Electrocardiographic abnormalities and left ventricular systolic function in Chagas' heart disease

Electrocardiogram abnormalities in chronic Chagas cardiomyopathy correlate with scar mass and left ventricular dysfunction as assessed by cardiac magnetic resonance imaging

Electrocardiographic (ECG) abnormalities are frequently identified in Chronic Chagas cardiomyopathy (CCC) patients and advanced abnormalities are related to a worse prognosis. Cardiac Magnetic Resonance (CMR) can precisely assess ventricular systolic dysfunction and quantify myocardial fibrosis (MF), both identified as prognostic factors. We sought to investigate if ECG abnormalities in CCC patients were associated with more severe myocardial involvement as evaluated by CMR.

METHODS

CCC patients with 12‑lead ECG and CMR closely obtained were included. ECG analysis evaluated rhythm, presence, and type of intraventricular conduction disturbances (IVCD) and, ventricular premature beats (VPB). CMR short-axis cine and late gadolinium enhancement images were evaluated to obtain left and right ventricular ejection fractions and MF mass, respectively. Statistical significance was set in 5%.

RESULTS

194 CCC patients (98 women, 56 ± 14 years) were evaluated, and no IVCD was detected in 71. The most common IVCD was the association of right bundle branch block and left anterior fascicular block (RBBB+LAFB) in 58 patients, followed by isolated RBBB in 34, isolated LAFB in 17, and left bundle branch block (LBBB) in 14 patients. Of patients with no IVCD, 63% had MF and the burden of fibrosis (no IVCD - 7.4 ± 8.6%; RBBB - 6.6 ± 6.5%; p = 1.00), as well as left ventricular ejection fraction (LVEF) (no IVCD - 52 ± 14%; RBBB - 55 ± 10%; p = 1.00) were similar to patients with isolated RBBB. Left conduction system impairment was associated with lower LVEF (LAFB - 39 ± 15%; RBBB+LAFB- 41 ± 15%; and LBBB - 35 ± 15%; p < 0.001) and more MF (RBBB+LAFB - 12.2 ± 10.4%; LBBB - 10.6 ± 7.5%; and LAFB - 12.0 ± 7.0%; p < 0.001). The univariable model showed that the presence of MF was related to RBBB+LAFB (OR 5.0; p = 0.001) and VPB (OR 6.3; p = 0.014). After adjustment for age, gender, and different risk factors in a multivariable model, the same findings were still significantly related to CMR myocardial fibrosis (RBBB+LAFB OR 5.0; p = 0.002 / VPB OR 6.9; p = 0.015).

CONCLUSIONS

ECG without IVCD does not exclude serious cardiac abnormalities in CCC, and isolated RBBB seems to have a benign course. The presence of VPB and left branch conduction impairment, especially LAFB associated with RBBB, indicate a more severe cardiac involvement.

Rare Pathogenic Variants in Mitochondrial and Inflammation-Associated Genes May Lead to Inflammatory Cardiomyopathy in Chagas Disease

Abstract

Cardiomyopathies are an important cause of heart failure and sudden cardiac death. Little is known about the role of rare genetic variants in inflammatory cardiomyopathy. Chronic Chagas disease cardiomyopathy (CCC) is an inflammatory cardiomyopathy prevalent in Latin America, developing in 30% of the 6 million patients chronically infected by the protozoan Trypanosoma cruzi, while 60% remain free of heart disease (asymptomatic (ASY)). The cytokine interferon-γ and mitochondrial dysfunction are known to play a major pathogenetic role. Chagas disease provides a unique model to probe for genetic variants involved in inflammatory cardiomyopathy.

Methods

We used whole exome sequencing to study nuclear families containing multiple cases of Chagas disease. We searched for rare pathogenic variants shared by all family members with CCC but absent in infected ASY siblings and in unrelated ASY.

Results

We identified heterozygous, pathogenic variants linked to CCC in all tested families on 22 distinct genes, from which 20 were mitochondrial or inflammation-related – most of the latter involved in proinflammatory cytokine production. Significantly, incubation with IFN-γ on a human cardiomyocyte line treated with an inhibitor of dihydroorotate dehydrogenase brequinar (enzyme showing a loss-of-function variant in one family) markedly reduced mitochondrial membrane potential (ΔψM), indicating mitochondrial dysfunction.

