Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt

BACKGROUND

The powers of the low-frequency (LF) and high-frequency (HF) oscillations characterizing heart rate variability (HRV) appear to reflect, in their reciprocal relationship, changes in the state of the sympathovagal balance occurring during numerous physiological and pathophysiological conditions. However, no adequate information is available on the quantitative resolution of this methodology.

METHODS AND RESULTS

We studied 22 healthy volunteers (median age, 46.5 years) who were subjected after a rest period to a series of passive head-up tilt steps randomly chosen from the following angles: 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. From the continuous ECG, after appropriate analog-to-digital conversion, a personal computer was used to compute, with an autoregressive methodology, time and frequency domain indexes of RR interval variability. Spectral and cross-spectral analysis with the simultaneously recorded respiratory signal excluded its contribution to LF. Age was significantly correlated to variance and to the absolute values in milliseconds squared of very-low-frequency (VLF), LF, and HF components. The tilt angle was correlated to both LF and HF (expressed in normalized units [nu]) and to the LF-to-HF ratio (r = .78, -.72, and .68; respectively). Lower levels of correlation were found with HF (in ms2) and RR interval. No correlation was present between tilt angle and variance, VLF, or LF (in ms2). Individual analysis confirmed that the use of nu provided the greatest consistency of results.

CONCLUSIONS

Spectral analysis of HRV, using nu or LF-to-HF ratio, appears to be capable of providing a noninvasive quantitative evaluation of graded changes in the state of the sympathovagal balance.

Human responses to upright tilt: a window on central autonomic integration

1. We examined interactions between haemodynamic and autonomic neural oscillations during passive upright tilt, to gain better insight into human autonomic regulatory mechanisms. 2. We recorded the electrocardiogram, finger photoplethysmographic arterial pressure, respiration and peroneal nerve muscle sympathetic activity in nine healthy young adults. Subjects breathed in time with a metronome at 12 breaths min-1 (0.2 Hz) for 5 min each, in supine, and 20, 40, 60, 70 and 80 deg head-up positions. We performed fast Fourier transform (and autoregressive) power spectral analyses and integrated low-frequency (0.05-0.15 Hz) and respiratory-frequency (0. 15-0.5 Hz) spectral powers. 3. Integrated areas of muscle sympathetic bursts and their low- and respiratory-frequency spectral powers increased directly and significantly with the tilt angle. The centre frequency of low-frequency sympathetic oscillations was constant before and during tilt. Sympathetic bursts occurred more commonly during expiration than inspiration at low tilt angles, but occurred equally in expiration and inspiration at high tilt angles. 4. Systolic and diastolic pressures and their low- and respiratory-frequency spectral powers increased, and R-R intervals and their respiratory-frequency spectral power decreased progressively with the tilt angle. Low-frequency R-R interval spectral power did not change. 5. The cross-spectral phase angle between systolic pressures and R-R intervals remained constant and consistently negative at the low frequency, but shifted progressively from positive to negative at the respiratory frequency during tilt. The arterial baroreflex modulus, calculated from low-frequency cross-spectra, decreased at high tilt angles. 6. Our results document changes of baroreflex responses during upright tilt, which may reflect leftward movement of subjects on their arterial pressure sympathetic and vagal response relations. The intensity, but not the centre frequency of low-frequency cardiovascular rhythms, is modulated by the level of arterial baroreceptor input. Tilt reduces respiratory gating of sympathetic and vagal motoneurone responsiveness to stimulatory inputs for different reasons; during tilt, sympathetic stimulation increases to a level that overwhelms the respiratory gate, and vagal stimulation decreases to a level below that necessary for maximal respiratory gating to occur.

The rational clinical examination. Is this patient hypovolemic?

OBJECTIVE

To review, systematically, the physical diagnosis of hypovolemia in adults.

METHODS

We searched MEDLINE (January 1966-November 1997), personal files, and bibliographies of textbooks on physical diagnosis and identified 10 studies investigating postural vital signs or the capillary refill time of healthy volunteers, some of whom underwent phlebotomy of up to 1150 mL of blood, and 4 studies of patients presenting to emergency departments with suspected hypovolemia, usually due to vomiting, diarrhea, or decreased oral intake.

