Clinical and Prognostic Implications of Cardiopulmonary Exercise Stress Echocardiography in Asymptomatic Degenerative Mitral Regurgitation.

The current guidelines recommend intervention in severe degenerative mitral regurgitation (MR) in symptomatic patients or asymptomatic patients with left ventricular dilatation or dysfunction. The insidious onset of symptoms may mean that patients do not report their symptoms. The role of systematic exercise testing for symptoms in MR is not clearly defined. A total of 97 patients with moderate to severe asymptomatic MR underwent exercise echocardiography combined with cardiopulmonary exercise testing. The predictors of exercise-induced dyspnea, symptom-free survival, and mitral valve intervention were identified. A total of 18 patients (19%) developed limiting dyspnea on exercise. Spontaneous symptom-free survival at 24 months was significantly higher in those without exercise-induced symptoms than those with exercise-induced symptoms, p <0.0001. The only independent predictors of spontaneous symptoms at 2 years were effective regurgitant orifice area (odds ratio 27.45, 95% confidence interval [CI] 1.43 to 528.40, p = 0.03) and exercise-induced symptoms (odds ratio 11.56, 95% CI 1.71 to 78.09, p = 0.01). The only independent predictor of surgery was indexed left ventricular systolic volumes (odds ratio 1.17, 95% CI 1.04 to 1.30, p = 0.006). Where only the patients who underwent surgery due to symptoms were included, the only independent predictor was exercise-induced symptoms (odds ratio 13.94, 95% CI 1.39 to 140.27, p = 0.025). In conclusion, in patients with primary asymptomatic degenerative MR, 1/5 develop revealed symptoms during exercise. This predicts a subsequent development of spontaneous symptoms and mitral valve intervention due to symptoms.

Determinants of post-operative left ventricular dysfunction in degenerative mitral regurgitation.

AIMS: Chronic degenerative mitral regurgitation leads to volume overload causing left ventricular (LV) enlargement and eventually LV impairment. Current guidelines determining thresholds for intervention are based on LV diameters and ejection fraction (LVEF). There are sparse data examining the value of LV volumes and newer markers of LV performance on outcomes of surgery in mitral valve prolapse. The aim of this study is to identify the best marker of LV impairment after mitral valve surgery. METHODS AND RESULTS: Prospective, observational study of patients with mitral valve prolapse undergoing mitral valve surgery. Pre-operative LV diameters, volumes, LVEF, global longitudinal strain (GLS), and myocardial work measured. Post-operative LV impairment defined as LVEF < 50% at 1 year post-surgery. Eighty-seven patients included. Thirteen percent developed post-operative LV impairment. Patients with post-operative LV dysfunction showed significantly larger indexed LV end-systolic diameters, indexed LV end-systolic volumes (LVESVi), lower LVEF, and more abnormal GLS than patients without post-operative LV dysfunction. In multivariate analysis, LVESVi [odds ratio 1.11 (95% CI 1.01-1.23), P = 0.039] and GLS [odds ratio 1.46 (95% CI 1.00-2.14), P = 0.054] were the only independent predictors of post-operative LV dysfunction. The optimal cut-off of 36.3 mL/m2 for LVESVi had a sensitivity of 82% and specificity of 78% for detection of post-operative LV impairment. CONCLUSION: Post-operative LV impairment is common. Indexed LV volumes (36.3 mL/m2) provided the best marker of post-operative LV impairment.

Direct in vivo assessment of global and regional mechanoelectric feedback in the intact human heart.

