Sympathoadrenal function in patients with paroxysmal hypertension: pseudopheochromocytoma

Controversies in Hypertension VI: Paroxysmal Hypertension

Paroxysmal hypertension is characterized by a sudden and significant increase in blood pressure that may have coexisting hyperadrenergic symptoms (headache, palpitations, diaphoresis) with or without an obvious precipitating cause. Pheochromocytoma is suggested, although less than 1% of such patients have the tumor. Four syndromes should be considered, including labile hypertension, panic attacks, pseudopheochromocytoma, and baroreflex failure. Labile hypertension includes paroxysms that are provoked by obvious stress or anxiety; they may be asymptomatic or have hyperadrenergic symptoms. Similarly, panic attacks are precipitated by fear or anxiety. Pseudopheochromocytoma is characterized by paroxysms without obvious precipitating stress or anxiety, although anxiety may result from the paroxysm, and the paroxysms are invariably symptomatic; abnormal repression of emotions underlies most cases. Afferent baroreflex failure presents as symptomatic hypertensive paroxysms often precipitated by emotional or environmental stress alternating with periods of frank hypotension; orthostatic hypotension frequently coexists. No guidelines specify therapy of paroxysmal hypertension and no randomized controlled trials with hard endpoints exist for this syndrome. We discuss in detail the four pheochromocytoma mimics in the differential diagnosis of paroxysmal hypertension with recommendations on diagnosis and therapy.

Pitfalls in the Diagnostic Evaluation of Pheochromocytomas

Pheochromocytomas and paragangliomas (PPGLs), rare neuroendocrine tumors arising from chromaffin cells, present a significant diagnostic challenge due to their clinical rarity and polymorphic symptomatology. The clinical cases demonstrate the importance of an integrated approach that combines clinical assessment, biochemical testing, and imaging to distinguish PPGLs from mimicking conditions, such as obstructive sleep apnea and interfering medication effects, which can lead to false-positive biochemical results. Although a rare condition, false-negative metanephrine levels can occur in pheochromocytomas, but imaging findings can give some clues and increase suspicion for a pheochromocytoma diagnosis. This expert endocrine consult underscores the critical role of evaluating preanalytical conditions and pretest probability in the biochemical diagnosis of PPGLs. Moreover, a careful differentiation of PPGLs from similar conditions and careful selection and interpretation of diagnostic tests, with focus on understanding and reducing false positives to enhance diagnostic accuracy and patient outcomes, is crucial.

Linking the Extended Autonomic System with the Homeostat Theory: New Perspectives about Dysautonomias

Dysautonomias are conditions in which altered functions of one or more components of the autonomic nervous system (ANS) adversely affect health. This essay is about how elucidating mechanisms of dysautonomias may rationalize personalized treatments. Emphasized here are two relatively new ideas-the "extended" autonomic system (EAS) and the "homeostat" theory as applied to the pathophysiology and potential treatments of dysautonomias. The recently promulgated concept of the EAS updates Langley's ANS to include neuroendocrine, immune/inflammatory, and central components. The homeostat theory builds on Cannon's theory of homeostasis by proposing the existence of comparators (e.g., a thermostat, glucostat, carbistat, barostat) that receive information about regulated variables (e.g., core temperature, blood glucose, blood gases, delivery of blood to the brain). Homeostats sense discrepancies between the information and response algorithms. The presentation links the EAS with the homeostat theory to understand pathophysiological mechanisms of dysautonomias. Feed-forward anticipatory processes shift input-output curves and maintain plateau levels of regulated variables within different bounds of values-"allostasis". Sustained allostatic processes increase long-term wear-and-tear on effectors and organs-allostatic load. They decreaseing thresholds for destabilizing and potentially fatal positive feedback loops. The homeostat theory enables mathematical models that define stress, allostasis, and allostatic load. The present discussion applies the EAS and homeostat concepts to specific examples of pediatric, adolescent/adult, and geriatric dysautonomias-familial dysautonomia, chronic orthostatic intolerance, and Lewy body diseases. Computer modeling has the potential to take into account the complexity and dynamics of allostatic processes and may yield testable predictions about individualized treatments and outcomes.

