The future of heart valve standards.
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Animals↗
Biomedical subjects
S P Nolan
Publications and source records attributed to S P Nolan.
Interventions to reduce decibel levels on patient care units.
The University of Virginia Health System inpatient satisfaction survey identified noise as the most important irritant to surgical inpatients. Analysis of the level and pattern of noise on patient floors and intensive care units was done with baseline measurements followed by then two separate interventions: 1) education of nursing and physician staff 2) closing patient room doors. A decibel meter (M-27 Dosimeter) recorded the noise level over 24 hours. Patients doors were open in the initial measurements. Next, three 1-hour education sessions were conducted by a surgeon and nursing supervisor to review noise-reduction strategies with the staff. These included using pagers in vibrate mode, minimizing overhead announcements, and conducting nurse reports and physician teaching sessions in classrooms away from the nurses' station. Finally, the doors were closed except as visitors and staff entered the room. Little impact was seen from staff education. Closing patient doors on surgical floors decreased noise an average of 6.0 dB, a change that patients can readily perceive. Conversely, intensive care unit patients are exposed to more noise with closed doors, presumably because most noise emanates from equipment within the room. A policy of closing patient floor room doors may increase patient satisfaction.
Communication↗
Is vertical vein ligation necessary in repair of total anomalous pulmonary venous connection?
BACKGROUND: In the repair of total anomalous venous connection, vertical vein ligation is recommended to eliminate left-to-right shunting. However, the small left heart chambers may not always tolerate the immediate increase in blood flow after combined repair and vein ligation. METHODS: A retrospective review of 23 infants and children undergoing correction of total anomalous pulmonary venous connection was undertaken to determine whether vertical vein ligation is a necessary component of successful surgical repair. In 14 patients this vein was ligated, whereas in 9 it was left patent. Six patients who underwent ligation and 5 who did not had pulmonary venous obstruction before operation. RESULTS: The operative mortality rate was 36% (5 of 14 patients) for the ligated group compared with 0% (0 of 9 patients) for the nonligated group (p = 0.06). All deaths occurred in patients with preoperative obstruction and a low mean left atrial pressure, and four of the deaths were directly attributable to left heart failure. Follow-up echocardiography in patients in whom the vertical vein was not ligated revealed adequate cardiac function and no residual left-to-right flow through the previously patent venous conduit. CONCLUSION: Vertical vein ligation during the repair of total anomalous pulmonary venous connection is not routinely necessary and actually may be undesirable in patients with preoperative obstruction, in whom the left heart chambers are particularly small.
Cardiac Surgical Procedures↗
Reflections on the evolution of cardiopulmonary bypass.
The concept of cardiopulmonary bypass is more than a century old. Although the first clinical application occurred in 1953, there were great deficits in knowledge and materials that had to be overcome before we could achieve the outcomes of cardiac surgery that we have today.
Cardiac Surgical Procedures↗
Synthesis and ligand binding of eta(6)-(2beta-carbomethoxy-3beta-phenyltropane) transition metal complexes.
The transition metal complexes [eta(6)- (2beta-carbomethoxy-3beta-phenyltropane)]tricarbonylchromium (3) and [eta(6)-(2beta-carbomethoxy-3beta-phenyltropane)] [eta(5)-(pentamethylcyclopentadienyl)]ruthenium(II)triflate (4) were synthesized from 2beta-carbomethoxy-3beta-phenyltropane (2, WIN 35,065) to further elucidate the influence of substituents on the 3beta-aryl on the affinity of the ligand for cocaine-binding sites at the dopamine transporter. The compounds were tested for their ability to displace bound [(3)H]WIN 35,428 (5) from rat caudate putamen tissue and for their ability to inhibit [(3)H]dopamine uptake. The binding affinity for 3 was 2-fold greater than those observed for cocaine (1) and 2, while the binding affinity for 4 was found to be 100-fold less than those of 1 and 2. In addition, 3 was equipotent with 1 and 2 in [(3)H]dopamine uptake inhibition studies, while 4 was 10-fold less potent. The potencies of the complexes 3 and 4 correlated well with the structure-activity relationships of other 2beta-carbomethoxy-3beta-aryltropane derivatives. These data further support a pharmacophore model in which the region occupied by the aryl ring is a lipophilic pocket with electropositive character.
Animals↗
Transatrial approach to posterior postinfarct ventricular septal defects.
Repair of posterior postinfarct ventricular septal defects via the transinfarct left ventriculotomy is technically challenging and can be associated with significant morbidity. A transatrial approach avoids incising through the acutely infarcted myocardium and, in selected cases, offers a safe and reliable repair of these defects.
