CT follow-up in patients with neuroendocrine tumors (NETs): combined radiation and contrast dose reduction.

Background Frequent computed tomography (CT) follow-ups involve significant radiation related risks for patients with low-grade neuroendocrine tumors (NETs). Contrast agent (CA) application is essential for diagnostic evidence and has additional risks especially in patients with limited renal function. Purpose To investigate if a combination of dose and contrast agent (CA) reduction affects image quality and diagnostic evidence in neuroendocrine tumor (NET) patients. Material and Methods A total of 51 NET patients were enrolled in the study and 153 CT scans were analyzed. Patients underwent a baseline CT scan (A = 120 kVp, filtered back projection [FBP]) and two follow-up CTs (B = 120 kVp, adaptive statistical iterative reconstruction [ASIR] 40%; C1 = 100 kVp, ASIR 40%; C2 = 100 kVp, ASIR 60%; the latter two protocols were applied with a 30% reduction in CA volume). We evaluated image quality and applied dose. Results In C1/2, the combination of low kV (100 kVp) with ASIR 40%/60% reduced the mean applied dose significantly by 28% compared to B and by 57% compared to A. Signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) of tumor to liver/muscle were significantly increased by using C1/2 compared to B and A. With respect to subjective image quality, a slight loss of diagnostic confidence in C1 could be counterbalanced by the higher ASIR blending in C2. Conclusion Combined dose reduction techniques can be used to reduce radiation dose and CA volume without sacrificing image quality and diagnostic confidence in staging CT of NET patients.

Effect of co-contractions on the cardiovascular response to submaximal static handgrip.

The aim of this study was to investigate the influence of concomitant involuntary contractions of different muscles on heart rate (HR) and blood pressure (BP) during a sustained, submaximal handgrip. Nine male subjects [23.6 (0.4) years, 177.0 (1.5) cm, and 73.0 (2.7) kg, means (SE)] participated in the experiment. The maximal integrated electromyographic activity (IEMG max) of four ipsilateral muscles, flexor digitorum (FD), biceps brachii (BB), rectus abdominalis (RA) and vastus lateralis (VA), was recorded. Then, after 30 min of rest, the subjects maintained a submaximal isometric handgrip for 2 min. Heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure and surface electromyography (EMG) of the four muscles were recorded. The amplitude and power spectrum of the EMG were analysed. During the handgrip the force was kept constant at 43 (1)% of the maximum voluntary contraction (MVC) only for 90 (12) s. After that time, the subjects were unable to maintain the target force which decreased continuously up to the end of the contraction (P<0.01) with a residual force of 27 (3)% MVC at t = 120 s. HR increased from 75 (3) beats x min(-1) at rest to 109 (6) beats x min(-1) at t = 120 s (P<0.01). SBP and DBP also increased from 112 (5) and 81 (2) mm Hg to 176 (5) and 133 (7) mm Hg, respectively (P<0.01). The EMG activity rose significantly for both FD and BB with a moderate increase for RA and VL. In fact, the individual contributions of FD and BB to the EMG activity of the four muscles were 52 (2)% and 37 (2)%, respectively, whereas the RA and VL contributed only 9 (1)% and 1.4 (0.1)%. The amplitude ratio of FD's EMG to the total EMG activity of the four muscles from which recordings were made decreased with time from 72% to 33% (P<0.01). The central command's level of activation, as reflected by the increased EMG activity of the four recorded muscles, was probably high enough to stimulate the cardiovascular centres through cortical spread (sometimes known as cortical irradiation). On the other hand, maintaining an isometric handgrip at 43% MVC reduced local muscle blood flow and metabolites known to stimulate type III and IV afferents then accumulated, which in turn induced a reflex-mediated elevation of blood pressure. However, the relative forces developed by the co-contracting muscles were of low intensity (less than 20% MVC) and short duration compared to those of the muscle group under study. These results suggest that the mass of the muscle groups recruited during a fatiguing submaximal handgrip contributes little to the cardiovascular response.

The isometric force that induces maximal surface muscle deoxygenation.

