Comparative Study of the Amount of Backflow Produced by Four Types of Aortic Valve Prostheses

1984 ◽  
Vol 106 (1) ◽  
pp. 66-71 ◽  
Author(s):  
H. N. Sabbah ◽  
P. D. Stein
Keyword(s):  
Aortic Pressure ◽  
Low Cardiac Output ◽  
Prosthetic Valves ◽  
Mechanical Valves ◽  
Disk Valve ◽  
Pump Rate ◽  
Valve Leakage ◽  
Clinically Significant ◽  
Valve Prostheses ◽  
Mean Aortic Pressure

To determine the extent of backflow encountered with currently used prosthetic valves, four types of aortic valves with comparable orifice diameters were tested in a pulse duplicating system. These were a Hancock porcine valve, a Lillehei-Kaster pivoting disk valve, a St. Jude bileaflet valve and a Bjo¨rk-Shiley tilting disk valve. Mean aortic pressure was sequentially increased from 83 to 147 mmHg, keeping the pump rate essentially constant (69–73 strokes/min). The porcine valve produced the least amount of total backflow (backflow due to closure plus leakage backflow) (1.6 to 2.4 mL/stroke). Among the mechanical valves the Bjo¨rk-Shiley valve showed the least amount of total backflow (5.0 to 6.0 mL/stroke). At a mean aortic pressure of 100 mmHg and a low cardiac output of 2 L/min, the total backflow with the porcine valve was only 6 percent of forward flow; whereas it was 19 percent with the Lillehei-Kaster valve, 22 percent with the St. Jude valve and 18 percent with the Bjo¨rk-Shiley valve. Leakage backflow at a given level of mean aortic pressure was, as expected, directly related to the annular clearance area. It is concluded that the Hancock valve showed the least amount of backward flow, which would be particularly beneficial in low output states. In the presence of normal hemodynamics, the amount of backflow with the three mechanical valves appeared to be well below the level of backflow considered to be clinically significant.

Modeling Endoleaks and Collateral Reperfusion following Endovascular AAA Exclusion

2003 ◽  
Vol 10 (3) ◽  
pp. 424-432 ◽  
Author(s):  
Chuh K. Chong ◽  
Thien V. How ◽  
Geoffrey L. Gilling-Smith ◽  
Peter L. Harris
Keyword(s):  
Stent Graft ◽  
Aortic Pressure ◽  
Type I ◽  
Type Ii ◽  
Pump System ◽  
Type Ii Endoleak ◽  
Type I Endoleak ◽  
The Impact ◽  
Mean Aortic Pressure

Purpose: To investigate the effect on intrasac pressure of stent-graft deployment within a life-size silicone rubber model of an abdominal aortic aneurysm (AAA) maintained under physiological conditions of pressure and flow. Methods: A commercial bifurcated device with the polyester fabric preclotted with gelatin was deployed in the AAA model. A pump system generated physiological flow. Mean and pulse aortic and intrasac pressures were measured simultaneously using pressure transducers. To simulate a type I endoleak, plastic tubing was placed between the aortic wall and the stent-graft at the proximal anchoring site. Type II endoleak was simulated by means of side branches with set inflow and outflow pressures and perfusion rates. Type IV endoleak was replicated by removal of gelatin from the graft fabric. Results: With no endoleak, the coated graft reduced the mean and pulse sac pressures to negligible values. When a type I endoleak was present, mean sac pressure reached a value similar to mean aortic pressure. When net flow through the sac due to a type II endoleak was present, mean sac pressure was a function of the inlet pressure, while pulse pressure in the sac was dependent on both inlet and outlet pressures. As perfusion rates increased, both mean and pulse sac pressures decreased. When there was no outflow, mean sac pressure was similar to mean aortic pressure. In the presence of both type I and type II endoleaks, mean sac pressure reached mean aortic pressure when the net perfusion rate was low. Conclusions: In vitro studies are useful in gaining an understanding of the impact of different types of endoleaks, in isolation and in combination, on intrasac pressure after aortic stent-graft deployment.