Conclusion

Mitochondrial dysfunction and inflammation may be genetically determined in CCC, driven by rare genetic variants. We hypothesize that CCC-linked genetic variants increase mitochondrial susceptibility to IFN-γ-induced damage in the myocardium, leading to the cardiomyopathy phenotype in Chagas disease. This mechanism may also be operative in other inflammatory cardiomyopathies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10875-021-01000-y.

Association between typical electrocardiographic abnormalities and NT-proBNP elevation in a large cohort of patients with Chagas disease from endemic area

Chagas cardiomyopathy is the most harmful complication of Chagas disease. The electrocardiogram is a well-studied exam and has been considered an important tool for detection and evaluation of Chagas cardiomyopathy since the first years of its description. Many of its abnormalities have been described as associated with a worse prognosis. Serum BNP levels were described as inversely related to the left ventricular ejection fraction and as an independent predictor of death. It was not reported how electrocardiographic alterations correlate to NT-proBNP and its analog. The present study aims to describe the baseline electrocardiograms of a large cohort of patients with Chagas disease from endemic area and to establish an association between the number of electrocardiogram alterations and high levels of NT-ProBNP in Chagas disease patients. This study selected 1959 Chagas disease patients in 21 municipalities within a limited region in the northern part of the State of Minas Gerais (Brazil), 1084 of them had Chagas cardiomyopathy. NT-proBNP levels were suggestive of heart failure in 11.7% of this population. One or more electrocardiographic alterations have an Odds Ratio of 9.12 (CI 95% 5.62-14.80) to have NT-proBNP elevation. Considering the association between the number of 1, 2, and 3 or more alterations in electrocardiogram and NT-proBNP elevation, the ORs were 7.11 (CI 95% 4.33-11.67); 16.04 (CI 95% 9.27-27.77) and 47.82 (CI 95% 17.98-127.20), respectively. The presence and the number of typical electrocardiographic alterations of Chagas disease are independently associated with the severity of the cardiomyopathy.

Electrocardiogram in Chagas disease

Since the initial descriptions of Chagas cardiomyopathy (ChCM), the electrocardiography has played a key role in patient evaluations. The diagnostic criterion of chronic ChCM is the presence of characteristic electrocardiographic (ECG) abnormalities in seropositive individuals, regardless of the presence of symptoms. However, these ECG abnormalities are rarely specific to ChCM and, particularly among the elderly, can be caused by other simultaneous cardiomyopathies. ECG abnormalities can predict the occurrence of heart failure, stroke, and even death. Nevertheless, most prognostic studies have included Chagas disease (ChD) populations and, not exclusively, ChCM. Thus, more studies are required to evaluate the efficacy of ECG in predicting reliable prognoses in established chronic ChCM. This review exclusively discusses the role of the 12-lead ECG in the clinical evaluation of chronic ChD.

Electrocardiographic abnormalities in Trypanosoma cruzi seropositive and seronegative former blood donors

BACKGROUND

Blood donor screening leads to large numbers of new diagnoses of Trypanosoma cruzi infection, with most donors in the asymptomatic chronic indeterminate form. Information on electrocardiogram (ECG) findings in infected blood donors is lacking and may help in counseling and recognizing those with more severe disease.

OBJECTIVES

To assess the frequency of ECG abnormalities in T.cruzi seropositive relative to seronegative blood donors, and to recognize ECG abnormalities associated with left ventricular dysfunction.

METHODS

The study retrospectively enrolled 499 seropositive blood donors in São Paulo and Montes Claros, Brazil, and 483 seronegative control donors matched by site, gender, age, and year of blood donation. All subjects underwent a health clinical evaluation, ECG, and echocardiogram (Echo). ECG and Echo were reviewed blindly by centralized reading centers. Left ventricular (LV) dysfunction was defined as LV ejection fraction (EF)<0.50%.

