IntroductionCardiac implantable electronic devices (CIEDs), including permanent pacemakers and implantable cardioverter-defibrillators (ICDs), are widely used in the management of bradyarrhythmias, tachyarrhythmias, and conduction disorders. Although implantation techniques and device technology have advanced substantially, mechanical complications remain clinically relevant. Lead displacement continues to represent an important cause of device malfunction and may present with a broad spectrum of clinical manifestations.¹Twiddler syndrome is a well-recognized but uncommon mechanical complication first described by Bayliss and colleagues in 1968, in which rotation of the pulse generator within its subcutaneous pocket results in lead coiling, retraction, and eventual loss of effective myocardial contact.² Variants such as Reel and Ratchet syndromes have since been described, differing primarily in the direction and mechanism of generator manipulation.³⁻⁴ Although the overall incidence is low, reported between 0.07% and 7%,⁵ presentations range from asymptomatic loss of capture to inappropriate ICD shocks and rare cases of sudden cardiac death.⁶⁻⁷When lead migration occurs proximally into the superior vena cava (SVC) or right atrium, pacing impulses may stimulate adjacent extracardiac structures, most notably the phrenic nerve, resulting in rhythmic diaphragmatic or abdominal wall contractions. These symptoms may be misinterpreted as arrhythmia, neuromuscular disease, or anxiety, leading to diagnostic delay.⁸ We report an early post-implantation presentation of right hemidiaphragmatic twitching due to ventricular lead migration into the SVC and highlight diagnostic and management considerations.
