A novel growth-factor-dependent myeloid cell line derived from mouse bone marrow cells contains progenitors endowed with high proliferative potential

We describe two modified methods for median-to-ulnar motor conduction comparison in the diagnosis of median neuropathy at the wrist: the median-thenar to ulnar-thenar latency difference (TTLD), and the median-thenar to ulnar-hypothenar latency difference (THLD). We also describe an F-wave ulnar-to-median comparative test, the F-wave latency difference (FWLD). The abnormal cutoffs based upon 34 normal controls are: TTLD, 0.8 ms; THLD, 1.2 ms; FWLD, 0.6 ms. In 50 patients (79 hands) with clinically defined carpal tunnel syndrome and electrophysiological evidence of median neuropathy at the wrist (based upon a prolonged median nerve palm-wrist latency), the diagnostic sensitivities were: 95-98%, 85-88%, and 75-78%, respectively. These tests are therefore highly sensitive. They are easily performed and require minimal additional effort to incorporate into commonly used clinical electrodiagnostic routines. They may be advantageous when a concomitant polyneuropathy is present, and they may also help avoid technical pitfalls and aid in identification of anatomic variants.     

Oral fluoroquinolones for maintenance treatment of melioidosis

Fifty-three hands with carpal tunnel syndrome had pre- and postoperative evaluations of median nerve distal motor latency (from wrist to thenar muscles) and orthodromic sensory nerve conduction velocity (from thumb and middle finger to wrist). At 6 months we observed a neurophysiological return to normal in all cases with normal preoperative distal motor latency and in about 50% of the hands with preoperative distal motor latency between 4 and 6 ms. Prolongation of the distal motor latency over 6 ms was not followed by return to neurophysiological normality, although some degree of sensory function was restored in the majority of cases.     

Abdominal wall metastases in incidental gallbladder carcinoma--different incidence after laparoscopic and open surgery?

We investigated 303 diabetic patients in order to clarify the relationship between progression of diabetic polyneuropathy and conduction delay across the carpal tunnel. Distal latency ratio (DLR) was determined by comparison of distal motor latency of the median nerve with that of the ulnar nerve. Lower extremity polyneuropathy index (LPNI), expressed as a mean percentage of the normal for six indices over two nerves obtained by motor nerve conduction studies, was 82.9% on the average in the patients. Their DLR (1.44 +/- 0.24) was larger than the normal value (1.29 +/- 0.10). About 30% of the diabetics had abnormal DLR, especially in women its incidence was as high as 39%. The lower the LPNI level, the larger the incidence of abnormal DLR. In diabetic polyneuropathy patients peripheral nerves will become fragile, which might increase the incidence of conduction delay across the carpal tunnel. This phenomenon might also be called as 'double crush syndrome'.     

Normal median near nerve potential

In routine studies of sensory nerve conduction, only fibers > or = 7 microns in diameter are analyzed. The late components which originate from thinner fibers are not detected. This explains why a normal sensory action potential (SAP) may be recorded in patients with peripheral neuropathies and sensory loss. In the present study we investigated the late component of the median SAP with a near nerve needle electrode technique in 14 normal volunteers (7 men and 7 women), aged 34.5 +/- 14.8 years. The stimulus consisted of rectangular pulses of 0.2-ms duration at a frequency of 1 Hz with an intensity at least 6 times greater than the threshold value for the main component. Five hundred to 2000 sweep averagings were performed. The duration of analysis was 40 or 50 ms and the wave analysis frequency was 200 (-6 dB/oct) to 3000 Hz (-12 dB/oct). We used an apparatus with a two-channel amplifier system, 200 M omega or more of entry impedance and a noise level of 0.7 microVrms or less. The main component mean amplitude, conduction velocity and latency and the late component mean amplitude, conduction velocity and latency were respectively (mean +/- SD): 26.5 +/- 5.42 microV, 56.8 +/- 5.42 m/s, 3.01 +/- 0.31 ms, 0.12 +/- 0.04 microV, 16.4 +/- 2.95 m/s and 10.6 +/- 2.48 ms. More sophisticated equipment has an internal noise of 0.6 microVrms. These data demonstrate that the technique can now be employed to study thin fiber neuropathies, like in leprosy, using commercial electromyographs, even in non-academic practices.     

