[Postural deficits and risk of falling in elderly persons with incipient osteoporosis]. / Posturale Defizite und Sturzrisiko bei älteren Personen mit Verdacht auf Osteoporose.

BACKGROUND: Falls and fall-dependent complications represent major problems in geriatrics. Approximately 80-90% of femoral neck fractures in postmenopausal women are caused by falls. STUDY QUESTION: The goal of this study was to evaluate a new posturographic measurement system (Interactive Balance System, IBS) regarding its potential to predict falls in osteoporotic patients. MATERIALS AND METHODS: A total of 228 patients admitted for osteodensitometry because of suspected osteoporosis were included in the study. During the baseline investigation, bone density and postural regulation were measured. Over a follow-up period of 12 months, all falls were recorded in a fall diary. Participants with more than two falls per year were classified as persons at high risk of falling. RESULTS: In patients with confirmed osteoporosis (n=139), the posturographic frequency range F(2-4) was found to be predictive for falls. The ROC analysis of the dependent fall index FIOR(F2-4) showed an AUC value of 0.88. CONCLUSION: IBS is an effective assessment for fall prediction in osteoporosis. Especially peripheral-vestibular regulation mechanisms seem to be of great importance in the evaluated patient group.

[The impact of different sports on posture regulation]. / Der Einfluss unterschiedlicher Sportarten auf die Haltungsregulation.

BACKGROUND: Previous work has suggested that both the level of activity and the type of sport may have a major impact on postural control. However, no systematic investigation has been performed regarding the various types of professional sports. Particularly, the impact of competitional sports on the postural subsystems has not been elucidated so far. OBJECTIVE: The aim of this study was to investigate the influence of the major professional sport types, such as handball, gymnastics, swimming, and shooting, on the subsystems of postural control. We also tested the hypothesis that specific types of sport have specific effects on postural regulation. METHODS: 155 competitive male and female athletes (handball: n = 30; gymnastics: n = 44; swimming: n = 50; shooting: n = 31), and 34 age- and gender-matched controls were investigated using the Interactive Balance System (IBS; Tetrax Inc., Ramat Gan, Israel). The following spectral and time-domain indices were determined: power in the following frequency bands: P(F1) (0.03 - 0.1 Hz), P(F)(2 - 4) (0.1 - 0.5 Hz), P(F)(5 - 6) (0.5 - 1.0 Hz), P(F)(7 - 8) (> 1.0 Hz), stability index (STABI), and synchronisation index (SYN). RESULTS: Shooting athletes exhibited significantly smaller values of P(F1) (p = 0.003), P(F)(2 - 4) (p < 0.001), and P(F)(7 - 8) (p = 0.002), respectively, than the other athletes investigated. Also, the shooting athletes exhibited the smallest STABI values (p = 0.002). In contrast, the gymnasts showed the largest SYN values (p = 0.002). CONCLUSIONS: Different types of competitive sports exert different effects on the various subsystems of posture control, where especially shooting competitors demonstrate a significantly better posture regulation. Those effects can be parameterised and quantified with the IBS which thus enables an efficient and purposeful training. Furthermore, the IBS is highly suitable for aptitude screening in sports with high posture regulatory demands (shooting competitions, gymnastics, diving etc.).

[Impact of therapeutic riding on gait and posture regulation]. / Der Einfluss des Therapeutischen Reitens auf den Gang und die Haltungsregulation.

