Graphical abstract
Keywords: Fossa ovalis, Interatrial septum, Hematoma, Transseptal puncture, Canine
Highlights:
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TASP is required for transcatheter LAD in dogs.
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Septal puncture can result in interatrial septal dissection and hematoma formation.
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PEff and cardiac tamponade can be a fatal complication after puncture.
Introduction
Myxomatous mitral valve disease (MMVD) is the most prevalent cardiac disease in canine patients, regularly progressing to symptomatic heart failure (HF).1, 2, 3 Traditionally, these patients have been managed pharmacologically. Nevertheless, progression of valvular disease for most patients will lead to death from HF or refractoriness to medical therapy within 2 years.4,5 Consequently, interventional and surgical techniques for management of MMVD are being developed and are increasingly more common.6, 7, 8, 9 One such technique is transcatheter left atrial decompression (LAD), which is a palliative procedure that has been shown to lower left atrial pressure with potential to improve control of HF symptoms.7
Transatrial septal puncture (TASP) is required for the LAD procedure. Inadvertent atrial wall perforation with pericardial effusion (PEff) and subsequent tamponade are a risk following TASP.7,10 The complicated septal anatomy often present in these patients due to severe left atrial enlargement and rightward septal bowing increases the difficulty of this procedure.10
A review of human literature identified 19 patients from 882 studies with interatrial septal dissection and/or hematoma formation following TASP.11 Many patients were managed conservatively, while 2 patients (2/19; 11%) required further intervention (pericardiocentesis or surgical drainage) to ameliorate hemodynamic instability.
This case report identifies interatrial septal hematoma formation and subsequent PEff following TASP in a dog. Although both hematoma formation and PEff were self-limiting, it is imperative that interventional cardiologists be cognizant of the potentially fatal complications of this procedure so that management can be adjusted accordingly.
Case Presentation
A 14-year-old female-spayed terrier mix with a history of chronic MMVD and symptomatic HF was presented to the cardiology service of a private veterinary specialty hospital for planned LAD. On presentation to the hospital, the dog was tachycardic (176 bpm; reference range, 60-160 bpm) with a grade V/VI left apical holosystolic heart murmur. On the day of the procedure, the patient weighed 4.75 kg and was receiving torsemide (1.25 mg [0.26 mg/kg] by mouth 3 times a day), spironolactone (12.5 mg [2.63 mg/kg] by mouth once a day), pimobendan (1.25 mg [0.26 mg/kg] by mouth 3 times a day), and amlodipine (0.625 mg [0.13 mg/kg] by mouth twice a day). Azotemia and hypokalemia were noted on serum chemistry profile (blood urea nitrogen 65 mg/dL, reference interval 7-27 mg/dL; creatinine 2.6 mg/dL, reference interval 0.5-1.8 mg/dL; potassium 3.2 mmol/L, reference interval 3.5-5.8 mmol/L). A preoperative transthoracic echocardiogram (TTE) performed by a board-certified veterinary cardiologist identified severe left atrial and ventricular dilation, mitral valve thickening, and subsequent severe mitral regurgitation (Figures 1 and 2, Videos 1 and 2). Transmitral inflow Doppler showed a restrictive filling pattern (E wave velocity = 2.15 m/s, A wave velocity = 1.48 m/s, E/A ratio = 1.46), consistent with high left ventricular filling pressure due to high left atrial pressure. Routine measurements were obtained using standard techniques.12
Figure 1.
Two-dimensional TTE, right parasternal 4-chamber long-axis diastolic view, demonstrates severe left ventricular dilation, mitral valve thickening, and severe left atrial dilation. LA, Left atrium; LV, left ventricle.
Figure 2.
Two-dimensional TTE, right parasternal 4-chamber long-axis midsystolic view with color-flow Doppler, demonstrates severe mitral regurgitation. LA, Left atrium; LV, left ventricle; MR, mitral regurgitation.