The predictive value of electrodiagnostic studies in carpal tunnel syndrome

In recent years, electrodiagnostic studies have become an expected component in the work up and evaluation of carpal tunnel syndrome. We conducted a retrospective review of 460 carpal tunnel decompressions to determine whether the accuracy of diagnosis and the prediction of therapeutic outcome could be related to the positivity and severity of findings on preoperative electrical studies. The 349 patients (460 hands) were divided into two groups: group 1 consisted of hands with the clinical diagnosis of carpal tunnel syndrome but with normal electrodiagnostic studies (n = 62); in group 2 the hands had a clinical diagnosis of carpal tunnel syndrome with confirmatory electrodiagnostic studies (n = 398). The number and distribution of signs and symptoms of carpal tunnel syndrome were not statistically different between these two groups. There was not a statistically significant difference in the success rate of surgery or the incidence of complications. The similarities between these two groups suggests that the distinction between them (the positivity of electrodiagnostic studies) is an artificial one and that the clinical diagnosis of carpal tunnel syndrome is sufficient to predict the presence of the disease, as well as outcome of surgery. On the basis of these data, strict adherence to electrodiagnostic studies to confirm the diagnosis will exclude 13 percent of the patients with legitimate carpal tunnel syndrome from receiving appropriate therapy.     

A comparison of traditional electrodiagnostic studies, electroneurometry, and vibrometry in the diagnosis of carpal tunnel syndrome

In 49 patients (98 hands), referred to an electrodiagnostic laboratory, assessments were made by conventional nerve conduction studies on the upper extremity and by two more portable modalities, namely electroneurometry (skin surface electrical stimulation of the motor nerve) and single-frequency (120 Hz) vibrometry. Tests were performed on median and ulnar nerves. Correlations with motor nerve conduction studies for each screening test on the median nerve were r = .81 for the electroneurometer and r = .48 for the vibrometer. When carpal tunnel syndrome was diagnosed either by clinical criteria only or by nerve conduction abnormality, the association with electroneurometry was characterized by high sensitivity and low specificity, while the opposite relationship prevailed with vibrometry. These associations were highly dependent on the methods used to select normal values from a reference population. While the manufacturer's recommended normal values offered good predictability, with thresholds that corresponded to nerve conduction studies, normal values generated in a more standard way produced much weaker and less useful associations. The selection of an appropriate electrical screening test for peripheral nerve injury, such as entrapment neuropathy, depends on the prevalence and seriousness of the target disease and the relative consequences of over- and underdiagnosis.     

A case of cortical reflex positive-negative myoclonus--electrophysiological study

An 11-year-old girl who had the positive-negative myoclonus and the history of the generalized tonic clonic seizure was electrophysiologically studied. She had no siblings with either myoclonus or epilepsy, and her intellectual level was normal. She had no other neurological deficits including ataxia, pyramidal and extrapyramidal signs. Surface EMG showed a brief increase in the EMG activity followed by the silent period associated with positive and negative myoclonus during sustained wrist extension. Giant SEP and C reflex (38.6 ms) following electric stimulation of the median nerve at the wrist were obtained in the resting condition and the silent period (about 180 ms) following C reflex was obtained during voluntary contraction. Jerk-locked back averaging of the EEG time-locked to the onset of the myoclonic discharge recorded from the right biceps muscle showed a cortical spike at the left central region preceding the myoclonus onset by 12.6 ms. The latency of C reflex in this case was very short compared with that of previously reported cortical reflex myoclonus. The estimated cortical delay between the arrival of the somatosensory volley and the motor cortex discharge responsible for the C reflex was -1.0 ms and this value was shorter than that in patients with typical cortical reflex myoclonus (mean 3.7 +/- 1.1 ms). Conditioning stimuli (C) of the right median nerve at the wrist started to facilitate the amplitude of the motor evoked potential recorded from the right abductor pollicis brevis muscle after magnetic test stimuli (T) of the left motor cortex at 20 ms of the C-T interval. This C-T interval was shorter than that (24.6 +/- 1.6 ms) in patients with the typical cortical myoclonus. These electrophysiological findings suggested the shorter reflex pathway of the cortical reflex myoclonus in this case than in typical cortical reflex myoclonus. We speculated that the myoclonus was based upon the direct sensory projection from the thalamus to the motor cortex in this case.     