BACKGROUND: Hippotherapy has become an important therapeutic option in patients suffering from motoric dysfunction. The physiologic basis of this approach is the three-dimensional transmission of the horse's motion onto the patients body. These motion stimuli are believed to exert possitve effects on the patients's postural control systems. AIM: To test the hypothesis that hippotherapy has both positive short- and lang-term effects on gait and posture control of persons suffering from motoric disabilities. METHODS: Twenty-two children and adolescents aged 9.69 +/- 4.01 years (range: 9.69 +/- 4.01 years) with motoric dysfunctions were included in a prospective matched control study. In each participant, gait and posture control were investigated on four different occasions (O1 - O4) using the Interactive balance system (IBS; Tetrax Inc., Ramat Gan, Israel) and the portable gait analysis sytem RehaWatch (Hasomed, Magdeburg, Germany). The dates of gait and posture analysis were defined as follows: O 1: immediately prior to first therapeutic riding session (TRS); O 2: immediately after first TRS; O 3: after the last day of an eight weeks period of daily TRS; O 4: seven weeks later after a TRS free interval. RESULTS: The following parameters were slightly improved (adjusted significance level of p < 0.003) after eight weeks of therapeutic riding: (O1 vs. O 3): (1) walking distance (p = 0.009, eta(2) = 0.339); (2) pace frequency (p = 0.007, eta(2) = 0.358); (3) walking speed (p = 0.006, eta(2) = 0.367), and (4) time of attachment (p = 0.007, eta(2) = 0.360). The only short-term effect observed was a significant decrease of the attachment phase (p = 0.002, eta(2) = 0.387). Interestingly, gait symmetry remained unaffected. Posturography (adjusted significance level of p < 0.01) at O 1 versus O 2 (short-term) showed a significant decrease of the performance of both the visual-nigrostriatal subsystem (p < 0.001) and the somato-sensory subsystem (p = 0.001). At O 1 versus O 3 (long-term), the following parameters were sharply decreased: (1) postural stability (p = 0.011), and (2) somatosensory performance (p = 0.011). CONCLUSIONS: In the individuals investigated, an eight weeks series of therapeutic riding did not improve posture control and had only a small positive effect on gait performance. The reasons for these rather disappointing results could have been the low number of therapeutic riding sessions (0.5 sessions per week), and the relatively short duration (30 min) of each session. It remains to be seen, whether a higher density and longer duration of therapeutic riding sessions yields better results.

[Specific riding styles are associated with specific effects on bodily posture control]. / Einfluss unterschiedlicher Reitdisziplinen auf die Haltungsregulation.

BACKGROUND: The assessment of body posture control can be time consuming and cumbersome due to the complexity and the multimodal influence of a multiply influenced system. Various types of equine paces, such as stepping, trotting or galloping, result in acceleration and deceleration forces of different magnitude. These forces induce, in the horseman, reflexes that mediate motor activity to sustain posture balance and counterbalance the gravitational pull. However, there is a paucity of real life data regarding the extent of the various postural subsystems that are recruited to control postural balance in specific equine disciplines, such as classical dressage, show jumping, or vaulting. This study was conducted to bridge that gap. AIM OF THE STUDY: The aim of this explorative study was to identify the types of the postural subsystems involved in balance control and assess the magnitude of their activities during classical dressage, show jumping, vaulting, and versatility riding. METHODS: 144 horseback riders (8.1 % males) aged 17.3 +/- 2.9 years and 38 age matched controls (non riders) were investigated. The riders studied were competing in dressage, show jumping, vaulting, and versatility. In each individual, postural control was investigated by means of the "interactive balance system (IBS)" that enabled us to determine the spectral power in the following four standard frequency bands: F 1 (0.03 - 0.1 Hz), F 2 - 4 (0.1 - 0.5 Hz), F 5 - 6 (0.5 - 1.0 Hz), and F 7 - 8 (1.0 - 3.0 Hz). In addition, three motorical output indices were calculated: heel-to-toe-ratio (HTR), synchronization of feet (SYNC), and the global stability index of postural balance (STAB). Furthermore, each individual was interviewed regarding riding time, frequency and discipline and also about other sports activities and disorders of health. RESULTS: The mean training period of the horseback riders was 122 +/- 45.8 months, and mean weekly frequency of training was 5.5 +/- 1.8 days per week. Balance control was most effective in dressage and vaulting riders and least effective in show jumping competitors: HTR was 51 +/- 8 % (dressage), 48 +/- 8 % (show jumping), 47 +/- 8 % (versatility), 51 +/- 7 % (vaulting); SYNC was 523 +/- 124a. i. (dressage), 497 +/- 156a. i. (show jumping), 468 +/- 155a. i. (versatility), 589 +/- 126a. i. (vaulting). Spectral analysis revealed significantly higher power in F 1, F 2 - 4, and F 7 - 8 in dressage competition than in the other equestrian disciplines but not compared with the controls. Significantly differences between riders versus non riders were only found in HTR (p = 0.045) und SYNC (p = 0.009). CONCLUSIONS: Balance control was most effective in dressage and vaulting riders and least effective in the show jumping competitors. Thus, except for dressage and vaulting, our results do not suggest a positive effect of traditional riding styles on postural stability and control.

