Propranolol decreases tachycardia and improves symptoms in the postural tachycardia syndrome: less is more

Postural tachycardia syndrome and inappropriate sinus tachycardia: role of autonomic modulation and sinus node automaticity

BACKGROUND

Inappropriate sinus tachycardia (IST) and postural tachycardia syndrome (POTS) are 2 disorders characterized by sinus tachycardia. It is debated whether the pathophysiology of IST and POTS results from abnormal autonomic regulation or abnormal sinus node function. We hypothesized that intrinsic heart rate (IHR) after autonomic blockade would be increased in patients with IST but not POTS.

METHODS AND RESULTS

We enrolled 48 POTS patients, 8 IST patients, and 17 healthy control (HC) subjects. Intravenous propranolol and atropine were given to block the sympathetic and parasympathetic limbs of the autonomic nervous system in order to determine the IHR. Patients with IST have a higher sympathetic contribution to heart rate when compared with POTS patients (31±13 bpm versus 12±7 bpm, P<0.001) and HC (8±4 bpm; P<0.001) and a trend to less parasympathetic contribution than POTS and HC (IST: 31±11 bpm versus POTS: 46±11 bpm versus HC: 48±11 bpm, ANOVA P=0.108). IHR was not significantly different between IST and either POTS or HC (IST: 111±11 bpm versus POTS: 108±11 bpm versus HC: 106±12 bpm, ANOVA P=0.237).

CONCLUSIONS

IST patients have more sympathetic tone when compared with either POTS or HC, but IST patients do not have abnormal sinus node automaticity. These data suggest that the treatment of IST and POTS should focus on sympatholysis, reserving sinus node modification for patients with continued debilitating symptoms after beta-blockade and possibly ivabradine.

CLINICAL TRIAL REGISTRATION URL

http://clinicaltrials.gov/. Unique identifier: NCT00262470.

Visceral sensitization in postural tachycardia syndrome

OBJECTIVE

Both psychogenicity and organicity have been asserted in postural tachycardia syndrome (PoTS). We studied the genesis of palpitations to dissect the biologic nature of PoTS.

METHODS

Eleven PoTS patients and 10 control subjects were asked to discriminate types of palpitations when supine and in response to two sympathetic stimuli [Valsalva maneuver (VM) and 10-min head-up tilt (HUT)] and one vagolytic stimulus (atropine administration). Participants rated the 10 items of the somatosensory amplification scale to assess symptom exaggeration. Their time-dependent heartbeat counts were compared against EKG data to study ability to perceive heartbeat.

RESULTS

Maximal heart rate increase (mean ± SE) over baseline (bpm) did not differ statistically between patients and controls (VM, 39.3 ± 4.7 versus 28.9 ± 3.9, respectively; p = 0.11; HUT, 42.4 ± 4.2 versus 34.7 ± 2.6, respectively; p = 0.14; and atropine, 47.8 ± 2.5 versus 52.0 ± 2.1, respectively; p = 0.22). Palpitations were more frequent in patients at baseline (55 versus 0 %, p = 0.006) and with VM (82 versus 10 %, p = 0.001) and HUT (64 versus 0 %, p = 0.002), but not with atropine (64 versus 60 %, respectively; p = 0.86). Patients discriminated more types of palpitations than did controls (seven versus three types). No difference was observed in somatosensory amplification or heartbeat perception.

INTERPRETATION

Palpitations were independent of tachycardia and were predominantly sympathetically mediated. The lack of somatosensory amplification militated against psychogenicity. PoTS patients were not superior in detecting peripheral cardiac sensation. However, patients were superior in discriminating palpitations qualitatively in response to individual stimuli, suggesting central visceral sensitization. Explanation of the nature of symptoms and pharmacologic management may be of therapeutic benefit.

Acute hemodynamic effects of a selective serotonin reuptake inhibitor in postural tachycardia syndrome: a randomized, crossover trial

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) are often prescribed in patients with postural tachycardia syndrome (POTS), and act at synaptic terminals to increase monoamine neurotransmitters. We hypothesized that they act to increase blood pressure and attenuate reflex tachycardia, thereby improving symptoms. Acute hemodynamic profiles after SSRI administration in POTS patients have not previously been reported.

METHODS

Patients with POTS (n=39; F=37, 39 ±9 years) underwent a randomized crossover trial with sertraline 50mg and placebo. Heart rate, systolic, diastolic, and mean blood pressure were measured with the patient seated and standing for 10 min prior to drug or placebo administration, and then hourly for 4 h. The primary endpoint was standing heart rate at 4 h.

