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Eur J Cardiothorac Surg 2001;20:262-269
© 2001 Elsevier Science NL
a Cardiac Surgery Division, Civic Hospital, Brescia, Italy
b ‘Salvatore Maugeri’ Foundation IRCCS, Division of Cardiology, Gussago, Italy
c Section of Medical Statistics and Biometrics, Brescia, Italy
Received 17 October 2000; received in revised form 18 April 2001; accepted 30 April 2001.
Corresponding author. Tel.: +39-030-3995636; fax: +39-030-3995004
e-mail: roberto_lorusso{at}iol.it
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Abstract |
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 Top Abstract 1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...Appendix B. Editorial CommentReferences |
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Key Words: Mitral valve repair • Double-orifice mitral valve • Mitral incompetence • Stress-test echocardiography
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1. Introduction |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...Appendix B. Editorial CommentReferences |
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Debate, however, persists on the potential drawbacks of this procedure, namely, the occurrence of mitral stenosis after the surgical correction, the dynamic behaviour of such a redesigned valve and lastly the long-term efficacy and durability of this procedure.
Our study specifically addressed the evaluation of the haemodynamic effects of a DO repair in a selected group of patients to provide useful insights on such a novel valve configuration that inevitably implies influence on valve function and related fluid dynamics. Furthermore, we assessed the effects of the DO procedure during stressful conditions in order to better elucidate haemodynamic and functional characteristics in this peculiar setting, which could have some impact on the surgical strategy.
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2. Methods |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...Appendix B. Editorial CommentReferences |
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Preoperative patient profile is displayed in Table 1. Preoperative mitral regurgitation had been severe (++++) in all patients. The mechanisms of regurgitation had been anterior leaflet prolapse in 11 patients (40%), prolapse of both leaflets in eight patients (30%) and posterior leaflet prolapse in eight patients (30%). The etiology had been degenerative in 14 patients (52%), infective in seven patients (26%) and rheumatic in six patients (22%). All patients had undergone conventional DO repair as originally described [7]. Annuloplasty had been carried out in 24 patients by the application of a rigid classic Carpentier ring in 13 patients (48%) and glutaraldeheyde pretreated autologous pericardial ring in 11 patients (41%), respectively. No annular remodelling had been used in three patients (11%). In three patients, commissural edge-to-edge technique had also been performed [7], whereas one patient had received conventional posterior quadrangular resection. Associated procedures had been aortic valve replacement (two patients) and CABG (two patients).
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2.1. Echocardiographic study protocol
All patients underwent bicycle ergometre stress test in the supine position, with a 25 W incremental step every 3 min, until 70% of maximal age-predicted heart rate was reached. Real-time phased array echo-Doppler recordings were obtained at rest and during maximal exercise with a GE Vingmed CFM 750 CV (2.75 or 3.25 MHz transducer). The examinations were carried out by two experienced investigators. Digital images were stored on a magneto-optical disk for subsequent analysis.
LV diameters and volumes (area–length method) were determined from two-dimensional parasternal long-axis view and from apical four-chamber view, respectively. Calculations of LV fractional shortening and LV ejection fraction were then derived from diameters and volumes, respectively. Continuous-wave Doppler was used to obtain transmitral pressure gradient (TPG); both mean and peak gradients were considered. When regurgitant jet was present, maximal velocity of tricuspid Doppler tracing was measured to estimate systolic pulmonary artery pressure. A fixed value of 10 mmHg has been added as estimated right atrial pressure, after determination of inspiratory collapse of the inferior vena cava [14]. Measurements of all echo-Doppler examinations were performed in a single day, by only one investigator. Mean value of three measurements was considered for each variable.
2.2. Statistical analysis
All values are expressed as mean±standard deviation. We used the Wilcoxon rank sum test, given the skewed distribution of peak TPG (PTPG), to analyze possible differences of this variable in relation to the type of ring. A logistic regression was also performed to evaluate the prediction role of PTPG in relation to the categorised variable pulmonary hypertension (1 present, 0 absent). Student's t-test for unpaired variables was used for the analysis of volumes, diameters and contractile performance of the left ventricle pre- and postoperatively. A P value less than 0.05 was considered as significant.
