Cardiac Abnormalities in Adult Patients With Polymyositis or Dermatomyositis as Assessed by Noninvasive Modalities.

OBJECTIVE: Cardiac events are a major cause of death in patients with idiopathic inflammatory myopathies. The study objective was in a controlled setting to describe cardiac abnormalities by noninvasive methods in a cohort of patients with polymyositis (PM) or dermatomyositis (DM) and to identify predictors for cardiac dysfunction. METHODS: In a cross-sectional study, 76 patients with PM/DM and 48 matched healthy controls (HCs) were assessed by serum levels of cardiac troponin I, electrocardiography, Holter monitoring, echocardiography with tissue Doppler imaging, and quantitative cardiac (99m) Tc-pyrophosphate ((99m) Tc-PYP) scintigraphy. RESULTS: Compared to HCs, patients with PM/DM more frequently had left ventricular diastolic dysfunction (LVDD) (12% versus 0%; P = 0.02) and longer QRS and QT intervals (P = 0.007 and P < 0.0001, respectively). In multivariate analysis, factors associated with LVDD were age (P = 0.001), disease duration (P = 0.004), presence of myositis-specific or -associated autoantibodies (P = 0.05), and high cardiac (99m) Tc-PYP uptake (P = 0.006). In multivariate analysis of the pooled data for patients and HCs, a diagnosis of PM/DM (P < 0.0001) was associated with LVDD. CONCLUSION: Patients with PM or DM had an increased prevalence of cardiac abnormalities compared to HCs. LVDD was a common occurrence in PM/DM patients and correlated to disease duration. In addition, the association of LVDD with myositis-specific or -associated autoantibodies and high cardiac (99m) Tc-PYP uptake supports the notion of underlying autoimmunity and myocardial inflammation in patients with PM/DM.

Saline-induced natriuresis and renal blood flow in conscious dogs: effects of sodium infusion rate and concentration.

AIM: This study focused on static and dynamic changes in total renal blood flow (RBF) during volume expansion and tested whether a change in RBF characteristics is a necessary effector mechanism in saline-induced natriuresis. METHODS: The aortic flow subtraction technique was used to measure RBF continuously. Identical amounts of NaCl (2.4 mmol kg(-1)) were given as slow isotonic (Iso, 120 min), slow hypertonic (Hyper, 120 min), and rapid isotonic loads (IsoRapid, 30 min). RESULTS: During Iso and IsoRapid, arterial blood pressure increased slightly (6-7 mmHg), and during Hyper it remained unchanged. Iso and Hyper increased sodium excretion (4 +/- 1 to 57 +/- 27 and 10 +/- 4 to 79 +/- 28 micromol min(-1), respectively) and decreased plasma renin activity (by 38% and 29%), angiotensin II (by 56% and 58%) and aldosterone (by 47% and 65%), while RBF remained unchanged. IsoRapid caused a similar increase in sodium excretion (to 72 +/- 19 micromol min(-1)), a similar decrease in renin system activity, but a 15% elevation of RBF (282 +/- 22 to 324 +/- 35 mL min(-1)). Selected frequency domain parameters of RBF autoregulation did not change in response to any load. CONCLUSIONS: In response to slow saline loading simulating daily sodium intake, the rate of sodium excretion may increase 10-20-fold without any change in mean arterial blood pressure or in RBF. Regulatory responses to changes in total body NaCl levels appears, therefore, to be mediated primarily by neurohumoral mechanisms and may occur independent of changes in arterial pressure or RBF.

Effects of oxytocin in normal man during low and high sodium diets.