RESULTS

Right bundle branch block and left anterior fascicular block, isolated or in association, were more frequently found in seropositive cases (p<0.0001). Both QRS and QTc duration were associated with LVEF values (correlation coefficients -0.159,p<0.0003, and -0.142,p = 0.002) and showed a moderate accuracy in the detection of reduced LVEF (area under the ROC curve: 0.778 and 0.790, both p<0.0001). Several ECG abnormalities were more commonly found in seropositive donors with depressed LVEF, including rhythm disorders (frequent supraventricular ectopic beats, atrial fibrillation or flutter and pacemaker), intraventricular blocks (right bundle branch block and left anterior fascicular block) and ischemic abnormalities (possible old myocardial infarction and major and minor ST abnormalities). ECG was sensitive (92%) for recognition of seropositive donors with depressed LVEF and had a high negative predictive value (99%) for ruling out LV dysfunction.

CONCLUSIONS

ECG abnormalities are more frequent in seropositive than in seronegative blood donors. Several ECG abnormalities may help the recognition of seropositive cases with reduced LVEF who warrant careful follow-up and treatment.

Pharmacological inhibition of transforming growth factor beta signaling decreases infection and prevents heart damage in acute Chagas' disease

Chagas' disease induced by Trypanosoma cruzi infection is an important cause of mortality and morbidity affecting the cardiovascular system for which presently available therapies are largely inadequate. We previously reported that transforming growth factor beta (TGF-beta) is implicated in several regulatory aspects of T. cruzi invasion and growth and in host tissue fibrosis. This prompted us to evaluate the therapeutic action of an inhibitor of TGF-beta signaling (SB-431542) administered during the acute phase of experimental Chagas' disease. Male Swiss mice were infected intraperitoneally with 10(4) trypomastigotes of T. cruzi (Y strain) and evaluated clinically for the following 30 days. SB-431542 treatment significantly reduced mortality and decreased parasitemia. Electrocardiography showed that SB-431542 treatment was effective in protecting the cardiac conduction system. By 14 day postinfection, enzymatic biomarkers of tissue damage indicated that muscle injury was decreased by SB-431542 treatment, with significantly lower blood levels of aspartate aminotransferase and creatine kinase. In conclusion, inhibition of TGF-beta signaling in vivo appears to potently decrease T. cruzi infection and to prevent heart damage in a preclinical mouse model. This suggests that this class of molecules may represent a new therapeutic agent for acute and chronic Chagas' disease that warrants further clinical exploration.

Valsalva maneuver in chagasic patients with documented past medical history of acute chagasic myocarditis

BACKGROUND

We studied the heart rate responses to the Valsalva maneuver in eight patients with documented past medical history of acute Chagas' disease.

METHODS

Four patients were studied 8-21 months after the acute episode and four, 58-68 months thereafter (age 25+/-8.65 years M+/-S.D.). Seventeen healthy subjects of similar age were included as controls (age 27+/-7.5 years, P=NS).

RESULTS

Baseline heart rate was higher in chagasic patients (88+/-15 beats/min) compared to controls (69.8+/-9.8, P=0.001). Maximum heart rate at phase II of the maneuver was also higher (114+/-16.3 vs. 101.5+/-9.9, P=0.02). Minimum heart rate at phase IV was, however, not different (57.4+/-10.4 vs. 63.3+/-7.3 P=NS). The magnitude of the absolute negative change at phase IV was larger in the chagasic patients, although, not different (-50.8+/-13.8 vs. -44+/-13.8, P=NS). The Valsalva index was 1.81+/-0.26 in the chagasic patients and 1.82+/-0.42 in the controls (P=NS). Minimum heart rate at phase IV correlated neither with the baseline heart rate (r=-0.28, P=NS) nor with the Valsalva index (r=-0.40, P=NS). The magnitude of the absolute negative change during phase IV correlated with, both, the baseline heart rate (r=-0.80, P<0.01) and the Valsalva index (r=-0.95, P<0.0001). The higher baseline high rate influenced the magnitude of the negative heart rate change, but not the minimum heart rate reached at phase IV.

