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J Thorac Cardiovasc Surg 2002;124:911-917
© 2002 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease (ACD) |
From the Department of Cardiothoracic Surgery, Papworth Hospital,a MRC Biostatistics Unit,b Cambridge, United Kingdom, and the Division of Cardiology, Department of Internal Medicine, University of Witwatersrand and Johannesburg Hospital, Johannesburg, South Africa.c
Received for publication Nov 6, 2001. Revisions requested Dec 18, 2001; revisions received March 7, 2002. Accepted for publication March 26, 2002. Address for reprints: Eric Lim, MB, ChB, MRCS, Department of Cardiothoracic Surgery, Royal Brompton Hospital, Sydney St, London SW3 6NP, United Kingdom (E-mail: ericlim2{at}hotmail.com).
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Abstract |
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statistic was used to express agreement. of 0.43 relative to echocardiography. Electrocardiographic criteria for left ventricular hypertrophy were superior, with a complete specificity of 100% but a low sensitivity of 15%. Agreement within 7 grades of severity was moderate, with a weighted value of 0.42. |
Introduction |
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1 Unlike valve replacement, surgical correction with repair techniques reconstructs and preserves the innate architecture of the mitral apparatus. Perfect competence is not always achievable, and trivial to mild residual regurgitation is present in 63% to 64% of patients after this procedure. 2,3
Long-term follow up studies now reveal that residual regurgitation after mitral repair is an independent risk for late reoperation. 4 Therefore, the ability to accurately assess and quantify the degree of residual regurgitation is important both in the postoperative management and in the decision as to the intensity of subsequent reviews. Considerable controversy exists regarding the optimal method of follow-up, and no consensus has been achieved in favor of either clinical examination alone or periodic echocardiography. 5 The aim of this study was to determine the risk factors and compare the accuracy of clinical examination with that of transthoracic echocardiography in assessing the presence and severity of residual postoperative mitral regurgitation.
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Methods |
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For each patient, clinical and transthoracic echocardiographic assessment was performed blind and independently during the same visit. The results were compared to determine the accuracy of clinical examination in detecting mitral regurgitation and the ability to discern between grades of regurgitation.
The cause of valvular regurgitation was determined by histopathologic examination of operatively obtained valve specimens. Operative details and evaluation of valve disease were obtained by scrutiny of individual patient operation notes.
Clinical assessment
Assessment consisted of history, clinical examination and electrocardiography (ECG). On admission, the ECG was recorded for each patient before interview and clinical examination undertaken by a cardiologist with a particular interest in and experience with mitral valve disease (J.B.B.). Mitral regurgitation was documented and graded in 7 categories (none, trivial, mild, mild to moderate, moderate, moderate to severe, and severe) according to previously published criteria. 6 Clinical criteria used to grade the severity of regurgitation are presented in Table 1. The presence of left ventricular hypertrophy (LVH) was determined according to the voltage criteria of Sokolow and Lyon (SV1 + RV5/6 >38 mm), and strain pattern was defined as downwardly sloping convex ST segments with inverted asymmetric T-wave inversion opposite to the QRS axis in V5/6. 7
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Each of the Doppler techniques was used to assess the overall grade of mitral regurgitation. Color flow Doppler was used to assess the width at the origin of the regurgitant jet, with broader jets indicating progressive degrees of regurgitation. The direction of the jet was determined from the color flow signal. Continuous-wave Doppler was used to grade the amount of regurgitation, with care being taken to align the continuous-wave beam with the strongest received signal. The brightness of the mitral regurgitation envelope was visually compared with that of the mitral valve forward flow envelope, and envelopes equal to or approaching the brightness of the mitral valve forward flow were taken to indicate severe mitral regurgitation. Incomplete envelopes and complete but pale envelopes were interpreted as mild mitral regurgitation. Pulsed-wave Doppler was used to track the regurgitant jet. The echocardiographic criteria used to grade the severity of regurgitation are presented in Table 2.
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statistic was used to determine the degree of agreement beyond chance in comparing the accuracy of clinical examination compared with echocardiography. A weighted was also computed to express the degree of agreement between the presence and severity of regurgitation in 7 grades ranging from 0 to 6. Interpretation of the statistic was based on the guidelines of Landis and Koch. 8 Sensitivities and specificities were calculated with 95% confidence intervals (CIs) for each of the diagnostic modalities reported. |
Results |
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and 4.
