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PubMedDate not supplied

[Cryopreservation of bone marrow and peripheral blood stem cells using a controlled rate freezing system: experience with 86 procedures].

UNLABELLED: The cryopreservation of hematopoietic stem cells can be used for rescuing the hematopoiesis after high dose chemotherapy. PURPOSE: The ice crystal formation during the freezing procedure is the key point that can be harmful to the cells. The cryopreservation of hematopoietic stem cells in a controlled-rate freezer could decrease the cell damage. METHODS: Twenty-three patients with a median age of 26 years (range 03-57) had bone marrow and/or peripheral blood stem cells harvested from March 1993 through October 1994, ending up to 86 freezing procedures. The patient's diagnoses are as follows: Non-Hodgkin's Lymphoma (n = 5); Acute Myelogenous Leukemia (n = 8); Acute Lymphocytic Leukemia (n = 6); Hodgkin's disease (n = 3); Multiple Myeloma (n = 1). The cells were frozen away in a controlled-rate freezer chamber at the following rate: -1 degree C/min from room temperature to -45 degrees C and then, at -10 degrees C/min down to -80 degrees C. After freezing, the cells were kept into mechanical freezers until the marrow infusion. To mobilize PBSC (peripheral blood stem cells), G-CSF (granulocyte colony stimulating factor) was given. RESULTS: A median of 3.16 x 10(8) cells/kg (range 0.86-24.22) of PBSC and 2.03 x 10(8) cells/kg (0.19-12.21) of bone marrow cells were frozen. The median time to reach granulocytes greater than 500/microL and platelets greater than 20,000/microL was 12 days (range 8-40) and 31 days (range 8-80), respectively. All patients had marrow engraftment after infusion of hematopoietic stem cells. CONCLUSION: The cryopreservation procedure using a controlled-rate freezer can store hematopoietic stem cells and potentially, cause less damage to the cells.

Adolescent↗
PubMed2004

A perspective on rate control in the treatment of atrial fibrillation.

Until recently, the standard approach to therapy of atrial fibrillation (AF) in most cases was restoration and maintenance of sinus rhythm (rhythm control). Although difficult to accomplish, and associated with potential serious adverse effects of antiarrhythmic agents, this therapeutic approach was influenced by the belief that rhythm control was associated with better survival, fewer symptoms, better exercise tolerance, lower risk of stroke, better quality of life, and absence of need for long-term anticoagulation. However, four clinical trials comparing rate control with rhythm control have failed to demonstrate these advantages, indicating that rate control should be considered a legitimate primary therapeutic option, particularly in patients at risk for stroke. Pursuit of rate or rhythm control should be decided on a case-by-case basis.

Anti-Arrhythmia Agents↗
PubMed2002

[Atrial fibrillation: rhythm or rate control?].

For many years it has been considered that it was necessary, whenever possible, to cardiovert atrial fibrillation and to maintain the sinus rhythm with antiarrhythmic drugs. There are many theoretical advantages to this maintenance of the sinus rhythm. Nevertheless the choice of the drugs used to maintain rhythm is often difficult and the therapeutical index of these drugs may be poor. It is necessary to avoid class I antiarrhythmic drugs in patients with congestive heart failure and coronary artery disease. In these cases, only sotalol and amiodarone can be used. The safety index of these drugs being low, plain rate control with persistence of atrial fibrillation has been proposed as a treatment alternative. Several drugs may be used: calcium inhibitors, beta-blockers, digitalis. It is always necessary to associate anticoagulation: of course if rate control is chosen, but also if rhythm control is obtained, owing to the possible risk of relapse. Several trials of comparison between these 2 strategies have been recently performed. Available results show no clear superiority of a strategy above the other but there is a tendency towards a lower mortality in the rate control group.

Adrenergic beta-Antagonists↗
PubMed1991

Successful cryopreservation of human bone marrow does not require a controlled-rate freezer.

