The head-up tilt testing is widely used in diagnosis of orthostatic intolerance. The tilting provokes blood pooling in the splanchnic and the lower extremity circulation which triggers the neural and humoral compensatory mechanisms aiming to maintain stable blood pressure and cerebral perfusion. The tilt test assesses the integrity of parasympathetic and sympathetic innervation [
Common orthostatic symptoms are usually defined by heart rate and blood pressure responses to tilting. The orthostatic cerebral blood flow is less studied; even many orthostatic symptoms are due to orthostatic cerebral hypoperfusion [
This retrospective, single-center study included patients with history of autonomic function testing at the University of Massachusetts Medical School, Autonomic Laboratory, between years 2007 and 2014. Patients were referred for evaluation of two types of orthostatic complaints. The first group constitutes orthostatic intolerance symptoms which include dizziness, lightheadedness, unexplained falls, chronic fatigue, heaviness, chest pain, and shortness of breath. The second group includes patients with history of unexplained loss of consciousness that were referred for evaluation of suspected syncope.
The details of our standardized testing protocol have been published previously [
Heart rate was calculated from ECG. Arterial blood pressure was measured in the upper arm intermittently using an automated noninvasive oscillometric device Dinamap ProCare Monitor 100 (GE, Fairfield, CT), as well as continuously by infrared finger plethysmography (Finapress Medical Systems, Amsterdam, Netherlands). Nasal thermistor and end tidal CO2 (Capstar-100, CWE, Inc., Ardmore, PA) were used for monitoring respiratory parameters. CBFv was monitored using transcranial Doppler (MultiDop T, DWL, Singen, Germany) with a 2 MHz probe. CBFv was obtained from the left middle cerebral artery with the Doppler probe attached to a three-dimensional positioner which kept the probe at a constant depth and angle of insonation.
The tilt responses were classified as described below.
Normally heart rate increases at least 10 beats per minute (BPM) but less than 30 BMP during the tilt (Table
Criteria for the orthostatic syndromes.
Disorder/syndrome | Criteria | Comments |
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Normal response to tilt | QASAT |
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Orthostatic hypotension (OH), compensated, with stable orthostatic CBFv | QASAT |
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OH, uncompensated, with reduced orthostatic CBFv | QASAT |
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Orthostatic cerebral hypoperfusion syndrome (OCHOs) | QASAT |
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Orthostatic hypertension syndrome (OHTN) | QASAT |
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Postural tachycardia syndrome (POTS) | QASAT |
If the maximal heart rate does not cross 120 BMP, it is called mild orthostatic intolerance |
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Inappropriate sinus tachycardia (IST) | QASAT |
Grading is based on maximal heart rate |
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Paroxysmal sinus tachycardia (PST) | QASAT |
PST usually affects the first 2 minutes of the tilt but not always. If, for example, the tachycardia with the 30 BPM increment occurs at minutes 9 and 10 of the tilt (the tachycardia duration = 2 minutes), then it is recommended to continue the tilt to clarify the diagnosis. If the tachycardia continues it is the POTS; if not it is PST |
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Syncope, cardiovagal | HR < 40 BPM AND |
All variables are obtained during the syncope |
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Syncope, vasodepressor | HR ≥ before syncope AND |
All variables are obtained during the syncope |
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Syncope, mixed | HR > 40 BPM AND |
All variables are obtained during the syncope |
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Primary cerebral autoregulatory failure | QASAT |
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Psychogenic pseudosyncope | QASAT |
Typically patient is unresponsive, atonic, although bizarre posturing can be observed, without abnormal movement that can be seen in seizures |
Comments: QASAT = Quantitative Scale for Grading of Cardiovascular Autonomic Reflex Tests and Small Fibers from Skin Biopsies, details of calculations can be found in Novak, 2015 [
POTS is defined by the presence of orthostatic symptoms associated with an increment of heart rate by ≥30 BPM held for more than 30 seconds when changing position from supine to upright in the absence of orthostatic hypotension [
Historically, OH is defined as a drop ≥20 mmHg in systolic blood pressure or ≥10 mmHg in diastolic blood pressure within three minutes of standing or head-up tilt. This definition does not take into account the baseline value; therefore a modified definition was that using a relative drop of 80% and 85% in systolic and mean blood pressure, respectively, where supine baseline is 100% [
OHTN is a common syndrome with a prevalence of 1.1% [
Syncope is defined as a transient loss of consciousness due to global cerebral hypoperfusion [
In psychogenic syncope, also termed psychogenic pseudosyncope, consciousness is only apparently lost and global cerebral hypoperfusion is absent [
PST can be frequently encountered during the tilt test and may be due to underlying anxiety disorder. Paroxysmal PST in this study was defined as intermittent (duration < 2 minutes) tachycardia (heart rate > 100 bpm [
IST is associated with persistent or recurrent elevated heart rate (>100 BMP) at rest including supine and excessive or inappropriate heart rate increment in upright position [
OCHOs is a recently described syndrome associated with reduced orthostatic cerebral blood flow velocity (CBFv) without OH, bradycardia, and excessive tachycardia [
This is a new syndrome defined in this paper. PCAF is characterized by abnormally low supine CBFv without supine hypotension. The normal supine CBFv is age and gender dependent and pCAF is defined as CBFv less than the lower limit of the normal range where the normal limit is 72.09–0.38
Vasomotor oscillations are periodic fluctuations of blood pressure.