CONCLUSIONS

Chagasic patients with proven past medical history of acute Chagas' disease had unimpaired heart responses to the Valsalva maneuver.

Electrocardiographic ventricular repolarization parameters in chronic Chagas' disease as predictors of asymptomatic left ventricular systolic dysfunction

Electrocardiographic repolarization parameters are potential markers of arrhythmogenic risk and have not been evaluated in Chagas' disease. The aim of this report was to investigate their associations with LV systolic function assessed by two-dimensional echocardiography. In a cross-sectional study involving 738 adult outpatients in the chronic phase of Chagas' disease, maximal QTc and T wave peak-to-end (TpTe) intervals, and QT, QTapex (QTa), IT and TpTe interval dispersions, and variation coefficients were measured and calculated from 12-lead standard ECGs. Clinical, radiological, ECG, and echocardiographic data were recorded. In bivariate statistical analysis, all repolarization parameters were significantly increased in patients with moderate or severe LV systolic dysfunction, and these patients showed more clinical, radiologic, and ECG abnormalities. Receiver operating characteristic curve analysis demonstrated that isolatedly QTd had the best predictive performance for LV dysfunction, with an 80% specificity and 67% sensitivity for values >60 ms in the subgroup of chagasic patients with abnormal ECGs and no heart failure. Multivariate logistic regression selected, as the best predictive model for LV dysfunction in this subgroup of patients, the presence of cardiomegaly on chest X ray (OR 14.06, 95% CI, 5.54-35.71), QTd >60 ms (OR 9.35, 95% CI, 4.01-21.81), male gender (OR 7.70, 95% CI, 2.98-19.91) and the presence of frequent premature ventricular contractions (PVCs) on ECG (OR 4.06, 95% CI, 1.65-9.97). This model showed 90% specificity and 71% sensitivity. In conclusion, QTd was associated to LV systolic function and could be used to predict asymptomatic dysfunction in chronic Chagas' disease. The presence of cardiomegaly, frequent PVCs, and male sex refined LV function stratification in these patients.

A narrow QRS does not predict a normal left ventricular function in Chagas' disease

Left ventricular (LV) systolic dysfunction is a major prognostic determinant in Chagas' disease (ChD), a potentially fatal disorder which affects nearly 20 million individuals in Latin America. Therefore, reliable screening methods are needed to identify patients in need of a detailed evaluation of LV function. Since previous reports have suggested that a prolonged QRS duration may be an accurate predictor of LV dysfunction, the relationship between QRS duration and LV function was evaluated in ChD patients, in order to determine whether a narrow QRS on surface electrocardiogram (ECG) predicts a normal LV function. Ninety-eight patients with ChD and no other cardiac or systemic illness were underwent standard 12-lead ECG and Doppler echocardiogram (echo) examination. An investigator (blinded to the echo data) measured manually the QRS duration. LV dysfunction was defined by the presence of LV dilatation (LV diastolic dimension > 55 mm), depressed LV ejection fraction (LVEF < 0.50), segmental contractile abnormalities (SCA) or LV aneurysm. QRS duration was significantly correlated with LV diastolic dimension (r = 0.44, P = 0.000) and LVEF (r = 0.24, P = 0.016). A significant percentage of patients with QRS < 100 ms had abnormal systolic LV parameters, including LV dilatation (8.1%), reduced EF (10.2%), SCA (42.8%) and LV aneurysm (14.2%). A narrow QRS does not exclude the presence of significant global and segmental LV dysfunction in ChD patients. Since these abnormalities have prognostic and therapeutic implications, further evaluation of LV systolic performance is desirable in such patients.

Chagas' heart disease and the autonomic nervous system

The autonomic nervous system is abnormal in patients with advanced Chagas' heart disease. Most researchers consider these autonomic abnormalities as primary, specific and irreversible. However, when and why these abnormalities appear in the natural history of Chagas' disease, is still the subject of intense controversy. Recent morphological and functional studies strongly suggest that the sympathetic and the parasympathetic abnormalities are preceded by myocardial damage and left ventricular dysfunction. Moreover, chagasic patients with cardiac failure benefit from drugs which antagonize neurohumoral activation. Consequently, the abnormalities of the autonomic nervous system of chagasic patients are very likely secondary and partially reversible.