RESULTS

At 4 h, standing heart rate and systolic blood pressure were not significantly different between sertraline and placebo. Seated systolic (106±12 mmHg vs. 101±8 mmHg; p=0.041), diastolic (72±8 mmHg vs. 69±8 mmHg; p=0.022), and mean blood pressure (86±9 mmHg vs. 81±9 mmHg; p=0.007) were significantly higher after sertraline administration than placebo. At 4 h, symptoms were worse with sertraline than placebo.

CONCLUSIONS

Sertraline had a modest pressor effect in POTS patients, but this did not translate into a reduced heart rate or improved symptoms.

A double-blind placebo-controlled cross-over study of the vascular effects of midodrine in neuropathic compared with hyperadrenergic postural tachycardia syndrome

POTS (postural tachycardia syndrome) is a chronic form of OI (orthostatic intolerance). Neuropathic POTS is characterized by decreased adrenergic vasoconstriction, whereas hyperadrenergic POTS exhibits increased adrenergic vasoconstriction. We hypothesized that midodrine, an α1-adrenergic receptor agonist, would increase CVR (calf vascular resistance), decrease C(v) (calf venous capacitance) and decrease orthostatic tachycardia in neuropathic POTS, but not alter haemodynamics in hyperadrenergic POTS. A total of 20 POTS patients (12 neuropathic and eight hyperadrenergic), ages 12-20 years, participated in this randomized placebo-controlled double-blind cross-over study. Of these subjects, 15 were female. POTS subjects received 2 weeks of treatment with midodrine or placebo, with increased dosing from 2.5 to 10 mg three times daily. Following a 7-day drug-washout period, subjects received the cross-over treatment. HR (heart rate), MAP (mean arterial pressure), Q(calf) (calf blood flow) and CVR were measured supine and during 35° HUT (head-up tilt). C(v) was measured supine. In neuropathic POTS, midodrine decreased supine HR, Q(calf) and C(v), while increasing MAP and CVR compared with placebo. During HUT, in neuropathic POTS, midodrine decreased HR, Q(calf) and C(v), while increasing MAP and CVR. In hyperadrenergic POTS, placebo and midodrine both decreased upright HR and increased supine CVR. Placebo also increased supine C(v), compared with midodrine in hyperadrenergic POTS. Therefore midodrine improved postural tachycardia in neuropathic POTS by increasing CVR and decreasing Q(calf) and C(v), whereas these effects were not seen in hyperadrenergic POTS patients who experienced a placebo effect. This suggests that midodrine is probably an effective treatment for neuropathic POTS, but not for hyperadrenergic POTS.

Postural orthostatic tachycardia syndrome (POTS)

Postural orthostatic tachycardia syndrome (POTS) is a heterogeneous group of conditions characterised by autonomic dysfunction and an exaggerated sympathetic response to assuming an upright position. Up till recently, it was largely under-recognised as a clinical entity. There is now consensus about the definition of POTS as a greater than 30/min heart rate increase on standing from a supine position (greater than 40/min increase in 12-19-year-old patients) or an absolute heart rate of greater than 120/min within 10 min of standing from a supine position and in the absence of hypotension, arrhythmias, sympathomimetic drugs or other conditions that cause tachycardia. We present two cases of POTS, followed by a discussion of its pathogenesis, pathophysiology, epidemiology and management.

Effects of norepinephrine reuptake inhibition on postural tachycardia syndrome

Background

Postural tachycardia syndrome (POTS) is a disorder of chronic orthostatic intolerance accompanied by excessive orthostatic tachycardia. Patients with POTS commonly have comorbid conditions such as attention deficit hyperactivity disorder, depression, or fibromyalgia that are treated with medications that inhibit the norepinephrine reuptake transporter (NRI). NRI medications can increase sympathetic nervous system tone, which may increase heart rate (HR) and worsen symptoms in POTS patients. We sought to determine whether NRI with atomoxetine increases standing tachycardia or worsens the symptom burden in POTS patients.

Methods and Results

Patients with POTS (n=27) underwent an acute drug trial of atomoxetine 40 mg and placebo on separate mornings in a randomized, crossover design. Blood pressure (BP), HR, and symptoms were assessed while seated and after standing prior to and hourly for 4 hours following study drug administration. Atomoxetine significantly increased standing HR compared with placebo (121±17 beats per minute versus 105±15 beats per minute; P=0.001) in POTS patients, with a trend toward higher standing systolic BP (P=0.072). Symptom scores worsened with atomoxetine compared to placebo (+4.2 au versus −3.5 au; P=0.028) from baseline to 2 hours after study drug administration.

