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What a right bundle branch block hides



A 37 years old Bolivian male was referred for cardiac evaluation after finding a right bundle branch block on an ECG performed in medical check-up exam at work (figure 1).




Figure 1. 12 lead ECG showed sinus rhythm, first-degree atrioventricular block (PR interval prolongation of 210 ms), complete right bundle branch block with a convex ST-segment elevation and negative T waves in precordial leads (V1-V6).


The patient had neither prior medical history nor cardiovascular risk factors. There was no evidence of family history of cardiomyopathy or sudden death. He was completely asymptomatic except from occasional episodes of palpitations not related to efforts. Physical examination was normal and cardiac auscultation revealed wide splitting of the second heart sound due to the right bundle branch block.
Chest x-ray demonstrated a normal cardiac-to-thoracic width ratio. Blood test showed NT-proBNP of 102 pg/ml and creatinkinase of 387 ng/ml. Transthoracic echocardiogram demonstrated upper limits of the normal left ventricle volumes (VTD/VTS 75/30 ml/m2, LVEDd 54 mm, 115% of predicted) with no areas of dys-synergy and mild impairment of left ventricular systolic function (EF 50%) (figure 2).



Figure 2. Echocardiogram showing 4 chamber apical view and paraesternal long axis. Note mild dilatation of left ventricle.


Cardiovascular magnetic resonance (CMR) imaging was then performed for precise assessment of dimensions, contractility, and tissue characterization. CMR confirmed both mild left ventricular dilatation and systolic dysfunction (EF 50%). It revealed as well the presence of extensive myocardial fibrosis detected by late gadolinium enhancement (figure 3).


Figure 3. CMR showing widespread patched transmural late gadolinium enhancement located at basal segments of the interventricular septum, the basal lateral wall and at the left ventricle apex.

Questions

  • What is the suspected diagnosis in this patient?
  • Would you discharge the patient at this point? Or would you perform any additional tests?
  • Would you recommend any medication?
  • Would you consider this patient to be at high risk of sudden cardiac death? Would you recommend ICD implantation in this patient?

 

CASE RESOLUTION:

Taking into account patient origin from an endemic area, serological methods to detect IgG antibodies to Trypanosoma cruzi, enzyme-linked immunosorbent assay (ELISA) and immunofluorescent antibody assay (IFA) were performed to rule out the diagnosis of Chagas Disease (ChD). The patient had both positive values ELISA index of 8 and IFA >1/160, which confirms the diagnosis of chronic infection. The patient was also evaluated for gastrointestinal involvement with barium-contrast esophageal and colon radiographs which showed no abnormalities.
With the diagnosis of chronic Chagas cardiomyopathy (CChC), based on serology, ECG and echocardiographic findings despite lacking of symptoms, treatment with the antitrypanosomal agent Benznidazole was started with good tolerance at a dose of 100 mg tds for 60 days.
Ten months after the diagnosis, the patient had a cardiac arrest while he was playing tennis. Unfortunately he could not be resuscitated by emergency services and a forensic autopsy was performed. The gross and microscopic examination of the heart revealed the following findings: (Figures 4, 5, 6)


Figure 4. Heart weighted 395 g and externally right ventricle was mildly dilated at the base (A). Short-axis section showing minimal scarring located in interventricular septum (B)


Figure 5. Histologic examination of the left ventricle demonstrates diffuse myocyte hypertrophy with multiple foci of necrosis associated to mononuclear inflammatory infiltrates (A and B), scattered areas of replacement fibrosis (C) and occasional adipocyte transformation (D).


Figure 6. Focal myocarditis was also observed affecting the sinus node (A), the AV node (B) and the His bundle (C).


