Stress testing for the evaluation of patients with mitral regurgitation

Functional Mitral Regurgitation in Heart Failure

Functional mitral regurgitation (FMR) in the setting of left ventricular (LV) dysfunction and heart failure portends a poor prognosis. Guideline-directed medical therapy remains the cornerstone of initial treatment, with emphasis placed on treatment of the underlying LV dysfunction, as FMR is a secondary phenomenon and a disease due to LV remodeling. Surgical correction of FMR is controversial because it typically does not address the underlying mechanism and etiology of the condition. However, new, minimally invasive transcatheter therapies, in particular the MitraClip system, have shown promise in the treatment of FMR in selected patients. This review will summarize the pathophysiology underlying FMR, the prognosis of patients with heart failure and FMR, and the various medical and procedural treatment options currently available and under investigation.

Stress echocardiography in patients with native valvular heart disease

Valve stress echocardiography (VSE) can be performed as exercise stress echocardiography (ESE) or dobutamine stress echocardiography (DSE) depending on the patient’s clinical status, severity and type of valve disease. ESE combines exercise testing with two-dimensional grey scale and Doppler echocardiography during exercise. Thus, it provides objective assessment of symptomatic status (exercise test), as well as exercise-induced changes of a series of echocardiographic parameters (different depending on the valve disease type), which yield prognostic information in individual patients and help in a better treatment planning. DSE is useful in symptomatic patients with low-gradient aortic stenosis. It clarifies its severity and helps in assessing surgical risk in patients with severe disease and systolic dysfunction. It can be also used to test valve haemodynamics in asymptomatic patients with significant mitral stenosis unable to perform an exercise test or to test the left ventricle response, namely to test viability, in patients with ischaemic secondary mitral regurgitation. VSE has taught us that history taking, clinical examination and resting echocardiography give an ‘incomplete picture’ of the disease in patients presenting with a severe valve disease. Therefore, its use should be encouraged in such patients.

Early surgical intervention or watchful waiting for the management of asymptomatic mitral regurgitation: a systematic review and meta-analysis

BACKGROUND

Discordance between studies drives continued debate regarding the best management of asymptomatic severe mitral regurgitation (MR). The aim of the present study was to conduct a systematic review and meta-analysis of management plans for asymptomatic severe MR, and compare the effectiveness of a strategy of early surgery to watchful waiting.

METHODS

A systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Studies were excluded if they: (I) lacked a watchful waiting cohort; (II) included symptomatic patients; or (III) included etiologies other than degenerative mitral valve disease. The primary outcome of the study was all-cause mortality at 10 years. Secondary outcomes included operative mortality, repair rate, repeat mitral valve surgery, and development of new atrial fibrillation.

RESULTS

Five observational studies were eligible for review and three were included in the pooled analysis. In asymptomatic patients without class I triggers (symptoms or ventricular dysfunction), pooled analysis revealed a significant reduction in long-term mortality with an early surgery approach [hazard ratio (HR) =0.38; 95% confidence interval (CI): 0.21-0.71]. This survival benefit persisted in a sub-group analysis limited to patients without class II triggers (atrial fibrillation or pulmonary hypertension) [relative risk (RR) =0.85; 95% CI: 0.75-0.98]. Aggregate rates of operative mortality did not differ between treatment arms (0.7% vs. 0.7% for early surgery vs. watchful waiting). However, significantly higher repair rates were achieved in the early surgery cohorts (RR =1.10; 95% CI: 1.02-1.18).

CONCLUSIONS

Despite disagreement between individual studies, the present meta-analysis demonstrates that a strategy of early surgery may improve survival and increase the likelihood of mitral valve repair compared with watchful waiting. Early surgery may also benefit patients when instituted prior to the development of class II triggers.