Electrocardiographic characteristics in patients with nonrheumatic atrial fibrillation and their relation to echocardiographic parameters.

The aim of this study was to determine the relation between (1) ECG fibrillatory wave amplitude and left atrial diameter and left atrial appendage (LAA) flow velocity using different ECG recording techniques, and (2) ECG fibrillatory frequency and frequency of LAA contractions in patients with nonrheumatic AF. In 36 patients (22 men, 14 women, mean age 61 +/- 11 years) with persistent AF, ECG recordings were performed using a standard 12-lead EGG and an orthogonal EGG lead system using a high gain, high resolution ECG. AF was classified as coarse (fibrillatory amplitude > or = 1 mm) orfine (fibrillatory amplitude < 1 mm) in leads I, aVF, V1 and corresponding leads X, Y, and Z. Fibrillatory frequency from the ECG was determined by subtracting averaged QRST complexes and applying a Fourier analysis to the resulting signal. Doppler flow was obtained from LAA during transesophageal echocardiography and LAA emptying velocity was determined. Fourier analysis was also applied to the Doppler signal generating the frequency of LAA contractions. Coarse AF was observed in 0, 9, and 18 patients in leads I, aVF, and V, respectively. It was more often (P < 0.05) detected in corresponding leads X (n = 13), Y (n = 31), and Z (n = 23). Fine AF in lead X was associated with a reduced LAA velocity (33 +/- 16 cm/s in coarse AF vs 22 +/- 13 cm/s in fine AF, P = 0.05). There was neither a relation between AF coarseness in any other ECG lead and LAA flow velocity, left atrial diameter, or echo contrast. In 25 patients with an active LAA flow, the mean frequency of LAA contractions was 6.8 +/- 0.8 Hz. The corresponding mean frequency obtainedfrom the EGG was 6.7 +/- 0.7 Hz (r = 0.85, P < 0.001). The mean difference between these two measures was 0.04 Hz, and the 95% confidence limits were 0.90 and- 0.82 Hz using the Bland-Altman method. In conclusion, AF coarseness and its relation to LAA flow velocity depend on the ECG recording technique used. LAA contractions represent one mechanical correlate of the electrical fibrillatory activity in AF.

Response of atrial fibrillatory activity to carotid sinus massage in patients with atrial fibrillation.

In some cases carotid sinus massage (CSM) may induce AF, whereas it may terminate AF in others. The purpose of this study was to investigate the influence of CSM on atrial fibrillatory frequency using spectral analysis of the surface ECG. Continuous ECG recordings were made in 19 patients (12 men, 7 women, mean age 61 +/- 11 years) with AF. Unilateral CSM was performed in the standard fashion to one randomized bifurcation of the carotid artery at a time. Ventricular rate and fibrillatory frequency were assessed in 30-second ECG segments at baseline and during CSM. The frequency content of the fibrillatory baseline was quantified using digital signal processing (filtering, subtraction of averaged QRST complexes, and Fourier transformation). CSM resulted in a relative change in fibrillatory frequency of 4.5 +/- 3.9% (range 0%-13%). In 8 (42%) patients an increase in fibrillatory frequency was found (6.4 +/- 0.5 vs 6.8 +/- 0.5 Hz, P = 0.012). In 9 (47%) patients a decrease in fibrillatory frequency occurred (6.5 +/- 0.8 vs 6.1 +/- 0.8 Hz, P = 0.008) without AF termination. The remaining two patients showed no change in fibrillatory frequency. CSM on the contralateral side after 2 minutes produced fibrillatory frequency changes in the same direction in all patients with a good reproducibility in its magnitude (r = 0.59, P = 0.05). Calcium channel blockers were more frequently used (78% vs 25%, P = 0.044) in patients with a decrease in fibrillatory frequency compared to patients with a frequency increase. There were no significant changes in ventricular rate during CSM. In conclusion, two different responses of atrial fibrillatory frequency to CSM were found. This might explain why CSM may facilitate AF induction in some cases and AF termination in others. Calcium channel blocker treatment may prevent an increase in fibrillatory frequency provoked by CSM suggesting a blunted electrical remodeling process.