Plasma norepinephrine, myocardial damage and left ventricular systolic function in Chagas' heart disease

The functional status of the sympathetic nervous system in Chagas' heart disease is still the subject of intense controversy. To determine the nature of the abnormalities of the sympathetic nervous system, we measured the plasma norepinephrine concentration of chagasic patients with varying degrees of myocardial damage. Thirty-six patients with positive serology for Chagas' disease were studied. Twenty patients were in Functional Class I (New York Heart Association), 10 were in Functional Class II and six were in Functional Classes III-IV. Cardiac catheterization was performed in 24 patients. The asymptomatic patients had a plasma norepinephrine concentration (121 +/- 37 pg/ml, mean +/- S.D.) not different from normal controls (103 +/- 59 pg/ml). The symptomatic patients, however, had a significantly elevated plasma norepinephrine concentration (665 +/- 354 pg/ml, P < 0.001). The baseline heart rate of the asymptomatic and symptomatic patients directly correlated with the plasma norepinephrine concentration (r = 0.69, P < 0.0001). The symptomatic patients had larger ventricular volumes, higher left ventricular end-diastolic pressures and lower ejection fractions than the asymptomatic patients and normal controls. The plasma norepinephrine concentration correlated linearly with the left ventricular end-diastolic volume (r = 0.77, P < 0.0001), and non-linearly with the ejection fraction (r = -0.70, P < 0.0001) and the left ventricular end-diastolic pressure (r = 0.53, P < 0.007). These results indicate that, in Chagas' heart disease as in most other cardiac diseases, sympathetic nervous system activation is a late and compensatory phenomenon. In other words, sympathetic activation is very likely related to the progressive impairment of left ventricular function.

Ventricular function in Chagas' heart disease

Invasive and noninvasive methods used to evaluate ventricular function in Chagas's disease are reviewed. The traditional indices of overall ventricular performance reflect the interaction of preload, contractility, afterload and heart rate. Therefore, they are unable to distinguish changes in contractility from modifications of loading conditions. The role of ventricular function as a predictor of mortality in chronic Chagas' heart disease is discussed. Ventricular function abnormalities in patients with indeterminate and digestive forms of Chagas' disease are especially emphasized. Finally, the evidence of early impairment of diastolic performance in digestive forms of Chagas' disease are especially emphasized. Finally, the evidence of early impairment of diastolic performance in patients with Chagas' disease is presented.

Plasma renin activity in chagasic patients with and without congestive heart failure

Chagasic patients with advanced heart disease have fluid retention-dependent symptoms. Since fluid retention is mostly dependent on the renin-angiotensin-aldosterone system, chagasic patients with congestion related symptoms should have activation of the renin-angiotensin-aldosterone system. The purpose of this investigation was to determine the plasma renin activity baseline values of chagasic patients with and without congestive heart failure. Twenty-eight patients with positive serology for Chagas' disease were studied. Nineteen patients were asymptomatic (functional class I New York Heart Association) and nine were symptomatic (functional classes II-IV). Cardiac catheterization and ventricular cineangiography were performed on 20 patients. The symptomatic patients had significantly higher plasma renin activity levels (4.11 +/- 1.03 ng/ml/h) than the asymptomatic patients (1.08 +/- 0.11 ng/ml/h, P < 0.001) and the normal sedentary controls (1.65 +/- 0.22 ng/ml/h, P < 0.05, mean +/- S.E.). The plasma renin activity baseline values of the asymptomatic and symptomatic patients correlated directly with the baseline heart rate (r = 0.77, P < 0.0001). The symptomatic patients had larger ventricular volumes, moderately depressed ejection fractions and increased left ventricular end-diastolic pressures. The plasma renin activity baseline values also correlated directly with the left ventricular diastolic pressures (r = 0.70, P < 0.0006) and with the left ventricular diastolic (r = 0.66, P < 0.001) and systolic volumes (r = 0.67, P < 0.001). These results indicate that chagasic patients with fluid retention-dependent symptoms and hemodynamic evidence of left ventricular systolic dysfunction have activation of the renin-angiotensin-aldosterone system.

