Role of the left atrium in adaptation of the heart to chronic mitral regurgitation in conscious dogs

Reappraisal of the Concept and Implications of Pulmonary Hypertension in Degenerative Mitral Regurgitation

BACKGROUND

European and U.S. clinical guidelines diverge regarding pulmonary hypertension (PHTN) in degenerative mitral regurgitation (DMR). Gaps in knowledge underpinning these divergences affect risk assessment and management recommendations attached to systolic pulmonary pressure (SPAP) in DMR.

OBJECTIVES

This study sought to define PHTN links to DMR severity, prognostic thresholds, and independent outcome impact in a large quantitative DMR registry.

METHODS

This study gathered a large multicentric registry of consecutive patients with isolated moderate-to-severe DMR, with DMR and SPAP quantified prospectively at diagnosis.

RESULTS

In 3,712 patients (67 ± 15 years, 36% women) with ≥ moderate-to-severe DMR, effective regurgitant orifice (ERO) was 0.42 ± 0.19 cm2, regurgitant volume 66 ± 327 mL/beat and SPAP 41 ± 16 mm Hg. Spline-curve analysis showed excess mortality under medical management emerging around SPAP 35 mm Hg and doubling around SPAP 50 mm Hg. Accordingly, severe pulmonary hypertension (sPHTN) (SPAP ≥50 mm Hg) was detected in 916 patients, moderate pulmonary hypertension (mPHTN) (SPAP 35-49 mm Hg) in 1,128, and no-PHTN (SPAP <35 mm Hg) in 1,668. Whereas SPAP was strongly associated with DMR-ERO, nevertheless excess mortality with sPHTN (adjusted HR: 1.65; 95% CI: 1.24-2.20) and mPHTN (adjusted HR: 1.44; 95% CI: 1.11-1.85; both P ≤ 0.005) was observed independently of ERO and all baseline characteristics and in all patient subsets. Nested models demonstrated incremental prognostic value of mPHTN and sPHTN (all P < 0.0001). Despite higher operative risk with mPHTN and sPHTN, DMR surgical correction was followed by higher survival in all PHTN ranges with strong survival benefit of early surgery (<3 months). Postoperatively, excess mortality was abolished (P ≥ 0.30) in mPHTN, but only abated in sPHTN.

CONCLUSIONS

This large international registry, with prospectively quantified DMR and SPAP, demonstrates a Doppler-defined PHTN impact on mortality, independent of DMR severity. Crucially, it defines objectively the new and frequent mPHTN range, independently linked to excess mortality under medical management, which is abolished by DMR correction. Thus, at DMR diagnosis, Doppler-SPAP measurement defining these new PHTN ranges, is crucial to guiding DMR management.

Left atrial and left ventricular strain dynamics with echocardiography in asymptomatic children with mitral regurgitation

Left atrial (LA) dilatation is a strong predictor of cardiovascular morbidity and mortality. Strain parameters evaluating LA functions have gained importance in assessing cardiovascular health. This study aimed to investigate the relationship between LA and left ventricular (LV) strain, using speckle-tracking echocardiography, and assess the impact of vena contracta on LV functioning in asymptomatic children with mitral regurgitation. We evaluated 45 asymptomatic mitral regurgitation patients, categorized as mild, moderate, and severe. LV strain was significantly lower in the moderate group (-17.8 ± 3.7%) and further reduced in the severe group (16 ± 2.1%) compared to the reference group (20.5 ± 6.2%). Conversely, LA reservoir strain was higher in the severe and moderate groups (38 ± 12.9% and 40.7 ± 9.5%, respectively) compared to the controls (31.3 ± 7.5%; p < 0.0001). The severe group also displayed a milder depression of contraction (12.2%) compared to the moderate group (13 ± 7.2%). In the moderate and severe groups, LV strain correlated significantly with vena contracta (r=-0.858; p = 0.04), with vena contracta emerging as the only independent predictor for LV longitudinal strain. ROC curve analysis indicated a cut-off value > 5.65 mm for vena contracta, which had a positive predictive value of 75% for predicting LV function impairment. In conclusion, this study emphasizes the significance of assessing LA and ventricular strain in asymptomatic children with mitral regurgitation. Furthermore, vena contracta with diameters greater than 5.6 mm may alert clinicians to the possibility of LV function impairment. These findings offer valuable insights for the follow-up and management of paediatric patients with mitral regurgitation, enabling early detection of potential complications and improved patient outcomes.