Determinants of postoperative echocardiographic regurgitation
Freedom from residual regurgitation (± SE) at 1 and 5 years were 91.5% ± 1.7% and 47.5% ± 3.2%, respectively. Factors significantly associated with postoperative regurgitation were preoperative left ventricular function (P = .006), preoperative atrial fibrillation (P = .05), age (P = .01), and chordal repair and replacement procedures (P = .02). Preoperative LVH approached traditional levels of significance (P = .07). In the final model, only preoperative left ventricular function (P = .04), age (P = .01), and chordal procedures (P = .006) remained significant. The odds ratio comparing echocardiographic detection of regurgitation with moderate to good left ventricular function was 2.3 (95% CI 1.1-4.8); that for poor to good function was 2.9 (95% CI 0.8-10.0). The odds ratio per additional year of age was 1.0 (95% CI 1.0-1.1), and the odds ratio comparing those with chordal procedures with those without was 8.7 (95% CI 1.1-68.0). The wide confidence interval reflects the high proportion of patients with chordal procedures with residual regurgitation (n = 27/28).
Comparison of modalities to detect mitral regurgitation
Most patients were in New York Heart Association functional class I or II (96.1% of patients without regurgitation compared with 94.4% of patients with regurgitation; P = .62). Of the 113 patients in New York Heart Association functional class I on follow-up, 72.6% (n = 82/113) had evidence of regurgitation on echocardiography. This included 6.2% (n = 7/113) of patients with regurgitation of moderate severity.
A total of 67.0% of patients had a murmur detectable by clinical examination. This was reasonably accurate, with a sensitivity of 78% (95% CI 72%-83%) and a specificity of 77% (95% CI 64%-89%). The calculated statistic for this observation was 0.42 (95% CI 0.31-0.54), which indicates moderate agreement with echocardiography. The positive predictive value was 93% (95% CI 89%-96%), the negative predictive value was 45% (95% CI 35%-55%), the positive likelihood ratio was 3.3 (95% CI 2.0-5.4), and the negative likelihood ratio was 0.30 (95% CI 0.22-0.40).
Electrocardiographic criteria for LVH were far superior in this respect, providing complete specificity at 100% (95% CI 92%-100%) but low sensitivity of 15% (95% CI 10%-20%) when correlated with echocardiography. The positive predictive value was 100% (95% CI 89%-100%), and the negative predictive value was 22% (95% CI 17%-28%). Strain pattern on electrocardiography provided another useful means of identifying mitral regurgitation, with a specificity of 87% (95% CI 74%-95%) but a low sensitivity of 29% (95% CI 23%-35%).
Comparison of modalities to assess the severity of mitral regurgitation
Differentiation among the 7 grades of regurgitation through clinical examination did not correlate well with echocardiographic results. The calculated for this observation was 0.24 (95% CI 0.17-0.32). When weighted the agreement was moderate, with a corrected value of 0.42 (95% CI 0.34-0.49). Of greater clinical relevance, however, is the ability to accurately differentiate between trivial to mild and moderate to severe regurgitation. According to this classification, clinical assessment relative to echocardiography has improved specificity of 88% (95% CI 84%-93%) but a poorer sensitivity of 54% (95% CI 34%-69%) than the presence or absence of regurgitation. The degree of accuracy expressed as for this was 0.36 (95% CI 0.19-0.50)
With the more broadly defined groups for severity of regurgitation, electrocardiographic criteria for LVH had a specificity of 91% (95% CI 87%-95%) and a sensitivity of 38% (95% CI 20%-56%) in this respect. ECG criteria for strain pattern showed specificity of 78% (95% CI 72%-83%) but a sensitivity of 52% (95% CI 34%-70%).
A summary of the comparison between clinical assessment and echocardiography was abbreviated to 4 grades, ranging from none, mild, moderate, to severe regurgitation. This is presented in Table 5.
