title: Limited myocardial contractile reserve and chronotropic incompetence in patients with chronic Chagas' disease: assessment by dobutamine stress echocardiography.
abstract: OBJECTIVE
  To determine whether dobutamine stimulation in patients with Chagas' disease may uncover abnormal contractile responses as seen in ischemic myocardium.
  
  
  BACKGROUND
  Segmental left ventricular (LV) dysfunction in the absence of coronary atherosclerosis is frequently seen in patients with chronic Chagas' heart disease. Myocardial ischemia and coronary microcirculation abnormalities have been found in animal models and in humans with Chagas' disease. In addition, chagasic sera may contain autoantibodies against human beta-adrenergic receptors.
  
  
  METHODS
  Two groups of patients with Chagas' disease were studied by echocardiography: group 1 (n = 12) without and group 2 (n = 14) with LV segmental wall motion abnormalities (mostly apical aneurysm). Ten normal subjects served as control subjects. We performed qualitative assessment of wall motion and quantitative evaluation of LV cavity under baseline conditions and after dobutamine stimulation.
  
  
  RESULTS
  Patients with Chagas' disease exhibited a blunted inotropic and chronotropic response to dobutamine stimulation. After dobutamine, fractional area change in Chagas' group 1 (54.7+/-6.6%; SD) and in group 2 (35.1+/-12.1%) were significantly lower than control group (66.7+/-2.5%; p < 0.001). In addition, in 6 of 14 group 2 patients, dobutamine induced a biphasic response with improvement at low dose and deterioration at peak dose, as seen in patients with coronary artery disease. Although the three groups had similar basal mean heart rates and attained a similar mean peak dobutamine doses, both groups of patients with Chagas' disease had a significantly blunted mean heart rate effect after dobutamine (p < 0.0001).
  
  
  CONCLUSIONS
  Thus, dobutamine stimulation unmasks a chronotropic incompetence and a blunted myocardial contractile response in chagasic patients, even in those with no overt manifestation of heart disease.
authors.affiliation: Centro de Investigaciones J.F. Torrealba, Hospital Universitario de Caracas, Venezuela.
authors.forename: H
authors.initials: H
authors.lastname: Acquatella
authors.forename: J E
authors.initials: JE
authors.lastname: Pérez
authors.forename: J A
authors.initials: JA
authors.lastname: Condado
authors.forename: I
authors.initials: I
authors.lastname: Sánchez
mesh_terms: D002316:Cardiotonic Agents / Q000008:administration & dosage; D002598:Chagas Cardiomyopathy / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002908:Chronic Disease; D004280:Dobutamine / Q000008:administration & dosage; D004452:Echocardiography / Q000379:methods; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D011379:Prognosis; D011446:Prospective Studies; D013268:Stimulation, Chemical; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000503:physiopathology*