Disturbed sympathetic and also parasympathetic activity of the autonomic nervous system points to pathological alterations in the cardiovascular system. Untreated hypertensive subjects were examined with respect to the question of whether an increase in sympathetic activity necessarily goes along with a reduction in parasympathetic activity, and whether 'delayed' recovery behaviour after mental stress could be an indicator of a disturbed cardiovascular function. In 20 male hypertensive (HT) and 20 normotensive (NT) subjects (control group), heart rate variability (HRV) was compared during rest and under mental stress. The testing procedure consisted of the following phases: habituation, arithmetic tasks without and with interference, recovery. HRV was analysed using the trigonometric regressive spectral analysis (TRS). Proceeding from the total variance (ms 2 ), the weighted averaged frequency (Hz) and the variance parts (ms 2 ) in the frequency bands 'low frequency' (LF-band: 0.04-0.15 Hz) and 'high frequency' (HF-band: 0.15-0.40 Hz) were explored. The variance part modulated by spontaneous breathing within the HF-band was assessed additionally. The variance part in the LF-band under mental stress was significantly increased in the HT group (Po0.01). Activity in the HF-band (without the respiration-dependent part) under mental stress did not differ between both groups, whereas the breathing-modulated part of variance in the HF-band was reduced in the HT subjects. During the recovery period in the HT group, the weighted averaged frequency was still elevated compared to baseline, and the variance part in the LF-band was increased, which may point to delayed recovery behaviour. In addition, by using a discriminant analysis 85% of all subjects were reclassified to the original groups, all HT subjects being assigned 'correctly'. Spectral variance parameters enable early discovery of altered cardiovascular regulation. Respiration influences variance in the HF-band in hypertensive subjects and should therefore be paid attention to. The variance part in the LF-band, weighted averaged frequency and the respiration-modulated variance in the HF-band turned out to be the most valid parameters for the differentiation between NT and HT subjects.
Postural Orthostatic Tachycardia Syndrome (POTS) is a clinical syndrome characterized by the presence of tachycardia in the absence of orthostatic hypotension; symptoms of orthostatic intolerance (presyncope and syncope) are present secondary to autonomic dysfunction (1). It is thought that one of the implications for POTS involves plasma volume disturbances leading to blood pooling. The Renin Angiotensin Aldosterone System (RAAS) is one system that assists in plasma volume regulation (2). In this study we hypothesized that these disturbances are brought about by an inactivation of RAAS. This was done by retrospectively reviewing the medical records of POTS patients. In these patients, diagnosis of POTS was established by an increase in Heart Rate of over 30 bpm within 10 minutes of tilt. Stroke Volume was used as a measure of volume disturbances; those POTS patients whose stroke volumes had not increased by the End of the Tilt as compared to their 6 minute supine baseline were considered to have an inactivation of RAAS. Our total sample of POTS patients numbered at 447, out of which 417 patients had lower stroke volumes at the end of their tilt table tests when compared to their baseline; this makes for 92.87% of our POTS Patient Sample. The average Stroke Volume at the 6 minute mark was calculated to be 74.67; the average stroke volume at the end of the tilt table test (30 minutes) was calculated to be 46.33 mL; . The results seen in this study show that more than 90% of our POTS Patient Sample there is no recovery of the stroke volume by the end of the tilt table test, this volume disturbance can be the result of decreased RAAS activation. This observation is supported by the difference found between average stroke volumes seen at 6 minute baseline and at 30 minutes of tilt. In normal individuals, we should see an increase in stroke volume at the end of the tilt as RAAS is activated. However, as patients with POTS are known to have lower plasma volumes (2), compounded with the inactivation of RAAS; the resulting hypovolemia will amplify the symptoms of POTS, increasing their severity. These patients should respond well to fludrocortisone, as there will be a correction of hemodynamic impairments (RAAS inactivation) leading to symptomatic relief (3). Further studies and analyses are needed to look into the levels of Renin and Aldosterone at Baseline & at Tilt, as well as the effects of fludrocortisone on such patients with RAAS inactivation. References:(1) Satish R. R., Circulation. 2013. June 11; 127(23): 2336-2342.(2) Satish R. R. et al., Circulation. 2005. March 2; 111(13): 1574-1582. (3) Freitas. J et al., Clin Auton Res. 2000. October; 10(5): 293-303. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to ...
Introduction: Postural Orthostatic Tachycardia Syndrome (POTS) is a form of dysautonomia which primarily affects young adult women. The hallmark of this condition is an exaggerated heart rate in response to postural changes. The symptoms of POTS can cause cerebral hypoperfusion and include generalized weakness, dizziness, lightheadedness, darkening of the visual fields and in some, palpitations and loss of consciousness. Increased sympathetic activation results in increase of the conduction through the AV node. Increased conduction through the AV node results in a shorter PR interval and a faster heart rate. The aim of this study is to determine if patients with severe POTS have resting Adrenal Hyperactivity by utilizing PR-Intervals. Methods: A team of researchers randomly selected pts with POTS from our clinic. This group consisted of 455 pts and these pts’ tilt table results as well as their resting ECG’s were reviewed from their electronic medical records. Pts were then categorized based on the degree of change in heart rate during the tilt table test. The categories were as follows: Orthostatic intolerance (<30 bpm), mild POTS (30-50 bpm), and severe POTS (>50 bpm). A few patients in the data set did not have tilt table results and were subsequently removed. We noted the resting PR intervals of these pts from their multiple ECG’s. For each pt the mean of these values was gathered and biostatistical analysis was performed on this first collection of data. After the first data was analyzed, a second team of researchers, blinded to the first team, collected the same data set on patients with POTS from our clinic. This was done in order to minimize observer bias and reproduce results. This team of researchers further filtered out 8 patients whose data did not meet the criteria required to categorize the patients, thus the second data set consisted of 447 pts. Tilt table results and resting PR intervals were taken from their electronic medical records and the pts were then categorized in the same manner as the first data set. Results: In the second group of 447 pts (n=447), 28.6% (n= 128) are categorized as having orthostatic intolerance, 51.6% (n=231) are categorized as mild POTS, and 19.6% (n=88) are categorized as severe POTS. Using a significance level of 0.05, the P-value was lower than 0.05 (0.00787), thus ANOVA fails to accept the null hypothesis that the means of the PR-intervals across the various categories are equal. That is to say, statistically the resting PR intervals are not equal across the different POTS categories in both groups with a significance level of 0.05. Average P-R (Severe POTS:137.0 ms & Orthostatic Intolerance: 145.59 ms) Conclusion: A statistically significant increase in resting Adrenal Hyperactivity in pts with severe POTS (>50 bpm) as opposed to pts with Orthostatic Intolerance (<30 bpm); the severity of which may have long-term prognostic significanc...
A 62-year-old man presented with a 2-year history of syncope, collapse and fluctuating blood pressure (BP). His medications included midodrine (10 mg, three times per day) and fludrocortisone (0.1 mg, two times per day), but neither treatment afforded symptomatic relief. Autonomic testing was performed. Head-up tilt table testing revealed a supine BP of 112/68 mm Hg (heart rate, 74 beats per minute (bpm)) after 6 min, which dropped to 76/60 mm Hg (83 bpm) within 2 min of 80° head-up tilt. Findings from a heart rate with deep breathing test and a Valsalva test were consistent with autonomic dysfunction. The patient was diagnosed with neurogenic orthostatic hypotension and treated with droxidopa (100 mg, two times per day; titrated to 100 mg, one time per day). After initiating treatment with droxidopa, the patient no longer reported losing consciousness on standing and experienced improvement in activities of daily living. These improvements were maintained through 1 year of follow-up.
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