Feasibility of concomitant exclusion of left atrial appendage during novel transapical off-pump beating heart mitral valve repair

The AtriClip device enables the safe and reproducible epicardial clipping of the left atrial appendage. Transapical off-pump beating heart mitral valve repair using NeoChord DS100 Artificial Chordae Delivery System has matured and become more standardized. We aim to evaluate the feasibility of combining NeoChord repair and left atrial appendage exclusion in a single procedure through the same minithoracotomy in patients with mitral valve prolapse and atrial fibrillation. From 2018 to 2019, seven patients with severe mitral regurgitation and atrial fibrillation underwent transesophageal echocardiography-guided transapical off-pump mitral valve repair with the novel NeoChord DS 1000 system and concomitant left atrial appendage exclusion using the AtriClip Pro II device. Both procedures were performed via left mini-thoracotomy. The AtriClip device was applied after the NeoChord repair was done. All seven patients had less than moderate mitral regurgitation after the NeoChord repair and successful left atrial appendage occlusion. There were no device or procedure-related complications. Clinical follow-up revealed significant symptomatic improvement, and no cardiovascular complications were reported. Transesophageal echocardiography at 6-12 months post-procedure showed stable left atrial appendage occlusion with no residual flow between the left atrium and the left atrial appendage and a stump of less than 5 mm. Beating heart epicardial clipping of the left atrial appendage using AtriClip concomitant with transapical mitral valve repair using Neochord DS 1000 system is a feasible and safe treatment option in mitral valve prolapse and atrial fibrillation in patients with limited indications. However, its safety needs to be confirmed in a larger series of patients.

Mitral regurgitation in the critically ill: the devil is in the detail

Mitral regurgitation (MR) is common in the critically unwell and encompasses a heterogenous group of conditions with diverging therapeutic strategies. MR may present acutely with haemodynamic instability or more insidiously with failure to wean from mechanical ventilation. Critical illness is associated with marked physiological stress and haemodynamic changes that dynamically influence the severity and implication of MR. The expanding role of critical care echocardiography uniquely positions the intensivist to apply advanced bedside valvular assessment to recognise haemodynanically significant MR, manipulate and optimise cardiopulmonary physiology and identify patients requiring urgent cardiology and surgical referral. This review will consider common clinical scenarios, therapeutic strategies and the pearls and pitfalls of echocardiographic assessment and quantification in the critically unwell.

Amlodipine decreases mitral regurgitation volume in dogs over 7 days: A study of 24 dogs with myxomatous mitral valve degeneration

Background

Amlodipine, a dihydropyridine calcium-channel blocker, is currently being investigated as a treatment for myxomatous mitral valvular degeneration (MMVD). However, the effects of amlodipine on moderate or severe spontaneous MMVD, based on changes in echocardiographic indices, remain unclear.

Animals

Client-owned small-breed dogs (n = 24) with naturally occurring MMVD of the American College of Veterinary Internal Medicine (ACVIM) stage B2 or higher.

Methods

Basic dog information including previous medication treatments were recorded. All subjects received amlodipine 0.1 mg/kg, administered per os, twice daily for 7 days, in addition to their existing medication. We measured systolic blood pressure, obtained x-ray, echocardiography, blood test data before and after 1 week of amlodipine administration.

