Redefining the blanking period following pulsed-field ablation in patients with atrial fibrillation.

BACKGROUND: Recurrence during the 3-month blanking period following radiofrequency ablation of atrial fibrillation (AF) is typically not considered as a predictor for late recurrence. OBJECTIVE: We investigated the significance of early recurrence as a risk factor for late recurrence in AF patients receiving pulsed-field ablation (PFA). METHODS: Consecutive patients undergoing PFA were prospectively followed-up for 1 year. All patients received isolation of pulmonary veins. Additional ablations were performed per operator's discretion. Following the procedure all remained on their previously ineffective antiarrhythmic drugs (AAD) during the 2-month blanking period after which the AADs were discontinued. Early recurrence was defined as atrial arrhythmia of > 30 second duration during the 3-mo blanking period and any recurrence beyond 3-mo was considered as late recurrence. RESULTS: A total of 337 patients undergoing PFA for AF were included. Early recurrence was recorded in 53 (15.7%) patients; 10 in the 1st month, 12 in the 2nd month and 31 in the 3rd month. Of the 10 patients having recurrence during the 1st month, 7 (70%) remained in sinus rhythm after cardioversion whereas 3 (30%) underwent redo because of late-recurrence. At 1 year, all patients with recurrence during the 2nd and 3rd month, experienced late-recurrence of which 10/12 and 27/31 underwent redo and the remaining 6 patients were in sinus on-AAD. CONCLUSION: In this consecutive series of AF patients, early-recurrence in the 2nd or 3rd month following the PFA procedure was associated with high risk of late-recurrence. Thus, blanking period could be redefined as 1-month following PFA.

Structural Heart Imaging Using 3-Dimensional Intracardiac Echocardiography: JACC Cardiovascular Imaging Position Statement.

3-dimensional (3D) intracardiac echocardiography (ICE) is emerging as a promising complement and potential alternative to transesophageal echocardiography for imaging guidance in structural heart interventions. To establish standardized practices, our multidisciplinary expert position statement serves as a comprehensive guide for the appropriate indications and utilization of 3D-ICE in various structural heart procedures. The paper covers essential aspects such as the fundamentals of 3D-ICE imaging, basic views, and workflow recommendations specifically tailored for ICE-guided structural heart procedures, such as transeptal puncture, device closure of intracardiac structures, and transcatheter mitral and tricuspid valve interventions. Current challenges, future directions, and training requirements to ensure operator proficiency are also discussed, thereby promoting the safety and efficacy of this innovative imaging modality to support expanding its future clinical applications.

Asplenia-Associated Babesiosis: A Quagmire Traversed by Exchange Transfusion.

Babesiosis is a potentially life-threatening tick-borne parasitic infection. Severe disease in splenectomized individuals may require exchange transfusion. A 58-year-old male with a history of splenectomy presented with 2 weeks of subjective fever, weakness, and abdominal pain. He denied any rashes, tick bites, or recent travel. He had a motor vehicle accident a few years ago and had undergone an emergency splenectomy. On examination, the patient was febrile (39.3 °C), tachycardic (106/min), and jaundiced. Labs revealed anemia and thrombocytopenia. Computed tomography (CT) abdomen revealed asplenia. As it was summer, there was concern for a tick-borne illness. A peripheral smear showed schistocytes, and labs revealed hyperbilirubinemia, high lactate dehydrogenase (LDH), low haptoglobin, and reticulocytosis (13%), consistent with hemolysis. Testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Ehrlichia, Borrelia, Anaplasma, and viral hepatitis was negative. Antibody testing for Babesia microti was positive. A blood parasite smear confirmed Babesia microti with a parasitemia of 9.5%. The patient received intravenous azithromycin and atovaquone for severe babesiosis. On day 2 of hospitalization, parasitemia increased to 14.7%. Hemoglobin and platelets dropped further on day 3. His parasite load remained consistently above 10% despite medical treatment. A decision was made for a red blood cell (RBC) exchange transfusion for severe disease, which was performed on the fourth day of hospitalization. Clinical improvement was seen after one session of exchange RBC transfusion. Hemoglobin remained stable, and thrombocytopenia improved 1 day after RBC exchange transfusion. Parasitemia dropped to 1.2% after 4 days of exchange transfusion, and azithromycin was switched to oral. He received 9 days of inpatient azithromycin and atovaquone. He was discharged with a plan to continue the oral antimicrobials for 3 more weeks. Asplenia and parasitemia > 10% are associated with severe babesiosis. Asplenia, in particular, is associated with severe infection, hospitalization, and prolonged duration of therapy. Exchange transfusion in severe babesiosis can be lifesaving.

