Faculty Bibliography

STUDY OBJECTIVES: In familial dysautonomia (FD) patients, sleep-disordered breathing (SDB) might contribute to their high risk of sleep-related sudden death. Prevalence of central versus obstructive sleep apneas is controversial but may be therapeutically relevant. We, therefore, assessed sleep structure and SDB in FD-patients with no history of SDB. METHODS: 11 mildly affected FD-patients (28 +/- 11 years) without clinically overt SDB and 13 controls (28 +/- 10 years) underwent polysomnographic recording during one night. We assessed sleep stages, obstructive and central apneas (>/= 90% air flow reduction) and hypopneas (> 30% decrease in airflow with >/= 4% oxygen-desaturation), and determined obstructive (oAI) and central (cAI) apnea indices and the hypopnea index (HI) as count of respective apneas/hypopneas divided by sleep time. We obtained the apnea-hypopnea index (AHI4%) from the total of apneas and hypopneas divided by sleep time. We determined differences between FD-patients and controls using the U-test and within-group differences between oAIs, cAIs, and HIs using the Friedman test and Wilcoxon test. RESULTS: Sleep structure was similar in FD-patients and controls. AHI4% and HI were significantly higher in patients than controls. In patients, HIs were higher than oAIs and oAIs were higher than cAIs. In controls, there was no difference between HIs, oAIs, and cAIs. Only patients had apneas and hypopneas during slow wave sleep. CONCLUSIONS: In our FD-patients, obstructive apneas were more common than central apneas. These findings may be related to FD-specific pathophysiology. The potential ramifications of SDB in FD-patients suggest the utility of polysomnography to unveil SDB and initiate treatment. COMMENTARY: A commentary on this article appears in this issue on page 1583.

Cerebral autoregulation (CA) dampens transfer of blood pressure (BP)-fluctuations onto cerebral blood flow velocity (CBFV). Thus, CBFV-oscillations precede BP-oscillations. The phase angle (PA) between sympathetically mediated low-frequency (LF: 0.03-0.15Hz) BP- and CBFV-oscillations is a measure of CA quality. To evaluate whether PA depends on sympathetic modulation, we assessed PA-changes upon sympathetic stimulation with and without pharmacologic sympathetic blockade. In 10 healthy, young men, we monitored mean BP and CBFV before and during 120-second cold pressor stimulation (CPS) of one foot (0°C ice-water). We calculated mean values, standard deviations and sympathetic LF-powers of all signals, and PAs between LF-BP- and LF-CBFV-oscillations. We repeated measurements after ingestion of the adrenoceptor-blocker carvedilol (25mg). We compared parameters before and during CPS, without and after carvedilol (analysis of variance, post-hoc t-tests, significance: p<0.05). Without carvedilol, CPS increased BP, CBFV, BP-LF- and CBFV-LF-powers, and shortened PA. Carvedilol decreased resting BP, CBFV, BP-LF- and CBFV-LF-powers, while PAs remained unchanged. During CPS, BPs, CBFVs, BP-LF- and CBFV-LF-powers were lower, while PAs were longer with than without carvedilol. With carvedilol, CPS no longer shortened resting PA. Sympathetic activation shortens PA. Partial adrenoceptor blockade abolishes this PA-shortening. Thus, PA-measurements provide a subtle marker of sympathetic influences on CA and might refine CA evaluation.

BACKGROUND: Patients with a history of mild TBI (post-mTBI-patients) have an unexplained increase in long-term mortality which might be related to central autonomic dysregulation (CAD). We investigated whether standardized baroreflex-loading, induced by a Valsalva maneuver (VM), unveils CAD in otherwise healthy post-mTBI-patients. METHODS: In 29 healthy persons (31.3 +/- 12.2 years; 9 women) and 25 post-mTBI-patients (35.0 +/- 13.2 years, 7 women, 4-98 months post-injury), we monitored respiration (RESP), RR-intervals (RRI) and systolic blood pressure (BP) at rest and during three VMs. At rest, we calculated parameters of total autonomic modulation [RRI-coefficient-of-variation (CV), RRI-standard-deviation (RRI-SD), RRI-total-powers], of sympathetic [RRI-low-frequency-powers (LF), BP-LF-powers] and parasympathetic modulation [square-root-of-mean-squared-differences-of-successive-RRIs (RMSSD), RRI-high-frequency-powers (HF)], the index of sympatho-vagal balance (RRI LF/HF-ratios), and baroreflex sensitivity (BRS). We calculated Valsalva-ratios (VR) and times from lowest to highest RRIs after strain (VR-time) as indices of parasympathetic activation, intervals from highest systolic BP-values after strain-release to the time when systolic BP had fallen by 90 % of the differences between peak-phase-IV-BP and baseline-BP (90 %-BP-normalization-times), and velocities of BP-normalization (90 %-BP-normalization-velocities) as indices of sympathetic withdrawal. We compared patient- and control-parameters before and during VM (Mann-Whitney-U-tests or t-tests; significance: P < 0.05). RESULTS: At rest, RRI-CVs, RRI-SDs, RRI-total-powers, RRI-LF-powers, BP-LF-powers, RRI-RMSSDs, RRI-HF-powers, and BRS were lower in patients than controls. During VMs, 90 %-BP-normalization-times were longer, and 90 %-BP-normalization-velocities were lower in patients than controls (P < 0.05). CONCLUSIONS: Reduced autonomic modulation at rest and delayed BP-decrease after VM-induced baroreflex-loading indicate subtle CAD with altered baroreflex adjustment to challenge. More severe autonomic challenge might trigger more prominent cardiovascular dysregulation and thus contribute to increased mortality risk in post-mTBI-patients.

