Mitral regurgitation (MR) is common in ischemic heart disease and contributes to symptoms and mortality. This report compares the results of baseline transesophageal echocardiography (TEE) and transthoracic echocardiography (TTE) imaging of the mechanism and severity of functional MR in patients with ischemic cardiomyopathy in the Surgical Treatment for Ischemic Heart Failure (STICH) trial. Independent core laboratories measured both TTE and TEE images on 196 STICH participants. Common measurements to both models included MR grade, mitral valve tenting height and tenting area, and mitral annular diameter. For each parameter, correlations were assessed using Spearman rank correlation coefficients. A modest correlation was present between TEE and TTE for overall MR grade (n = 176, r = 0.52). For mechanism of MR, modest correlations were present for long-axis tenting height (n = 152, r = 0.35), tenting area (n = 128, r = 0.27), and long-axis mitral annulus diameter (n = 123, r = 0.41). For each measurement, there was significant scatter. Potential explanations for the scatter include different orientation of the imaging planes between TEE and TTE, a mean temporal delay of 6 days between TEE and TTE, and statistically significant differences in heart rate and blood pressure and weight between studies. In conclusion, TEE and TTE measurements of MR mechanism and severity correlate only modestly with enough scatter in the data that they are not interchangeable.
In patients with heart failure due to ischemic cardiomyopathy, functional mitral regurgitation (MR) is common and has been shown to be associated with mortality. The mechanism of functional MR is restricted leaflet closure by a combination of outward and apical tethering due to left ventricular (LV) dilation and/or regional wall motion abnormalities, reduced systolic closing force, and/or annular dilation. In a substudy of the Surgical Treatment for Ischemic Heart Failure (STICH) trial, multiple measurements of MR mechanism, including leaflet tenting, annulus size, and LV end-systolic volume index, predicted MR severity. This study was performed to compare measurements of MR mechanism and severity by transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) in patients enrolled in the STICH Trial.
Methods
Of 2,136 patients enrolled in STICH, 2,006 (94%) had TTE studies measured by an independent Echocardiography Core Laboratory. A TEE substudy enrolled 215 patients, of whom, 196 also had measureable TTE studies assessed by an independent TEE Core Laboratory.
Detailed echocardiographic measurements and results have been reported previously for both TTE and TEE findings in STICH. All TEE studies were performed under conscious sedation; none were intraoperative. This report compares identical measurements of the mechanism and severity of MR by both TTE and TEE in the same patients. Specific measurements of MR mechanism that were common to TTE and TEE were mitral valve tenting height, mitral valve tenting area, and mitral annulus anteroposterior diameter, all performed in long-axis views. Specific measurements of MR severity were effective regurgitant orifice area (EROA) by the proximal isovelocity surface area method and overall MR grade which integrated multiple parameters, including jet size and eccentricity, EROA, mitral filling pattern, and pulmonary venous flow pattern. Because severe MR was rare, patients with moderate or severe MR were combined, giving 3 categories: none/trace, mild, and moderate/severe MR.
Data for 196 patients included in this study were descriptively summarized using the mean and standard deviation for the continuous variables and frequencies and percentages for the categorical variables. The distributions of continuous variables for the 196 patients and other STICH participants were compared using the Wilcoxon rank-sum test, and categorical variables were compared using the Pearson chi-square tests. Spearman rank correlation coefficients were used to assess the strength of association between TEE and TTE measurements on MR severity and MR mechanism. One-sample t tests were used to evaluate whether the mean differences of TEE and TTE measurements were significantly different from zero. All analyses were performed using SAS statistical software, version 9.4 (SAS Institute Inc., Cary, North Carolina).
Results
Table 1 lists the demographic and clinical characteristics of the patients in this MR substudy compared to the remainder of the STICH main trial population. There was a regional difference, with our patients being more likely white (90.8% vs 76.8%) and European (83.7% vs 53.6%; p <0.0001 for both). Our patients had slightly more previous myocardial infarctions (87.2% vs 81.0%, p = 0.0311) and less chronic kidney disease (3.6% vs 8.5%, p = 0.0154). New York Heart Association heart failure class was less severe (p <0.0001), but LV volumes were larger (LV end-diastolic volume index 125.2 ± 42.6 vs 116.6 ± 40.6 ml/m 2 , p = 0.0099; LV end-systolic volume index 90.3 ± 34.3 vs 83.2 ± 33.7 ml/m 2 , p = 0.0031). MR severity (as graded by the sites) tended to be slightly worse in the patients in MR substudy (moderate/severe MR in 28.8% vs 16.9%, p = 0.0002).
