Alterations of circulatory responses to upright tilt in cardiac patients

Abnormal impedance cardiography predicts symptom severity in chronic fatigue syndrome

BACKGROUND

Findings indicative of a problem with circulation have been reported in patients with chronic fatigue syndrome (CFS). We examined this possibility by measuring the patient's cardiac output and assessing its relation to presenting symptoms.

METHODS

Impedance cardiography and symptom data were collected from 38 patients with CFS grouped into cases with severe (n = 18) and less severe (n = 20) illness and compared with those from 27 matched, sedentary control subjects.

RESULTS

The patients with severe CFS had significantly lower stroke volume and cardiac output than the controls and less ill patients. Postexertional fatigue and flu-like symptoms of infection differentiated the patients with severe CFS from those with less severe CFS (88.5% concordance) and were predictive (R2 = 0.46, P < 0.0002) of lower cardiac output. In contrast, neuropsychiatric symptoms showed no specific association with cardiac output.

CONCLUSIONS

These results provide a preliminary indication of reduced circulation in patients with severe CFS. Further research is needed to confirm this finding and to define its clinical implications and pathogenetic mechanisms.

The use of postural vital signs in the assessment of fluid volume status

Postural or orthostatic vital signs, although frequently used in many clinical settings to aid in the diagnosis of fluid volume disturbance, can be a source of confusion. Practitioners often have questions about how to perform the test and may be uncertain about what results mean in various clinical situations. Some of this confusion is reflected in the literature, where studies on normal orthostatic responses seem to contradict clinically used parameters of "normal," and where very few studies appear on evaluating unusual responses as indicators of patients' fluid volume status. A review of existing literature is presented, in which relevant data are reviewed in terms of their impact on the use of this clinical sign. Recommendations regarding the use of the orthostatic test are given.