Design of Prosthetic Heart Valve and Application of Additive Manufacturing

2021 ◽  
pp. 482-491
Author(s):  
Dheeman Bhuyan
Keyword(s):  
Additive Manufacturing ◽  
Heart Valve ◽  
Design Process ◽  
Prosthetic Heart Valve ◽  
Animal Tissue ◽  
Heart Valve Prostheses ◽  
Mechanical Valves ◽  
Valve Prostheses

Heart valve prostheses are well known and can be classified in two major types or categories: biological and mechanical. Biological valves (i.e., Homografts and Heterografts) make use of animal tissue as the valving mechanism whereas mechanical valves make use of balls, disks, and other mechanical valving mechanism. Mechanical valves carry considerable risk and require lifelong medication. The design of these valves is usually done on a “one size fits all” basis, with only the diameter changing depending on the model being produced. The author seeks to present an application of additive manufacturing in the design process for mechanical valves. This is expected to provide patients with customized prostheses to match their physiology and reduce the risk associated with the implantation.

Femoral circulatory responses to lumbar nerve stimulation in developing swine

1981 ◽  
Vol 240 (4) ◽  
pp. H505-H510
Author(s):  
N. M. Buckley ◽  
P. Brazeau ◽  
I. D. Frasier ◽  
P. M. Gootman
Keyword(s):  
Nerve Stimulation ◽  
Low Frequency ◽  
Aortic Pressure ◽  
Nerve Fibers ◽  
High Frequency Stimulation ◽  
Mean Flow ◽  
Frequency Stimulation ◽  
Pentobarbital Sodium Anesthesia ◽  
Carotid Arterial ◽  
Mean Aortic Pressure

The maturation of femoral circulatory responses to efferent lumbar nerve stimulation was tested in 51 developing swine (1 day-3 mo old) under pentobarbital sodium anesthesia (10-30 mg/kg). Aortic pressure, heart rate, and femoral and carotid arterial flows (measured by electromagnetic flow transducers) were recorded simultaneously. Femoral vascular resistance was calculated as mean aortic pressure/mean flow. Transection of the lumbar nerve fibers below the last ganglion in the sympathetic chain did not after femoral resistance in day-old animals but decreased femoral resistance in swine 1 wk of age and older. Efferent lumbar nerve stimulation at various combinations of frequencies and intensities revealed an atropine-blockable vasodilator component in the femoral circulatory response in swine 1 mo of age and older. After alpha-adrenergic receptor blockade with phentolamine (0.25 or 0.5 mg/kg), femoral vasodilation occurred during low-frequency and -intensity stimulation of the lumbar nerve only in animals 1 mo of age and older. Acetylcholine (2 micrograms ia) caused a decrease in femoral resistance at all ages. Vasoconstrictor effects of high-frequency stimulation (5-10 Hz) were present at all ages and were age dependent. The results of these experiments suggest that the femoral circulation in swine at birth in innervated by functionally active vasoconstrictor fibers, which do not provide a tonic influence on femoral resistance until late in the first postnatal week. Furthermore, although femoral vascular cholinergic receptors are demonstrable at birth, there appears to be a delay in the maturation of functionally active vasodilator fibers.

Improvement in ischemic myocardial blood flow following a new calcium antagonist

1980 ◽  
Vol 239 (2) ◽  
pp. H163-H171 ◽  
Author(s):  
S. R. Jolly ◽  
G. J. Gross
Keyword(s):  
Blood Flow ◽  
Perfusion Pressure ◽  
Aortic Pressure ◽  
Contractile Force ◽  
Tissue Blood Flow ◽  
Coronary Pressure ◽  
Ischemic Tissue ◽  
High Doses ◽  
Mean Aortic Pressure ◽  
Aortic Perfusion

The effect of FR 7534, a new dihydropyridine CA2+ antagonist, nitroglycerin, and dipyridamole have been compared on coronary collateral function in pentobarbital-anesthetized open-chest dogs following acute ligation of the left anterior descending coronary artery. Measurements of tissue blood flow using radioactive microspheres were made 60 min postligation after low and high doses of each drug and at the higher dose with methoxamine added to to return mean aortic pressure. FR 7534 treatment increased subepicardial, subendocardial, and transmural tissue flow by 100% in the central ischemic zone when perfusion pressure was controlled by methoxamine. Nitroglycerin also increased ischemic tissue flow, but to a lesser degree, 18% transmurally. Dipyridamole produced no significant change. Tissue flow in normal myocardium was similarly increased by FR 7534 and dipyridamole but slightly reduced by nitroglycerin. FR 7534 and nitroglycerin also increased retrograde coronary pressure when aortic presure was maintained constant. FR 7534, but not nitroglycerin, increased ischemic contractile force. In this model, FR 7534 may produce greater effects than nitroglycerin in increasing blood supply to ischemic myocardium delivered by endogenous collaterals especially when aortic perfusion pressure was controlled.

