Right ventricular function in Chagas disease

Imaging Diagnosis of Right Ventricle Involvement in Chagas Cardiomyopathy

Right ventricle (RV) is considered a neglected chamber in cardiology and knowledge about its role in cardiac function was mostly focused on ventricular interdependence. However, progress on the understanding of myocardium diseases primarily involving the RV led to a better comprehension of its role in health and disease. In Chagas disease (CD), there is direct evidence from both basic and clinical research of profound structural RV abnormalities. However, clinical detection of these abnormalities is hindered by technical limitations of imaging diagnostic tools. Echocardiography has been a widespread and low-cost option for the study of patients with CD but, when applied to the RV assessment, faces difficulties such as the absence of a geometrical shape to represent this cavity. More recently, the technique has evolved to a focused guided RV imaging and myocardial deformation analysis. Also, cardiac magnetic resonance (CMR) has been introduced as a gold standard method to evaluate RV cavity volumes. CMR advantages include precise quantitative analyses of both LV and RV volumes and its ability to perform myocardium tissue characterization to identify areas of scar and edema. Evolution of these cardiac diagnostic techniques opened a new path to explore the pathophysiology of RV dysfunction in CD.

Evaluation of Right Ventricular Systolic Function in Chagas Disease Using Cardiac Magnetic Resonance Imaging

BACKGROUND

Right ventricular (RV) impairment is postulated to be responsible for prominent systemic congestion in Chagas disease. However, occurrence of primary RV dysfunction in Chagas disease remains controversial. We aimed to study RV systolic function in patients with Chagas disease using cardiac magnetic resonance.

METHODS AND RESULTS

This cross-sectional study included 158 individuals with chronic Chagas disease who underwent cardiac magnetic resonance. RV systolic dysfunction was defined as reduced RV ejection fraction based on predefined cutoffs accounting for age and sex. Multivariable logistic regression was used to verify the relationship of RV systolic dysfunction with age, sex, functional class, use of medications for heart failure, atrial fibrillation, and left ventricular systolic dysfunction. Mean age was 54±13 years, 51.2% men. RV systolic dysfunction was identified in 58 (37%) individuals. Although usually associated with reduced left ventricular ejection fraction, isolated RV systolic dysfunction was found in 7 (4.4%) patients, 2 of them in early stages of Chagas disease. Presence of RV dysfunction was not significantly different in patients with indeterminate/digestive form of Chagas disease (35.7%) compared with those with Chagas cardiomyopathy (36.8%) (P=1.000).

CONCLUSIONS

In chronic Chagas disease, RV systolic dysfunction is more commonly associated with left ventricular systolic dysfunction, although isolated and early RV dysfunction can also be identified.

Altered Cardiomyocyte Function and Trypanosoma cruzi Persistence in Chagas Disease

Chagas disease, caused by the triatominae Trypanosoma cruzi, is one of the leading causes of heart malfunctioning in Latin America. The cardiac phenotype is observed in 20-30% of infected people 10-40 years after their primary infection. The cardiac complications during Chagas disease range from cardiac arrhythmias to heart failure, with important involvement of the right ventricle. Interestingly, no studies have evaluated the electrical properties of right ventricle myocytes during Chagas disease and correlated them to parasite persistence. Taking advantage of a murine model of Chagas disease, we studied the histological and electrical properties of right ventricle in acute (30 days postinfection [dpi]) and chronic phases (90 dpi) of infected mice with the Colombian strain of T. cruzi and their correlation to parasite persistence. We observed an increase in collagen deposition and inflammatory infiltrate at both 30 and 90 dpi. Furthermore, using reverse transcriptase polymerase chain reaction, we detected parasites at 90 dpi in right and left ventricles. In addition, we observed action potential prolongation and reduced transient outward K(+) current and L-type Ca(2+) current at 30 and 90 dpi. Taking together, our results demonstrate that T. cruzi infection leads to important modifications in electrical properties associated with inflammatory infiltrate and parasite persistence in mice right ventricle, suggesting a causal role between inflammation, parasite persistence, and altered cardiomyocyte function in Chagas disease. Thus, arrhythmias observed in Chagas disease may be partially related to altered electrical function in right ventricle.

Pathophysiological basis of right ventricular remodeling

The pathophysiology of right ventricular (RV) remodeling is a complex process and may include unique elements not observed in left ventricular (LV) remodeling. The RV also has a relatively irregular geometry not accounted for in LV analyses. RV remodeling includes basic changes in geometry, wall thickness, and ventricular pressure-volume relationships. Also, myocyte dimensions and number increase, and myocardial extracellular matrix and biochemical milieu are modified. Remodeling has been associated with such diseases as pulmonary hypertension, lung transplant, LV pathology, Chagas' disease, and arrhythmogenic right ventricular cardiomyopathy. Disease progression may lead to further RV changes, including hypertrophy, dilatation, and subsequently to variable alterations in RV hemodynamic status. The multiple methods to assess RV hypertrophy include cine magnetic resonance imaging and 3-D echocardiography. Each technique offers different precision in evaluating RV dimensions and functional performance characteristics. Strategies to prevent RV remodeling include pharmacological agents, such as vasodilators and angiotensin-converting enzyme inhibitors, as well as more invasive interventions, such as ventricular assist devices.

