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Ann Thorac Surg 1999;68:1262-1264
© 1999 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Conduction disturbances after superior septal approach for mitral valve repair

^a Department of Thoracic and Cardiovascular Surgery, Jichi Medical School, Tochigi, Japan

Address reprint requests to Dr Misawa, Department of Thoracic and Cardiovascular Surgery, Jichi Medical School, Yakushiji 3311-1, Minami-Kawachi, Tochigi, 329-0498, Japan
e-mail: tcvmisa{at}jichi.ac.jp

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. The superior septal approach sacrifices the sinus node artery, and it requires more invasive incisions into the right and left atria. Therefore, postoperative rhythm disturbances could be troublesome in patients with SSA. In this study, we evaluated perioperative and midterm conduction disturbances in the cardiac rhythms of patients who had a SSA for mitral valve repair.

Methods. Fifty-two patients had mitral valve operations by the superior septal approach, and cardiac rhythm status was assessed. The mean follow-up period was 15 ± 8 months. In patients with normal sinus rhythms preoperatively, serial changes in PR intervals were also assessed. Holter electrocardiograms were used 6 to 12 months postoperatively. Twelve patients who had mitral valve operations by conventional left atriotomy from the right side of the left atrium served as the control group.

Results. There were no operative deaths, but one patient in the experimental group died of cerebral hemorrhage 4 months postoperatively. No intractable arrhythmias occurred. Of the 25 patients who maintained sinus rhythms, preoperative PR interval on electrocardiogram was 155 ± 20 milliseconds. Postoperative PR intervals increased for 1 week, had decreased within 2 weeks postoperatively, and returned to the normal range by 6 months postoperatively. Holter electrocardiograms of 17 patients did not show supraventricular arrhythmias exceeding 3% of the total beats. None of the patients needed pacemaker implantation. The PR intervals of 5 patients with normal sinus rhythms in the control group did not show significant changes perioperatively.

Conclusions. The superior septal approach is excellent for mitral valve operations because it overcomes postoperative dysrhythmias.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
The conventional approaches for mitral valve operations, which do not sacrifice the sinus node artery, include left atriotomy from the right side and the septal approach. In contrast, the superior septal approach (SSA) sacrifices the sinus node artery and requires more invasive incisions into the right and left atria. Therefore, postoperative rhythm disturbances, such as supraventricular arrhythmia and atrioventricular conduction disturbance, could be troublesome in patients who had an SSA. However, SSA provides surgeons with a large operative field even when the left atrium is small. With the SSA, both the surgeon and assistants can observe the operative field, whereas with the conventional approaches assistants can not always observe the operative field. Some studies of rhythm disturbance accompanying SSA have been published previously, but they covered mainly perioperative events, such as premature contraction and bradycardia. We evaluated perioperative and midterm conduction disturbances in the cardiac rhythms of patients who had mitral valve operations by the SSA and compared them with patients who had a conventional approach for the mitral valve operation.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
Between October 1996 and October 1998, 52 patients (SSA group) had mitral valve operations by the SSA, and cardiac rhythm status was assessed. The average age was 55 ± 14 years (range, 15 to 76 years). There were 25 men and 27 women. Preoperative mean pulmonary artery pressure was 29 ± 11 mm Hg, and the mean left atrial diameter was 63 ± 10 mm. Cardiopulmonary bypass time was 158 ± 22 minutes, and ischemic time was 106 ± 18 minutes. The mean follow-up period was 15 ± 8 months (range, 2 to 25 months). Forty-two patients in the SSA group had mitral valve replacement, and 10 had mitral valve plasty. Twenty-five patients had concomitant operations, including aortic valve replacement in 9, tricuspid annuloplasty in 12, coronary artery bypass grafting in 1, atrial septal defect repair in 1, atrial septal defect repair plus tricuspid annuloplasty in 1, and patch plasty for abscess cavity in the mitral annulus in 1. Aortic valve and tricuspid operations were done frequently, and 5 patients had previous mitral or aortic valve operations.

Twelve patients who had mitral valve operations by conventional left atriotomy from the right side served as the control group. The average age of the group was 59 ± 10 years (range, 36 to 72 years). There were 7 men and 5 women. Preoperative mean pulmonary artery pressure was 33 ± 8 mm Hg, and the mean left atrial diameter was 68 ± 19 mm. Cardiopulmonary bypass time was 172 ± 45 minutes, and ischemic time was 111 ± 31 minutes. The mean follow-up period was 30 ± 7 months (range, 23 to 45 months). Eleven patients had mitral valve replacement, and 1 had mitral valve plasty combined with mitral valve annuloplasty. Tricuspid annuloplasty was done in 3 patients, the aortic valve was replaced in 3 patients, and coronary artery bypass grafting was done in 4 patients.