Circadian variations in atrial fibrillatory frequency in persistent human atrial fibrillation.

Atrial fibrillatory frequency reflects the atrial refractory period during AF. This study was conducted to investigate noninvasively the diurnal fluctuations of fibrillatory frequency in persistent human atrial fibrillation and to determine the relationship between changes in ventricular rate and fibrillatory frequency. Ambulatory ECGs were recorded in 30 patients (18 men, 12 women, mean age 60 +/- 11 years) with persistent AF (> 24 hours). AF frequency was measured in 1-minute ECG segments by subtracting averaged QRST complexes and applying Fourier analysis to the resulting signals at 4 PM, 10 PM, 4 AM, and 10 AM. Peak frequency was determined in the 3-12 Hz frequency band. Mean fibrillatory frequency measured 6.6 +/- 0.6 Hz (range 5.0-7.8 Hz). Two different frequency patterns were distinguished comparing maximal diurnal versus nocturnal fibrillatory frequency. In six (20%) patients an increase (P = 0.045) in nocturnal fibrillatory frequency (type I) was found. In the remaining 24 (80%) patients a decrease (P < 0.001) in fibrillatory frequency occurred (type II). Type I AF showed a strong inverse correlation between relative changes (percent) in ventricular rate and fibrillatory frequency obtained from two consecutive measurement points (r = -0.88 to -.97, P < 0.01), whereas in type II AF a moderate positive correlation (r = 0.36 to 0.41, P < 0.05) was detected. These data indicate a circadian pattern in AF frequency that concurs with ventricular rate changes suggesting a modulating influence of the autonomic nervous system on atrial electrophysiology in persistent human AF.

[Technical and practical aspects of T-wave alternans testing]. / T-Wellen-Alternans: vom Rauschen zum Signal, vom Signal zur Prognose.

Alternation of the amplitude of the repolarization wave (T-wave) of the body surface ECG, usually referred to as T-wave alternans (TWA), has become one of the most important noninvasive tools in cardiac risk stratification. In earlier experimental and clinical studies TWA was shown to predict an individual's susceptibility of ventricular tachyarrhythmias. Recently, a number of prospectively designed clinical studies have confirmed these results and demonstrated that a positive TWA result in high risk populations, such as post-myocardial infarction patients and individuals suffering from congestive heart failure, is a very useful prognostic marker heralding sudden cardiac death due to ventricuar tachyarrhythmias. Moreover, experiments, performed in animals as well as in computer models, have shown that T-wave alternans may also be mechanistically involved in arrhythmogenesis. Since it has now become possible to measure TWA completely noninvasively by menas of exercise testing, an exponential increase in TWA tests has been observed. However, little information on the technical aspects of TWA testing is available. Therefore, in this article, technical and practical aspects of TWA assessment and interpretation are reviewed as far as they are relevant for clinicians.

Non-invasive assessment of fibrillatory activity in patients with paroxysmal and persistent atrial fibrillation using the Holter ECG.

