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Biomedical subjects

C M Duran

Publications and source records attributed to C M Duran.

At least 19 recordsLinked to original sources
PubMed2001

Hemodynamic evaluation of a new stentless autologous pericardial mitral valve.

BACKGROUND: There is no satisfactory mitral valve prosthesis. An ideal mitral valve substitute should be biologic, nonantigenic, and anatomically correct. METHODS: We developed a stentless, chordal-supported (including anterior basal stay chords) mitral valve made with glutaraldehyde-treated autologous pericardium. Eight such prostheses were implanted in sheep. RESULTS: Seven animals survived the operation and were studied postoperatively immediately, at 1 week, and at 1 month. Simultaneous left ventricular and left atrial pressures showed peak and mean transvalvular pressure gradients of 6+/-2 mm Hg and 1+/-1 mm Hg, respectively. Echocardiography performed intraoperatively and then 1 week and 1 month postoperatively showed normal valve leaflet movements. Color and pulsed Doppler echocardiography showed no sign of transvalvular stenosis or regurgitation. Effective orifice area was 5.39+/-0.35 cm2 at intraoperative, 5.51+/-0.29 cm2 1 week after operation (n = 5), and 5.51+/-.28 cm2 1 month after operation (n = 3). Three animals were sacrificed at 19 days and at 1 and 3 months. One animal is alive at 10 months. CONCLUSIONS: This new stentless pericardial mitral valve performed satisfactorily with low gradients and no regurgitation. Possible advantages of this pericardial valve are excellent hemodynamics, ease of construction and implantation, lack of immunogenicity, and low cost. Similarly designed valves but with a shorter nonglutaraldehyde treatment time have been used in 3 sheep monitored for more than 3 months.

Animals↗
PubMed2001

A new method for the preservation of aortic valve homografts.

BACKGROUND AND AIM OF THE STUDY: Aortic valve homografts were treated with 50% ethanol and glycerol followed by freeze-drying (D-Hydro). Comparative results of fresh versus D-Hydro-treated aortic roots implanted for up to nine months in the descending aorta of sheep with induced aortic regurgitation (AR) are reported. METHODS: Six fresh and six D-Hydro valves were implanted in 12 sheep for three, six and nine months, and echocardiography and pressures were taken at surgery and sacrifice. Tissue sections were stained with hematoxylin and eosin, von Kossa, Masson's trichrome, Movat's pentachrome, von Willebrand factor, CD3 (a T-cell marker) and smooth muscle alpha-actin. RESULTS: No grafts had increased gradients after implantation, or at sacrifice. At explantation, fresh homografts showed early pannus formation followed by thrombus, annular dilatation and wall calcification. Leaflets were thickened and progressively retracted. All had severe AR. The appearance of D-Hydro-treated homografts was normal, except for mild leaflet retraction in three, resulting in AR (in two animals the induced AR had healed). Histologically, a T-cell-mediated reaction was evident in the fresh homografts, and collagen distortion was noted. Calcification was present in all fresh specimens and was severe at nine months. D-Hydro roots showed only minor calcification in the six-month samples. Normal collagen, and a complete layer of von Willebrand factor-stained cells were present at three months. At nine months, cell rehabitation extended for two-thirds of the leaflets (alpha-actin +). The inflammatory reaction was very mild, with CD3+-stained cells absent in most samples. CONCLUSION: Aortic valve homografts treated with the D-Hydro freeze-drying method performed better than fresh homografts due to the absence of thrombus and annulus dilatation, limited calcification, and rehabitation of the aortic wall and parts of the leaflet by myofibroblasts, as well as the presence of a complete endothelial layer on the aortic wall and leaflet.

Animals↗
PubMed2000

Pathogenic mechanisms in rheumatic carditis: focus on valvular endothelium.