Acetazolamide reduces peripheral afferent transmission in humans

Carbonic anhydrase has been localized in skeletal muscle and nerve, thus, inhibition with acetazolamide (ACZ) may alter nerve and/or muscle function in healthy humans. ACZ (3 oral doses 14, 8, and 2 h prior to testing) reduced isometric force (37%) and peak to peak electromyographic (EMG) amplitude (1.38 mV to 0.83 mV), while increasing EMG latency associated with a unilateral Achilles tendon-tap. Reflex recovery profiles, following a contralateral conditioning tap, were similar in both placebo and ACZ experiments. ACZ led to significant changes in Hmax/Mmax ratio (52.19/14.42 to 45.73/15.65) and H-reflex latency (34.18 +/- 2.54 ms to 35.24 +/- 2.74 ms). Motor nerve conduction velocity and maximal voluntary isometric torque (knee extensors) were unaltered by ACZ. These data suggest that inhibition of the tendon-tap reflex and associated isometric force, following ACZ, is related to impairment of synaptic integrity between la fibers of the muscle spindle and the alpha motor neuron and not impairment of the muscle spindle or force-generating capacity.     

Early diagnosis of carpal tunnel syndrome: comparison of sensory conduction studies of four fingers

Sensory studies of four fingers were performed on 72 patients with early (distal motor latency <4.2 ms) carpal tunnel syndrome (CTS) and on 43 control subjects. Results demonstrate that sensory studies of digit 4 yields the highest sensitivity (88%) for diagnosis of early CTS. The sensitivity of digit 1, digit 2, and digit 3 was 61%, 22%, and 50%, respectively.     

Hydroxylamine blocks adenosine A1 receptor-mediated inhibition of synaptic transmission in rat hippocampus

BACKGROUND AND PURPOSE: Stroke-induced hemiparesis involving the arm and hand results in regular, repeated overuse of the opposite hand and wrist. Because repetitive hand and wrist movement is a common cause of carpal tunnel syndrome (CTS), we examined the nonparetic upper limb in stroke patients for evidence of CTS. METHODS: We measured bilaterally sensory nerve conduction velocity (SNCV), motor nerve conduction velocity (MNCV), sensory nerve action potentials (SNAP) at the wrist, palm-to-wrist distal sensory latency (DSL), palm-to-wrist SNAP, compound motor action potentials (CMAP), and distal motor latency (DML) in stroke patients and control subjects. Controls were right-handed, >/=65 years old, lucid, independent in their activities of daily living, and had no disease known to cause CTS. Stroke patients were divided into a functioning hand group (n=61) and a disused hand group (n=71). All patients had hemiplegia. RESULTS: Tinel's sign was observed on the nonparetic side in 57.7% of patients with a disused hand and in 31.1% of those with a functioning hand. All electrophysiological indices were significantly more abnormal on the nonparetic side than on the hemiparetic side or in controls. Patients with a disused hand showed greater abnormality on the nonparetic side in SNCV, SNAP, palm-to-wrist DSL, DML, and CMAP than patients with a functioning hand. CONCLUSIONS: Overuse of the nonparetic hand and wrist of the nonparetic side may result in CTS in stroke patients, especially when the paretic hand is not functional. Wrist splinting or other prophylactic treatments beginning soon after stroke might help to prevent CTS.     