To determine the external force that induces maximal deoxygenation of brachioradialis muscle 32 trained male subjects maintained isometric contractions using the elbow flexor muscles up to the limit time (isotonic part of the isometric contraction, IIC) and beyond that time for 120 s (anisotonic part of the isometric contraction). During IIC each subject maintained relative forces of either 25% and 70% maximal voluntary contraction (MVC), 50% and 100% MVC, or 40% and 60% MVC. Muscle oxygenation was assessed using a near infrared spectroscope, and expressed as a percentage of the reference value (deltaO2rest) which was the difference between the minimal oxygenation obtained after 6 min of ischaemia at rest and the maximal reoxygenation following the release of the tourniquet. During IIC at 25% MVC, muscle oxygenation decreased to 17 (SEM 3)% deltaO2rest, then it levelled off [25 (SEM 1)% deltaO2rest]. After the point at which target force could not be maintained, reoxygenation was very weak. During IIC at 40%, 50%, 60%, and 70% MVC, the lowest muscle oxygenation values were obtained after 15-20 s of contraction and corresponded to -18 (SEM 6), -59 (SEM 12) -31 (SEM 6), and -29 (SEM 6)% deltaO2rest, respectively. For the contraction at 100% MVC, the lowest oxygenation [-19 (SEM 9)% deltaO2rest] was obtained while force was decreasing (69% MVC). During the anisotonic part of the isometric contractions, the greatest reoxygenation rate was obtained after 50% MVC IIC (P < 0.001). Our results showed that during isometric elbow flexions between 25% and 100% MVC, there was no linear relationship between external force and muscle oxygenation, and that the maximal deoxygenation of the brachioradialis muscle was obtained at 50% MVC.

Influence of posture and training on the endurance time of a low-level isometric contraction.

Classically, the critical force of a muscle (the relative force below which an isometric contraction can be maintained for a very long time without fatigue) is comprised of between 15 and 20% of its maximum voluntary contraction (MVC). However, some authors believe that the value is below 10% MVC. If such is the case, signs that accompany the establishment of muscle fatigue (EMG changes, continuous increase in systolic blood pressure [SBP] and heart rate [HR]) would have to appear more rapidly and with a higher intensity if the muscle is already partially fatigued at the start of maintaining a contraction at 10% MVC. Twelve healthy untrained participants carried out two isometric contractions with the digit flexors: one (test A) began with a maximum contraction sustained for 4 min followed without interruption by a contraction at 10% MVC for 61 min; the other (test B) was a contraction maintained at 10% MVC for 65 min. For test B, after an initial increase of 4 bpm with respect to at rest, HR remained stable until the end of contraction, SBP progressively increased by 24 mm Hg in 28 min, then remained unchanged until the end, and there were no significant changes in EMG (absence of spectral deviation towards low frequencies). For test A, in spite of the initial maximum contraction, changes in the parameters being studied (total maintenance time, HR, SBP, EMG) during maintenance at 10% MVC were identical to those for test B. The results show that (1) when the number and intensity of the co-contractions are minimized by applying an appropriate posture, it is possible to sustain an isometric contraction at 10% MVC for at least 65 min without the appearance of signs of muscle fatigue; (2) the critical force of the digit flexors is higher than 10% MVC.

Cardiovascular changes during an isometric contraction combined to a cold pressor test.

Fifteen normotensive male subjects (age, 27.9 +/- 1.3 years) performed isometric contractions (handgrip) at 15, 30 and 50% maximal voluntary contraction respectively for 7, 3 and 1 min. The contractions were sustained with or without a cold pressor test of the same duration (immersion of one foot in water of 5.2 +/- 0.1 degrees C). At rest, under the influence of a cold pressor test for 3 min, the heart rate increased from 74.3 +/- 2.2 to 83.3 +/- 2.1 beats min-1 (P < 0.001) in less than 10 s, and returned to the control value in 3 min; on the contrary, at the end of 3 min of cold pressor test, the systolic blood pressure was still above the control value (135.5 +/- 4.2 and 121.0 +/- 3.2 mmHg, P < 0.001). During the contractions, there was no significant difference between heart rate and systolic blood pressure values obtained with or without cold pressor test. Similarly, there was no significant change in the concentrations of plasma catecholamines. This absence of cardiovascular effect of cold pressor test associated with isometric contraction (for three relative force levels) is probably due to the increasing importance of sympathetic cardiac activation produced by the contraction with respect to that produced by the cold pressor test, the absence of supplementary changes in total peripheral resistance and a partial reciprocal inhibition of pain produced by the simultaneous performance of these two tests.

