Diminished release of atrial natriuretic factor in calves with a total artificial heart

Venous hypertension after total artificial heart (TAH) replacement, a common problem in humans as well as experimental animals, is thought to be related to reduced release of atrial natriuretic factor (ANF) due to atrial damage. To verify this hypothesis, we stimulated the release of ANF in 6 calves before (-7 days) and after TAH replacement (+25, +50, +80, and +100 days) by the rapid (+ = 10 min) infusion of 2 L of Ringer's solution. In normal calves (-7 days) this procedure induced a rise in plasma concentration of ANF from 18.5 +/- 12 to 31.6 +/- 12 pmol/L (p < 0.05). After TAH the ANF release continuously decreased (analysis of variance, p < 0.02). Thus, ANF increased by 9.8 +/- 9.3, 6.8 +/- 17.5, 0.4 +/- 5.2, and 0.5 +/- 3.2 pmol/L at days 25, 50, 80, and 100, respectively. The central venous pressure increased by 3.4 +/- 1.5 mm Hg (before TAH) and by 6 +/- 2.9 mm Hg (after TAH) during this procedure. A decrease in plasma concentrations of aldosterone, most likely due to extracellular volume expansion and a decrease in total protein plasma concentrations and in hematocrit due to the dilution of blood, was seen in each experiment. Necropsy demonstrated massive atrial dilatation and myocardial dystrophy with atrial fibrosis. ANF granules were present to a small extent in every calf. We conclude that rapid intravenous infusion is an adequate stimulus to release ANF in normal calves. After TAH implantation the release of ANF by high venous pressure declines although ANF granules are still present in the damaged atrial stumps. Therefore, the loss of stimulated ANF could contribute to the observed increase in venous pressure in TAH calves although other pathophysiologic mechanisms cannot be excluded.     

Automatic atrial tachycardia in an infant following general anesthesia

Automatic atrial tachycardia (AAT) is a rare supraventricular tachyarrhythmia (<10% of all supraventricular tachycardias), which can present in infants or young children. There are no published reports of AAT occurring in an infant or child following noncardiac surgery and general anesthesia. This report describes the management of a previously healthy 5-month-old infant, who developed AAT in the postanesthesia care unit following an uneventful circumcision under general anesthesia.     

High-Detailed evaluation of the right atrial anatomy by three-dimensional rotational angiography during ablation procedures for atrioventricular nodal reentrant tachycardia and atrial flutter

Abstract

Aim. 3D Rotational angiography (3DRA) allows for detailed reconstruction of atrial anatomy and is often used to facilitate pulmonary vein isolation. This study aimed to reappraise the anatomy of the right atrium (RA) using 3DRA, specifically looking at Koch’s triangle and the cavotricuspid isthmus (CTI) in atrio-ventricular reentrant tachycardia (AVNRT) and atrial flutter (AFl) ablation. Methods and results. 3DRA was performed in 97 patients: AVNRT =?51 and AFl =?46. Dimensions of Koch’s triangle and CTI were highly variable between individuals but were not different in both ablation groups. RA volume was significantly larger in AFl patients (p = .004) while indexed RA volume to the body surface area (RAVI) was lightly different (p = .024). In univariate Cox analysis, age (p = .003), RAVI (p < .001) and previous ablation of AFl (p = .003) were predictors of AF occurrence . In multivariate Cox analysis, RAVI was the only independent predictor of AF occurrence. RAVI >80?ml/m² was a strong predictor for AF during follow-up. Conclusion. 3DRA allows for detailed per-procedural evaluation of RA anatomy and revealed a great variability in Koch’s triangle and CTI dimensions and morphology. RA enlargement as measured by RAVI was an independent predictor for AF occurrence during follow-up.     

The effect of positive end-expiratory pressure ventilation on atrial filling

As a measure of atrial filling, left and right auricular diameter and free wall segment length were recorded by sonomicrometry during incremental positive end-expiratory pressure (PEEP) in eight acutely instrumented closed chest dogs. The effect of PEEP was assessed with the pericardium open (n = 6) and closed (n = 8). On both occasions, PEEP decreased left auricular diameter (P less than 0.05). PEEP also caused a reduction in right auricular diameter with the pericardium open (P less than 0.05), while the variable was unchanged with the pericardium closed. PEEP did not cause any changes in either left or right free wall segment lengths. Both left and right auricular pressure-diameter relationships were progressively shifted leftwards with incremental PEEP. These observations suggest that PEEP may reduce left ventricular output not only by interfering with passive ventricular filling, but also by reducing atrial dimensions.     