Peripheral nerve repair in the hand with and without motor sensory differentiation

To investigate the value of motor sensory differentiated nerve repair, we examined a group of 9 patients with motor sensory differentiated nerve repair and a group of 13 patients without motor sensory differentiated nerve repair. The clinical and electroneurographic findings were compared. For the clinical examination, Millesi's scoring system was used. The hand function after motor sensory differentiated median nerve repair was 72% +/- 16% compared with 57% +/- 14% without motor sensory differentiation. The hand function after motor sensory differentiated median and ulnar nerve repair was 53% +/- 12% compared with 43% +/- 24% without motor sensory differentiation. After ulnar nerve repair the achieved values for hand function were high even without motor sensory differentiation. Our results indicate that intraoperative motor sensory differentiation of injured nerves is helpful to reestablish particularly the sensory function in median nerve injuries.     

Entrapment neuropathies

Relative frequency of entrapment neuropathies was studied from amongst the patients referred to an electrodiagnostic medicine laboratory for electrophysiological studies. During the study period electrophysiological procedures were done on 650 patients with various peripheral nerve disorders. The entrapment neuropathies constituted 8.5%. Carpal tunnel syndrome (CTS) was the commonest entrapment neuropathy (83.6%). Diagnosis of CTS was established in 84 Patients referred with the diagnosis of CTS. Electrophysiological tests confirmed the diagnosis of thoracic outlet syndrome in 4 (15.4%) of the 26 patients referred with this diagnosis and in 5 (19.3%) of them the diagnosis turned out to be CTS. Diagnosis of cubital tunnel syndrome was not suspected clinically in all the 3 patients, they were referred with the diagnosis of ulnar neuropathy. In both the patients with tarsal tunnel syndrome the initial diagnosis was peripheral neuropathy.     

Peripheral motor and sensory nerve conduction studies in haemodialysis patients. A study of 54 patients

Peripheral motor and sensory nerve conduction velocities were studied prospectively in 54 chronic haemodialysis patients. The most sensitive parameters for the detection of polyneuropathy were the deep peroneal nerve motor conduction velocity, the sural nerve sensory conduction velocity and the H-reflex latency and H-index of the S1 roots. All patients examined were found to present at least one abnormal nerve conduction parameter. In the present study the side of the arteriovenous shunt had no statistically significant effect on the sensory and motor nerve conduction velocities in the upper extremities. There was a significant correlation between H-reflex latency and H-reflex index, and between H-reflex latency and sural nerve sensory conduction velocity.     

Pudendal neuropathy is predictive of failure following anterior overlapping sphincteroplasty

PURPOSE: This study assessed the efficacy of anterior overlapping sphincteroplasty and parameters predictive of a successful outcome. METHODS: Clinical findings and physiologic investigations of female patients who underwent anterior overlapping sphincteroplasty for fecal incontinence between 1988 and 1996 were reviewed. The extent of sphincter damage was assessed at needle electromyography as the number of quadrants exhibiting decreased motor unit potentials. Prolonged pudendal nerve terminal motor latencies were those of greater than 2.2 ms. The size of the endoanal ultrasound defect was assessed as degrees circumference of the external sphincter in which viable muscle was absent. Patients were reviewed by telephone questionnaire and were asked to grade the outcome of their surgery as excellent or good (success) or fair or poor (failure). Incontinence was graded using a scoring system of 0 (perfect continence) to 20 (complete incontinence). RESULTS: There were 100 patients who had an overlapping sphincteroplasty; complete follow-tip information was obtained for 77 patients at a median of 24 (range, 2-96) months. The median age was 47 (range, 25-80) years and they had a median duration of incontinence of four (range, 0.1-39) years. Prior sphincteroplasty had been performed in 30 patients with a median of one (range, 1-7) operations. Investigations performed included electromyography (n = 49), pudendal nerve terminal motor latency (n = 71), endoanal ultrasound (n = 49), and manometry (n = 67). Sixty percent of patients had improved continence and 42 (55 percent) considered their surgery to have been successful as attested to by a significant decrease in their incontinence score (from 15.1 +/- 4.5 to 4.3 +/- 4.2; P < 0.0001). Neither patient age, parity, prior sphincteroplasty, cause or duration of incontinence, extent of electromyography damage, size of the endoanal ultrasound defect, nor any manometric parameter correlated with outcome. However, 62 percent of 59 patients with bilaterally normal pudendal nerve terminal motor latencies had a successful outcome compared with only 16.7 percent of 12 patients with unilateral or bilateral prolonged pudendal nerve terminal motor latencies (P < 0.01). CONCLUSION: Bilateral normal pudendal nerve terminal motor latencies are the only factors predictive of long-term success after overlapping sphincteroplasty.     