To clarify immune-mediated mechanisms in rheumatic heart disease caused by group A streptococcal infection, valve tissues from rheumatic patients with valvular heart disease who required valve replacement were studied for reactivity with monoclonal anti-CD4 or anti-CD8 monoclonal antibodies or anti-vascular cell adhesion molecule-1 (VCAM-1). At the valve surface, CD4(+) and CD8(+) T lymphocytes were adherent to valve endothelium and penetrated through the subendothelial layer. T cell extravasation into the valve through the surface valvular endothelium appeared to be an important event in the development of rheumatic heart disease. VCAM-1 was expressed on the valvular endothelium in rheumatic valves. Evidence suggested that the pathogenesis of rheumatic heart disease involved the activation of surface valvular endothelium with the expression of VCAM-1 and the extravasation of CD4(+) and CD8(+) lymphocytes through the activated endothelium into the valve. Lymphocytic infiltration through the valve surface endothelium has not been appreciated as a potential initiating step in disease pathogenesis.

Adolescent↗
PubMed2000

Activation of myocardial angiogenesis and upregulation of fibroblast growth factor-2 in transmyocardial-revascularization-treated mice.

OBJECTIVE: To evaluate the growth factor responses associated with myocardial angiogenesis. DESIGN: Mice were treated with transmyocardial revascularization (TMR) and evaluated for angiogenic and growth factor responses. METHODS: TMR was performed via thoractomy with a 27 g needle. At 2, 5, and 7 days post-treatment, hearts were removed from the TMR treated and control groups, then assayed for angiogenesis, fibroblast growth factor (FGF)-2 expression and vascular endothelial cell growth factor (VEGF) expression. RESULTS: TMR caused an angiogenic reaction in the myocardial blood vessels at 7 days post-TMR treatment. Elevated FGF-2 corresponded with increased TMR related angiogenesis. VEGF levels only increased in hearts that were prewounded then TMR treated. CONCLUSIONS: The data show that TMR stimulates myocardial angiogenesis. The angiogenic reaction is mediated by FGF-2 which increased in most experimental treatment groups. The VEGF response was more specific, requiring prewounding then TMR treatment for a VEGF increase.

Animals↗
PubMed2000

Significant increase of aortic root volume and commissural area occurs prior to aortic valve opening.

BACKGROUND AND AIM OF THE STUDY: The increased use of autologous, homologous or heterologous aortic root demands a detailed knowledge of its anatomy and function. The advent of 3-D digital sonomicrometry offered the opportunity to acquire precise information on the root and leaflet movements during the cardiac cycle. METHODS: Under cardiopulmonary bypass, sonomicrometry crystals were implanted in the aortic root and valve of eight sheep. Crystals were sutured at each commissure (n = 3), the top of the sinotubular junction (n = 3), lowest point of the annulus (n = 3), and leaflet tip (n = 3). 3-D coordinates of each crystal were recorded, together with left ventricular and aortic root pressures and ECG. When the animal had returned to a stable hemodynamic condition, the maximum and minimum distances between two crystals, and areas between three crystals, were calculated. Changes in root volume and leaflet position were time-related to the pressure changes. RESULTS: The most significant change between maximum and minimum distance between crystals during the cardiac cycle occurred at the commissural level. Similarly, the triangle defined by the three commissural crystals showed the greatest change in area (47%). The root volume increased by an average of 22%; about 40% of this increase occurred during the isovolumic phase. The aortic leaflets began to open before ejection. CONCLUSION: We postulate that aortic valve opening is initiated by the outward pull of the commissures. These findings should impact on aortic root surgery.

Animals↗
PubMed2000

A study of the junction between glutaraldehyde-treated allogeneic aorta and host aorta.