人工二尖瓣舒张期最大跨瓣压与左心房压力的相关性

目的 分析二尖瓣置换或修复术患者舒张期最大跨瓣压与左心房压力(LAP)的相关性.方法 选择行心肺转流(CPB)下二尖瓣置换或修复手术的瓣膜病患者20例,男9例,女11例,年龄18～80岁,术中行经食管超声心动图(TEE)监测.于心脏复跳后CPB停机前、左心房引流管拔除前,分别采用左心房引流管测量LAP,TEE测量人工二...     

The relationship between change in blood pressure, blood pressure and time

Physiological homeostatic mechanisms and interventions by anaesthetists attempt to moderate excessive change in many biological variables during anaesthesia. These mechanisms may have fast or slow response times. This study describes how mean arterial blood pressure changes with time and how the change is dependent upon the pre-existing blood pressure. The results demonstrate the 'regression towards the mean' concept; low arterial blood pressures increase and high pressures decrease. The data are the result of all interactions and have been used to produce an 'envelope' into which 80% of all changes fall. Alarm systems using this envelope could warn of excessive changes that occur within short time intervals.     

Plasma concentrations of atrial natriuretic factor during positive end-expiratory pressure ventilation in dogs with normal or impaired left ventricular function

The influence of positive end-expiratory pressure (PEEP) ventilation on plasma concentrations of atrial natriuretic factor (ANF) was studied in dogs anesthetized with sodium pentobarbital during normal cardiac function and during acutely impaired left ventricular function. Left ventricular impairment was induced by injecting repeated doses of polystyrene microspheres with a diameter of 50 microns into the main left coronary artery, causing a severe depression of left ventricular performance. This was accompanied by doubling of ANF concentrations measured in blood sampled from aorta. Application of PEEP (10 cmH2O (0.98 kPa] reduced plasma ANF in dogs both with normal and impaired left ventricular function. The decrease was significantly greater during left ventricular impairment compared to control, 31 and 19%, respectively. A positive correlation was observed between plasma ANF and transmural left ventricular end-diastolic pressure when all data were pooled, but not between ANF and transmural right atrial pressure. This implies that transmural left ventricular end-diastolic and hence transmural left atrial pressure probably is the principal determinant of acute ANF release in this model. Reduced plasma ANF in response to PEEP even during acute left ventricular impairment when ANF release was augmented, was probably due to diminished atrial distension during PEEP ventilation.     

Plasma levels of atrial natriuretic factor and catecholamines in endotoxin shock in dogs

Changes in arterial plasma levels of atrial natriuretic factor and catecholamine release were studied in 11 beagle dogs during pentobarbital anesthesia. Seven dogs were injected intravenously with Escherichia coli endotoxin, 0.5 mg/kg over 15 min. Four control dogs received only saline solution. The endotoxin injection resulted in cardiac depression,, hemoconcentration, acidosis and renal hypoperfusion. The central venous pressure remained relatively unchanged in both groups during the 2-hour study. The concentrations of epinephrine, norepinephrine and the norepinephrine metabolite 3,4-dihydroxyphenylglycol increased in arterial plasma during the acute hypodynamic endotoxin shock. In the control dogs the levels of these hormones remained very low and constant. Increased circulating levels of atrial natriuretic factor were observed in endotoxin shock with renal hypoperfusion, unchanged central venous pressure and no concomitant tachycardia.     

Plasma atrial natriuretic polypeptide and polyuria during paroxysmal tachycardia in Wolff-Parkinson-White syndrome patients

The human atrial natriuretic polypeptide (hANP) concentration in plasma was measured during paroxysmal supraventricular tachycardia provoked in 2 patients with Wolff-Parkinson-White syndrome. A 10- to 20-fold increase in plasma hANP concentration was observed during the tachycardia: from 12 to 291 pg/ml in 1 case and from 14 to 174 pg/ml in the other. Although polyuria was associated with the tachycardia, urinary sodium excretion as well as urinary osmolality were decreased. The urinary arginine vasopressin was appreciably decreased during the tachycardia. These results suggest that hANP released by paroxysmal tachycardia might not act as a natriuretic factor in this range of plasma concentration. Polyuria during paroxysmal tachycardia was attributed mainly to the inhibition of arginine vasopressin release.     