A study of patients who leave without notice in an A & E department

Neuronal degradation accompanied with axonal degeneration has been known to occur in spinal motor neurons after an upper level of spinal cord lesion. In the present study, the functional integrity of neuromuscular transmission was assessed by utilizing a sensitive electrodiagnostic method comprising of stimulated single-fiber electromyography (SFEMG), along with axonal microstimulation, in paralytic muscles of patients with spinal cord injury (SCI). Neuromuscular jitter was measured in anterior tibial muscles for 30 patients with SCI and also for 12 normal controls. Mean jitter of 37.4 +/- 14.7 (mean +/- SD) micros, as obtained in SCI patients, was found to be significantly greater than the results of 20.1 +/- 8.4 micros in normal controls (P < 0.01). Jitter measurement was not significantly different in varied functional scales of SCI. A positive correlation was noted between the increased jitter and the disease duration from the onset of cord lesion till the time of stimulated SFEMG test (r = 0.68; P < 0.01). The present abnormal finding of neuromuscular jitter provides an electrophysiologic evidence for axonal degeneration and suggests that transsynaptic degeneration of motor neuron may occur below the level of cord lesion in SCI patients. Furthermore, the neuronal degradation in SCI was positively correlated with the course duration of the disease.     

Sensitivity of H-reflexes and stretch reflexes to presynaptic inhibition in humans

The sensitivity of soleus H-reflexes, T-reflexes, and short-latency stretch reflexes (M1) to presynaptic inhibition evoked by a weak tap applied to the biceps femoris tendon or stimulation of the common peroneal nerve (CPN) was compared in 17 healthy human subjects. The H-reflex was strongly depressed for a period lasting up to 300-400 ms (depression to 48 +/- 23%, mean +/- SD, of control at a conditioning test interval of 70 ms) by the biceps femoris tendon tap. In contrast, the short-latency soleus stretch reflex elicited by a quick passive dorsiflexion of the ankle joint was not depressed. The soleus T-reflex elicited by an Achilles tendon tap was only weakly depressed (92 +/- 8%). The H-reflex was also significantly more depressed than the T-reflex at long intervals (>15 ms) after stimulation of CPN (H-reflex 63 +/- 14%, T-reflex 91 +/- 13%; P < 0. 01). However, the short-latency (2 ms) disynaptic reciprocal Ia inhibition evoked by stimulation of CPN was equally strong for H- and T-reflexes (H-reflex 72 +/- 10%, T-reflex 67 +/- 13%; P = 0.07). Peaks in the poststimulus time histogram (PSTH) of the discharge probability of single soleus motor units (n = 53) elicited by an Achilles tendon tap had a longer duration than peaks evoked by electrical stimulation of the tibial nerve (on average 5.0 ms as compared with 2.7 ms). All parts of the electrically evoked peaks were depressed by the conditioning biceps femoris tendon tap (average depression to 55 +/- 27% of control; P < 0.001). A similar depression was observed for the initial 2 ms of the peaks evoked by the Achilles tendon tap (69 +/- 48%; P < 0.001), but the last 2 ms were not depressed. Conditioning stimulation of the CPN at long intervals (>15 ms) also depressed all parts of the electrically evoked PSTH peaks (n = 34; average 65%; P < 0.001) but had only a significant effect on the initial 2 ms of the peaks evoked by the Achilles tendon tap (85%; P < 0.001). We suggest that the different sensitivity of mechanically and electrically evoked reflexes to presynaptic inhibition is caused by a difference in the shape and composition of the excitatory postsynaptic potentials underlying the two reflexes. This difference may be explained by a different composition and/or temporal dispersion of the afferent volleys evoked by electrical and mechanical stimuli. We conclude that it is not straightforward to predict the modulation of stretch reflexes based on observations of H-reflex modulation.     

