galloway Future band at the German Heart Center in Munich between 2001 and 2005. A total of 237 patients (54.2%) underwent isolated mitral valve repair, and 200 patients (45.8%) underwent a combined procedure. The follow-up is 97% complete (mean follow-up of 405 survivors 2.1 +/- 1.1 years). RESULTS Overall 30-day mortality was 2.7%. Twenty patients (4.6%) died later after an average of 1.1 +/- 1.1 years. Actuarial survival at 4 years after isolated mitral valve reconstruction and combined procedures was 91% +/- 4% and 87% +/- 2.5%, respectively (P < .001). Twelve patients (2.7%) required a mitral valve reoperation after an average of 4.5 +/- 4.3 months. Five of these reoperations were required for band dehiscence, and 1 reoperation was required for band fracture. Freedom from reoperation at 4 years was 97% +/- 0.9%. At the latest follow-up, 93.5% of the patients showed trivial or mild mitral valve regurgitation, and 86.4% of the patients showed New York Heart Association functional class I or II. CONCLUSION Mitral valve annuloplasty with the Colvin-Galloway Future band can be performed with a low early and late mortality and an excellent functional outcome. The low incidence of reoperation demonstrates that the Colvin-Galloway Future band is a safe and effective device. The importance of secure anchoring of the device in the mitral annulus has to be emphasized to prevent band dehiscence.

Mitral Valve Incompetence Following Blunt Chest Trauma After Mitral Valve Repair - Recognition by Three-dimensional Echocardiography

We present a unique case of mitral incompetence following blunt chest trauma in a 46-year-old woman who had undergone successful mitral valve repair 2 years before the accident. Three-dimensional echocardiography revealed the precise pathology, with partial avulsion of the annuloplasty ring and rupture of chordae tendineae.We present a unique case of mitral incompetence following blunt chest trauma in a 46-year-old woman who had undergone successful mitral valve repair 2 years before the accident. Three-dimensional echocardiography revealed the precise pathology, with partial avulsion of the annuloplasty ring and rupture of chordae tendineae.

Effect of Leaflet Geometry on Mechanical Performance of Stentless Pericardial Aortic Valves – A Dynamic Simulation

Recent developments in aortic valve replacement include the truly stentless pericardial bioprostheses with Single Point Attached Commissures (SPAC). The leaflet geometry available for these valves can be a simple tubular or a complex three-dimensional molded structure resembling the natural valve. We compared mechanical performance of these two valve designs via dynamic simulation. Surface models representing a tubular valve and a molded valve incorporating the aortic root of 25 mm in diameter were created. An elastic modulus of 8 MPa and a density of 1,100 kg/m3 were assigned to the pericardial leaflet tissue. Time-varying physiological pressure loadings over a full cardiac cycle were applied on the upper and lower aortic root wall, and aorto-ventricular pressure gradient applied on the valve leaflets. The maximum effective valve orifice area during systole is 400.6 and 633.5 mm2 for the tubular and the molded valves, respectively. When fully closed, the free edges in the molded valve form S-shaped lines characterized by twisting at the valve center, a phenomenon not apparent in the tubular valve. Consequently, the coaptation height in the former is nearly four times greater than in the latter, being 4.5 and 1.2 mm, respectively. Computed compressive stress indicates that high magnitude in the tubular valve prevails at the commissure, along the inter-leaflet margin and the leaflet basal attachment line, while in the molded valve it occurs at the center of the free edge and on the leaflet belly. The highest stress magnitude in the tubular is 3.83 MPa versus 1.80 MPa in the molded. The molded leaflet geometry resembling the natural valve performs better than the simple tubular geometry for the SPAC valves, by producing greater effective orifice area, better coaptation properties, and lower magnitude in compressive stress, which should translate into enhanced valve efficacy and durability.