The relationship between transmurality of ischemic scars and the heart rate of ventricular tachycardia

Abstract

Aims. The relationship between the heart rate of ventricular tachycardia (VT) and the transmurality of ischemic scars was assessed by a new semiautomatic coordinate-based analysis of late gadolinium-enhanced cardiac magnetic resonance (LGE-CMR) images. Methods and results. Twenty patients assessed by LGE-CMR before implantation of implantable cardioverter defibrillator (ICD) with verified VT during the first year following ICD implantation were included. Scar was defined by pixels with a signal intensity ≥ 50% of maximum signal intensity. All pixels were assigned a coordinate position between endo- and epicardium (λ) and the angle of the heart axis (φ). Based upon the λ and φ values, multiple scar features were computed for all scarred areas. These features were correlated to VT heart rate across the complete range of transmurality. The strongest correlation with univariate regression was found between VT heart rate and the sum of transmurality when the maximum transmurality of these features was ≥ 90% (R-square = 0.47). In multiple regressions analysis, the strongest relationship with VT heart rate was found with a maximum transmurality ≥ 90% and by a combination of scar size, transmurality, and endocardial extent of infarction (R-square = 0.64). Conclusion. Transmurality is the strongest predictor of VT heart rate both in univariate and multivariate models. The strongest relationships were found at a transmurality level > 90%.     

Prevention of acute cyclosporin nephrotoxicity by verapamil and atrial natriuretic factor in the rat

Nephrotexicity is the most common and important side-effectof cyclosporin (CsA) therapy. CsA alters renal haemodynamicswith a reduction in renal blood flow (RBF) and glomerular filtrationrate (GFR) and a significant increase in renal vascular resistances(RVR). The present experimental study investigates whether verapamilor atrial natriuretic factor (ANF) are able to prevent the nephrotoxicityof CsA. All studies were conducted in an in-situ autoperfused rat kidneymodel which allows continuous measurement of renal blood flowwithout dissection of the renal artery. CsA as a 40 mg/kg bolus dose significantly decreased RBF (from2.15±0.1 and 2.19±0.1 before CsA, to 1.29±0.16ml/min/100 g BW, 60 mm after CsA administration) (P<0.05),and GFR (from 0.14±0.1 and 0.13±0.01 before CsA,to 0.08±0.01 ml/min/100 g BW, 60 min after CsA administration)(P<0.05). CsA significantly increased RVR (from 9.5±0.73and 9.8±0.78 before CsA, to 16.7±2.9 mmHgxmin/ml60 min after CsA administration) (P<0.05). Verapamil pretreatment(as continuous intrarenal infusion at the rate of 1.25 µg/kg/min)attenuated the fall in GFR (from 0.16±0.01 and 0.19±0.03ml/min/100 g before CsA to 0.20±0.05 ml/min/100 g BW,60 mm after CsA administration) (NS) and in RBF (from 2.42±0.2and 2.6±0.22 ml/min/100 g before CsA to 1.79±0.17ml/min/100 g BW, 60 min after CsA administration (P<0.05).Pretreatment with ANF (as continuous intrarenal infusion atthe rate of 2.5 µg/kg/min) protected GFR (from 0.11±0.02and 0.18±0.03 ml/min/100 g before CsA, to 0.11±0.03ml/min/100 g BW, 60 min after CsA administration) (NS) and RVR(from 9.53±0.6 and 8.95±0.74 mmHgxmin/ml beforeCsA to 11.93±1.19 minHgxmin/ml, 60 min after CsA administration)(NS)and attenuated the fall in RBF (from 2.17±0.11 and 2.2±0.14ml/min/100g before CsA to 1.56±0.25 ml/min/100 g BW 60mm after CsA administiation)(P<0.05) when compared with initialvalues. These studies suggest that verapamil and ANF can prevent CsA-inducedrenal toxicity. Further studies should evaluate their usefulnessin clinical practice.     

Maternal and fetal plasma atrial natriuretic peptide concentrations during elective caesarean section

Atrial natriuretic peptide (ANP) is stored in the atrial cardiocyte and is capable of exerting potent, selective, and transient effects on fluid and electrolyte balance and on blood pressure. Because fluid shifts and hemodynamic adjustments occur during parturition, ANP might play a homeostatic role in the parturient and fetoplacental unit. We measured maternal and fetal plasma ANP concentrations in 19 parturients during elective caesarean section. Plasma ANP levels were also measured in seven nonpregnant women of the same age group. The baseline ANP concentration in parturients was significantly higher (29.77 +/- 6.06 pg/ml vs 7.37 +/- 2.1 pg/ml; mean +/- s.e.mean) than in their nonpregnant counterparts. The umbilical artery (UA) ANP concentration was significantly higher than the umbilical vein concentration (91.91 +/- 14.91 pg/ml vs. 40.04 +/- 9.71 pg/ml). Factors under the anaesthesiologist's control may influence maternal and fetal plasma ANP levels. There was a significant correlation between the volume of maternal Ringer's lactate infusion received and maternal ANP concentration. A significant correlation was seen between the total dose of ephedrine administered acutely prior to delivery and the UA ANP concentration. These data suggest that: 1) increased blood volume during pregnancy is associated with increased maternal plasma ANP levels, and 2) the fetus can produce its own ANP, and is thereby capable of responding to ANP stimulating factors.     

