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Ann Thorac Surg 2006;82:828-833
© 2006 The Society of Thoracic Surgeons
a Cardiothoracic Surgery, Monash Medical Center, Clayton, Victoria, Australia
b Cardiology Units, Monash Medical Center, Clayton, Victoria, Australia
c Department of Surgery, Monash University, Clayton, Victoria, Australia
d Center for Heart and Chest Research, Monash University, Clayton, Victoria, Australia
Accepted for publication March 29, 2006.
* Address correspondence to Prof Smith, Department of Surgery, Level 5, E Block, Monash Medical Centre, 246 Clayton Rd, Clayton, Victoria 3168, Australia (Email: julian.smith{at}med.monash.edu.au).
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Abstract |
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METHODS: A retrospective analysis was performed on 243 patients undergoing PMV at a single institution over a 14 year period.
RESULTS: Fifty (21%) of 243 patients, comprising 44 women and 6 men and aged 55 ± 14 years, underwent cardiac surgery at a median interval of 6 months (range, 0 to 130) after PMV. Nine (18%) underwent a procedure within 15 days, and 41 (82%) had a procedure more than 15 days after the valvuloplasty. After PMV, surgery-free survival was 85% at 1 year, 83% at 2 years, 81% at 3 years, 80% at 4 years, and 80% at 5 years.
CONCLUSIONS: The need for surgery after PMV is not uncommon. Independent predictors of surgery after PMV included severity of mitral regurgitation (p < 0.003) and a higher echo score (p < 0.039).
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Material and Methods |
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Baseline demographic and clinical data were obtained by interview and examination of medical records, while a baseline NYHA classification was performed as part of the clinical workup. Individual consent was not required for the collection of this data, which is covered under The Victorian Cardiac Surgery Database Project Patient Information Sheet Version No. 2 (Southern Health Human Research Ethics Committee A Project No. 01040A, approved July 18, 2001).
Echocardiography
Patients underwent M-mode, two-dimensional, and Doppler transthoracic echocardiography on the day prior to PMV to evaluate mitral valvular and subvalvular morphology, and to measure the transmitral pressure gradient and left atrial diameter. Measurements were performed according to the recommendations of the American Society of Echocardiography [11]. Mitral valve area was primarily obtained with continuous wave Doppler echocardiography using the pressure half time method [12], but planimetry of the short axis two-dimensional echo image at the level of the tips of the mitral valve leaflets was employed in approximately 10% of cases where Doppler velocity envelopes were less than optimal. Mitral valve morphology was quantitated using the "echo score" of Wilkins and colleagues [13], derived by grading valve calcification, subvalvular morphology, valve thickness, and valve mobility on a scale from 0 (normal) to 4 (severely abnormal). After its introduction at our institution in 1990, 220 patients also underwent transesophageal echocardiography prior to PMV to exclude the presence of a left atrial thrombus. Transthoracic echocardiographic measurement of valve area and transmitral pressure gradient was repeated two days after PMV, a time interval previously validated for pressure half-time measurements of the mitral valve area after transseptal puncture [14].
Valvuloplasty Procedure
In the catheterization laboratory, a 7.5F Swan-Ganz thermodilution catheter (Baxter Healthcare Corp, Irvine, CA) was inserted to measure cardiac output by thermodilution, while a 6F polymer pigtail catheter (C.R. Bard Inc, Galway, Ireland) was inserted into the left ventricle for pressure measurement and ventriculography. Mitral regurgitation was assessed before and after PMV during left ventricular cineangiography and its degree graded on a scale of 0 to 4. Coronary angiography was performed in selected patients, based on an individual coronary artery disease risk assessment.
After atrial transseptal puncture with a Brockenbrough needle, an 8F transseptal catheter was advanced into the left atrium and the mean gradient across the mitral valve was obtained by simultaneous recordings of the left atrial and left ventricular pressures. The mitral valve was subsequently dilated using double cylindrical balloons [1], an Inoue balloon catheter (Toray Med Ind, Tokyo, Japan), or a valvulotome [2, 3]. Valve dilatations were repeated until there was a satisfactory increase in mitral valve area, a reduction in the left atrial pressure or transmitral pressure gradient, or an increase in the severity of mitral regurgitation on auscultation or transthoracic echocardiography. Cardiac output and pressure measurements were repeated after completion of valve dilatation.
