Wolff-Parkinson-White syndrome in a man presenting with palpitation – A case report

Wolff-Parkinson-White (WPW) syndrome is not a common presentation, but physicians get to see cases with pre-excitation syndrome. WPW is characterized by the existence of an accessory pathway that predisposes patients to tachyarrhythmias and sudden death. Patients with WPW syndrome are at greater risk of hazardous ventricular arrhythmias. The majority of the cases never present with an underlying structural cardiac disease. It is always controversial to manage asymptomatic patients with WPW syndrome. Here, we discuss an uncommon case of a 48-year-old man with WPW syndrome after being evaluated for palpitation and giddiness.

Bloqueo de rama alternante en una taquicardia supraventricular: ¿Cuál es el mecanismo subyacente? / Alternating bundle branch block in a supraventricular tachycardia: Which is the mechanism ?

El bloqueo de rama funcional durante una taquicardia supraventricular puede ser observado con longitudes de ciclo cortas y representa una respuesta fisiológica del sistema de conducción intraventricular por la existencia de conducción nodal auriculo ventricular acelerada. Presentamos el caso de un paciente joven con taquicardia reentrante aurículo-ventricular ortodrómica y bloqueo de rama alternante. Esta respuesta infrecuente se explica por el hallazgo obtenido durante el estudio electrofisiológico. Una conducción nodal aurículo-ventricular acelerada produce un frente de onda que despolariza las ramas durante sus períodos refractarios. Una vez que ocurrió el bloqueo en una de las ramas, dicho bloqueo persistió debido al fenómeno de linking, que es por conducción oculta retrógrada repetitiva de la rama contralateral. Después de la ablación transcatéter de una vía accesoria oculta lateral izquierda, el marcapaseo auricular rápido a la misma longitud de ciclo de la taquicardia, reprodujo la misma aberrancia observada durante la taquicardia. Este procedimiento demostró que el bloqueo de rama funcional fue debido a la longitud de ciclo corto y no a la presencia de una vía accesoria aurículo-ventricular.

Functional bundle branch block during a supraventricular tachycardia can be observed with shorter cycle lengths and represent a physiologic response by the specialized intraventricular conduction system to accelerated AV nodal conduction. The present case corresponds to a young patient with exercise induced orthodromic A-V reentrant tachycardia and alternating bundle branch block. This unusual response is explained by the finding obtained during the electrophysiology study. An accelerated AV nodal conduction made the depolarizing wave front reach the bundle branches during their refractory period. Once block in one bundle was stablished, block persisted due to the linking phenomenon that is repetitive retrograde concealed conduction from the contralateral bundle. After catheter ablation of a concealed left-sided accessory A-V pathway, rapid atrial pacing at the same cycle length of the tachycardia reproduced the same aberrancies observed during tachycardia. This response proved that functional bundle branch block is due to the short cycle length and not the presence of an accessory A-V pathway.

Slow and fast orthodromic and antidromic variants in acute 9-h jet-lagged pygmy field mice.

Biological clocks help organism to adapt temporally to a variety of rhythmic environmental cues. Acute changes in the rhythmicity of entraining cues causes short- to long-term physiological distress in individuals, for example, those occurring during jet-lag after long-haul transmeridial flights, or shift work. Variations in the rate of re-entrainment to a 9 h advanced schedule (simulation of acute Jet-lag/shift work) in the Indian pygmy field mouse, Mus terricolor are reported. Wheel- and lab-acclimated adult male mice were entrained to a 12:12 h light:dark (LD) cycles, followed by a 9 h advance in the LD cycle. In response, these mice either advanced or delayed their activity onsets, with individual variation in the rate and direction. Rapid orthodromic (advancing) re-entrainers exhibited a coincidence of activity onsets with the new dark onset in <=3 days, while gradually advancing re-entrainers took ~9 days or more. Delayers (antidromic) also either re-entrained very rapidly (<=2 days), or gradually (~9 days). Acrophase measurement confirmed the direction of the transients, which did not depend on the free-running period. Such different patterns might determine the differential survival of individuals under the pressure of re-entrainment schedules seen in jet-lag and shift work.

Antidromic and Orthodromic Sensory Conduction of Ring Finger in Carpal Tunnel Syndrome

For the diagnosis of carpal tunnel syndrome (CTS), a sensory conduction study of median nerve is the most sensitive parameter, by either antidromic or orthodromic recording. Many different sensory recordings have been developed to detect the mild or early cases of carpal tunnel syndrome. A comparison of the median and ulnar sensory responses using the 4th digit either orthodromically or antidromically has been one of the methods. However, a simultaneous comparison of both antidromic and orthodromic methods on the 4th digit has not been documented. For the comparison between the median and the ulnar sensory nerve conduction of the 4th digit recorded antidromically or orthodromically, conduction studies of the median and ulnar sensory nerves were performed using standard methods in normal populations as well as in patients with carpal tunnel syndrome. We studied 31 CTS patients (46 hands) with mean age of 54 years old (range, 25~70). Also, 51 subjects (102 hands) with mean age of 48 years old were studied as control. The difference of antidromic latencies between the median and the ulnar nerves was less than or equal to 0.4 msec in the control subjects and greater than or equal to 0.5 msec in the patients with carpal tunnel syndrome. The difference of orthodromic latencies was less than or equal to 0.5 msec in the control subjects and greater than or equal to 0.5 msec in the patients with carpal tunnel syndrome. By the antidromic and orthodromic methods, the mean difference between latencies of the median or ulnar nerve was not statistically significant. However the amplitude of median or ulnar nerve was 2 times larger by the antidromic method than by the orthodromic. We concluded that the latency difference of 0.5 msec or greater between the median and ulnar nerve sensory conductions from the 4th digit would be valuable for the diagnosis of CTS. The antidromic methods with larger amplitude may be more technically convenient to determine CTS than the orthodromic methods.