Conclusion

Norepinephrine reuptake inhibition with atomoxetine acutely increased standing HR and symptom burden in patients with POTS.

Clinical Trials Registration

URL: http://clinicaltrials.gov. Unique identifier: NCT00262470.

What is brain fog? An evaluation of the symptom in postural tachycardia syndrome

PURPOSE

Adolescents with postural tachycardia syndrome (POTS) often experience ill-defined cognitive impairment referred to by patients as "brain fog." The objective of this study was to evaluate the symptom of brain fog as a means of gaining further insight into its etiology and potential palliative interventions.

METHODS

Eligible subjects who reported having been diagnosed with POTS were recruited from social media web sites. Subjects were asked to complete a 38-item questionnaire designed for this study, and the Wood mental fatigue inventory (WMFI).

RESULTS

Responses were received from 138 subjects with POTS (88 % female), ranging in age from 14 to 29 years; 132 subjects reported brain fog. WMFI scores correlated with brain fog frequency and severity (P < 0.001). The top ranked descriptors of brain fog were "forgetful," "cloudy," and "difficulty focusing, thinking and communicating." The most frequently reported brain fog triggers were fatigue (91 %), lack of sleep (90 %), prolonged standing (87 %), dehydration (86 %), and feeling faint (85 %). Although aggravated by upright posture, brain fog was reported to persist after assuming a recumbent posture. The most frequently reported interventions for the treatment of brain fog were intravenous saline (77 %), stimulant medications (67 %), salt tablets (54 %), intra-muscular vitamin B-12 injections (48 %), and midodrine (45 %).

CONCLUSIONS

Descriptors for "brain fog" are most consistent with it being a cognitive complaint. Factors other than upright posture may play a role in the persistence of this symptom. Subjects reported a number of therapeutic interventions for brain fog not typically used in the treatment of POTS that may warrant further investigation.

Propranolol's effects on the consolidation and reconsolidation of long-term emotional memory in healthy participants: a meta-analysis

BACKGROUND

Considering the pivotal role of negative emotional experiences in the development and persistence of mental disorders, interfering with the consolidation/reconsolidation of such experiences would open the door to a novel treatment approach in psychiatry. We conducted a meta-analysis on the experimental evidence regarding the capacity of the ß-blocker propranolol to block the consolidation/reconsolidation of emotional memories in healthy adults.

METHODS

Selected studies consisted of randomized, double-blind experiments assessing long-term memory for emotional material in healthy adults and involved at least 1 propranolol and 1 placebo condition. We searched PsycInfo, PubMed, Web of Science, Cochrane Central, PILOTS, Google Scholar and clinicaltrials.org for eligible studies from the period 1995-2012. Ten consolidation (n = 259) and 8 reconsolidation (n = 308) experiments met the inclusion criteria. We calculated effect sizes (Hedges g) using a random effects model.

RESULTS

Compared with placebo, propranolol given before memory consolidation reduced subsequent recall for negatively valenced stories, pictures and word lists (Hedges g = 0.44, 95% confidence interval [CI] 0.14-0.74). Propranolol before reconsolidation also reduced subsequent recall for negatively valenced emotional words and the expression of cue-elicited fear responses (Hedges g = 0.56, 95% CI 0.13-1.00).

LIMITATIONS

Limitations include the moderate number of studies examining the influence of propranolol on emotional memory consolidation and reconsolidation in healthy adults and the fact that most samples consisted entirely of young adults, which may limit the ecological validity of results.

CONCLUSION

Propranolol shows promise in reducing subsequent memory for new or recalled emotional material in healthy adults. However, future studies will need to investigate whether more powerful idiosyncratic emotional memories can also be weakened and whether this weakening can bring about long-lasting symptomatic relief in clinical populations, such as patients with posttraumatic stress or other event-related disorders.