The dog was subsequently anesthetized using total-intravenous anesthesia and placed in left lateral recumbency. Transesophageal echocardiography (TEE) with three-dimensional capability was performed throughout the procedure by a board-certified veterinary cardiologist. The LAD was performed via a previously described transvenous approach using a 5 Fr introducer in the right jugular vein for vascular access.7,10 Nonheparinized saline was used to flush catheters and introducers throughout the procedure. A 4 F hydrophilic-coated angiographic catheter and 0.035-inch hydrophilic guidewire were advanced under fluoroscopic guidance through the right heart and into the pulmonary artery, and a right heart pressure study was obtained. The hydrophilic-coated angiographic catheter was removed, and the 5Fr vascular introducer was exchanged for a 7 Fr hydrophilic-coated hemostatic guiding sheath introducer over a 0.035-inch polytetrafluoroethylene guidewire. Hemorrhage was noted around the introducer, and a vascular cutdown was performed to ligate the vein proximally and achieve vascular control and subsequent hemostasis with 2-0 silk distally. Prior to TASP, TEE demonstrated a normal extracardiac fibrofatty space between the atria with rightward deviation of the interatrial septum (IAS; Figure 3, Video 3). A pediatric Brockenbraugh transseptal needle was introduced through the introducer, and an attempt at needle puncture of the septum was performed as previously described.10 During initial TASP, the needle orientation was abnormally parallel to the IAS on TEE and was noted to be within the interatrial space (Figure 4, Video 4). The needle was then repositioned and successfully passed into the left atrium. Subsequent hematoma formation in the IAS (noted as an increased echodensity and thickening of the interatrial space on biplane TEE) and PEff (anechoic space between the epicardium and pericardium) were noted (Figures 5 and 6, Videos 5 and 6). The procedure was temporarily suspended to monitor for continued fluid extravasation into the pericardial space and cardiac tamponade. Given the lack of continued fluid accumulation and stable arterial blood pressure, the procedure was successfully completed as described elsewhere.7,10 The dog recovered uneventfully from anesthesia, and postoperative imaging confirmed the persistence but lack of progression of the interatrial septal hematoma and PEff (Figure 7, Video 7). Left-to-right shunting across the atrial septostomy site was appropriate, the size of the defect measured approximately 5 mm, and the flow was not impeded by the septal hematoma. At the dog's 6-month recheck, there was a persistent left-to-right flow through the atrial septostomy site and the septal hematoma had completely resolved without residual PEff; the atrial septostomy site measured similar in diameter with appropriate left-to-right flow (Figure 8, Video 8). The dog was euthanized at 8 months post-LAD for owner-assessed poor quality of life. No postmortem examination was performed.
Figure 3.
Two-dimensional biplane TEE, modified 4-chamber long-axis view (A) and modified bicaval view (B), demonstrates a normal interatrial septal space with a curvilinear septum situated between the large LA and normal right atrium. Three-dimensional TEE, modified en face view of the IAS (C), demonstrates the patient's interatrial septal anatomy viewed from the LA prior to TASP. Electrocardiogram showed a single blocked P wave followed by an interpolated ventricular premature complex. LA, Left atrium; MV, mitral valve.
Figure 4.
Two-dimensional biplane TEE, modified 4-chamber long-axis view (A) and modified bicaval view (B), demonstrates the needle within the interatrial space (arrow). Three-dimensional TEE, modified en face view of the IAS (C), demonstrates focal longitudinal thickening (arrowheads) of the IAS consistent with interatrial septal needle placement. Sinus rhythm is present on electrocardiogram. LA, Left atrium; MV, mitral valve.
Figure 5.
Two-dimensional TEE, 2-chamber long-axis view (A) and modified bicaval view (B), demonstrates an increased echogenicity (arrowheads) within the interatrial space consistent with interatrial hematoma development. Three-dimensional TEE, modified en face view of the IAS (C), demonstrates broad and irregular thickening (arrowheads) of the IAS.
Figure 6.
Two-dimensional TEE, 2-chamber long-axis view, demonstrates small volume PEff (arrows). LA, Left atrium; LV, left ventricle; MV, mitral valve.
Figure 7.
Two-dimensional TTE, left apical 4-chamber view, demonstrates echogenic interatrial septal thickening (arrowheads) and PEff. LA, Left atrium; LV, left ventricle.
Figure 8.
Six-month postoperative two-dimensional TTE, right parasternal short-axis heart base view, demonstrates complete resolution of the previously noted hematoma within the IAS (arrows). Ao, Aorta; LA, left atrium.