We studied CFU-GM recovery from bone marrow samples frozen either in a machine for controlled-rate freezing or in a -70 degrees C freezer. We found no statistically significant difference between the two methods. Cooling-curve investigations also demonstrated that it was possible to obtain satisfactory cooling rates simply by manipulation of the shape and volume of the marrow and its container. Five patients received a total of six successful autografts for which their marrow cells were frozen without controlled-rate freezing. Thus it is not necessary to use a sophisticated machine in order to obtain satisfactory cryopreservation of human marrow stem cells.

Bone Marrow↗
PubMed1995

Atrial fibrillation and flutter: maintaining stability of sinus rhythm versus ventricular rate control.

Two major treatment strategies have emerged for managing atrial fibrillation: maintaining sinus rhythm by chronic administration of suppressive antiarrhythmic agents versus controlling the ventricular rate and chronic anticoagulation. Potential benefits of maintenance of sinus rhythm include improvement of the hemodynamic profile of the patient, a decreased risk of cerebrovascular accidents, reduced symptoms, and, if atrial fibrillation is successfully suppressed, possible elimination of the need for the chronic anticoagulation. When selecting long-term antiarrhythmic drug therapy for suppression of atrial fibrillation, it should be recalled that at least 50% of patients have a recurrence of the arrhythmia within the first year and the majority of other patients have a recurrence within the next 3 to 5 years. In addition, the risk of proarrhythmia and sudden cardiac death must be considered; this has stimulated interest in nonpharmacologic approaches to maintaining sinus rhythm. Large multicenter randomized trials are now under way to compare the benefits and risks of maintaining sinus rhythm versus controlling the ventricular rate and chronically anticoagulating patients in atrial fibrillation. Important endpoints of these trials include mortality, functional capacity, and quality of life.

Anti-Arrhythmia Agents↗
PubMed1998

Rate issues in atrial fibrillation: consequences of tachycardia and therapy for rate control.

Atrial fibrillation (AF) is an arrhythmia resulting in loss of atrial contribution to ventricular filling, an irregular ventricular contraction, and an inappropriately rapid ventricular rate. An uncontrolled ventricular response may result in various changes of ventricular function and structure referred to as tachycardia-related cardiomyopathy. However, the effects of tachycardia may be reversible with adequate pharmacologic or nonpharmacologic interventional rate control. The purpose of this review article is to discuss the present knowledge regarding tachycardia-related cardiomyopathy and therapy for rate control.

Animals↗
PubMed2005

[The control rate of irbesartan/hydrochlorothiazide combination regimen in the treatment of Chinese patients with mild to moderate hypertension].

OBJECTIVES: To analyse the control rate of irbesartan/hydrochlorothiazide (HCTZ) combination tablets (COAPROVEL) in the treatment of patients with mild to moderate primary hypertension. METHODS: In this multi-center, open, single therapy trial, the enrolled patients aged 18-75 were treated with irbesartan/HCTZ combination tablets for 8 weeks. The initial dose comprised one tablet of irbesartan (150 mg)/HCTZ (12.5 mg) once a day during the first 2 weeks. If diastolic blood pressure was greater than 85 mm Hg at the end of the second or fourth weeks, irbesartan (300 mg)/HCTZ (12.5 mg) once a day or irbesartan (300 mg)/HCTZ (25 mg) once a day were added respectively. RESULTS: In 968 patients with mild to moderate hypertension enrolled, 920 patients were followed up for 8 weeks. (1) After 1 week of treatment, irbesartan/HCTZ combination tablets lowered systolic blood pressure by 11.87 mm Hg and diastolic blood pressure by 8.54 mm Hg (P < 0.01). After 8 weeks of treatment, the corresponding decreases were 21.97 mm Hg and 16.08 mm Hg, respectively (P < 0.01). (2) After 2, 4 and 8 weeks of treatment, 526, 703 and 769 patients reached blood pressure target (diastolic blood pressure less than 85 mm Hg). The control rates were 57.17%, 76.41% and 83.59%, respectively. (3) Among the 920 patients who completed the trial, 637 patients took irbesartan (150 mg)/HCTZ (12.5mg) once a day (69.24%), 211 patients took irbesartan (300 mg)/HCTZ (12.5 mg) once a day (22.93%), and 72 patients took irbesartan (300 mg)/HCTZ (25 mg) once a day (7.82%). (4) In the intention-to-treat analysis, no adverse reaction was observed in 903 patients (93.29% of the patients enrolled). CONCLUSIONS: When irbesartan/HCTZ combination regimen are used in the treatment of patients with mild to moderate primary hypertension, the proportion of patients reaching blood pressure target is high and adverse reactions are rare.