Update on the theory and management of orthostatic intolerance and related syndromes in adolescents and children

Orthostasis means standing upright. One speaks of orthostatic intolerance (OI) when signs, such as hypotension, and symptoms, such as lightheadedness, occur when upright and are relieved by recumbence. The experience of transient mild OI is part of daily life. 'Initial orthostatic hypotension' on rapid standing is a normal form of OI. However, other people experience OI that seriously interferes with quality of life. These include episodic acute OI, in the form of postural vasovagal syncope, and chronic OI, in the form of postural tachycardia syndrome. Less common is neurogenic orthostatic hypotension, which is an aspect of autonomic failure. Normal orthostatic physiology and potential mechanisms for OI are discussed, including forms of sympathetic hypofunction, forms of sympathetic hyperfunction and OI that results from regional blood volume redistribution. General and specific treatment options are proposed.

Confounders of vasovagal syncope: postural tachycardia syndrome

Most patients who present to a cardiologist with syncope have vasovagal (reflex) syncope. A busy syncope practice often also sees patients with postural tachycardia syndrome, often presenting with severe recurrent presyncope. Recognition of this syncope confounder might be difficult without adequate knowledge of their presentation, and this can adversely affect optimal management. Postural tachycardia syndrome can often be differentiated from vasovagal syncope by its hemodynamic pattern during tilt table test and differing clinical characteristics. This article reviews the presentation of postural tachycardia syndrome and its putative pathophysiology and presents an approach to nonpharmacologic and pharmacologic management.

Common syndromes of orthostatic intolerance

The autonomic nervous system, adequate blood volume, and intact skeletal and respiratory muscle pumps are essential components for rapid cardiovascular adjustments to upright posture (orthostasis). Patients lacking sufficient blood volume or having defective sympathetic adrenergic vasoconstriction develop orthostatic hypotension (OH), prohibiting effective upright activities. OH is one form of orthostatic intolerance (OI) defined by signs, such as hypotension, and symptoms, such as lightheadedness, that occur when upright and are relieved by recumbence. Mild OI is commonly experienced during intercurrent illnesses and when standing up rapidly. The latter is denoted "initial OH" and represents a normal cardiovascular adjustment to the blood volume shifts during standing. Some people experience episodic acute OI, such as postural vasovagal syncope (fainting), or chronic OI, such as postural tachycardia syndrome, which can significantly reduce quality of life. The lifetime incidence of ≥1 fainting episodes is ∼40%. For the most part, these episodes are benign and self-limited, although frequent syncope episodes can be debilitating, and injury may occur from sudden falls. In this article, mechanisms for OI having components of adrenergic hypofunction, adrenergic hyperfunction, hyperpnea, and regional blood volume redistribution are discussed. Therapeutic strategies to cope with OI are proposed.

β-Adrenergic blockade in cardiovascular disease

The development and subsequent clinical application of the β-adrenergic receptor blocking drugs represent one of the major advances in human pharmacotherapeutics. No other class of synthetic drugs has demonstrated such widespread therapeutic utility for the treatment and prevention of so many cardiovascular diseases. In addition, these drugs have proven to be molecular probes that have contributed to our understanding of the disease, and on the molecular level, both the structure and function of the 7 transmembrane G protein receptors that mediate the actions of many different hormones, neurotransmitters, and drugs. The evolution of β-blocker drug development has led to refinements in their pharmacodynamic actions that include agents with relative β1-selectivity, partial agonist activity, concomitant α-adrenergic blockers activity, and direct vasodilator activity. In addition, long-acting and ultra-short-acting formulations of β-blockers have also demonstrated a remarkable record of clinical safety in patients of all ages.

Low-dose propranolol and exercise capacity in postural tachycardia syndrome: a randomized study

OBJECTIVE

To determine the effect of low-dose propranolol on maximal exercise capacity in patients with postural tachycardia syndrome (POTS).

METHODS

We compared the effect of placebo vs a single low dose of propranolol (20 mg) on peak oxygen consumption (VO2max), an established measure of exercise capacity, in 11 patients with POTS and 7 healthy subjects in a randomized, double-blind study. Subjects exercised on a semirecumbent bicycle, with increasing intervals of resistance to maximal effort.

RESULTS

Maximal exercise capacity was similar between groups following placebo. Low-dose propranolol improved VO2max in patients with POTS (24.5 ± 0.7 placebo vs 27.6 ± 1.0 mL/min/kg propranolol; p = 0.024), but not healthy subjects. The increase in VO2max in POTS was associated with attenuated peak heart rate responses (142 ± 8 propranolol vs 165 ± 4 bpm placebo; p = 0.005) and improved stroke volume (81 ± 4 propranolol vs 67 ± 3 mL placebo; p = 0.013). In a separate cohort of POTS patients, neither high-dose propranolol (80 mg) nor metoprolol (100 mg) improved VO2max, despite similar lowering of heart rate.