Cardiac Surgical Procedures↗
Reduction of femoral arterial bleeding post catheterization using percutaneous application of fibrin sealant.
The number of cardiac catheterizations performed yearly is growing with correspondingly increasing amounts of morbidity, complications, and hospital costs. This study suggests that fibrin sealant instillation via an arterial sheath at the completion of femoral catheterization may improve hemostasis. Results using fibrin sealant in 12 unheparinized dogs documented significant reductions (McNemar's exact test) versus control for groin ecchymoses (1 versus 8, P = .008) and radiolabeled hematoma formation (0 versus 7, P = .016). Also swelling was less in the fibrin sealant treated groins when compared to control groins (1 versus 6, P = .125), but failed to reach statistical significance. Results in eight heparinized dogs (activated clotting time 374 +/- 22, mean +/- SEM) revealed a statistically significant reduction in signs of gross bleeding in the fibrin sealant-treated groins (1 versus 8, P = .016). This method may contribute to reduced morbidity, complications, and length of hospitalization. It may also allow for earlier patient mobilization after cardiac catheterization.
Administration, Cutaneous↗
1987: Anterolateral thoracotomy as an alternative to repeat median sternotomy for replacement of the mitral valve. Updated in 1995.
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Heart Valve Prosthesis↗
General surgical complications can be predicted after cardiopulmonary bypass.
OBJECTIVE: The authors review the general surgical complications of cardiopulmonary bypass, including newer procedures such as heart and lung transplantation, to identify patients at higher risk. SUMMARY BACKGROUND DATA: Although rare, the general surgical complications of cardiopulmonary bypass are associated with high mortality. The early identification of patients at increased risk for these complications may allow for earlier detection and treatment of these problems to reduce mortality. METHODS: A retrospective review was performed of 1831 patients undergoing cardiopulmonary bypass from 1991 to 1993. This was done to identify factors that significantly contributed to an increased risk of general surgical complications. RESULTS: Factors associated with an increased risk of general surgical complications included prolonged cardiopulmonary bypass (p < 0.005) and intensive care unit stay (p < 0.002), occurrence of arrhythmias (p < 0.001), use of inotropic agents (preoperatively or postoperatively p < 0.001), insertion of the intra-aortic balloon pump (preoperatively p < 0.005, postoperatively p < 0.001), use of steroids (p < 0.001), and prolonged ventilator support (p < 0.001). Multivariate analysis identified use of the intra-aortic balloon pump (p < 0.001) as the strongest predictor of the general surgical complications of cardiopulmonary bypass. A variety of factors not contributing significantly to an increased risk also were identified. CONCLUSIONS: Factors indicative of or contributing to periods of decreased end-organ perfusion appear to be significantly related to general surgical complications after cardiopulmonary bypass.
Aged↗
Mechanism of mitral leaflet excursion.
The factors that influence the extent of mitral leaflet opening (MLO) and closure (MLC) have not been defined. We hypothesized that left ventricular (LV) systolic function determines the rate of increase of the early diastolic left atrial (LA)-LV pressure gradient, which is responsible for the extent of MLO, and also the rate of change of the early systolic LV-LA pressure gradient, which determines the degree of MLC. Accordingly, global LV function was changed by altering left main coronary artery flow with LA pressure held relatively constant. LV end-systolic dimension and peak positive LV rate of pressure development (dP/dt) correlated best with the degrees of MLO and MLC, with average correlation coefficients of 0.88 and 0.68, and 0.86 and 0.72, respectively. Although transsecting the submitral apparatus resulted in flailing of the mitral leaflets during normal LV systolic function, the extents of MLO and MLC during LV systolic dysfunction were still influenced by LV systolic function. It is concluded that LV systolic function determines the extent (both opening and closure) of mitral leaflet excursion.
Animals↗
The search for standards.
The International Organization for Standardization (ISO) assigned the responsibility for developing valve standards to its technical committee on surgical implants. A sub-committee on cardiovascular implants and the working group for heart valves were formed more than 20 years ago. The working group has learned a great deal, not only from its experience with ISO, but most of all from the collaboration of its international experts representing science, engineering and manufacturing. The first valve standard was published in 1984, revised in 1989, and the next revision will probably be published in 1995. After the formation of this ISO working group in 1972, the U.S. Food and Drug Administration (FDA) developed regulations for the premarket approval of heart valves in the United States. The European Committee for Standardization (CEN) was subsequently formed and appointed a working group to develop heart valve standards for Europe. It rapidly became apparent that the lack of co-ordination and communication of three separate organizations writing documents with different requirements and tests would lead to inconsistent and conflicting requirements. The ultimate outcome could have been a threat to public welfare by limiting the availability of medical devices. The commitment to the harmonization of standards by CEN and ISO, and the recent FDA policy to participate actively in standards development, have greatly improved this situation. Past errors, omissions and inappropriate attitudes have often slowed the standards process or have resulted in incomplete standards. This learning experience, while painful, should point the way to more timely and complete standards development in the future.