Blood pressure acquired by finger plethysmographic device is not always accurate [
The syndromes described above were detected automatically by an algorithm written in Matlab programming language (MathWorks, Natick, MA). The software used in this study is an extension of the Quantitative Scale for Grading of Cardiovascular Autonomic Reflex Tests and Small Fibers from Skin Biopsies (QASAT) [
The clinical variables associated with orthostatic syndromes were compared with normal responses using Wilcoxon rank test since most of the data had nonnormal distribution. Nine clinical syndromes were compared with the normal response to the tilt, for example, OH, OCHOs, OHTN, POTS, IST, PST, syncope, psychogenic syncope, and pCAF, and therefore the initial significance 0.05 was adjusted by Bonferroni correction to 0.005 (0.05/10 comparisons). All statistical analyses were performed using JMP 12.0 (Cary, NC) statistical software.
Data from 744 patients were analyzed. All patients had unrevealing standardized evaluation including medical history, neurological examination, basic metabolic panel, 12-lead ECG, imaging studies (CT or MRI of the brain), and EEG if patients were referred for evaluation of syncope.
669 patients were referred for evaluation of orthostatic symptoms including dizziness and 75 patients were referred for evaluation of unexplained loss of consciousness with a suspected diagnosis of syncope.
The tilt test was normal in 102 subjects (Table
Main clinical variables associated with orthostatic syndromes.
Diagnosis | New Dg | Age |
OST | ROS | Baseline | Tilt | Comments |
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Normal |
0 |
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32 | 14 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (2), palpitations (3), presyncope (patient believes is going to faint) 0, sense of weakness (3), shortness of breath (1), chest pain (0), excessive sweating (1), fatigue (4). 12 patients experienced dizziness associated with movement of the tilt table that resolved after the tilt table did reach the upright position. |
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OH-c |
34 |
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12 | 10 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (0), palpitations (0), presyncope (patient believes is going to faint) 0, sense of weakness (3), shortness of breath (3), chest pain (2), excessive sweating (1), fatigue (11). |
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OH-u |
24 |
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51 | 51 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (50), palpitations (33), presyncope (patient believes is going to faint) 37, sense of weakness (41), shortness of breath (14), chest pain (6), excessive sweating (33), fatigue (48). |
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OCHOs |
97 |
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97 | 95 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (93), palpitations (12), presyncope (patient believes is going to faint) 44, sense of weakness (34), shortness of breath (6), chest pain (9), excessive sweating (22), fatigue (67). |
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OHTN |
14 |
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13 | 13 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (4), palpitations (0), presyncope (patient believes is going to faint) 4, sense of weakness (10), shortness of breath (4), chest pain (3), excessive sweating (1), fatigue (12). |
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POTS |
67 |
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100 | 100 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (82), palpitations (80), presyncope (patient believes is going to faint) 62, sense of weakness (72), shortness of breath (30), chest pain (31), excessive sweating (18), fatigue (34). HR during the tilt is the average of maximal values of each subject. |
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IST |
24 |
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24 | 24 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (21), palpitations (24), presyncope (patient believes is going to faint) 12, sense of weakness (15), shortness of breath (18), chest pain (9), excessive sweating (8), fatigue (18). |
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PST |
12 |
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12 | 12 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (3), palpitations (12), presyncope (patient believes is going to faint) 2, sense of weakness (5), shortness of breath (7), chest pain (1), excessive sweating (2), fatigue (10). HR during the tilt is the average of maximal values of each subject. |
