Plasma atrial natriuretic peptide (ANP) concentration and fluid balance during rapid intravenous saline infusions in camels

Human muscle samples were obtained with the percutaneous biopsy technique. The samples were membrane-hyperpermeabilized (skinned) using a chemical or freeze-drying technique. Short single fibre segments were dissected from the sample, transferred to an experimental chamber, connected to a force transducer and manipulator, and exposed to temperature-controlled solutions. The force generating-capacity, the sensitivity of the contractile apparatus to calcium and the caffeine threshold for calcium release from the sarcoplasmic reticulum could be studied in the short muscle fibre segments obtained from man with the percutaneous muscle biopsy technique. The average length of the fibre segments between the connectors was 0.44±0.21 mm. Thus, detailed studies of the contractile machinery can be made on human skinned muscle fibres with only minimal discomfort to the patient or subject during biopsy, which should be useful in studies of neuromuscular disease, muscle plasticity or in applied physiology.     

Electrocardiographic and Clinical Predictors of Torsades de Pointes Induced by Almokalant Infusion in Patients with Chronic Atrial Fibrillation or Flutter: A Prospective Study

The aim of this study was to identify predictors of torsades de pointes (TdP) in patients with atrial fibrillation (AF) or flutter exposed to the Class III antiarrhythmic drug almokalant. TdP can be caused by drugs that prolong myocardial repolarization. One hundred patients received almokalant infusion during AF (infusion 1) and 62 of the patients during sinus rhythm (SR) on the following day (infusion 2). Thirty-two patients converted to SR. Six patients developed TdP. During AF, T wave alternans was more common prior to infusion (baseline) in patients developing TdP (50% vs 4%, P < 0.01). After 30 minutes of infusion 1, the TdP patients exhibited a longer QT interval (493 ± 114 vs 443 ± 54 ms [mean ± SD], P < 0.01), a larger precordial QT dispersion (50 ± 74 vs 27 ± 26 ms, P < 0.05), and a lower T wave amplitude (0.12 ± 0.22 vs 0.24 ± 0.16 mV. P < 0.01). After 30 minutes of infusion 2, they exhibited a longer QT interval (672 ± 26 vs 489 ± 74 ms, P < 0.001), a larger QT dispersion in precordial (82 ± 7 vs 54 ± 52 ms, P < 0.01) and extremity leads (163 ± 0 vs 40 ± 34 ms, P < 0.001), and T wave alternans was more common (100% vs 0%, P < 0.001). Risk factors for development of TdP were at baseline: female gender, ventricular extrasystoles, and treatment with diuretics; and, after 30 minutes of infusion: sequential bilateral bundle branch block, ventricular extrasystoles in bigeminy, and a biphasic T wave. Patients developing TdP exhibited early during almokalant infusion a pronounced QT prolongation, increased QT dispersion, and marked morphological T wave changes.     

心电图短P-R间期观测研究

目的：探讨和鉴别心电图短Ｐ－Ｒ间期的产生原因，为临床诊断、治疗提供依据。方法：检测１１５例受检者的常规导联心电图（ＲＬＥＣＧ）、头胸导联心电图（ＨＣＥＣＧ）、食管导联心电图（ＥＬＥＣＧ），对其中５５例临床可疑心律失常和ＲＬＥＣＧ示短Ｐ－Ｒ间期者行食管心房调搏电生理检查。结果：①Ｐ波出现率和振幅均值比较ＥＬＥＣＧ＞ＨＣＥＣＧ＞ＲＬＥＣＧ（Ｐ＜０．０１），出现率分别为１００％、９５％、９１％。②ＨＣＥＣＧＰ－Ｒ段均值（Ｐ＜０．０１）及变异系数＜ＲＬＥＣＧ。③ＲＬＥＣＧ波幅低、图形多变是产生心电图短Ｐ－Ｒ间期的主要原因。结论：作为无创伤性检查方法，ＨＣＥＣＧ和ＥＬＥＣＧ可以对短Ｐ－Ｒ间期者进行初步筛选，而经食管心房调搏能检测ＥＣＧ短Ｐ－Ｒ间期的电生理特性，对鉴别诊断有肯定价值。     

