Circadian body temperature variability is an indicator of poor prognosis in cardiomyopathic hamsters.

BACKGROUND: Low body temperature is an independent predictor of poor prognosis in patients with congestive heart failure. The cardiomyopathic hamster develops progressive biventricular dysfunction, resulting in heart failure death at 9 months to 1 year of life. Our goal was to use cardiomyopathic hamsters to examine the relationship between body temperature and heart failure decompensation and death. METHODS AND RESULTS: To this end, we implanted temperature and activity transducers with telemetry into the peritoneal space of 46 male Bio-TO-2 Syrian cardiomyopathic hamsters. Multiple techniques, including computing mean temperature, frequency domain analysis, and nonlinear analysis, were used to determine the most useful method for predicting poor prognosis. Data from 44 hamsters were included in our final analysis. We detected a decline in core body temperature in 98% of the hamsters 8+/-4 days before death (P < .001). We examined the dominant frequency of temperature variation (ie, the circadian rhythm) by using cosinor analysis, which revealed a significant decrease in the amplitude of the body temperature circadian rhythm 8 weeks before death (0.28 degrees C; 95% CI, 0.26-0.31) compared to baseline (0.36 degrees C; 95% CI, 0.34-0.39; P=.005). The decline in the circadian temperature variation preceded all other evidence of decompensation. CONCLUSIONS: We conclude that a decrease in the amplitude of the body temperature circadian rhythm precedes fatal decompensation in cardiomyopathic hamsters. Continuous temperature monitoring may be useful in predicting preclinical decompensation in patients with heart failure and in identifying opportunities for therapeutic intervention.

Decreasing body temperature predicts early rehospitalization in congestive heart failure.

BACKGROUND: In congestive heart failure (CHF), a low body temperature at hospital admission predicts in-hospital mortality. We hypothesized that a postdischarge reduction in body temperature predicts early CHF rehospitalization and death. METHODS: We reviewed the records of 198 patients discharged after CHF hospitalization. We categorized the patients as hypothermic or normothermic (cutoff point, 36.3 degrees C/97.4 degrees F) according to body temperature at discharge. We classified the 2 groups according to the direction of temperature change between discharge and the first follow-up visit: normothermic/non-decreasing temperature (N+), normothermic/decreasing temperature (N-), hypothermic/non-decreasing temperature (H+), and hypothermic/decreasing temperature (H-). RESULTS: Ninety-three patients (47%) had decreasing temperatures, and 105 patients (53%) had non-decreasing temperatures. Kaplan-Meier analysis revealed a significant intergroup difference in survival (P = .01) and rehospitalization time (P = .005). On logistic regression, a decreasing temperature was significantly associated with rehospitalization within 180 days (odds ratio, 4.01; 95% confidence interval, 1.63-10.02; P = .003). On Cox regression, the hazard ratios for death were 3.19 (P = .07), 6.49 (P = .004), and 5.17 (P = .07), for the N-, H+, and H- groups, respectively, versus the N+ group. For rehospitalization time, the hazard ratios were 7.02 (P = .01), 4.24 (P = .08), and 13.43 (P = .005) for the N-, H+, and H- groups, respectively, versus the N+ group. CONCLUSION: Decreasing body temperatures can predict readmission, decreased time to rehospitalization, and (in combination with hypothermia) decreased survival.

Devices in heart failure: potential methods for device-based monitoring of congestive heart failure.

Congestive heart failure has long been one of the most serious medical conditions in the United States; in fact, in the United States alone, heart failure accounts for 6.5 million days of hospitalization each year. One important goal of heart-failure therapy is to inhibit the progression of congestive heart failure through pharmacologic and device-based therapies. Therefore, there have been efforts to develop device-based therapies aimed at improving cardiac reserve and optimizing pump function to meet metabolic requirements. The course of congestive heart failure is often worsened by other conditions, including new-onset arrhythmias, ischemia and infarction, valvulopathy, decompensation, end-organ damage, and therapeutic refractoriness, that have an impact on outcomes. The onset of such conditions is sometimes heralded by subtle pathophysiologic changes, and the timely identification of these changes may promote the use of preventive measures. Consequently, device-based methods could in the future have an important role in the timely identification of the subtle pathophysiologic changes associated with congestive heart failure.