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Cathether-based interventional strategies for cor triatriatum in the adult – feasibility study through a hybrid approach
© Li et al. 2015
Received: 26 January 2015
Accepted: 7 July 2015
Published: 14 July 2015
Cor triatriatum is a rare congenital cardiac abnormality, consisting of an obstructing membrane between the pulmonary veins and the mitral valve in varying patterns. The entitiy can mimick the pathophysiology of mitral stenosis, necessitating surgical resection. Occasionally, percutaneous balloon dilatation of the membrane has been successfully performed.
We report two cases with cor triatriatum where intraoperative balloon dilatation of the membrane was attempted followed by surgical resection, to explore the feasibility of cathether-based interventional strategies for cor triatriatum.
Various anatomical variations exist of cor triatriatum, depending on the drainage of the pulmonary veins and the drainage of the proximal chamber in the right or left atrium. Only isolated forms of cor triatriatum where all pulmonary veins ultimately drain into the left atrium can be recommended for percutaneous strategies. In addition, several anatomical characteristics should be considered to predict technical success of cathether-based interventional strategies, such as the location of the membrane, the degree of pulmonary vein stenosis, the extent of calcification, and the presence of other (congenital) cardiovascular abnormalities. Furthermore, long-term efficacy of these strategies remains to be confirmed. As such, surgical treatment of cor triatriatum remains the mainstay of treatment in adult patients, especially when other cardiovascular anomalies are present which require surgical correction.
Modified classification of cor triatriatum according to Lucas 
Accessory atrial chamber receives all pulmonary veins and communicates with left atrium
A. No other connections (classic cor triatriatum)
B. Other anomalous connections
1. To right atrium directly
2. With totally anomalous pulmonary venous connection
Accessory atrial chamber receives all pulmonary veins and does not communicate with the left atrium
A. Anomalous connection to right atrium directly (cardiac TAPVC with all pulmonary veins first draining to a venous confluence)
B. With totally anomalous pulmonary venous connection (supracardiac or infracardiac TAPVC)
Subtotal cor triatriatum
A. Accessory atrial chamber receives part of the pulmonary veins and connects to the left atrium
1. Remaining pulmonary veins connect normally
2. Remaining pulmonary veins connect anomalously (partial cor triatriatum with PAPVC)
B. Accessory atrial chamber receives part of the pulmonary veins and connects to the right atrium
1. Remaining pulmonary veins connect normally (PAPVC with anomalously connected pulmonary veins first draining to a venous confluence)
2. Remaining pulmonary veins connect anomalously (mixed TAPVC)
Overview of published reports on percutaneous interventions in cor triatriatum
Cor triatriatum classification
Outcome and remarks
Am Heart J 1996
Double-balloon dilatation (2× 18 mm diameter & 3 cm-long balloon angioplasty catheter sequentially placed)
Reduction of transmembrane gradient from 34 to 4 mmHg, and pulmonary artery pressure from 92/48 to 36/16 mmHg
Catheter Cardiovasc Interv 2002
Inoue balloon dilatation
Reduction of transmembrane gradient from 26 to 4 mmHg
Pediatr Cardiol 2008
Balloon dilatation (16 mm × 4 cm Tyshak II balloon)
Reduction of pressure in proximal chamber from 32 to 12 mmHg
Pediatr Cardiol 2012
Balloon dilatation (13 mm)
Admitted to emergency department with cardiogenic shock due to obstructing cor triatriatum and PAPVC. Planned staged treatment with percutaneous intervention as palliative measure before definitive surgical therapy.
Reduction of transmembrane gradient from 20 to 1 mmHg
European Journal of Heart Failure 2013
Inoue balloon dilatation (30 mm)
Reduction of transmembrane gradient from 20 to 1 mmHg, and increase of orifice diameter from 1.2 to 2 cm
Catheter Cardiovasc Interv 2013
Placement of 7 × 16 mm stent
Complex congenital heart defect with HLHS, TAPVC, cor triatriatum. Percutaneous intervention as part of staged treatment.
Reduction of pulmonary venous confluence pressure from 21 to 7 mmHg
In this paper, we present two cases as a feasibility study evaluating the effects of intraoperative balloon dilatation in two adult patients undergoing surgical treatment of cor triatriatum. Based on these experiences and previously reported cases, recommendations are made to guide patient selection for percutaneous treatment of cor triatriatum.
Postoperative course was uneventful, and the patient was discharged on postoperative day 7. At 4 months follow-up, the patient was asymptomatic. Echocardiography showed no residual membrane and no signs of pulmonary venous stenosis.
A 58-year-old woman with a history of paroxysmal atrial fibrillation was referred to our center with cor triatriatum. Transthoracic and transesophageal echocardiography demonstrated normal left and right ventricular size and function, and an enlarged left atrium. A thin membrane was noticed in the left atrium dividing it into 2 compartments, with a mean gradient of 4 mmHg over the membrane, which increased to 7 mmHg during exercise. Pulmonary hypertension was noticed (36 mmHg), which increased after exercise (56 mmHg). Cardiac MRI confirmed these findings, demonstrating a proximal chamber receiving all PVs and communicating with the left atrium (type IA ). Left and right cardiac catheterization showed normal coronary arteries without significant stenoses, and a significant mean gradient between simultaneously measured right pulmonary capillary wedge and left ventricular end diastolic pressure of 6 mmHg, which increased to 20 mmHg after dopamine-infusion.
Postoperative course was uneventful, and the patient was discharged on postoperative day 10. At 6 months follow-up, the patient was asymptomatic, with less dyspnea on exertion when compared to before the operation. On echocardiography, no residual membrane was found.