Clinical Follow-Up
There was no occurrence of in-hospital stroke, myocardial infarction, or death related to the PMV procedure. Unless a prior endpoint event intervened, initial follow-up was performed at 3 months, at which time a NYHA classification was determined. Subsequent follow-up was performed annually, when information about improvement or deterioration in symptomatic status, hospital admissions, and cardiac surgical procedures was obtained by a mailed questionnaire or telephone interview, or from the family doctor or referring cardiologist. Operation notes were obtained on all patients who underwent surgery after PMV. Follow-up was concluded in September 2002, with a follow-up period of at least three months unless a prior event occurred. Median duration of follow-up was 38 months (range, 0 to 153 months).
Statistical Analysis
Statistical analyses were performed using Statistical Package for the Social Sciences version 10.0.5 (SPSS Inc, Chicago, IL). Independent predictors of cardiac surgery were identified by multivariate analysis with stepwise Cox proportional hazards regression [15], using entry variables with a p value 0.1 or less on a univariate Cox analysis. Two separate stepwise models were constructed. The initial model evaluated demographic and preprocedural variables only. The second model combined the foregoing variables with postprocedural variables and the NYHA classification at the initial three-month follow-up, the latter being included because it is a powerful predictor of long-term outcome after PMV [7]. The hypothesis of proportional hazards was verified graphically [15], while the hazards ratios with 95% confidence limits were obtained from the Cox regression model. Results are presented as mean ± SD and were considered statistically significant at p less than 0.05.
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Results |
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Univariate Analysis
No major differences were apparent in the demographic features of patients who did or did not undergo surgery after PMV (Table 1). However, while mitral valve area was similar patients undergoing surgery after PMV had a higher echo score, a greater degree of mitral regurgitation (MR) and a higher left atrial pressure before PMV, a higher incidence of cardiac tamponade during PMV, a more pronounced mitral gradient, more severe mitral regurgitation, a lower cardiac output, and higher left atrial pressure after PMV, as well as a higher NYHA classification on first follow-up (Table 2).
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Comment |
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This study has shown that surgery is not uncommon after PMV. Approximately one in five patients went on to have surgery after PMV; however, only a small proportion (18%) of these had a procedure within two weeks. The majority (82%) underwent surgery outside of two weeks, and most in the initial year, after the PMV, with surgery-free survival relatively stable after this time.
There was no difference in the demographic variables of patients who did or did not undergo surgery after PMV (Table 1). This finding is interesting in that it shows factors that normally might be expected to increase the need for cardiac surgery; for example, age and the presence of concomitant coronary artery or other valvular disease do not seem to play a part in the need for surgery after PMV. A prior smoking history approached statistical significance; however, it did not attain it. This may be due to the small sample size of the surgical group.
When the multivariate analysis was confined to demographic and preprocedural factors, in order to establish if it was possible to identify patients at greater risk of surgery before the valvuloplasty procedure, two factors emerged as independent predictors: (1) MR and (2) echo score. These are, therefore, important considerations when deciding to recommend PMV in a given patient.
The presence of MR before the PMV as an independent predictor of the need for surgery after the valvuloplasty is probably due to the fact that while inflation of the balloon is effective in relieving MS, it also causes or even worsens any preexisting MR, due to mechanical tearing of the mitral valve leaflets and commissures [16]. This is also highlighted in the fact that the most common primary clinical indication for surgery after valvuloplasty was moderate to severe MR.
Echocardiography is the mainstay in the noninvasive evaluation of mitral stenosis [13] and the echo score is also an independent predictor of the need for surgery after PMV. The transthoracic echocardiogram provides an evaluation of the valvular apparatus, associated valve lesions, and subvalvular structures. Doppler echocardiography provides information regarding pulmonary artery pressures and the degree of tricuspid regurgitation [17].
The morphologic evaluation of the mitral valve and subvalvular apparatus is objectively based on the echocardiographic score. The scoring system evaluates leaflet thickening, subvalvular deformity, calcification, and leaflet mobility as the main features of valve deformity. A maximum score of 4 indicates the highest level of deformity in each of the four features. Thus, minimally deformed valves have a score below 6, whereas valves with severe deformity have a score approaching 16. It has generally been accepted that patients with echo scores less than 8 have a better outcome with balloon mitral valvuloplasty [18], and this study agrees with this finding as we have shown the echo score to be an independent predictor of surgery after PMV. Furthermore, while not an independent predictor as such, the proportion of patients with echo scores greater than 8 in the surgical group was statistically significant when compared with the nonsurgical group. On analysis of all the preprocedural, procedural, and postprocedural variables, however, only three postprocedural variables were independent predictors of surgery after PMV: (1) MR, (2) mitral (M) gradient, and (3) NYHA on first follow-up.