Biochemical Assessment of Pheochromocytoma and Paraganglioma

Pheochromocytoma and paraganglioma (PPGL) require prompt consideration and efficient diagnosis and treatment to minimize associated morbidity and mortality. Once considered, appropriate biochemical testing is key to diagnosis. Advances in understanding catecholamine metabolism have clarified why measurements of the O-methylated catecholamine metabolites rather than the catecholamines themselves are important for effective diagnosis. These metabolites, normetanephrine and metanephrine, produced respectively from norepinephrine and epinephrine, can be measured in plasma or urine, with choice according to available methods or presentation of patients. For patients with signs and symptoms of catecholamine excess, either test will invariably establish the diagnosis, whereas the plasma test provides higher sensitivity than urinary metanephrines for patients screened due to an incidentaloma or genetic predisposition, particularly for small tumors or in patients with an asymptomatic presentation. Additional measurements of plasma methoxytyramine can be important for some tumors, such as paragangliomas, and for surveillance of patients at risk of metastatic disease. Avoidance of false-positive test results is best achieved by plasma measurements with appropriate reference intervals and preanalytical precautions, including sampling blood in the fully supine position. Follow-up of positive results, including optimization of preanalytics for repeat tests or whether to proceed directly to anatomic imaging or confirmatory clonidine tests, depends on the test results, which can also suggest likely size, adrenal vs extra-adrenal location, underlying biology, or even metastatic involvement of a suspected tumor. Modern biochemical testing now makes diagnosis of PPGL relatively simple. Integration of artificial intelligence into the process should make it possible to fine-tune these advances.

Pseudopheochromocytoma: an Uncommon Cause of Severe Hypertension

PURPOSE OF REVIEW

Pseudopheochromocytoma or paroxysmal hypertension is an underrecognized condition that requires a thorough investigation of secondary causes of hypertension. In this review, we aim to provide an overview of pathogenesis, clinical manifestations, biochemical evaluation, and potential therapeutic options to manage patients with pseudopheochromocytoma.

RECENT FINDINGS

The pathogenesis of this condition has not been completely elucidated but certain patients show overactivity of the sympathetic nervous system and present with elevated epinephrine and dopamine levels. Workup should include a proper evaluation of blood pressure in distinct clinical scenarios, including ambulatory blood pressure monitoring. Management should be focused on treatment of acute hypertensive episodes and prevention of paroxysms. Treatment of patients with pseudopheochromocytoma should be individualized. Psychopharmacotherapy and psychotherapeutic interventions play an important role in controlling patients' symptoms.

Blood Pressure Management in Afferent Baroreflex Failure: JACC Review Topic of the Week

Afferent baroreflex failure is most often due to damage of the carotid sinus nerve because of neck surgery or radiation. The clinical picture is characterized by extreme blood pressure lability with severe hypertensive crises, hypotensive episodes, and orthostatic hypotension, making it the most difficult form of hypertension to manage. There is little evidence-based data to guide treatment. Recommendations rely on understanding the underlying pathophysiology, relevant clinical pharmacology, and anecdotal experience. The goal of treatment should be improving quality of life rather than normalization of blood pressure, which is rarely achievable. Long-acting central sympatholytic drugs are the mainstay of treatment, used at the lowest doses that prevent the largest hypertensive surges. Short-acting clonidine should be avoided because of rebound hypertension, but can be added to control residual hypertensive episodes, often triggered by mental stress or exertion. Hypotensive episodes can be managed with countermeasures and short-acting pressor agents if necessary.

Pseudopheochromocytoma

Pseudopheochromocytoma manifests as severe, symptomatic paroxysmal hypertension without significant elevation in catecholamine and metanephrine levels and lack of evidence of tumor in the adrenal gland. The clinical manifestations are similar but not identical to those in excess circulating catecholamines. The underlying symptomatic mechanism includes augmented cardiovascular responsiveness to catecholamines alongside heightened sympathetic nervous stimulation. The psychological characteristics are probably attributed to the component of repressed emotions related to a past traumatic episode or repressive coping style. Successful management can be achieved by strong collaboration between a hypertension specialist and a psychiatrist or psychologist with expertise in cognitive-behavioral panic management.

Labile hypertension: a new disease or a variability phenomenon?

Blood pressure (BP) is a physiological parameter with short- and long-term variability caused by complex interactions between intrinsic cardiovascular (CV) mechanisms and extrinsic environmental and behavioral factors. Available evidence suggests that not only mean BP values are important, but also BP variability (BPV) might contribute to CV events. Labile hypertension (HTN) is referred to sudden rises in BP and it seems to be linked with unfavorable outcomes. The aim of this article was to review and summarize recent evidence on BPV phenomenon, unraveling the labile HTN concept along with the prognostic value of these conditions.

Reference intervals for LC-MS/MS measurements of plasma free, urinary free and urinary acid-hydrolyzed deconjugated normetanephrine, metanephrine and methoxytyramine

BACKGROUND

Plasma or urinary metanephrines are recommended for screening of pheochromocytomas and paragangliomas (PPGLs). Measurements of urinary free rather than deconjugated metanephrines and additional measurements of methoxytyramine represent other developments. For all measurements there is need for reference intervals.