RESULTS

When clinicians evaluate adults with suspected blood loss, the most helpful physical findings are either severe postural dizziness (preventing measurement of upright vital signs) or a postural pulse increment of 30 beats/min or more. The presence of either finding has a sensitivity for moderate blood loss of only 22% (95% confidence interval [CI], 6%-48%) but a much greater sensitivity for large blood loss of 97% (95% CI, 91%-100%); the corresponding specificity is 98% (95% CI, 97%-99%). Supine hypotension and tachycardia are frequently absent, even after up to 1150 mL of blood loss (sensitivity, 33%; 95% CI, 21%-47%, for supine hypotension). The finding of mild postural dizziness has no proven value. In patients with vomiting, diarrhea, or decreased oral intake, the presence of a dry axilla supports the diagnosis of hypovolemia (positive likelihood ratio, 2.8; 95% CI, 1.4-5.4), and moist mucous membranes and a tongue without furrows argue against it (negative likelihood ratio, 0.3; 95% CI, 0.1-0.6 for both findings). In adults, the capillary refill time and poor skin turgor have no proven diagnostic value.

CONCLUSIONS

A large postural pulse change (> or =30 beats/min) or severe postural dizziness is required to clinically diagnose hypovolemia due to blood loss, although these findings are often absent after moderate amounts of blood loss. In patients with vomiting, diarrhea, or decreased oral intake, few findings have proven utility, and clinicians should measure serum electrolytes, serum blood urea nitrogen, and creatinine levels when diagnostic certainty is required.

The North American Vasovagal Pacemaker Study (VPS). A randomized trial of permanent cardiac pacing for the prevention of vasovagal syncope

OBJECTIVES

This study was done to evaluate pacemaker therapy for severe recurrent vasovagal syncope.

BACKGROUND

Nonrandomized studies have suggested that permanent pacing might help control the symptoms of recurrent vasovagal syncope. The study goal was to evaluate the effect of permanent pacemaker implantation on syncope in patients with frequently recurrent vasovagal syncope.

METHODS

Patients with > or = 6 lifetime episodes of syncope and with a tilt-table test that induced syncope or presyncope, as well as a relative bradycardia, were randomized to receive a dual-chamber pacemaker or not. The pacemaker prevented bradycardia and provided high-rate pacing if a predetermined drop in heart rate occurred (rate-drop response). The primary outcome was the first recurrence of syncope. Patients also completed a detailed diary recording presyncopal episodes.

RESULTS

A total of 284 patients was originally planned and a pilot study of 60 patients was initiated. At the planned first formal interim analysis of efficacy of the pilot study, an unanticipated large treatment effect was observed which fulfilled the prespecified criteria for early termination of the study. At that time, there were 54 patients enrolled, randomized evenly to no pacemaker or to pacemaker. In the no-pacemaker and pacemaker groups the mean ages were 40 and 46 years; 74% and 70% patients, respectively, were female. The baseline tilt-table test showed a slowest heart <60/min or longest heart period >1000 ms in 60% of no-pacemaker patients and 72% of pacemaker patients. There was a marked reduction in the postrandomization risk of syncope in pacemaker patients (relative risk reduction 85.4%, 95% confidence interval 59.7% to 94.7%; 2p=0.000022).

CONCLUSIONS

Dual-chamber pacing with rate-drop response reduces the likelihood of syncope in patients with recurrent vasovagal syncope.

Misdiagnosis of epilepsy: many seizure-like attacks have a cardiovascular cause

OBJECTIVES

We sought to investigate the value of cardiovascular tests to diagnose convulsive syncope in patients with apparent treatment-resistant epilepsy.

BACKGROUND

As many as 20% to 30% of epileptics may have been misdiagnosed. Many of these patients may have cardiovascular syncope, with abnormal movements due to cerebral hypoxia, which may be difficult to differentiate from epilepsy on clinical grounds.

METHODS

Seventy-four patients (33 men, mean age 38.9 +/- 18 years [range 16 to 77]) who were previously diagnosed with epilepsy were studied. Inclusion criteria included continued attacks despite adequate anticonvulsant drug treatment (n = 36) or uncertainty about the diagnosis of epilepsy, on the basis of the clinical description of the seizures (n = 38). Each patient underwent a head-up tilt test and carotid sinus massage during continuous electrocardiography, electroencephalography and blood pressure monitoring. Ten patients subsequently underwent long-term electrocardiographic (ECG) monitoring with an implantable loop recorder.

RESULTS

In total, an alternative diagnosis was found in 31 patients (41.9%), including 13 (36.1%) of 36 patients taking an anticonvulsant medication. Nineteen patients (25.7%) developed profound hypotension or bradycardia during the head-up tilt test, confirming the diagnosis of vasovagal syncope. One other patient had a typical vasovagal reaction during intravenous cannulation. Two patients developed psychogenic symptoms during the head-up tilt test. Seven patients (9.5%) had significant ECG pauses during carotid sinus massage. In two patients, episodes of prolonged bradycardia correlated precisely with seizures according to the insertable ECG recorder.

