[Chronotropic-metabolic index in Chagas' disease].
Chronotropic incompetence is a common feature in Chagas' disease patients. New methodologies are now available to evaluate the chronotropic response in different subsets. The chronotropic-metabolic index (CMI) is one of these new indexes and quantifies the relationship between the increment of heart rate and the maximal oxygen consumption (VO2 max) during exercise testing. In normal subjects there is linear response and the index is round 1.0. The aim of the study was to evaluate the chronotropic response in healthy controls and Chagas' disease patients with and without left ventricular dysfunction, using CMI. Twenty-four controls and 171 Chagas' disease patients underwent a clinical protocol and maximal exercise testing. Chagas' disease patients were divided into two groups: Ch1= patients with ejection fraction (EF) > 39% and Ch2 = EF < 40%. CMI was analyzed and calculated according to the Wilkoff method. Chagas' disease patients were older than controls and showed higher prevalence of right bundle branch block, as well as lower VO2 max during exercise. Both groups of Chagas' disease patients showed a less steep curve in the chronotropic-metabolic index (Ch1: 0.91+/-0.10, Ch2: 0.89+/-0.08) than controls (1.0+/-0.12, p < 0.001). Chagas' disease patients with and without left ventricular dysfunction chronotropic incompetence may exhibit reduced chronotropic response to exercise, expressed by a less steep chronotropic-metabolic index.
Rocha
Ana Luiza Lunardi
AL
Faculdade de Medicina, Universidade de Minas Gerais, Belo Horizonte, MG, Brazil.
Rocha
Manoel Otávio da Costa
MO
Teixeira
Bruno Otávio Soares
BO
Lombardi
Federico
F
Abreu
Cláudia Drumond Guimarães
CD
Bittencourt
Roberto José
RJ
Barros
Márcio Vinícius Lins
MV
Ribeiro
Antonio Luiz Pinho
AL
D000328:Adult; D016022:Case-Control Studies; D002598:Chagas Cardiomyopathy / Q000503:physiopathology; D014355:Chagas Disease / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D011446:Prospective Studies; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*