Kevin McNeeley

Hypotension Unawareness in Profound Orthostatic Hypotension

BACKGROUND Clinicians depend on history given by the patients when considering the diagnosis of orthostatic hypotension. METHODS Patients with a decrease in systolic blood pressure more than 60 mm Hg from baseline during a head-up tilt table test were included. They were classified according to their symptoms during the head-up tilt table test. Localization of the cause of orthostatic hypotension was sought in each of these groups. RESULTS Eighty-eight (43%) patients had typical symptoms, 49 (24%) had atypical symptoms, and 68 (33%) were asymptomatic. The average decrease in systolic blood pressure was 88 mm Hg, 87.5 mm Hg, and 89.8 mm Hg in the typical, atypical, and asymptomatic groups, respectively (P=.81). Patients reported severe dizziness with a similar frequency as lower extremity discomfort. Backache and headache also were common atypical complaints. Patients with peripheral cause of dysautonomia were able to sustain the longest upright position during the head-up tilt table test (21 minutes, compared with central dysautonomia [15 minutes]) (P=.005). There was no correlation between the cause of dysautonomia and the occurrence of symptoms during the head-up tilt table test (P=.58). CONCLUSION A third of the patients with severe orthostatic hypotension are completely asymptomatic during the head-up tilt table test, and another quarter have atypical complaints that would not lead physicians toward the diagnosis of orthostatic hypotension. These findings suggest that they might not provide adequate information in diagnosing profound orthostatic hypotension in a subset of patients with this disorder.

Orthostatic Syndromes Differ in Syncope Frequency

BACKGROUND There are conflicting opinions on whether postural tachycardia syndrome predisposes to syncope. We investigated this relationship by comparing the frequency of syncope in postural tachycardia syndrome and orthostatic hypotension. METHODS We queried our autonomic laboratory database of 3700 patients. Orthostatic hypotension and postural tachycardia syndrome were defined in standard fashion, except that postural tachycardia syndrome required the presence of orthostatic symptoms and a further increase in heart rate beyond 10 minutes. Syncope was defined as an abrupt decrease in blood pressure and often, heart rate, requiring termination of the tilt study. Statistical analysis utilized Fishers exact test and Students t test, as appropriate. RESULTS Of 810 patients referred for postural tachycardia syndrome, 185 met criteria while another 328 patients had orthostatic hypotension. Of the postural tachycardia syndrome patients, 38% had syncope on head-up tilt, compared with only 22% of those with orthostatic hypotension (P<.0001). In the postural tachycardia group, syncope on head-up tilt was associated with a clinical history of syncope in 90%, whereas absence of syncope on head-up tilt was associated with a clinical history of syncope in 30% (P<.0001). In contrast, syncope on head-up tilt did not bear any relationship to clinical history of syncope in the orthostatic hypotension group (41% vs 36%; P=.49). CONCLUSION Our results demonstrate that syncope (both tilt table and clinical) occurs far more commonly in patients who have postural tachycardia syndrome than in patients with orthostatic hypotension. These findings suggest that one should be clinically aware of the high risk of syncope in patients with postural tachycardia syndrome, and the low-pressure baroreceptor system that is implicated in postural tachycardia syndrome might confer more sensitivity to syncope than the high pressure system implicated in orthostatic hypotension.

A Comparison of Dysautonomias Comorbid with Cyclic Vomiting Syndrome and with Migraine

Cyclic vomiting syndrome (CVS) shares many features with migraine headache, including auras, photophobia, and antimigrainous treatment response being traditionally viewed as a migraine variant. Aims. To determine whether CVS is associated with the same disorders as migraine headache, and compare these associations to those in healthy control subjects. Methods. Cross-sectional study of patients utilizing the ODYSA instrument, evaluating the probability of 12 functional/autonomic diagnoses, CVS, migraine, orthostatic intolerance (OI), reflex syncope, interstitial cystitis, Raynauds syndrome, complex regional pain syndrome (CRPS), irritable bowel syndrome, functional dyspepsia, functional abdominal pain, fibromyalgia, and chronic fatigue syndrome. Control subjects were age-matched gender-matched friends. Patients had to fulfill criteria for CVS or migraine, while control subjects could not. Results. 103 subjects were studied, 21 with CVS, 46 with migraine and 36 healthy controls. CVS and migraine did not differ in the relative frequencies of fibromyalgia, OI, syncope, and functional dyspepsia. However, CVS patients did demonstrate a significantly elevated frequency of CRPS. Conclusions. Although CVS and migraine clearly share many of the same comorbidities, they do differ in one important association, suggesting that they may not be identical in pathophysiology. Since OI is common in CVS, treatment strategies could also target this abnormality.

Postural tachycardia syndrome with asystole on head-up tilt

Enhanced sympathetic activity causes an exaggerated heart rate response to standing in the postural tachycardia syndrome (POTS). All patients describe symptoms of orthostatic intolerance such as dizziness, blurred vision, shortness of breath, palpitations, tremulousness, chest discomfort, headache, lightheadedness and nausea, but only one third suffer loss of consciousness. We report four patients with POTS, who had long ventricular pauses (i.e. asystole) and syncope during head-up tilt test. This suggests that a subset of patients with POTS can have a surge in parasympathetic outflow that precedes vasovagal syncope.