BACKGROUND AND AIM OF THE STUDY: Stentless aortic valve bioprostheses have become popular because of their superior hemodynamics and expected increased durability. However, the stentless bioprosthesis differs from stented valves in that glutaraldehyde (GA)-treated tissue is implanted in direct contact with the native aorta. The effect of GA-treated tissue on host tissue has not been reported. METHODS: In order to analyze the effect of GA in the healing process, sheep descending aortic conduits treated with 0.625% GA were inserted in the descending thoracic aorta of 10 adult sheep. The implants were removed after 4, 5, 10, 12, 15, 25, 30, 32, 60 and 120 days. The upstream and downstream junctions were evaluated macro- and microscopically, and by immunohistology for smooth muscle cell alpha-actin and von Willebrand factor. RESULTS: By day 60 of implantation, the GA-treated conduits were calcified. By days 60 and 120, the calcification had spread to the host aorta, and was seen as foci of calcification in the junctional area. Acellular areas were also seen in the host aorta near the anastomosis. A fibrotic layer spanning the abluminal aspect of the junction between the implant and host aorta was present at day 4 and continued through 120 days. This layer was characterized by a progressive increase in collagenous matrix and cellularity, as well as new blood vessel formation. The luminal aspect of the junction had a neointimal layer of variable thickness containing alpha-actin-expressing cells covered by a monolayer of von Willebrand factor-expressing cells, seen at 15-30 days and present through 120 days. CONCLUSION: In our model, implanting GA-fixed tissue in direct contact with living tissues resulted in cell death and calcification of host tissue within 60 days. The integrity of the junction did not appear to be compromised. This may be of interest in light of the increased popularity of the stentless aortic bioprosthesis.

Actins↗
PubMed1999

Expanding indications for the Ross procedure.

The pulmonary autograft procedure has been shown to provide excellent hemodynamic results in young patients with aortic pathology. However, the use of this procedure in those with more complex aortic disease has not been extensively evaluated. The purpose of this report is to present the application of the Ross procedure in a 21-year-old man with extensive acquired aortic root pathology, both subannular and supraannular, and prosthetic valve dysfunction after two previous procedures.

Adult↗
PubMed1999

Behavior of vital and killed autologous pericardium in the descending aorta of sheep.

OBJECTIVES: Cardiovascular implants of fresh autologous pericardium produced mixed results including fibrosis with retraction or thinning and dilatation. The reasons for these differences are unknown but may involve activation of cells intrinsic to the tissue implant. To better understand the behavior of autologous pericardial implants, we studied the outcomes of vital pericardium (fresh) versus ethanol-killed pericardium. METHODS: Fresh and ethanol-killed autologous pericardium was transplanted as a patch, a conduit, or a rectangular flap bisecting the lumen in the descending aorta of sheep. The implants, recovered at 1, 5, 10, 15, and 30 days, were evaluated macroscopically and microscopically and by immunohistologic studies. RESULTS: Fresh implants showed good preservation with fibrin deposition on day 15. Microscopically, cells positive for alpha-actin and von Willebrand-related antigen appeared in the fibrin by day 10. By day 30 the flap was fibrotic and retracted whereas the patch and conduit retained their original appearance on the luminal aspect. An endothelium-like layer expressing von Willebrand-related antigen was present in the patch and conduit but absent in the flap. In contrast, the ethanol-killed implants were free of fibrin by day 10. By day 30, there were no signs of fibrosis or retraction, and a surface layer of cells expressing von Willebrand-related antigen, characteristic of endothelial cells, was present on all implants. All ethanol-killed implants were repopulated by host cells. CONCLUSION: The transluminal flap is an interesting model for studying the behavior of intraluminal autologous pericardial cardiovascular implants. Killing of the pericardial implants alleviated the fibrosis and tissue retraction observed with fresh flap implants.

Actins↗
PubMed1999

Aortic root geometry: pattern of differences between leaflets and sinuses of Valsalva.

