Relationship between fibrosis and ventricular arrhythmias in Chagas heart disease without ventricular dysfunction

Abstract

Background: Patients with Chagas disease and segmental wall motion abnormality (SWMA) have worse prognosis independent of left ventricular ejection fraction (LVEF). Cardiac magnetic resonance (CMR) is currently the best method to detect SWMA and to assess fibrosis.

Objective: To quantify fibrosis by using late gadolinium enhancement CMR in patients with Chagas disease and preserved or minimally impaired ventricular function (> 45%), and to detect patterns of dependence between fibrosis, SWMA and LVEF in the presence of ventricular arrhythmia.

Methods: Electrocardiogram, treadmill exercise test, Holter and CMR were carried out in 61 patients, who were divided into three groups as follows: (1) normal electrocardiogram and CMR without SWMA; (2) abnormal electrocardiogram and CMR without SWMA; (3) CMR with SWMA independently of electrocardiogram.

Results: The number of patients with ventricular arrhythmia in relation to the total of patients, the percentage of fibrosis, and the LVEF were, respectively: Group 1, 4/26, 0.74% and 74.34%; Group 2, 4/16, 3.96% and 68.5%; and Group 3, 11/19, 14.07% and 55.59%. Ventricular arrhythmia was found in 31.1% of the patients. Those with and without ventricular arrhythmia had mean LVEF of 59.87% and 70.18%, respectively, and fibrosis percentage of 11.03% and 3.01%, respectively. Of the variables SWMA, groups, age, LVEF and fibrosis, only the latter was significant for the presence of ventricular arrhythmia, with a cutoff point of 11.78% for fibrosis mass (p < 0.001).

Conclusion: Even in patients with Chagas disease and preserved or minimally impaired ventricular function, electrical instability can be present. Regarding the presence of ventricular arrhythmia, fibrosis is the most important variable, its amount being proportional to the complexity of the groups.

Figure 1

Representation of the 17 left ventricular wall segments. (A) The figure in each segment indicates the number of patients with segmental wall motion abnormality. The grey color represents the segments most frequently affected by segmental wall motion abnormality. (B) Number of patients with fibrosis in each left ventricular wall segment. The grey color represents the segments most frequently affected by fibrosis.

Graph 1

Ventricular arrhythmia on Holter or treadmill exercise test and presence of fibrosis.

Graph 2

Ejection fraction and amount of fibrosis in the different groups. LVEF: left ventricular ejection fraction.

Figure 2

Classification tree showing that fibrosis is the most significant variable for the presence of ventricular arrhythmia, with a cutoff point of 11.78%.

Figure 3

Classification tree per group, showing that the group with segmental wall motion abnormality (Group 3) had the majority of patients with ventricular arrhythmia.

Figure 4

Correlation matrix (values as R2). The more oval the tracing, the better the correlation. LV: left ventricular; LVEF: left ventricular ejection fraction; RVEF: right ventricular ejection fraction.