In these two cases assessing the efficacy of cathether-based interventional strategies for cor triatriatum in the adult, several cautionary lessons can be learned regarding patient selection. While the concept of percutaneous therapy for this congenital abnormality is sound and technically certainly feasible, several anatomical considerations should be taken into account. Various variations exist of cor triatriatum, depending on the drainage of the PVs and the drainage of the proximal chamber in the right or left atrium  (Table 1). Only isolated forms of cor triatriatum where all PVs ultimately drain into the left atrium can be recommended for percutaneous strategies. As such, only type IA (classic cor triatriatum where an accessory atrial chamber receives all PVs and connects with the left atrium) and type IIIA1 (subtotal cor triatriatum with an accessory atrial chamber receiving part of the PVs and communicates with the left atrium, with the remaining PVs connecting normally) are amendable for percutaneous intervention. In addition, approximately 75 % of patients in large surgical series undergoing operative treatment also underwent additional surgical procedures [4, 5, 14]. When cor triatriatum is associated with other cardiac abnormalities requiring surgical intervention, operative therapy naturally remains the treatment of choice. Therefore, detailed imaging studies are essential in guiding patient selection for percutaneous therapy, to clarify the exact anatomy of the anomaly and to detect associated cardiac abnormalities. In this regard, transthoracic and transesophageal echocardiography are usually the initial choice of imaging modality. Additionally, cardiac MRI can even more clearly depict the precise morphology of cor triatriatum, demonstrating the relationship between the fibromuscular membrane and the PVs, determining the hemodynamic significance of the obstruction, and detecting associated cardiac abnormalities .
In patients with isolated type IA or type IIIA1 cor triatriatum, we speculate that several anatomical characteristics should be evaluated to predict the chance of a successful percutaneous intervention. The exact anatomy of the PVs draining in the proximal chamber should be assessed, with emphasis on the presence of PV obstruction or stenosis, especially at the level of the draining orifice. As illustrated in case 1, the complex anatomy of an obstructing membrane just before an already stenotic draining orifice of the PV, affects the technical success of a balloon dilatation greatly. Although treatment of PV stenosis with angioplasty and stenting has been reported, long-term outcomes are poor with a high degree of restenosis [16, 17]. As such, we do not recommend an attempt at percutaneous intervention for patients with cor triatiatum with concomitant PV stenosis. In these cases, a surgical resection of the obstructive membrane should be performed with surgical enlargement of the PV orifice.
Besides the presence of PV stenosis, we hypothesize that calcification of the obstructing membrane is an additional important aspect to consider. With the increasing diagnostic accuracy of echocardiography, cor triatriatum might be diagnosed more frequently and at an older age , when calcification of the obstructing membrane will be more prevalent. As illustrated in case 2 where the inferior border of the membrane was significantly calcified, balloon dilatation led only to a small tear next to the calcified part of the membrane with limited increase of orifice area. In the setting of PMC for mitral stenosis, valve calcification has been associated with poor immediate and long-term results  and is a relative contraindication for PMC [6, 7]. Whether membrane calcification is also associated with procedural success in the percutaneous treatment of cor triatriatum remains to be clarified.
Our initial concern regarding extracardiac rupture, one of the main reasons to initiate this feasibility study through a hybrid approach, seems unfounded based on the intraoperative estimation of tissue tear after balloon dilatation. Correspondingly, cardiac rupture after PMC is a rare complication, and is usually puncture-related rather than a direct consequence of balloon dilatation .
Even in cases of cor triatriatum with favourable anatomical characteristics where percutaneous interventional is feasible, the long-term patency remains unclear, with 15 months as the longest reported follow-up period (Table 2). In addition, we assume a publication bias towards reporting successful cases is present. Moreover, surgical repair of cor triatriatum, consisting of total resection of the membrane, is usually a simple and straightforward procedure. Although the use of extracorporeal circulation and cardioplegic arrest of the heart is needed, it can be performed with minimal mortality and morbidity. In the largest surgical series available  with 66 patients, no mortality was noted in cases operated after 1970, and no surgical reintervention was needed after a median follow-up of 5.4 years. These results should serve as a benchmark for comparison for any other intervention.
Then what is the role of cathether-based interventional strategies for cor triatriatum? In selected patients who are acutely presented with heart failure and are at that time unfit for surgery, percutaneous interventions could be important as a bridge to definite operative therapy , or even as definitive treatment , both in pediatric  and adult cases . Additionally, when cor triatriatum is diagnosed during pregnancy, a percutaneous strategy might be useful when the anatomical variant is compatible, as cardiac surgery and cardiopulmonary bypass increase maternal and fetal risks. In elective cases of isolated cor triatriatum with favorable anatomical characteristics, the option of a percutaneous intervention can be discussed with the patient as an experimental alternative, or in the setting of a comparative study. These cases should be centralized in high-volume percutaneous intervention centers, preferably with extensive experience in PMC, and should be reported in an international registry for research and educational purposes.
In conclusion, the concept of percutaneous cathether-based interventional treatment strategies for cor triatriatum in the adult is sound and should be technically feasible. However, several anatomical characteristics should be considered to predict technical success, such as the location of the membrane, the degree of PV stenosis, the extent of calcification, and the presence of other (congenital) cardiovascular abnormalities. Furthermore, long-term efficacy of this therapy remains to be confirmed. As such, surgical treatment of cor triatriatum remains the mainstay of treatment in adult patients, especially when other cardiovascular anomalies are present which require surgical correction.
Written informed consent was obtained from both patients for publication of this Case report and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.
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