ChD is caused by infection with the protozoan parasite Trypanosoma cruzi. Historically, the disease occurred predominantly in rural areas of Latin America where poor housing conditions facilitates recurrent contact with infected vectors. However, given the new patterns of immigration and the introduction of successful programs to reduce transmission in endemic areas, the epidemiology of the disease is changing [1].
The natural history of Chagas heart disease comprises an acute phase, an indeterminate form, and a cardiomyopathy form in the chronic phase. Approximately one-third to one-half of patients eventually develops chronic Chagas cardiomyopathy (CChC), which is characterized by biventricular dilatation. Clinical manifestations range from asymptomatic to heart failure, cardiac arrhythmias, thromboembolism (systemic and pulmonary), and chest pain. The most common ECG abnormalities are right bundle branch block often associated with left anterior fascicular block and diffuse ST-T changes. Abnormal Q waves, various degrees of AV block, QT interval prolongation, and variation in the QT interval (QT dispersion) can also be seen. Echocardiography may demonstrate one or more areas of hypokinesia or dyskinesia. Left ventricular apical aneurysm is also common in patients with moderate to severe cardiac impairment [2]. Sudden cardiac death (SD) accounts for approximately 60% of deaths in patients with CChC. It is often precipitated by exercise and can be caused by ventricular tachycardia or fibrillation, asystole, or complete AV block [3]. Another relevant pathophysiologic mechanism of ventricular arrhythmias and sudden death in CChC may be related to the extensive myocardial sympathetic denervation [4]. Mortality rate for patients presenting with heart failure due to CChD is higher than that reported in other heart failure associated conditions [5].
Major risk factors for mortality in patients with CChC are heart failure, evidence of left ventricular dilatation or systolic dysfunction, and non-sustained ventricular tachycardia (NSVT). A risk score (Rassi score) for mortality has been developed and validated. Six independent predictors have been proposed: NYHA class III/IV (5 points), cardiomegaly on chest X-ray (5 points), left ventricular systolic dysfunction on echocardiogram (3 points), NSVT on Holter monitoring (3 points), low QRS voltage (2 points) and male gender (2 points). According to the Rassi score, our patient would have been classified as low risk (5 points), providing that Holter monitoring was not performed in our patient. In this study, the combination of left ventricular systolic dysfunction and NSVT was associated with particularly high risk (15.1 fold increase risk of death) [6].
Although data on treatment of chronic ChD are limited, most experts recommend antitrypanosomal therapy, using Benznidazole as first-line agent, to treat patients with chronic infection up to 50 years of age including those with evidence of early Chagas heart disease (eg, isolated ECG abnormalities) but not in those with advanced CChC [7,8]. The results from BENEFIT, a large multicenter randomized controlled trial of trypanocidal therapy in patients with Chagas heart disease is ongoing and will provide useful information.
Appropriate measures to reduce SD risk in patients with CChC are uncertain due to paucity of data. No randomized clinical trials had evaluated primary prevention of SD in patients with ChD. The 2008 American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) guidelines for device-based therapy of arrhythmias recommend ICD implantation for primary prevention in patients with non-ischaemic dilated cardiomyopathy with an LVEF ≤35 percent and NYHA functional class II or III. However, these guidelines include scant discussion of treatment of CChC. They note only that ICD implantation is reasonable for patients with ChD [9]. According to the international guidelines at the moment of our evaluation our patient did not have a definite indication to ICD implantation.

Conclusion:


Physicians around the world should become aware of the existence of Chagas cardiomyopathy and how to recognize and treat it. Risk stratification of these patients is very important due to the high incidence of sudden cardiac death in these patients. Information from ongoing studies is awaited.

References



1. Gascon J, Bern C, Pinazo MJ. Chagas disease in Spain, the United States and other non-endemic countries. Acta Trop 2010; 115:22.
2. Andrade JP, Marin Neto JA, Paola AA, et al. I Latin American Guidelines for the diagnosis and treatment of Chagas' heart disease: executive summary. Arq Bras Cardiol 2011; 96:434
3. Rassi A Jr, Rassi SG, Rassi A. Sudden death in Chagas' disease. Arq Bras Cardiol 2001; 76:75.
4. Miranda CH, Figueiredo AB, Maciel BC, et al. Sustained ventricular tachycardia is associated with regional myocardial sympathetic denervation assessed with 123I-metaiodobenzylguanidine in chronic Chagas cardiomyopathy. J Nucl Med 2011; 52:504.
5. Issa VS, Amaral AF, Cruz FD, et al. Beta-blocker therapy and mortality of patients with Chagas cardiomyopathy: a subanalysis of the REMADHE prospective trial. Circ Heart Fail 2010; 3:82.
6. Rassi A Jr, Rassi A, Little WC, et al. Development and validation of a risk score for predicting death in Chagas' heart disease. N Engl J Med 2006; 355:799.
7. Caryn Bern. Antitrypanosomal Therapy for Chronic Chagas‟ Disease. NEJM 2011; 364: 2527-3
8. Murcia L, Carrilero B, Saura D, Iborra MA, Segovia M. Diagnosis and treatment of Chagas disease. Enferm Infecc Microbiol Clin. 2013; 31 Suppl 1:26-34.
9. Epstein AE, DiMarco JP, Ellenbogen KA, et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices): developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. Circulation 2008; 117:e350.

Notes to editor


Marina Navarro, Alicia Mateo, José Vicente Campos, Cardiac Department, University Hospital Virgen Arrixaca, Murcia, Spain
The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.