An intriguing case report of functional mitral regurgitation treated with MitraClip

Functional mitral regurgitation (FMR) is frequent in patients with heart failure (HF). It develops as a consequence of left ventricle (LV) geometry alterations, causing imbalance between increased tethering forces and decreased closing forces exerted on the mitral valve apparatus during systole.FMR is known to change at rest and during effort, due to preload-afterload changes, myocardial ischemia, and/or LV dysfunction. Despite optimized medical therapy, an FMR can be responsible of shortness of breath limiting quality of life and decompensation. In this report, we present a case of dynamic FMR treated with MitraClip.MitraClip implantation is a successful and innovative opportunity for HF patients with FMR.

Timing of surgery in valvular heart disease: prophylactic surgery vs watchful waiting in the asymptomatic patient

In the absence of randomized controlled trial data, the management of patients with severe valvular heart disease without symptoms, ventricular dysfunction, or other identified triggers for surgery is controversial. In this review, we frame the debate between prophylactic surgery vs close follow-up until triggers occur (watchful waiting) for severe aortic stenosis and degenerative mitral regurgitation (MR), the 2 conditions for which the pros and cons of these approaches are best articulated. Classic high-gradient severe aortic stenosis is generally accurately diagnosed. In asymptomatic patients, stress testing can be used to confirm asymptomatic status and identify high-risk features including reduced exercise tolerance, exercise-induced symptoms, and absolute or relative hypotension. Resting echocardiographic predictors of disease progression and/or adverse events include very high gradients, rapid progression, and extensive calcification. Surgical risk calculators can help estimate perioperative morbidity/mortality with the ultimate choice of a medical vs a prophylactic surgical approach to be made after discussion with the patient. With degenerative MR, severity can be inaccurately estimated. Stress testing might clarify whether the patient is truly asymptomatic and identify features associated with worse prognosis and symptom onset. Selecting patients with high probability of repair can be challenging. Perioperative risk and postoperative risks including those of unanticipated valve replacement and recurrent MR after repair are also considerations. In aggregate, management of patients with valvular disease who are asymptomatic and who have no clear trigger for surgery is complex, requires individualization, and should be carried out by or in collaboration with a heart valve centre of excellence.

Devices for mitral valve repair

The natural history of severe mitral regurgitation (MR) is unfavorable, leading to left ventricular failure, atrial fibrillation, stroke, and death. Many patients affected by severe regurgitation (MR) do not currently undergo surgery, mainly due to the perceived risk of the procedure (old age, impaired left ventricular function, and comorbidities). Mitral transcatheter interventions carry the hope of minimizing risks while preserving clinical efficacy of surgical repair, as an alternative to conventional treatment. Multiple technologies and diversified approaches are under development with the purpose of treating MR in less invasive ways. They can be categorized based on the anatomical and patho-physiological addressed target. Among them, MitraClip (Abbott Vascular, Inc., Menlo Park, California) has emerged as a clinically safe and effective method for percutaneous mitral valve repair in patients either with degenerative and functional regurgitation. This device mimics the surgical edge-to-edge repair initially described by Alfieri in the early 1990s. Other repair technologies include percutaneous direct and indirect annuloplasty, neochordae implantation, and left ventricular reshaping. They are still in early phase clinical trials or preclinical studies. The combination of different repair techniques is likely to be required to achieve good long-lasting results. In the future, novel devices, improved knowledge, more efficient imaging, and transcatheter mitral prosthetic valve implantation may expand the indications to those patients currently not treated, as well as improve the results both in terms of early efficacy and long-term durability. These treatments are currently reserved to high-risk and inoperable patients, and their application requires an integrated Heart-Team approach. They represent the natural evolution of surgery and promise to expand treatment options and improve patients' outcomes in the near future.

Coexistence of dynamic mitral regurgitation and dynamic left ventricular dyssynchrony in a patient with repeated episodes of acute pulmonary edema: improvement with cardiac resynchronization therapy

A 69-year-old woman with idiopathic dilated cardiomyopathy and chronic heart failure experienced repeated hospital admissions for acute pulmonary edema with no recognizable precipitating factor. Worsening mitral regurgitation was triggered by exercise echocardiography and significant intraventricular dyssynchrony was elicited by low-dose dobutamine stress echocardiography. After cardiac resynchronization therapy she remained free of hospitalizations for 12 months. This case highlights the dynamic nature of both functional mitral regurgitation and left ventricular dyssynchrony and illustrates how in some patients stress echocardiography can help to clarify clinical scenarios and help with the challenging task of selecting patients who will benefit from cardiac resynchronization therapy.