Myocardial Infarction and Complete Heart Block in a Patient With Anomalous Origin of the Left Coronary Artery From the Pulmonary Artery (ALCAPA).

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital malformation. We present a case of an elderly patient with ALCAPA presenting with complete heart block and non-ST-elevation myocardial infarction years after diagnosis and surgical correction. An 81-year-old female with a history of ALCAPA presented to the emergency department with chest pain and progressive mental deterioration. She was bradycardic and hypotensive. An electrocardiogram revealed a complete heart block. Troponin was 4.04 ng/mL. She received atropine and underwent transcutaneous pacing. Left heart catheterization revealed complete occlusion of the mid-left circumflex artery, which was intervened with balloon angioplasty and chronic total occlusion of the right coronary artery. She was supported with temporary transvenous pacing, did not require further pacing support, and was discharged home. Previous records unearthed that in 1988 she had presented with syncope and was diagnosed with ALCAPA, filling from right-to-left collaterals with large and ectatic coronaries. At the time, she underwent surgical correction with excision of the left coronary from the pulmonary artery and reimplantation in the left coronary cusp along the posterior aorta. She had remained asymptomatic after her surgery until this presentation. ALCAPA is extremely rare in adults. Insufficient collaterals to the left ventricle cause inadequate blood supply, leading to ischemia in adults, predisposing them to arrhythmias and risk of sudden death. Adults with ALCAPA remain at increased risk of adverse cardiac events later in life, requiring long-term monitoring.

A Patch Wearable Cardioverter-Defibrillator for Patients at Risk of Sudden Cardiac Arrest.

BACKGROUND: For many patients, sudden cardiac arrest (SCA) risk is elevated temporarily. Wearable cardioverter-defibrillators (WCDs) can monitor and treat SCA during these temporary periods. Traditional WCDs can be uncomfortable, require frequent maintenance, and cannot be used when showering, resulting in poor compliance and avoidable SCA deaths. The Jewel is a novel, water-resistant patch-wearable cardioverter-defibrillator (P-WCD) with a machine learning detection algorithm designed to improve compliance and protection against SCA. OBJECTIVES: This study aims to demonstrate the safety and clinical effectiveness of a novel P-WCD. METHODS: The Jewel IDE Study, a prospective, single-arm study conducted at 30 U.S. sites, enrolled patients at SCA risk due to ventricular tachycardia/ventricular fibrillation who were not candidates for or refused an implantable defibrillator. The primary safety endpoint was <15% patients with clinically significant cutaneous adverse device effects and the primary effectiveness endpoint was <2 inappropriate shocks/100 patient-months. Secondary endpoints were ≥1 successful ventricular tachycardia/ventricular fibrillation conversion and wear time compliance of >14.1 h/d. RESULTS: A total of 305 patients (mean age: 57.9 years; 30.2% female, 27.9% non-White) were enrolled, of which 290 had available device data. The clinically significant cutaneous adverse device effect rate was 2.30% (upper 1-sided 98% CI: 4.80); none were severe. No device-related deaths or serious adverse events were reported. The inappropriate shock rate was 0.36/100 patient-months (upper 1-sided 98% CI: 1.53). Of 11 shocks in 9 patients, 9 shocks were adjudicated to be appropriate. Eight of 9 shocks were successful with a single shock. Median wear time compliance was 23.5 (20.7-23.9) h/d. CONCLUSIONS: The novel P-WCD is a safe and effective WCD with high patient compliance. There were no deaths due to noncompliance and a high number of successful conversions (Jewel IDE study [A Clinical Evaluation of the Jewel P-WCD in Subjects at High Risk for Sudden Cardiac Arrest]; NCT05201495).

Outcomes With the WATCHMAN FLX in Everyday Clinical Practice From the NCDR Left Atrial Appendage Occlusion Registry.