CONCLUSIONS

A simple, noninvasive cardiovascular evaluation may identify an alternative diagnosis in many patients with apparent epilepsy and should be considered early in the management of patients with convulsive blackouts.

Randomized assessment of syncope trial: conventional diagnostic testing versus a prolonged monitoring strategy

BACKGROUND

Establishing a diagnosis in patients with unexplained syncope is complicated by infrequent and unpredictable events. Prolonged monitoring may be an alternative strategy to conventional testing with short-term monitoring and provocative tilt and electrophysiological testing.

METHODS AND RESULTS

Sixty patients (aged 66+/-14 years, 33 male) with unexplained syncope were randomized to "conventional" testing with an external loop recorder and tilt and electrophysiological testing or to prolonged monitoring with an implantable loop recorder with 1 year of monitoring. If patients remained undiagnosed after their assigned strategy, they were offered crossover to the alternate strategy. A diagnosis was obtained in 14 of 27 patients randomized to prolonged monitoring compared with 6 of 30 patients undergoing conventional testing (52% versus 20%, P=0.012). Crossover was associated with a diagnosis in 1 of 6 patients undergoing conventional testing compared with 8 of 13 patients who completed monitoring (17% versus 62%, P=0.069). Overall, prolonged monitoring was more likely to result in a diagnosis than was conventional testing (55% versus 19%, P=0.0014). Bradycardia was detected in 14 patients undergoing monitoring compared with 3 patients undergoing conventional testing (40% versus 8%, P=0.005).

CONCLUSIONS

A prolonged monitoring strategy is more likely to provide a diagnosis than conventional testing in patients with unexplained syncope. Consideration should be given to earlier implementation of a monitoring strategy.

Cardiac origins of the postural orthostatic tachycardia syndrome

OBJECTIVES

The purpose of this study was to test the hypothesis that a small heart coupled with reduced blood volume contributes to the postural orthostatic tachycardia syndrome (POTS) and that exercise training improves this syndrome.

BACKGROUND

Patients with POTS have marked increases in heart rate during orthostasis. However, the underlying mechanisms are unknown and the effective therapy is uncertain.

METHODS

Twenty-seven POTS patients underwent autonomic function tests, cardiac magnetic resonance imaging, and blood volume measurements. Twenty-five of them participated in a 3-month specially designed exercise training program with 19 completing the program; these patients were re-evaluated after training. Results were compared with those of 16 healthy controls.

RESULTS

Upright heart rate and total peripheral resistance were greater, whereas stroke volume and cardiac output were smaller in patients than in controls. Baroreflex function was similar between groups. Left ventricular mass (median [25th, 75th percentiles], 1.26 g/kg [1.12, 1.37 g/kg] vs. 1.45 g/kg [1.34, 1.57 g/kg]; p < 0.01) and blood volume (60 ml/kg [54, 64 ml/kg] vs. 71 ml/kg [65, 78 ml/kg]; p < 0.01) were smaller in patients than in controls. Exercise training increased left ventricular mass and blood volume by approximately 12% and approximately 7% and decreased upright heart rate by 9 beats/min [1, 17 beats/min]. Ten of 19 patients no longer met POTS criteria after training, whereas patient quality of life assessed by the 36-item Short-Form Health Survey was improved in all patients after training.

CONCLUSIONS

Autonomic function was intact in POTS patients. The marked tachycardia during orthostasis was attributable to a small heart coupled with reduced blood volume. Exercise training improved or even cured this syndrome in most patients. It seems reasonable to offer POTS a new name based on its underlying pathophysiology, the "Grinch syndrome," because in this famous children's book by Dr. Seuss, the main character had a heart that was "two sizes too small."

Mechanism of syncope in patients with isolated syncope and in patients with tilt-positive syncope

BACKGROUND

Because of its episodic behavior, the correlation of spontaneous syncope with an abnormal finding can be considered a reference standard.

