Abnormal heart rhythms pose risk in cardiac sarcoidosis
Study looks at cardiac activity in patients with implanted heart devices
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Among people with cardiac sarcoidosis and implanted heart devices, sustained ventricular arrhythmias (abnormal heartbeats that start in the heart’s lower chambers) occurred most often in those with more severe heart involvement, a study in the U.K. showed.
Still, about one in five patients with less severe heart involvement, reflected by the absence of conventional indications for an implanted heart device, experienced sustained ventricular arrhythmias within five years, the data showed.
Sustained ventricular tachycardia (fast heartbeat driven by the heart’s lower chambers) and impaired left ventricular ejection fraction (LVEF, the proportion of blood pumped out with each heartbeat) at the study’s start were found to be independent predictors of future ventricular arrhythmias.
“These findings support continued device surveillance, repeated longitudinal risk reassessment, and integrated clinical-imaging decision-making in [cardiac sarcoidosis],” the researchers wrote.
The study, “Life-threatening ventricular arrhythmias in cardiac sarcoidosis with implantable devices: Incidence and predictors in a UK cohort,” was published in Current Problems in Cardiology.
Implanted devices help spot heart problems
Sarcoidosis is characterized by granulomas (small clusters of inflammatory cells) in various organs and tissues. When granulomas form in the heart muscle, it’s called cardiac sarcoidosis, which is associated with abnormal heart rhythms (arrhythmias). This can lead to heart failure and sudden cardiac death.
Implantable heart electronic devices are used to monitor or correct arrhythmias and prevent heart failure. Examples include pacemakers, implantable cardioverter-defibrillators, and cardiac resynchronization therapy units.
However, there is little data on the burden of sustained ventricular arrhythmias among cardiac sarcoidosis patients in the U.K. with implanted heart devices.
The researchers analyzed data from 275 cardiac sarcoidosis patients with implanted heart devices who were referred to a large U.K. hospital. Participants’ mean age at the time of device insertion was 54.5, and two-thirds (66.2%) were men.
A few (2.5%) had a diagnosis of definite cardiac sarcoidosis confirmed by heart biopsy, while 45.5% had highly probable disease with biopsy evidence outside the heart. The remaining 52% had probable disease, as determined by a specialist team. A biopsy involves collecting a tiny sample of tissue to be observed under a microscope.
Patients were divided into three groups based on 2014 Heart Rhythm Society’s criteria for insertion of an implantable cardioverter-defibrillator, which monitors life-threatening fast heartbeats and can reset the heart rhythm back to normal.
A total of 114 participants (41.5%) had Class 1A indications, including a history of cardiac arrest, sustained ventricular arrhythmias, or a low LVEF (below 35%), that make the device insertion a recommended approach.
About a third (33.1%) had Class 2A indications, in which the device is considered due to fainting or near fainting with an arrhythmic cause, a separate need for a pacemaker, or sustained arrhythmias triggered during programmed electrical stimulation.
The remaining one-quarter of patients (25.5%) had neither Class 1A nor 2A indications, meaning they had no conventional indications for an implantable cardioverter-defibrillator.
Before implantation (baseline), more than half (58.5%) had heart failure and more than one-third (37.1%) had high-grade atrioventricular block, or interrupted electrical signals between the upper and lower chambers. About one-quarter (25.8%) had a history of sustained ventricular tachycardia, all of them with Class IA indications.
Class IA patients had significantly worse heart abnormalities at baseline, including larger left ventricles, lower LVEF, and greater extent of late gadolinium enhancement (LGE), or active inflammation or scarred tissue in the heart muscle as assessed with cardiac MRI (CMR). This group was also significantly more likely to be on an anti-arrhythmic medication and at least one guideline-directed medical therapy for heart failure.
One year after device implantation, the frequency of sustained ventricular arrhythmias was 9.7% in the Class 1A group, 5.6% in the Class 2A group, and 7.4% in the neither group. At five years, the estimates were 46.1%, 19.3%, and 18.7%, respectively. The results remained consistent when the team considered only patients with definite and highly probable cardiac sarcoidosis.
This highlights that even though the highest rates were found among patients with more severe heart problems (Class 1A), about one in five of those without conventional indications for an implantable cardioverter-defibrillator still experienced sustained ventricular arrythmias over five years.
The risk “remained clinically meaningful among those without Class I indications,” the researchers wrote.
Statistical analyses showed that baseline sustained ventricular tachycardia and low baseline LVEF were independently associated with future ventricular arrhythmias, suggesting that they “should … remain central to clinical decision-making,” the team wrote.
“Future work should prospectively validate time-varying LGE thresholds, develop dynamic risk models using serial CMR/PET and device diagnostics, and test whether imaging-guided immunomodulation or heart-failure therapies reduce arrhythmic events in this population,” the researchers concluded.
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