Results

Left ventricular end-diastolic internal diameter, left atrial diameter and E wave reduced statistically after 1 week of amlodipine treatment (all p < 0.001). No adverse effects were reported.

Conclusions

These findings suggest that low-dose amlodipine should be considered as treatment for dogs with ACVIM stage B2‒C MMVD.

Left Atrial Remodeling after Mitral Valve Repair for Primary Mitral Regurgitation: Evolution over Time and Prognostic Significance

Left atrial (LA) dilatation is associated with worse outcomes in primary mitral regurgitation (MR). However, the effects of mitral valve repair on LA size and its prognostic implications are not well known. In the current study, LA volume index (LAVi) and LA reservoir strain (LASr) were evaluated immediately before and after surgery, and during long-term follow-up in 226 patients undergoing mitral valve repair for primary MR (age 62 ± 13 years, 66% male). Mean LAVi was reduced significantly after surgery and at long-term follow-up (from 56 ± 28 to 38 ± 21 to 32 ± 17 mL/m2; p < 0.001). LASr reduced significantly after surgery but increased again during the long-term (from 23.6 ± 9.4 to 11.5 ± 5.0 to 17.3 ± 7.5%; p < 0.001). Age, pre-operative LAVi, MR severity, and postoperative transmitral pressure gradient were associated with LA reverse remodeling by the long-term check-up. During a median follow-up of 72 (40−114) months, 43 (19%) patients died. Patients with LAVi ≥ 42 mL/m2 at long-term follow-up showed significant higher mortality rates compared to patients with LAVI < 42 mL/m2 (p < 0.001), even after adjusting for clinical covariates. In conclusion, significant LA reverse remodeling was observed both immediately and at long-term follow-up after mitral valve repair. LA dilatation at long term follow-up after surgery was still associated with all-cause mortality.

Left atrial remodeling in mitral regurgitation: A combined experimental-computational study

Aims

Progressive changes to left atrial (LA) structure and function following mitral regurgitation (MR) remain incompletely understood. This study aimed to demonstrate potential underlying mechanisms using experimental canine models and computer simulations.

Methods

A canine model of MR was created by cauterization of mitral chordae followed by radiofrequency ablation-induced left bundle-branch block (LBBB) after 4 weeks (MR-LBBB group). Animals with LBBB alone served as control. Echocardiography was performed at baseline, acutely after MR induction, and at 4 and 20 weeks, and correlated with histology and computer simulations.

Results

Acute MR augmented LA reservoir and contractile strain (40±4 to 53±6% and -11±5 to -22±9% respectively, p<0.05). LA fractional area change increased significantly (47±4 to 56±4%, p<0.05) while LA end-systolic area remained unchanged (7.2±1.1 versus 7.9±1.1 cm2 respectively, p = 0.08). LA strain ‘pseudonormalized’ after 4 weeks and decompensated at 20 weeks with both strains decreasing to 25±6% and -3±2% respectively (p<0.05) together with a progressive increase in LA end-systolic area (7.2±1.1 to 14.0±6.3 cm2, p<0.05). In the LBBB-group, LA remodeling was less pronounced. Histology showed a trend towards increased interstitial fibrosis in the LA of the MR-LBBB group. Computer simulations indicated that the progressive changes in LA structure and function are a combination of progressive eccentric remodeling and fibrosis.

Conclusion

MR augmented LA strain acutely to supranormal values without significant LA dilation. However, over time, LA strain gradually decreases (pseudornormal and decompensated) with LA dilation. Histology and computer simulations indicated a correlation to a varying degree of LA eccentric remodeling and fibrosis.

Left Atrial Function Post Radiofrequency and Cryoballoon Ablation Assessed by Volume-Pressure Loops

Background

Left atrial (LA) function is linked to atrial fibrillation (AF) pathogenesis. AF catheter ablation decreases disease burden with potentially favorable effects on cardiac function. Atrial volume-pressure loops can optimally assess the LA function.