Myocardial protection during the operation was accomplished with moderate hypothermia (28°C to 30°C) and blood cardioplegic solution. In case of bradycardia below 70 beats per minute, right atrial or ventricular pacing between 70 and 90 beats per minute was initiated to obtain a stable postoperative hemodynamic condition.

Postoperative complications were compared in the two groups, and preoperative and postoperative electrocardiograms were analyzed in patients with normal sinus rhythms. Serial changes in PR intervals were assessed to study the conduction disturbances that occurred with this approach. Holter electrocardiograms were used 6 to 12 months postoperatively to assess cardiac rhythm status in the SSA group.

Postoperative mortality and morbidity rates were based on the revised guideline by Edmunds and associates [1]. Statistical analysis was done using the t test and Wilcoxon test with STAX ’98 (Nakayama-shoten, Tokyo, Japan). Data are presented as mean ± standard deviation, and p values less than 0.05 were considered significant.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Postoperative complications
In patients who had the SSA, there were no operative deaths. No intractable arrhythmias occurred in the early postoperative phase. There was one late death from cerebral hemorrhage 4 months postoperatively. Paravalvular leakage was recognized in 1 patient 2 months postoperatively, and he had reoperation 14 months after the initial operation because of advancing heart failure. One cirrhotic patient with both aortic and mitral valve replacement had reexploration because of mediastinal bleeding 4 hours postoperatively. There were no other valve-related or treatment-related complications.

In the control group, no intractable arrhythmias occurred in the early postoperative phase. Low cardiac output syndrome developed in the patient who had mitral valve plasty developed 3 hours after operation, thus he subsequently had mitral valve replacement. No other complications were observed in the control group.

Changes in postoperative electrocardiograms
Twenty-six patients had normal sinus rhythms preoperatively. Eleven had transient atrial fibrillation or junctional rhythms for approximately 2 weeks. Twenty-five patients maintained sinus rhythm, and atrial fibrillation developed in 1 patient by final follow-up. Five of 26 patients with preoperative atrial fibrillation showed sinus rhythms in the early postoperative phase. In one patient atrial fibrillation recurred by 6 months postoperatively, and another died of cerebral bleeding 4 months postoperatively. Another 10 patients with atrial fibrillation showed transient junctional rhythms postoperatively.

Serial changes in PR intervals were assessed in the 25 patients who maintained their sinus rhythms (Fig 1). The mean preoperative PR interval on electrocardiograms was 155 ± 20 milliseconds, indicating no conduction delay. However, postoperative PR intervals were significantly prolonged for 1 week (p = 0.02), decreased within 2 weeks postoperatively, and returned to normal by 6 months postoperatively. Five patients had transient I° atrioventricular blocks, and 1 developed a permanent I° atrioventricular block. No other conduction abnormalities were observed.

View larger version (16K): [in this window] [in a new window]   Fig 1. PR intervals of patients who had the superior septal approach (SSA) became longer postoperatively and decreased gradually. However, those of patients who had a conventional approach did not change significantly (p values of any PR intervals 0.10). Between the two groups, there was a significant difference in serial PR interval changes (p = 0.05 by the generalized Wilcoxon test).

Postoperative echocardiography 1 to 2 months after operation found no case of atrial septal defect.

Five patients in the control group maintained normal sinus rhythms perioperatively. The other patients had atrial fibrillation throughout their follow-up periods. PR intervals of the 5 patients were also examined. The mean preoperative interval was 162 ± 21 milliseconds, and postoperative PR intervals did not show significant changes (p values of any PR intervals 0.10, Fig 1). No patient had atrioventricular block. There was a significant serial change between the two groups (p = 0.05). None of the 12 patients in the control group needed implantation of a pacemaker.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
Conventionally, a left atriotomy made posterior to the interatrial groove or a transseptal approach is chosen for mitral valve operations. However, these approaches can yield a limited operative field in cases of a small left atrium or repeat operation. Poor visibility in a limited field might result in an inaccurate surgical procedure. Mitral valve plasty, which is preferable to valve replacement because of the better quality of life postoperatively, requires optimal exposure of the valve and the subvalvular apparatus. In such a case, precision and reliable technique will yield a successful outcome. Therefore, excellent exposure of the mitral apparatus is essential. In addition, it would be advantageous for a young surgeon to do the surgical procedure in a large operative field where the instructor could observe the procedure closely.