Adolescent↗
PubMed2004

Breast cancer metastases in liver: laser-induced interstitial thermotherapy--local tumor control rate and survival data.

PURPOSE: To evaluate the local tumor control rate and survival data for magnetic resonance (MR) imaging-guided laser ablation of breast cancer liver metastases by using laser-induced interstitial thermotherapy (LITT). MATERIALS AND METHODS: MR-guided LITT was performed in 232 female patients with 578 liver metastases from breast cancer. Survival rates were calculated with the Kaplan-Meier method. Indications for the procedure were defined for patients with no more than five metastases, none of which were larger than 5 cm in diameter, as follows: recurrent liver metastases after partial liver resection (8.2%), metastases in both liver lobes (45.2%), locally nonresectable tumors (19%), general contraindications for surgery (2.6%), or refusal to undergo surgical resection (25%). RESULTS: Local recurrence rate at 6-month follow-up after LITT was 2.3% (five of 213) for metastases up to 2 cm in diameter, 4.3% (seven of 162) for metastases 2-3 cm in diameter, 3.2% (two of 63) for metastases 3-4 cm in diameter, and 1.9% (one of 52) for metastases larger than 4 cm in diameter. No additional local tumor progression was observed beyond 6 months. The mean survival rate for all treated patients, with calculation started on the date of diagnosis of the metastases treated with LITT, was 4.9 years (95% confidence interval: 4.3, 5.4). The median survival was 4.3 years; 1-year survival, 96%; 2-year survival, 80%; 3-year survival, 63%; and 5-year survival, 41%. The mean survival after the first LITT treatment was 4.2 years (95% confidence interval: 3.6, 4.8). CONCLUSION: MR-guided LITT yields high local tumor control and survival rates in patients with liver metastases from breast cancer.

Adult↗
PubMed1996

Hypertension awareness, treatment and control rates for an Asian population: results from a national survey in Korea.

OBJECTIVE: This observational study was performed in order to determine the hypertension awareness, treatment, and control rates for the country of Korea. METHODS: Rates were determined in conjunction with a national blood pressure survey in Korea in 1990. Through cluster sampling, individuals aged > 30 in 190/146,944 districts were selected for study. Among 25,567 eligible individuals, 21,242 had measurement of blood pressure (BP) and answered a standard questionnaire. BP was recorded as the mean of two measurements with a standard mercury manometer. Hypertension was defined either as BP > or = 160/95 mm Hg or on treatment (n = 2628), or as BP > or = 140/90 mm Hg or on treatment (n = 4219). Treatment was defined as any method of BP treatment, including dietary, traditional, or medication. RESULTS: Rates for BP > or = 160/95 mm Hg or on treatment: aware 1057 (40%), treated 696 (27%), controlled 367 (14%). Rates for BP > or = 140/90 mm Hg or on treatment: aware 1069 (25%), treated 696 (16%), controlled 221 (5%). CONCLUSIONS: Hypertension awareness, treatment, and control rates are relatively low in Korea. Blood-pressure control programs, including detection strategies, are needed here and worldwide.

Adult↗
PubMed1984

Rate control of phosphorylation-coupled respiration by rat liver mitochondria.