Objective

To investigate changes in LA function by volume-pressure loops after paroxysmal AF ablation and explored potential differences between the radiofrequency and cryoballoon ablation.

Methods

We analyzed 44 patients undergoing paroxysmal AF ablation from 2 centers, 22 treated with radiofrequency and 22 with cryoablation. Pre- and post-procedure, all patients underwent a real-time three-dimensional transthoracic ECG to evaluate LA volume, while simultaneously recording LA pressure following transseptal puncture. Volume-pressure loops pre- and post-procedure were created by paired data. Areas of A-loop (LA booster pump function) and V-loop (LA reservoir function), and the stiffness constant determining the slope of the exponential curve during LA filling were calculated.

Results

Average LA pressure, A-wave amplitude, and V-wave amplitude were increased post-procedurally (p < 0.001). Overall, A-loop area decreased (p = 0.001) and V-loop area tended to increase (p = 0.07). The change in both A-loop and V-loop areas was similar between radiofrequency- and cryoballoon-treated patients (p = 0.18 and p = 0.52, respectively). However, compared with cryoballoon-treated patients, radiofrequency-treated patients had higher increase in the stiffness constant (b = 0.059; 95% CI: 0.022–0.096; p = 0.006).

Conclusion

AF catheter ablation by the radiofrequency or cryoballoon is associated with the decrease of the booster pump function and increase of the reservoir function. Moreover, there is a post-procedural increase of LA pressure which is associated with an acute increase in LA stiffness in radiofrequency ablation, but not in cryoablation.

Cardiac Imaging for the Assessment of Left Atrial Mechanics Across Heart Failure Stages

The left atrium (LA) is emerging as a key element in the pathophysiology of several cardiac diseases due to having an active role in contrasting heart failure (HF) progression. Its morphological and functional remodeling occurs progressively according to pressure or volume overload generated by the underlying disease, and its ability of adaptation contributes to avoid pulmonary circulation congestion and to postpone HF symptoms. Moreover, early signs of LA dysfunction can anticipate and predict the clinical course of HF diseases before the symptom onset which, particularly, also applies to patients with increased risk of HF with still normal cardiac structure (stage A HF). The study of LA mechanics (chamber morphology and function) is moving from a research interest to a clinical application thanks to a great clinical, prognostic, and pathophysiological significance. This process is promoted by the technological progress of cardiac imaging which increases the availability of easy-to-use tools for clinicians and HF specialists. Two-dimensional (2D) speckle tracking echocardiography and feature tracking cardiac magnetic resonance are becoming essential for daily practice. In this context, a deep understanding of LA mechanics, its prognostic significance, and the available approaches are essential to improve clinical practice. The present review will focus on LA mechanics, discussing atrial physiology and pathophysiology of main cardiac diseases across the HF stages with specific attention to the prognostic significance. Imaging techniques for LA mechanics assessment will be discussed with an overlook on the dynamic (under stress) evaluation of the chamber.

Left atrial structural and mechanical remodelling in heart failure with reduced ejection fraction

Aims

In patients with heart failure with reduced ejection fraction (HFrEF), an association between left atrial (LA) dilatation and dysfunction is expected, but the degree of coexistence of the two abnormalities and their relative prognostic role is not known.