The SSA can provide a larger operative field than conventional approaches. The sinus node artery arises from the right coronary artery in about 55% of hearts and from the left circumflex or main coronary artery in the remaining hearts. When it originates from the right coronary artery, it runs posteriorly and superiorly over the anterior wall of the right atrium and beneath the right appendage to the base of the superior vena cava [2]. Therefore, the sinus node artery frequently must be sacrificed for SSA. There will be collateral blood flows in the postoperative recovery phase, but blood supply will be reduced in the early postoperative phase. Moreover, the atrial incision required for SSA is longer than that for conventional approaches, which might interfere with the cardiac conduction system, resulting in conduction disturbances and arrhythmias. Some investigators have already reported rhythm disturbances after SSA.

Utley and associates [3] and Kon and colleagues [4] reported high risk of loss of sinus rhythm with SSA, but Gaudino and associates [5] mentioned that SSA was not associated with a greater incidence of rhythm disturbances. Masuda and coworkers [6] found a higher incidence of dysrhythmias with SSA in the early postoperative period than that with the conventional right lateral left atriotomy, and there was a similar incidence of dysrhythmias for both methods in the late period. In addition, Smith [7] showed a change in the P-wave axis and morphology possibly related to division of the sinus node artery at late follow-up visits in patients who had the SSA. They also confirmed the beneficial aspect of SSA, an excellent operative field. The possible causes of the postoperative dysrhythmias with SSA are mentioned above. The changes of PR interval on electrocardiogram in the patients who had the SSA, which were prolonged in the early postoperative phase but returned to normal range in the late phase, might be caused by newly developed collateral blood flows to the sinus node or cardiac conduction systems. Further studies are required to confirm these hypotheses. The SSA group had the potential risk of residual atrial septal defect, but postoperative echocardiography found no cases of atrial septal defect.

Conventional left atrial incision in the control group was longitudinal, approximately 5 to 6 cm. The sinus node artery is not sacrificed. Even in cases requiring tricuspid operation, right atrial incision was shorter than the that in the SSA group. Longer incision length might be a cause of stable PR intervals after operation.

In our study, patients with bradycardia less than 70 beats per minute were routinely paced during the early postoperative phase, and no patients had medically intractable bradycardia more than 2 weeks postoperatively. Moreover, no patient needed implantation of a permanent pacemaker because of symptomatic or latent bradycardia as detected by Holter electrocardiograms at the median follow-up time of 15 months.

Excellent visibility of the mitral valve is important for surgical treatment. It yields successful clinical results and educational opportunities for surgical residents. Some clinical problems, including postoperative rhythm disturbances, can occur with the SSA, but they can be controlled medically or with transient electrical pacemaking in the early postoperative phase. Conventional approaches for mitral valve operations can also produce postoperative rhythm disturbances [3, 5, 6]. We conclude that SSA is an excellent approach for mitral valve operations that overcomes postoperative transient dysrhythmias.

	References

Top Abstract Introduction Patients and methods Results Comment References

 

1. Edmunds L.H., Clark R.E., Cohn L.H., Grunkemeier G.L., Miller D.C., Weisel R.D. Guideline for reporting morbidity and mortality after cardiac valvular operations. Ann Thorac Surg 1996;62:932-935.[Abstract/Free Full Text]
2. Kirklin J.W., Barratt-Boyes B.G. Cardiac surgery, 2nd ed. New York: Churchill Livingstone, 1993:3-60.
3. Utley J.R., Leyland S.A., Nguyenduy T. Comparison of outcomes with three atrial incisions for mitral valve operations. J Thorac Cardiovasc Surg 1995;109:582-587.[Abstract/Free Full Text]
4. Kon N.D., Tucker W.Y., Mills S.A., Lavender S.W., Cordell A.R. Mitral valve operation via an extended transseptal approach. Ann Thorac Surg 1993;55:1413-1417.[Abstract]
5. Gaudino M., Alessandrini F., Glieca F., et al. Conventional left atrial versus superior septal approach for mitral valve replacement. Ann Thorac Surg 1997;63:1123-1127.[Abstract/Free Full Text]
6. Masuda M., Tominaga R., Kawachi Y., et al. Postoperative cardiac rhythms with superior septal approach and lateral approach to the mitral valve. Ann Thorac Surg 1996;62:1118-1122.[Abstract/Free Full Text]
7. Smith C.R. Septal-superior exposure of the mitral valve. The transplant approach. J Thorac Cardiovasc Surg 1992;103:623-628.[Abstract]

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