As stated previously, while PMV relieves mitral stenosis, it may also cause mitral regurgitation. The outcome of this analysis is consistent with the observation that moderate-moderate-severe MR was the most common surgical indication at the time of operation.
The M gradient is also an independent predictor. This probably relates to the fact that a high M gradient represents a severely stenotic valve, one that may not be initially suitable for PMV, and a persisting high M gradient after the PMV reflects lack of success of the procedure, a finding underscored by the fact that persistent and severe mitral stenosis and recurrent mitral stenosis were indications commonly encountered in the surgical group.
The final independent predictor was the NYHA score post-PMV. The NYHA classification at three months post-PMV has been shown to be a potent predictor of long-term outcome, independent of other variables [7]. This study has shown a statistically significant difference between patients undergoing surgery after PMV and those not requiring surgery in terms of NYHA score post-PMV. Although both groups experienced a decrease in NYHA scores after PMV, the nonsurgical group went from NYHA class 3 to NYHA class 1, whereas the surgical group moved from NYHA class 3 to NYHA class 2, probably again related to some worsening of mitral regurgitation from the PMV.
Importantly, the results of this study indicated that the number of balloon dilations was not a predictor of cardiac surgery after PMV. Even though the surgical group did have more dilations on average, this did not reach statistical significance. Although increased number of dilations may increase the post-PMV MR, this has no independent bearing on the need for surgery.
Within the surgical group, the majority of patients underwent mitral valve replacement rather than repair if they needed surgery post-PMV. While this is unusual given the relatively younger age group of these patients than would normally undergo mitral valve surgery (56 ± 14 years at time of surgery), most if not all would have had a severely deformed valve displaying features of previous PMV, namely torn leaflets and commissures, which would have made valve repair a technically more difficult undertaking.
Finally, most of the patients undergoing mitral valve replacement had a mechanical device inserted rather than a bioprosthesis. This probably related to two factors. First, again given the relatively young age of our study group, inserting a mechanical valve would avoid future operations in this age bracket. Second, a large proportion of these patients were already in atrial fibrillation and on warfarin, so a decision on life-long anticoagulation for mechanical valves would have been easier to make.
In conclusion, while PMV is a safe and effective procedure for the treatment of rheumatic MS, surgery after PMV is not uncommon. Independent predictors for the need to undergo surgery after PMV include the presence of MR before and after PMV, the echo score before PMV, the M gradient after PMV, and the NYHA score at first follow-up after PMV. Further study is needed to determine what combination of events or variables may lead to an increased risk of surgery after PMV, and whether or not these can be flagged for possible early surgical intervention or even surgery in the first instance to avoid any other morbidity associated with the PMV.
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Online Discussion Forum |
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Once the article selected for discussion is published in the online version of The Annals, we will post a notice on the CTSNet home page (http://www.ctsnet.org) with a FREE LINK to the full-text article. Readers wishing to comment can post their own commentary in the discussion forum for that article, which will be informally moderated by The Annals Internet Editor. We encourage all surgeons to participate in this interesting exchange and to avail themselves of the other valuable features of the CTSNet Discussion Forum and Web site.
For September, the article chosen for discussion under the Pediatric Cardiac Dilemma Section of the Discussion forum is:
Is the Ross Operation Still an Acceptable Option in Children and Adolescents?
Jürgen O. Böhm, MD, Cornelius A. Botha, FCS(SA), Alexander Horke, MD, Wolfgang Hemmer, MD, Detlef Roser, MD, Gunnar Blumenstock, MD, Frank Uhlemann, MD, and Joachim-Gerd Rein, MD
Tom R. Karl, MD
The Annals Internet Editor
UCSF Children's Hospital
Pediatric Cardiac Surgical Unit
505 Parnassus Ave, Room S-549
San Francisco, CA 94143-0118
Phone: (415) 476-3501
Fax: (212) 202-3622
e-mail: karlt{at}surgery.ucsf.edu
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This article has been cited by other articles:
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  B. Jungwirth and G. B. Mackensen Real-Time 3-Dimensional Echocardiography in the Operating Room Seminars in Cardiothoracic and Vascular Anesthesia, December 1, 2008; 12(4): 248 - 264. [Abstract] [PDF]
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 S. H. Rahimtoola The Year in Valvular Heart Disease. J. Am. Coll. Cardiol., February 19, 2008; 51(7): 760 - 770. [Full Text] [PDF]
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