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Syncope-cardioinhibitory |
3 |
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4 | 3 |
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Loss of consciousness (4), additional orthostatic symptoms during the tilt test: dizziness or lightheadedness (3), palpitations (0), presyncope (patient believes is going to faint) 4, sense of weakness (3), shortness of breath (4), chest pain (0), excessive sweating (2), fatigue (1). Tilt vitals obtained during syncope. |
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Syncope-vasodepressor |
11 |
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12 | 2 |
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Loss of consciousness (12); additional orthostatic symptoms during the tilt test: dizziness or lightheadedness (11), palpitations (7), presyncope (patient believes is going to faint) 8, sense of weakness (8), shortness of breath (9), chest pain (1), excessive sweating (7), fatigue (4). Tilt vitals obtained during syncope. |
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Syncope-mixed |
10 |
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26 | 12 |
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Loss of consciousness (26); additional orthostatic symptoms during the tilt test: loss of consciousness (22), dizziness or lightheadedness (21), palpitations (14), presyncope (patient believes is going to faint) 22, sense of weakness (25), shortness of breath (17), chest pain (2), excessive sweating (21), fatigue (19). Tilt vitals obtained during syncope. |
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pCAF |
67 |
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22 | 22 |
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Orthostatic symptoms during the tilt test: dizziness or lightheadedness (61), palpitations (10), presyncope (patient believes is going to faint) 33, sense of weakness (45), shortness of breath (17), chest pain (12), excessive sweating (21), fatigue (50). All patients had also prominent nonpositional symptoms including chronic fatigue (33), weakness (32), forgetfulness (45), and attention deficit (54). |
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Psychogenic pseudosyncope |
3 |
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8 | 8 |
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Loss of consciousness (8); additional orthostatic symptoms during the tilt test: dizziness or lightheadedness (6), palpitations (4), presyncope (patient believes is going to faint) 2, sense of weakness (4), shortness of breath (5), chest pain (1), excessive sweating (2), fatigue (5), eye flutter (4), moaning (4), bizarre posturing (4). Tilt vitals obtained during pseudosyncope. |
Comments: diagnosis = diagnosis obtained during the tilt test; new Dg = diagnosis obtained from the tilt test that is different from the referral diagnosis or it is not documented in the chart (e.g., if the patient was referred for evaluation of orthostatic hypotension and the tilt test showed POTS);
From 669 patients evaluated for orthostatic intolerance (not syncope), the tilt test was normal in 77 patients. From 75 patients referred for evaluation of syncope, the tilt test showed normal response in 25 subjects, neutrally mediated syncope in 33 patients, and abnormal results but nonsyncope pattern in remaining patients (Table
Table
Figures
Comparisons of normal responses to the tilt (control), orthostatic hypotension (OH), and orthostatic cerebral hypoperfusion syndrome (OCHOs). Normal heart rate increment (≥10 and <30 BPM) is seen in all examples. Orthostatic blood pressure is stable in a healthy control subject and OCHOs while it is reduced in OH. Orthostatic cerebral blood flow velocity is stable in a control subject and reduced in OH and OCHOs. CBFv can be normal or reduced in OH, depending on functioning of cerebral autoregulation and severity of OH. Green boxes represent mean blood pressure obtained from the upper arm. HR = heart rate, BP = blood pressure, and CBFv = cerebral blood flow velocity.
Comparisons of tachycardia syndromes including postural tachycardia syndrome (POTS), inappropriate sinus tachycardia (IST), and paroxysmal sinus tachycardia (PST). During supine position, the heart rate is normal (<100) in POTS, consistently elevated in IST, and transiently elevated in PST. The excessive tachycardia during the tilt is seen in all shown syndromes, being continuous in POTS and IST, and intermittent in PST. Blood pressure is stable in all examples. CBFv is reduced in POTS, normal in IST, and intermittently elevated in PST.