BACKGROUND: PINNACLE FLX (Protection Against Embolism for Nonvalvular AF Patients: Investigational Device Evaluation of the WATCHMAN FLX LAA Closure Technology) demonstrated improved outcomes and low incidence of adverse events with the WATCHMAN FLX device in a controlled setting. The National Cardiovascular Disease Registry's Left Atrial Appendage Occlusion Registry was utilized to assess the safety and effectiveness of WATCHMAN FLX in contemporary clinical practice in the United States. METHODS: The WATCHMAN FLX Device Surveillance Post Approval Analysis Plan used data from the Left Atrial Appendage Occlusion registry to identify patients undergoing WATCHMAN FLX implantation between August 2020 and September 2022. The key safety end point was defined as all-cause death, ischemic stroke, systemic embolism, or device or procedure-related events requiring open cardiac surgery or major endovascular intervention between device implantation and hospital discharge. Major adverse events were reported at hospital discharge, 45 days, and 1 year. RESULTS: Among 97 185 patients in the Left Atrial Appendage Occlusion registry undergoing WATCHMAN FLX, successful implantation occurred in 97.5% (n=94 784) of patients. The key safety end point occurred in 0.45% of patients. At 45 days post-procedure, all-cause death occurred in 0.81% patients, ischemic stroke in 0.23%, major bleeding in 3.1%, pericardial effusion requiring intervention in 0.50%, device-related thrombus in 0.44%, and device embolism in 0.04% patients. No peri-device leak was observed in 83.1% of patients at 45 days. At 1 year, the rate of all-cause death was 8.2%, the rate of any stroke was 1.5% (ischemic stroke, 1.2%), and major bleeding occurred in 6.4% of patients. CONCLUSIONS: In a large contemporary cohort of patients with the WATCHMAN FLX device, the rates of implant success and clinical outcomes through 1 year were comparable with the PINNACLE FLX study, demonstrating that favorable outcomes achieved in the pivotal approval study can be replicated in routine clinical practice.

VARIPULSE: A step-by-step guide to pulmonary vein isolation.

INTRODUCTION: The VARIPULSE™ variable-loop circular catheter (VLCC) is a bidirectional, multielectrode catheter that can perform electrophysiological mapping and deliver pulsed field energy through the TRUPULSE™ Generator for the treatment of atrial fibrillation. This ablation system, including the CARTO 3™ three-dimensional electroanatomical mapping system, represents a fully integrated system. METHODS: Pulsed field ablation (PFA) is a novel, primarily cardiac tissue-selective ablation technology with a minimal thermal effect, potentially eliminating the collateral tissue damage associated with radiofrequency ablation or cryoablation. Integration of a mapping system may lead to shorter fluoroscopy times and improve the usability of the system, allowing tracking of energy density and placement to confirm no areas around the vein are left untreated. RESULTS: This step-by-step review covers patient selection, mapping, the step-by-step ablation workflow, details on catheter repositioning and ensuring contact, considerations for ablation of specific anatomical variations, and discussion of ablation without fluoroscopy based on our initial clinical experience. CONCLUSIONS: The VLCC is part of the fully integrated PFA system designed for pulmonary vein isolation, using mapping to guide catheter placement and lesion set creation. The current workflow, which is based on our initial clinical experience, may be further refined as the PFA system is used in real-world settings.

Myocarditis: A Rare Complication of Immune Checkpoint Inhibitor Therapy.

Immune checkpoint inhibitors (ICIs) are a class of immunotherapy agents that are often used in cancer treatment. A rare but life-threatening complication that can be seen is ICI-induced myocarditis. We discuss a case of pembrolizumab-induced myocarditis and the nuances involved in timely diagnosis and treatment. A 64-year-old female with a past medical history significant for metastatic right-sided colorectal adenocarcinoma undergoing immunotherapy with pembrolizumab presented with worsening shortness of breath and was found to be hypoxic. Initial laboratory analysis was remarkable for troponin of 0.35 ng/mL, which later peaked at 6.01 ng/mL. The electrocardiogram showed non-specific ST segment changes in the anteroseptal leads, and a subsequent echocardiogram revealed severely reduced left ventricular systolic function with an ejection fraction of 25%. Coronary angiography showed non-obstructive coronary arteries. As the patient was on pembrolizumab immunotherapy for cancer, there was high suspicion of ICI-induced myocarditis, and the patient was started empirically on steroids. Subsequently, cardiac magnetic resonance imaging was done, which confirmed the diagnosis of myocarditis. Pembrolizumab therapy was discontinued, and she was started on guideline-directed medical therapy for heart failure. While ICIs have transformed cancer therapy, healthcare providers must be vigilant for immune-related adverse events such as myocarditis. Early recognition, prompt management, and close monitoring are crucial for optimizing patient outcomes.