Dysautonomia and ventricular dysfunction in the indeterminate form of Chagas disease

BACKGROUND

The associations between autonomic function and biventricular function in patients with the indeterminate form of Chagas disease remains to be elucidated.

METHODS

In 42 asymptomatic patients and 19 healthy volunteers, the autonomic function was assessed by time domain indices of heart rate variability (HRV), analyzed for 24 h; the right ventricular function was assessed by fraction area change, right ventricle shortening, and systolic excursion of the tricuspid valve; and the left ventricular function was assessed by ejection fraction and transmitral flow velocities. Data were expressed as mean+/-SD or medians (including the lower quartile and upper quartile). Groups were compared by Student's t or Mann-Whitney U test. Autonomic and ventricular function were correlated by Pearson's or Spearman's correlation coefficient. The level of significance was 5%.

RESULTS

Right and left ventricular systolic function indexes were comparable between groups. Transmitral flow velocities were decreased in the Chagas disease group (p<0.05). The patients presented impaired HRV as indicated by the values of SDNN-day (80 (64-99) ms vs. 98 (78-127) ms; p=0.045), SDNNI-24 h (54 (43-71) vs. 65 (54-105) ms; p=0.027), SDNNI-day (49 (42-64) vs. 67 (48-76) ms; p=0.045), pNN50-day (2.2 (0.7-5)% vs. 10 (3-11)%; p=0.033); and pNN50-24 h (3 (1-7)% vs. 12 (8-19)%; p=0.013). There were no correlations between the left ventricular diastolic indices and autonomic dysfunctional indices (p>0.05).

CONCLUSION

Patients with the indeterminate form of Chagas disease have both dysautonomia and left ventricular diastolic dysfunction. However, the right ventricular function is preserved. Importantly, ventricular diastolic dysfunction and dysautonomia are independent phenomena.

Detection of early right ventricular dysfunction in Chagas' disease using Doppler tissue imaging

BACKGROUND

The involvement of the right ventricle (RV) in Chagas' disease is frequent. Although echocardiography plays an important role in noninvasive assessment of cardiac function, evaluation of RV is challenging because of the anatomic and functional complexity of this chamber.

METHODS

To study early functional abnormalities in the RV, we selected 18 patients with Chagas' disease, no other disease, and a normal echocardiogram; and 12 normal individuals as a control group. All participants were submitted to Doppler tissue imaging and the parameters of systolic (systolic wave and regional isovolumic contraction time) and diastolic (early and late expansion waves) function were analyzed at the level of the interventricular septum and free wall of the RV.

RESULTS

Regional isovolumic contraction time values showed a statistically significant difference between the 2 groups both in the RV free (P =.0003) and septal (P =.003) walls. With respect to diastolic function, we observed a significant difference between groups involving the early expansion wave (P =.014) and e/a ratio (P =.004) of the RV free wall.

CONCLUSION

Doppler tissue imaging proved to be useful in early detection of RV dysfunction in Chagas' disease, with potential use in risk stratification of these patients.

Elevated levels of antibodies against sulphatide are present in all chronic chagasic and dilated cardiomyopathy sera

A natural anti-sulphatide antibody was found to be present in the serum of every normal individual studied. The reactivity of the antibody was assessed by its interaction with galactosylceramide-I3-sulphate. Antigen-antibody binding was strongly blocked by 1 mM heparin, dextran sulphate and chondroitin sulphate A, and by 5 mM chondroitin sulphate B. Antibodies avidly absorb to rabbit erythrocytes, but discretely to rat erythrocytes, suggesting that they are different from galactocerebroside antibodies. Elevated levels of sulphatide antibodies were present in all of 102 chronic Trypanosoma cruzi-infected patients studied, but not in other patients having cutaneous or visceral leishmaniasis, T. rangeli infection or several other protozoal, helminthic or mycotic infections. Interestingly, 100% of 40 dilated cardiomyopathy patients also have elevated levels of sulphatide antibodies. As T. cruzi is rich in galactocerebroside sulphate, it is proposed that in chagasic patients this glycolipid could act as an immunogen, inducing elevated titres of sulphatide antibodies, which could be important in the pathogenesis of cardiac or peripheral nerve symptoms.

Prognostic indicators of chronic chagasic cardiopathy

After 104 patients with positive serology for Chagas' disease had been followed for a decade, a selection of 66 patients was made from this number and a total of 25 variables obtained from clinical and paraclinical findings were analyzed, with the purpose of knowing which of these variables may be of help, in time, in determining prognosis. The information was analyzed using the Cox regression model. The patients were classified into groups according to the results in the invasive and noninvasive studies: those with a normal electrocardiogram without heart disease (14 patients) or with early segmental abnormalities of the left ventricle (9 patients); those with an abnormal electrocardiogram and advanced myocardial damage but without signs of congestive heart failure (26 patients); and those with an abnormal electrocardiogram together with congestive heart failure (17 patients). Of these patients, those with electrocardiographic abnormalities correspond to stages of the disease where advanced myocardial damage is proven. There was a 42% mortality during the follow-up of these patients. According to the regression model, the value of the systolic blood pressure is a good predictor of mortality (P = 0.0380) in those with congestive heart failure. When we analyzed jointly the patients with an abnormal electrocardiogram, we found that several variables (systolic blood pressure, the presence of atrial fibrillation, the radiologic cardiothoracic index, and left ventricular end-diastolic volume obtained by the ventriculogram), were negatively correlated with regard to survival. This last model has a chi-square of 11.36 (P = 0.0228). These models allow us to predict the prognosis in this group of patients with Chagas' disease and advanced myocardial damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of heart rate to atropine and left ventricular function in Chagas' heart disease