Relation Between Cycle Length, Volume, and Pressure in Type I Atrial Flutter

Assuming that type I atrial flutter is a macroreentrant circuit, its cycle length should vary with the atrial dimensions. In order to test this hypothesis, flutter cycle length was measured while inducing atrial volume and pressure changes by postural and pharmacological means in seven patients undergoing a therapeutic programmed stimulation for type 1 atrial flutter conversion. Right atrial volume was estimated from B-mode echocardiography data. Basal values were compared with those obtained during inspiration, expiration, Valsalva maneuver, negative tilt (head down), and positive tilt (head up) with 0.8–1.6 mg p.o. nitroglycerin. The right atrial size increased slightly from 17.8 to 18.3 cm² (P = 0.04) during the pressure load induced by negative tilt (+ 3 mmHg), with a corresponding lengthening of the flutter cycle length from 228 to 233 msec (P = 0.02). Similarly, pressure unloading of -2 mmHg by positive tilting and nitrates was accompanied by a decrease in right atrial size to 16.6 cm² (P = 0.04), with a corresponding decrease in cycle length from 228 to 219 msec (P = 0.03). Respiratory maneuver yielded similar results with an inspiratory cycle lengthening, expiratory shortening, and further shortening during Valsalva maneuver. These experiments demonstrate a direct relation between cycle length and atrial volume in human type I atrial flutter. They underline the importance of the right heart preload and atrial size for the electrophysiological characteristics of type I atrial flutter. Beside its fundamental interest, this finding is important for the understanding of the mechanism of maintenance and therapeutic responses of this common arrhythmia.     

POTASSIUM ACCELERATES URINARY SODIUM EXCRETION DURING SALT LOADING WITHOUT STIMULATING ATRIAL NATRIURETIC POLYPEPTIDE SECRETION

1. Effects of potassium (K) supplementation (100 mEq/day) on urinary sodium (Na) excretion and on the secretion of atrial natriuretic polypeptide (ANP) during salt loading (350 mEq/day) were studied in 12 healthy salt-resistant normotensives under strictly controlled metabolic ward conditions. 2. Urinary volume and Na excretion on the first day of the high salt period (HSP) were significantly greater in the K-supplemented group (KG) than in the control group (CG). 3. There was a significant gain in bodyweight after salt loading in both groups, with a significantly greater gain in CG on the second day of HSP. Haematocrit decreased significantly during salt loading in both groups, the degree of which was significantly greater in CG. 4. Plasma norepinephrine decreased significantly during salt loading in both groups, the degree of which was significantly less in KG than in CG. A significant increase in plasma ANP was observed in CG on and after the second day of HSP, while a significant increase in plasma ANP was observed on the fifth day of HSP in KG. 5. These findings indicate that K supplementation accelerates diuresis and natriuresis, resulting in moderate suppression of volume expansion induced by salt loading and that this accelerated diuresis and natriuresis is not a result of the action of ANP.     

心脏病患者血浆心钠素浓度初探

本文报道了采用放射免疫分析法检测的136例健康人和95例心脏病患者血浆心钠素含量的结果。健康人血浆心钠素含量为460．86±23．68ng／L，男女之间，年龄之间无明显差异。心脏病患者的血浆心钠素浓度均高于健康人，心脏病患者心功能越差，血浆心钠素浓度越高，其中以肺心病组变化最为明显。     

Ostial PV Isolation:

Pulmonary vein (PV) isolation by elimination of spike potentials has been reported to cure drug refractory atrial fibrillation. Because of the heterogenous morphology of the PVs, sequential electroanatomic reconstruction of the PVs was performed in 39 patients (group A), who underwent subsequent PV isolation by interruption of all conductive myocardial fibers by distinct RF current applications using a "lasso" approach. In group B (157 patients), only biplane two-dimensional fluoroscopy was performed to guide the diagnostic and the ablation catheters. After reprocedures (in 7% of patients in group A and 22% of group B), which depicted a recurrence of a spike potential inside or at the ostium of  >1 previously isolated PV in all restudied patients, stable sinus rhythm was documented in 69% of patients in group A and 60% of patients in group B. Reasons for the relapse of the previously eliminated spike potentials include a temporary ablation effect and a too distal interruption of the conducting myocardial fiber. Detailed knowledge of the individual three-dimensional morphology enhanced the clinical success rate of PV isolation but is time-consuming using CARTO   (8.0 ± 1.7 vs 5.0 ± 1.6, P < 0.001)   . Further technical improvement to fuse the individual three-dimensional anatomy and the electrophysiological markers to a composed "electroanatomic" map may overcome this limitation in the future. (PACE 2003; 26[Pt. II]:1624–1630)     