Methods and results

A total of 626 HFrEF patients formed the study population. All of them underwent a comprehensive echocardiographic evaluation. LA maximal volume was indexed to body surface area (LAVi); LA function was assessed using strain analysis during the reservoir phase: peak atrial longitudinal strain (PALS) analysis. Study primary endpoint was overall mortality or hospitalization for worsening heart failure. Four groups of patients were included in this study according to LAVi (≤34 or >34 mL/m²) and PALS (≤23% or >23%); 61 (10%) patients had normal LA volume and function (Group 1), 58 (9%) had LA dilatation but normal function (Group 2), 100 (16%) had normal volume but abnormal function (Group 3), and 407 (65%) had enlarged left atrium and abnormal function (Group 4). PALS was associated with primary endpoint in patients with both normal‐size [Groups 1 and 3: hazard ratio (HR) 0.92, 95% confidence interval (CI) 0.88–0.96; P = 0.0006] and dilated left atria (Groups 2 and 4: HR 0.93, 95% CI 0.91–0.96; P < 0.0001). In contrast, LAVi was associated with the primary endpoint in patients with abnormal LA function (Groups 3 and 4: HR 1.018, 95% CI 1.011–1.024; P < 0.00001) but not in those with normal PALS (Groups 1 and 2: HR 1.023, 95% CI 0.99–1.057; P = 0.1).

Conclusions

Left atrial dilatation and dysfunction frequently but not invariably coexist. PALS emerged as a significant prognostic parameter in HFrEF even in the absence of LA dilation.

The predictive value of clinical, radiographic, echocardiographic variables and cardiac biomarkers for assessing risk of the onset of heart failure or cardiac death in dogs with preclinical myxomatous mitral valve disease enrolled in the DELAY study

OBJECTIVES

To identify the predictive value on time to onset of heart failure (HF) or cardiac death of clinical, radiographic, and echocardiographic variables, as well as cardiac biomarkers N-terminal pro brain natriuretic peptide (NT-proBNP) and cardiac troponin I in dogs with preclinical myxomatous mitral valve disease (MMVD).

ANIMALS

One hundred sixty-eight dogs with preclinical MMVD and left atrium to aortic root ratio ≥1.6 (LA:Ao) and normalized left ventricular end-diastolic diameter ≥1.7 were included.

METHODS

Prospective, randomized, multicenter, single-blinded, placebo-controlled study. Clinical, radiographic, echocardiographic variables and plasma cardiac biomarkers concentrations were compared at different time points. Using receiving operating curves analysis, best cutoff for selected variables was identified and the risk to develop the study endpoint at six-month intervals was calculated.

RESULTS

Left atrial to aortic root ratio >2.1 (hazard ratio [HR] 3.2, 95% confidence interval [95% CI] 1.9-5.6), normalized left ventricular end-diastolic diameter > 1.9 (HR: 6.3; 95% CI: 3.3-11.8), early transmitral peak velocity (E peak) > 1 m/sec (HR: 3.9; 95% CI: 2.3-6.7), and NT-proBNP > 1500 ρmol/L (HR: 5.7; 95% CI: 3.3-9.5) were associated with increased risk of HF or cardiac death. The best fit model to predict the risk to reach the endpoint was represented by the plasma NT-proBNP concentrations adjusted for LA:Ao and E peak.

CONCLUSIONS

Logistic and survival models including echocardiographic variables and NT-proBNP can be used to identify dogs with preclinical MMVD at higher risk to develop HF or cardiac death.

The Evolving Epidemiology of Elderly with Degenerative Valvular Heart Disease: The Guangzhou (China) Heart Study

Aim

The present study was aimed at investigating the prevalence, incidence, progression, and prognosis of degenerative valvular heart disease (DVHD) in permanent residents aged ≥65 years from Guangzhou, China.

Methods

This was a prospective study based on community population. Over a 3-year span, we conducted repeated questionnaires, blood tests, and echocardiographic and electrocardiogram examinations (2018) of a random sample of initially 3538 subjects.

Results

The prevalence of DVHD increased with age, average values being 30.6%, 49.2%, and 62.9% in 65-74, 75-84, and ≥85 years of age, respectively. The incidence rate was 1.7%/year. Aortic stenosis was the result of DVHD, and the mean transvalvular pressure gradient increased by 5.6 mmHg/year. The increase of mild aortic stenosis was lower than that of more severe disease, showing a nonlinear development of gradient, but with great individual variations. Mortality was significantly increased in the DVHD group (HR = 2.49). Risk factors for higher mortality included age (χ² = 1.9, P < 0.05), renal insufficiency (χ² = 12.5, P < 0.01), atrial fibrillation (χ² = 12.2, P < 0.01), mitral regurgitation (χ² = 1.8, P < 0.05), and tricuspid regurgitation (χ² = 6.7, P < 0.05) in a DVHD population.

