Leadless pacemakers offer an alternative to conventional pacing by eliminating lead- and pocket-related complications. However, their use during pregnancy remains very limited because of concerns related to radiation exposure. We describe the clinical experience of a 17-week pregnant patient who presented with episodes of dizziness, profound weakness, and syncope. Further evaluation revealed second-degree atrioventricular block, Mobitz type II, and transient third-degree atrioventricular block documented by Holter monitoring, indicating the need for permanent pacing. The patient underwent implantation of a Micra AV (Medtronic, USA) leadless pacemaker under fluoroscopic guidance using optimized radiation safety protocols. The estimated fetal absorbed dose was 1.4 mGy, well below reported thresholds for deterministic effects and associated with a very low additional radiation risk compared with background risks of congenital malformations and childhood cancer. The maternal effective dose was 15 mSv. Post-procedure follow-up demonstrated complete symptom resolution, an uncomplicated continuation of pregnancy, and delivery of a healthy infant. This case illustrates the practical feasibility of leadless pacemaker implantation during pregnancy when careful radiation minimization strategies are applied and adds real-world experience to the limited data available for critical pacing indications in pregnant patients.

Radiofrequency ablation (RFA) is generally considered a safe treatment for hepatocellular carcinoma. Although cardiovascular complications have been occasionally reported, they are primarily attributed to sedatives and analgesics or the vasovagal reflex. However, a unique case is presented where RFA itself was suspected of inducing a progressive atrioventricular disorder. An 80-year-old male underwent RFA for hepatocellular carcinoma. His electrocardiogram showed a first-degree atrioventricular block on admission. Prior to ablation, fentanyl and propofol were administered. Severe bradycardia developed immediately after initiation of ablation. RFA and propofol infusion were terminated, leading to prompt heart rate recovery. After approximately five minutes, ablation was resumed without propofol, but severe bradycardia recurred. The electrocardiogram during RFA revealed a complete atrioventricular block. Therefore, the procedure was terminated. A 12-lead electrocardiogram performed after the aborted procedure revealed progression to a second-degree AV block (Mobitz type II) requiring pacemaker implantation. The exact mechanism of this effect remains unclear, though progression of the atrioventricular conduction disorder was considered to be induced by RFA. Careful intraoperative patient management is crucial during RFA.

Leadless pacemaker (LPM) implantation in pediatric patients is increasingly considered as an alternative to conventional pacemakers, especially when femoral venous access is not feasible. We present the case of a 7-year-old child with Mobitz type II second-degree atrioventricular block who successfully underwent LPM implantation via the right internal jugular vein due to inadequate femoral vein diameter. A comprehensive literature review was conducted to summarize the outcomes of internal jugular vein approach in children. The transjugular approach demonstrates several advantages, including suitability for larger sheaths, reduced vascular complications, shorter implantation path, stable mid-septal positioning, and faster recovery. Preoperative evaluation of venous anatomy and patient-specific factors is critical. Although pericardial effusion and sensing issues may occur, the internal jugular vein represents a safe and effective alternative for LPM implantation in selected pediatric patients when femoral access is contraindicated.

A 41-year-old male with a history of preterm birth, intellectual disability, and refractory epilepsy on multiple anti-seizure medications with an active vagus nerve stimulation device (VNS) presented for progressive lethargy and a global decline in health. The symptoms began two years after placement of a second VNS, as the first was removed years earlier due to infection complications. At the time of the lethargy and global decline presentation, the VNS was set at an output of 3.25 mA. On admission to the hospital, telemetry showed frequent sinus pauses lasting 2 to 8.5 seconds. An electrocardiogram (EKG) showed a second-degree Mobitz type II atrioventricular block. A transthoracic echocardiogram showed an ejection fraction of 65% without valvular abnormalities. A sleep study showed mild sleep apnea. The electroencephalogram (EEG) did not show epileptiform activity correlated to these events. Previous workup included a transthoracic echocardiogram and a 30-day cardiac monitor, which had shown normal sinus rhythm. Complete resolution of sinus pauses occurred after the VNS device was turned off. Cardiac arrhythmias associated with VNS are exceedingly rare and can occur years after implantation. High clinical suspicion is required in patients with VNS devices who develop new-onset lethargy and/or atonic episodes without other causes. This case aligns with previously reported cases and provides more evidence of these rare but potentially life-threatening events.

