Two Undesired Conditions Resulting From T-Wave Oversensing in Two Patients With Hypertrophic Cardiomyopathy: Inappropriate ICD Shocks and Pacemaker Dysfunction

T-wave oversensing (TWOS) is generally seen in patients with hypertrophic cardiomyopathy (HCM) and is a rare cause of inappropriate implantable cardioverter defibrillator (ICD) shocks. TWOS rarely causes pacemaker dysfunction. In this paper, we present two patients with hypertrophic cardiomyopathy (HCM). One patient had several inappropriate ICD shocks, and the other experienced pacemaker dysfunction due to TWOS. ICD interrogation revealed that TWOS occurred only during high heart rates in the first patient. Attempts to fix TWOS, including a higher beta blocker dose, electrophysiology study, and ICD re-programming, were unsuccessful. We replaced the previously implanted ICD generator (Medtronic Maximo II DR) with a new one that has a specific diagnostic algorithm to prevent TWOS (Medtronic Protector). After replacement, the patient did not have any inappropriate shocks due to TWOS. The second patient had bradycardic pacemaker rhythm due to TWOS. Although we reposed, the ventricular lead did not stabilize with an adequate threshold, and thus we decided to replace the lead with a new one. The pacemaker dysfunction disappeared after the lead replacement. Patients with HCM must be observed carefully for these undesired conditions.