Discussion
Transatrial septal puncture is aimed at puncturing the septum at the level of the fossa ovalis.7 The fossa ovalis is contained within the true IAS where septal tissue is the thinnest.13 In adulthood, it is covered by the valve of the fossa ovalis, which prevents direct communication between the atria due to left and right atrial pressure differences.13 When TASP is performed elsewhere on the IAS, the needle can pass into the extracardiac space, potentially resulting in IAS dissection, hematoma formation, and PEff.11 The fossa ovalis is bordered by the caudal vena cava caudally, the coronary sinus caudoventrally, the septal leaflet of the tricuspid valve ventrally, the intervenous tubercule cranially, and the roof of the right atrium dorsally.13 Left atrial decompression is pursued in canine patients with increased left atrial pressure, making it fair to assume that these patients will have rightward septal bowing, complicating the septal anatomy and approach to TASP from the cranial vena cava.7,10 It is imperative that interventional cardiologists have a sound knowledge of septal anatomy so procedural techniques can be adjusted accordingly. Transesophageal echocardiography at the time of TASP in this case revealed the needle coursing caudodorsally and parallel to the IAS and through the septum secundum into the extracardiac space between the 2 atria. A septal hematoma was then identified as an acute increase in echogenicity and thickness, identified on TEE, in this interatrial space. A contrast injection in this space was not performed, so it cannot be concluded that the needle was truly within the interatrial septal space, but the subsequent development of PEff and hematoma development within this space strengthens this argument.
As the pressure within the left atrium increases with the progression of valvular disease, the left atrial wall thins and endocardial splitting is a common finding at postmortem examination in dogs.7 Inappropriate needle orientation or attempted puncture distant from the fossa ovalis may lead to septal hematoma formation if this thin tissue is inadvertently punctured.11 Additionally, larger sheaths and recrossing the IAS can also predispose a patient to interatrial septal hematoma formation.11 Ideally, a single controlled puncture of the IAS with minimal septal tenting is performed at the midfossa ovalis.11 For this case, it is likely that a combination of factors listed above led to septal hematoma formation.
As no preoperative coagulation testing was performed, coagulopathy cannot be excluded as a cause for potentiation of the PEff. Pericatheter hemorrhage prior to TASP was thought to be secondary to inappropriate catheter sizing, as opposed to coagulopathy, and given the lack of continued effusion development following TASP, it is unlikely that a coagulopathy contributed to this dog's pathology.
Although not identified in this dog, aortic root puncture must be considered when acute PEff development is noted post-TASP.14 Arterial pressure monitoring, serial PEff monitoring via TEE, and fistula identification via color-Doppler can assist in diagnosis/exclusion of aortic root puncture.14
It is also plausible that interatrial septal hematoma formation may affect cardiac electrical conduction pathways given the proximity to the atrioventricular node and its tributaries. No such arrhythmias were identified in this case. However, an argument can be made for acute arrhythmia formation (e.g., pressure ischemia of the conduction system from the hematoma) and chronic arrhythmia formation (e.g., secondary fibrosis development following resolution of the hematoma) to be concerns following TASP.
The study performed by Allen et al.7 introducing the LAD technique, its success, and noted complications identified 3 out of 18 procedures that developed PEff, each of them being self-limiting. Only 1 of the 3 developed PEff in association with TASP; the other 2 were the result of guidewire puncture of the caudal vena cava and puncture of the caudal aspect of the left atrium following forceful puncture of the septum. It should be noted that PEff did not develop in some cases where IAS puncture did not occur at the fossa ovalis. The absence of periprocedural and intraoperative mortality found by this study identifies LAD as a safe, although palliative, procedure to be performed in dogs with MMVD and advanced HF. However, despite this low complication rate, it is important to recognize that complications can necessitate acute changes in management strategies, and the interventionalist and their team need to be prepared as such.
Deciding to administer anticoagulant agents following TASP with PEff development is case dependent. Anticoagulation (with heparin) at the time of IAS puncture is generally performed to reduce risk of thrombus formation and closure of the newly created defect.7 However, long-term benefits versus risk of anticoagulation are yet to be established in dogs. The risks of forgoing anticoagulation in dogs are unknown, although in humans, reversal of anticoagulation and aborting of the procedure is recommended if rapid PEff were to develop.11,15 In this case, anticoagulation was not performed due to complications encountered during TASP and long-term patency of the defect was still maintained postoperatively. Recommendations regarding the decision for anticoagulation in canine LAD, especially in the face of procedural complications, are still lacking.
This case report has several limitations. As this is a case report, distinctions cannot be made about when intervention (such as pericardiocentesis) is indicated during the procedure should PEff develop as a result of TASP. Similarly, we cannot conclude that it is safe to proceed with anticoagulation following TASP when interatrial dissection, hematoma formation, and/or PEff develop. The decision to intervene still needs to be made on a case-by-case basis.