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3. Results |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...Appendix B. Editorial CommentReferences |
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Table 2 shows the haemodynamic data recorded at rest preoperatively and at the time of investigation, as measured by transthoracic echocardiography. Significant mitral valve regurgitation (+++/++++) was shown in five patients (18%). Pulmonary hypertension (moderate in all cases) was detected in six patients (22%). Left ventricular contractility was normal in all patients. Supine exercise significantly increased heart rate and systemic blood pressure. Table 3 shows functional and haemodynamic data obtained during exercise. All patients but one showed enhancement of left ventricular contractility during exercise. In one patient left ventricular ejection fraction fell from 54 to 47% at peak exercise. One patient showed mitral systolic anterior movement with left ventricular outflow tract obstruction with a significant intraventricular gradient (55 mmHg). No substantial modifications were elicited by stress conditions in terms of mitral valve insufficiency. Conversely, TPG showed a significant (P<0.001) increase in both peak and mean values at peak exercise (from 7±4 to 17±10 and from 3±2 to 8±6 mmHg, respectively) (Fig. 1 ). Furthermore, 12 patients showed PTPG values which doubled at peak exercise if compared with resting data (Fig. 2 ). Similarly, the number of patients who developed pulmonary hypertension during exercise rose from six to 13 cases (P<0.001), which confirmed the trend towards a restrictive behaviour of a DO valve during strenuous cardiocirculatory conditions (Fig. 3 ).
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The associated reconstructive techniques to achieve mitral competence (commissural closure) apparently did not affect haemodynamic response to exercise after DO repair. Indeed, no pulmonary hypertension was detected in two cases either at rest or at peak exercise, whereas the third patient developed moderate pulmonary hypertension only during stressful conditions.
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4. Discussion |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...Appendix B. Editorial CommentReferences |
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Maisano et al. [15] reported on the computational model of blood flow through a DO valve and showed that blood velocity was exclusively related to the total valve area irrespective of the conformation and equality of the two orifice areas. Accordingly, echo-Doppler measurements were shown to provide reliable estimation of transvalvular pressure gradient by simply analyzing blood flow velocity in one orifice. Nonetheless, a major limitation of this study was linked to the evaluation of a virtual and therefore inanimate model of valvular physiology.
The effects of exercise on the normal mitral valve physiology have been clearly reported by Rassi et al. [16] who showed that exercise state induces augmentation of transmitral blood flow by an increase in mean diastolic cross-sectional area. These findings suggest that the maintenance or the least limitation of natural diastolic motion of the mitral valve is an important component of MVRep to ensure unrestrictive transvalvular flow rates, especially during high flow cardiocirculatory conditions.
From a purely surgical standpoint, the procedure implies the testing, at the end of the repair, by which the dimensions of the obtained orifices are calculated. So, the induction of haemodynamically significant mitral stenosis is extremely unlikely under a resting condition [11–13]. However, though acceptable global valve area is usually maintained after DO repair, the functional consequences of two orifices were yet to be defined during exercise.
These premises prompted us to study a selected group of patients previously submitted to DO repair. Our findings demonstrated that a DO valve may predispose to restrictive transmitral blood flow and hence to pulmonary hypertension, which is more evident during exercise conditions. Echocardiographic estimation of LV function at rest and during exercise in our study group showed preserved functional state which excludes the potential correlation between increased transvalvular gradient and impaired diastolic ventricular filling or systolic performance. Moreover, the extent of mitral insufficiency did not influence and was not statistically related to exercise-induced pulmonary hypertension, since patients with no mitral incompetence at rest and at high flow conditions developed pulmonary hypertension. On the other hand, haemodynamically significant mitral regurgitation, which was assessed at resting conditions in a few patients, did not change during the exercise test despite increased pulmonary resistance, making the hypothesis of increased pulmonary hypertension due to augmented valve incompetence inconsistent. Furthermore, the appearance or deterioration of pulmonary hypertension was apparently related to the type of annuloplasty performed, despite the absence of linear correlation. We speculate that limitation of mitral annular excursion and valve opening reserve due to the central suture might partially explain the restricted transmitral blood flow.
Umana et al. [17] specifically addressed annular mechanics in a sheep model of DO repair in the setting of acute ischaemic mitral insufficiency, and showed preserved annular motion and ventricular function as compared to conventional MVRep. This experimental model, however, did not include annuloplasty procedures.
