A 44-year-old El Salvadorian immigrant with no applicable medical history suffered a ventricular fibrillation arrest while lifting a bag of potatoes. A post-arrest electrocardiogram showed atrial fibrillation with a slow ventricular response, right bundle branch block with left anterior fascicular block, and a variable QT interval (on one occasion 554 msec). No ST-segment elevation was noted. An echocardiogram post-arrest showed normal left ventricular size, ejection fraction of 20% with worse function of the basal inferior/inferolateral segments, right ventricular dilatation, and severe hypokinesis. Troponin was 0.078 peaking at 6.1. An electrolyte panel was normal. A coronary angiogram was performed, and no obstructive coronary artery disease was noted.
What would be the single best test to diagnose his arrhythmogenic condition?
The correct answer is: A. Trypanosoma cruzi IgG testing
As an El Salvadorian immigrant to the United States, this patient has a baseline risk of approximately 3.45% of having Chagas disease.1 Latin American immigrants from Chagas-endemic countries in the United States who have bifascicular block have an 18% risk of Chagas.2 Sudden death is a classic presentation for Chagas disease because of the focal scarring that triggers re-entrant ventricular arrhythmias, particularly scar in the basal inferolateral wall.
Answer B is not correct because, as noted above, this patient has a probability of at least 18% of having Chagas cardiomyopathy, which is higher than his risk of long QT syndrome. Answer C is not correct because although cardiac sarcoidosis has several phenotypic similarities with Chagas cardiomyopathy, including high rates of right bundle branch block, bradyarrhythmias, and tachyarrhythmias, the likelihood of Chagas disease is much higher in a patient from a Chagas-endemic country. Answer D is not correct because although there are several suggestive findings of Chagas cardiomyopathy on cardiac MRI, including focal scarring noted by gadolinium uptake and the classic apical aneurysm, these findings are suggestive but not diagnostic. Right ventricular dysplasia is still a much less likely clinical entity than Chagas disease in this setting.
Although essential for the diagnosis, serologic testing for Chagas disease (Trypansoma cruzi IgG serology) is a send-out laboratory test at most institutions with a resultant up to 7-day delay in diagnosis; therefore, appropriate imaging should be ordered while waiting for the results. When the diagnosis is suspected for other clinical presentations, such as heart failure or stroke, cardiac MRI is a valuable tool not only for assessing the apex in a patient in whom echocardiographic imaging is suboptimal even with contrast media, but also to quantify scar burden because Chagas patients with extensive scar may have a risk of sudden cardiac death high enough to consider placement of an automated implantable cardioverter-defibrillator for primary prevention. In this case, for instance, this patient's ejection fraction rose to 50% 1 week after his arrest, with persistent hypokinesis of the basal inferolateral wall.
Data suggest that Chagas disease is far more common in the United States than many clinicians expect. Between 13% and 19%3,4 of patients from Chagas-endemic countries with nonischemic cardiomyopathy have Chagas disease, and 7.5%5 of a similar population with pacemakers have Chagas disease as the cause of their conduction system disease.
Meymandi SK, Forsyth CJ, Soverow J, et al. Prevalence of Chagas Disease in the Latin American-born Population of Los Angeles. Clin Infect Dis 2017;64:1182-8.
Traina MI, Hernandez S, Sanchez DR, et al. Prevalence of Chagas Disease in a U.S. Population of Latin American Immigrants with Conduction Abnormalities on Electrocardiogram. PLoS Negl Trop Dis 2017;11:e0005244.
Traina MI, Sanchez DR, Hernandez S, et al. Prevalence and Impact of Chagas Disease Among Latin American Immigrants With Nonischemic Cardiomyopathy in Los Angeles, California. Circ Heart Fail 2015;8:938-43.
Kapelusznik L, Varela D, Montgomery SP, et al. Chagas disease in Latin American immigrants with dilated cardiomyopathy in New York City. Clin Infect Dis 2013;57:e7.
Park S, Sanchez DR, Traina MI, et al. The Prevalence of Chagas Disease Among Latin American Immigrants with Pacemakers in Los Angeles, California. Am J Trop Med Hyg 2017;96:1139-42.