Conclusion
Transatrial septal needle puncture may lead to interatrial septal dissection, hematoma formation, and PEff, necessitating serial intraoperative and postoperative echocardiographic evaluation to guide management and intervention to avoid cardiac tamponade and death. It is vital that interventionalists and intraoperative imagers be able to recognize these complications via TEE so that management can be adjusted accordingly. In the present case, TEE and hemodynamic monitoring allowed the LAD to be performed successfully, despite interatrial septal hematoma formation and PEff formation without further complication.
Ethics Statement
The authors declare that the work described has been carried out in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki) for experiments involving humans.
Consent Statement
The authors declare that since this was a non-interventional, retrospective, observational study utilizing de-identified data, informed consent was not required from the patient under an IRB exemption status.
Funding
The authors declare that this report did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Disclosure Statement
The authors reported no actual or potential conflicts of interest relative to this document.
Acknowledgments
We thank Nadine Valenciano, Vanessa Diaz, and Ivan Alcala, who helped manage the anesthetic and postoperative care for these patients.
Footnotes
Supplementary data related to this article can be found at https://doi.org/10.1016/j.case.2026.01.001.
Supplementary Data
Two-dimensional TTE, right parasternal 4-chamber long-axis view, demonstrates left-sided cardiac chamber dilation.
Two-dimensional TTE, left apical 4-chamber view, demonstrates severe mitral regurgitation.
Two- and three-dimensional TEE, (A) modified 4-chamber long-axis view, (B) modified bicaval view, and (C) modified en face view, demonstrates the patient's septal anatomy prior to TASP. Electrocardiogram showed a single blocked P wave followed by an interpolated ventricular premature complex. The white arrows point toward the IAS.
Two-dimensional biplane TEE, modified 4-chamber long-axis view (A) and modified bicaval view (B), demonstrates the needle within the interatrial space (white arrows). Three-dimensional TEE, modified en face view of the IAS (C), demonstrates focal longitudinal thickening of the IAS consistent with interatrial septal needle placement (white arrows). Electrocardiogram showed sinus rhythm.
Two-dimensional biplane TEE, (A) 2-chamber long-axis view (A) and bicaval view (B) and 3D TEE, en face view (C), demonstrates an increased echogenicity within the interatrial space and thickening of the interatrial wall post-TASP (white arrows).
Two-dimensional TEE, 2-chamber long axis view, demonstrates small volume PEff (white arrow).
Two-dimensional TTE, left apical 4-chamber view, demonstrates the echogenic interatrial septal thickening (white arrow).
Two-dimensional TTE, right parasternal transverse view at the level of the heart base, demonstrates the complete resolution of the previously noted interatrial septal hematoma at 6 months postoperatively (white arrow). Electrocardiogram showed sinus rhythm.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Two-dimensional TTE, right parasternal 4-chamber long-axis view, demonstrates left-sided cardiac chamber dilation.
Two-dimensional TTE, left apical 4-chamber view, demonstrates severe mitral regurgitation.
Two- and three-dimensional TEE, (A) modified 4-chamber long-axis view, (B) modified bicaval view, and (C) modified en face view, demonstrates the patient's septal anatomy prior to TASP. Electrocardiogram showed a single blocked P wave followed by an interpolated ventricular premature complex. The white arrows point toward the IAS.
Two-dimensional biplane TEE, modified 4-chamber long-axis view (A) and modified bicaval view (B), demonstrates the needle within the interatrial space (white arrows). Three-dimensional TEE, modified en face view of the IAS (C), demonstrates focal longitudinal thickening of the IAS consistent with interatrial septal needle placement (white arrows). Electrocardiogram showed sinus rhythm.
Two-dimensional biplane TEE, (A) 2-chamber long-axis view (A) and bicaval view (B) and 3D TEE, en face view (C), demonstrates an increased echogenicity within the interatrial space and thickening of the interatrial wall post-TASP (white arrows).
Two-dimensional TEE, 2-chamber long axis view, demonstrates small volume PEff (white arrow).
Two-dimensional TTE, left apical 4-chamber view, demonstrates the echogenic interatrial septal thickening (white arrow).
Two-dimensional TTE, right parasternal transverse view at the level of the heart base, demonstrates the complete resolution of the previously noted interatrial septal hematoma at 6 months postoperatively (white arrow). Electrocardiogram showed sinus rhythm.