Exercise Pulmonary Hypertension in MR
Abstract & Commentary
By Michael H. Crawford, MD
Source: Magne, J et al. Exercise pulmonary hypertension in asymptomatic degenerative mitral regurgitation. Circulation. 2010;122:33-41.
Current guidelines recommend mitral-valve surgery for severe organic mitral regurgitation in asymptomatic patients if exercise pulmonary hypertension (PASP > 60 mmHg) is demonstrated. However, little is known about the echocardiographic correlates of exercise-induced pulmonary hypertension (PH) or its relationship to symptom-free survival. Thus, these investigators from Belgium studied 78 consecutive asymptomatic patients with moderate or more organic mitral regurgitation (MR) and preserved left ventricular (LV) systolic function, who were referred for exercise echocardiographic testing. Patients with ischemic heart disease, valve stenosis, or concomitant regurgitation, atrial fibrillation, or poor images, were excluded (n = 10). Semi-supine bicycle exercise, with two-minute stages increased by 25W at each stage, was performed with echo Doppler imaging. The results of the exercise study were not shared with the referring physician. Mean follow-up was 19 months (2-56) in 100% of the patients. Resting PH was present in 15% (PASP > 50) and 46% exhibited exercise PH. Multivariate analysis showed that only E/Ea correlated with resting systolic pulmonary artery pressure (SPAP) and measures of MR severity did not. Exercise PH was correlated with age, resting SPAP, and exercise MR severity measures. During follow-up, resting and exercise PH were associated with decreased symptom-free survival over two years compared to medically treated patients (36 vs. 59%, p = 0.04; 35% vs. 75%, p < .0001, respectively). After adjustment for age and sex, resting PH was no longer predictive (HR = 2.1, 95% CI 0.9-4.9, p = 0.08). Exercise PH remained predictive (HR = 2.8, 1.4-5.4, p = 0.002). Receiver operating curve (ROC) analysis showed that the best cut point for predicting reduced symptom-free survival was an exercise SPAP > 56 mmHg (specifically 73%, sensitively 82%, positive predictive value 72%, and negative predictive value 80%). Mitral-valve surgery was performed in 25 patients during follow-up (20 repairs and five replacements) because of symptoms. The authors concluded that an exercise SPAP > 56 mmHg predicts the occurrence of symptoms and is associated with a significantly lower symptom-free survival.
Commentary
Deciding when to recommend surgery for asymptomatic patients with moderately severe-to-severe MR and normal LV function is a challenge. If we knew that all would get a repair, rather than a replacement, it would be easier, but this study confirms that 20% end up with a prosthetic valve. The guidelines recommend surgery for patients if they have a resting SPAP > 50 or an exercise value > 60 mmHg (class IIa, evidence C). Thus, this report is a welcome addition to our knowledge base about these criteria.
In this study, symptom-free survival was reduced if patients had SPAP values roughly above the mean value for this population: rest mean 39, receiver operating curve (ROC) cut-off 36; exercise mean 62, ROC cut-off 56. The guidelines cut points are rest 50 and exercise 60. The exercise value is consistent with the data in this study, but the resting cut point in the guidelines seems high. However, all but one patient with a resting pressure above 50 had exercise PH. So, meeting the guideline's resting cut point of 50 predicts exercise PH. This is not surprising because a major determinant of exercise PH is resting PH. Clearly, a resting value above 50 is an indication for surgery and any value above 40 is a cause for concern.
Since patients with normal resting SPAP may develop exercise PH, exercise echo testing seems to be a good idea for those with moderate-to-severe MR and normal resting SPAP. Exercise PH was frequently observed in this population (46%), which is not surprising, since about 60% had severe MR. Interestingly, MR severity did not predict resting PH, but LV filling pressure estimates did. However, exercise PH was predicted by exercise MR severity. This suggests that, at rest, LV filling pressure is a good indicator of the hemodynamic consequences of MR, and that some patients develop more MR with exercise, which seems important for predicting who will become symptomatic.
The implications of this study are that asymptomatic patients with exercise-induced PH and moderately severe-to-severe MR may benefit from early surgery. Before we jump on this bandwagon, there are a few caveats to this study. First, it is not clear that other causes of PH were excluded. This would certainly be important. Second, only echo Doppler was used to assess pulmonary pressures and right atrial pressure was estimated to be 10 mmHg in all patients at rest and exercise. This is a reasonable assumption, but may not be accurate in everyone. All their patients had mitral valve prolapse, and only 10% had a flail leaflet, so this analysis may not apply to other patient populations with more diverse etiologies of MR and a higher percentage of flail leaflets. At this point, I believe exercise echo Doppler could be useful in borderline cases to sway the decision of whether to recommend surgery, but I am not sure I would use it as the sole criterion.
Current guidelines recommend mitral-valve surgery for severe organic mitral regurgitation in asymptomatic patients if exercise pulmonary hypertension (PASP > 60 mmHg) is demonstrated.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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