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Discussion |
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4 The detected proportion of residual regurgitation was 69% in our series, consistent with other centers on midterm transthoracic echocardiographic follow-up. 2,3 Most, however, have clinically insignificant trivial regurgitation (59%, n = 107/182). Although this finding does not undermine the outstanding results of mitral repair in general, residual regurgitation has been reported as an independent risk for reoperation. 4 The hazard phase for reoperation tends to occur in two time frames, with the initial peak during the first year followed by a slow and gradual increase in risk with time. 9 Most failures during the initial peak are presumably detected and addressed early, so the need for highly predictive testing should decrease with time. The hazard function for residual regurgitation on the other hand, occurs as a gradual risk that increases steadily after the third year (Figure 1, B). The independent risk factors were impaired preoperative left ventricular function, increased age, and chordal repair or replacement. Among the patients undergoing chordal procedures, there was no difference between the proportions of patients with anterior (57.1%, n = 16/28) and posterior (50.0%, 14/28, P = .25) chordal disease.
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10 Although Doppler echocardiography has been considered to be more accurate than auscultation, clinical assessment has the advantage of being inexpensive and repeatable. 11 The central issue, however, is whether clinical examination is as reliable as echocardiography.
Our results indicate that the agreement on the presence of mitral regurgitation between clinical examination and echocardiography alone is moderate. This may be a reflection of differences in the accuracy of clinical assessment and echocardiography in the detection of mitral regurgitation. Although echocardiography has been reported to be highly accurate 11 when judged by cardiac catheterization, regurgitant jets may be localized. It is known that inability to position the sample volume in the jet on echocardiography can result in failure to detect regurgitation. 12 Under these circumstances, an experienced clinical examiner would argue that regurgitation is present when a murmur is detected, even though no regurgitant jet may be seen on echocardiography.
We have discovered that ECG is able to effectively augment the diagnostic process with 100% specificity to rule in the diagnosis of residual mitral regurgitation in the presence of LVH. All patients in our series with postoperative LVH also had evidence of residual regurgitation (11.4%, n = 30/264).
Clinical implications
The risk of residual regurgitation after mitral repair escalates after the third year. Where possible, leaflet prolapse should be corrected with procedures other than chordal repair or replacement. Symptoms alone cannot be relied on to guide further management, because regurgitation was present on echocardiography in most symptom-free patients on follow-up. Older patients with more severe left ventricular impairment are at increased risk. Although clinical assessment alone had moderate agreement with echocardiography, when augmented with ECG evidence of LVH it had complete specificity for residual regurgitation. Therefore, clinical assessment and ECG are all that is necessary to detect the presence of regurgitation after mitral repair. Clinical assessment was limited in the ability to discriminate the grades of severity, however, so a combined clinical approach with periodic echocardiography should be used when clinical regurgitation is detected.
Study limitations
A cardiologist with extensive experience and interest in mitral valve disease performed the clinical assessment for our study, and not all clinicians may achieve a similar standard. The quality of echocardiography may also vary with operator experience. However, the level of agreement ( 0.30-0.48) is consistent with that found for other cardiologists in the detection of systolic murmurs in general. 13 Reproducibility of the techniques used in this study may not be exact, because an inherent degree of subjectivity will exist when discriminating the grades of severity of mitral regurgitation for both clinical examination and echocardiography.
Freedom from regurgitation in Figure 1, A, commences on the assumption that all patients were initially free of regurgitation after the operation. This is clearly not the case in practice, and readers are cautioned to interpret the freedom from regurgitation as a function of time to detection rather than the absence of regurgitation per se.
The inclusion of 15 patients (5.7%, n = 15/264) with concomitant valve procedures may have prejudiced the clinical examination. However, the decision to include these patients in our study was undertaken to critically evaluate clinical assessment in circumstances reflective of the heterogeneous population encountered in practice.
Conclusions
Continual surveillance for residual regurgitation is recommended after mitral repair, because the hazard function increases steadily after the third year. Increased age, poor ventricular function, and chordal repair or replacement procedures are independent risk factors for residual regurgitation. Clinical assessment (augmented with ECG evidence of LVH) is excellent in detecting the presence of mitral regurgitation. The two modalities, however, have a less powerful correlation in grading the severity of regurgitation.
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