Chronotropic incompetence and abnormal autonomic modulation in ambulatory Chagas disease patients

Background: Chagas disease (ChD) patients might present chronotropic incompetence during exercise, although its physiopathology remains uncertain. We evaluated the heart rate (HR) response to exercise testing in ChD patients in order to determine the role of autonomic modulation and left ventricular dysfunction in the physiopathology of chronotropic incompetence. Methods: ChD ambulatory patients (n= 170) and healthy controls (n= 24) underwent a standardized protocol including Doppler echocardiography, Holter monitoring, HR variability analysis, brain natriuretic peptide (BNP) measurement, and maximal exercise testing. The chronotropic response was calculated as the percentage of predicted HR achieved and the HR increment (Delta HR) during exercise. ChD patients were divided according to the absence or presence of cardiopathy and chronotropic incompetence (<85% predicted HR). Results: Chronotropic incompetence was present in 34 (20%) of all ChD patients. The group with cardiopathy displayed reduced Delta HR (91 +/- 119 bpm) during exercise in comparison with ChD patients without cardiopathy (100 19 bpm). Both the values observed in ChD groups were significantly different from those of controls (112 +/- 13 bprn). Exercise duration, maximal oxygen consumption, and systolic blood pressure increment were significantly reduced in patients with abnormal chronotropic response. Delta HR during the exercise was significantly correlated with markers of autonomic control of sinus node, Such as rest HR (r= -0.498, P <= 0.001), peak HR during exercise (r= 0.775, P <= 0.001), minimal HR during Holter recording (r= -0.231, P= 0.003), and high- and low-frequency components of short-term HR variability (r= 0.188, P= 0.042 and r= 0.203, P= 0.027). Neither left ventricular function nor BNP levels were independently related to the presence of chronotropic incompetence. Conclusions: Chronotropic incompetence may be considered an early sign of autonomic dysfunction in ChD patients

A ENFERMAGEM E A PESQUISA NO BRASIL

A enfermagem brasileira em relação à pesquisa apresenta uma evolução acentuada nos últimos anos, com um saldo quantitativo na última década. Os pesquisadores brasileiros localizam-se na sua maioria na categoria docente e na região sudeste do Brasil. Existem oito Centros universitários de estudos em nível de pós-graduação, com inúmeras áreas de concentração nos cursos de mestrado. Os cursos de doutorado localizam-se todos na região sudeste. Existem recursos disponíveis em agências financiadoras de pesquisas para a enfermagem, porém a demanda ainda é incipiente. A Associação Brasileira de Enfermagem tem procurado implementar medidas que visam o desenvolvimento das pesquisas na área da enfermagem