Dorsal horn cells connected to the lissauer tract and their relation to the dorsal root potential in the rat

We have examined the role of dorsal horn cells that respond to Lissauer tract stimulation in regulating primary afferent depolarization (PAD). PAD was monitored by recording the dorsal root potential (DRP) in the roots of the lumbar cord. Recordings were made of the discharges of Lissauer tract-responsive cells, and their discharges were correlated with the DRPs occurring spontaneously and those evoked by stimulation. Electrical microstimulation of the Lissauer tract (<10 microA; 200 micros) was used to activate the tract selectively and evoke a characteristic long-latency DRP. Cells that were excited by Lissauer tract stimulation were found in the superficial laminae of the dorsal horn. They exhibited low rates of ongoing discharge and responded to Lissauer tract stimulation typically with a burst of impulses with a latency to onset of 5.6 +/- 2.7 ms (mean +/- SD) and to termination of 13.6 +/- 4.1 ms (n = 105). Lissauer tract-responsive cells in L5 were shown to receive convergent inputs from cutaneous and muscle afferents as they responded to stimulation of the sural nerve (100%, n = 19) and the nerve to gastrocnemius (95%, n = 19). The latency of the response to sural nerve stimulation was 3.7 +/- 1.5 ms and to gastrocnemius nerve stimulation, 8.3 +/- 3.6 ms. Stimulation through a microelectrode at a depth of 1.5 mm in the sensorimotor cortex (100 microA, 200 micros) evoked a response in 17 of 31 Lissauer tract-responsive cells (55%) with a latency to onset of 21.9 +/- 2.8 ms (n = 17). Stimulation of the sural nerve, nerve to gastrocnemius or sensorimotor cortex was shown to depress the response of Lissauer tract-responsive cells to a subsequent Lissauer tract stimulus. The ongoing discharges of Lissauer tract-responsive cells were correlated to the spontaneous DRP using spike-triggered averaging. Of 123 cells analyzed in this way, 117 (95%) were shown to be correlated to the DRP. In addition, the peaks of spontaneous negative DRPs in spinally transected animals were detected in software. Perievent time histograms triggered from these peaks showed the discharge of Lissauer tract-responsive cells to be correlated to the spontaneous DRPs in 57 of 62 cells (92%) recorded. We conclude that these data provide compelling evidence that the Lissauer tract, and the dorsal horn cells that it excites, mediate the PAD evoked from multiple neural pathways.     

In vivo 1H MRS of normal breast and breast tumors using a dedicated double breast coil

OBJECTIVE: To characterize sleep patterns of patients with juvenile rheumatoid arthritis (JRA). METHODS: Sixteen patients with JRA aged 12+/-4 years and 9 controls aged 11+/-3 years underwent a comprehensive evaluation by self-report questionnaire and formal all night polysomnographic recordings. Multiple sleep latency test was performed in 7 patients. RESULTS: Patients had 90% more arousals and awakenings (p<0.01) and the median length of occurrences of uninterrupted sleep in stages 2 and 3 and rapid eye movement (REM) sleep was 60% shorter than in controls (p<0.01). The overall amount of sleep stage shift from deeper to lighter sleep was 23.5+/-10.8 events in patients compared to 14.9+/-4.0 in controls (p<0.05). In 15 of 16 patients 15% of non-REM sleep consisted of alpha-delta (alpha-rating) sleep, compared with less than 1% in controls (p<0.001). Multiple sleep latency test for patients was 10.3+/-2.6 min. There were no differences between JRA and controls in self-reported questions. However, patients reported longer afternoon naps, 1.8+/-1.3 h compared to 0.3+/-0.8 h in controls (p<0.05). CONCLUSION: Objective polysomnographic evidence of abnormal sleep has been confirmed in patients with JRA. Sleep disturbance was associated with daytime sleepiness as evidenced by abnormal multiple sleep latency test and longer afternoon naptime.     

