Pulmonary hypertension (PH) is a common sequela of degenerative mitral valve disease, but the regression of PH after mitral surgery is often incomplete. We sought to identify the preoperative risk factors for residual PH after mitral valve repair and its effect on the clinical outcome. The outcomes in 71 patients with preoperative PH (mean pulmonary arterial pressure ≥25 mm Hg) were compared according to the presence or absence of residual PH 24 hours after mitral valve surgery. Of 71 patients, 33 (46%) had residual PH. The remainder experienced significant reductions in the mean pulmonary arterial pressure without changes in pulmonary vascular resistance. Patients with residual PH had significantly elevated postoperative pulmonary vascular resistance (despite a significant decrease from the preoperative baseline) compared to those without residual PH. Residual PH was an independent risk factor for postoperative morbidity, mortality, and a prolonged intensive care unit stay (odds ratio 4.0, 95% confidence interval 1.2 to 13.1, p = 0.02), independent of the preoperative mean pulmonary arterial pressure. A decreased left ventricular ejection fraction (odds ratio 0.9, 95% confidence interval 0.8 to 1.0, p = 0.007) and fibroelastic deficiency (odds ratio 3.6, 95% confidence interval 1.1 to 11.8, p = 0.03) were independent predictors of residual PH. In conclusion, residual PH is a clinically important entity common after mitral valve repair for degenerative disease and is associated with clinical variables that aid in the preoperative prediction of at-risk patients.
The main objectives of the present study were to define preoperative risk factors that may be used to identify those patients more likely to experience residual elevation in pulmonary artery pressure after mitral repair for degenerative mitral valve disease, and to determine the prognostic effect of residual pulmonary hypertension (PH).
Methods
We retrospectively analyzed the data from patients with preoperative PH who had undergone mitral valve surgery for pure mitral regurgitation at the Mount Sinai Medical Center (New York, New York) from September 2005 to July 2008. Preoperative PH was defined as either a mean pulmonary arterial pressure (PAP) of ≥25 mm Hg by way of right heart catheterization or evidence of at least moderate PH on the preoperative echocardiogram. The exclusion criteria included concomitant aortic valve surgery, nondegenerative mitral valve disease, planned ventricular assist device implantation, death within 24 hours of surgery, and incomplete postoperative pulmonary artery catheterization data. Degenerative mitral valve disease was defined echocardiographically and confirmed intraoperatively as single or multisegment leaflet prolapse resulting from chordal elongation or rupture and caused by myxomatous valve disease. Patients with small valves and single-segment prolapse were classified as having fibroelastic deficiency, and patients with large valves and multisegment prolapse were classified as having Barlow’s disease. During the study period, 431 patients underwent mitral valve surgery with or without concomitant tricuspid repair and coronary artery bypass grafting. A total of 71 patients met the inclusion and exclusion criteria, with a mean age of 65 ± 12 years. Of the 71 patients, 44% were women. The data from these patients were collected from the prospective clinical databases and chart review. The local institutional review board approved the protocol, and the study adhered to the Health Insurance Portability and Accountability Act regulations and ethical guidelines of the 1975 Declaration of Helsinki.
All patients underwent preoperative echocardiography. The systolic PAP was derived by adding the right ventricular systolic pressure to the estimated right atrial pressure. The right ventricular systolic pressure was estimated from the peak velocity of tricuspid regurgitation and the simplified Bernoulli equation (ΔP = 4V ). The right atrial pressure was estimated according to the hepatic vein flow, right atrial size, or the degree of inspiratory collapse of the inferior vena cava.
Preoperative right heart catheterization was performed in 44 patients (59%). Cardiac output was determined using the Fick equation, assuming an oxygen consumption at rest of 125 ml/min/m 2 and converted to the cardiac index. Postoperative hemodynamic data were obtained for ≤24 hours after surgery.