METHODS AND RESULTS

We inserted an implantable loop recorder in 111 patients with syncope, absence of significant structural heart disease, and a normal ECG; tilt-testing was negative in 82 (isolated syncope) and positive in 29 (tilt-positive). The patients had had >/=3 episodes of syncope in the previous 2 years and were followed up for 3 to 15 months. Results were similar in the isolated syncope group and the tilt-positive group: syncope recurred in 28 (34%) and 10 patients (34%), respectively, and electrocardiographic correlation was found in 24 (23%) and 8 (28%) patients, respectively. The most frequent finding, which was recorded in 46% and 62% of patients, respectively, was one or more prolonged asystolic pauses, mainly due to sinus arrest, preceded for a few minutes by progressive bradycardia or progressive tachycardia-bradycardia. Bradycardia without pauses was observed in 8% and 12% of cases, respectively. The remaining patients had normal sinus rhythm or sinus tachycardia, except for one, who had ectopic atrial tachycardia. In the tilt-positive group, an asystolic syncope was also recorded when the type of response to tilt-testing was vasodepressor or mixed. Presyncopal episodes were never characterized by asystolic pauses; normal sinus rhythm was the most frequent finding.

CONCLUSIONS

Homogeneous findings were observed during syncope. In most patients, the likely cause was neurally-mediated, and the most frequent mechanism was a bradycardic reflex. In the other cases, a normal sinus rhythm was frequently recorded. Presyncope was not an accurate surrogate for syncope in establishing a diagnosis.

Use of an extended monitoring strategy in patients with problematic syncope. Reveal Investigators

BACKGROUND

The conventional investigation of patients who present with syncope involves short-term ECG monitoring or provocative testing with head-up tilt and electrophysiological testing. A symptom-rhythm correlation is often difficult to obtain during spontaneous syncope because of its sporadic, infrequent, and unpredictable nature.

METHODS AND RESULTS

We used a prolonged monitoring strategy to determine the cause of syncope in 85 patients (age, 59+/-18 years; 44 men) with recurrent undiagnosed syncope with an implantable loop recorder capable of cardiac monitoring for up to 18 months. During a mean of 10.5+/-4.0 months of follow-up, symptoms recurred in 58 patients (68%) 71+/-79 days (2.3+/-2.6 months) after implantable loop recorder insertion. An arrhythmia was detected in 42% of patients who recorded a rhythm during recurrent symptoms, with bradycardia present in 18 and tachycardia in 3. Five of the 18 bradycardic patients and 2 additional sinus rhythm patients received a clinical diagnosis of neurally mediated syncope. Patients who experienced presyncope were much less likely to record an arrhythmia during symptoms compared with recurrence of syncope (24% versus 70%, P=0.0005). There were no adverse events associated with recurrent symptoms, and there were no sudden deaths. Inability to freeze after an event occurred in 8 patients, and pocket infection occurred in 3.

CONCLUSIONS

The strategy of prolonged monitoring is effective and safe in patients with problematic syncope.

Inappropriate sympathetic activation at onset of septic shock: a spectral analysis approach

The autonomic cardiovascular control was investigated in 10 patients with septic shock, 10 patients with sepsis syndrome, and six tilted healthy subjects. Overall variability, high- and low-frequency components (AUC, HF, and LF, beats/min(2)/Hz or mm Hg(2)/Hz) from heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures spectra were obtained from 5-min recordings. LF(HR)/HF(HR) and the square root of LF(SBP)/LF(HR) (alpha) were used as indices of sympathovagal interaction and baroreflex control of the heart, respectively. Compared with tilted control subjects and patients with sepsis syndrome, septic shock is characterized by reduction in: (1) HR variability, i.e., decreased AUC(HR) (p = 0.007), LF(HR) (p = 0.002), and LF(HR)/HF(HR) (p = 0.0002); (2) DBP variability, i.e., decreased AUC(DBP) (p = 0.003) and LF(DBP) (p = 0.001), (3) alpha (p = 0.003). In septic shock, LF(HR)/HF(HR), alpha, and LF(DBP) correlated with mean blood pressure (r = 0.67, p = 0.04, r = 0.64, p = 0.03, and r = 0.88, p = 0.0008, respectively), and with plasma norepinephrine levels (r = -0.65, p = 0.03, r = -0.79, p = 0.006, and r = -0.69, p = 0.03, respectively). In conclusion, onset of septic shock is characterized by high concentrations of circulating catecholamines but impaired sympathetic modulation on heart and vessels, suggesting that central autonomic regulatory impairment contributes to circulatory failure.