Prolongation of conduction time during premature stimulation in the human atrium is primarily caused by local stimulus response latency

BACKGROUND: Conventional clinical electrophysiological techniques cannot accurately differentiate between local stimulus response latency and propagation time of the atrial response. The purpose of this study was to identify and distinguish local stimulus response latency from impulse propagation time in the human right atrium during programmed electrical stimulation. METHODS: Pacing was performed from two atrial sites (high and low right atrium) in 19 patients, using monophasic action potential recording/pacing combination catheters (interelectrode distance < 2 mm). Local stimulus response latency (interval between stimulus artifact and upstroke of the local monophasic action potential), and propagation time (interval between local and remote monophasic action potential upstroke) were evaluated at a basic cycle length (S1-S1) of 600 ms and as a function of the extrastimulus proximity (interval between extrastimulus and effective refractory period). Data are presented as means +/- SEM. RESULTS: During basic stimulation, local latency was very small (3.8 +/- 1.7 ms). During premature extrastimulation (proximity < 70 ms), local latency increased progressively with decreasing coupling intervals. Prolongation of local latency was most pronounced during stimulation close to the effective refractory period with local stimulus response latency increasing to 18.3 +/- 1.4 ms (380 +/- 7.9%) at 10 ms proximity (P < 0.002) and to 27.9 +/- 3.7 ms (630 +/- 13.2%) at 5 ms proximity, respectively (P < 0.0001). The impulse propagation time between the stimulation site and the remote recording site was on average 54.5 +/- 14.3 ms during basic stimulation, and increased up to 62.1 +/- 13.5 ms (14.0 +/- 8.4%), which was not significant. CONCLUSIONS: The intra-atrial impulse propagation remained essentially unchanged during the entire range of premature stimulation. Local stimulus response latency was negligible and constant during late coupling intervals but increased dramatically when extrastimulation approached the preceding repolarization phase. This has the following clinical impact: first, local stimulus response latency during premature extrastimulation curbs the targeted atrial response interval second, local stimulus response latency, not propagation time, seems responsible for the greater functional than effective refractory period during electrical stimulation; third, local stimulus response latency should be considered in pace mapping for accurate comparison of conduction time before pacing with that during pacing.     

Dependency on atrial electrophysiological properties of appearance of paroxysmal atrial fibrillation in patients with Wolff-Parkinson-White syndrome: evidence from atrial vulnerability before and after radiofrequency catheter ablation and surgical cryoablation

The pathogenesis of paroxysmal atrial fibrillation in patients with Wolff-Parkinson-White syndrome and the effects of elimination of accessory pathways on the appearance of atrial fibrillation are still controversial. Fifty-four patients with Wolff-Parkinson-White syndrome were classified into three groups: a No AF group (n = 24), patients without paroxysmal atrial fibrillation; an RF-AF Group (n = 12), patients with paroxysmal atrial fibrillation whose accessory pathways were eliminated using radiofrequency catheter ablation; and a Cryo-AF Group (n = 18), patients with paroxysmal atrial fibrillation whose accessory pathways were eliminated with surgical cryoablation. The electrophysiological characteristics of each group were evaluated prior to and following the elimination of their accessory pathways. As indices of atrial vulnerability, the presence of fragmented atrial activity and repetitive atrial firing zones were assessed. Inducibility of atrial fibrillation was significantly reduced following ablation of accessory pathways in the Cryo-AF group (83.3%-5.6%, P < 0.0001), while it was unchanged in the RF-AF group (83.3%-75%). In preablation studies, the effective refractory periods of the atrium in the RF-AF group and the Cryo-AF group were significantly shorter compared with the No AF group (204 +/- 18 ms, 197 +/- 16 ms vs 246 +/- 44 ms, respectively, P < 0.0001). Following ablation, the effective refractory period for patients in the Cryo-AF group was significantly prolonged compared with before ablation (197 +/- 16 ms to 232 +/- 24 ms, P < 0.0001). As a result of this prolongation of the effective refractory period of the atrium, the fragmented atrial activity and repetitive atrial response zones narrowed following ablation in the Cryo-AF group, but not in the RF-AF group. Therefore, the pathogenesis of atrial fibrillation in patients with Wolff-Parkinson-White syndrome may depend on the refractory period of the atrium rather than on the presence of accessory pathways.