Body Temperature Circadian Rhythm Variability Corresponds to Left Ventricular Systolic Dysfunction in Decompensated Cardiomyopathic Hamsters

Background: A declining amplitude of body temperature circadian rhythm (BTCR) predicts decompensation or death in cardiomyopathic hamsters. We tested the hypothesis that changes in BTCR amplitude accompany significant changes in left ventricular (LV) size and function. Methods and Results: Using intraperitoneal transmitters, we continuously monitored the temperature of 30 male BIO TO-2 Syrian dilated cardiomyopathic hamsters. Cosinor analysis was used to detect significant changes-defined as changes > 1 standard deviation from the baseline amplitude for 3 consecutive days-in BTCR amplitude over each hamster's lifespan. The Student t-test was used to compare BTCR variability and LV size and function (as assessed by 2D echocardiography) between baseline and the time that BTCR amplitude declined. All hamsters received 10 mg/kg furosemide daily. At the time of BTCR amplitude decline, functional parameters had changed significantly (P < .0001) from baseline: ejection fraction (0.31 +/- 0.09% vs. 0.52 +/- 0.08%), LV end-systolic volume (0.11 +/- 0.03 vs. 0.05 +/- 0.02 cm(3)), and LV end-diastolic volume (0.16 +/- 0.04 vs. 0.10 +/- 0.03 cm(3)). Conclusions: In decompensated cardiomyopathic hamsters, a decline in BTCR amplitude was associated with progression of heart failure and cardiac decompensation. Variation in BTCR warrants further investigation because of its potential implications for the diagnosis and treatment of cardiovascular disorders. (J Cardiac Fail 2011;17:937-943)