"Hot and Achy": A Case of an Extensive Spinal Epidural Abscess.

We present a case of a 94-year-old female who presented to the emergency room with a fever and generalized weakness without an initial obvious source of infection. Throughout admission, she continued to be febrile despite broad-spectrum antibiotics. Several days into admission, the patient complained of severe back pain, necessitating magnetic resonance imaging (MRI) of the entire spine. The imaging revealed an extensive epidural fluid collection consistent with a spinal epidural abscess. Fortunately, she did not have any neurological deficits and was treated conservatively with IV antibiotics with improvement. This case highlights this rare presentation and the importance of early diagnosis and management of spinal epidural abscesses.

Navigating a Complex Case of Mycobacterium Xenopi in a Patient with Blue Rubber Bleb Nevus Syndrome.

Introduction: Blue rubber bleb nevus syndrome is a rare disorder of venous malformations, with around 200 cases reported. We present a case of Mycobacterium xenopi infection in a patient with blue rubber bleb nevus syndrome. Case Description: A 40-year-old female with blue rubber bleb nevus syndrome, asthma, and bronchiectasis came to the pulmonology clinic with shortness of breath and a cough. She was recently admitted for a bronchiectasis exacerbation but continued to have a worsening productive cough and fevers. The most recent CT scan of the chest showed interval stable right upper lobe fibrocavitary disease, demonstrating gradual progression over two years. She had occasional positive cultures for Mycobacterium Avium Complex and M. xenopi one year previously, assumed to be a colonizer and not treated. Most recent hospital cultures were negative for bacteria and an acid-fast bacilli smear. She was sent to the emergency department for bronchiectasis exacerbation and returned to the clinic six weeks later with two sputum cultures growing M. xenopi. It was decided to treat M. xenopi as this was likely the cause of her cavitary lung lesion and frequent infections. Azithromycin, rifampin, and sulfamethoxazole/trimethoprim were initiated. Intravenous amikacin was added later on. She finally had a right partial lung resection done after one year at an outside hospital. She was on and off antibiotics for M. xenopi for approximately three years with negative repeat cultures for non-tuberculous mycobacteria. Conclusion: Due to the high mortality of M. xenopi infections (which can be as high as 69%), treatment of at least twelve months is recommended. To our knowledge, this is the first reported case of M. xenopi in a patient with blue rubber bleb nevus syndrome. LEARNING POINTS: The decision to initiate treatment for non-tuberculous mycobacterium infections is often challenging with prolonged treatment.Lifetime monitoring is required in patients with blue rubber bleb nevus syndrome, which can have pulmonary complications.M. xenopi has the highest mortality among non-tuberculous mycobacterium infections and requires at least 12 months of treatment.

Anomalous Bronchial Artery Origin - Canary in the Coal Mine - For Diagnosing Chronic Thromboembolic Pulmonary Hypertension.

Anomalous bronchial artery origins may have clinical implications beyond their anatomical curiosity. In this case, identification of such an anomaly led to the diagnosis of chronic thromboembolic pulmonary hypertension (CTEPH). A 49-year-old male with a history of recurrent deep vein thrombosis (DVT) and pulmonary embolism (PE) on anticoagulation presented with chest pain and shortness of breath. Laboratory analysis was remarkable for a troponin peak of 14.74 ng/ml, a brain natriuretic peptide level of 602 pg/ml and a D-dimer level of 0.62 µg/ml. Electrocardiogram showed non-specific ST elevation in the anterolateral and inferior leads. Computed tomography angiography (CTA) of the chest was positive for PE involving the right lower lobe pulmonary arterial tree. Echocardiogram showed reduced left ventricular function (ejection fraction 38%) and akinesis of the antero-apical and infero-apical segments. Cardiac catheterization revealed non-obstructive coronary arteries, and an anomalous origin of a right bronchial artery from the right coronary artery. The right bronchial hypertrophied as it supplied collateral flow to the occluded right pulmonary artery. This anomaly and the patient's history of multiple DVT/PEs while on therapeutic levels of warfarin with near normal D-dimer levels raised suspicion for a false positive PE. Pulmonary angiogram revealed chronic occlusion in branches of the right pulmonary artery, mean pulmonary artery pressure of 36 mmHg and no acute thrombus. Ventilation-perfusion scan confirmed the diagnosis of CTEPH. The patient underwent successful pulmonary thromboendarterectomy and subsequently had normalization of mean pulmonary artery pressure. This case underscores the importance of a comprehensive diagnostic approach, and consideration of alternative explanations for imaging findings, that unveiled the diagnosis of a complex and life-threatening condition such as CTEPH. LEARNING POINTS: This case underscores the diagnostic significance of identifying anomalous bronchial artery origin which played a crucial role in the diagnosis of the underlying chronic thromboembolic pulmonary hypertension (CTEPH).It is important to understand the limitations of computed tomography angiography (CTA) chest for diagnosis of CTEPH.