BACKGROUND AND AIMS OF THE STUDY: Growing interest in aortic root replacement with the use of stentless auto-, homo- and xenografts, and new developments in aortic valve conservation demand a deeper understanding of the normal aortic root anatomy. METHODS: Ten cryopreserved human aortic roots were pressurized, fixed and measured directly (leaflet free edge and attachment) and using three-dimensional computed tomography imaging software (sinus of Valsalva height and volume). RESULTS: The mean of the measurements of all four parameters yielded a pattern in which the non-coronary sinus (N) structures had the greatest dimensions followed by the right (R) and then the left (L). Non-parametric ANOVA on each of these parameters also showed significant differences among the sinuses yielding a pattern of N > R > L. This pattern determined an angle of tilt between the plane at the base (annulus) and the plane intersecting the sinotubular junction with a mean value of 11 degrees. Linear regression indicated that this angle did not depend on the size of the base (annulus). CONCLUSIONS: The data showed a geometric pattern of the aortic root, with the structures of the non-coronary sinus being the largest followed by the right and then the left. The possible hemodynamic relevance and surgical implications of these findings need to be explored.

Aortic Valve↗
PubMed1999

Multiplane transesophageal echocardiography: a roadmap for mitral valve repair.

Multiplane transesophageal echocardiography (TEE) is useful in providing a detailed anatomic map for successful mitral valve repair. This report describes an approach, developed over the past two to three years, which helps to delineate valve anatomy in specific detail. Mid-esophageal views are selected to view different segments of the valve leaflets. When correlated with surgical anatomy, this approach is found to be both practical and useful.

Cardiac Surgical Procedures↗
PubMed1999

Critical analysis of the Ross procedure: do its problems justify wider application?

The Ross procedure has shown superior hemodynamic results in young patients with aortic root pathology. Wider application of the procedure is restricted by its technical complexity and potential associated problems. The mortality/morbidity associated with 130 consecutive patients who have had the Ross procedure using the root replacement implantation technique between October 29, 1990, and October 8, 1998 is summarized. New York Heart Association (NYHA) preoperatively was class I, 23.5%; class II, 64.7%; and class III, 11.8%; mean age was 36 years (range 3 to 67 years). Men accounted for 73.8% and women 26.2% of the series. Preoperative diagnosis was congenital, 80.7%; rheumatic, 5.3%; failed prosthesis, 7.0%; degenerative, 2.6%; and endocarditis, 4.4% with preoperative aortic insufficiency (AI) 7.9% 1+, 19.8% 2+, 29.7% 3+, and 42.6% 4+, respectively. At operation mean cross-clamp time was 201 minutes (range 102 to 280 minutes). Patient follow-up was 99.2% (1 patient lost to follow-up), and 94.4% were NYHA class I at follow-up and 5.6% class II. Postoperative AI was 0 to 1 + in 93.6% and 2+ or greater in 6.4%. Mean time to patient follow-up was 436 days (range, 20 days to 2,878 days). Thirty-day mortality rate was 1.5%; one patient died of mediastinal bleeding, and one from complications of acute pancreatitis. There was no late mortality. Early autograft explant occurred in one patient secondary to iatrogenic injury to the pulmonary autograft at the time of harvesting, and one late explant occurred secondary to proximal suture line dehiscence. Late autograft repair occurred in one patient secondary to a false aneurysm along the proximal suture line; one patient was reoperated for left main coronary stenosis relative to iatrogenic injury at the time of the procedure. Right ventricular outflow tract replacement has occurred in two patients. Postoperative morbidity and mortality for the Ross procedure, as shown in this series, remains low and supports broader application of the procedure.

Adolescent↗
PubMed1998

The Ross Procedure: current registry results.