| Parameter | Excluded (n=1940) | Included (n=196) | P value |
|---|---|---|---|
| Age (years) | 61.0 ± 9.5 | 58.9 ± 9.9 | 0.1690 |
| Men | 1680 (86.6%) | 170 (86.7%) | 0.9573 |
| Region | <0.0001 | ||
| USA | 292 (15.1%) | 15 (7.7%) | |
| Canada | 257 (13.2%) | 8 (4.1%) | |
| Europe | 1040 (53.6%) | 164 (83.7%) | |
| Asia | 278 (14.3%) | 9 (4.6%) | |
| South America | 73 (3.8%) | 0 | |
| White | 1490 (76.8%) | 178 (90.8%) | <0.0001 |
| Body Mass Index (kg/m 2 ) | 27.4 ± 4.7 | 27.2 ± 3.9 | 0.7799 |
| Myocardial infarction | 1571 (81%) | 171 (87.2%) | 0.0311 |
| Diabetes | 738 (38%) | 61 (31.1%) | 0.0564 |
| Stroke | 125 (6.4%) | 16 (8.2%) | 0.3554 |
| Hypertension | 1160 (59.8%) | 116 (59.2%) | 0.8682 |
| Hyperlipidemia | 1257 (64.9%) | 135 (68.9%) | 0.2683 |
| Current smoker | 406 (20.9%) | 39 (19.9%) | 0.7325 |
| Peripheral vascular disease | 297 (15.3%) | 24 (12.2%) | 0.2526 |
| Chronic kidney disease | 165 (8.5%) | 7 (3.6%) | 0.0154 |
| Atrial fibrillation | 240 (12.4%) | 20 (10.2%) | 0.3765 |
| Previous Coronary Artery Bypass | 58 (3%) | 2 (1%) | 0.1118 |
| Previous Percutaneous Coronary Intervention | 297 (15.3%) | 35 (17.9%) | 0.3481 |
| Current NYHA heart failure class | <0.0001 | ||
| I | 177 (9.1%) | 40 (20.4%) | |
| II | 913 (47.1%) | 101 (51.5%) | |
| III | 768 (39.6%) | 51 (26%) | |
| IV | 82 (4.2%) | 4 (2%) | |
| Left ventricular ejection fraction | 28.4 ± 8.8% | 27.1 ± 8.5% | 0.0604 |
| Left ventricular end-diastolic volume index (ml/m 2 ) | 116.6 ± 40.6 | 125.2 ± 42.6 | 0.0099 |
| Left ventricular end-systolic volume index (ml/m 2 ) | 83.2 ± 33.7 | 90.3 ± 34.4 | 0.0031 |
| Mitral Regurgitation ∗ | 0.0002 | ||
| None/trace | 711 (36.8%) | 57 (29.4%) | |
| Mild | 892 (46.2%) | 81 (41.8%) | |
| Moderate | 278 (14.4%) | 35 (18%) | |
| Severe | 49 (2.5%) | 21 (10.8%) |
Figure 1 displays the association of TEE and TTE measurements on MR grade (n = 176), tenting height (n = 152), tenting area (n = 128), and mitral annulus anteroposterior diameter (n = 123) on scatterplots. Only modest association between TEE and TTE measurements was observed on the scatterplots with the Spearman rank correlation coefficients ranged from 0.27 to 0.51, with considerable scatter present on the plots.
Furthermore, it was found the mean difference of all 4 TEE and TTE measures was statistically significantly different from zero by 1-sample t tests ( Table 2 ). TEE measurements were significantly lower than TTE measurements on MR grade ( t = −5.75, p <0.001), tenting area ( t = −7.44, p <0.001), and mitral annulus anteroposterior diameter ( t = −9.68, p <0.001), whereas TEE measurement on tenting height was significantly greater than TTE measurement ( t = 2.11, p = 0.037). EROA was not analyzed because only 16 patients had EROA by both TEE and TTE.
| Variables | N | TEE Measure (Mean ± Std) | TTE Measure (Mean ± Std) | Mean Difference (Mean ± Std) | 95% Confidence Limit for Mean Difference | 1-Sample T-test on Mean Difference | |
|---|---|---|---|---|---|---|---|
| T-value | P-value | ||||||
| Mitral Regurgitation Grade | 176 | 0.91 (0.70) | 1.28 (0.96) | -0.37 (0.85) | (-0.50, -0.24) | -5.75 | <0.0001 |
| MV Tenting Area (cm 2 ) | 128 | 1.88 (0.61) | 2.70 (1.28) | -0.82 (1.24) | (-1.03, -0.60) | -7.44 | <0.0001 |
| MV Tenting Height (cm) | 152 | 0.81 (0.31) | 0.75 (0.31) | 0.06 (0.37) | (0.01, 0.12) | 2.11 | 0.0368 |
| Long-axis Annulus Diameter (cm) | 123 | 3.32 (0.38) | 3.75 (0.51) | -0.42 (0.49) | (-0.51, -0.34) | -9.68 | <0.0001 |
| Systolic Blood Pressure (mmHg) | 162 | 118.64 (17.47) | 115.53 (16.66) | 3.10 (16.41) | (0.56, 5.65) | 2.41 | 0.0172 |
| Diastolic Blood Pressure (mmHg) | 163 | 75.29 (10.89) | 73.10 (9.42) | 2.19 (11.45) | (0.42, 3.96) | 2.44 | 0.0157 |
| Heart Rate (beats/minute) | 167 | 75.37 (12.56) | 71.26 (12.04) | 4.11 (12.00) | (2.27, 5.94) | 4.42 | <0.0001 |
| Weight (lbs) | 169 | 172.97 (28.77) | 171.71 (28.68) | 1.26 (6.48) | (0.28, 2.25) | 2.53 | 0.0124 |
| Height (inch) | 169 | 67.12 (3.09) | 67.06 (3.16) | 0.06 (1.19) | (-0.12, 0.23) | 0.61 | 0.5394 |
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