Cardiovascular responses to leisure alpine skiing in habitually sedentary middle-aged men.

In order to evaluate the cardiovascular responses to leisure alpine skiing of habitually sedentary and not particularly active adult men, a series of continuous recordings of heart rate (HR) was performed on 10 subjects aged 51.0 +/- 1.3 years (mean +/- S.E.) during a 6-day ski trip at an altitude of 1000-2485 m. From the very first day, the subjects spontaneously adopted a regimen of intense physical activity, since 17.9% of the HR values recorded on the ski runs were higher than 85% of the maximal theoretical HR [THRmax (beats min-1) = 220--age (years)], which represented 19.5% of the actual skiing time. On day 2, 10.7% of the HR values were higher than 85% THRmax, or 17.9% of actual skiing time. For the entire ski trip, the mean HR during skiing was approximately 126 beats min-1, which corresponds to 75% THRmax. At rest, HR in the morning did not change significantly from days 2 to 6 (from 80 +/- 4 to 75 +/- 4 beats min-1, P > 0.05), whereas HR in the evening correlated significantly with the duration of physical activity during the day (r = 0.487, P < 0.001). In all cases, HR at rest was significantly higher than before the trip, except in the evening of day 4, the day on which the subjects skied less because they were fatigued after skiing in the morning. Systolic blood pressure (SBP) at rest was always lower than the control established before the trip, whether taken in the morning or in the evening.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the heart rate and electromyogram beyond the limit time of an isotonic isometric contraction.

Nine men [24.6 (SEM 1.1) years] carried out isometric contractions (IC) of the right elbow flexors at 50% and 100% of the maximal voluntary contraction (MVC). At 50% MVC they had to maintain IC until the limit time (isotonic IC: IIC50) and beyond for as long as possible (anisotonic IC: AIC50). At 100% MVC, IC was anisotonic since the decrease in force was immediate (AIC100). Measurements of the force, the integrated electromyogram (iEMG) and the heart rate (fc) were made during the entire period of contraction. There was a linear relationship between the iEMG increase and the fc increase for IIC50 and AIC100. This relationship was not found for AIC50. The role played by the peripheral information would seem to have become more important in fc regulation when the isotonic IC preceding the anisotonic IC was sufficiently long (submaximal IIC). It would seem that the idea of muscle exhaustion at the limit time was only relative, and depended greatly on the subject's motivation and his capacity to endure a certain degree of pain.

Carotid stenosis is a powerful predictor of a positive exercise electrocardiogram in a large hyperlipidemic population.

Hypercholesterolemia is a major risk factor in coronary heart disease (CHD) and ischemic stroke. However, there is no general agreement on the usefulness of systematic screening of patients with hyperlipidemia by stress exercise electrocardiogram (ECG). The feasibility of this approach would depend on selecting patients with a high risk of CHD, since the sensitivity and specificity of the test depends on the prevalence of the disease. In view of the association of CHD and ischemic stroke, we undertook a study to determine whether the presence of atherosclerosis in the carotid arteries was predictive of a positive exercise ECG in a group of 778 asymptomatic patients referred to their hyperlipidemia. We a much higher percentage of positive exercise ECG in patients with carotid atherosclerosis in our ultrasonographic examinations. In a multiple regression analysis which included 13 parameters (age, sex, body mass index, arterial blood pressure, lipid parameters, serum level of glucose, smoking status and the severity of carotid lesions), the strongest predictors of a positive exercise ECG test were age (P = 0.014) and the degree of carotid atherosclerosis (P = 0.010). We therefore conclude that hyperlipidemic patients with atherosclerotic lesions on carotid arteries would benefit most from screening by the exercise ECG.