A Modular Communicative Leadless Pacing-Defibrillator System.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (ICD) is associated with fewer lead-related complications than a transvenous ICD; however, the subcutaneous ICD cannot provide bradycardia and antitachycardia pacing. Whether a modular pacing-defibrillator system comprising a leadless pacemaker in wireless communication with a subcutaneous ICD to provide antitachycardia and bradycardia pacing is safe remains unknown. METHODS: We conducted a multinational, single-group study that enrolled patients at risk for sudden death from ventricular arrhythmias and followed them for 6 months after implantation of a modular pacemaker-defibrillator system. The safety end point was freedom from leadless pacemaker-related major complications, evaluated against a performance goal of 86%. The two primary performance end points were successful communication between the pacemaker and the ICD (performance goal, 88%) and a pacing threshold of up to 2.0 V at a 0.4-msec pulse width (performance goal, 80%). RESULTS: We enrolled 293 patients, 162 of whom were in the 6-month end-point cohort and 151 of whom completed the 6-month follow-up period. The mean age of the patients was 60 years, 16.7% were women, and the mean (±SD) left ventricular ejection fraction was 33.1±12.6%. The percentage of patients who were free from leadless pacemaker-related major complications was 97.5%, which exceeded the prespecified performance goal. Wireless-device communication was successful in 98.8% of communication tests, which exceeded the prespecified goal. Of 151 patients, 147 (97.4%) had pacing thresholds of 2.0 V or less, which exceeded the prespecified goal. The percentage of episodes of arrhythmia that were successfully terminated by antitachycardia pacing was 61.3%, and there were no episodes for which antitachycardia pacing was not delivered owing to communication failure. Of 162 patients, 8 died (4.9%); none of the deaths were deemed to be related to arrhythmias or the implantation procedure. CONCLUSIONS: The leadless pacemaker in wireless communication with a subcutaneous ICD exceeded performance goals for freedom from major complications related to the leadless pacemaker, for communication between the leadless pacemaker and subcutaneous ICD, and for the percentage of patients with a pacing threshold up to 2.0 V at a 0.4-msec pulse width at 6 months. (Funded by Boston Scientific; MODULAR ATP ClinicalTrials.gov NCT04798768.).

Dual-energy lattice-tip ablation system for persistent atrial fibrillation: a randomized trial.

Clinical outcomes of catheter ablation for atrial fibrillation (AF) are suboptimal due, in part, to challenges in achieving durable lesions. Although focal point-by-point ablation allows for the creation of any required lesion set, this strategy necessitates the generation of contiguous lesions without gaps. A large-tip catheter, capable of creating wide-footprint ablation lesions, may increase ablation effectiveness and efficiency. In a randomized, single-blind, non-inferiority trial, 420 patients with persistent AF underwent ablation using a large-tip catheter with dual pulsed field and radiofrequency energies versus ablation using a conventional radiofrequency ablation system. The primary composite effectiveness endpoint was evaluated through 1 year and included freedom from acute procedural failure and repeat ablation at any time, plus arrhythmia recurrence, drug initiation or escalation or cardioversion after a 3-month blanking period. The primary safety endpoint was freedom from a composite of serious procedure-related or device-related adverse events. The primary effectiveness endpoint was observed for 73.8% and 65.8% of patients in the investigational and control arms, respectively (P < 0.0001 for non-inferiority). Major procedural or device-related complications occurred in three patients in the investigational arm and in two patients in the control arm (P < 0.0001 for non-inferiority). In a secondary analysis, procedural times were shorter in the investigational arm as compared to the control arm (P < 0.0001). These results demonstrate non-inferior safety and effectiveness of the dual-energy catheter for the treatment of persistent AF. Future large-scale studies are needed to gather real-world evidence on the impact of the focal dual-energy lattice catheter on the broader population of patients with AF. ClinicalTrials.gov identifier: NCT05120193 .