Liver mitochondria provided with an oxidizable substrate, ATP, oxygen, and an ADP-generating system (soluble F1-ATPase) were used to reevaluate the rate-controlling step(s) intrinsic to all of the processes of mitochondrial oxidative phosphorylation. The quantity termed "control strength" (C), previously defined as the fractional change in flux through a (system) induced by a fractional change in the concentration of an individual enzyme in the system, has been used to evaluate rate-influencing steps in this overall process by carefully defining the dimensions of the "system" under analysis. If the system is defined by a suspension of mitochondria provided with substrates, plus an extrinsic ADP-generating process (ATPase), the value of C of the latter for the overall process of phosphorylation-linked respiration is near 1.0 until the capacity of the mitochondria to phosphorylate ADP is approached, after which C for the soluble ATPase becomes zero as the maximum capacity for phosphorylation is attained. Carboxyatractyloside was found only marginally to inhibit respiration stimulated by ATPase, even when a large percentage of adenine nucleotide translocase molecules were immobilized. The relative lack of effect of carboxyatractyloside on phosphorylating respiration is explained by the readjustment of the concentration of one of the substrates (ADP) and an inhibitor (ATP), which results from inhibition of adenine nucleotide translocase. The residual blunted inhibition of respiration is explained by product inhibition of the ADP-regenerating ATPase, and not necessarily to any intrinsically mitochondrial intermediate process. The system being evaluated can be redefined to include only the processes intrinsic to mitochondria. This can be achieved by providing exactly comparable substrate concentrations to the mitochondria under comparable incubation conditions. Under these conditions, the adenine nucleotide translocase is the principal, if not the only, rate-controlling step in the overall process of oxidative phosphorylation until a new rate-limitation is attained (ATP synthesis). These data are consistent with the conclusion that, at intermediate rates of phosphorylation-coupled respiration, the extramitochondrial ATP/ADP ratio regulates this process through its kinetic effects on the catalytic properties of the adenine nucleotide translocase.

Adenosine Diphosphate↗
PubMed1980

Development of autonomic heart rate control in the kitten during sleep.

Development of cardiac rate control was studied in 34 kittens aged 4 days to 6 wk during quiet and active sleep, using atropine and propranolol to quantitatively assess the degree of tonic parasympathetic and sympathetic control, with the analysis based on the Rosenblueth and Simeone model. The order of blocking agent administration did not significantly affect the results if a correction was made for the baroreceptor-mediated heart rate change after the blockade of a single autonomic branch. During the first 4 wk, the heart rate in quiet sleep was lower than in active sleep due to a significantly higher parasympathetic tone. The heart rate decreased with age in both sleep states: the decrease in quiet sleep was accompanied by a transition from sympathetic to parasympathetic dominance. The intrinsic rate of the pharmacologically denervated heart was maximum at about 2 wk and decreased steadily thereafter. The observed changes may help explain some features of the development in heart rate previously reported for sleeping human infants.

Aging↗
PubMed1986

Determination of the dissolution rate controlling process for isomeric amides in alkane solvents.

The mechanisms that control the dissolution rates of chemical compounds in liquids have long been of interest to pharmaceutical scientists. Generally, control of the dissolution rate can be classified as being by interfacial reaction rate or by the rate of mass transport. Little work has been done in the area of sparingly soluble compounds dissolving in nonpolar organic solvents. In this study the dissolution of three isomers of methylacetanilide was investigated in three nonpolar organic solvents (hexane, heptane, and cyclohexane). The dissolution apparatus used a flat plate into which the nondisintegrating tablet could be placed so that dissolution occurred only from one face of the tablet. Agitation was provided by a four-bladed stirrer whose outer edge was 2 cm from the tablet surface. Dissolution data were collected only for concentrations less than 5% of the saturation solubility of the given compound in the given solvent. All dissolution profiles were linear. Dissolution rates were obtained from the slopes of these plots. Plots of In (dissolution rate) versus In (stirring speed) were also linear and yielded slopes that were close to the value of 0.50 predicted by the convective diffusion model employed.