Our study suggests that rigid fixation of the mitral annulus in DO repair may further predispose to reduced mitral valve diastolic motion since rigid prosthetic ring induced a more marked increase in transvalvular gradient during exercise test as compared to flexible biological annular support. This finding is in accordance with previous investigations performed at our institution and by others on the effects of different approaches in terms of annular remodelling in MVRep [18–20]. As suggested by Umana et al. [11], annular remodelling during DO repair should be achieved with minimal intervention and, in our opinion, with flexible and limited (C-type) devices to partially preserve the diastolic mechanical contribution of the native annulus and to counterbalance the centripetal effect of the central suture.
Recurrent mitral insufficiency may be encountered in some patients at follow-up, but the influence of such redesigned valves on fluid dynamics, which may affect efficacy and durability of MVRep is still unknown. A thorough analysis of our complete patient population is under way to specifically elucidate the precise mechanism of recurrent mitral regurgitation and to disclose potential determinants of unfavourable outcome after the DO repair.
The DO repair had a favourable impact on several anatomical and functional cardiac parameters in our study population. Remarkable reduction in preoperative LA and LV dimensions were clearly documented at follow-up. Furthermore, the majority of patients showed competent valve, with no modification even under stressful haemodynamic conditions. Therefore, we can confirm that DO repair may be a valuable technique to face complex mitral lesions which could otherwise lead to valve replacement or to extremely complex reparative techniques with uncertain outcome.
4.1. Study limitation
Our study has been carried out on a limited patient population; therefore, the statistical analysis could have been adversely influenced by inappropriate study power. Patients were not randomised according to the application or to the type of annuloplasty procedure. No homogeneity in terms of etiology of the disease and patient age was present, making the impact of these inherent differences in mitral valve behaviour possible. All selected patients underwent exercise test, also in the presence of haemodynamically significant mitral incompetence, which could have affected some data interpretation. Nonetheless, these patients represented only a minority and the behaviour of such valve regurgitation in the presence of a DO valve was considered anyhow important to allow appropriate decision making for hypothetical indication of reoperation.
In conclusion, our study showed the haemodynamic effects of a redesigned DO valve for MVRep recorded at rest and during exercise conditions. A tendency towards restrictive patterns of transmitral blood flow was shown, particularly under strenuous cardiocirculatory conditions. Our data also suggest that the postoperative functional mitral stenosis does not relate to the application of the DO valve per sé as the only causal factor; rather, it is the result of a combination of several factors, particularly related to annular remodelling. These insights may be meaningful to design a more efficient application of a DO repair (unrestrictive annuloplasty) to correct complex mechanism of mitral insufficiency. Further studies are required to better elucidate the modifications of the actual DO mitral dynamism and fluid dynamics following DO repair, particularly without the influence of prosthetic annular support.
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Footnotes |
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Appendix A. Conference discussion |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...Appendix B. Editorial CommentReferences |
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Dr Borghetti: Undoubtedly this is just our preliminary report. This study has been conducted on just half of the patients who underwent double-orifice repair in our center. So the high percentage of failure with this particular technique is maybe due to the difficulty in the selection of patients and interpretation of the mechanism of regurgitation. In fact, last year we presented a similar study carried out in a population of patients who had undergone conventional posterior quadrangular resection and no or trivial mitral valve regurgitation had been found.
Dr S. Collins (Umea, Sweden): As you know, we have other variables which influence the mitral transgradient and pulmonary hypertension. Have you considered such variables, such as left ventricular function and so on?
Dr Borghetti: Yes. We have taken into account other variables such as the degree of mitral regurgitation or cardiac rhythm, which could influence the transmitral pressure gradient, but no correlation was found. Moreover, we tried to correlate the presence of left ventricular dysfunction with the development of pulmonary hypertension, which would be influenced by that, but again, no correlation was found.
Dr O. Alfieri (Milan, Italy): How could you include in your study a population of patients who had severe mitral insufficiency and pulmonary hypertension at baseline evaluation? You have simply demonstrated that a patient who did not have a good repair does not tolerate an effort.
Dr Borghetti: The patients had been chosen with strict inclusion criteria and we excluded patients with preoperative pulmonary hypertension. Moreover, I have mentioned before that other variables, able to influence our findings during exercise, have been taken into consideration and we failed to show any correlations between them.