Complementary roles of central command and muscular reflex in the regulation of heart rate during submaximal isometric contraction.

During submaximal isometric contraction, the heart rate (HR) and the electromyographic activity (EMG) increase continuously. Although activation of the muscle and the cardiovascular center is placed partly under the common control of the central command, the nature of the relationship that may exist between HR and the integrated electromyogram (iEMG) is seldom studied. Seventeen healthy men, 22.4 +/- 0.5 years of age (M +/- SE), performed isometric contractions with the right elbow flexors. Forces of 25, 40, 50 and 65% of the maximum voluntary contraction (MVC) were used, and the contractions were sustained until (isotonic isometric contraction: IIC) and beyond exhaustion (anisotonic isometric contraction: AIC). During IIC, a linear relationship exists between HR and iEMG; the slope of this relationship is independent of the relative force developed, which is in favor of a predominant role played by the central command in HR increase. The increase in the ratio iEMG/HR at the approach of local muscular exhaustion would indicate that at the end of IIC there is an increase in the relative part furnished by the information of peripheral origin in HR regulation. During AIC, the force (F) decreases in an exponential manner and stabilizes at around 25% MVC from tAIC = 70 s on. The iEMG and HR change independently: iEMG decreases like F such that iEMG/F remains constant; HR continues to increase in the first phase corresponding to the rapid decrease in F and iEMG, then in a second phase, it decreases linearly with respect to time. Our results suggest that the action of the central command is dominant during stage 1 of AIC, while during stage 2 the relative part furnished by the muscle reflexes increases. Beyond tAIC = 70 s, there seems to be a certain degree of central fatigue.

[The static exercise-induced arterial hypertension test]. / Test d'hypertension artérielle provoquée par effort statique.

The exercise tests used in the detection and follow-up of hypertensive patients fall into two categories: isotonic (dynamic) and isometric (static). The isometric exercise-induced arterial hypertension test consists of an isometric contraction--usually a grip by the dominant hand--sustained for 3 minutes, with a strength that is 30 percent of maximum voluntary strength. This results in a continuous and parallel increase of systolic and diastolic blood pressures during the hand grip. The heart rate also continuously rises, though not to the level obtained by the isotonic exercise test. The increase in cardiac output observed, despite a fall in stroke volume, and the absence of decrease in peripheral vascular resistance contribute to a sometimes considerable rise in blood pressure, particularly diastolic pressure. These cardiovascular responses do not depend on the muscular mass involved but on the relative strength developed during isometric contraction. Owing to the lack of strict standardization and longitudinal studies, the isometric exercise test is of little value in the early detection of arterial hypertension. However, it is useful in the follow-up of hypertensive patients, as it provides precise information on the point of impact and mode of action of several antihypertensive drugs.

[Absence of a direct effect of peritoneal dialysate on venous lower limb flow]. / Absence d'effet direct du dialysat péritonéal sur le retour veineux des membres inférieurs.

In order to verify if the presence of 21 of fluid in the peritoneum is likely to produce a slowing of the venous flow in the lower limbs, 34 patients suffering from end stage chronic renal failure and treated by continuous ambulatory peritoneal dialysis (CAPD) were followed up for two years by means of noninvasive methods. The maximum femoral venous flow velocity before and during CAPD was evaluated using Doppler effect, in 2 positions of the patients (recumbent or upright), and with or without dialysate (abdomen full or empty). The venous distensibility and the maximum venous outflow were evaluated using venous occlusion plethysmography in the recumbent position. Despite a decrease in mean arterial blood pressure (before the start of CAPD: 116.0 +/- 3.7 mm Hg; after 2 years of CAPD: 104.3 +/- 3.2 mm Hg, p less than 0.02), there was no significant slowing of the venous limb flow during the two years of treatment by CAPD, and in no case did the peritoneal fluid constitute a mechanical obstruction.