Myocardial and systemic responses to arterial hypoxemia during cardiac tamponade

1989 ◽  
Vol 257 (3) ◽  
pp. H726-H733
Author(s):  
G. J. Crystal ◽  
M. R. Salem
Keyword(s):  
Cardiac Tamponade ◽  
Regional Blood Flow ◽  
Aortic Pressure ◽  
Arterial Hypoxemia ◽  
Pericardial Pressure ◽  
O2 Supply ◽  
Fick Equation ◽  
Arterial Po2 ◽  
Mean Aortic Pressure ◽  
Systemic Responses

Experiments were performed on 14 anesthetized, open-chest dogs to assess myocardial and systemic responses to cardiac tamponade alone (TAMP) and combined with arterial hypoxemia (HYP). Regional blood flow (RBF) was measured with radioactive microspheres and used to compute regional O2 supply. Myocardial oxygen and lactate extraction were determined. Myocardial oxygen consumption (MVO2) was calculated with Fick equation. An increase in pericardial pressure, sufficient to reduce mean aortic pressure (MAP) by 20%, caused proportional decreases in myocardial RBF and MVO2 but had no effect on endo-to-epi flow ratio or on myocardial lactate extraction. TAMP alone decreased RBF and O2 supply in kidney, splanchnic organs, skeletal muscle, and skin, but it had no effect in brain. HYP (arterial PO2, 35 +/- 2 mmHg) during TAMP restored MAP and caused transmurally uniform increases in myocardial RBF that were adequate to maintain MVO2 and lactate extraction. RBF increased sufficiently in brain to maintain regional O2 supply, whereas unchanged or inadequate increases in RBF in other tissues accentuated reductions in O2 supply. During combined TAMP and HYP, local vasodilator mechanisms were capable of maintaining adequate oxygen supply in myocardium and brain but not apparently in the nonvital tissues where these mechanisms were antagonized by reflex vasoconstriction.

Influence of acute hypertension on aortic valve competence

1975 ◽  
Vol 39 (6) ◽  
pp. 879-884 ◽  
Author(s):  
N. O. Fowler ◽  
J. C. Holmes ◽  
H. Spitz
Keyword(s):  
Aortic Valve ◽  
Aortic Insufficiency ◽  
Aortic Pressure ◽  
Acute Hypertension ◽  
Descending Aorta ◽  
Mean Pressure ◽  
Anesthetized Dogs ◽  
Aortic Incompetence ◽  
Indicator Dye ◽  
Mean Aortic Pressure

The effect of acutely induced hypertension on aortic valve competence was studied in anesthetized dogs. Aortic pressure was increased by infusion of methoxamine or mechanically; aortic valve competence was evaluated by aortogrphy and by indicator dye. The aortic valve was normally competent; aortic insufficiency appeared with increase of mean pressure by as little as 20–50 mmHg; 6 of 9 animals showed aortic incompetence when mean aortic pressure was elevated 45–70 mmHg, but the valve remained competent in 2 of 9 animals with mean pressure increments of 60–90 mmHg. The aortic root was appreciably less distensible than was the proximal descending aorta; this factor may limit the degree of aortic insufficiency in response to acute hypertension in the dog.

Renal effects of atrial natriuretic peptide in a marine elasmobranch

1990 ◽  
Vol 258 (5) ◽  
pp. R1201-R1206 ◽  
Author(s):  
S. Benyajati ◽  
S. D. Yokota
Keyword(s):  
Atrial Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Aortic Pressure ◽  
Renal Effects ◽  
Physiological Dose ◽  
Excretion Rates ◽  
Solute Excretion ◽  
Mammalian Peptide ◽  
Mean Aortic Pressure ◽  
Atrial Natriuretic

The effects of atrial natriuretic peptide on the renal function of the spiny dogfish (Squalus acanthias) in seawater were evaluated. A synthetic mammalian peptide, atriopeptin II (2 micrograms/kg), was injected intravascularly into unanesthetized, unrestrained fish prepared for renal clearance studies. The aortic pressure, glomerular filtration rate (GFR), urine flow rate (V), and urinary excretion of sodium, potassium, and total osmolytes were continuously monitored. Atriopeptin II significantly decreased mean aortic pressure (-12%), GFR (-40%), V (-66%), and the absolute excretion rates of sodium (-47%), potassium (-43%), and total osmolytes (-44%). However, the renal effects of atriopeptin II were temporally dissociated from the vasodepressor effect. Mean aortic pressure decreased quickly and returned to control values approximately 2 h after injection, whereas GFR did not decrease significantly until the third hour after injection. The decreases in renal water and solute excretion in response to atriopeptin could be accounted for by the decrease in GFR, since there were no significant changes in fractional water or solute excretion. Similar decreases in GFR were observed during constant infusions of a lower physiological dose of the peptide (80 pg.kg-1.min-1). The observed antidiuretic and antinatriuretic effect of synthetic atriopeptin in the dogfish contrasts with its putative role as a hormone mediating hypervolemic regulation.