Conclusions

DVHD was highly prevalent among residents in southern China. With the progression of the disease, the mean transvalvular pressure gradient accelerated. DVHD was an independent predictor of death, and the mortality was higher in those with older age, renal insufficiency, atrial fibrillation, mitral regurgitation, and tricuspid regurgitation.

Diffuse Alveolar Hemorrhage in Cardiac Diseases

Diffuse alveolar hemorrhage (DAH) is a rare condition with reported mortality ranging between 20 and 100%. There are many etiologies of DAH. Cardiac diseases are likely underreported causes of DAH. Heart failure and mitral valve diseases are the most common cardiac causes of DAH. The DAH results from pulmonary venous hypertension leading to stress failure of the pulmonary capillaries. There is also a contribution of the bronchial circulation. The Alveolar-capillary membrane or blood-gas barrier is an extremely thin structure that allows rapid and passive diffusion of oxygen from the inhaled air to the pulmonary capillaries while preventing pulmonary edema and DAH with chronic elevation of the transmural hydrostatic pressure. The purpose of this manuscript is to inform the clinician about this rare cause of DAH, which may be overlooked unless specifically sought after. We also discuss the pathophysiologic aspects of DAH and the safety mechanisms in place to prevent such occurrences.

Hemodynamic function of the right ventricular-pulmonary vascular-left atrial unit: normal responses to exercise in healthy adults

With each heartbeat, the right ventricle (RV) inputs blood into the pulmonary vascular (PV) compartment, which conducts blood through the lungs at low pressure and concurrently fills the left atrium (LA) for output to the systemic circulation. This overall hemodynamic function of the integrated RV-PV-LA unit is determined by complex interactions between the components that vary over the cardiac cycle but are often assessed in terms of mean pressure and flow. Exercise challenges these hemodynamic interactions as cardiac filling increases, stroke volume augments, and cycle length decreases, with PV pressures ultimately increasing in association with cardiac output. Recent cardiopulmonary exercise hemodynamic studies have enriched the available data from healthy adults, yielded insight into the underlying mechanisms that modify the PV pressure-flow relationship, and better delineated the normal limits of healthy responses to exercise. This review will examine hemodynamic function of the RV-PV-LA unit using the two-element Windkessel model for the pulmonary circulation. It will focus on acute PV and LA responses that accommodate increased RV output during exercise, including PV recruitment and distension and LA reservoir expansion, and the integrated mean pressure-flow response to exercise in healthy adults. Finally, it will consider how these responses may be impacted by age-related remodeling and modified by sex-related cardiopulmonary differences. Studying the determinants and recognizing the normal limits of PV pressure-flow relations during exercise will improve our understanding of cardiopulmonary mechanisms that facilitate or limit exercise.

Significant functional mitral regurgitation affects left atrial function in heart failure patients: haemodynamic correlations and prognostic implications

AIMS

Functional mitral regurgitation (FMR) is a well-known pathophysiological factor in heart failure (HF) patients, and left atrial function (LAF) is a novel determinant of clinical status and outcome in this setting. However, little is known about the pathophysiological role of FMR on LAF in HFrEF patients. Aim of this study is to explore the possible interplay between the severity of FMR and LAF in heart failure with reduce ejection fraction (HFrEF) patients and their possible consequences.