OBJECTIVE: Automatic analysis of the frequency content of the fibrillatory baseline on the surface ECG accurately reflects the average rate of atrial fibrillation (AF). This frequency measurement correlates with the behavior of AF and predicts the response to administration of ibutilide, a new antiarrhythmic drug. Neither the temporal pattern of fibrillatory frequency in spontaneous paroxysmal or persistent AF, nor its response to chronic antiarrhythmic medication has been studied so far. METHODS AND RESULTS: Holter ECG recordings were made in 20 patients during AF. One minute ECG segments were selected for analysis. The frequency content of the fibrillatory baseline was then quantified using digital signal processing. After high-pass filtering, the QRST complexes were subtracted using a template matching algorithm. The resulting fibrillatory baseline signal was subjected to Fourier transformation, displayed as a frequency power spectrum and the peak frequency (f) was determined. In 11 patients (7 male, 4 female, age 62 +/- 10 years) 31 paroxysmal AF episodes were analyzed. Duration ranged from 1 min to 665 min (115 +/- 175 min). Initial mean peak f measured 5.1 +/- 0.7 Hz (range 3.9 to 6.9 Hz). There was a positive correlation between f and AF duration (R = 0.53, p = 0.002). AF of less than 15 min duration (n = 13) showed a lower f (4.8 +/- 0.6 Hz) when compared with longer lasting episodes (n = 18, 5.3 +/- 0.7 Hz, p = 0.03). In short AF episodes f was constant, whereas in longer-lasting episodes f increased to 5.8 +/- 0.5 Hz (p < 0.001) within 5 min. In 9 patients (9 male, age 58 +/- 8 years) with persistent AF oral antiarrhythmic drugs (amiodarone n = 5, sotalol n = 3, flecainide n = 1) were given prior to electrical cardioversion for prophylaxis of AF recurrence. Frequency measurements were obtained at baseline and 3 to 5 days after initiation of drug administration. At baseline mean f measured 6.9 +/- 0.4 Hz. Frequency was reduced by antiarrhythmic drugs to 5.8 +/- 0.4 Hz (p < 0.001). CONCLUSIONS: (1) The duration of paroxysmal AF episodes can be predicted using spectral analysis of ECG recordings of AF episodes. (2) An increase in fibrillatory frequency is associated with AF persistence. (3) This technique can be used to monitor the response to antiarrhythmic medication.

An increase in sinus rate following radiofrequency energy application in the posteroseptal space.

An increase in sinus rate has been previously described in patients with AV node reentry (AVNRT) following successful AV node modification. This increase could either be a specific sign of elimination of slow pathway conduction or it could be a consequence of energy application in the posteroseptal area. Thus, we compared the changes in sinus cycle length following successful slow pathway ablation (defined as complete elimination of dual AV node physiology) in patients having AVNRT with those in patients undergoing successful ablation of a posteroseptal atrioventricular accessory connection. Twenty five patients (16 women and 9 men, mean age 41 +/- 4 years) with typical AVNRT (cycle length 378 +/- 12 ms) and 29 patients (16 women and 13 men, age 34 +/- 5 years) with an accessory connection (17 manifest and 12 concealed) were studied. The electrophysiology study was performed during sedation with Fentanyl and Midazolam. The mean number of energy applications was 3 +/- 1 for successful slow pathway ablation and 4 +/- 1 for successful ablation of the accessory connection (p:NS). Following the successful energy application, the sinus cycle length decreased significantly 776 ms at baseline to 691 ms in patients with AVNRT. Following successful ablation of the posteroseptal AC, sinus cycle length decreased from 755 ms at baseline to 664 ms (p < 0.05 in both groups [difference between groups not significant]). The decrease in sinus cycle length did not correlate with the number of RF energy applications required for successful ablation or the total energy delivered. In conclusion, ablation of the AV node slow pathway and a posteroseptal accessory connection results in similar increases in the sinus rate. Thus, the increase in sinus rate is probably due to energy application in the posteroseptal space, possibly due to concomitant destruction of vagal inputs, and it is not specific for elimination of slow pathway conduction.

Pathophysiological mechanisms of dominant and recessive KVLQT1 K+ channel mutations found in inherited cardiac arrhythmias.

