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Background-We have observed that elevated mitral gradients can develop in some patients after mitral valve repair for degenerative mitral regurgitation. Methods and Results-We screened 275 patients who had mitral valve repair involving >1 leaflet scallop between October 2001 and July 2010. Mitral valve hemodynamics were assessed at rest and at peak exercise using the cycle ergometer. B-type natriuretic peptide levels were measured at rest and after exercise. The patients also performed a 6-minute walk test and short-form 36-Item Health Survey questionnaire. We enrolled 110 patients, with resting mean mitral diastolic gradient of ≤3 mm Hg in 35 patients (group 1) and >3 mm Hg indicative of elevated mitral gradients in 75 patients (group 2). Posterior mitral leaflet plication (P=0.04) and the use of a complete mitral annuloplasty ring (P<0.0001) were associated with elevated mitral gradients. Group 2 patients had larger left atrial volume (P=0.02), higher mitral gradients at peak exercise and higher pulmonary artery systolic pressure at rest and at peak exercise, and lower exercise capacity (101±40 versus 122±51 W; P=0.02). Group 2 patients also had higher B-type natriuretic peptide levels and lower scores in 3 short-form 36-Item Health Survey health concepts. Multivariate regression analyses showed that mitral valve area was an independent predictor of maximum exercise capacity (P=0.003). Conclusions-After mitral valve repair for degenerative mitral regurgitation, elevated mitral gradients is not uncommon and is associated with worse intracardiac hemodynamics, higher B-type natriuretic peptide levels, lower exercise capacity, and poorer quality of life. Further refinement in the surgical technique may reduce the incidence of this complication. (Circ Cardiovasc Imaging. 2013;6:1041-1047.)Key Words: exercise capacity ◼ mitral valve insufficiency ◼ mitral valve repair ◼ mitral valve stenosis ◼ quality of life

O bstructive sleep apnea (OSA), present in approximately a third of all patients with heart failure (HF) with reduced ejection fraction (HFrEF), [1][2][3] is an independent predictor of mortality. 4 Common to both HFrEF and OSA are sympathetic nervous system (SNS) activation and impaired myocardial energetic efficiency. Clinical Perspective on p 901Myocardial efficiency estimates the capacity of the heart to convert oxygen into effective forward stroke work.5-9 The noninvasively derived cardiac work metabolic index (WMI) estimates efficiency by quantifying forward minute-work of the Background-Heart failure with reduced ejection fraction and obstructive sleep apnea (OSA), 2 states of increased metabolic demand and sympathetic nervous system activation, often coexist. Continuous positive airway pressure (CPAP), which alleviates OSA, can improve ventricular function. It is unknown whether this is due to altered oxidative metabolism or presynaptic sympathetic nerve function. We hypothesized that short-term (6-8 weeks) CPAP in patients with OSA and heart failure with reduced ejection fraction would improve myocardial sympathetic nerve function and energetics. Methods and Results-Forty-five patients with OSA and heart failure with reduced ejection fraction (left ventricular ejection fraction 35.8±9.7% [mean±SD]) were evaluated with the use of echocardiography and 11 C-acetate and 11 C-hydroxyephedrine positron emission tomography before and ≈6 to 8 weeks after randomization to receive short-term CPAP (n=22) or no CPAP (n=23). Work metabolic index, an estimate of myocardial efficiency, was calculated as follows: (stroke volume index×heart rate×systolic blood pressure÷K mono ), where K mono is the monoexponential function fit to the myocardial ; P=0.003). There was no significant change in work metabolic index between groups. However, in those with more severe OSA (apnea-hypopnea index >20 events per hour), CPAP significantly increased both work metabolic index and systolic blood pressure (P<0.05). Conclusions-In patients with heart failure with reduced ejection fraction and OSA, short-term CPAP increased hydroxyephedrine retention, indicating improved myocardial sympathetic nerve function, but overall did not affect energetics. In those with more severe OSA, CPAP may improve cardiac efficiency. Further outcome-based investigation of the consequences of CPAP is warranted. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT00756366.(Circulation. 2014;130:892-901.)

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C-acetate PET measurements of WMI and MEE exhibited excellent test-retest repeatability and operator reproducibility. Newer PET-CT scanners may be preferred for longitudinal tracking of cardiac efficiency.