Aortocaval bypass was instituted using a median sternotomy, hemisternotomy, or right thoracotomy, and the mitral valve was approached through a left atriotomy in Sondegaard’s groove. Myocardial preservation was achieved using intermittent cold blood cardioplegia given anterogradely and retrogradely. The mitral valve was systematically evaluated using transesophageal echocardiography and then under direct vision. Mitral valve repair was performed according to Carpentier’s reconstructive principles. Concomitant tricuspid valve annuloplasty was performed for patients with moderate to severe PH with significant annular dilation or tricuspid regurgitation of at least moderate severity.
The patients were categorized into 1 of 2 groups according to the absence or presence of residual PH (defined as a mean PAP of ≥25 mm Hg at rest 24 hours after surgery, measured using a pulmonary artery catheter). The secondary end points focused on the effect of residual PH on postoperative mortality, major complications (e.g., respiratory failure, renal failure, deep sternal wound infection, bleeding requiring reoperation, stroke, and gastrointestinal complications), length of the intensive care unit stay, duration of mechanical ventilation, and duration of inotropic support. Respiratory failure was defined as ventilator therapy for >72 hours, the need for reintubation, or the need for tracheostomy. Renal failure was classified as serum creatinine >2.5 mg/dl for ≥7 days postoperatively or a new dialysis requirement. Stroke was defined as a new, permanent neurologic deficit of cerebrovascular cause. Gastrointestinal complications included upper or lower gastrointestinal bleeding and the need for laparotomy. Survival data were obtained by cross-referencing the patient Social Security numbers with the Web-based Social Security death index.
Normally distributed continuous variables are expressed as the mean ± SD and non-normally distributed variables as the median with the interquartile range. Categorical variables are presented as proportions. Differences between groups were assessed using the chi-square test or Fischer’s exact test for categorical variables, the independent 2-tailed Student t test for normally distributed continuous variables, and the Mann-Whitney U test for non-normally distributed continuous variables. A univariate logistic regression analysis was performed, including all preoperative candidate variables in Tables 1 and 2 (mean PAP and pulmonary vascular resistance [PVR]), to evaluate the potential risk factors for residual PH. Variables with p <0.15 were included in a stepwise multivariate model. The predicted probabilities for residual PH were calculated for patients in the study population, and receiver operating characteristic curves were generated. A c -statistic of >0.7 was considered accurate. Midterm survival was evaluated using Kaplan-Meier survival analysis, and the groups were compared using log-rank testing. A Cox proportional hazard regression analysis was performed to determine the independent predictors of reduced survival. The results of the regression analyses are presented as the odds ratios (ORs) or hazard ratios, with the corresponding 95% confidence intervals (CIs). All tests were 2-tailed, and p <0.05 was considered statistically significant. The statistical analysis was performed using the Statistical Package for Social Sciences for Macintosh, version 18.0 (SPSS, Chicago, Illinois).
| Variable | Residual PH | p Value | |
|---|---|---|---|
| No (n = 38) | Yes (n = 33) | ||
| Preoperative data | |||