AIM: We tested the hypothesis that oxytocin in normal man causes natriuresis by means of nitric oxide and/or atrial natriuretic peptide. METHODS: Normal male subjects were investigated after 4 days of sodium controlled diets (30 mmol sodium chloride day(-1), n = 8 or 230 mmol sodium chloride day(-1), n = 6). Oxytocin was infused intravenously (1 pmol kg(-1) min(-1) for 240 min). RESULTS: Mean arterial blood pressure, heart rate and glomerular filtration rate by clearance of chromium-labelled ethylenediaminetetraacetate remained stable. Plasma oxytocin increased from 2 to 3 pg mL(-1) to around 50 pg mL(-1). Oxytocin decreased urine flow (4.2 +/- 0.2--0.75 +/- 0.11 and 4.6 +/- 1.3-1.4 +/- 0.6 mL min(-1), low- and high-salt diet, respectively). During low-salt conditions, oxytocin reduced sodium and potassium excretion (11 +/- 2--4 +/- 2 and 93 +/- 19--42 +/- 3 micromol min(-1), respectively). Plasma renin, angiotensin II, aldosterone and renal excretion of metabolites of nitric oxide (nitrate and nitrite) all decreased. Plasma atrial natriuretic peptide and cyclic guanosine monophosphate were unchanged. A similar pattern was obtained during high-salt conditions but in this case the antinatriuresis was not different from that occurring during the corresponding time control series. CONCLUSIONS: The data reject the hypothesis. In contrast, we found significant antinatriuretic, antikaliuretic and antidiuretic effects, which were not mediated by the renin-angiotensin-aldosterone system, atrial natriuretic peptide, systemic haemodynamics, or processes increasing urinary excretion of metabolites of nitric oxide. The natriuretic effect of oxytocin found in laboratory animals is species-specific.

Mechanisms of acute natriuresis in normal humans on low sodium diet.

This study evaluates the relative importance of several mechanisms possibly involved in the natriuresis elicited by slow sodium loading, i.e. the renin-angiotensin-aldosterone system (RAAS), mean arterial blood pressure (MAP), glomerular filtration rate (GFR), atrial natriuretic peptide (ANP), oxytocin and nitric oxide (NO). Eight seated subjects on standardised sodium intake (30 mmol NaCl day(-1)) received isotonic saline intravenously (NaLoading: 20 micromol Na(+) kg(-1) min(-1) or approximately 11 ml min(-1) for 240 min). NaLoading did not change MAP or GFR (by clearance of (51)Cr-EDTA). Significant natriuresis occurred within 1 h (from 9 +/- 3 to 13 +/- 2 micromol min(-1)). A 6-fold increase was found during the last hour of infusion as plasma renin activity, angiotensin II (ANGII) and aldosterone decreased markedly. Sodium excretion continued to increase after NaLoading. During NaLoading, plasma renin activity and ANGII were linearly related (R = 0.997) as were ANGII and aldosterone (R = 0.999). The slopes were 0.40 pM ANGII (mi.u. renin activity)(-1) and 22 pM aldosterone (pM ANGII)(-1). Plasma ANP and oxytocin remained unchanged, as did the urinary excretion rates of cGMP and NO metabolites (NO(x)). In conclusion, sodium excretion may increase 7-fold without changes in MAP, GFR, plasma ANP, plasma oxytocin, and cGMP- and NO(x) excretion, but concomitant with marked decreases in circulating RAAS components. The immediate renal response to sodium excess appears to be fading of ANGII-mediated tubular sodium reabsorption. Subsequently the decrease in aldosterone may become important.

Aortic blood flow subtraction: an alternative method for measuring total renal blood flow in conscious dogs.

We have measured total renal blood flow (TRBF) as the difference between signals from ultrasound flow probes implanted around the aorta above and below the renal arteries. The repeatability of the method was investigated by repeated, continuous infusions of angiotensin II and endothelin-1 seven times over 8 wk in the same dog. Angiotensin II decreased TRBF (350 +/- 16 to 299 +/- 15 ml/min), an effect completely blocked by candesartan (TRBF 377 +/- 17 ml/min). Subsequent endothelin-1 infusion reduced TRBF to 268 +/- 20 ml/min. Bilateral carotid occlusion (8 sessions in 3 dogs) increased arterial blood pressure by 49% and decreased TRBF by 12%, providing an increase in renal vascular resistance of 69%. Dynamic analysis showed autoregulation of renal blood flow in the frequency range <0.06-0.07 Hz, with a peak in the transfer function at 0.03 Hz. It is concluded that continuous measurement of TRBF by aortic blood flow subtraction is a practical and reliable method that allows direct comparison of excretory function and renal blood flow from two kidneys. The method also allows direct comparison between TRBF and flow in the caudal aorta.