Electroanatomic mapping of transseptal conduction during coronary sinus pacing in patients with paroxysmal atrial fibrillation

Objective—To delineate the electrophysiological properties of transseptal conduction from the left to the right atrium in patients with paroxysmal atrial fibrillation (AF).

Design and results—Right atrial mapping using the electroanatomic mapping technique was performed at 111?±?16 sites in 16 patients with paroxysmal AF during pacing from distal coronary sinus (CS). A single transseptal breakthrough near the CS ostium was observed in all patients. The activation time from the pacing site to the earliest septal activation site was 47?±?13?ms. The total septal activation time (68?± 16?ms) was markedly longer but the total right atrial activation time (118?±?17?ms) was similar to that in patients without AF in a previous observation.

Conclusion—During distal CS pacing, a preferential site of transseptal conduction near the CS ostium was demonstrated in patients with paroxysmal AF. This has clinical implications when surgical dissection or catheter ablation is considered to eliminate interatrial connection in patients with AF.     

The relationship between functional class,pulmonary artery pressure and size in left atrial myxoma

To examine the correlation between the size of left atrial myxoma, the degree of pulmonary hypertension and the patient's New York Heart Association (NYHA) functional class, the records of 29 surgically treated patients with left atrial myxoma were reviewed. Of 29 patients, 23 were catheterized before surgery. As the preoperative NYHA functional class advanced, the preoperative mean pulmonary artery pressure (mmHg) was seen to increase. Moreover, the weight of the excised myxoma also correlated well with the preoperative pulmonary artery pressure value. In five patients inserted with a Swan-Ganz catheter, the mean pulmonary artery pressure decreased immediately after tumour excision. Postoperatively, the average NYHA class of the 29 patients significantly improved. These results confirmed the positive correlation between the size of the tumour, the pulmonary artery pressure, and NYHA class in patients with left atrial myxoma.     

Acute and long-term changes in plasma levels of atrial natriuretic factor in patients with renal replacement therapy

Abstract. In 14 patients on hemodialysis who received kidney grafts from living related donors, plasma levels of immunoreactive atrial natriuretic factor (Ir-ANF) were determined in a sequence covering the last hemodialysis treatment, the day of transplantation, and a follow-up period of 6–12 months. The geometric mean value before dialysis was 196 pg/ml, the range 32–634. Weight loss during dialysis was 1. 5 1. 1 kg (mean SD), but only a nonsignificant reduction in Ir-ANF levels occurred. On the day of transplantation, plasma Ir-ANF levels increased from 143 pg/ml before to 391 post-transplantation ( P = 0. 02, n = 12), probably in response to deliberate volume expansion. Post-transplant Ir-ANF levels correlated significantly to diuresis during the first 24 h, which ranged from 3. 7 to 17. 81 (mean 6. 6; r = 0. 65, P = 0. 02). On day 2, mean 24 h diuresis decreased to 3. 3 1. 41. Most patients had reached their true dry weight by day 5, but Ir-ANF levels remained high, the geometric mean being 180 pg/ml. During further follow-up and preserved graft function (GFR range 34–88 ml/min per 1. 73 m² body surface area), Ir-ANF levels declined to a geometric mean of 63 pg/ml by 2–6 months and to 36 at 12 months post-transplant. We conclude that plasma Ir-ANF levels are chronically elevated in patients with chronic renal failure but may be further stimulated by acute overhydration. Transplanted kidneys initially respond to the increased levels but adapt within a day. Even with good graft function, normalization of plasma Ir-ANF requires several weeks or months.     

Acute and long-term changes in plasma levels of atrial natriuretic factor in patients with renal replacement therapy

In 14 patients on hemodialysis who received kidney grafts from living related donors, plasma levels of immunoreactive atrial natriuretic factor (Ir-ANF) were determined in a sequence covering the last hemodialysis treatment, the day of transplantation, and a follow-up period of 6–12 months. The geometric mean value before dialysis was 196 pg/ml, the range 32–634. Weight loss during dialysis was 1.5±1.1 kg (mean±SD), but only a nonsignificant reduction in Ir-ANF levels occurred. On the day of transplantation, plasma Ir-ANF levels increased from 143 pg/ml before to 391 post-transplantation (P=0.02, n=12), probably in response to deliberate volume expansion. Post-transplant Ir-ANF levels correlated significantly to diuresis during the first 24 h, which ranged from 3.7 to 17.81 (mean 6.6; r=0.65, P=0.02). On day 2, mean 24 h diuresis decreased to 3.3±1.41. Most patients had reached their true dry weight by day 5, but Ir-ANF levels remained high, the geometric mean being 180 pg/ml. During further follow-up and preserved graft function (GFR range 34–88 ml/min per 1.73 m² body surface area), Ir-ANF levels declined to a geometric mean of 63 pg/ml by 2–6 months and to 36 at 12 months post-transplant. We conclude that plasma Ir-ANF levels are chronically elevated in patients with chronic renal failure but may be further stimulated by acute overhydration. Transplanted kidneys initially respond to the increased levels but adapt within a day. Even with good graft function, normalization of plasma Ir-ANF requires several weeks or months.     