Apical left ventricular aneurysms and cardiac parasympathetic innervation in Chagas' heart disease

Left ventricular apical aneurysms are present in Chagasic patients who have normal cardiac parasympathetic innervation. Cardiac parasympathetic abnormalities are found, in later stages of the disease, when diffuse myocardial damage and ventricular dilatation are already present. The apical region of the left ventricle is also affected in several acute and chronic non-Chagasic cardiac diseases. Therefore, thinning of the left ventricular apex, with aneurysm formation, may be a non-specific myocardial sequelae, secondary to myocardial damage.

Cardiac autonomic control mechanisms in Chagas' heart disease. Therapeutic implications

According to the neurogenic theory of Chagas' heart disease, the cardiac parasympathetic abnormalities of chagasic cardiac patients are due to a selective destruction of the cardiac parasympathetic neurons. Trypanosoma cruzi would selectively destroy the cardiac vagal neurons, during the acute stage of the disease. However, these cardiac parasympathetic abnormalities are found mainly in chagasic patients who are in very advanced stages of the disease. Furthermore, the extent of cardiac parasympathetic involvement correlates with the degree of left ventricular dilation. Cardiac parasympathetic abnormalities, and a reciprocal sympathetic hyperactivity are also present in non-chagasic cardiac patients. Modern medical treatment, with sympatholytic drugs, prevents ventricular dilatation and prolongs life in these non-chagasic cardiac patients. Consequently, if chagasic cardiac patients have ventricular dilatation-related parasympathetic abnormalities; it is of the utmost importance to ask: first, do they also have a progressive activation of their neurohumoral systems?; and second, would they benefit from sympatholytic drugs?.

Chagas' disease

Chagas' disease, caused by Trypanosoma cruzi, is an important cause of morbidity in many countries in Latin America. The important modes of transmission are by the bite of the reduviid bug and blood transfusion. The organism exists in three morphological forms: trypomastigotes, amastigotes, and epimastigotes. The mechanism of transformation and differentiation is currently being explored, and signal transduction pathways of the parasites may be involved in this process. Parasite adherence to and invasion of host cells is a complex process involving complement, phospholipase, penetrin, neuraminidase, and hemolysin. Two clinical forms of the disease are recognized, acute and chronic. During the acute stage pathological damage is related to the presence of the parasite, whereas in the chronic stage few parasites are found. In recent years the roles of tumor necrosis factor, gamma interferon, and the interleukins in the pathogenesis of this infection have been reported. The common manifestations of chronic cardiomyopathy are arrhythmias and thromboembolic events. Autoimmune, neurogenic, and microvascular factors may be important in the pathogenesis of the cardiomyopathy. The gastrointestinal tract is another important target, and "mega syndromes" are common manifestations. The diagnosis and treatment of this infection are active areas of investigation. New serological and molecular biological techniques have improved the diagnosis of chronic infection. Exacerbations of T. cruzi infection have been reported for patients receiving immuno-suppressive therapy and for those with AIDS.

Gap junction distribution is altered between cardiac myocytes infected with Trypanosoma cruzi

Conduction disturbances frequently accompany both acute and chronic Chagas' disease. To explore the possibility that changes in gap junction distribution or abundance might play a role in these disturbances, we have investigated intercellular communication between rat neonatal cardiac myocytes in cultures infected with Trypanosoma cruzi. Contractile activity of infected cells was characterized by regional asynchrony within the culture as well as by irregular contraction patterns. Junctional conductance between infected cell pairs was found to be significantly lower than in uninfected cell pairs, and the rapidity and extent of intercellular transfer of the dye lucifer yellow was markedly reduced between infected cells. Immunocytochemical studies demonstrated that the parasitic infection significantly decreased connexin43 expression at junctional membrane regions, correlating with the detected functional uncoupling. These findings of reduced gap junction abundance and function in trypanosome-infected cells may provide important insight into the pathogenesis of the cardiac arrhythmias that attend Chagas' disease.