Biomedical Engineering↗
The International Standard Cardiovascular implants--Cardiac Valve Prostheses (ISO 5840:1989) and the FDA Draft Replacement Heart Valve Guidance (Version 4.0)
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Documentation↗
High speed cine-radiographic study of aortic valve leaflet motion.
The leaflets of the aortic valve move extremely rapidly during opening and closing. To analyse this movement, radiopaque markers were placed on the aortic valves of four dogs during cardiopulmonary bypass. One to five months later the dogs were studied using x-ray, and the marker motion was recorded on cine-film at 500 frames/second. Simultaneous aortic pressure varied from 70/30 to 188/152 mmHg and heart rate from 33 to 150 bpm. Analysis of 19 systolic periods and 2500 cine-frames indicated that leaflet motion occurred in four phases: 1--rapid movement during initial opening, 2--a little movement near maximal excursion, 3--a slow movement during early closing and 4--a rapid movement to complete closure. Phases 1 and 4 averaged 17.6 and 16.5 msec respectively, and were independent of heart rate, whereas the length of phases 2 and 3 varied with heart rate. The leaflets moved 82% of their maximum excursion during rapid opening and 53% during rapid closure. Leaflet curvature reversed in both the radial and the circumferential directions during opening. The leaflet profile in the radial direction changed as follows: during rapid opening, the belly of the leaflet moved outward, first causing the leaflet to straighten and then to conform to the profile of blood flow. During closure the belly of the leaflet moved centrally, causing the leaflet to curve toward the ventricle. The leaflet profile in the circumferential direction indicated that during opening the midpoint of the leaflet leads the motion towards the aortic wall.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Distribution of low density lipoprotein in the branch and non-branch regions of the aorta.
Atherosclerosis occurs focally in branch segments of the artery. Understanding why these segments are more susceptible to the development of the disease is at the root of understanding atherogenesis. We investigated accumulation of low density lipoprotein (LDL) in the branch and non-branch regions of the aorta to determine why the disease develops in branch regions. Abdominal aortas and their major branches were harvested from 36 rabbits. Rabbit LDL was prepared from whole blood and radiolabeled with 125I. The aorta was incubated with radiolabeled LDL in the lumen at 37 degrees C, under intraluminal pressure of 2-3 mmHg, for 1 h. Disks of 1.8 mm diameter were punched from the branch and non-branch regions of the aorta, cryosectioned and the sections counted in a gamma counter. Protein bound radioactivity was determined by TCA precipitation. LDL accumulation was highest towards the aortic intima and declined sharply towards the media. LDL accumulation at any given depth was higher in the branch than non-branch region. LDL accumulation in the intimal-medial sections was 87% higher in the branch than non-branch region. Total LDL accumulation in the branch was almost twice that in the non-branch region. Mean LDL accumulation was also greater in the branch than non-branch region. The aorta was significantly thicker at the branch. LDL distribution profiles indicate that LDL is present in a greater concentration and over a greater depth in the branch than non-branch region. The tendency of the branch region to accumulate LDL in greater amounts may explain its susceptibility to atherosclerotic lesion development.
Animals↗
A mathematical model for the quantification of mitral regurgitation. Experimental validation in the canine model using contrast echocardiography.
BACKGROUND: Because the clearance of contrast from the left atrium (LA) relative to the left ventricle (LV) depends on the degree of mitral regurgitation (MR), we hypothesized that a mathematical model can be developed that would provide a quantitative estimation of MR from the washout of contrast from these chambers. METHODS AND RESULTS: After mathematically developing the model, we performed experiments in two groups of dogs with the use of contrast echocardiography. Group 1 consisted of nine dogs in which different degrees of MR were produced by creating ischemic LV dysfunction. Contrast was injected into the LV, and MR was graded visually on a scale of from 0 to 4+. Videointensity plots generated from the LA and LV were provided to the model. There was excellent correlation between visual assessment of MR and model-derived regurgitant fraction in the 33 stages: y = 0.16x + 0.002 (r = 0.97, p less than 0.001, SEE = 0.06). To obtain a more quantitative validation, we placed electromagnetic flow probes on the aorta and just cephalad to the mitral annulus in six dogs (group 2) during cardiopulmonary bypass. Different degrees of MR were produced by chordal traction and/or myocardial ischemia. Regurgitant fraction was calculated at each stage from the flow probe and videointensity data. There was excellent correlation between flow probe and model-derived regurgitant fraction (y = 0.90x + 0.03; r = 0.96, p less than 0.001, SEE = 0.06), and close interobserver and intraobserver correlations were noted using flow probe and contrast echocardiographic data. CONCLUSIONS: A mathematical model that uses the clearance of contrast from the LA relative to the LV can be used to accurately measure the severity of MR. These findings may have important practical implications for the quantification of MR.