Chagasic patients may have a normal or abnormal response of heart rate to atropine. To determine if this response to atropine is related to the degree of left ventricular dysfunction, we studied 33 patients with a positive complement fixation test for Chagas' disease. Eleven subjects, with atypical chest pain and negative complement fixation test, were used as controls (sero-negative). Left ventricular wall motion and the left ventricular volumes were determined by ventricular cineangiography. Coronary arteriography was also performed. The sero-negative subjects had normal left ventricular wall motion and the left ventricular diastolic volume was 88 +/- 24 ml/m2. The response of heart rate to atropine was 50 +/- 8 (mean +/- SD) (range 40-65 beats/min). On the basis of the response to atropine, the chagasic patients were divided into groups with a normal response (greater than 40 beats/min) and those with an abnormal response (less than 40 beats/min). Sixty five per cent of those with a normal response had left ventricular apical aneurysms. The left ventricular end-diastolic volume was not significantly different from the sero-negative subjects (96 +/- 26 ml/m2). Six patients (30%) had a left ventricular diastolic volume between 110 and 140 ml/m2. Sixty two per cent of those chagasic subjects with an abnormal response had diffuse left ventricular hypokinesis, and the left ventricular end-diastolic volume was 192 +/- 49 ml/m2 (P less than 0.01). The response of heart rate and the left ventricular diastolic volume were inversely correlated in the chagasic patients (r = -0.88, P less than 0.01). Our results indicate that myocardial damage and the degree of left ventricular dilatation are more severe in chagasic patients with an abnormal response of their heart rate to atropine. Furthermore, the inverse correlation between these two variables is highly indicative of a relationship between the response of heart rate to atropine and the degree of left ventricular dysfunction.

Effect of low oral doses of disopyramide and amiodarone on ventricular and atrial arrhythmias of chagasic patients with advanced myocardial damage

Low-dose (7 mg/kg per day) disopyramide administration to arrhythmic chagasic patients decreased the frequency of ventricular extrasystoles in 4 of 17 patients (24%) and suppressed most complex ventricular arrhythmias in 12 of 15 patients (80%). This assessment was made from 72-h continuous Holter monitoring recorded during the course of this double blind, placebo-controlled randomized crossover study. Seven patients (41%) complained of anticholinergic side effects, but no contractile or conduction system depression was seen. Amiodarone (200 mg) given on a single blind, placebo-controlled basis to 9 of these patients reduced the frequency of ventricular extrasystoles in 6 of 9 patients (67%) and suppressed complex ventricular ectopy in 6 of 7 patients (85%). One patient was unable to tolerate this drug (11%). Both drugs seemed less effective in controlling supraventricular arrhythmias, although disopyramide eliminated paroxysms of supraventricular tachycardia in 9 of 13 (69%) and amiodarone in all 6 patients with this arrhythmia. Amiodarone appears to be a better antiarrhythmic drug for chagasic patients, due to its greater effectiveness and lower incidence of side effects.

Life expectancy analysis in patients with Chagas' disease: prognosis after one decade (1973-1983)

We studied the evolution of chronic Chagas' disease in 107 patients with a positive Guerreiro-Machado reaction and 22 non-chagasic, non-heart disease control subjects for a follow-up period of 3 to 10 years (mean follow-up of 4.9 years). After completion of invasive and non-invasive studies, chagasic patients were classified into four groups: IA (normal ECG, without heart disease; 18 patients); IB (normal ECG, early left ventricular segmental abnormalities; 13 patients); II (abnormal ECG, advanced myocardial damage, no signs of heart failure; 42 patients); and III (abnormal ECG, end-stage, congestive heart failure; 34 patients). One out of five group IA patients re-studied with invasive methods evolved to group IB (20%); 4 group IB patients evolved to group II (33%) and 6 group II patients evolved to group III (15%). The life expectancy of patients in groups IA and IB (normal ECG) was similar to that of our control group, whereas in groups II and III it was significantly decreased (P less than 0.001). Nine group II patients (23%) and 28 group III patients (82%) died during the follow-up period. Main terminal events were refractory congestive heart failure, sudden death and systemic thromboembolism. Our findings suggest that chronic Chagas' disease follows an evolutionary course from asymptomatic, normal ECG group I stage to arrhythmic (II) and congestive (III) stages. Subjects with a positive Guerreiro-Machado reaction showed a significantly lower life expectancy than our control group, but only when clinical and/or ECG abnormalities were identified.