METHODS

Plasma free, urinary free and urinary deconjugated O-methylated catecholamine metabolites were measured by LC-MS/MS in specimens from 590 hypertensives and normotensives. Reference intervals were optimized using data from 2,056 patients tested for PPGLs.

RESULTS

Multivariate analyses, correcting for age and body surface area, indicated higher plasma and urinary metanephrine in males than females and sex differences in urinary normetanephrine and free methoxytyramine that largely reflected body size variation. There were positive associations of age with plasma metabolites, but negative relationships with urinary free metanephrine and methoxytyramine. Plasma and urinary normetanephrine were higher in hypertensives than normotensives, but differences were small. Optimization of reference intervals using the data from patients tested for PPGLs indicated that age was the most important consideration for plasma normetanephrine and sex most practical for urinary metabolites.

CONCLUSION

This study clarifies impacts of demographic and anthropometric variables on catecholamine metabolites, verifies use of age-specific reference intervals for plasma normetanephrine and establishes sex-specific reference intervals for urinary metabolites.

Roles of catechol neurochemistry in autonomic function testing

Catechols are a class of compounds that contain adjacent hydroxyl groups on a benzene ring. Endogenous catechols in human plasma include the catecholamines norepinephrine, epinephrine (adrenaline), and dopamine; the catecholamine precursor DOPA, 3,4-dihydroxyphenylglycol (DHPG), which is the main neuronal metabolite of norepinephrine; and 3,4-dihydroxyphenylacetic acid (DOPAC), which is the main neuronal metabolite of dopamine. In the diagnostic evaluation of patients with known or suspected dysautonomias, measurement of plasma catechols is rarely diagnostic but often is informative. This review summarizes the roles of clinical catechol neurochemistry in autonomic function testing.

Pseudopheochromocytoma Associated with Domestic Assault

Pseudopheochromocytoma has a clinical presentation that is similar to pheochromocytoma. It manifests itself with paroxysmal hypertension crises, associated with various symptoms such as headaches, chest pain, nausea, palpitations, and dizziness. Patients are usually asymptomatic in between the crises. Unlike pheochromocytoma, there is no catecholamines overproduction in this pathology: hypertensive peaks are caused by a hyperactivation of the sympathetic nervous system, which is often triggered by a psychological trauma in the past. Treatment of pseudopheochromocytoma can be challenging due to normal blood pressure values in between the hypertensive peaks; it includes alpha- and beta-blockers for moderate crises and prevention and must be combined with psychopharmacologic agents such as anxiolytics or antidepressant drugs. Psychotherapy and dietetic treatment are also crucial in pseudopheochromocytoma management.

Labile and Paroxysmal Hypertension: Common Clinical Dilemmas in Need of Treatment Studies

Although "labile hypertension" is regularly encountered by clinicians, there is a paucity of information available to guide therapeutic decisions. This review discusses its clinical relevance, the limitations of current knowledge, and possible directions for future research and clinical management. Results of studies that assessed measures of blood pressure variability or reactivity are reviewed. The limited information about effects of antihypertensive drugs on blood pressure variability is discussed. Two different clinical presentations are differentiated: labile hypertension and paroxysmal hypertension. Labile hypertension remains a clinical impression without defined criteria or treatment guidance. Paroxysmal hypertension, also called pseudopheochromocytoma, presents as dramatic episodes of abrupt and severe blood pressure elevation. The disorder can be disabling. Although it regularly raises suspicion of a pheochromocytoma, such a tumor is found in <2 % of patients. The cause, which involves both emotional factors and the sympathetic nervous system, and treatment approaches, are presented.

Sympathoneural and adrenomedullary responses to mental stress

This concept-based review provides historical perspectives and updates about sympathetic noradrenergic and sympathetic adrenergic responses to mental stress. The topic of this review has incited perennial debate, because of disagreements over definitions, controversial inferences, and limited availability of relevant measurement tools. The discussion begins appropriately with Cannon's "homeostasis" and his pioneering work in the area. This is followed by mental stress as a scientific idea and the relatively new notions of allostasis and allostatic load. Experimental models of mental stress in rodents and humans are discussed, with particular attention to ethical constraints in humans. Sections follow on sympathoneural responses to mental stress, reactivity of catecholamine systems, clinical pathophysiologic states, and the cardiovascular reactivity hypothesis. Future advancement of the field will require integrative approaches and coordinated efforts between physiologists and psychologists on this interdisciplinary topic.