Animals↗
Change in endothelial cell morphology at arterial branch sites caused by a reduction of intramural stress.
Arterial branch sites have very high intramural stresses at physiologic intraluminal pressures; the same sites have a predilection for atherosclerosis. The effect of intramural stress on endothelial cell morphology was investigated. Five rabbits had permanent casts placed around a segment of the abdominal aorta-left renal artery branch area during controlled hypotension, thus reducing intramural stress without narrowing the lumen. These five animals, and three normal rabbits, were sacrificed after 4-8 weeks, and the vessels were perfused with buffered 2.5% glutaraldehyde for 2 h at 100 mm Hg pressure. The aortas were examined by scanning electron microscopy. In normal aortas, the distal region of the ostia of the left renal and celiac arteries just beyond the flow divider displayed many morphologically altered endothelial cells ranging from spindle shape to cobble-stone shape. The same aortic area of casted rabbits, as well as the straight abdominal aorta in all rabbits, showed a smooth surface of endothelial cells with intact cell borders and no morphologically altered cells. At branch sites, the occurrence of morphologically altered endothelial cells may be due to increased intramural stress. When intramural stress is reduced, the morphology of branch endothelial cells changes to resemble that of the unbranched regions. In conclusion, endothelial cell morphology changes in response to changes in intramural stress.
Animals↗
Optimization of a trileaflet valve design.
This study investigates the fundamental principles that should govern the basic design of an optimal trileaflet valve. The geometry of the leaflets is described in terms of radius of the base (Rb), radius of the commissures (Rc), height of the valve (H), height of the commissures (Hs), and angle of the open leaflet to vertical (beta). Using computer-aided design software and these design parameters, a computer model of the valve was constructed. Choosing the parameters empirically did not produce an optimal valve. The four criteria for optimal performance were defined as: (1) a certain minimum coaptation height, (2) no folds in the leaflet, (3) minimum valve height, and (4) minimum leaflet flexion. Mathematical relationships were established between the design parameters and the performance parameters. These relationships indicated that the parameters Rc, Hs, and beta could be used to minimize valve height; however, a reduction in valve height must be balanced against the accompanying increase in leaflet flexion. For an optimal valve, the design parameters were Rb = 10 mm, then Rc = 8 to 10 mm, H = 11.5 mm, Hs = 2.4 to 2.6 mm, and beta = 4 degrees to 11 degrees . The optimal valve of any radius can be designed by scaling Rc, H, and Hs with respect to Rb. These design parameters were similar to those of the natural aortic valve. Trileaflet bioprosthetic valves designed on these principles are expected to have enhanced efficiency and longevity.
Bioprosthesis↗
Four years' experience with fibrin sealant in thoracic and cardiovascular surgery.
A single-donor fibrin sealant system was used in 689 thoracic and cardiovascular surgical procedures over the 4-year period between April 1, 1985, and March 31, 1989. An excellent overall success rate (646/689, 94% effective) was achieved with specific applications, including reduction of leakage of air (29/33, 88% effective), blood (595/634, 94% effective), and fluid (14/14, 100% effective), as well as positioning of anatomical structures such as coronary bypass grafts (8/8, 100% effective). Application methods included use of spray bottles (477/497, 96% effective), syringes (165/186, 89% effective), and a Silastic cannula through the flexible fiber-optic bronchoscope (4/6, 67% effective). The system was used in a wide variety of cardiac, pulmonary, esophageal, and vascular procedures to seal staple lines, suture lines, anastomoses, conduits, fistulas, and raw surfaces. No complications with this single-donor system secondary to blood-borne disease have been documented. Overall infection occurred at a nominal rate (16/689, 2%). Thus, fibrin sealant has been a useful tool to control the leakage of air, blood, and fluid during a wide variety of thoracic and cardiovascular procedures and may be of benefit to other surgeons.
Aerosols↗