Dual-chamber pacing in the treatment of neurally mediated tilt-positive cardioinhibitory syncope : pacemaker versus no therapy: a multicenter randomized study. The Vasovagal Syncope International Study (VASIS) Investigators

BACKGROUND-This study was performed to compare implantation of a DDI pacemaker with rate hysteresis with no implant in respect to syncopal recurrences in patients with severe cardioinhibitory tilt-positive neurally mediated syncope. METHODS AND RESULTS-Forty-two patients from 18 European centers were randomized to receive a DDI pacemaker programmed to 80 bpm with hysteresis of 45 bpm (19 patients) or no pacemaker (23 patients). Inclusion criteria were >/=3 syncopes over the last 2 years and a positive cardioinhibitory (Vasovagal Syncope International Study types 2A and 2B) response to tilt testing. The median number of previous syncopal episodes was 6; asystolic response to tilt testing was present in 36 patients (86%) (mean asystole, 13.9+/-10.2 seconds). All patients were followed up for a minimum of 1.0 years and a maximum of 6.7 years (mean, 3.7+/-2.2). One patient (5%) in the pacemaker arm experienced recurrence of syncope compared with 14 patients (61%) in the no-pacemaker arm (P=0.0006). In the no-pacemaker arm, the median time to first syncopal recurrence was 5 months, with a rate of 0.44 per year. On repeated tilt testing performed within 15 days after enrollment, positive responses were observed in 59% of patients with pacemakers and in 61% of patients without pacemakers (P=NS). CONCLUSIONS-In a limited, select group of patients with tilt-positive cardioinhibitory syncope, DDI pacing with hysteresis reduced the likelihood of syncope. The benefit of the therapy was maintained over the long term. Even in untreated patients, the syncopal recurrence burden was low. A negative result of tilt testing was not a useful means to evaluate therapy efficacy.

Management of vasovagal syncope: controlling or aborting faints by leg crossing and muscle tensing

BACKGROUND

Posture-related vasovagal syncope is by far the most frequent cause of transient loss of consciousness, and present pharmacological and cardiac pacing treatment remains unsatisfactory. A simple maneuver to prevent or diminish vasovagal reactions would be beneficial.

METHODS AND RESULTS

Twenty-one patients with recurrent syncope (age 17 to 74 years, 11 males) who were referred for routine tilt-table testing and had a positive test were included. They were instructed to perform leg crossing and muscle tensing for at least 30 seconds at the onset of a tilt table-provoked impending faint. Continuously measured blood pressure and heart rate at nadir and during the maneuver were compared. Ten months after the test, a telephone follow-up was performed. The physical counter-maneuver, performed in 20 of 21 subjects, increased blood pressure and heart rate. Systolic blood pressure rose from 65+/-13 to 106+/-16 mm Hg (mean+/-SD, P<0.001), and diastolic blood pressure rose from 43+/-9 to 65+/-10 mm Hg (P<0.001). During the maneuver, prodromal symptoms disappeared in all patients, and none lost consciousness. After terminating the maneuver, symptoms did not return in 5 subjects during the test. At follow-up, 13 of 20 patients reported that they applied the maneuver in daily life and benefited from it.

CONCLUSIONS

Leg crossing combined with tensing muscles at the onset of prodromal symptoms can postpone and in some subjects prevent vasovagal syncope.

Does the chronic fatigue syndrome involve the autonomic nervous system?

PURPOSE

To investigate the role of the autonomic nervous system in the symptoms of patients with chronic fatigue syndrome (CFS) and delineate the pathogenesis of the orthostatic Intolerance and predisposition to neurally mediated syncope reported in this patient group.

PATIENTS AND METHODS

Twenty-three CFS patients and controls performed a battery of autonomic function tests. The CFS patients completed questionnaires pertaining to autonomic and CFS symptoms, their level of physical activity, and premorbid and coexisting psychiatric disorders. The relationship between autonomic test results, cardiovascular deconditioning, and psychiatric disorders was examined with multivariate statistics and the evidence that autonomic changes seen in CFS might be secondary to a postviral, idiopathic autonomic neuropathy was explored.

RESULTS

The CFS subjects had a significant increase in baseline (P < 0.01) and maximum heart rate (HR) on standing and tilting (both P < 0.0001). Tests of parasympathetic nervous system function (the expiratory inspiratory ratio, P < 0.005; maximum minus minimum HR difference, P < 0.05), were significantly less in the CFS group as were measures of sympathetic nervous system function (systolic blood pressure decrease with tilting, P < 0.01; diastolic blood pressure decrease with tilting, P < 0.05; and the systolic blood pressure decrease during phase II of a Valsalva maneuver, P < 0.05). Twenty-five percent of CFS subjects had a positive tilt table test. The physical activity index was a significant predictor of autonomic test results (resting, sitting, standing, and tilted HR, P < 0.05 to P < 0.009); and the blood pressure decrease in phase II of the Valvalsa maneuver, P < 0.05) whereas premorbid and coexistent psychiatric conditions were not. The onset of autonomic symptoms occurred within 4 weeks of a viral infection in 46% of patients-a temporal pattern that is consistent with a postviral, idiopathic autonomic neuropathy.

