Pitfalls in Left Atrial Reduction. Superior Neo-Cava with Pericardium

INTRODUCTION

Left atrial reduction has been proposed by Sankar¹ as an alternative for eliminating chronic atrial fibrillation (AF) associated with mitral valve disease. We have performed this procedure in 17 patients during mitral valve surgery; nevertheless, this surgery involves risks, such as the inadvertent rotation of the left atrium (LA) when it is anastomosed. The displacement of the heart to the right, including the proximal portion of the superior vena cava (SVC), makes correct anastomosis impossible. In such cases, alternative surgical techniques must be used in order to avoid a superior vena cava syndrome.

CLINICAL CASE

A 47-year-old woman was diagnosed with a double mitral valve lesion and chronic AF, and was categorized as New York Heart Association (NYHA) functional capacity III. She underwent surgery in February of 2001. A Carbomedics Inc. 29 mm mechanical mitral valve prosthesis (Austin, Tex., USA) was implanted. A left atrial reduction was performed to eliminate the chronic AF.² The SVC could not be anastomosed directly due to inadvertent displacement of the heart to the right. A superior neocava was constructed at the base of the patient´s pericardium, using a Hegar dilator as a mold (Figure 1). The superior and inferior ends of the pericardium were anastomosed to the ends of sectioned SVC, re-establishing normal cardiopulmonary flow to the right atrium (Figure 2). Cardiopulmonary bypass was utilized for 140 minutes, and aortic clamping for 110 minutes during the left atrial reduction procedure. The construction and anastomosis of the superior neocava was performed with the aorta unclamped and the heart beating. Normal sinus rhythm resumed as soon as the aorta was unclamped. The patient´s post-operative course was uneventful and there was no sign of SVC syndrome. Radioisotope superior venocavography was performed using sulfur-99mTc colloid 5 days after surgery (Figure 3) and was repeated 3 months post-surgery--these studies showed graft permeability. A transmitral flow Doppler echocardiograph showed post-operative recovery of left atrial functional capacity upon reappearance of the atrial «a» wave, which had been absent previously. The study also revealed a significant reduction in LA size.

Fig. 1. This illustration shows how to construct an autologous pericardial tube using a Hegar dilator as a mold.

Fig. 2.Artist´s rendition of the interposition of the autologous pericardial tube in the superior vena cava. The arrow indicates the pericardial graft.

Fig. 3. Radioisotope superior venocavography (5 days post-surgery). The images obtained reveal the adequate flow of radiopharmaceutical material (sulfur^-99mTc colloid) through the subclavian vein, superior vena cava, and the right cardiac cavities, indicating graft permeability.

DISCUSSION

Mitral valve disease is one of the most common causes of chronic AF,³ especially when the LA is large. Nevertheless, valve surgery per se does not eliminate this arrhythmia in the majority of cases. Various surgical techniques have been proposed.^1,2,4-9 We have successfully used the atrial reduction technique described by Sankar¹ in 17 patients who underwent mitral valve surgery with concomitant chronic AF; eliminating chronic AF with this technique is highly effective.^1,2 Experimental studies by Chorro et al¹⁰ have shown that when the atria are distended, they can cause both atrial flutter patterns and complete re-entries. This can be eradicated by the formation of obstacles secondary to surgical suture lines, which can also eradicate complete areas of arrhythmia, such as in the base of the left atrial appendage. The technique also incorporates 2 principles cited by Cox:⁴ isolation of the AF reentrant microcircuits in the LA and reduction of the LA critical mass. This procedure consists of isolating the pulmonary vein heads and extirpation of a circumferential band of LA tissue that includes the base of the left appendage and anastomosis of the LA. The SVC is resected transversely to expose the roof of the LA.

LA transport function can be determined by echocardiographic study.¹¹ The re-establishment of LA transport function can be established by electrocardiography when the «a» wave is apparent after this surgical procedure is performed to eliminate AF. Nevertheless, this new technique is not without complications. We found a potential complication of this procedure is the inadvertent torsion of the heart to the right when performing the LA reconstruction, making it impossible to re-suture the SVC directly because of the risk of developing SVC syndrome caused by partial or total obstruction of the SVC. In the case presented here, this problem was successfully solved by using an autologous pericardial tube to ensure SVC permeability. The interposition of the superior neocava of the pericardium was performed with aortic clamping, with the heart beating, without increasing the duration of cardiopulmonary bypass by more than 25 minutes.

In conclusion, we believe that the use of an autologous pericardial tube to prevent unanticipated SVC torsion during left atrial reduction is an excellent surgical option.

ACKNOWLEDGEMENT

We would like to thank Miss Maria del Carmen Colomer for her valuable assistance in preparing this manuscript.

---

Correspondence: Dr. Ovidio A. García-Villarreal
Vista Florida, 460, Col. Linda Vista.
67130 Guadalupe. Nuevo León. México.
E-mail: [e-mail]