An 8-year-old castrated male Miniature Poodle was referred due to polyuria, polydipsia and urinary incontinence, following 12 days of prednisolone administration (0.25 mg/kg q12h) for otitis externa. Upon physical examination, an abnormal heart rhythm was detected on cardiac auscultation without any associated clinical signs. Owing to suspected conduction abnormalities, electrocardiography (ECG) was performed, which revealed a Mobitz Type II second-degree atrioventricular (AV) block. Blood analysis revealed hyperglycaemia (> 500 mg/dL; reference interval [RI] = 65-118 mg/dL), elevated fructosamine (361 µmol/L; RI = 177-314 µmol/L) and β-hydroxybutyric acid concentrations (5.4 mmol/L; RI ≤ 2.5 mmol/L), leading to a diagnosis of diabetic ketosis. To manage the diabetic ketosis, porcine lente insulin (Caninsulin, MSD) was administered at a dose of 0.33 U/kg q12h. Three days after initiating insulin therapy, the clinical signs improved, a stable blood glucose curve with a nadir of 150 mg/dL was observed, and the β-hydroxybutyric acid concentration decreased to 1.4 mmol/L. Follow-up ECG confirmed resolution of the AV block. Subsequently, the diabetes mellitus (DM) was well managed, and the AV block did not recur. A strong association between DM and AV block is reported in humans. However, studies investigating the relationship between DM and AV block in veterinary medicine are limited. This case report describes the potential for acute-onset DM to induce cardiac conduction disturbances in dogs.

The terminology of second-degree atrioventricular block has evolved over time, thereby creating some confusion and misinterpretations. Strict adherence to standard terminology and the appropriate use of eponyms are important to avoid diagnostic errors.

Mobitz type II second-degree atrioventricular block (AVB) is an electrocardiographic pattern that describes what appears to be an all-or-none conduction without visible changes in the AV conduction time or PR intervals before and after a single non-conducted P wave. An unchanged PR interval after the block is a sine qua non of Mobitz type II block. A 2:1 AVB cannot be classified in terms of type I or type II AVB. The diagnosis of Mobitz type II block AVB requires a stable sinus rate, which is an important criterion because a vagal surge (generally benign) can cause simultaneous sinus slowing and AV nodal block, which can resemble Mobitz type II AVB. Atypical forms of Wenckebach AVB may be misinterpreted as Mobitz type II AVB when a series of PR intervals are constant before the block. Concealed His bundle or ventricular extrasystoles may mimic both Wenckebach and/or type II AVB (pseudo-AVB). Correctly identified Mobitz type II AVB is invariably at the level of the His-Purkinje system and is an indication for a pacemaker.

A 48-year-old woman was found hanged in the bathroom. She was wearing a Holter monitor, which was later analysed by a cardiologist. During autopsy, findings congruent with atypical hanging were collected. The ECG showed a 20 s asystole and four minutes later bradycardia, which progressed to a second-degree AV-block Mobitz I, then Mobitz II, then to a third-degree AV-block. Finally, only P waves could be observed, before heart action ceased. This is one of few cases reporting ECG-changes during hanging and might give further insight into the complex pathophysiology of this type of death.

A number of publications have claimed that Mobitz type II atrioventricular block (AVB) may occur during sleep. None of the reports defined type II AVB and representative electrocardiograms were either misinterpreted or missing. Relatively benign Wenckebach type I AVB is often misdiagnosed as Mobitz type II which is an indication for a pacemaker. Review of the published reports indicates that Mobitz type II AVB does not occur during sleep when it is absent in the awake state. Conclusion: There is no proof that sleep is associated with Mobitz type II AVB.

The year 2024 marks the centenary of Mobitz's description of type II second-degree atrioventricular block. Its definition remains valid to this day with only minor modification for the diagnosis of infranodal conduction block. Mobitz a century ago indicated that his type II atrioventricular block was associated with Stock-Adams attacks and a prolonged duration of the QRS complex before the eventual description of bundle branch block.