Relationship between blood pressure during haemodialysis and ambulatory blood pressure in between dialyses

BACKGROUND.: Ambulatory blood pressure measurements in haemodialysis patientsare relevant in view of the high cardiovascular morbidity andmortality in chronic haemodialysis patients. METHODS.: Twelve normotensive patients were studied from the beginningof one dialysis until the end of the next (mean 64 h, SD 19h) using a Spacelabs oscillometric blood-pressure recorder. RESULTS.: A circadian blood pressure rhythm was present in six of the12 patients. In seven patients the lowest pressure recorded(including the dialysis sessions) occurred 5–6 h afterdialysis (late post-dialysis dip). Blood pressure did not increasesharply in the hours before dialysis although it increased slightlyin the interdialytic interval as a whole, at a mean rate of5.6 mmHg per 24 h (SD 4.1, P<0.001). We could not find ablood pressure measurement during dialysis (or combination ofmeasurements) which reliably reflects interdialytic blood pressure:the 95% confidence intervals were 25 mmHg or higher. CONCLUSION.: Ambulatory blood pressure measurements are needed for adequatemonitoring of the control of blood pressure in haemodialysispatients.     

Effects of continuous negative extrathoracic pressure ventilation on left ventricular dimensions and hemodynamics in dogs

It has been reported that continuous negative extrathoracic pressure ventilation (CNETPV) depresses cardiac output less than continuous positive pressure ventilation (CPPV) does, and this difference may be related to the different effects of two ventilatory modes on preload. We performed simultaneous measurements of hemodynamics and left ventricular short axis dimensions by transesophageal echocardiography (TEE) to evaluate left ventricular preload and function during CNETPV and CPPV in normal dogs.Hemodynamic measurements and simultaneous TEE recording were performed at 5 successive periods; 1) the first control period of intermittent positive pressure ventilation (IPPV1), 2) CNETPV with negative end-expiratory pressure (NEEP) of –10cmH₂O (CNET10), 3) CNETPV with NEEP of –15cmH₂O (CNET15), 4) the second control period of IPPV (IPPV2), and 5) CPPV with PEEP of 15cmH₂O (CPPV15). Left ventricular end-systolic and end-diastolic dimension (LVESD and LVEDD), ejection fraction (EF) and fractional shortening (FS) were measured from TEE recordings.Both CNET10 and CNET15 induced no significant changes in hemodynamics and left ventricular dimensions, compared with those during IPPV1. However, CPPV15 reduced cardiac output and stroke volume (SV) and increased heart rate significantly, compared with IPPV2. CPPV15 significantly decreased LVEDD compared with IPPV2. Neither EF nor FS showed any significant change throughout the experiment.These results indicate that CNETPV preserved cardiac output because it maintained the preload and the left ventricular function.(Andoh T, Doi H, Kudoh I, et al.: Effects of continuous negative extrathoracic pressure ventilation on left ventricular dimensions and hemodynamics in dogs. J Anesth 7: 308–315, 1993)     

经皮椎体成形术注入压力与心肺并发症的关系

目的　探讨经皮穿刺椎体成形术中注入压力与心肺并发症之间的关系。方法　筛选 8只成年杂交山羊 ,随机分为两组 ,每组均在C臂X线机引导下分别行L2 、L3 、L43个椎体的椎弓根穿刺 ,A组单侧穿刺保持较大的压力 (5 7 8kPa± 3 3kPa)注入 ,B组两侧椎弓根穿刺形成减压孔以相对较低的压力 (48 5kPa± 2 6kPa)注入 ,两组均同时测量推注时的压力、注入前后的心率、平均颈动脉压和血气分析 ,处死后行肺组织切片染色。结果　A组对心率、平均颈动脉压、血气分析和肺内脂肪滴的影响要大于B组 (P <0 0 5 )。结论　经皮椎体成形术推注压力越大 ,越易引起心肺并发症。