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Appendix B. Editorial Comment |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...Appendix B. Editorial CommentReferences |
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In this issue of the Journal, Dr Borghetti and associates raise a question that has been in the mind of most surgeons faced with this innovative technique. They report the postoperative echocardiographic findings in a group of 27 patients followed for a mean of 47 months after edge-to-edge suture of the mitral leaflets (‘Alfieri's stitch’). An annuloplasty had been added in 88% of the patients. At peak exercise, an important transmitral gradient became apparent with pulmonary hypertension in 13 cases. Significant regurgitation was detected in six cases (22%). One case of significant systolic anterior movement (SAM) was observed. These rather poor results must be carefully analyzed and should not immediately disqualify a technique that because of its simplicity, has probably saved many mitral valves.
A criticism of these results might be the case selection. Out of the 75 patients with the procedure, only 27 non-randomized cases were studied. Although the inclusion criteria are described, whether a natural tendency towards studying patients with a poor clinical outcome is possible. Also, the small number of patients minimizes the value of the study. However, early reports of a new technique tend to be limited in the number of patients. This argument plays both ways since the early publications by Alfieri's group did not report many cases either [21]. It can also be argued that although the sizes of the annuloplasty rigid rings used by the authors were large, they might further the diastolic restriction imposed by the leaflet suture.
This ‘double-orifice’ technique has recently become quite popular, primarily because of its technical simplicity. As with all new surgical techniques, their originators, because of their dedication to the subject, careful technique and experience that eliminates earlier mistakes, tend to report better results than their followers. These early good results encourage the optimistic view that the new approach can solve most problems. Usually, time and hard reality modulate the initial enthusiasm until a balance is achieved and the more limited and precise indications become progressively established. Therefore, it is beneficial to learn of the problems that an ‘outsider’ has encountered when applying this new technique.
Contrary to many emerging techniques, this one is not limited by its technical complexity. Confusion might have arisen about the need for adding an annuloplasty to the double-orifice technique. Although initially Dr Alfieri limited the surgery to only his stitch, more recent reports show a progressive increase in the use of a contention annuloplasty. In his recent publication (corresponding to his presentation at the last Annual Meeting of the Society [21] 91% (75/82) of the patients had an annuloplasty while at the presentation 69% (47/68) had an annuloplasty. The actual reasons that led to this increase should be known. Also, it was understood that Dr Alfieri considered this technique as a partial suture closure at any point of the mitral coaptation line which included the commissures [22] and therefore not necessarily a ‘double-orifice’ technique. Appropriately, the authors of the present report include three such cases.
Two main questions about this technique must be addressed today: its durability and its precise indications. A recent study from the Stanford group [23], in an experimental model of ischemic regurgitation, has shown an abnormal cyclic increase in tension (particularly during diastole) at the level of the Alfieri stitch. The clinical implications of these findings are unknown. Only time will elucidate this question.
Another important point is whether this technique can and should be applied to all cases of mitral regurgitation. Again, while the initial reports included rheumatic cases, present information tends to concentrate on the excellent results obtained in myxomatous disease. A possibly clearer indication is prolapse in the presence of a calcified annulus where leaflet resection is hazardous although more complex techniques such as chordal replacement are available. It is probably unwise to expect good results in rheumatic valves where fibrotic leaflets do not allow for their partial closure without impunity. Twenty-two percent of the patients reported by Borghetti and associates had a rheumatic etiology. An interesting area where this technique is receiving attention is in cases of ‘functional’ regurgitation where our ignorance of its mechanism limits the benefit of a simple reducing annuloplasty. The simplicity of the method, possibility of being performed through an open ventriculotomy and extra time needed for an annuloplasty has encouraged some groups to use it systematically in ischemic and dilated cardiomyopathies.
Dr Borghetti and collaborators should be congratulated for raising questions that encourage fruitful discussion. In this field close to geometry, dispassionate reporting of positive and negative results will determine its value and decide whether to incorporate it to the mitral repair armamentarium. So far, it should be observed carefully.
Carlos M.G.Duran
International Heart Institute of Montana, 554 West Broadway, Missoula, MT 59802-4008, USA
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References |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...Appendix B. Editorial CommentReferences |
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  F Antonini-Canterin, C C Beladan, B A Popescu, C Ginghina, A C Popescu, R Piazza, E Leiballi, B Zingone, and G L Nicolosi Left atrial remodelling early after mitral valve repair for degenerative mitral regurgitation Heart, June 1, 2008; 94(6): 759 - 764. [Abstract] [Full Text] [PDF]
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