Evaluation of a brief cardiovascular autonomic screen

OBJECTIVE To test the validity and practicality of a simple, rapid autonomic cardiovascular evaluation (RACE). INTRODUCTION Assessment of the autonomic nervous system is costly and time consuming. Consequently, briefer measures are often utilized as evaluations of autonomic function. We therefore set out to assess the validity and practicality of a simple, rapid autonomic cardiovascular evaluation protocol which mimicked the bedside evaluations used in many healthcare centers. DESIGN/METHODS Every eligible patient undergoing full autonomic testing (FAT) in our laboratory was enrolled. The protocol, performed blinded to FAT results, consisted of one breath in the supine position, and supine and standing (1 and 3 min) pressures and pulse. Results were scored for cardiac variation during the breath, a drop in pressure during the stand. Pulse increase was also scored. Aggregate RACE score was regressed against a similarly scored FAT. RESULTS The single breath response correlated poorly with the standard response to deep breathing with convergent results in only 26/37 patients, with a specificity of 30%, and sensitivity of 85%. HR and BP changes standing showed little regression against matching values during FAT. Only 5/11 patients who met the criteria for postural tachycardia syndrome by FAT demonstrated a >20 bpm increase in HR by 3 min standing. Finally, aggregate scores for FAT and RACE correlated poorly. DISCUSSION The RACE does not satisfy the criteria to serve as a robust dysautonomia screen. Full autonomic testing provides more complete and accurate information than simple bedside assessment.

Achalasia as the harbinger of a novel mitochondrial disorder in childhood

Department of Pediatric Gastroenterology and Nutrition, Rainbow Babies and Children’s Hospital, Autonomic Laboratory, University Hospitals of Cleveland, Cleveland, Ohio; Department of Neurology, Columbia University College of Physicians and Surgeons, New York, New York; Center for Human Genetics, Department of Pathology, Department of Neurology & Autonomic Laboratory, University Hospitals of Cleveland and Case Western Reserve University, Cleveland, Ohio

The clinical thermoregulatory sweat test induces maximal sweating.

Although thermoregulatory sweat testing is commonly used to assess the autonomic nervous system, the power of this stimulus to induce sweating has not been studied. In 8 healthy male subjects, the authors quantitated sweat rates, core temperature, heart rate, and blood pressure during clinical thermoregulatory sweat testing, a separate exercise protocol, and with exercise added to thermal conditions. The authors found that (1) the addition of exercise to the thermal environment produced no further increase in sweat rate (3,841±948 versus 3,888±866 nl/mn-cm2); (2) maximum sweat rates closely corresponded to the theoretical maximum (6,000 nl/mn-cm2) derived from single gland studies; (3) sweat rates vary across subjects, but are similar across sites in any one individual; (4) core temperature rise is a major determinant of cardiovascular load in both thermal and exercise settings; (5) blood pressure decreased 28/11 mm Hg during thermal load, but increased 26/10 mm Hg with exercise, in agreement with current understanding of muscle and skin vascular physiology. The authors conclude that clinical thermoregulatory testing conditions produce maximum sweat rates in humans.

Implications of tilt-table induced faint time in patients with reflex syncope

OBJECTIVE The aim of this study was to determine whether patients who faint earlier in the course of a tilt table study represent a separate population with a poorer prognosis or different pathophysiology. We analyzed differences across patients with different syncopal times on the tilt-table study to answer this question. METHODS This was a retrospective, approved, chart review. From our database of over 6000 patients, we identified 1222 patients with syncope. After excluding patients with orthostatic hypotension, postural tachycardia syndrome and diabetes, we were left with 131 patients with pure reflex syncope. We divided fainters into an early (<20 minutes) and late (>20 minutes) faint times. Along with the tilt table test all patients underwent heart rate response for deep breathing, Valsalva maneuver and quantitative sudomotor axon reflex tests. RESULTS By 10 minutes in the tilt study, only 18% of subjects had fainted, 65% by 20 minutes, 92% by 30 minutes and 96% by 35 minutes. Age was evenly distributed across all syncopal times. Neither the 14 abnormal cardiac responses to deep breathing nor the 20 abnormal Valsalva maneuvers, nor the 28 abnormal axon reflex responses clustered with an early or late faint time. CONCLUSION A 10-minute tilt will miss 82% of syncopal episodes, while a 30- minute tilt increases the yield 10-fold, missing only 8%. Patients with early faint times did not differ from patients with late fainting times with regard to age or autonomic test abnormalities. Timing of syncope during the tilt table test does not associated with more severe dysautonomia. A prospective study is needed to confirm these observations.

Lower body negative pressure: A test of cardiovascular autonomic function

Lower body negative pressure (LBNP) may provide an alternative test of cardiovascular autonomic function for patients unable to perform the Valsalva maneuver (VM). LBNP at −40 mmHg for 30 s was compared to the VM at 40 mmHg for 15 s with heart rate and blood pressure measured continuously in three age groups: 10–25 years; 26–40 years; and 41–55 years. Heart rate and blood pressure responses were comparable, with moderately diminished changes in blood pressure and heart rate in the LBNP test. When heart response to LBNP was converted to a ratio similar to that calculated for the VM, a high degree of correlation was found (R2 = 0.5711). The LBNP test shows promise as an alternative test of cardiovascular autonomic function based on studies in normal subjects. The less marked changes may relate to the more passive nature of the applied stress. Future work should improve the devices accessibility and establish values for patients with autonomic disorders.