We present a patient with severe nonischemic cardiomyopathy in whom the HeartLogic algorithm was activated on her Boston Scientific cardioverter defibrillator. She had an out-of-alert state for several months and had clinically “stable” heart failure with no hospitalizations in the last 6 months. A sudden and fast increase of the HeartLogic index preceded her presentation in the emergency ward by several days. The detailed readout of HeartLogic however had some atypical features for heart failure decompensation. The patient presented at the emergency department with an increased dyspnea and a dry cough. Clinical exam showed desaturation and was suggestive for an acute respiratory infection. Subsequent imaging with CT thorax and nasopharyngeal real-time polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 viral pneumonia (COVID-19). This case illustrates that a timely and detailed analysis of HeartLogic alerts could help in the early differentiation of disease in patients with severe heart failure.

Background Exercise capacity is an important aspect of quality of life in patients undergoing pacemaker implantation. Device algorithms for ventricular pacing avoidance have been developed to avoid unnecessary and potentially harmful effects of right ventricular pacing. However, little data exists on the immediate response of these algorithms to sudden AV block during exercise. Methods The ventricular pacing avoidance algorithms of four pacemaker manufacturers were tested in an ex‐vivo model. The RSIM‐1500‐USB Device‐Interactive Heart Simulator (Rivertek Medical Systems, Inc.) was used to simulate three different scenarios: the first one starting with an initially conducted atrial pacing rate of 60 min−1, the second one starting with an atrial rate of 120 min−1 and finally a scenario starting with an atrial rate of 150 min−1. In all three scenarios, the initially conducted atrial rate was followed by a sudden, long lasting episode of third‐degree AV‐block. The response to those scenarios was recorded for each of the (brand‐specific) ventricular pacing avoidance algorithms. Results In the first scenario, the simulation resulted in a ventricular pause of 1333 ms (Boston Scientific), 2000 ms (Medtronic and Microport), and 2340 ms (Biotronik). In the second and third scenario, different results were observed across devices. All simulations of the second and third scenario resulted in repetitive 2:1 block response (during eight cycles) in Boston Scientific and Biotronik devices. These scenarios were confirmed in patient cases. Conclusion Simulator based observations of unanticipated pacemaker‐induced 2:1 block response during exercise may explain clinical symptoms experienced by some patients having a two‐chamber pacemaker.