Catecholamine excess: pseudopheochromocytoma and beyond

Symptoms of catecholamine excess or pseudopheochromocytoma can be clinically indistinguishable from pheochromocytoma. Patients usually present with paroxysmal or episodic hypertension and have a negative evaluation for pheochromocytoma. It is important to exclude other causes of catecholamine excess that can be induced by stress, autonomic dysfunction due to baroreflex failure, medications, and drugs. Patients with pseudopheochromocytoma appear to have an amplified cardiovascular responsiveness to catecholamines with enhanced sympathetic nervous stimulation. The exact mechanism is not well understood and increased secretion of dopamine, epinephrine, and norepinephrine, and their metabolites have been identified as potentiating this clinical scenario leading to differing hemodynamic presentations depending on which catecholamine is elevated. Management of this condition is often difficult and frustrating for both the physician and the patient. Most patients respond reasonably well to medications that reduce sympathetic nervous system activity. Anxiolytics, antidepressants, and psychotherapy also play an important role in managing these patients' symptoms.

Pseudopheochromocytoma induced by anxiolytic withdrawal

Background

Symptomatic paroxysmal hypertension without significantly elevated catecholamine concentrations and with no evidence of an underlying adrenal tumor is known as pseudopheochromocytoma.

Methods

We describe the case of a female patient with paroxysmal hypertensive crises accompanied by headache, vertigo, tachycardia, nausea and altered mental status. Previously, she was treated for a longer period with alprazolam due to panic disorder. Causes of secondary hypertension were excluded. Neurological triggers (intracranial tumor, cerebral vascular lesions, hemorrhage, and epilepsy) could not be detected.

Results

Setting of the diagnosis of pseudopheochromocytoma treatment was initiated with alpha- and beta-blockers resulting in reduced frequency of symptoms. Alprazolam was restarted at a daily dose of 1 mg. The patient’s clinical condition improved rapidly and the dosage of alpha- and beta-blockers could be decreased.

Conclusions

We conclude that the withdrawal of an anxiolytic therapeutic regimen may generate sympathetic overdrive resulting in life-threatening paroxysmal malignant hypertension and secondary encephalopathy. We emphasize that pseudopheochromocytoma can be diagnosed only after exclusion of the secondary causes of hypertension. We highlight the importance of a psychopharmacological approach to this clinical entity.

Determination of catecholamines in plasma and urine

For more than 20 years, measurement of catecholamines in plasma and urine in clinical chemistry laboratories has been the cornerstone of the diagnosis of neuroendocrine tumors deriving from the neural crest such as pheochromocytoma (PHEO) and neuroblastoma (NB), and is still used to assess sympathetic stress function in man and animals. Although assay of catecholamines in urine are still considered the biochemical standard for the diagnosis of NB, they have been progressively abandoned for excluding/confirming PHEOs to the advantage of metanephrines (MNs). Nevertheless, catecholamine determinations are still of interest to improve the biochemical diagnosis of PHEO in difficult cases that usually require a clonidine-suppression test, or to establish whether a patient with PHEO secretes high concentrations of catecholamines in addition to metanephrines. The aim of this chapter is to provide an update about the catecholamine assays in plasma and urine and to show the most common pre-analytical and analytical pitfalls associated with their determination.

The clinical spectrum of labile hypertension: a management dilemma

J Clin Hypertens (Greenwich). 2009;11:491-497. (c)2009 Wiley Periodicals, Inc.Although the management of the labile component of blood pressure elevation is a problem often encountered by clinicians, there is a paucity of information available to guide therapeutic decisions. This review discusses the clinical relevance of blood pressure lability, the limitations of current knowledge, and possible directions for future research and clinical management.

Depression masked as paroxysmal hypertension episodes

This paper describes a clinical picture frequently seen in specialty hypertension clinics, a patient with paroxysmal or intermittent hypertension not related to pheochromocytoma. A variety of diagnostic labels given to these patients is reviewed, including pseudopheochromocytoma and panic attacks. The clinical features, pathophysiology, diagnosis and treatment of these syndromes are outlined. It is proposed that successful management of these patients may be best achieved by collaborative care between a hypertension specialist and a psychiatrist, or clinical psychologist with expertise in cognitive-behavioral panic disorder management, stress-reduction techniques including controlled breathing, and effective treatment of anxiety. The use of drugs effective for treatment of panic disorder can also be helpful in managing those patients.