After mild traumatic-brain-injury (mTBI), patients have increased long-term-mortality-rates, persisting even beyond 13 years. Pathophysiology is unclear. Yet, central-autonomic-network dysfunction may contribute to cardiovascular dysregulation and increased mortality. Purely parasympathetic cardiovascular challenge by eyeball-pressure-stimulation (EP), might unveil subtle autonomic-dysfunction in post-mTBI-patients. We investigated whether mild EP shows autonomic-cardiovascular-dysregulation in post-mTBI-patients. In 24 patients (34+/-12years; 5-86 months post-injury) and 27 controls (30+/-11years), we monitored respiration, electrocardiographic RR-intervals (RRI), systolic- and diastolic-blood-pressure (BPsys, BPdia) before and during 2 minutes of 30mmHg EP, applied by an ophthalmologic ocular-pressure-device (Okulopressor(R)). We calculated spectral-powers of RRI in the mainly sympathetic low (LF: 0.04-0.15Hz) and parasympathetic high (HF: 0.15-0.5Hz) frequency-ranges, and of BP in the sympathetic LF-range, the RRI-LF/HF-ratio as index of the sympathetic-parasympathetic-balance, normalized (nu) RRI-LF- and HF-powers, and LF- and HF-powers after natural-logarithmic-transformation (ln). Parameters before and during EP in post-mTBI-patients and controls were compared by repeated measurement analysis of variance (ANOVA) with post-hoc analysis (significance: p<0.05). During EP, BPsys and BPdia increased in post-mTBI-patients. Only in controls but not in post-mTBI-patients, EP increased RRI-HFnu-powers and decreased RRI-LF-powers, RRI-LFnu-powers, BPsys-LF-powers, BPsys-lnLF-powers and BPdia-lnLF-powers. RRI-LF/HF-ratios slightly increased in post-mTBI-patients but slightly decreased in controls upon EP. Even with only mild EP, our controls showed normal EP-responses and shifted sympathetic-parasympathetic-balance towards parasympathetic predominance. In contrast, our post-mTBI-patients could not increase parasympathetic heart rate modulation but increased BP upon EP, indicating a paradox sympathetic activation. The findings support the hypothesis that central-autonomic-dysfunction might contribute to an increased cardiovascular risk, even years after mTBI.

Introduction: Familial dysautonomia (FD)-patients are at risk of sudden unexplained death, particularly during sleep. Respiratory abnormalities and reduced arousability might contribute to fatalities. Aim: To assess respiratory abnormalities and arousability in FD during sleep. Methods: 11 FD-patients (28 +/- 11 years) and 11 healthy persons (28 +/- 11 years) underwent polysomnographic recording during one night. We assessed sleep stages, apneas (>90% air flow reduction) and hypopneas (>30% decrease in airflow with >4% oxygen-desaturation). Arousals were defined as >3 sec abrupt shift in electroencephalographic frequencies to alpha- or theta-activity or frequencies >16Hz. We tested differences between FD-patients and controls by U-test or Fisher's exact test (significance: p < 0.05). Results: Percentage of sleep stages was similar in FD-patients and controls. 107 apneas occurred in 10 FD-patients. Apneas were followed by 74 oxygen-desaturations and 4 arousals. 9 Apneas were followed by desaturation and arousal. Only 5 apneas (p < 0.001) occurred in 2 controls (p > 0.05) and were followed by 2 oxygen desaturations (p=0.001) and 1 arousal (p > 0.05). No apneas were followed by desaturation and arousal. Hypopneas were the most frequent respiratory event and occurred primarily during sleep stage 1 and 2. In all FD-patients, we recorded 362 hypopneas with subsequent oxygen-desaturation that were followed by only 51 arousals. 12 hypopneas (p < 0.001) occurred in 3 controls (p=0.085) and were followed by 3 arousals (p=0.002)

