Fontan Hemodynamics

Right atrial-pulmonary artery connection places the pulmonary circulation in series with the systemic circulation rather than the single ventricular "parallel" circulatory arrangement that usually is present prior to repair. The accompanying central cardiac shunt and volume overload physiology are eliminated. Favorable changes in ventricular dimension, ventricular wall stress, cardiovascular efficiency, relative systemic perfusion, and arterial oxygen saturation should result. The ongoing myocardial injury associated with the single-ventricle volume overload is presumably arrested and repair is initiated to a variable degree. Some candidates for right atrial-pulmonary artery connection may not benefit from repair because of irreversible ventricular injury. More accurate indices of systolic and diastolic ventricular function should be applied to this difficult group of borderline patients to further define potential for myocardial recovery and, therefore, candidacy for Fontan repair.     

高尿酸血症与高血压进展

尿酸是体内嘌呤代谢的终产物,任何原因造成尿酸生成过多或排泄减少都可引起高尿酸血症.目前认为基础血尿酸水平是高血压发病的最强的独立预报因子,它在高血压的发生发展及预后的过程中起着重要的作用.本文就近年来高尿酸血症与高血压关系进展作一综述.     

Hemodynamics of sequential grafts

Sequential femoropopliteal-tibial grafts have been advocated as a promising treatment for use in patients with severe ischemia of the distal lower extremity. Proponents hypothesize better patency rates due to documented increases in proximal graft flow with the sequential technique. We hypothesized that the effect of the sequential graft was to create competitive collateral flow and that distal graft flow would not be increased with the addition of a sequential anastomosis. Seven adult dogs with chronic occlusions were studied with angiography and underwent sequential iliofemoral bypass grafting. Proximal and distal flows were measured with and without the sequential anastomosis open to flow. Proximal graft flows increased significantly whereas distal flows decreased significantly in all dogs with an open sequential anastomosis. The study suggests that there may be limitations to the use of sequential bypass grafts.     

Hemodynamics of arterial stenosis

In order to derive a better understanding of the effect of varying degrees of stenosis on arterial pulsatile waveforms, an in vitro model was constructed and in vivo studies were done in dogs to observe and record the changes in the pulsatile and steady arterial blood flow components. Blood flow measurements were made using the electromagnetic blood flowmeter proximal and distal to the stenosis. The data show that as the degree of stenosis increases, the decreases in the pulsatile components of flow and distal pressure occur earlier and to a much greater degree than changes in mean flow.

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Résumé Pour mieux comprendre les effets de sténoses d'importance variable sur la forme du pouls, nous avons construit un modèle in vitro et l'avons complété par des observations in vivo chez le chien. Nous avons observé et enregistré les modifications des composantes moyenne et pulsatile du flux sanguin. Les mesures ont été faites avec un débitmètre électromagnétique en amont et en aval de la sténose. Lorsque les diamètres artériels diminuent, les composantes pulsatiles du flux et de la pression en aval diminuent plus vite que le débit sanguin moyen.

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Presented at the XXVIIth Congress of the Société Internationale de Chirurgie, Kyoto, Japan, September 3–8, 1977.     

Hemodynamics of penile erection

In the flaccid state, the smooth muscles of the cavernous arterioles and trabeculae are contracted, and minimal blood flow enters the sinusoids. Relaxation of these smooth muscles incites arterial dilation, venous compression, and sinusoidal relaxation and results in penile erection.     

Hereditary hyperuricemia and renal disease

Hyperuricemia and gout have long been known to run in families. As well as an apparently multifactorial genetic component to classic gout itself, 2 rather unusual sex-linked single-gene disorders of purine biosynthesis or recycling have been defined: deficiency of the enzyme hypoxanthine-guaninephosphoribosyl transferase (HPRT), and overactivity of PPriboseP synthase. Both result in overproduction of urate, hyperuricemia, and secondary overexcretion that may lead to acute or chronic renal damage. Familial juvenile hyperuricemic nephropathy (FJHN) and autosomal-dominant medullary cystic kidney disease (ADMCKD) are more common but less well-defined hyperuricemic conditions resulting from a decrease in the fractional excretion of filtered urate, with normal urate production. Although having features in common, ADMCKD is distinguished in particular by the presence of medullary cysts. One major group of both disorders is associated with mutations in the gene for uromodulin, but this accounts for only about one third of cases, and genetic heterogeneity is present. Whether the genes involved in these latter disorders contribute to the polygenic hyperuricemia and urate underexcretion of classic gout remains unexplored.     

