The Atrial Electrogram During Clinical Electrophysiologic Studies: Onset versus the Local/Intrinsic Deflection

The Local Atrial Deflection. Introduction : As a wave front passes unfiltered bipolar recording electrodes, the point of local depolarization is marked by a maximal change in voltage, i.e., the intrinsic deflection. However, during electrophysiologic studies, the depolarization (A) on the lead recording the His-bundle potential traditionally has been measured at the first rapid reproducible deflection on a filtered electrogram. This methodology permits considerable latitude for subjective interpretation. The purpose of this study was to assess the timing of the atrial electrogram using the intrinsic deflection of relatively unfiltered electrograms (0.1-4.0 to 1,250 Hz) or the equivalent on filtered recordings. Methods and Results : To do this we studied 70 patients without evidence of atrial or atrioventricular (AV) nodal disease, documenting the difference in timing between the A wave as traditionally measured and as measured at its peak local deflection (A_L) determined from simultaneously recorded filtered and relatively unfiltered electrograms. New ranges based on the A_L were established for timing of intra-atrial and AV nodal conduction intervals. The P-A (41 ± 11 msec) was significantly shorter than the P-A_L (55 ± 12) and the A-H (80 ± 20) was longer than the A_L-H (66 ± 21 msec), both P <0.001. Interobserver differences in measurements were smaller when using the local (A_L) rather than traditional criteria. Conclusions : Conventional measurement of the A deflection provides only a rough estimate of local depolarization of the atrium near the AV node. The criteria proposed in the present article may (1) provide a better estimate of the timing of local depolarization; (2) have application in computerized timing of intervals; and (3) decrease technical problems and subjective error.     

Decrease in bispectral index prior to cardiovascular collapse during Caesarean sections

We report a case of significant reduction in bispectral index (BIS) associated with suspected amniotic fluid embolism (AFE) that occurred prior to change in haemodynamic variables. The patient was a 29‐year‐old nulliparous, who was admitted for Caesarean section under general anaesthesia in the 33rd week of pregnancy. After the baby was born, the BIS value suddenly decreased to 0, with suppression ratio of 100. One minute later, saturation decreased abruptly to 85%, end‐tidal carbon dioxide (EtCO₂) decreased to 5 mmHg, peak inspiratory pressure increased to 35 cm H₂O, and non‐invasive blood pressure (BP) failed to obtain a reading. After administration of vasoactive drugs, the systolic BP was maintained at 100 mmHg or higher, the BIS value rose to 10–20, and the EtCO₂ increased to 24–33 mmHg. In this case, the BIS monitoring may provide an earlier warning of impending cardiovascular collapse in the case of AFE.     

Increased Range of Motion and Decreased Strength of the Thumb in Massage Practitioners with Thumb Pain

The purpose of this study was to compare the range of motion (ROM) and strength of the metacarpophalangeal (MP) and interphalangeal (IP) joints among massage practitioners with and without thumb pain and control subjects. Sixteen massage practitioners with thumb pain, 16 practitioners without thumb pain, and 16 control subjects participated in this study. ROM of flexion, extension, and abduction in the MP joint; ROM of flexion and extension in the IP joint of the thumb; strength of the flexor pollicis brevis (FPB), extensor pollicis brevis (EPB), abductor pollicis brevis, flexor pollicis longus (FPL), and extensor pollicis longus measured in all subjects. ROM of extension and abduction in the MP joint were significantly increased in massage practitioners with and without thumb pain compared with control subjects. ROM of extension in the IP joint was significantly increased in massage practitioners with thumb pain compared with those without thumb pain. The strength of the EPB and FPL muscle was significantly decreased in massage practitioners with thumb pain compared with those without thumb pain and control subjects, respectively. In addition, there was significantly increased EPB/FPB strength in massage practitioners without thumb pain compared to those with thumb pain and control subjects.     

