CIRCANNUAL VARIATION OF MALIGNANT VENTRICULAR TACHYARRHYTHMIAS IN PATIENTS WITH IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS AND EITHER CORONARY-ARTERY DISEASE OR IDIOPATHIC DILATED CARDIOMYOPATHY

We studied the possible relation between the frequency of ventricular tachyarrhythmic events and thermal stress in patients with an implanta ble cardioverter-defibriIlator (ICD) living in a locally limited area under homogeneous climatic conditions. The frequency of tachyarrhythmi c events wets correlated with the thermal stress level according to th e ''Klima Michel Model,'' a complete thermo physiol og ic model that c alculates ''felt-temperature'' values on the basis of the outdoor temp erature and further meteorologic data. During a mean follow-up time of 40 +/- 17 months (range 4 to 72), 761 ventricular tachyarrhythmic eve nts occurred in 50 of 138 consecutive ICD recipients. Analysis of the monthly felt-temperature levels and the mean circannual variation of t he registered ventricular arrhythmias suggested that very cold and ver y hot conditions may be associated with an increased frequency of vent ricular tachyarrhythmias. This finding was confirmed by calculation of the sum of tachyarrhythmias on all 2,039 days of the follow-up period divided into 5-degree-step felt-temperature classes. Thus, thermal st ress may be 1 factor triggering the occurrence of ventricular tachyarr hythmias in patients with cardiac disease and suppressed cardiac funct ion, Part of the increase in cardiac mortality under above-average hot and cold atmospheric conditions may be attributed to ventricular arrh ythmic events. (C) 1997 by Excerpta Medica, Inc.