The inherited long QT syndrome (LQTS), characterized by a prolonged QT interval in the electrocardiogram and cardiac arrhythmia, is caused by mutations in at least four different genes, three of which have been identified and encode cardiac ion channels. The most common form of LQTS is due to mutations in the potassium channel gene KVLQT1, but their effects on associated currents are still unknown. Different mutations in KVLQT1 cause the dominant Romano-Ward (RW) syndrome and the recessive Jervell and Lange-Nielsen (JLN) syndrome, which, in addition to cardiac abnormalities, includes congenital deafness. Co-expression of KvLQT1 with the IsK protein elicits slowly activating potassium currents resembling the cardiac Iks current. We now show that IsK not only changes the kinetics of KvLQT1 currents, but also its ion selectivity. Several mutations found in RW, including a novel mutation (D222N) in the putative channel pore, abolish channel activity and reduce the activity of wild-type KvLQT1 by a dominant-negative mechanism. By contrast, a JLN mutation truncating the carboxyterminus of the KvLQT1 channel protein abolishes channel function without having a dominant-negative effect. This fully explains the different patterns of inheritance. Further, we identified a novel splice variant of the KVLQT1 gene, but could not achieve functional expression of this nor of a previously described heart-specific isoform.

50 years of successfull human defibrillation. A history of continuing progress.

50 years ago, Claude Beck successfully performed the first cardiac defibrillation in a human. This was the beginning of a new era in cardiology as well as in general medicine. Today, defibrillation or cardioversion measures in the context of resuscitation or performed as an elective procedure is a well-established technique and every physician is familiar with it. However, 50 years ago when Beck saved the life of a 14 year old boy in the operating room, little was known about defibrillation and its therapy. This article is in memoriam of Claude Beck, who drawing the right conclusions from published experimental observations, did the right thing at the right time. The circumstances of the first human defibrillation are described and the theoretical and experimental framework available at that time is discussed.

Permanent epicardial and transvenous single- and dual-chamber cardiac pacing in children.

Between January 1974 and November 1991 33 children received a permanent single- or dual-chamber pacing system, mainly because of postoperative high-degree AV block. The children were followed up retrospectively for pacemaker- and lead-related complications, and for differences between epi- and endocardial stimulation. The overall rate of lead related complications was 35% and did not differ significantly between the epi- and endocardially paced groups, although it tended to be somewhat higher in the epicardially paced children, mainly due to a higher rate of exit blocks in the latter. The epicardially stimulated patients exhibited a significantly higher rate of pacemaker-related complications, which was primarily accounted for by a higher frequency of battery depletions in the epicardial systems. The most impressive differences between both groups, however, was seen with respect to subacute and chronic energy consumption. Chronic energy drain in the epicardially paced patients amounted to almost the sixfold of that seen in the endocardially stimulated children. This resulted in a significantly shorter cumulative pacemaker survival in the epicardial group. Therefore, it is concluded that, whenever possible, the transvenous approach be used in children and small infants too. However, as a rule, in the latter transvenous dualchamber pacing is usually not feasible. In these cases rate-adaptive single-chamber pacing has evolved as a reasonable alternative for improving hemodynamics as well as quality of life. In epicardial pacing the use of pulse generators allowing bidirectional telemetry is advisable. In this way monitoring of lead impedance and battery status can be performed noninvasively, thus permitting individualization of pulse widths and amplitude setting, which is important with respect to energy conservation.

Is epicardial dual chamber pacing a realistic alternative to endocardial DDD pacing? Initial results of a prospective study.

Seventeen patients, in whom an epicardial (n = 7) or a transvenous DDDM pacemaker system had been implanted between June 1988 and October 1990, were followed up for pacemaker and lead related complications, pacemaker longevity, and electrophysiological lead parameters. The mean follow-up interval was 18 +/- 12 months, maximum 34 months. There were no differences in chronic atrial and ventricular sensing thresholds between epicardial and endocardial stimulation, nor were there any differences concerning lead related complications between the two pacing modalities. However, atrial as well as ventricular chronic stimulation thresholds were significantly higher with epicardial stimulation resulting in a twofold increase in atrial energy consumption and a threefold increase in the ventricular energy consumption. Thus, in one patient with an epicardial DDD system, the pacemaker had to be replaced prematurely because of battery depletion. It is concluded that epicardial DDD stimulation can be reliably performed as far as atrial and ventricular sensing is concerned, but that the energy requirements of available myocardial leads are not satisfactory for making optimal use of modern pacemaker capability.