CONCLUSIONS

These findings suggest that nonselective β-blockade with propranolol, when used at the low doses frequently used for treatment of POTS, may provide a modest beneficial effect to improve heart rate control and exercise capacity.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that a single low dose of propranolol (20 mg) as compared with placebo is useful in increasing maximum exercise capacity measured 1 hour after medication.

Postural tachycardia syndrome: a heterogeneous and multifactorial disorder

Postural tachycardia syndrome (POTS) is defined by a heart rate increment of 30 beats/min or more within 10 minutes of standing or head-up tilt in the absence of orthostatic hypotension; the standing heart rate is often 120 beats/min or higher. POTS manifests with symptoms of cerebral hypoperfusion and excessive sympathoexcitation. The pathophysiology of POTS is heterogeneous and includes impaired sympathetically mediated vasoconstriction, excessive sympathetic drive, volume dysregulation, and deconditioning. POTS is frequently included in the differential diagnosis of chronic unexplained symptoms, such as inappropriate sinus tachycardia, chronic fatigue, chronic dizziness, or unexplained spells in otherwise healthy young individuals. Many patients with POTS also report symptoms not attributable to orthostatic intolerance, including those of functional gastrointestinal or bladder disorders, chronic headache, fibromyalgia, and sleep disturbances. In many of these cases, cognitive and behavioral factors, somatic hypervigilance associated with anxiety, depression, and behavioral amplification contribute to symptom chronicity. The aims of evaluation in patients with POTS are to exclude cardiac causes of inappropriate tachycardia; elucidate, if possible, the most likely pathophysiologic basis of postural intolerance; assess for the presence of treatable autonomic neuropathies; exclude endocrine causes of a hyperadrenergic state; evaluate for cardiovascular deconditioning; and determine the contribution of emotional and behavioral factors to the patient's symptoms. Management of POTS includes avoidance of precipitating factors, volume expansion, physical countermaneuvers, exercise training, pharmacotherapy (fludrocortisone, midodrine, β-blockers, and/or pyridostigmine), and behavioral-cognitive therapy. A literature search of PubMed for articles published from January 1, 1990, to June 15, 2012, was performed using the following terms (or combination of terms): POTS; postural tachycardia syndrome, orthostatic; orthostatic; syncope; sympathetic; baroreceptors; vestibulosympathetic; hypovolemia; visceral pain; chronic fatigue; deconditioning; headache; Chiari malformation; Ehlers-Danlos; emotion; amygdala; insula; anterior cingulate; periaqueductal gray; fludrocortisone; midodrine; propranolol; β-adrenergic; and pyridostigmine. Studies were limited to those published in English. Other articles were identified from bibliographies of the retrieved articles.

Diagnosis and management of postural orthostatic tachycardia syndrome: A brief review

Postural orthostatic tachycardia syndrome (POTS) has been recognized since at least 1940. A review of the literature identifies differences in the definition for this condition and wide variations in treatment and outcomes. This syndrome appears to describe a group of conditions with differing pathophysiology, which requires treatment tailored to the true underlying disorder. Patients need to be fully evaluated to guide treatment. Further research is required to effectively classify the range of underlying pathophysiology that can produce this syndrome and to guide optimal management.

Gynecologic disorders and menstrual cycle lightheadedness in postural tachycardia syndrome

OBJECTIVE

To assess differences in gynecologic history and lightheadedness during menstrual cycle phases among patients with POTS and healthy control women.

METHODS

In a prospective, questionnaire-based study carried out at Paden Autonomic Dysfunction Center, Vanderbilt University, between April 2005 and January 2009, a custom-designed questionnaire was administered to patients with POTS (n=65) and healthy individuals (n=95). The results were analyzed via Fisher exact test and Mann-Whitney U test.

RESULTS

Patients with POTS reported increased lightheadedness through all phases of the menstrual cycle phases as compared with healthy controls. Both groups experienced the greatest lightheadedness during menses, and a decrease in lightheadedness during the follicular phase. Patients with POTS reported a higher incidence of gynecologic diseases as compared with healthy controls.

CONCLUSION

The severity of lightheadedness was found to vary during the menstrual cycle, which may relate to changes in estrogen levels. Patients with POTS also reported an increase in estrogen-related gynecologic disease.

