| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||
J Thorac Cardiovasc Surg 2008;135:1304-1305
© 2008 The American Association for Thoracic Surgery
Invited Commentary |
It can be hard to get these patients to return for follow-up, and I commend you on your persistence in what is a large series of follow-up MRI scans.
All of your patients were in permanent or persistent AF preoperatively. We have had tremendous problems obtaining MRI scans in these patients because of the difficulty in gating the irregular rhythm. How did you overcome these challenges and are you sure you did not miss part of the cardiac cycle in these patients?
Dr Marui. "Thank you, Dr. Damiano, for your kind comments and questions. We recognize your contribution to this field of AF surgery" Your first question is an important one, because gating of MRI in patients with AF is difficult. We used 3 to 5 cardiac-cycle series to evaluate the patients with AF for MRI evaluation. If patients recovered sinus rhythm, we used 3 cardiac-cycle series and averaged these data, and used them in the present study.
Dr Damiano. In your analysis you have omitted an important component of atrial emptying. The CF of the atrium is extremely important. By this I mean there is a certain percentage of blood flow of the LA volume that goes directly from the pulmonary veins through the mitral valve into the left ventricle that cannot be measured by your MRI atrial volumes. This can be calculated, though, by subtracting the reservoir and booster pump volume from the LV stroke volume, which you can obtain. In 20 healthy human volunteers we found that the conduit volume or the CF makes up approximately 40% of the LA contribution to LV filling. So you haven't told us about approximately 40% of LA emptying. Moreover, the ratio between the reservoir and the conduit volume is an important indicator of ventricular function, which is another confounder in this study. What were the differences in the CF of the left atrium in these patients? How may have it affected these results by just presenting booster pump and reservoir volumes?
Dr Marui. "That is a very excellent question." As Dr Damiano points out, we used only 2 functions: BPF and RF. The last one is CF, and this is an important contribution to LA function. However, when we performed this study, we didn't know how to evaluate CF by MRI. Therefore we studied only BPF and RF. We recognize that Dr Damiano's institution (Department of Surgery, Barnes-Jewish Hospital, Washington University School of Medicine) has evaluated LA function, including CF by MRI, and are now obtaining more data, and we would like you to teach us how to evaluate CF.
Dr Damiano. It is excellent work, but it is still something to remember when you are looking at atrial dynamics. Postoperative ventricular systolic function, particularly diastolic relaxation, has a tremendous impact on LA function. I would say that in your control group, 43% of patients had mitral valve replacement versus only 33% in the volume reduction group. There was a similar discordance in the number of repairs. This may have had an impact on the postoperative ventricular function between the groups. Moreover, the types of concomitant surgeries varied in the 2 groups, as you acknowledged in your study limitations. Did you make any attempt to try to control for postoperative differences in ventricular function and how they may have affected your results? How can we be assured that the differences in atrial emptying that you have shown in this study aren't really a reflection of differences in ventricular function between the 2 groups unrelated to the arrhythmia operation but more related to their mitral valve surgery?
Dr Marui. As Dr Damiano points out, this is a major limitation of the study. We used 2 types of mitral valve surgery, and this may affect the results of the LA compliance, RF, and BPF. We must do a prospective randomized study for the evaluation of LA function including several postoperative parameters in the future.
Dr Takashi Nitta (Tokyo, Japan). I have a question about the mechanism of the improvement of the LA function. Everybody can understand that atrial systolic function can be increased and improved by volume reduction. It is like a Batista operation; reduced volume results in better contraction. I still have a problem understanding why the RF improved at the same time, because RF and systolic function are supplemented by each other. If the patient has sufficient systolic function, the patient no longer needs RF, and if the patient has sufficient RF, the patient no longer needs the atrial kick. So can you explain why the RF also improved even when the atrial systolic function had already improved?
Dr Marui. "Thank you. A very good question but a difficult question to answer." Before this study, we speculated that BPF would improve, but as you pointed out, the RF did not improve. The results were as shown here. The reasons are unclear. As you say, the improvement of LA RF in the present study might not mean recovery of atrial compliance alone. However, the mechanism of LA functional recovery after the LA volume reduction surgery is not fully understood; therefore, the reason for the improvement of LA compliance should be addressed in future studies.
Related Article
J. Thorac. Cardiovasc. Surg. 2008 135: 1297-1305.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
