Complete Atrioventricular Block after Arsenic Trioxide Treatment in an Acute Promyelocytic Leukemic Patient

A V block after arsenic trioxide (As₂O₃) treatment for refractory acute promyelocytic leukemia is very rare. In this patient, the block was at A-H level and manifested with complete AV block and Wenckebach second-degree type 3:2 block. The junctional recovery time during complete AV block did not significantly prolong after administration of more arsenic trioxide. The effect of heart block of arsenic trioxide seemed reversible after the discontinuation of arsenic trioxide and was not correlated to the leukemic status as observed in this patient.     

Heterogeneous Expression of Potassium Currents and Pacemaker Currents Potentially Regulates Arrhythmogenesis of Pulmonary Vein Cardiomyocytes

Introduction: The relationship between the determining factors and beating rates of pulmonary vein (PV) pacemaker cardiomyocytes has not been fully elucidated. The purposes of this study were to compare the electrophysiological characteristics between PV fast and slow pacemaker cardiomyocytes. Methods: Whole‐cell patch clamp was used to investigate the action potentials, transient outward currents (I_to), sustained outward potassium currents (I_Ksus), rapid delayed rectifier potassium currents (I_Kr), inward rectifier potassium current (I_K1), pacemaker currents (I_f), and transient inward currents in isolated rabbit PV single fast (≥2.5 Hz) and slow (<2.5 Hz) pacemaker cardiomyocytes. Results: The fast PV pacemaker cardiomyocytes (n = 66) had lesser negative maximum diastolic potential (?53 ± 1 mV vs ?59 ± 1 mV, P < 0.001) and larger slope of diastolic depolarization (0.31 ± 0.02 V/sec vs 0.09 ± 0.01 V/sec, P < 0.001) than slow PV pacemaker cardiomyocytes (n = 65). Moreover, the PV beating rates correlated well with the slope of diastolic depolarization and maximum diastolic potential with a linear regression. As compared to those in slow PV pacemaker cardiomyocytes, the fast PV pacemaker cardiomyocytes had smaller I_to and I_K1, and larger I_f but with similar I_Ksus,I_Kr, and transient inward currents. However, only few fast (2/34) and slow (1/23) PV pacemaker cardiomyocytes contained barium‐sensitive hyperpolarization‐activated time‐dependent current (I_KH)_. Conclusions and Implications: The fast and slow PV pacemaker had different electrophysiological characteristics. I_to, I_K1, and I_f may regulate the beating rates of PV pacemaker cardiomyocytes.     

Pathophysiology of the Pulmonary Vein as an Atrial Fibrillation Initiator:

The basic electrophysiologic studies have proved the arrhythmogenic mechanisms of the pulmonary vein as an atrial fibrillation initiator; the mechanisms include enhanced automaticity, triggered activity, and microreentry from myocardial sleeves inside pulmonary veins. Immunohistology study has proved the conduction characteristics of pulmonary vein myocardium, and further study of ionic currents are important for understanding atrial fibrillation initiation from the pulmonary vein. (PACE 2003; 26[Pt. II]:1576–1582)     

Clonal chromosomal abnormalities as direct evidence for clonality in nasal T/natural killer cell lymphomas

Nasal T/natural killer (NK) cell lymphoma is a distinct clinicopathologic entity which is more prevalent in Asia than in America and Europe. The clonal nature of the infiltrating lymphoid cells is difficult to demonstrate because of the lack of immunologic markers for clonality and the absence of clonal T-cell receptor gene rearrangement in most cases. In this study, clonal chromosomal abnormalities were detected in the tumour cells from four patients with nasal T/NK cell lymphoma. This finding provided direct evidence for clonality of the disease. Moreover, nonrandom cytogenetic abnormalities, including isochromosome for the short arm (p) of chromosome 6, isochromosome for the long arm (q) of chromosome 1, partial deletion of 6q, and aberrations at 11q, were disclosed. Isochromosome 6p was the sole structural abnormality in one patient, which may be a pathognomonic change in nasal lymphoma.