Result of the left bundle branch area pacing data collection registry, an international multicenter study of conduction system pacing with a Tendril STS 2088 stylet-driven lead.

INTRODUCTION: Left bundle branch area (LBBA) pacing (LBBAP) has been proposed as an alternative therapy option in patients indicated for cardiac pacing to treat bradycardia or heart failure. The aim of the study was to evaluate the safety and effectiveness of LBBAP in patients implanted with a Tendril 2088 stylet-driven lead. METHODS: The international retrospective data collection registry included 11 sites from 5 countries globally. Patients with attempted implants of the Tendril lead in the LBBA were followed for at least 6 months post the implant attempt. The primary safety and efficacy endpoints were freedom from LBBAP lead-related serious adverse events and the composite of LBBA capture threshold of ≤2.0 V and R-wave amplitudes ≥5 mV (or ≥value at implant), respectively. RESULTS: Of 221 patients with attempted implants of the Tendril 2088 lead in the LBBA, 91.4% (202/221) had successful implants for LBBAP. Regardless of the LBBAP implant success, all patients were followed for at least 6 months (8.7 ± 7.3 months). Baseline characteristics: 44% female, 84% ≥65 years old, 34% coronary artery disease, and 86% of primary indications for pacemaker implant. Both primary safety and effectiveness endpoints were met (freedom from LBBAP lead-related serious adverse device effects of 99.5% and electrical performance composite success rate of 93%). The capture thresholds in LBBAP at implant and 6 months were 0.8 ± 0.3 V@0.4 ± 0.1 ms and 0.8 ± 0.3 V@0.4 ± 0.1 ms. The rate of patients with capture threshold rise ≥1 V was 1.5% through 6 months. The R-wave amplitudes in LBBAP at implant and 6 months were 9.3 ± 3.2 mV and 10.6 ± 3.0 mV. CONCLUSIONS: This large multicenter study demonstrates that the stylet-driven Tendril™ STS 2088 lead is safe and effective for LBBAP with high success and low complication rates.

Micra Extraction Out To 4.5 Years.

Leadless pacemaker systems (LPs) were developed as an alternative to traditional transvenous permanent pacemakers (TV-PPM) due to increasing rates of device and procedural related complications, leading to a high-cost burden to our health-care system. LPs were initially indicated for single-chamber ventricular pacing; however, recent developments have allowed for dual-chamber pacing too. These systems have demonstrated highly successful implant rates with stable pacing performance. This article describes the retrieval techniques of the Micra LPs and ways to mitigate challenges encountered during the retrieval process.

A Case of Omeprazole-Associated Acute Interstitial Nephritis.

Acute interstitial nephritis (AIN) is characterized by an inflammatory infiltrate of the interstitium of the kidney, typically causing a decline in kidney function. Drug-induced AIN (also called allergic AIN) is a type of AIN. Common drugs associated with AIN are antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), and proton pump inhibitors (PPIs). A 59-year-old male with a history of recent laparoscopic robotic sleeve gastrectomy presented to the emergency department with five weeks of progressively worsening fatigue, nausea, and lightheadedness. Postoperatively, he was prescribed omeprazole 20 mg daily for gastric ulcer prophylaxis. His other home medications were amlodipine, atorvastatin, ursodiol, and budesonide-formoterol fumarate nebulizer. His physical examination was normal. Laboratory studies revealed elevated creatinine of 4.19 mg/dL from a baseline of 0.9 mg/dL two months ago and the presence of urine eosinophils. The etiology of this elevated creatinine was unclear, prompting CT-guided left renal biopsy. The biopsy showed diffuse interstitial inflammatory infiltration with numerous lymphocytes, a large number of neutrophils, and scattered eosinophils, consistent with the allergic type of AIN. Omeprazole was discontinued and the patient received a seven-day course of prednisone. Despite treatment, permanent renal damage occurred, and the patient's new baseline creatinine was 2.3 mg/dL. AIN caused by PPIs should be considered in the differential diagnosis of acute kidney injury (AKI). AIN can be difficult to diagnose, presenting with nonspecific symptoms, such as oliguria, malaise, nausea, and vomiting. An accurate and timely diagnosis can help prevent and treat worsening renal failure.