Desmopressin acutely decreases tachycardia and improves symptoms in the postural tachycardia syndrome

BACKGROUND

Postural tachycardia syndrome (POTS) induces disabling chronic orthostatic intolerance with an excessive increase in heart rate on standing, and many patients with POTS have low blood volume. Increasing blood volume is a promising approach to this problem.

OBJECTIVE

To test the hypothesis that desmopressin (DDAVP) will attenuate the tachycardia and improve symptom burden in patients with POTS.

METHODS

In this protocol, patients with POTS (n = 30) underwent acute drug trials with DDAVP 0.2 mg orally and placebo, on separate mornings, in a randomized crossover design. Blood pressure, heart rate, and symptoms were assessed while seated and after standing for up to 10 minutes prior to and hourly for 4 hours following study drug.

RESULTS

The standing heart rate was significantly lower following DDAVP than placebo (101.9 ± 14.5 beats/min vs 109.2 ± 17.4 beats/min; P <.001). Standing blood pressure was not affected (P = .28). The symptom burden improved with DDAVP (from a score of 18 ± 18 arbitrary units [AU] to 13 ± 15 AU at 2 hours) compared with placebo (from 18 ± 17 AU to 19 ± 16 AU; P = .010).

CONCLUSIONS

Oral DDAVP significantly attenuated tachycardia and improved symptoms in POTS. The safety profile of this approach would need to be examined before it can be recommended for routine treatment of these patients.

Diurnal variability in orthostatic tachycardia: implications for the postural tachycardia syndrome

Patients with POTS (postural tachycardia syndrome) have excessive orthostatic tachycardia (>30 beats/min) when standing from a supine position. HR (heart rate) and BP (blood pressure) are known to exhibit diurnal variability, but the role of diurnal variability in orthostatic changes of HR and BP is not known. In the present study, we tested the hypothesis that there is diurnal variation of orthostatic HR and BP in patients with POTS and healthy controls. Patients with POTS (n=54) and healthy volunteers (n=26) were admitted to the Clinical Research Center. Supine and standing (5 min) HR and BP were obtained in the evening on the day of admission and in the following morning. Overall, standing HR was significantly higher in the morning (102±3 beats/min) than in the evening (93±2 beats/min; P<0.001). Standing HR was higher in the morning in both POTS patients (108±4 beats/min in the morning compared with 100±3 beats/min in the evening; P=0.012) and controls (89±3 beats/min in the morning compared with 80±2 beats/min in the evening; P=0.005) when analysed separately. There was no diurnal variability in orthostatic BP in POTS. A greater number of subjects met the POTS HR criterion in the morning compared with the evening (P=0.008). There was significant diurnal variability in orthostatic tachycardia, with a great orthostatic tachycardia in the morning compared with the evening in both patients with POTS and healthy subjects. Given the importance of orthostatic tachycardia in diagnosing POTS, this diurnal variability should be considered in the clinic as it may affect the diagnosis of POTS.

Circulation: Arrhythmia and Electrophysiology Editors' Picks

The following articles are being highlighted as part of Circulation: Arrhythmia and Electrophysiology's Topic Review series. This series will summarize the most important manuscripts, as selected by the editors, published in Circulation: Arrhythmia and Electrophysiology and the rest of the Circulation portfolio. The studies included in this article represent the most read manuscripts published on the topic of atrial fibrillation in 2009 and 2010.

Circulation Editors' Picks

The following articles are being highlighted as part of Circulation's Topic Review series. This series will summarize the most important manuscripts, as selected by the editors, published in Circulation and the Circulation subspecialty journals. The studies included in this article represent the most read manuscripts published on the topic of arrhythmia and electrophysiology in 2009 and 2010.

Antipsychotic pharmacotherapy and orthostatic hypotension: identification and management

Orthostatic hypotension is a common adverse effect of antipsychotics that may delay or prevent titration to a dose necessary to control psychotic symptoms. Complications of orthostatic hypotension include syncope, transient ischaemic attack, stroke, myocardial infarction and death. The risk of orthostatic hypotension associated with antipsychotic therapy is increased in patients with disorders of the autonomic nervous system, fluid imbalance and those taking concomitant drug therapy that affects haemodynamic tone. Prospective monitoring for changes in postural blood pressure is important because patients with psychotic disorders often do not articulate symptoms of orthostasis and the subjective report of dizziness does not correlate well with orthostatic blood pressure changes. Nonpharmacological strategies and patient education, most notably, slowly rising from the supine position, are crucial first steps in the prevention and treatment of both symptomatic and asymptomatic orthostatic hypotension. Pharmacological treatment is only recommended when symptomatic orthostatic hypotension persists despite proper nonpharmacological therapy and there is a compelling indication for antipsychotic treatment. Fludrocortisone is a reasonable first choice for symptomatic orthostatic hypotension. Other agents including desmopressin and midodrine may be considered in patients who do not respond favourably to a trial of fludrocortisone, but safety concerns and lack of evidence limit the utility of these agents.