Atrial natriuretic peptide and verapamil can prevent gentamicin induced acute renal failure in the rat

Summary: Calcium channel blockers are able to improve renal function in acute renal failure (ARF) and natriuretic peptides can also exert beneficial effects. At present it is unknown whether administration of atrial natriuretic peptide (ANP) and a calcium channel blocker given before a toxic lesion can prevent gentamicin induced ARF. the mechanisms of action of natriuretic peptides and calcium channel blockers are different and, as yet, it has not been clarified if combined administration can augment the effects on renal function. After a basal period we investigated the effects of verapamil (VER, 0.66 mg/kg), ANP, (30 μg/kg) and a combination of both (identical doses as described individually). the drugs were given intravenously for a period of 40 min (infusion period) before gentamicin (15 mg/kg, i.v.) was administered for induction of ARF. Basal values for glomerular filtration rate (GFR, mL/min) were around 1.8 with no differences between the groups. At the end of the infusion period (before application of gentamicin) GFR was significantly elevated with VER + ANP (3.13 ± 0.51), ANP (2.70 ± 0.59) and VER (2.34 ± 0.47) compared to controls (saline, 1.7 ± 0.48). After application of gentamicin GFR significantly dropped in the control group (0.77 ± 0.21, 0.75 ± 0.19, respectively), indicating development of ARF. In contrast with VER + ANP, ANP and VER GFR could be maintained for 30 min (2.47 ± 0.39, 2.28 ± 0.33, 2.22 ± 0.43, respectively) and 130 min (2.11 ± 0.32, 1.86 ± 0.29, 2.11 ± 0.28, respectively) after gentamicin. Moreover ANP and VER revealed natriuretic activity and, due to their vasorelaxing potency, also influenced arterial blood pressure. We conclude that both VER and ANP are able to prevent early gentamicin induced ARF when given before the toxic lesion. Both drugs induce hyperfiltration while infused, in particular when administered in combination.     

A Decrease in Pulmonary Vein Diameter After Radiofrequency Ablation Predicts the Development of Severe Stenosis

A decrease in ostial pulmonary vein (PV) diameter was observed in patients on the day after radiofrequency ablation of atrial fibrillation (AF). This study examined whether a relative reduction in PV diameter on day 1 (RRPVD1) after the procedure predicts the late development of severe PV stenosis (PVS). The study included 104 consecutive patients (mean age = 55 years, range 46–61, 34 women) with drug refractory AF. Pulmonary vein diameter was measured using MR angiography (MRA) on the day before and on day 1 after the ablation procedure. The MRA was repeated every 3 months after the procedure. Severe PVS was defined as a >70% diameter reduction from the initial ostial diameter. The cut-off of RRPVD1 was prespecified as 25% decrease in initial diameter. The data are presented as medians and interquartile range. A total of 357 PV were treated. The RRPVD1 was 0.0% (0.0–11.1%). Severe PVS was found in 18 PV during a follow-up of 12 months (range 6–13). The log-rank analysis confirmed a strong association between a RRPVD1 ≥25% and the development of PVS (hazard ratio: 7.1; 95% confidence interval 3.8–13.5, P < 0.0001). By multivariate Cox regression model, after adjustment of procedure variables, RRPVD1 was the strongest predictor of development of severe PVS. RRPVD1 ≥25% was a strong independent predictor of development of severe PVS.     

雷米普利降低高血压患者心房颤动发生率以及改善左心房内径临床观察

目的观察血管紧张素转换酶抑制剂(ACEI)雷米普利降低高血压患者心房颤动(AF)发生率及对左心房内径的影响。方法将180例原发性高血压患者分为治疗组(90例)和对照组(90例)。治疗组给予雷米普利(2.5～15)mg/d口服,连服50个月。对照组苯磺碳氨氯地平(2.5～10)mg/d口服,连服50个月。结果治疗50个月后治疗组AF发生率3.4%,对照组AF发生率为8.05%;治疗组左心房内径缩小(2.0±1.5)mm,对照组左心房内径缩小(0.0±1.6)mm。2组相比P<0.05,有统计学意义。结论雷米普利可降低高血压患者AF的发生率并缩小左心房内径。