BACKGROUND: Inhomogeneity of ventricular contraction is associated with sudden cardiac death, but the underlying mechanisms are unclear. Alterations in cardiac contraction impact electrophysiological parameters through mechanoelectric feedback. This has been shown to promote arrhythmias in experimental studies, but its effect in the in vivo human heart is unclear. OBJECTIVE: The purpose of this study was to quantify the impact of regional myocardial deformation provoked by a sudden increase in ventricular loading (aortic occlusion) on human cardiac electrophysiology. METHODS: In 10 patients undergoing open heart cardiac surgery, left ventricular (LV) afterload was modified by transient aortic occlusion. Simultaneous assessment of whole-heart electrophysiology and LV deformation was performed using an epicardial sock (240 electrodes) and speckle-tracking transesophageal echocardiography. Parameters were matched to 6 American Heart Association LV model segments. The association between changes in regional myocardial segment length and activation-recovery interval (ARI; a conventional surrogate for action potential duration) was studied using mixed-effect models. RESULTS: Increased ventricular loading reduced longitudinal shortening (P = .01) and shortened ARI (P = .02), but changes were heterogeneous between cardiac segments. Increased regional longitudinal shortening was associated with ARI shortening (effect size 0.20 [0.01-0.38] ms/%; P = .04) and increased local ARI dispersion (effect size -0.13 [-0.23 to -0.03] ms/%; P = .04). At the whole organ level, increased mechanical dispersion translated into increased dispersion of repolarization (correlation coefficient r = 0.81; P = .01). CONCLUSION: Mechanoelectric feedback can establish a potentially proarrhythmic substrate in the human heart and should be considered to advance our understanding and prevention of cardiac arrhythmias.

The importance of contractile reserve in predicting exercise tolerance in asymptomatic patients with severe aortic stenosis.

BACKGROUND: Mortality dramatically rises with the onset of symptoms in patients with severe aortic stenosis (AS). Surgery is indicated when symptoms become apparent or when there is ventricular decompensation. Cardiopulmonary exercise testing (CPET) in combination with exercise echocardiography can unmask symptoms and provides valuable information regarding contractile reserve. The aim of the present study was to determine the prevalence of reduced exercise tolerance and the parameters predicting adverse cardiovascular events. METHODS: Thirty-two patients with asymptomatic severe AS were included in this study. Patients were followed up as part of an enhanced surveillance clinic. RESULTS: Age was 69 ± 15.7 years, 75% of patients were male. Patients had a raised NT-ProBNP of 301 pg/mL. VO2peak was 19.5 ± 6.2 mL/kg/min. Forty-one percent of patients had a reduced %VO2peak and this predicted unplanned cardiac hospitalisation (P = 0.005). Exercise systolic longitudinal velocity (S') and age were the strongest independent predictors for VO2peak (R 2 = 0.76; P < 0.0001). Exercise S' was the strongest independent predictor for NT-ProBNP (R 2 = 0.48; P = 0.001). CONCLUSION: A large proportion of patients had a lower than predicted VO2peak. The major determinant of exercise and NT-ProBNP is the ability of the left ventricle (LV) to augment S' on exercise rather than the severity of aortic valve obstruction or resting structural remodelling of the LV. Reduced exercise tolerance and more adverse remodelling, rather than valve obstruction predicted unplanned hospitalisation. This study demonstrates that for those patients, in whom a watchful waiting is an agreed strategy, a detailed assessment should be undertaken including CPET, exercise echocardiography and biomarkers to ensure those with exercise limitation and risk of decompensation are detected early and treated appropriately.

Aortic Stenosis, a Left Ventricular Disease: Insights from Advanced Imaging.

Aortic stenosis (AS) is the most common primary valve disorder in the elderly with an increasing prevalence. It is increasingly clear that it is also a disease of the left ventricle (LV) rather than purely the aortic valve. The transition from left ventricular hypertrophy to fibrosis results in the eventual adverse effects on systolic and diastolic function. Appropriate selection of patients for aortic valve intervention is crucial, and current guidelines recommend aortic valve replacement in severe AS with symptoms or in asymptomatic patients with left ventricular ejection fraction (LVEF) <50 %. LVEF is not a sensitive marker and there are other parameters used in multimodality imaging techniques, including longitudinal strain, exercise stress echo and cardiac MRI that may assist in detecting subclinical and subtle LV dysfunction. These findings offer potentially better ways to evaluate patients, time surgery, predict recovery and potentially offer targets for specific therapies. This article outlines the pathophysiology behind the LV response to aortic stenosis and the role of advanced multimodality imaging in describing it.

Structural cure for reflex syncope?

The ROX Coupler is a device that allows creation of a central arteriovenous anastomosis at the iliac level. The device has been shown to improve exercise capacity in patients with chronic obstructive pulmonary disease and is CE marked for the treatment of resistant and uncontrolled hypertension. Reflex syncope is a challenging clinical condition with limited proven therapeutic options. We describe the resolution of symptoms and tilt table response of a patient who underwent insertion of a ROX Coupler to treat hypertension, and also incidentally had pre-existing vasodepressor syncope.