Exercise training versus propranolol in the treatment of the postural orthostatic tachycardia syndrome

We have found recently that exercise training is effective in the treatment of the postural orthostatic tachycardia syndrome (POTS). Whether this nondrug treatment is superior to "standard" drug therapies, such as β-blockade, is unknown. We tested the hypothesis that exercise training but not β-blockade treatment improves symptoms, hemodynamics, and renal-adrenal responses in POTS patients. Nineteen patients (18 women and 1 man) completed a double-blind drug trial (propranolol or placebo) for 4 weeks, followed by 3 months of exercise training. Fifteen age-matched healthy individuals (14 women and 1 man) served as controls. A 2-hour standing test was performed before and after drug treatment and training. Hemodynamics, catecholamines, plasma renin activity, and aldosterone were measured supine and during 2-hour standing. We found that both propranolol and training significantly lowered standing heart rate. Standing cardiac output was lowered after propranolol treatment (P=0.01) but was minimally changed after training. The aldosterone:renin ratio during 2-hour standing remained unchanged after propranolol treatment (4.1±1.7 [SD] before versus 3.9±2.0 after; P=0.46) but modestly increased after training (5.2±2.9 versus 6.5±3.0; P=0.05). Plasma catecholamines were not affected by propranolol or training. Patient quality of life, assessed using the 36-item Short-Form Health Survey, was improved after training (physical functioning score 33±10 before versus 50±9 after; social functioning score 37±9 versus 48±6; both P<0.01) but not after propranolol treatment (34±10 versus 36±11, P=0.63; 39±7 versus 39±5, P=0.73). These results suggest that, for patients with POTS, exercise training is superior to propranolol at restoring upright hemodynamics, normalizing renal-adrenal responsiveness, and improving quality of life.

The effect of Ventricular Assist Devices on cerebral autoregulation: A preliminary study

Background

The insertion of Ventricular Assist Devices is a common strategy for cardiovascular support in patients with refractory cardiogenic shock. This study sought to determine the impact of ventricular assist devices on the dynamic relationship between arterial blood pressure and cerebral blood flow velocity.

Methods

A sample of 5 patients supported with a pulsatile ventricular assist device was compared with 5 control patients. Controls were matched for age, co-morbidities, current diagnosis and cardiac output state, to cases. Beat-to-beat recordings of mean arterial pressure and cerebral blood flow velocity, using transcranial Doppler were obtained. Transfer function analysis was performed on the lowpass filtered pressure and flow signals, to assess gain, phase and coherence of the relationship between mean arterial blood pressure and cerebral blood flow velocity. These parameters were derived from the very low frequency (0.02-0.07 Hz), low frequency (0.07-0.2 Hz) and high frequency (0.2-0.35 Hz).

Results

No significant difference was found in gain and phase values between the two groups, but the low frequency coherence was significantly higher in cases compared with controls (mean ± SD: 0.65 ± 0.16 vs 0.38 ± 0.19, P = 0.04). The two cases with highest coherence (~0.8) also had much higher spectral power in mean arterial blood pressure.

Conclusions

Pulsatile ventricular assist devices affect the coherence but not the gain or phase of the cerebral pressure-flow relationship in the low frequency range; thus whether there was any significant disruption of cerebral autoregulation mechanism was not exactly clear. The augmentation of input pressure fluctuations might contribute in part to the higher coherence observed.

Abnormalities of angiotensin regulation in postural tachycardia syndrome

BACKGROUND

Postural tachycardia syndrome (POTS) is a disorder characterized by excessive orthostatic tachycardia and significant functional disability. We previously reported that POTS patients have low blood volume and inappropriately low plasma renin activity (PRA) and aldosterone. In this study, we sought to more fully characterize the renin-angiotensin-aldosterone system (RAAS) to gain a better understanding of the pathophysiology of POTS.