Low-dose-rate radiation exposure leads to testicular damage with decreases in DNMT1 and HDAC1 in the murine testis

This study examined the effects of continuous low-dose-rate radiation exposure (3.49 mGy/h) of gamma rays on mice testicles. C57BL/6 mice were divided into sham and radiation groups (n = 8 each), and were exposed to either sham irradiation or 2 Gy for 21 days, 0.2 Gy for 2 days, or 0.02 Gy for 6 h of low-dose-rate irradiation. Testicular weight, seminiferous tubular diameter, and seminiferous epithelial depth were significantly decreased in the mice irradiated with 2 Gy at 1 and 9 days after exposure. Moreover, the low-dose-rate radiation exposure induced an increase in malondialdehyde levels, and a decrease in superoxide dismutase activity in the testis of mice irradiated with 2 Gy at 1 and 9 days after exposure. The sperm count and motility in the epididymis also decreased in mice irradiated with 2 Gy at 1 and 9 days after exposure, whereas there was no significant effect on the proportion of abnormal sperm. The expressions of DNA methlytransferases-1 and histone deacetylases 1 in testes irradiated with 2 Gy were significantly decreased compared with the sham group. In conclusion, the damage exerted on the testes and epididymis largely depended on the total dose of low-dose-rate radiation.     

Low and high linear energy transfer radiation sensitization of HCC cells by metformin

The purpose of this study was to investigate the efficacy of metformin as a radiosensitizer for use in combination therapy for human hepatocellular carcinoma (HCC). Three human HCC cell lines (Huh7, HepG2, Hep3B) and a normal human hepatocyte cell line were treated with metformin alone or with radiation followed by metformin. In vitro tests were evaluated by clonogenic survival assay, FACS analysis, western blotting, immunofluorescence and comet assay. Metformin significantly enhanced radiation efficacy under high and low Linear Energy Transfer (LET) radiation conditions in vitro. In combination with radiation, metformin abrogated G2/M arrest and increased the cell population in the sub-G1 phase and the ROS level, ultimately increasing HCC cellular apoptosis. Metformin inhibits the repair of DNA damage caused by radiation. The radiosensitizing effects of metformin are much higher in neutron (high LET)-irradiated cell lines than in γ (low LET)-irradiated cell lines. Metformin only had a moderate effect in normal hepatocytes. Metformin enhances the radiosensitivity of HCC, suggesting it may have clinical utility in combination cancer treatment with high-LET radiation.     

Effects of a problem‐solving counseling program to facilitate intensified walking on Koreans with type 2 diabetes

Aim: This study aimed to evaluate the immediate and long‐term effects of a 12 week problem‐solving (PS) counseling program to facilitate intensified walking with machinery monitoring on persons with type 2 diabetes mellitus in Korea. Methods: The study used a quasi‐experimental design. The participants were 57 patients with diabetes from three endocrinology or internal medicine clinics in an urban city of South Korea. Moderate‐intensity walking and PS counseling were recommended to both groups. The difference between the two groups was whether the intensity of the exercise was monitored by an ambulatory heart rate monitor (experimental group) or was self‐regulated (comparison group). Those programs were evaluated in relation to BMI, glycemic control (blood glucose level, glycosylated hemoglobin [HbA1c]), a vascular complication index (total cholesterol, high‐density lipoprotein cholesterol, low‐density lipoprotein cholesterol, triglycerides, tissue plasminogen activator [t‐PA], plasminogen activator inhibitor‐1 [PAI‐1], Parma Cardiovascular Risk Index), and coping strategies at 3 and 6 months. Results: The experimental group members showed dramatic decreases in their glucose and HbA1c levels at 3 months. The values of t‐PA decreased significantly at baseline, compared to at 3 months. The levels of PAI‐1 continuously declined and the Parma Cardiovascular Risk Index score did not change significantly from baseline to at 3 months, but showed significant effects at 6 months. Conclusion: A combined program of intensified walking, using a heart rate monitor, with PS counseling is more helpful to prevent complications than self‐regulated exercise for persons with type 2 diabetes in Korea.