BACKGROUND: The pulmonary autograft procedure for the treatment of aortic valve disease was developed and performed by Ross in 1967. The results he published in 1987 prompted increasing interest in the procedure. The International Registry of the Ross Procedure was established in 1993 to further examine longitudinal clinical outcomes. METHODS: The results from the Ross registry document the continued and growing interest in the procedure with 2,523 patients currently enrolled, representing 122 centers and 166 surgeons worldwide. RESULTS: Mortality (1987 to present) reported in the registry is 2.5%. It should be noted that follow-up stands at 70%. The most important issues for the registry to track are the incidence of reoperation for autograft failure and the fate of the pulmonary homograft. Reoperation for all valve-related problems is low (5.4%), with an autograft explant rate of 1.9%. Overall registry data indicate that the right ventricular outflow tract revision rate is 2.8%, with this decreasing by half to 1.3% in the 1987 to present subgroup. CONCLUSIONS: Rigorous analysis of outcomes is difficult with registry follow-up currently at 70%; however, the general conclusions derived from the registry are supported by other individual series with excellent follow-up. Success of the registry depends on judicious efforts by all participating surgeons and coordinators in documenting long-term patient results and reporting them to the registry.

Adolescent↗
PubMed1998

Cardiopulmonary response to maximal exercise in young athletes following the Ross procedure.

BACKGROUND: Aortic prosthetic devices offer limitations that make them less than optimal valve substitutes because the vast majority are innately obstructive, especially at increased levels of hemodynamic function. The present study is designed to demonstrate the hemodynamics of the pulmonary autograft in 11 conditioned athletes who have undergone the Ross (pulmonary autograft) procedure. Data was compared to a group of 13 age-matched "normal athletes." METHODS: All the Ross athletes had undergone the autograft procedure using the root replacement technique and were at least 3 months into their postrecovery phase. All athletes (both normal and Ross) underwent resting transthoracic echo followed by maximal exercise stress test (modified Bruce protocol) to exhaustion. Post-operative transesphogeal echocardiogram obtained within 90 seconds documented aortic valve gradient and velocity across the aortic valve. RESULTS: In the Ross athlete group, maximum heart rate was 188 beats per minute, peak aortic valve gradient at rest (mm Hg) 7.69 (mean), velocity across the aortic valve at rest (cm per second) 129.40 (mean), peak aortic valve gradient at maximal exercise (mm Hg) 16.30 (mean), velocity across the aortic valve at maximal exercise (cm per second) 190.00 (mean). In the normal athlete group, maximum heart rate was 176 beats/minute, peak aortic valve gradient at rest (mm Hg) 5.97 (mean), velocity across the aortic valve at rest (cm per second) 120.54 (mean), peak aortic valve gradient at maximal exercise (mm Hg) 14.61 (mean), velocity across the aortic valve at maximal exercise (cm per second) 190.23 (mean). CONCLUSION: The pulmonary autograft exhibits hemodynamic characteristics similar to the normal human aortic valve under conditions of enhanced cardiac output.

Aortic Valve↗
PubMed1998

Treated bovine and autologous pericardium for aortic valve reconstruction.

BACKGROUND: To determine the differences in clinical behavior of bovine versus autologous pericardium, all consecutive patients undergoing aortic valve reconstruction were reviewed. METHODS: Between October 1988 and December 1995, 91 patients (mean age 30 years) underwent reconstruction with bovine (n = 27) or autologous (n = 64) pericardium. RESULTS: There were 2 hospital deaths, 5 late deaths, and no embolic events. Dysfunction of the aortic reconstruction required reoperation in 6 bovine (infection 1, fibrocalcific 5) and in 5 autologous (infection 3, annulus dilatation 1, commissural tear 1). Actuarial survival and freedom from structural deterioration at 8 years were 82.2%+/-9.6% and 76.2%+/-10.7% for bovine and 91.05%+/-3.96% and 96.8%+/-2.25% for autologous pericardium, respectively. The last Doppler echocardiographic study showed a mean regurgitation (1 to 4+) and gradient in the bovine pericardium of 1.25+/-and 20.7 mm Hg and in the autologous pericardium of 1+ and 7.7 mm Hg. CONCLUSIONS: Aortic valve reconstruction with pericardium can be safely performed with low thromboembolic rate. At 8 years follow up, there is a difference in favor of the autologous pericardium.

Actuarial Analysis↗