Comparisons of three main types of neurally mediated syncope. Syncope is associated with profound decline in BP and in diastolic CBFv. HR and BP responses differentiate each type of syncope while CBFv responses are similar among all syncope types. HR declines before BP in cardiovagal syncope. HR decline is absent in the vasodepressor syncope. HR and BP decline simultaneously in mixed syncope. CBFv shows typical vasodilation pattern in all types of syncope that is characterized by a decline in diastolic and increase in systolic CBFv. The diastolic CBFv is equal or close to zero during syncope.
Orthostatic hypotension with stable orthostatic CBFv. There is immediate decline in BP at the onset of tilt and the decline further progressed towards the end of the tilt. The HR increment was normal and CBFv was stable during the tilt. Note details of signals in (b) and (c). Data from 60-year-old man.
Transient orthostatic hypotension. This example shows a progressive decline in BP during the first 5 minutes of the tilt followed by the recovery of BP towards the end of the tilt. CBFv was normal and stable during the tilt. Data from 42-year-old woman.
Orthostatic hypotension with reduced orthostatic CBFv. (a) shows the drop of BP (1. drop) at the beginning of the tilt with a recovery (recovery) followed by a further decline in BP at the second half of the tilt (2. drop). The HR increment was preserved during the tilt. CBFv was progressively declining during the tilt. Patient was very dizzy and anxious and she requested to terminate the tilt at the 6th minute. (b) shows data from the same person a year later. The second tilt test was remarkably similar to the first one showing orthostatic hypotension with similar recovery and final decline of the blood pressure. CBFv was reduced throughout the tilt. Data from 26-year-old woman.
This example shows combination of (1) primary cerebral autoregulatory failure (pCAF); (2) severe orthostatic hypotension with reduced orthostatic CBFv; and (3) atrial fibrillation. Supine BP is elevated while supine CBFv is reduced. The pattern of elevated BP and reduced CBFv during supine position is due to abnormal cerebral vasoconstriction consistent with pCAF. There was severe OH with a progressive decrease in BP during the tilt. Diastolic CBFv was reduced during the tilt but less than systolic CBFv that can be seen in mild cerebral vasodilatation that compensates for reduced orthostatic BP. HR responses to the tilt were absent. Note random, noise-like pattern of HR due atrial fibrillation. The HR fluctuated wildly (50–180 BPM) and not all electrical systoles were transmitted in the mechanical systoles (c) resulting in marked variations of BP and CBFv. Supine hypertension and orthostatic hypotension are a marker of severe autonomic adrenergic failure. Green boxes represent mean blood pressure obtained from the arm. Data from 69-year-old man with multiple system atrophy.
Mixed syncope. In this subject, initial slowing of HR from 123 to 81 BPM (thin red arrow) is not cardioinhibitory response but reflects a functioning baroreflex since it is associated with elevation of BP (thin black arrow) and CBFv (thin blue arrow). The onset of the cardioinhibitory reaction is marked by the vertical red line with HR 108 BPM (thick red arrow) and coincides with a BP drop (thick black arrow) and patient became quickly unconscious. The pulsatility index increased during syncope (systolic CBFv increased and diastolic CFBv decreased) which is consistent with cerebral vasodilatation. The vasodilatation started early (thick blue arrows), and the changes were discernible in the doppler audio signal before noticeable changes in heart rate or BP. The cardiac slowing followed with delayed BP decrease being characteristic of cardioinhibitory syncope. Patient lost consciousness when the systolic BP declined below 60 mmHg, as expected. Data from 20 y/o woman.
Vasodepressor syncope. There is a progressive drop in BP without bradycardia till syncope occurred. HR started to slow down only after a subject was tilted back to supine position. The syncope is associated with a characteristic cerebral vasodilatation pattern. Data from 27-year-old woman.