Amides↗
PubMed1995

Rate control within the Na+/glucose cotransporter.

The intestinal Na+/glucose cotransporter has recently been cloned and expressed in Xenopus oocytes, and kinetically characterised to produce a 6-state model of the transporter. We have analyzed this model using control analysis to determine the extent to which each rate constant and step in the mechanism limits the steady-state rates under various conditions. We show that control (rate limitation) is distributed among a number of rate constants and changes with the membrane potential and the concentrations of external and internal sodium and sugar. There is no single rate-limiting step but, with saturating concentrations of external sugar and sodium and negligible internal concentrations, the sugar and sodium fluxes are limited by sodium dissociation on the inside, translocation of the unloaded carrier to the outside and translocation of the fully loaded carrier to the inside. With more physiological external and internal concentrations there is a significant leak flux, which causes the cotransporter to act as a sugar uniporter, and entails that control over the sugar flux differs from control over the sodium flux. In these conditions control is widely distributed among many of the rate constants. The analysis shows that the concept of a rate-limiting step is not generally applicable to transporters.

Animals↗
PubMed1999

The effect of heart rate control on myocardial ischemia among high-risk patients after vascular surgery.

UNLABELLED: Patients undergoing vascular surgery have a high risk of suffering major postoperative cardiac events. Preoperative myocardial ischemia as detected by Holter monitoring identifies a high-risk subgroup whose postoperative ischemia, similarly detected, seems to herald major cardiac events. In this study, we determined whether systematic, patient-specific postoperative heart rate control with beta-adrenergic blocker therapy decreases the incidence of postoperative ischemia among high-risk vascular surgery patients. A total of 26 of 150 patients who underwent elective vascular surgery and were monitored preoperatively by 24-h Holter were found to have significant myocardial ischemia as defined by ST-segment depression. The minimal heart rate at which this ST-segment depression occurred was identified (ischemic threshold), and these 26 patients were then randomized to receive continuous i.v. beta-blockade with esmolol or placebo plus usual medical therapy, aiming to reduce the postoperative heart rate to 20% below the ischemic threshold. All patients were monitored by Holter for 48 h postoperatively. Postoperative Holter readings were analyzed for the incidence of ischemia and for the number of hours during which heart rate was controlled below the ischemia threshold. Patients had a median of two episodes of preoperative ischemia lasting a median of 30 min (range 1-155 min). A total of 15 patients were randomized to receive esmolol, and 11 were randomized to receive placebo. The two groups were comparable with respect to clinical characteristics and incidence and duration of preoperative ischemia. Ischemia persisted in the postoperative period in 8 of 11 placebo patients (73%), but only 5 of 15 esmolol patients (33%) (P < 0.05). Of the 15 esmolol patients, 9 had mean heart rates below the ischemic threshold, and all 9 had no postoperative ischemia. A total of 4 of 11 placebo patients had mean heart rates below the ischemic threshold, and 3 of the 4 had no postoperative ischemia. There were two postoperative cardiac events among patients who had postoperative ischemia (one placebo, one esmolol) and whose mean heart rates exceeded the ischemic threshold. Our data suggest that patient-specific, strict heart rate control aiming for a predefined target based on individual preoperative ischemic threshold was associated with a significant reduction and frequent elimination of postoperative myocardial ischemia among high-risk patients and provide a rationale for a larger trial to examine this strategy's effect on cardiac risk. IMPLICATIONS: Patients who undergo peripheral vascular surgery often experience transient cardiac complications and/or permanent heart damage just after surgery because of inadequate myocardial blood flow. In this study, we identified patients at high risk of cardiac complications after vascular surgery and showed that if their heart rate was carefully controlled for 48 h after surgery, myocardial ischemia, a common marker of heart injury, was markedly reduced.

