Myocardial External Efficiency in Asymptomatic Severe Primary Mitral Regurgitation Using 11C-Acetate PET.

Subjects with asymptomatic moderate-to-severe or severe primary mitral regurgitation are closely observed for signs of progression or symptoms requiring surgical intervention. The role of myocardial metabolic function in progression of mitral regurgitation is poorly understood. We used 11C-acetate PET to noninvasively measure myocardial mechanical external efficiency (MEE), which is the energetic ratio of external cardiac work and left ventricular (LV) oxygen consumption. Methods: Forty-seven patients in surveillance with mitral regurgitation and no or minimal symptoms prospectively underwent PET, echocardiography, and cardiac MRI on the same day. PET was used to simultaneously measure cardiac output, LV mass, and oxygen consumption to establish MEE. PET findings were compared between patients and healthy volunteers (n = 9). MEE and standard imaging indicators of regurgitation severity, LV volumes, and function were studied as predictors of time to surgical intervention. Patients were followed a median of 3.0 y (interquartile range, 2.0-3.8 y), and the endpoint was reached in 22 subjects (47%). Results: MEE in patients reaching the endpoint (23.8% ± 5.0%) was lower than in censored patients (28.5% ± 4.5%, P = 0.002) or healthy volunteers (30.1% ± 4.9%, P = 0.001). MEE with a cutoff lower than 25.7% was significantly associated with the outcome (hazard ratio, 7.5; 95% CI, 2.7-20.6; P < 0.0001) and retained independent significance when compared with standard imaging parameters. Conclusion: MEE independently predicted time to progression requiring valve surgery in patients with asymptomatic moderate-to-severe or severe primary mitral regurgitation. The study suggests that inefficient myocardial oxidative metabolism precedes clinically observed progression in mitral regurgitation.

Changes in global longitudinal strain and left ventricular ejection fraction during the first year after myocardial infarction: results from a large consecutive cohort.

Aims: To determine changes of global longitudinal strain (GLS) and their predictors in relation to classical echocardiographic parameters of left ventricular (LV) function, over 1 year, in consecutive patients with myocardial infarction (MI) and initially normal or impaired LV ejection fraction (EF). Methods and results: A total of 285 patients with MI prospectively included in the REBUS (RElevance of Biomarkers for future risk of thromb-oembolic events in UnSelected post-myocardial infarction patients) study underwent echocardiography within 72 h from admission and after 1 year. At baseline, 213 (74.7%) of MI patients had a normal EF (≥52% in men or ≥54% in women), but in 70.4% of them, an impaired GLS ( ≥ -18.0%) was observed. During 1-year follow-up, in patients with normal EF at baseline, GLS improved from -15.8% to - 17.4% (10.1% relative change); EF decreased from 62.5% to 59.9% (4.0% relative change); indexed end-diastolic volume, indexed end-systolic volume, and indexed stroke volume increased with 15.6%, 24.8%, and 10.0% of relative change, respectively (P < 0.001 for all the comparisons). In the whole cohort, initial impairment of LV function [by EF, wall motion score index (WMSI), or GLS], male gender, non-smoking, and treatment with beta-blockers were the independent predictors of GLS improvement. In the group with initially impaired EF, over 1 year GLS improved from -11.9% to - 14.8% (24.4% relative change) and EF from 44.6% to 52.6% (18.2% relative change) (P < 0.001 for both). Improvement in GLS significantly correlated with EF increase in the group with impaired EF (r = -0.41, P = 0.001) but not in the patients with normal EF (r = -0.14, P = ns). Conclusions: Despite diveregent evolution of GLS compared with EF and ventricular volumes, one year after MI GLS significantly improved in patients with initially both normal and impaired EF. Initial impairment of LV function (by EF, WMSI, or GLS), male gender, non-smoking, and treatment with beta-blockers were independent predictors of GLS improvement. LV remodelling was present even in patients with normal EF at baseline and during follow-up, confirming limited functional assessment by EF alone.