Cerebral vasodilation during syncope. The cerebral vascular resistance is reduced during syncope which is consistent with cerebral vasodilation. The same subject as in Figure
Cardioinhibitory syncope. In this subject, slowing of HR, BP drop, and cerebral vasodilation began almost simultaneously (marked by blue line) and progressed rapidly into asystole of 27 seconds. Note the vasodilatory pattern in CBFv early in the evolution of syncope (blue arrows) followed by reactive hyperemia (green circle) with elevated systolic and diastolic CBFv. Data from 39-year-old man.
Orthostatic cerebral hypoperfusion syndrome (OCHOs). The tilt provoked a progressive increase in BP that was seen in both finger (black trace) and arm (green boxes) BP. The finger systolic BP exceeded the upper range of our device, 205 mmHg. The CBFv was progressively declining during the tilt that was consistent with cerebral vasoconstriction. Patient was very dizzy and agitated during the tilt. Data from 66-year-old woman.
Orthostatic hypertension syndrome. BP was elevated during the tilt while CBFv was stable. HR responses were normal during the tilt. Note increased cerebral vascular resistance (CRV) that is consistent with cerebral vasoconstriction. Data from 39-year-old man.
Primary cerebral autoregulatory failure (pCAF, (b)). HR and BP were normal at supine and during the tilt. CBFv was markedly reduced at the supine position and was further reduced during the tilt. Data from 47-year-old man. Patient was referred for evaluation of chronic fatigue, difficulites with attention, and chronic dizziness that was both supine and postural. For comparison, a healthy 80-year-old woman has normal CBFv (a).
Inappropriate sinus tachycardia (IST). Note elevated resting heart rate (>100 BMP) which is further increased during the tilt. This response satisfies criteria for POTS (last baseline HR = 101.3, last HR during the tilt = 132.6, and increment > 30 BPM and BPM > 120) except that the continuous resting supine tachycardia is inconsistent with POTS. Second clue that this is not POTS is an episode of HR increment exceeding 120 BPM (green oval) at supine position after completing the tilt. Mean supine HR = 106.6 ± 2.8, range 97.1–114.3 BPM, mean orthostatic HR 128 ± 2.4, and range 121.8–134.0 BPM.
Paroxysmal sinus tachycardia (PST) due to anxiety. The patient, a 34 y/o woman, was referred for evaluation of postural tachycardia syndrome (POTS). During montage in supine position before placing the blood pressure sensor (i.e., why the initial portion of recording is missing), she became very anxious after she was informed that she will be tilted in several minutes. The anxiety was associated with transient tachycardia 170 BPM, elevated BP, and CBFv (green ovals). Similar pattern (transient tachycardia, elevated BP, and CBFv) was observed at the onset of the tilt (blue oval). The supine tachycardia of similar character to that of the tilt confirms that this is not POTS but IST. Furthermore, the tachycardia is usually sustained and/or it is progressively increased during the tilt in POTS. CBFv is usually unchanged or decreased in POTS during the tilt.
Postural tachycardia syndrome (POTS) or paroxysmal sinus tachycardia (PST) due to the anxiety reaction? The supine variables were normal. The tilt test induced initial tachycardia associated with elevation of BP and CBFv (green ovals). This reaction is due to anxiety since BP and CBFv are elevated. In POTS, CBFv is usually unchanged or reduced. Similar reaction occurred at the end of the tilt (blue ovals). Note that patient was hyperventilating during the tilt (green tracing). The tilt test was done without any medication. Trial of beta blockers failed to improve orthostatic intolerance. Final diagnosis was PST. Mean supine HR was 91.5 ± 4.9 BPM; mean orthostatic HR during more steady HR (demarcated by a red box) was 109.3 ± 8.5 BPM. The mean HR during the whole tilting was 118.5 ± 13.8 BPM. Data from 25-year-old woman.
Inappropriate sinus tachycardia complicated by vasodepressor syncope. The average HR was above 100 BPM with the maximal heart rate 149 BPM during the supine position. The tilt provoked HR increase and marked oscillations in all signals including HR, BP, and CBFv. At the 5th minute of the tilt, BP suddenly declined (black arrow) that was accompanied by tachycardia 179 BPM culminated in a syncope. The decline in BP without bradycardia is characteristic of vasodepressor syncope due to reduced peripheral resistance. CBFv declined and the pulsatility index (systolic CBFv – diastolic CBFv) increased (blue arrows) that indicates cerebral vasodilation. Data from 26-year-old woman.