Cardiovascular response to static handgrip in trained and untrained men.

The influence of aerobic capacity on the cardiovascular response to handgrip exercise, in relation to the muscle mass involved in the effort, was tested in 8 trained men (T) and 17 untrained men (U). The subjects performed handgrip exercises with the right-hand (RH), left-hand (LH) and both hands simultaneously (RLH) at an intensity of 25% of maximal voluntary contraction force. Maximal aerobic capacity was 4.3 l.min-1 in T and 3.21 l.min-1 in U (P less than 0.01). The endurance time for handgrip was longer in T than in U by 29% (P less than 0.05) for RH, 38% (P less than 0.001) for LH and 24% (P less than 0.001) for RLH. Heart rate (fc) was significantly lower in T than in U before handgrip exercise, and showed smaller increases (P less than 0.01) at the point of exhaustion: 89 vs 106 beats.min-1 for RH, 93 vs 100 beats.min-1 for LH and 92 vs 108 beats.min-1 for RLH. Stroke volume (SV) at rest was greater in T than in U and decreased significantly (P less than 0.05) during handgrip exercise in both groups of subjects. At the point of exhaustion SV was still greater in T than in U: 75 vs 57 ml for RH, 76 vs 54 ml for LH and 76 vs 56 ml for RLH. During the last seconds of handgrip exercise, the left ventricular ejection time was longer in T than in U. Increases in cardiac output (Qc) and systolic blood pressure did not differ substantially between T and U, nor between the handgrip exercise tests.(ABSTRACT TRUNCATED AT 250 WORDS)

[Changes in blood pressure during static work. Practical implication]. / Modifications de la pression artérielle au cours du travail statique. Implications pratiques.

while the cardiocirculatory response to dynamic exercises (e.g. running, cycling, swimming) is the object of the physician's full attention, the cardiovascular repercussions of static exercises, such as weight-lifting, sustained postures in gymnastics or immobilization in judo, are often ignored. Yet any sustained isometric contraction is associated from the art with an increase in blood pressure which may be major and involves about equally the systolic and diastolic pressures. As soon as the strength developed by the muscle exceeds 20 p. 100 of its maximum voluntary strength (MVS) the increase of blood pressure continues until the contraction comes to an end. Whatever the muscle used, the intensity of a cardiovascular response is independent of the muscular mass in action, but it mostly depends on the MVS percentage This rise in blood pressure is mainly due to an increase in heart and cardiac output. The reactions are such that relatively moderate and localized static effort may result in a rapid and important increase in myocardial work, and this may cause serious accidents in subject with a cardiovascular weakness, either isolated or associated with such risk factors as age or arterial hypertension. In consequence, adults who are insufficiently trained and present with one or several risk factors should avoid sports which required frequent respiratory arrests and/or sustained postures. If such sports are nevertheless chosen, it would seem that practising also a dynamic sport relying on aerobic metabolism might lin , at least in part, the effects of increased blood pressure due to static activities.

Fatigue induced by static work.

Despite its low energy cost, isometric contraction can result in the onset of local muscle fatigue. The onset of fatigue occurs more rapidly when the relative force exerted is greater than 15-20% of the maximum voluntary contraction (MVC) of the muscle considered, and when the contraction time is increased. The maximum maintenance time (limit-time) and the corresponding relative force are linked by a hyperbolic relation. Ischaemia promotes accumulation of acid metabolites produced during contraction, and hinders their elimination, thus constituting the main causal factor in the onset of local muscle fatigue. The introduction of rest periods of sufficient duration to ensure restoration of normal blood flow through the muscle is an effective way of delaying, or even preventing, the onset of muscle fatigue. Other factors may also be taken into account, such as the position in which the static work is performed, and the nature and number of muscles used simultaneously, etc. Numerous laboratory and field studies have allowed the development of various models that take into account the conditions relating to isometric contractions during static work.

Cardiovascular and sympatho-adrenal responses to static handgrip performed with one and two hands.