Generalized and neurotransmitter-selective noradrenergic denervation in Parkinson's disease with orthostatic hypotension

Patients with Parkinson's disease (PD) often have manifestations of autonomic failure. About 40% have neurogenic orthostatic hypotension (NOH), and among PD+NOH patients virtually all have evidence of cardiac sympathetic denervation; however, whether PD+NOH entails extra-cardiac noradrenergic denervation has been less clear. Microdialysate concentrations of the main neuronal metabolite of norepinephrine (NE) and dihydroxyphenylglycol (DHPG) were measured in skeletal muscle, and plasma concentrations of NE and DHPG were measured in response to i.v. tyramine, yohimbine, and isoproterenol, in patients with PD+NOH, patients with pure autonomic failure (PAF), which is characterized by generalized catecholaminergic denervation, and control subjects. Microdialysate DHPG concentrations were similarly low in PD+NOH and PAF compared to control subjects (163 +/- 25, 153 +/- 27, and 304 +/- 27 pg/mL, P < 0.01 each vs. control). The two groups also had similarly small plasma DHPG responses to tyramine (71 +/- 58 and 82 +/- 105 vs. 313 +/- 94 pg/mL; P < 0.01 each vs. control) and NE responses to yohimbine (223 +/- 37 and 61 +/- 15 vs. 672 +/- 130 pg/mL, P < 0.01 each vs. control), and virtually absent NE responses to isoproterenol (20 +/- 34 and 14 +/- 15 vs. 336 +/- 78 pg/mL, P < 0.01 each vs. control). Patients with PD+NOH had normal bradycardia responses to edrophonium and normal epinephrine responses to glucagon. The results support the concept of generalized noradrenergic denervation in PD+NOH, with similar severity to that seen in PAF. In contrast, the parasympathetic cholinergic and adrenomedullary hormonal components of the autonomic nervous system seem intact in PD+NOH.

Endocrine causes of secondary hypertension

Secondary hypertension is common in clinical practice if a broad definition is applied. Various patterns of hypertension exist in the patient with an endocrine source of their disease, including new-onset hypertension in a previously normotensive individual, a loss of blood pressure control in a patient with previously well-controlled blood pressure, and/or labile blood pressure in the setting of either of these 2 patterns. A thorough history and physical exam, which can rule out concomitant medications, alcohol intake, and over-the-counter medication use, is an important prerequisite to the workup for endocrine causes of hypertension. Endocrine forms of secondary hypertension, such as pheochromocytoma and Cushing's disease, are extremely uncommon. Conversely, primary aldosteronism now occurs with sufficient frequency so as to be considered "top of the list" for secondary endocrine causes in otherwise difficult-to-treat or resistant hypertension. Primary aldosteronism can be insidious in its presentation since a supposed hallmark finding, hypokalemia, may be variable in its presentation. It is important to identify secondary causes of hypertension that are endocrine in nature because surgical intervention may result in correction or substantial improvement of the hypertension.

Neuronal source of plasma dopamine

BACKGROUND

Determinants of plasma norepinephrine (NE) and epinephrine concentrations are well known; those of the third endogenous catecholamine, dopamine (DA), remain poorly understood. We tested in humans whether DA enters the plasma after corelease with NE during exocytosis from sympathetic noradrenergic nerves.

METHODS

We reviewed plasma catecholamine data from patients referred for autonomic testing and control subjects under the following experimental conditions: during supine rest and in response to orthostasis; intravenous yohimbine (YOH), isoproterenol (ISO), or glucagon (GLU), which augment exocytotic release of NE from sympathetic nerves; intravenous trimethaphan (TRI) or pentolinium (PEN), which decrease exocytotic NE release; or intravenous tyramine (TYR), which releases NE by nonexocytotic means. We included groups of patients with pure autonomic failure (PAF), bilateral thoracic sympathectomies (SNS-x), or multiple system atrophy (MSA), since PAF and SNS-x are associated with noradrenergic denervation and MSA is not.

RESULTS

Orthostasis, YOH, ISO, and TYR increased and TRI/PEN decreased plasma DA concentrations. Individual values for changes in plasma DA concentrations correlated positively with changes in NE in response to orthostasis (r = 0.72, P < 0.0001), YOH (r = 0.75, P < 0.0001), ISO (r = 0.71, P < 0.0001), GLU (r = 0.47, P = 0.01), and TYR (r = 0.67, P < 0.0001). PAF and SNS-x patients had low plasma DA concentrations. We estimated that DA constitutes 2%-4% of the catecholamine released by exocytosis from sympathetic nerves and that 50%-90% of plasma DA has a sympathoneural source.

CONCLUSIONS

Plasma DA is derived substantially from sympathetic noradrenergic nerves.