Vasomotor oscillations. Note marked fluctuations of BP occurring approximately every minute. CBFv also fluctuates in synchrony with BP. Patient was mildly anxious during the tilt test but she was not dizzy. Data from 47-year-old woman.
The transient drop in BP at the beginning of the tilt (designated by a green box) is artificial. The oscillometric device showed much higher BP (the small filled green box in (b)). Another clue that this is a technical artifact is the fact that there is no corresponding HR reaction and also CBFv is unchanged. The tilt test was normal. Data from 38-year-old woman.
This example shows arteficial drift in the plethysmographic finger BP that may be misinterpreted as orthostatic hypotension. The spurious decline in BP continued in spite of multiple repositionings of a sensor. Note that oscillometric BP from the upper arm (green boxes) shows absent orthostatic hypotension. There are a number of extrasystoles in the HR. BP was interpreted as normal. CBFv responses to the tilt were abnormal as there was a drop in CBFv from the supine 59.4 cm/sec to 36.5 cm/sec at the end of the tilt. Patient was dizzy during the tilt. The final diagnosis was orthostatic cerebral hypoperfusion syndrome. Data from 43-year-old man.
Syncope was associated with low blood pressure and CBFV (Table
OH can be progressive (Figures
OCHOs (Figures
In OHTN (Figure
Characteristic features of tachycardia syndromes (POTS, IST, and PST) are shown in Figures
Vasomotor oscillations (Figure
Eight patients had pseudosyncope (Figures
Psychogenic unresponsiveness. A patient became progressively obtunded and confused, experienced eyelid flutter, became aphasic, and finally did lose the consciousness during the tilt. The patient responded to reassurance and she regained consciousness while in the upright position. All monitoring variables were normal during the spell; patient became slightly tachycardiac after the spell. Data from 37-year-old woman.
POTS + psychogenic unresponsiveness + syncope. The tilt provoked symptomatic excessive heart rate increment associated with a drop in CBFv without orthostatic hypotension which satisfies criteria for POTS. Then the patient became progressively less responsive which was consistent with pseudosyncope (psychogenic unresponsiveness) since CBFv was stable. The patient responded to reassurance and she regained consciousness later during the tilting. However, subsequently the patient experienced true mixed syncope at the 5th minute of the tilt (the tilt starts at minute 10.6 of the recording) and the tilt was terminated. Final diagnoses: (1) POTS; (2) psychogenic unresponsiveness; and (3) mixed syncope. Data from 21-year-old woman.
Patients with pCAF had reduced CBFv in the supine position, had elevated cerebral vascular resistance in supine position and during the tilt, and had abnormal drop of CBFv score during the tilt (Table
Table
The characteristics of the patterns associated with the tilt test.
Disorder/syndrome | HR | BP | CBFv |
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Comments | ||||
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Supine | Tilt | Supine | Tilt | Supine | Tilt | Supine | Tilt | ||
Orthostatic hypotension (OH), compensated, with stable orthostatic CBFv |
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↕ | ↕ | ↓ |
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OH with stable orthostatic CBFv indicating preserved cerebral autoregulation. OH can have any pattern: early, late, sustained, intermittent, progressive, stable. Patients are typically not dizzy during the tilting |
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OH, uncompensated, with reduced orthostatic CBFv |
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↕ | ↕ | ↓ |
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↓ |
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OH with reduced orthostatic CBFv indicating either autoregulatory failure or BP below the autoregulatory range. Patients are typically dizzy during the tilting |
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Orthostatic cerebral hypoperfusion syndrome (OCHOs) |
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↕ |
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↓ |
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Orthostatic CBFv is low without OH or arrhythmia. Patients are typically dizzy during the tilting |
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Orthostatic hypertension syndrome (OHTN) |
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↕ | ↑ |
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If HR increases ≥30 BPM during the tilt then it is POTS. If HR increases <30 BPM and CBFv decreases during the tilt then it is OCHOs |
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Postural tachycardia syndrome (POTS) |
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↑ |
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HR increase during the tilt is usually sustained. HR ≥ 120 BPM during the tilt is also required. If maximal HR < 120 BPM during the tilt then it is called “mild orthostatic intolerance” |
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Inappropriate sinus tachycardia (IST) | ↑ |
↑ |