12 healthy men aged 21-25 years performed, in the sitting position, a sustained handgrip at 25% of their maximum voluntary contraction, first with each hand separately and then with both hands simultaneously. Heart rate (HR), systolic blood pressure (SBP), stroke volume (determined reographically) and plasma catecholamine concentration were measured during each handgrip test. The HR and SBP increased consistently during each handgrip test while stroke volume decreased by approximately 20% of the initial value. Cardiac output did not change significantly. There were no significant differences in the magnitude and dynamics of the cardiovascular responses between the tests with one and with both hands. Plasma noradrenaline and adrenaline levels showed similar elevations in response to handgrip performed with the right hand and with both hands, while during the exercise performed with the left hand the increase in the plasma catecholamine concentration was less pronounced. It was concluded that: (1) during sustained handgrip, performed in the sitting position by young healthy subjects, the stroke volume markedly decreases and cardiac output does not change significantly in spite of the increased HR; (2) the cardiovascular and sympatho-adrenal responses to static handgrip do not depend on the mass of contracting muscle when the same relative tension is developed.

[Clinical aspects of continuous ambulatory peritoneal dialysis in diabetics]. / Les aspects cliniques de la dialyse péritonéale continue ambulatoire chez les diabétiques.

The treatment of end stage renal diabetic nephropathy remains a challenge. A large experience allows us to clearly outline the advantages and the drawbacks of continuous ambulatory peritoneal dialysis (CAPD). 81 patients, mean age 51.3 years, were treated over the past nine years by CAPD-CCPD. Extrarenal complications, mainly vascular lesions, account for qualifying these patients as a high risk population. The technique was modified in order to inject insulin intraperitoneally, four times per day, to control blood glucose level. Peripheral vascular disease was prospectively studied in 19 patients. Actuarial survival was 92% at one year, 50% at four years mainly influenced by age: 85% survival at two years in 35 patients aged less than 50 years and 62% at two years in 46 patients aged more than 50 years. The main causes of death were of cardiovascular origin: arteritis, myocardial infarction, stroke. The main causes for transfer to an alternative method of treatment were technical complications. Peritonitis rate was one episode ever 14 months. Satisfactory control of blood pressure, blood glucose levels, main biological parameters, visual status were the clear advantages of the method. Peripheral vascular disease is not influenced by the technique. CAPD can be the technique of first choice in young diabetics awaiting a kidney transplant and the reference technique for home dialysis.

Physiological modifications of local haemodynamic conditions during bilateral isometric contractions.

Nine subjects (five women and four men) simultaneously performed two isometric contractions sustained until exhaustion at different relative forces: 40% of maximum voluntary contraction (MVC) for the right elbow flexors; 50% MVC for the left elbow flexors. Contraction of the left elbow flexors commenced at 50% of the limit time (maximum maintenance time) of isometric contraction of the right elbow flexors. Increase in heart rate during concomitant contraction of the left elbow flexors led to an increase in blood flow to the right elbow flexors. Under these conditions, the limit time of isometric contraction of the right elbow flexors was prolonged with respect to the limit time obtained for an isolated isometric contraction at the same relative tension. The difference was more significant in the female (+40%, P less than 0.05) than in the male subjects (+20%, P greater than 0.05).

Effect of arm position on cardiovascular responses during isometric handgrips.

Sixteen subjects (eight women and eight men, age 20-25 years) carried out in the seated position, isometric contractions sustained until exhaustion of the digital flexors. The subject's arm was placed in two positions, high and low. The muscle tensions used were 30, 40 and 50% of maximum voluntary contraction (MVC). Under these conditions, for a given relative force, the duration of contraction (limit-time) was not modified by the arm position. In the male subjects, increases in heart rate (HR) and systolic blood pressure (SBP) were slightly more pronounced in the low than the high position, but the differences were not significant. Limit times in the high position were similar to those in the low position, and, in the absence of an increase in HR and SBP, this seemed to be due to an increase in cardiac output consequent upon a transient improvement in venous return together with an increase in the coefficient of oxygen utilization.