In a case report published in Frontiers in Cardiovascular Medicine, cardiologists from the Department of Cardiology at Wuhan Asia Heart Hospital documented a fatal instance of giant interventricular septal hematoma accompanied by multiple septal perforator artery ruptures following left bundle branch area pacing. Left bundle branch area pacing has emerged as a widely adopted physiological pacing modality in cardiac resynchronization therapy, designed to engage the native conduction system by advancing a pacing lead from the right ventricular septal surface deep into the interventricular septum toward the path of the left bundle branch. While previous case reports of procedure-induced giant septal hematomas described favorable clinical outcomes after timely intervention, this clinical record describes the first known domestic or international fatal outcome associated with the complication, which developed in a patient with severe, refractory heart failure.

The patient was a sixty-seven-year-old male with a four-year medical history of dilated cardiomyopathy and refractory heart failure who had experienced recurrent hospitalizations despite receiving long-term, standardized medical therapy. He presented with no reported family history of hereditary cardiomyopathy, and previous coronary angiography confirmed the absence of significant coronary artery stenosis or obstructive lesions. At the time of his admission, surface electrocardiography demonstrated sinus rhythm and complete left bundle branch block featuring a markedly widened QRS duration of 198 milliseconds. Transthoracic echocardiography calculated by the biplane Simpson method revealed a severely reduced left ventricular ejection fraction of 13.2 percent and an enlarged left ventricular end-diastolic diameter of 66 millimeters, while chest radiography demonstrated marked pulmonary congestion alongside an elevated serum N-terminal pro-B-type natriuretic peptide concentration of 9,121 picograms per milliliter.

Initial inpatient management focused on stabilizing hemodynamic and respiratory status through five days of intensive, guideline-directed anti-heart failure medical treatment, which led to symptomatic improvement and radiographically verified clearance of pulmonary congestion. Because of persistent ventricular dyssynchrony, profound systolic impairment, and electrical conduction delay, clinical providers scheduled the patient for cardiac resynchronization therapy defibrillator implantation under general anesthesia after obtaining written informed consent. The procedural design prioritized primary left bundle branch area pacing to correct the native bundle branch block; however, if left bundle branch block could not be adequately resolved through pacing alone, the clinical team intended to transition to left bundle branch-optimized cardiac resynchronization therapy involving an additional coronary sinus lead.

The implantation procedure was executed on June 13, 2025, utilizing endotracheal intubation and general anesthesia with two Medtronic 3830 active-fixation pacing leads. The operators positioned the first lead at the His bundle to establish an anatomical and electrophysiological mapping reference, while the second lead was screwed into the proximal segment of the left bundle branch area. Pacing through this second lead produced a QR pattern in surface lead V1, yielding a left ventricular peak activation time of 112 milliseconds at 3 volts and 100 milliseconds at 10 volts. A notable reduction in pacing impedance occurred during deeper advancement, prompting the operators to secure the lead at that depth without further penetration. To optimize pacing morphology and address conduction delay, the first 3830 lead was subsequently screwed into six separate anatomical sites across the left bundle branch area; despite these attempts, prolonged activation times persisted, indicating coexisting intraventricular conduction block.

Faced with incomplete electrical correction, the operators initiated coronary sinus lead placement to facilitate optimized resynchronization therapy. A Medtronic 4196 pacing lead was advanced through the coronary sinus into the mid-segment of the left ventricular lateral vein using a Medtronic 6250 delivery sheath, and a Medtronic 6935 defibrillation lead was actively fixed at the right ventricular apex. The reference 3830 lead was withdrawn from the septum and anchored in the right atrial septum. Due to the large caliber and smooth endothelial surface of the lateral vein, the left ventricular lead repeatedly dislodged into the main coronary sinus body during sheath manipulation. Because no suitable alternative venous branches were anatomically present, left ventricular coronary sinus lead placement was abandoned, concluding a total operative duration of 3.5 hours. Following extubation, postoperative electrocardiography revealed a narrowed QRS interval of 160 milliseconds.

Five hours following the completion of the procedure, the patient developed acute localized discomfort over the left infraclavicular device pocket and left anterior chest, accompanied by arterial hypotension measuring 92/59 millimeters of mercury. Immediate bedside transthoracic echocardiography identified a massive interventricular septal hematoma with a septal wall thickness expanding to 41 millimeters, producing bilateral ventricular cavity compression that primarily restricted the right ventricle, alongside a small pericardial effusion measuring between 5 and 11 millimeters. The cardiac care team established a diagnosis of interventricular septal hematoma secondary to septal perforator vessel injury, initiated volume expansion, and administered intravenous vasoactive infusions. An urgent surgical consultation concluded that immediate open surgical thoracotomy was not indicated, reserving invasive interventional maneuvers for impending clinical deterioration.

