Prolonged post-faint hypotension can be reversed by dynamic tension

A severe variant of vasovagal syncope, observed during tilt tests and blood donation has recently been termed “prolonged post-faint hypotension” (PPFH). A 49-year-old male with a life-long history of severe fainting attacks underwent head-up tilt for 20 min, and developed syncope 2 min after nitroglycerine spray. He was unconscious for 40 s and asystolic for 22 s. For the first 2 min of recovery, BP and HR remained low (65/45 mmHg and 40 beats/min) despite passive leg-raising. Blood pressure (and symptoms) only improved following active bilateral leg flexion and extension (“dynamic tension”). During PPFH, when vagal activity is extreme, patients may require central stimulation as well as correction of venous return

Atrioventricular and interventricular delay optimization in cardiac resynchronization therapy: physiological principles and overview of available methods

In this review, the physiological rationale for atrioventricular and interventricular delay optimization of cardiac resynchronization therapy is discussed including the influence of exercise and long-term cardiac resynchronization therapy. The broad spectrum of both invasive and non-invasive optimization methods is reviewed with critical appraisal of the literature. Although the spectrum of both invasive and non-invasive optimization methods is broad, no single method can be recommend for standard practice as large-scale studies using hard endpoints are lacking. Current efforts mainly investigate optimization during resting conditions; however, there is a need to develop automated algorithms to implement dynamic optimization in order to adapt to physiological alterations during exercise and after anatomical remodeling

Insulin sensitivity and insulin clearance in human immunodeficiency virus-infected men

To test whether clinically stable human immunodeficiency virus (HIV) infection, like other infections, is associated with insulin resistance and increased insulin clearance, we measured the sensitivity to insulin and insulin clearance using the euglycemic insulin clamp technique in 10 clinically stable outpatients with symptomatic HIV infection (Centers for Disease Control [CDC] group IV) and 10 healthy controls. During administration of 0.8 and 4 mU insulin.kg-1.min-1, HIV-infected men had 40% (P less than .02) and 83% (P less than .01) higher rates of insulin clearance when compared with healthy controls. Despite significantly lower steady-state insulin concentrations (42 +/- 2 v 52 +/- 4 microU/mL, P less than .05, and 255 +/- 17 v 392 +/- 14 microU/mL, P less than .001, patients v controls), patients and controls had similar total glucose uptake (7.99 +/- 0.81 v 7.92 +/- 0.44 mg.kg-1.min-1 and 14.00 +/- 0.81 v 13.65 +/- 0.65 mg.kg-1.min-1, patients v controls). In the postabsorptive state, no differences were found between patients and controls in insulin levels (7 +/- 1 microU/mL in both) and endogenous glucose production (2.52 +/- 0.07 and 2.24 +/- 0.17 mg.kg-1.min-1, respectively), but plasma glucose levels in the patients (5.02 +/- 0.15 mmol/L) were significantly lower when compared with controls (5.46 +/- 0.14 mmol/L, P less than .05). The results indicate that HIV-infected men have increased rates of insulin clearance and increased sensitivity of peripheral tissues to insulin, which makes HIV infection unique with regard to glucose and insulin metabolis

Basal fuel homoeostasis in symptomatic human immunodeficiency virus infection

1. In eight clinically stable symptomatic human-immunodeficiency-virus-infected patients and in seven healthy control subjects, glucose and fat metabolism were studied, using indirect calorimetry and primed continuous infusions of [3-3H]glucose and [14C]palmitate. 2. Studies were performed in the post-absorptive state (16 h of overnight fasting) and again after 22 h of overnight fasting. 3. In the post-absorptive state, net fat oxidation and triacylglycerol ('triglyceride') concentrations were significantly higher in the patients, but concentrations and turnover of free fatty acids were not significantly different between patients and control subjects. After 22 h of overnight fasting, free fatty acid turnover in the patients rose to significantly higher levels when compared with the control subjects. 4. Post-absorptive glucose oxidation, glucose turnover and glucose clearance did not differ between patients and control subjects. Although fasting induced a significantly greater decline in glucose turnover in the patients, plasma glucose concentrations decreased comparably in patients and control subjects. 5. No differences were found in plasma concentrations of insulin or of the counter-regulatory hormones between patients and control subjects. 6. It is concluded that the metabolic adaptation to short-term starvation in clinically stable human-immuno-deficiency-virus-infected patients differs from that in healthy control subjects. Short-term starvation results in a significantly greater fall in glucose turnover, whereas fat metabolism is clearly stimulated. These alterations cannot be explained by differences in the concentrations of insulin or of the counter-regulatory hormone

