[Cardiovascular autonomic reflexes on the postural orthostatic tachycardia syndrome]. / Réflexes autonomiques cardiovasculaires dans le syndrome de tachycardie orthostatique idiopathique.

Postural orthostatic tachycardia syndrome (POTS) is an inadequately understood pathology because its diagnosis is not based on the conventional methods of investigation. The orthostatic test allows to make the diagnosis easily. The objective of this study is to determine cardiovascular autonomic reflexes of 70 patients having POTS. The tests of exploration of the autonomic nervous system practised are: deep breathing, hand grip, mental stress and orthostatic test. The analysis of orthostatic test showed that the increase of the cardiac frequency, relative to the state of "beta" peripheral sympathetic hyperactivity occurred before the 2nd minute in 80% of patients. The POTS was considered "florid" in 43% of patients and had complicated of a rough and severe fall of systolic blood pressure inferior to 70 mmHg in four patients, after the fifth minute of the test. The analysis of the different tests had shown vagal hyperactivity in 63% of patients on deep breathing, in 93% of patients on hand grip and in 100% on orthostatic test. The "alpha" central sympathetic activity was increased in 76% of the cases and "beta" central sympathetic activity was high in 83% of cases. The "alpha" peripheral hyperactivity was observed in 63% of patients on hand grip, and in 44% on orthostatic test. The analysis of cardiovascular autonomic reflexes in patients affected by POTS allowing the determination of their autonomic profile, will contribute probably to a better understanding of this pathology and to a better orientation of its care.

[Sympathetic response in primary hypertension]. / Les réponses sympathiques dans l'hypertension artérielle essentielle.

UNLABELLED: High blood pressure (BP) is a major cause of cardiovascular disease and primary hypertension is a frequent pathological condition. Sympathetic hyperactivity may be involved in primary hypertension. The purpose of this study was mainly to evaluate sympathetic activity when performing cardiovascular autonomic profile examination in patients with primary hypertension in comparison with normotensive subjects. PATIENTS AND METHODS: This prospective study included one group of hypertensive patients (n=120, mean age 54 years) compared with a control group (n=120, mean age 52 years) of normotensive subjects. Autonomic tests included deep-breathing (DB), hand-grip (HG) and echostress test (ES). Comparison tests between the two groups, similar in age, were expressed as mean+/-SE and made using the t Student test, p<0.05 was considered significant. RESULTS: Alpha-adrenergic sympathetic response using ES method produced a BP response of 20,0%+/-9,8 in hypertensive patients group and 15,2%+/-8,6 in the control group (p<0.001). Alpha-adrenergic sympathetic response using three minutes HG test was of 16,7%+/-7,5 in hypertensive patients group and 13,3%+/-6,5 in the control group (p<0.001). Vagal stimulation in hypertensive group after DB showed that electrocardiographic: ECG (EKG) waves R (RR) interval variation was of 30,2%+/-8,1 meanwhile in the control group this RR variation was of 46,1%+/-21,1 p<0.001, and the one of HG of 15 seconds was 17,6%+/-10,2 versus 32,5%+/-12,7 p<0.001. CONCLUSION: Hypertensive patients had a significantly higher sympathetic response to central and peripheral stimulations and a significantly lower parasympathetic response when compared to normotensive controls.

[Evaluation of the vagal activity by the Deep-Breathing test]. / Evaluation de l'activité vagale par le test de la respiration profonde (Deep-Breathing).

OBJECTIVE: The Deep-Breathing (DB) test is of major importance in the evaluation of the vagal response (VR). We applied this test to assess the VR in a group of subjects with functional (neurological, cardiovascular or digestive) symptoms unexplained by standard cardiac examination and to compare it with the VR measured in a group of healthy controls. PATIENTS AND METHODS: The following groups were considered: a C-Group of healthy controls (n=50), and three groups each consisting of 50 symptomatic patients (S1, S2, S3). Subjects in the S1-Group had a postural orthostatic tachycardia syndrome (POTS), while members of the S2-Group had arterial hypertension, and members of S3-Group had neither POTS nor arterial hypertension. The VR was expressed as a percentage variation of RR intervals 100x[(RR(max)-RR(min))/RR(min)], and was correlated with age and sex in the C-Group before any comparison. RESULTS: In controls the VR was 31.0%+/-8.2. It was negatively correlated with age (r=-0.42, p=0.003) and there was no significant difference between males (31.2%+/-5.7) and females (30.9%+/-9.0) (p=0.12). Compared to the C-Group, the VR was 51.6%+/-20.4 in the S1-Group (p<0.001), 26.9%+/-11.3 in the S2-Group (p<0.001), and 47.2%+/-22.7 in the S3-Group (p<0.001). CONCLUSION: The VR was independent of sex but was negatively correlated with age. In comparison with healthy controls, it was significantly increased in the patients with POTS and significantly decreased in hypertensives.

Effects of adrenalectomy or RU-486 on rat muscle fibers during hindlimb suspension.

The purpose of this study was to investigate the effects of a glucocorticoid antagonist, RU-486, and of adrenalectomy (ADX) on rat skeletal muscle structural properties after 3, 7, and 14 days of hindlimb suspension (H). After H, a significant loss in muscle weight was observed as early as 3 days in soleus (SOL; -10%) and adductor longus (AL; -14%) muscles. In SOL, after only 7 days, a reduction (-14%) in type I fiber percent distribution occurred, accompanied by an increase (+129%) in intermediate type I fibers. Fiber type changes increased depending on the duration of H. In AL muscle, no change occurred after H in the fiber type composition despite a similar degree of muscle atrophy. Treatment with RU-486 or ADX significantly reduced the loss of SOL weight observed after 14 days (-42 and -44%, respectively, vs. -50% for H rats), delayed the SOL atrophy (from 3 to 7 days), and normalized the shift in fiber type distribution induced by H. In SOL, administration of RU-486 (but not ADX) partly prevented the reduction in size induced by H of all the fibers. In AL, neither treatment affected the extent of muscle atrophy, even though the reduction in type IIa fiber size was prevented by RU-486 but not by ADX after 14 days of suspension. ADX or RU-486 administration did not prevent the extensor digitorum longus weight loss observed after 14 days of suspension but allowed a recovery of its normal fiber type composition.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of torbafylline on muscle atrophy: prevention and recovery.

The effects of torbafylline on the prevention of and the recovery from 5 weeks of hindlimb suspension induced atrophy were analyzed in rat soleus and extensor digitorum longus muscles. Muscle alterations were investigated by determining a suite of electrophysiological, histochemical, and muscle ultrastructural characteristics. Administration of torbafylline during the suspension period was ineffective in preventing any of the observed muscle atrophic changes. Application of torbafylline during the recovery period resulted in a faster recovery of some soleus muscle structural and functional properties. Mitochondrial volume densities and capillary to fiber ratios returned towards baseline values earlier in the recovery process with torbafylline. Furthermore, the drug significantly improved soleus muscle fatigue resistance 4 weeks after cessation of hindlimb suspension.