Hemodynamics of Distal Revascularization-Interval Ligation

Distal revascularization-interval ligation (DRIL) empirically corrects steal after arteriovenous fistula (AVF) creation in most cases, but because there is no topologic alteration in anatomy, it is unclear as to why it is effective. To explore this issue, nine symptomatic patients underwent intravascular pressure and flow measurements before and after DRIL following upper arm autologous AVFs. Mean pre-DRIL systolic pressure (mmHg; mean ± SD) in the proximal brachial artery (PROX) was 102 ± 17, while that at the AV anastomosis (AV ANAST) was 47 ± 38 (p < 0.0006). Flow (mL/min) distal to AV ANAST was retrograde with the fistula open (–21 ± 64) but became antegrade (58 ± 29; p < 0.03) with occlusion of the fistula. Following DRIL, pressures at both PROX and AV ANAST sites did not change (104 ± 24 and 51 ± 43, respectively). However, pressure at the point at which the blood flow split to supply the hand or the fistula, now PROX, increased from 47 ± 38 (pre-DRIL AV ANAST) to 104 ± 24 (p < 0.0001). Pressure in the brachial artery distal to the ligature increased to 104 ± 27 (p < 0.0001), flow at this point (to the hand) became antegrade (51 ± 39; p < 0.03), and occlusion of the fistula did not significantly change pressure at this site. We hypothesize that improvement in hand perfusion following DRIL is due to a higher pressure at the point at which the blood flow splits to supply both hand and fistula (pre-DRIL: AV ANAST; post-DRIL: PROX), allowing antegrade flow down the new bypass to the lower pressure forearm. This increased pressure must be due to the increased resistance of the fistula created by interposing the arterial segment between the original AV ANAST and new PROX ANAST. As such, DRIL is schematically equivalent to banding, but resistance is increased in a fashion that is physiologically and empirically acceptable.Presented at the Twenty-ninth Annual Meeting of the Peripheral Vascular Surgery Society, Anaheim, CA, June 4-5, 2004.     

Hemodynamics in donor plasmapheresis

Several studies have demonstrated that preoperative withdrawal and storage of autologous plasma as fresh frozen plasma is effective in blood conservation. For that purpose patients with elective surgery (orthopaedic surgery, open heart surgery, neurosurgery and others) have to undergo donor plasmapheresis without staying in the hospital. Depending upon the need the procedure can be performed several times preoperatively, taking about 900 ml in a normal weighting subject at once. The collection of autologous plasma should be finished at least 14 days before surgery. In order to investigate the haemodynamic effects of donor plasmapheresis 30 patients scheduled for coronary bypass surgery were devided into two groups. 15 patients underwent plasmapheresis (10 ml plasma/kgbw) by one-needle-technique using a Haemonetics seperator (PCS) after premedication but before onset of anaesthesia. Blood withdrawal was performed with 0.5 ml/kgbw x min. Another 15 patients, serving as control had no plasma withdrawal and were measured at identical times as the other group. Both groups had an identical fluid replacement with 500 ml Ringer's solution during the investigation period. Plasma withdrawn was not substituted by colloidal solution (simulating the situation when plasmapheresis is performed at the outpatient). Haemodynamic measurements (both groups) included heart rate, arterial blood pressure, right- and left-atrial pressure, systemic- and pulmonary-vascular resistance and cardiac output. There were no relevant effects of plasmapheresis on haemodynamic function during and after the investigation period in that patients: neither heart rate, blood pressure or vascular resistance changed significantly nor did pre- and afterload or cardiac index. No differences to the group without plasmapheresis could be observed.(ABSTRACT TRUNCATED AT 250 WORDS)