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HR during the supine may fluctuate but mean HR > 100 BPM during supine. HR is increased during the tilt and the increase is usually fluctuating |
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Paroxysmal sinus tachycardia (PST) |
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↑ |
↕ |
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HR increase which may happen during both supine and the tilt is usually intermittent and associated with anxiety and may respond to reassurance |
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Syncope, cardiovagal |
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↓ |
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↓ |
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↓ |
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↕ | HR < 40 BPM |
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Syncope, vasodepressor |
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↓ |
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↓ |
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↕ | Minimal HR slowing (<10%) |
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Syncope, mixed |
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↓ |
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↓ |
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↓ |
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↕ | Both HR and BP decrease |
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Primary cerebral autoregulatory failure (pCAF) |
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↓ |
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Hyperventilation should be ruled out |
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Psychogenic pseudosyncope | ↕ | ↕ | ↕ | ↕ |
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↕ | ↕ | Pseudosyncope can occur in both supine and upright position |
Comments: CBFv = cerebral blood flow velocity;
This study showed head-to-head comparisons of common tilt test patterns. Characteristic pattern associated with a particular orthostatic syndrome can be grouped into abnormalities predominantly affecting heart rate (PST, IST, and POTS), blood pressure (syncope, OH, and OHTN), and cerebral blood flow (OCHOs, pCAF). Psychogenic pseudosyncope is associated with stable CBFv without any particular heart rate or blood pressure pattern. This study also showed that criteria for several orthostatic syndromes had to be modified to allow unambiguous pattern classifications.
Orthostatic symptoms, except of syncope, are nonspecific and in general poorly correlating with orthostatic blood pressure or heart rate. This study showed that orthostatic drop in CBFv is more sensitive and specific marker of prediction of orthostatic symptoms than orthostatic blood pressure changes. Therefore CBFv is better proxy for cerebral hypoperfusion than orthostatic hypotension.
Criteria for orthostatic syndromes are heterogeneous; some criteria are exclusively physiological (e.g., OH which can be symptomatic or asymptomatic) while the others require also the presence of symptoms, for example, POTS. Nevertheless, the information obtained from the tilt test should not be used in isolation but always on clinical ground.
These syndromes share excessive heart rate increment. Primarily, it is the timing of tachycardia that distinguishes each syndrome. Using the nonmodified criteria, majority of patients with IST and PST satisfy also the POTS criteria. The ambiguities in determination of tachycardia syndromes were solved by modifying the diagnostic criteria as mentioned in the Section
Neurally mediated syncope has a characteristic pattern. Loss of consciousness usually occurs if systolic blood pressure declines to 60 mmHg [
PCAF is defined as low supine CBFv without supine hypotension or other hemodynamic abnormalities that can explain low CBFv. Patients with pCAF have increased cerebral vascular resistance that may be due to cerebral autoregulatory failure [
Original definition of OHTN included only an increase of blood pressure during the tilt while heart rate and CBFv responses to tilting were not considered. These limitations can cause diagnostic overlap with POTS since occasional rise in blood pressure during tilting can be observed in the hyperadrenergic form of POTS [
Typically, the tilt test uses heart rate and blood pressure responses in classification of results [
No specific changes in hemodynamic parameters except of stable CBFv have been found in this study. This is in contrast with a recent study [
Ambiguities in definition of orthostatic syndromes were removed by adjusting the diagnostic criteria. Nevertheless, the clinical significance of adjusted criteria needs to be validated in future studies.
Table
Tilt test can be used as an add-on in diagnosis of orthostatic syndromes. However diagnostic criteria for several syndromes had to be made more explicit to allow unambiguous pattern classification. To be able to classify all patterns, it is essential to monitor CBFv in addition to blood pressure and heart rate.
Peter Novak served on a scientific advisory board of Lundbeck. Study was funded by Department of Neurology, University of Massachusetts Medical School.
The author thanks Dr. Lan Qin, Shane Stanek, and Steve Smajkiewicz for their help in data collection.