| Age (years) | 63 ± 13 | 68 ± 11 | 0.125 |
| Women | 20 (53%) | 11 (33%) | 0.102 |
| Body mass index (kg/m 2 ) | 26 ± 10 | 27 ± 3 | 0.587 |
| Body mass index >30 kg/m 2 | 3 (8%) | 4 (12%) | 0.697 |
| Left ventricular ejection fraction (%) | 61 ± 7 | 56 ± 9 | 0.007 |
| Left ventricular ejection fraction ≤50% | 4 (12%) | 8 (26%) | 0.145 |
| New York Heart Association class III-IV | 12 (32%) | 12 (36%) | 0.671 |
| Previous myocardial infarction | 1 (3%) | 1 (3%) | 1.000 |
| Previous stroke | 1 (3%) | 2 (6%) | 0.594 |
| Systemic hypertension ⁎ | 17 (45%) | 22 (68%) | 0.064 |
| Diabetes mellitus | 1 (3%) | 2 (6%) | 0.474 |
| Peripheral vascular disease | 1 (3%) | 1 (3%) | 1.000 |
| Chronic obstructive airways disease | 2 (5%) | 0 (0%) | 0.495 |
| Asthma | 3 (8%) | 1 (3%) | 0.618 |
| Sleep apnea | 1 (3%) | 0 (0%) | 1.000 |
| Renal failure | 0 (0%) | 0 (0%) | — |
| Atrial fibrillation | 7 (18%) | 14 (42%) | 0.027 |
| Reoperation | 1 (3%) | 1 (3%) | 1.000 |
| Barlow’s disease | 16 (42%) | 8 (24%) | 0.113 |
| Logistic EuroSCORE | 0.760 | ||
| Median | 4 | 5 | |
| Interquartile range | 3–12 | 3–10 | |
| Echocardiographic data | |||
| Mitral regurgitation | 0.549 | ||
| Moderate | 0 | 1 (3%) | |
| Severe | 38 (100%) | 32 (97%) | |
| Right ventricular systolic pressure (mm Hg) | 45 ± 10 | 53 ± 13 | 0.023 |
| Left ventricular end-diastolic diameter (cm) | 5.7 ± 0.7 | 5.5 ± 0.8 | 0.352 |
| Operative data | |||
| Mitral repair | 38 (100%) | 33 (100%) | — |
| Tricuspid repair | 34 (90%) | 28 (85%) | 0.724 |
| Coronary artery bypass grafting | 7 (18%) | 8 (24%) | 0.549 |
| Maze ablation | 8 (21%) | 13 (39%) | 0.091 |
| Patent foramen ovale closure | 2 (5%) | 1 (3%) | 1.000 |
| Cardiopulmonary bypass time (min) | 183 ± 63 | 194 ± 57 | 0.442 |
| Cross-clamp time (min) | 145 ± 43 | 155 ± 51 | 0.381 |
| Intra-aortic balloon pump placement | 3 (8%) | 5 (15%) | 0.459 |
⁎ Defined by one of the following: documented history of hypertension diagnosed and treated with medication, diet, and/or exercise; previous documentation of blood pressure >140 mm Hg systolic or 90 mm Hg diastolic for patients without diabetes or chronic kidney disease, or previous documentation of blood pressure >130 mm Hg systolic or 80 mm Hg diastolic on ≥2 occasions for patients with diabetes or chronic kidney disease; and current pharmacological therapy to control hypertension.
| Variable | Preoperative | Postoperative | p Value |
|---|---|---|---|
| No residual pulmonary hypertension | |||
| Mean arterial pressure (mm Hg) | 84 ± 11 | 77 ± 11 | 0.109 |
| Mean pulmonary artery pressure (mm Hg) | 31 ± 4 | 21 ± 2 ⁎ | <0.001 |
| Systolic pulmonary artery pressure (mm Hg) | 45 ± 5 | 30 ± 4 ⁎ | <0.001 |
| Diastolic pulmonary artery pressure (mm Hg) | 21 ± 5 | 14 ± 3 ⁎ | <0.001 |
| Central venous pressure (mm Hg) | 8 ± 3 | 9 ± 3 ⁎ | 0.620 |
| Cardiac index (L/min/m 2 ) | 2.4 ± 0.6 | 2.7 ± 0.6 | 0.102 |
| Pulmonary vascular resistance (dyn × s × cm −5 ) | 117 ± 43 | 114 ± 46 † | 0.838 |
| Residual pulmonary hypertension | |||
| Mean arterial pressure (mm Hg) | 92 ± 15 | 79 ± 9 | 0.003 |
| Mean pulmonary artery pressure (mm Hg) | 35 ± 8 | 30 ± 4 ⁎ | 0.015 |
| Systolic pulmonary artery pressure (mm Hg) | 54 ± 12 | 42 ± 6 ⁎ | <0.001 |
| Diastolic pulmonary artery pressure (mm Hg) | 23 ± 9 | 23 ± 3 ⁎ | 0.691 |
| Central venous pressure (mm Hg) | 10 ± 5 | 15 ± 3 ⁎ | <0.001 |
| Cardiac index (L/min/m 2 ) | 2.2 ± 0.5 | 2.6 ± 0.5 | 0.030 |
| Pulmonary vascular resistance (dyn × s × cm −5 ) | 258 ± 156 | 147 ± 54 † | 0.024 |
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