Are neutrons involved in the pathogenesis of life-threatening cardiac arrhythmias?

Geomagnetic fields protect the earth from the adverse effects of cosmic rays, whose activity can be indirectly measured by monitoring the level of neutrons in the environment. The number and days of discharges from automatic implantable cardioverter defibrillators (ICD) in patients with cardiac arrhythmias are inversely correlated with the daily level of geomagnetic activity (GMA). The aim of the present was to determine whether neutron levels on days of AICD discharges are higher than average. Days on which discharges occurred were recorded in 31 patients bearing ICDs for managing ischemic cardiomyopathy. Daily neutron levels obtained from the monitoring data of the Russian Academy of Sciences in Moscow were analyzed using Student's t test. The mean (+/-SD) daily neutron level for the 1096-day period was 8299.29 +/- 294.236 imp/min (median 8252), and for days of ACID discharge, 8423.93 +/- 274.187 imp/min (median 8443) (p = 0.0002). The mean neutron activity on days of AICD discharges in response to ventricular disturbances was significantly higher than the mean level over the 1096-day study period. Whether this relation is a direct result of low GMA or due to an independent role of neutrons in the pathogenesis and timing of cardiac arrhythmias is unknown.

There is synergism between high-intensity, low-frequency ultrasound and streptokinase but not with eptifibatide, heparin, and aspirin. Differential effects on fresh and aged blood clots. An in vitro study.

OBJECTIVE: Ultrasound is emerging as a promising modality for recanalization of acutely thrombosed blood vessels, especially when associated with fibrinolytics. We assessed the efficacy of ultrasound combined with saline, heparin, eptifibatide, aspirin, and streptokinase in disruption of fresh as well as aged human blood clots, using an in vitro model. METHODS: Blood clots from five donors, 2-4 or 48 hours old, were cut into 250-400 mg slices and immersed for 1, 15, or 30 min in 10 ml saline containing either heparin, eptifibatide, aspirin, streptokinase, or saline alone. Clots were then randomized to 10 s of 20 kHz ultrasound or immersion alone. After treatment, the percentage difference in weight was calculated. RESULTS: Immersion of fresh clots without ultrasound in eptifibatide and heparin resulted in significantly more clot lysis than immersion in saline, aspirin, and streptokinase. Immersion of aged thrombi without ultrasound in heparin, eptifibatide, and aspirin had no additive effect over immersion in saline. Ultrasound enhanced clot disruption in all five solutions, in each immersion time and both in fresh and aged clots. Heparin and aspirin had no additive effect, compared with saline, on ultrasound disruption of both fresh and aged clots, whereas eptifibatide was less effective than saline. In contrast, streptokinase greatly enhanced disruption of both fresh (P=.004) and aged (P<.001) thrombi by ultrasound. The combinations of ultrasound with saline, heparin, eptifibatide, and aspirin were less effective on aged than fresh thrombi, whereas the combination of ultrasound with streptokinase was equally effective on fresh and aged thrombi. CONCLUSIONS: Using a simple in vitro model, we found that the combination of streptokinase and low-frequency ultrasound had a synergistic effect on disruption of both fresh and aged blood clots. Further studies are needed to assess the role of heparin and antiplatelet agents in augmenting clot disruption by ultrasound in in vivo models of acute and subacute thrombosis.

The effects of streptokinase and hydroxyethyl starch on in vitro clot disruption by ultrasound.

BACKGROUND: In vitro studies showed that low-frequency ultrasound (US) causes blood clot dissolution. This effect is augmented with thrombolytics, microbubbles and microparticles. However, in animal models of transcutaneous delivery, US alone is not effective, probably due to attenuation of US energy by overlying skin. When combined with thrombolytics or microbubbles, transcutaneous US is highly effective. PURPOSE: To assess the synergistic effect of low-intensity low-frequency US and saline, hydroxyethyl starch (HAES) (a non-gas filled microparticle containing solution), streptokinase (STK), and their combination on blood clot disruption. METHODS: Human blood clots from 4 healthy donors, 2-4 hours old, were immersed for 0, 15, or 30 min in 37 degrees C in 10 ml of the above-mentioned solutions, and then were randomized to 10 sec of 20 kHz US or no US. The % difference in weight was calculated. RESULTS: Immersion for 30 min without US resulted in 13.8 +/- 1.2% clot lysis in saline, and 22.0 +/- 1.3%, 21.7 +/- 2.1%, and 23.2 +/- 1.9% in STK, HAES, and STK + HAES, respectively (p = 0.002). US augmented clot lysis in all groups and at all time points. With low-intensity US, HAES was not better than saline. However, the combination of HAES + STK with US resulted in larger clot disruption at 15 sec incubation time (46.7 +/- 3.2%) than with saline (29.6 +/- 2.1%), HAES (29.6 +/- 2.5%), and STK (32.8 +/- 3.6%) (p < 0.001). CONCLUSION: low-frequency, low-intensity US combined with HAES and STK resulted in greater clot disruption at short incubation times. This combination may assist in achieving faster reperfusion in in vivo models.