CONCLUSION

Patients with CFS show alterations in measures of sympathetic and parasympathetic nervous system function. These results, which provide the physiological basis for the orthostatic intolerance and other symptoms of autonomic function in this patient group, may be explained by cardiovascular deconditioning, a postviral idiopathic autonomic neuropathy, or both.

Syncope Evaluation in the Emergency Department Study (SEEDS): a multidisciplinary approach to syncope management

BACKGROUND

The primary aim and central hypothesis of the study are that a designated syncope unit in the emergency department improves diagnostic yield and reduces hospital admission for patients with syncope who are at intermediate risk for an adverse cardiovascular outcome.

METHODS AND RESULTS

In this prospective, randomized, single-center study, patients were randomly allocated to 2 treatment arms: syncope unit evaluation and standard care. The 2 groups were compared with chi2 test for independence of categorical variables. Wilcoxon rank sum test was used for continuous variables. Survival was estimated with the Kaplan-Meier method. One hundred three consecutive patients (53 women; mean age 64+/-17 years) entered the study. Fifty-one patients were randomized to the syncope unit. For the syncope unit and standard care patients, the presumptive diagnosis was established in 34 (67%) and 5 (10%) patients (P<0.001), respectively, hospital admission was required for 22 (43%) and 51 (98%) patients (P<0.001), and total patient-hospital days were reduced from 140 to 64. Actuarial survival was 97% and 90% (P=0.30), and survival free from recurrent syncope was 88% and 89% (P=0.72) at 2 years for the syncope unit and standard care groups, respectively.

CONCLUSIONS

The novel syncope unit designed for this study significantly improved diagnostic yield in the emergency department and reduced hospital admission and total length of hospital stay without affecting recurrent syncope and all-cause mortality among intermediate-risk patients. Observations from the present study provide benchmark data for improving patient care and effectively utilizing healthcare resources.

A randomized, double-blind, placebo-controlled study of permanent cardiac pacing for the treatment of recurrent tilt-induced vasovagal syncope. The vasovagal syncope and pacing trial (SYNPACE)

AIMS

Recently, some studies revealed the efficacy of pacemaker implantation in decreasing recurrences in patients with vasovagal syncope. As these studies were not blinded or placebo-controlled, the benefits observed might have been due to a bias in the assessment of outcomes or to a placebo effect of the pacemaker. We performed a randomized, double-blind, placebo-controlled study in order to ascertain if pacing therapy reduces the risk of syncope relapse.

METHODS AND RESULTS

Twenty-nine patients (53 +/- 16 years; 19 women) with severe recurrent tilt-induced vasovagal syncope (median 12 syncopes in the lifetime) and 1 syncopal relapse after head-up tilt testing underwent implantation of a pacemaker, and were randomized to pacemaker ON or to pacemaker OFF. During a median of 715 days of follow-up, 8 (50%) patients randomized to pacemaker ON had recurrence of syncope compared to 5 (38%) of patients randomized to pacemaker OFF (p = n.s.); the median time to first syncope was longer in the pacemaker ON than in pacemaker OFF group, although not significantly so (97 [38-144] vs 20 [4-302] days; p = 0.38). There was also no significant difference in the subgroups of patients who had had a mixed response and in those who had had an asystolic response during head-up tilt testing.

CONCLUSION

Our data were unable to show a superiority of active pacing versus inactive pacing in preventing syncopal recurrence in patients with severe recurrent tilt-induced vasovagal syncope.

GRADED REPAIR OF CRANIAL BASE DEFECTS AND CEREBROSPINAL FLUID LEAKS IN TRANSSPHENOIDAL SURGERY

OBJECTIVE

A graded approach to cerebrospinal fluid (CSF) leak repair after transsphenoidal surgery is presented.