OBJECTIVE

The purpose of this study was to prospectively assess the plasma levels of angiotensin (Ang) peptides and their relationship to other RAAS components in patients with POTS compared with healthy controls.

METHODS

Heart rate, PRA, Ang I, Ang II, Ang (1-7), and aldosterone were measured in POTS patients (n = 38) and healthy controls (n = 13) while they were consuming a sodium-controlled diet.

RESULTS

POTS patients had larger orthostatic increases in heart rate than did controls (52 ± 3 [mean ± SEM] bpm vs 27 ± 6 bpm, P = .001). Plasma Ang II was significantly higher in POTS patients (43 ± 3 pg/mL vs 28 ± 3 pg/mL, P = .006), whereas plasma Ang I and angiotensin 1-7 [Ang-(1-7)] were similar between groups. Despite the twofold increase of Ang II, POTS patients trended to lower PRA levels than did controls (0.9 ± 0.1 ng/mL/h vs 1.6 ± 0.5 ng/mL/h, P = .268) and lower aldosterone levels (4.6 ± 0.8 pg/mL vs 10.0 ± 3.0 pg/mL, P = .111). Estimated angiotensin-converting enzyme-2 (ACE2) activity was significantly lower in POTS patients than in controls (0.25 ± 0.02 vs 0.33 ± 0.03, P = .038).

CONCLUSION

Some patients with POTS have inappropriately high plasma Ang II levels, with low estimated ACE2 activity. We propose that these abnormalities in Ang regulation may play a key role in the pathophysiology of POTS in some patients.

The role of the cardiologist in the evaluation of dysautonomia

Dysfunction of the autonomic nervous system, or dysautonomia, is an uncommon disease. Postural orthostatic tachycardia syndrome is one of the several types of dysautonomia. Postural orthostatic tachycardia syndrome, also known as chronic orthostatic intolerance, is the most common but least severe of the dysautonomic disorders; it will serve as the model for evaluation and management of the other dysautonomias. Overall, these patients can have variable dysfunction of the autonomic nervous system that is more severe than that observed in typical neurocardiogenic syncope. Frequently, providers are not familiar with either the evaluation or the management of this syndrome, or are just not interested in doing so. This article attempts to describe strategies for evaluation and management of postural orthostatic tachycardia syndrome. The diagnosis of postural orthostatic tachycardia syndrome is made by the finding of orthostatic intolerance associated with a pulse greater than 120 beats per minute in the first 10 minutes of upright position or an elevation in pulse greater than 30 beats per minute in the first 10 minutes of upright position. Overall, these patients can have variable dysfunction of the autonomic nervous system that is more severe than that seen in typical neurocardiogenic syncope. A wide variety of associated symptoms may exist and these symptoms can have tremendous impact on the lives of the patients and their families. Management of these patients can be difficult as well as rewarding. It is helpful to perform an extensive education up front with these patients and their families. Interventions for patients with postural orthostatic tachycardia syndrome typically fall into two broad categories: non-pharmacological and pharmacological. Non-pharmacological therapies are varied, but are based primarily on ensuring adequate status of intravascular fluid. Polypharmacy may be required to control symptoms associated with postural orthostatic tachycardia syndrome. On account of the severity of their symptoms, these patients frequently have difficulty in completing their school assignments. The physician may need to help support the attempts of the family to work with the school to help the patient stay in school. As postural orthostatic tachycardia syndrome is underdiagnosed and poorly understood, it is a disease that provides an excellent opportunity to perform research. The most important studies would be those that aim to elucidate an aetiology and a pathophysiology of postural orthostatic tachycardia syndrome. In the final analysis, the role of the cardiologist in the evaluation and management of a patient with dysautonomia is to help a patient with severe disability to feel as if they are normal, or much closer to it.

Orthostatic intolerance and the headache patient

Orthostatic intolerance (OI) refers to a group of clinical conditions, including postural orthostatic tachycardia syndrome (POTS) and neurally mediated hypotension (NMH), in which symptoms worsen with upright posture and are ameliorated by recumbence. The main symptoms of chronic orthostatic intolerance syndromes include light-headedness, syncope or near syncope, blurring of vision, headaches, problems with short-term memory and concentration, fatigue, intolerance of low impact exercise, palpitations, chest pain, diaphoresis, tremulousness, dyspnea or air hunger, nausea, and vomiting. This review discusses what is known about the pathophysiology of this disorder, potential treatments, and understanding its role in the patient with chronic headache pain.