BACKGROUND: Early repolarization pattern (ER) gained attention as a risk factor for ventricular arrhythmia and sudden cardiac death in the general population. While electrocardiographic abnormalities are frequent findings in stroke patients, data on ER pattern in this population are lacking. METHODS: We assessed the prevalence of ER pattern in consecutive acute stroke patients at a tertiary stroke center. Functional outcome after 90 days was analyzed to determine the effect of an ER pattern on mortality. Multivariate logistic regression analysis was used to identify factors associated with an ER pattern. RESULTS: Out of 1141 consecutive stroke patients 771 patients remained for analysis after application of exclusion criteria. ER was observed in 62 (8.04 %) patients. ER was more prevalent among subjects with intracerebral and subarachnoidal hemorrhage (13.0 %) than among patients with ischemic stroke (7.0 %; p = 0.024). Multiple regression analysis revealed QRS-duration (OR 0.972 95 % CI 0.950-0.994, p = 0.012), QT-duration (OR 1.009, 95 % CI 1.004-1.014, p = 0.001) and mechanical ventilation on admission (OR 0.320, 95 % CI 0.136-0.752, p = 0.009) as independent predictors for ER. Overall ER on admission was not associated with increased mortality at 3-month follow-up (ER 11.3 % vs. non-ER 9.2 %; p = 0.582). CONCLUSIONS: ER is frequently found among patients with acute cerebrovascular events and is more prevalent in patients with hemorrhagic compared to ischemic events. Our study yields no evidence that ER is associated with worse outcome or mortality after stroke.

Neurocardiological interactions can cause severe cardiac arrhythmias in patients with acute ischemic stroke. The relationship between the lesion location in the brain and the occurrence of cardiac arrhythmias is still discussed controversially. The aim of the present study was to correlate the lesion location with the occurrence of cardiac arrhythmias in patients with acute ischemic stroke. Cardiac arrhythmias were systematically assessed in patients with acute ischemic stroke during the first 72 h after admission to a monitored stroke unit. Voxel-based lesion-symptom mapping (VLSM) was used to correlate the lesion location with the occurrence of clinically relevant severe arrhythmias. Overall 150 patients, 56 with right-hemispheric and 94 patients with a left-hemispheric lesion, were eligible to be included in the VLSM study. Severe cardiac arrhythmias were present in 49 of these 150 patients (32.7 %). We found a significant association (FDR correction, q < 0.05) between lesions in the right insular, right frontal and right parietal cortex as well as the right amygdala, basal ganglia and thalamus and the occurrence of cardiac arrhythmias. Because left- and right-hemispheric lesions were analyzed separately, the significant findings rely on the 56 patients with right-hemispheric lesions. The data indicate that these areas are involved in central autonomic processing and that right-hemispheric lesions located to these areas are associated with an elevated risk for severe cardiac arrhythmias.

BACKGROUND: Growing evidence suggests that the heart rate (HR) at rest is an independent predictor of cardiovascular mortality. In ischemic stroke, continuous monitoring of HR is the standard of care, but systematic data on its dynamics and prognostic value during the acute phase are limited. METHODS: In this prospective observational study, HR was measured by continuous electrocardiographic monitoring on admission and during the first 72 hours of care among patients who were awake with ischemic stroke and survived until discharge. Functional outcome was assessed after 90 days. RESULTS: Data from 702 consecutive patients were analyzed (median age, 73 years, 54% men). The time course of HR was initially characterized by a rapid decline during the first 12 hours after admission. Among patients who survived until day 90, this was followed by a continuous downward trend in HR, whereas death after discharge was associated with a secondary increase and a reversal point 12 hours after admission. After adjustment for established risk factors, this secondary increase during the acute period was an independent predictor of death (hazard ratio, 3.73; 95% confidence interval, 1.47-9.43; P = .005). CONCLUSIONS: A secondary rise of HR during care for acute ischemic stroke is an early sign of fatality and may represent a surrogate for an unfavorable sympathetic disinhibition. Further research is warranted to clarify the role of targeted HR reduction after ischemic stroke (http://clinicaltrials.gov/, unique identifier NCT01858779).

OBJECTIVE: To investigate feasibility and diagnostic accuracy of measurement of the peripheral pulse (MPP) at the radial artery as a simple, noninvasive screening tool for paroxysmal atrial fibrillation (pAF) in patients after acute ischemic stroke. METHODS: Two hundred fifty-six patients with acute ischemic stroke and the patients' relatives at a tertiary stroke center were prospectively included. Participants were instructed for characteristics of atrial fibrillation (AF) in MPP using standardized educational material. Measurements of participants as well as a health care professional were then compared with simultaneous blinded ECG to evaluate diagnostic accuracy parameters. RESULTS: MPP by the health care professional or patients' relatives had a diagnostic sensitivity of 96.5% and 76.5%, respectively, with 94.0% and 92.9% specificity for the detection of AF. Self-measurements were reliably performed by 89.1% of competent patients with a diagnostic sensitivity of 54.1% and 96.2% specificity. False-positive results were limited to 6 cases (2.7%) with a positive predictive value of 76.9% and a negative predictive value of 90.0%. CONCLUSION: With a low rate of false-positive results, MPP offers an easy, ubiquitously available, noninvasive, first-step screening tool to guide ECG diagnostics for pAF after ischemic stroke. The data warrant a prospective trial evaluating the efficacy of MPP-guided ECG diagnostics in secondary prevention after stroke, which is now underway. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that MPP by patients or relatives accurately distinguishes AF from normal heart rhythm as compared with continuous ECG.