METHODS

Patients undergoing endonasal tumor removal during an 8-year period were reviewed. Intraoperative CSF leaks were classified as Grade 0, no leak observed; Grade 1, small leak without obvious diaphragmatic defect; Grade 2, moderate leak; or Grade 3, large diaphragmatic/dural defect. Cranial base repair was tailored to the leak grade as Grade 0, collagen sponge; Grade 1, two-layered collagen sponge repair with intrasellar titanium mesh buttress; Grade 2, intrasellar and sphenoid sinus fat grafts with collagen sponge overlay and titanium buttress; and Grade 3, same as Grade 2 with CSF diversion in most cases. A provocative tilt test was performed before patient discharge to assess the integrity of the CSF leak repair. Protocol modifications adopted in 2003 included an intrasellar fat graft in Grade 1 leaks with a large intrasellar dead space, frequent use of BioGlue (CryoLife, Inc., Atlanta, GA) in Grade 1, 2, and 3 leaks, and CSF diversion for all Grade 3 leaks.

RESULTS

Among 668 cases in 620 patients (475 pituitary adenomas and 145 other lesions), an intraoperative CSF leak was observed in 57% of the cases: 32.5% Grade 1, 15% Grade 2, and 8.7% Grade 3. Postoperative repair failures occurred in 17 cases (2.5%), including 0.7, 3, 1, and 12% of Grade 0, 1, 2, and 3 CSF leaks, respectively. Bacterial meningitis occurred in three patients (0.45%). After protocol modifications in 2003, repair failures decreased from 4 to 1.2% (P = 0.02).

CONCLUSION

A graded repair approach to CSF leaks in transsphenoidal surgery avoids tissue grafts and CSF diversion in more than 60% of patients. Protocol modifications adopted in the last 340 cases have reduced the failure rate to 1% overall and 7% for Grade 3 leaks. Provocative tilt testing before patient discharge is helpful in the timely diagnosis of postoperative CSF leaks.

Prospective evaluation of patients with syncope: a population-based study

PURPOSE

To determine the diagnostic yield of a standardized sequential evaluation of patients with syncope in a primary care teaching hospital.

PATIENTS AND METHODS

All consecutive patients who presented to the emergency department with syncope as a chief complaint were enrolled. Their evaluation included initial and routine clinical examination, including carotid sinus massage, as well as electrocardiography and basic laboratory testing. Targeted tests, such as echocardiography, were used when a specific entity was suspected clinically. Other cardiovascular tests (24-hour Holter monitoring, ambulatory loop recorder ECG, upright tilt test, and signal-averaged electrocardiography) were performed in patients with unexplained syncope after the initial steps. Electrophysiologic studies were performed in selected patients only as clinically appropriate. Follow-up information on recurrence and mortality were obtained every 6 months for as long as 18 months for 94% (n = 611) of the patients.

RESULTS

After the initial clinical evaluation, a suspected cause of syncope was found in 69% (n = 446) of the 650 patients, including neurocardiogenic syncope (n = 234, 36%), orthostatic hypotension (n = 156, 24%), arrhythmia (n = 24, 4%), and other diseases (n = 32, 5%). Of the 67 patients who underwent targeted tests, suspected diagnoses were confirmed in 49 (73%) patients: aortic stenosis (n = 8, 1%), pulmonary embolism (n = 8, 1%), seizures/stroke (n = 30, 5%), and other diseases (n = 3). Extensive cardiovascular workups, which were performed in 122 of the 155 patients in whom syncope remained unexplained after clinical assessment, provided a suspected cause of syncope in only 30 (25%) patients, including arrhythmias in 18 (60%), all of whom had abnormal baseline ECGs. The 18-month mortality was 9% (n = 55, including 8 patients with sudden death); syncope recurred in 15% (n = 95) of the patients.

CONCLUSION

The diagnostic yield of a standardized clinical evaluation of syncope was 76%, greater than reported previously in unselected patients. Electrocardiogram-based risk stratification was useful in guiding the use of specialized cardiovascular tests.

The relationship between neurally mediated hypotension and the chronic fatigue syndrome

OBJECTIVE

To compare the clinical symptoms and response evoked by upright tilt-table testing in healthy individuals and in a sample of those satisfying strict criteria for chronic fatigue syndrome.

DESIGN

Case-comparison study with mean (SD) follow-up of 24 (5) weeks.

SETTING

Tertiary care hospital.

PATIENTS AND OTHER PARTICIPANTS

A sample of 23 patients with chronic fatigue syndrome (five men and 18 women; mean age, 34 years), each of whom fulfilled the strict diagnostic criteria of the Centers for Disease Control and Prevention, was recruited from regional chronic fatigue support groups and from the investigators' clinical practices. There were 14 healthy controls (four men and 10 women; mean age, 36 years).

