Understanding Cardiac Sarcoidosis: Interview with Frank Bogun, MD

Interview by Jodie Elrod
Interview by Jodie Elrod
New research regarding cardiac sarcoidosis shows that radiofrequency catheter ablation of ventricular tachycardia in these patients can be effective. Dr. Frank Bogun of the University of Michigan explains his findings. Tell us about cardiac sarcoidosis. How does it affect the heart? Sarcoidosis most often affects the lymphatic system. It is not known how often it actually affects the heart. The numbers are based on autopsy studies and range between 25-75% (i.e., finding granulomas within the heart on autopsy). It is clinically apparent in only 5% of patients with sarcoidosis elsewhere. Who does it affect? What are its causes? How many patients are affected? The annual incidence of sarcoidosis varies from one geographic region to another; it is up to 40 per 100,000 people in Northern Europe. In the United States, the annual incidence is highest in African Americans (36 cases per 100,000 people, as compared to Caucasian Americans in which it is 11 per 100,000). It is a multisystem inflammatory disease and its origin is not well understood. Environmental factors and genetic susceptibility play a role in the pathogenesis. How is cardiac sarcoidosis generally treated? It is treated with immunosuppression including steroids. Tell us about the multicenter study. How many patients were followed? What was the study objective? We have a multicenter registry of cardiac sarcoidosis that was started here at the University of Michigan about four years ago. The purpose of this registry is to include centers that have a special interest in treatment and management of patients with cardiac sarcoidosis. The main objective of the registry is to help better understand the pathogenesis and disease manifestations of cardiac sarcoidosis in order to improve management of this disease condition and to improve outcome in these patients. At the University of Michigan, we follow about 80 patients with cardiac sarcoidosis. There are many projects that we are currently looking at in these patients, the role of ventricular tachycardia (VT) ablation being one of them. Why can the management of VT be especially difficult in patients with cardiac sarcoidosis? As far as we know, the disease process often is initiated in the myocardium and reaches either the epicardium or endocardium by extension of the inflammatory process. This makes the ablation procedure more challenging, especially if the disease process is located intramurally. It may be reachable neither by an endocardial nor by an epicardial approach. A cardiac MRI with delayed enhancement can help to regionalize the disease process and indicate whether scarring is located intramurally, epicardially, endocardially or transmurally. How many VTs were induced? What was the most frequent type of VT circuit found? In the study that we published in Heart Rhythm,1 we were able to induce a total of 44 VTs in nine patients. The most frequent anatomical location of reentry circuits that could be identified was in the peritricuspid valve area. This area has been described in other disease processes that involve the right ventricle like arrhythmogenic right ventricular dysplasia (ARVD). ARVD is a great imitator of sarcoidosis, and this needs to be kept in mind as the treatment for ARVD is fundamentally different. Was treatment effective for these patients? These were long ablation procedures, and they resulted in substantial reduction in the arrhythmic burden in these patients. When is the expected completion of the study? Our registry continues to enroll patients, to help us answer not just this question about the management of VT in these patients, but also other questions regarding prognosis, diagnosis, outcomes and risk stratification. What further research is needed in the treatment of cardiac sarcoidosis? Lots! This starts with making the diagnosis of cardiac involvement in patients with sarcoidosis. Cardiac MRI with delayed enhancement is particularly promising in this regard. In the case of cardiac involvement, risk stratification for sudden cardiac death is particularly important and is not adequately addressed in current guidelines. Cardiac MRI might be helpful in this regard, too. One also has to recognize that sarcoidosis might predominantly affect the heart and there might be no other organ manifestations, which might make the correct diagnosis challenging. The role of immunosuppression is not clear in patients with cardiac sarcoidosis. We do know, however, that earlier institution of immunosuppression in the disease progress seems to improve prognosis in cardiac sarcoidosis. Of course, another important question is to find out the determinants of cardiac involvement. Is there anything else you’d like to add? Yes. As cardiac sarcoidosis is a rare condition, a single center is less likely to come up with all the answers needed to adequately tackle this disease. We thought that a multicenter registry might be beneficial in order to help find some answers to these questions. The hospitals currently involved in this registry include the University of Michigan, St. John Hospital in Detroit, the University of Chicago, and Johns Hopkins Hospital. If there is interest from other centers in participating, they can send an email to fbogun@umich.edu.