The role of exercise echocardiography in the management of mitral valve disease

PURPOSE

Exercise echocardiography can assess the dynamic component of mitral valve (MV) disease and may therefore be helpful for the clinical decision-making by the heart team. The purpose of this study is to determine the role of exercise echocardiography in the management of disproportionately symptomatic or otherwise atypical patients with mitral regurgitation (MR) and stenosis (MS) in clinical practice.

METHODS

Data of 14 MR and 14 MS patients, including echocardiograms at rest, were presented retrospectively to an experienced heart team to determine treatment strategy. Subsequently, exercise echo data were provided whereupon once again the treatment strategy was determined. This resulted in: value of exercise echo by means of 1) alteration or 2) confirmation of treatment strategy or 3) no additional value.

RESULTS

During exercise the echocardiographic severity of MV disease increased in 9 (64 %) MR and 8 (57 %) MS patients. Based upon alteration or confirmation of the treatment strategy, the value of exercise echocardiography in the management of MR and MS was 86 % and 57 %, respectively.

CONCLUSION

This study showed that physical exercise echo can have an important role in the clinical decision-making of challenging patients with MV disease. Exercise echocardiography had additional value to the treatment strategy in 71 % of these patients.

Mitral transcatheter technologies

Mitral valve regurgitation (MR) is often diagnosed in patients with heart failure and is associated with worsening of symptoms and reduced survival. While surgery remains the gold standard treatment in low-risk patients with degenerative MR, in high-risk patients and in those with functional MR, transcatheter procedures are emerging as an alternative therapeutic option. MitraClip(®) is the device with which the largest clinical experience has been gained to date, as it offers sustained clinical benefit in selected patients. Further to MitraClip implantation, several additional approaches are developing, to better match with the extreme variability of mitral valve disease. Not only repair is evolving, initial steps towards percutaneous mitral valve implantation have already been undertaken, and initial clinical experience has just started.

Orthostatic stress echocardiography as a useful test to measure variability of transvalvular pressure gradients in aortic stenosis

The aim of the study was to assess the influence of the orthostatic stress test on changes in aortic pressure gradients in patients with aortic stenosis (AS).

METHODS

The orthostatic stress test was performed in 56 AS patients. The maximum aortic gradient was compared between the supine and the upright position (using Doppler echocardiography from the apical window). The left hand of each patient was kept on top of their head for both readings. 21 patients were excluded from the study for three reasons: 1) atrial fibrillation (significant beat-to-beat variability of measured gradient), 2) suboptimal Doppler signal during the orthostatic test, and 3) aortic gradient significantly higher in suprasternal or right parasternal windows than in apical window (different direction of stenosed blood jets) in the supine examination. The last limitation (#3) is methodologically important because during the orthostatic examination, only the transapical measurement was used. We were able to analyze 35 AS patients (20 males, 15 females, mean age 74.8 ± 9.2 years).

RESULTS

The wide range of severity of AS was examined (maximal aortic gradient in the supine position from 30 to 146 mmHg). With regard to statistical trends, the mean value of the maximum aortic gradient significantly decreased after orthostatic stress (from 87.5 ± 28.6 to 75.8 ± 23.7 mmHg), p > 0.01). In 7 patients (increasing responders) the peak aortic gradient slightly increased during the stress test. Five of the seven only increased by a few percent. The other two patients increased by nearly 10%. In contrast, the remaining 28 AS patients' gradient decreased by as much as 40% (decreasing responders).

CONCLUSIONS

The orthostatic position test frequently generated a decrease of "theoretically fixed at rest" valvular gradient in AS. The combination of the stiffened stenotic valve apparatus and a reduced LV preload may be responsible for this decreasing response.