Adrenergic beta-Antagonists↗
PubMed1998

Rate control therapy for atrial fibrillation following coronary artery bypass surgery.

Atrial fibrillation (AF) is a common complication of coronary artery bypass surgery (CABS). Because conventional antiarrhythmic therapy may cause proarrhythmia, a rate control approach to AF was evaluated in 59 patients post-CABS. The use of digoxin with or without verapamil for AF was associated with spontaneous conversion to normal sinus rhythm in 55 of 59 patients. Two to four weeks later, all patients were on digoxin and 12% were on verapamil, with two of four AF patients having converted to normal sinus rhythm and two others previously in normal sinus rhythm now in AF. A rate control approach to treating AF post-CABS resulted in over 90% of patients being in normal sinus rhythm for two to four weeks after the onset of the arrhythmia.

Administration, Oral↗
PubMed2006

Accuracy of dual-source CT coronary angiography: First experience in a high pre-test probability population without heart rate control.

The aim of this study was to assess the diagnostic accuracy of dual-source computed tomography (DSCT) for evaluation of coronary artery disease (CAD) in a population with extensive coronary calcifications without heart rate control. Thirty patients (24 male, 6 female, mean age 63.1+/-11.3 years) with a high pre-test probability of CAD underwent DSCT coronary angiography and invasive coronary angiography (ICA) within 14+/-9 days. No beta-blockers were administered prior to the scan. Two readers independently assessed image quality of all coronary segments with a diameter > or =1.5 mm using a four-point score (1: excellent to 4: not assessable) and qualitatively assessed significant stenoses as narrowing of the luminal diameter >50%. Causes of false-positive (FP) and false-negative (FN) ratings were assigned to calcifications or motion artifacts. ICA was considered the standard of reference. Mean body mass index was 28.3+/-3.9 kg/m2 (range 22.4-36.3 kg/m2), mean heart rate during CT was 70.3+/-14.2 bpm (range 47-102 bpm), and mean Agatston score was 821+/-904 (range 0-3,110). Image quality was diagnostic (scores 1-3) in 98.6% (414/420) of segments (mean image quality score 1.68+/-0.75); six segments in three patients were considered not assessable (1.4%). DSCT correctly identified 54 of 56 significant coronary stenoses. Severe calcifications accounted for false ratings in nine segments (eight FP/one FN) and motion artifacts in two segments (one FP/one FN). Overall sensitivity, specificity, positive and negative predictive value for evaluating CAD were 96.4, 97.5, 85.7, and 99.4%, respectively. First experience indicates that DSCT coronary angiography provides high diagnostic accuracy for assessment of CAD in a high pre-test probability population with extensive coronary calcifications and without heart rate control.

Adult↗
PubMed1986

Measurement of right ventricular blood temperature during exercise as a means of rate control in physiological pacemakers.

Several biological parameters have been suggested for rate control in physiological pacemakers in the past. Up to now, measurements of central venous blood temperature have been mostly done on dogs. We studied central venous blood temperature and heart rate in 14 healthy volunteers under conditions of treadmill and bicycle exercise with different workloads. A custom-made 5F lead with a thermistor incorporated near the tip was placed at the right ventricle under fluoroscopic control. Temperature was recorded with an accuracy of 1/100 degrees C on a digital memory device at a sampling rate of 5-10 s. We found the increase in blood temperature to be not only a function of absolute workloads but also a function of the individual's maximum exercise tolerance. Independent of the absolute increase in heart rate and temperature at a given workload, the individual's relation of increase in temperature and heart rate was found to be highly correlating (r = 0.9095). At a load of 100 W, we found a mean increase in heart rate of 52 beats and of temperature of 0.57 degree C, at 150 W of 74 beats/min and 0.84 degree C. During, as well as after, the exercise, heart rate and temperature have a parallel course. According to our data, control of physiological pacemakers by means of central venous blood temperature is possible.

Blood↗