Abstract
Aim
The significance of passive stretching of the mitral valve as a contributor to valve opening, after percutaneous transvenous mitral commissurotomy (PTMC), is not known. Our objective was to determine whether any acute reduction in valve area occurs due to recoil of stretched valve structures.
Methods and Results
In a prospective observational study, we evaluated nine patients (age 30.1±8.0 years; median valve score 7) who underwent PTMC. We calculated mitral valve area (MVA) before, immediately after, and at 10 and 30 min after valvotomy. There was no acute reduction in MVA after successful PTMC. But there was a significant increase in MVA at 30 min, from that measured immediately after the procedure (1.8±0.4 to 2.0±0.4 cm 2 ; P =.048). This was attributable to the continuing fall in pulmonary artery wedge (PAW) pressures (17±3 to 15±3 mmHg; P =.003) and transmitral gradients (8±3 to 7±2 mmHg; P =.037).
Conclusion
Passive stretching of the valve apparatus does not play an important role in valve opening after PTMC in young patients with favorable valve morphology.
1
Introduction
Percutaneous transvenous mitral commissurotomy (PTMC) is the treatment of choice for patients with rheumatic mitral stenosis and suitable valve morphology . Excellent short- and long-term results have been reported both with the Inoue and the double-balloon technique . The primary mechanism by which stenosis is relieved after balloon dilatation is by the splitting of fused commissures . In addition, stretching of the valve leaflets and subvalvular apparatus , and fracture of nodular calcium within the leaflets also play a role in determining the final valve area after balloon dilatation. Whereas the splitting of fused commissures and the fracture of leaflet calcium can be expected to produce relatively long-lasting changes in mitral valve area (MVA), the contribution of mechanical stretching of the valve apparatus is likely to be temporary . The magnitude of the immediate gain in valve area due to this passive stretching alone has not been quantified. If passive stretching of the valve leaflets is an important factor, we hypothesized that serial measurements would show a decrease in valve area from that obtained immediately after balloon dilatation. We tested this hypothesis in nine patients undergoing percutaneous balloon mitral valvotomy.
2
Methods
2.1
Patients
Patients were considered for inclusion in the present study if they had critical mitral stenosis (MVA less than 1.0 cm 2 ) and a noncalcific valve considered suitable for PTMC on transthoracic echocardiography (TTE). We excluded patients who had more than mild tricuspid regurgitation (TR) and those with multivalve disease. This was done in order to ensure accurate measurement of cardiac output by the thermodilution method. Patients developing significant mitral regurgitation (MR) following valvotomy were not included. We also excluded patients who were in NYHA Class IV congestive heart failure or atrial fibrillation (AF) with uncontrolled ventricular rate.
2.2
Echocardiography
Mitral valve area was measured on TTE both by planimetry and by the pressure half-time method before and 24 h after PTMC. Transesophageal echocardiography (TEE) was performed only if the left atrial (LA) appendage was not adequately visualized on TTE. The valve was scored as previously described .
2.3
Cardiac catheterization
All patients gave informed consent. Diagnostic right and left heart catheterization and left ventricular (LV) angiography were performed before and after valvotomy. Simultaneous pulmonary artery wedge (PAW) or LA and LV pressures were recorded at 100 mm/s paper speed. The PAW tracing was realigned by about 50 ms so that the V wave peaked immediately before the downstroke of the LV pressure trace. The mean diastolic gradient across the mitral valve was determined by planimetry. Cardiac output was measured by the thermodilution method. Mitral valve area was calculated using the method described by Cohen and Gorlin . Valve area was measured before and immediately after balloon dilatation. Measurements were repeated 10 and 30 min after dilatation.
2.4
Mitral valvotomy
Percutaneous mitral valvotomy with the Inoue balloon was performed using the antegrade transseptal technique [16]. Optimal balloon size was decided according to the patients’ height using the following formula: maximum balloon size (mm)=[patient’s height (cm)/10]+10. The initial balloon size used was generally about 2 mm less than that calculated from the formula. Further increases in balloon size were dictated by the reduction in LA pressure and the diastolic gradient, and were at the discretion of the operator. PTMC was considered successful if there was ≥50% increase in MVA or the valve area increased to ≥1.5 cm 2 and the MR severity was ≤2/4.
2.5
Statistical analysis
The data are presented as mean±S.D. Differences between pre- and postdilatation parameters were assessed using the Wilcoxon signed-rank test. The Spearman rank correlation coefficient was determined to compare the valve areas calculated using the hydraulic formula and that measured by transthoracic 2-D and Doppler echocardiography. A difference was considered statistically significant if the P value was less than .05.