INTERVENTIONS

Each subject completed a symptom questionnaire and underwent a three-stage upright tilt-table test (stage 1, 45 minutes at 70 degrees tilt; stage 2, 15 minutes at 70 degrees tilt with 1 to 2 micrograms/min of isoproterenol; and stage 3, 10 minutes at 70 degrees with 3 to 4 micrograms/min of isoproterenol). Patients were offered therapy with fludrocortisone, beta-adrenergic blocking agents, and disopyramide, alone or in combination, directed at neurally mediated hypotension.

MAIN OUTCOME MEASURES

Response to upright tilt and scores on symptom questionnaires prior to and during follow-up.

RESULTS

An abnormal response to upright tilt was observed in 22 of 23 patients with chronic fatigue syndrome vs four of 14 controls (P < .001). Seventy percent of chronic fatigue syndrome patients, but no controls, had an abnormal response during stage 1 (P < .001). Nine patients reported complete or nearly complete resolution of chronic fatigue syndrome symptoms after therapy directed at neurally mediated hypotension.

CONCLUSIONS

We conclude that chronic fatigue syndrome is associated with neurally mediated hypotension and that its symptoms may be improved in a subset of patients by therapy directed at this abnormal cardiovascular reflex.

Diagnosing syncope. Part 2: Unexplained syncope. Clinical Efficacy Assessment Project of the American College of Physicians

PURPOSE

To review the literature on diagnostic testing in syncope that remains unexplained after initial clinical assessment.

DATA SOURCES

MEDLINE search.

STUDY SELECTION

Published papers were selected if they addressed diagnostic testing in syncope, near syncope, or dizziness.

DATA EXTRACTION

Studies were identified as population studies, referral studies, or case series.

DATA SYNTHESIS

After a thorough history, physical examination, and electrocardiography, the cause of syncope remains undiagnosed in 50% of patients. In such patients, information may be derived from the results of carefully selected diagnostic tests, especially 1) electrophysiologic studies in patients with organic heart disease, 2) Holter monitoring or telemetry in patients known to have or suspected of having heart disease, 3) loop monitoring in patients with frequent events and normal hearts, 4) psychiatric evaluation in patients with frequent events and no injury, and 5) tilt-table testing in patients who have infrequent events or in whom vasovagal syncope is suspected. Hospitalization is indicated for high-risk patients, especially those with known heart disease and elderly patients.

CONCLUSIONS

A flexible, focused approach is required to diagnose syncope. Features of the initial history and physical examination help guide diagnostic testing.

Effect of age and gender on sudomotor and cardiovagal function and blood pressure response to tilt in normal subjects

Normative data are limited on autonomic function tests, especially beyond age 60 years. We therefore evaluated these tests in a total of 557 normal subjects evenly distributed by age and gender from 10 to 83 years. Heart rate (HR) response to deep breathing fell with increasing age. Valsalva ratio varied with both age and gender. QSART (quantitative sudomotor axon-reflex test) volume was consistently greater in men (approximately double) and progressively declined with age for all three lower extremity sites but not the forearm site. Orthostatic blood pressure reduction was greater with increasing age. HR at rest was significantly higher in women, and the increment with head-up tilt fell with increasing age. For no tests did we find a regression to zero, and some tests seem to level off with increasing age, indicating that diagnosis of autonomic failure was possible to over 80 years of age.

Mechanism of syncope in patients with bundle branch block and negative electrophysiological test

BACKGROUND

In patients with syncope and bundle branch block (BBB), syncope is suspected to be attributable to a paroxysmal atrioventricular (AV) block, but little is known of its mechanism when electrophysiological study is negative.

METHODS AND RESULTS

We applied an implantable loop recorder in 52 patients with BBB and negative conventional workup. During a follow-up of 3 to 15 months, syncope recurred in 22 patients (42%), the event being documented in 19 patients after a median of 48 days. The most frequent finding, recorded in 17 patients, was one or more prolonged asystolic pause mainly attributable to AV block; the remaining 2 patients had normal sinus rhythm or sinus tachycardia. The onset of the bradycardic episodes was always sudden but was sometimes preceded by ventricular premature beats. The median duration of the arrhythmic event was 47 seconds. An additional 3 patients developed nonsyncopal persistent III-degree AV block, and 2 patients had presyncope attributable to AV block with asystole. No patients suffered injury attributable to syncopal relapse.

CONCLUSIONS

In patients with BBB and negative electrophysiological study, most syncopal recurrences have a homogeneous mechanism that is characterized by prolonged asystolic pauses, mainly attributable to sudden-onset paroxysmal AV block.