Pulmonary microvascular response to prostacyclin (PGI2) infusion in unanesthetized sheep

1982 ◽  
Vol 52 (5) ◽  
pp. 1338-1342 ◽  
Author(s):  
R. Gunther ◽  
C. Zaiss ◽  
R. H. Demling
Keyword(s):  
Cardiac Output ◽  
Aortic Pressure ◽  
Base Line ◽  
Fluid Exchange ◽  
Protein Ratio ◽  
Microvascular Response ◽  
Pulmonary Arterial ◽  
Pulmonary Microcirculation ◽  
Rebound Increase ◽  
Mean Aortic Pressure

We studied the effect of prostacyclin (PGI2) infusion and cessation of infusion on the pulmonary microcirculation. We used lung lymph flow (QL) and the lymph to plasma protein ratio as sensitive indices of net fluid (QF) and protein flux (CP). After a 4-h base line period, we infused PGI2 (0.2 micrograms . kg(-1).min(-1) into eight unanesthetized sheep for 2 h. We monitored vascular pressures and lymph during infusion and for another 18 h after PGI2. During infusion, QL and cardiac output increased by 75 and 50%, respectively, over base line, whereas the lymph-to-plasma ratio (L/P) remained constant for both albumin and globulin. This resulted in a significant increase in both fluid and protein flux. Pulmonary vascular pressures remained unchanged, whereas mean aortic pressure decreased. The increase in QF and CP was felt to be due to an increase in the surface area of fluid exchange vessels rather than increased permeability. After infusion, cardiac output rapidly returned to base line, whereas mean QL remained increased by 70% over base line for 2–8 h. Mean L/P decreased from 0.65 to 0.53. Pulmonary arterial pressure and pulmonary vascular resistance increased. The increase in QL and decrease in L/P indicate a rebound increase in pulmonary microvascular pressure in the postperfusion period.

Vasodilator reserve in respiratory muscles during maximal exertion in ponies

1986 ◽  
Vol 60 (5) ◽  
pp. 1571-1577 ◽  
Author(s):  
M. Manohar
Keyword(s):  
Blood Flow ◽  
Maximal Exercise ◽  
Respiratory Muscles ◽  
Aortic Pressure ◽  
Whole Body ◽  
Adenosine Infusion ◽  
Base Line ◽  
Triceps Brachii ◽  
Vasodilator Reserve ◽  
Mean Aortic Pressure

Eight healthy adult grade ponies were studied at rest as well as during maximal exertion carried out with and without adenosine infusion (3 microM X kg-1 X min-1 into the pulmonary artery) on a treadmill to compare levels of blood flow in respiratory muscles with those in other vigorously working muscles and to ascertain whether there remained any unutilized vasodilator reserve in respiratory muscles of maximally exercising ponies. Radionuclide-labeled 15-micron-diam microspheres, injected into the left ventricle, were used to study tissue blood flows. During maximal exertion, there were increases above base-line values in heart rate (336%), mean aortic pressure (41%), cardiac output (722%), and arterial O2 content (56%). The whole-body O2 consumption was 123 +/- 11 ml X min-1 X kg-1, and the stride/respiratory frequency of the galloping ponies was 138 +/- 4/min. With adenosine infusion during maximal exertion, mean aortic pressure decreased (P less than 0.05), but none of the above variables was different from maximal exercise alone. During maximal exertion, blood flow in the adrenal glands, myocardium, respiratory, and limb muscles increased, whereas that in the kidneys decreased and the cerebral perfusion remained unaltered. With adenosine infusion during maximal exercise, renal vasoconstriction intensified, whereas adrenal and coronary beds exhibited further vasodilatation. During maximal exertion, blood flow in the equine diaphragm (265 +/- 36 ml X min-1 X 100 g-1) was not different from that in the gluteus medius (253 +/- 36) and biceps femoris (233 +/- 29); both are principal muscles of propulsion in the equine subjects) or the triceps brachii (227 +/- 26) muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

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