Six hours postoperatively, the patient exhibited acute clinical worsening characterized by profound diaphoresis, progressive hypotension, sinus tachycardia, cold extremities, and severe motor restlessness. Repeat echocardiographic evaluation revealed expansion of the pericardial effusion to depths between 8 and 17 millimeters, accompanied by near-complete diastolic collapse of the right ventricular chamber. The medical team performed emergent endotracheal intubation and initiated bedside venoarterial extracorporeal membrane oxygenation support before transferring the patient to the cardiac catheterization laboratory. Emergent pericardiocentesis drained 350 milliliters of gross bloody effusion. Subsequent emergency coronary angiography identified ruptures across six distinct septal perforator arteries, with active contrast extravasation directly entering the pericardial cavity from one injured branch.

During coronary angiography and attempted intervention, the patient developed multiple episodes of ventricular fibrillation and cardiac arrest accompanied by refractory circulatory shock. Because of the widespread nature of the microvascular injuries, transcatheter coil embolization was achieved in only one relatively large ruptured perforator branch. Despite continuous venoarterial mechanical circulatory support, aggressive fluid administration, multiple vasoactive and inotropic infusions, mechanical ventilation, and continuous pericardial decompression, the patient suffered irreversible cardiovascular collapse and died ten hours after the initial implantation procedure. Laboratory coagulation profiles, platelet counts, and perioperative medication reviews confirmed that no antiplatelet or anticoagulant agents had been administered before or during the procedure, excluding systemic coagulopathy as the cause of bleeding.

The authors contextualized the incident by reviewing published complication rates, noting that left bundle branch area pacing maintains a very low incidence of major adverse vascular events. The multicenter ChiCSP registry previously reported an interventricular septal hematoma incidence of 0.04 percent among 2,610 recipients, while a single-center cohort study evaluating 636 pacing cases detected three septal coronary artery fistulas and three septal venous fistulas without any septal hematomas. Within the authors’ hospital center, where nearly 2,000 left bundle branch area pacing procedures had been performed, this event represented the first observed case of severe septal hematoma. Previously published literature documented only sporadic cases, almost all of which involved patients with preserved baseline ventricular function, mild anatomical compression, no more than three vascular lacerations, and favorable recovery following conservative care or targeted intervention.

In analyzing the pathophysiological cascade, the authors concluded that repeated lead repositioning and prolonged procedural duration caused localized mechanical trauma to septal vessels. Subsequent progressive hematoma expansion elevated intraseptal wall tension, precipitating secondary lacerations of neighboring perforators outside the direct drill tract. This formed a self-amplifying cycle of hemorrhage and biventricular compression that proved fatal due to the patient’s depleted baseline cardiac reserve. Standard surgical repair was precluded by diffuse septal edema, tissue friability, and prohibitive operative risk, while trans-apical needle decompression was ruled out due to laceration risks. Based on these observations, the authors suggested that operators consider early procedure termination when lead manipulation exceeds three attempts or total operative time surpasses 2.5 hours in fragile patients, emphasizing that these thresholds represent experience-based, unvalidated hypotheses rather than established clinical guidelines.

Subject of Research: Fatal Interventricular Septal Hematoma Complicating Left Bundle Branch Area Pacing

Article Title: Case Report: Rupture of multiple perforating branches and fatal giant interventricular septal hematoma: a severe complication of left bundle branch area pacing

Article References: Li, J., Bao, Y., Han, H., Yi, H., & Yan, H. (2026). Case Report: Rupture of multiple perforating branches and fatal giant interventricular septal hematoma: a severe complication of left bundle branch area pacing. Frontiers in Cardiovascular Medicine, 13, Article 1896456. https://doi.org/10.3389/fcvm.2026.1896456

Image Credits: AI Generated

DOI: 10.3389/fcvm.2026.1896456

Keywords: cardiology, left bundle branch area pacing, interventricular septal hematoma, heart failure, cardiac resynchronization therapy, septal perforator rupture, extracorporeal membrane oxygenation, case report, Case, Report, Rupture, multiple