Timing of life-threatening arrhythmias detected by implantable cardioverter-defibrillators in relation to changes in cosmophysical factors.

BACKGROUND Studies have linked the natural history of many pathologies with environmental physical activity. This study investigated the relationship between the occurrence of ventricular tachycardia/fibrillation (VT/VF) recorded by implantable cardioverter defibrillators (ICD) and geomagnetic and cosmic ray (neutron) activity. METHODS The study group included 85 patients (73 men) with cardiomyopathy (80% ischemic) who underwent ICD placement in the years 1995-2006; 74% had a left ventricular ejection fraction of < 30%. Data on the days on which VT/VF occurred (total number of days: 284) and the days on which the patients were treated (total number of treatments: 580) were collected from the ICD records. The findings were analyzed against levels of geomagnetic activity (GMA) (I degree -IV degree) and cosmic ray activity (CRA), derived from international observatories, on the same days and throughout the study period. RESULTS On days of VT/VF, daily values of GMA level averaged 1.5 +/- 0.7, consistent with level I degree (quiet). The ratios of daily VT/VF episodes and treatment to GMA level for the whole study period were as follows: 1.2 level I; 0.9 level II; 0.69 level III; 0.78 level IV (r = -0.974; p = 0.02). Mean CRA on days of VT/VF was 9246.8 +/- 299.0 imp/min, and for all 4383 days studied, 8805.33 +/- 411.4 imp/min (p < 0.0001). CONCLUSIONS In patients with predominantly ischemic cardiomyopathy and severe left ventricular dysfunction, VT/VF occurs more often on days of low GMA and high CRA. Further studies are needed to determine the underlying mechanism of the effect of neutron activity on cardiac electrical instability.