2
Methods
2.1
Patients
Patients were considered for inclusion in the present study if they had critical mitral stenosis (MVA less than 1.0 cm 2 ) and a noncalcific valve considered suitable for PTMC on transthoracic echocardiography (TTE). We excluded patients who had more than mild tricuspid regurgitation (TR) and those with multivalve disease. This was done in order to ensure accurate measurement of cardiac output by the thermodilution method. Patients developing significant mitral regurgitation (MR) following valvotomy were not included. We also excluded patients who were in NYHA Class IV congestive heart failure or atrial fibrillation (AF) with uncontrolled ventricular rate.
2.2
Echocardiography
Mitral valve area was measured on TTE both by planimetry and by the pressure half-time method before and 24 h after PTMC. Transesophageal echocardiography (TEE) was performed only if the left atrial (LA) appendage was not adequately visualized on TTE. The valve was scored as previously described .
2.3
Cardiac catheterization
All patients gave informed consent. Diagnostic right and left heart catheterization and left ventricular (LV) angiography were performed before and after valvotomy. Simultaneous pulmonary artery wedge (PAW) or LA and LV pressures were recorded at 100 mm/s paper speed. The PAW tracing was realigned by about 50 ms so that the V wave peaked immediately before the downstroke of the LV pressure trace. The mean diastolic gradient across the mitral valve was determined by planimetry. Cardiac output was measured by the thermodilution method. Mitral valve area was calculated using the method described by Cohen and Gorlin . Valve area was measured before and immediately after balloon dilatation. Measurements were repeated 10 and 30 min after dilatation.
2.4
Mitral valvotomy
Percutaneous mitral valvotomy with the Inoue balloon was performed using the antegrade transseptal technique [16]. Optimal balloon size was decided according to the patients’ height using the following formula: maximum balloon size (mm)=[patient’s height (cm)/10]+10. The initial balloon size used was generally about 2 mm less than that calculated from the formula. Further increases in balloon size were dictated by the reduction in LA pressure and the diastolic gradient, and were at the discretion of the operator. PTMC was considered successful if there was ≥50% increase in MVA or the valve area increased to ≥1.5 cm 2 and the MR severity was ≤2/4.
2.5
Statistical analysis
The data are presented as mean±S.D. Differences between pre- and postdilatation parameters were assessed using the Wilcoxon signed-rank test. The Spearman rank correlation coefficient was determined to compare the valve areas calculated using the hydraulic formula and that measured by transthoracic 2-D and Doppler echocardiography. A difference was considered statistically significant if the P value was less than .05.
3
Results
Twenty-four patients planned for PTMC using the Inoue balloon catheter were screened. Reasons for exclusion were presence of moderate or greater severity of tricuspid insufficiency (five patients), associated aortic insufficiency (six patients), AF with fast ventricular rate, significant TR, and congestive heart failure (two patients). Two other patients did not provide consent. We studied nine patients who underwent PTMC ( Table 1 ). There were five females and four males. The mean age of the patients was 30.1 years (S.D. 8.0 years; range 18 to 46 years). Two patients were in NYHA Class II and the remaining in Class III. Four patients were in AF. Trivial to mild TR was present in three patients. Two patients had trivial MR. The median echocardiographic score was 7 (range 5 to 9) ( Table 1 ).
| Patient | Age | Sex | Height | Valve score | NYHA Class | CI | PAW | MDG | MVA | PA | Comment |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 35 | M | 168 | 7 | III | 2.8 | 45 | 36.3 | 0.8 | 87 | Mild TR, AF |
| 2 | 30 | F | 150 | 6 | II | 3.0 | 34 | 22.5 | 0.9 | 43 | – |
| 3 | 23 | M | 170 | 5 | III | 3.1 | 36 | 26.4 | 0.9 | 44 | Trivial MR |
| 4 | 28 | F | 144 | 8 | III | 3.3 | 32 | 22.4 | 0.9 | 46 | Trivial TR |
| 5 | 26 | F | 148 | 9 | III | 3.2 | 35 | 28.0 | 0.7 | 50 | Trivial MR, AF |
| 6 | 18 | M | 175 | 7 | II | 3.4 | 31 | 24.3 | 1.0 | 48 | – |
| 7 | 30 | M | 171 | 6 | III | 4.2 | 40 | 37.0 | 1.3 | 60 | Trivial TR |
| 8 | 35 | F | 155 | 8 | III | 3.0 | 22 | 18.0 | 1.0 | 39 | AF |
| 9 | 46 | F | 155 | 9 | III | 2.2 | 32 | 20.3 | 0.7 | 48 | AF |
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