PLASMA NOREPINEPHRINE, MYOCARDIAL DAMAGE AND LEFT-VENTRICULAR SYSTOLIC FUNCTION IN CHAGAS HEART-DISEASE

The functional status of the sympathetic nervous system in Chagas' hea rt disease is still the subject of intense controversy, To determine t he nature of the abnormalities of the sympathetic nervous system, we m easured the plasma norepinephrine concentration of chagasic patients w ith varying degrees of myocardial damage. Thirty-six patients with pos itive serology for Chagas' disease were studied, Twenty patients were in Functional Class I(New York Heart Association), 10 were in Function al Class II and six were in Functional Classes III-IV. Cardiac cathete rization was performed in 24 patients, The asymptomatic patients hada plasma norepinephrine concentration (121 +/- 37 pg/ml, mean +/- S.D.) not different from normal controls (103 +/- 59 pg/ml). The symptomatic patients, however, had a significantly elevated plasma norepinephrine concentration (665 +/- 354 pg/ml, P < 0.001). The baseline heart rate of the asymptomatic and symptomatic patients directly correlated with the plasma norepinephrine concentration (r = 0.69, P < 0.0001). The s ymptomatic patients had larger ventricular volumes, higher left ventri cular end-diastolic pressures and lower ejection fractions than the as ymptomatic patients and normal controls. The plasma norepinephrine con centration correlated linearly with the left ventricular end-diastolic volume (r = 0.77, P < 0.0001), and non-linearly with the ejection fra ction (r = -0.70, P < 0.0001) and the left ventricular end-diastolic p ressure (r = 0.53, P < 0.007). These results indicate that, in Chagas' heart disease as in most other cardiac diseases, sympathetic nervous system activation is a]ate and compensatory phenomenon, In other words , sympathetic activation is very likely related to the progressive imp airment of left ventricular function.