Non-insulin-mediated glucose uptake in human immunodeficiency virus-infected men

1. One of the metabolic features of acquired immunodeficiency syndrome is increased tissue glucose uptake documented by euglycaemic-hyperinsulinaemic clamp studies, suggesting increased insulin sensitivity. However, these results may also be related to the confounding effect of increased non-insulin-mediated glucose uptake in acquired immunodeficiency syndrome, which will result in an erroneously presumed increased insulin sensitivity. To study the contribution of non-insulin-mediated glucose uptake to total tissue glucose uptake in acquired immunodeficiency syndrome, we conducted a hypoinsulinaemic clamp study in clinically stable human immunodeficiency virus-infected (Centers for Disease Control class IV) men (n = 7) and healthy subjects (n = 5). Glucose uptake was measured by a primed, continuous infusion of [3-3H]glucose in the postabsorptive state and during somatostatin-induced insulinopenia at euglycaemic (approximately 5.3 mmol/l) and hyperglycaemic (approximately 11 mmol/l) glucose concentrations. 2. Basal glucose concentration (patients, 5.2 +/- 0.1 mmol/l; control subjects, 5.3 +/- 0.1 mmol/l) and basal glucose tissue uptake (patients, 15.9 +/- 0.5 mumol min-1 kg-1 fat-free mass; control subjects, 15.2 +/- 0.4 mumol min-1 kg-1 fat-free mass) were not different between the two groups. 3. Euglycaemic glucose uptake during somatostatin infusion, reflecting non-insulin-mediated glucose uptake, decreased to 82 +/- 3% in patients and 78 +/- 2% in control subjects (not significant). Under hyperglycaemic (approximately 11 mmol/l) conditions with sustained insulinopenia, no differences in glucose uptake existed between the two groups (patients, 16.8 +/- 0.6 mumol min-1 kg-1 fat-free mass; control subjects, 16.1+/- 0.3 mumol min-1 kg-1 fat-free mass).(ABSTRACT TRUNCATED AT 250 WORDS

Septata intestinalis frequently isolated from stool of AIDS patients with a new cultivation method

Two species of microsporidia, Enterocytozoon bieneusi and Septata intestinalis have been reported as intestinal parasites of AIDS patients. In attempts to establish E. bieneusi in vitro, spores were concentrated from stool samples from 4 AIDS patients with biopsy-proven E. bieneusi infections. After sterilization of the concentrate in antibiotic solution, the spores were added to monolayers of RK13 cells grown on the membranes of Transwells. Cultures were established from 7 stool samples from the 4 patients but in every case the species established was S. intestinalis not E. bieneusi. On retrospective examination of the stools, a very small number of spores of a size comparable to that of S. intestinalis was found but this species was not detected in biopsies. Typical septate vacuoles containing Type I tubules were observed in vitro but in contrast to the original description, meronts were intravacuolar and sporogony was mainly disporoblastic. The cultivation system, used for the first time for microsporidia, revealed the presence of unsuspected S. intestinalis infections and indicates that this species may be much more common than hitherto suspected. S. intestinalis has not previously been culture

Hypothyroid-like regulation of the pituitary-thyroid axis in stable human immunodeficiency virus infection

Thyroid function and regulation were studied in 14 consecutive male outpatients with asymptomatic human immunodeficiency virus (HIV) infection (CDC II/III, n = 8) or AIDS (CDC IV, n = 6) who were free of concomitant infections and hepatic dysfunction, and in eight healthy, age- and weight-matched male controls. Blood was sampled every 10 minutes over 24 hours for measurement of thyrotropin (TSH). Thereafter, thyroid hormones and TSH responsiveness to thyrotropin-releasing hormone (TRH) were measured. Triiodothyronine (T3) and thyroxine (T4) did not differ between HIV-infected patients and controls, but HIV patients had lower thyroid hormone-binding index ([THBI] HIV patients, 1.01 +/- 0.02; controls, 1.11 +/- 0.03; P <.02), free thyroxine (FT4) index (94 +/- 3 v 110 +/- 4, P <.01), FT4 (11.8 +/- 0.4 v 14.3 +/- 0.4 pmol/L, P <.01), and reverse triiodothyronine (rT3) values (0.18 +/- 0.01 v 0.26 +/- 0.02 nmol/L, P <.001) and higher thyroxine-binding globulin ([TBG] 20 +/- 1 v 16 +/- 1 mg/L, P <.02) values. Mean 24-hour TSH levels were increased in HIV patients (2.39 +/- 0.33 v 1.44 +/- 0.16 mU/L, P <.05), associated with increased mean TSH pulse amplitude and TSH responsiveness to TRH. No differences were observed between asymptomatic HIV-seropositive and AIDS patients. In conclusion, there is a hypothyroid-like regulation of the pituitary-thyroid axis in stable HIV infection, which differs distinctly from the euthyroid sick syndrome in non-HIV-nonthyroidal illnesses.(ABSTRACT TRUNCATED AT 250 WORDS