METHODS AND RESULTS

We studied 97 consecutive patients with FMR classified in two groups: mild-to-moderate MR ore less (FMR group, n = 38) and moderate-to-severe or more (SFMR group, n = 59). Using the phasic method, left atrial contractile, conduit, reservoir, and total emptying function (TLAEF) were calculated to assess LAF. SFMR group showed significantly lower values of LAF compared to FMR group. LA dysfunction (LA-dys) was defined for TLAEF values below the median and groups divided in four subgroups based on its presence. Patient with LA-Dys in SFMR group showed a worse clinical status, higher incidence of right ventricular dysfunction (RV-Dys), and pulmonary hypertension (PH), and a significant worse clinical survival compared to all other groups.

CONCLUSION

In our study, the survival was significantly lower in SFMR/LA-Dys+ group. Furthermore, LA-Dys was strongly related with worse clinical status and higher incidence of PH and RV-Dys. These results suggest that in patients with SFMR and HFrEF, LA-Dys may represent both a marker of more advanced disease and a novel prognostic factor.

Hemodynamics rounds: Hemodynamics of mitral valve interventions

Mitral valvulopathy presents as regurgitation, stenosis, or mixed disease and can occur in both native and prosthetic valves. Such disease develops in conjunction with pathophysiologic changes in the left atrium (LA) and drives changes in LA compliance, pressure, and thus clinical syndromes. With advances in the understanding and treatment of structural heart disease and in the setting of higher-risk patient populations, less-invasive transcatheter approaches have become increasingly commonplace in the treatment of mitral valve disease. Over time, transcatheter mitral valve interventions have evolved to include paravalvular leak closure, mitral valve repair, and mitral valve replacement. Parallel to this evolution, advances in invasive intracardiac pressure monitoring, particularly at the level of the LA, have also occurred. These advances emphasize the unique interplay between mitral valve disease and LA function; account for limitations of noninvasive assessment; and guide beneficial outcomes in each area of transcatheter mitral valve intervention. As a result, continuous transseptal LA pressure monitoring has developed into an indispensable instrument in successful percutaneous mitral valve intervention, complementing traditional noninvasive assessment.

Mitral regurgitation, left atrial structural and functional remodelling and the effect on pulmonary haemodynamics

AIMS

To assess the association between mitral regurgitation (MR) and left atrial (LA) structural and functional remodelling and their effect on pulmonary haemodynamics.

METHODS AND RESULTS

Consecutive unselected patients undergoing comprehensive echocardiography were enrolled. Parameters of cardiac structure and function were obtained as well as mitral effective regurgitant orifice area (ERO) and estimation of pulmonary artery systolic pressure (PASP). Measures of LA structure [LA volume (LAV)] and function [peak atrial longitudinal strain (PALS), peak atrial contraction strain (PACS) and conduit strain (CS)] were also calculated. The study population included 102 patients (mean age 70 ± 14 years, 42% women), with a mean ejection fraction of 52 ± 13%. MR was classified as organic due to mitral valve prolapse in 14 patients (14%) and functional in 88 patients (86%). Mean ERO was 0.12 ± 0.12 cm² and 86 patients (84%) had an ERO ≤0.2 cm² . ERO was significantly associated with worse measures of LA structure and function. Despite the low burden of MR, the association remained significant after adjusting for clinical and echocardiographic confounders (β: 3.7, P = 0.022 for LAV; β: -3.0, P = 0.003 for PALS; β: -1.8, P = 0.027 for PACS) and was significantly related with functional MR (P for interaction <0.001). ERO was also significantly associated with PASP, and measures of LA function (PALS and PACS) significantly modified this relationship (P for interaction <0.001).

CONCLUSIONS

Even a mild degree of MR contributes to LA remodelling and this relationship plays an active role in pulmonary circulation, suggesting a potential mechanism by which these parameters contribute to the development of heart failure.

Analysis of a coupled fluid-structure interaction model of the left atrium and mitral valve

We present a coupled left atrium-mitral valve model based on computed tomography scans with fibre-reinforced hyperelastic materials. Fluid-structure interaction is realised by using an immersed boundary-finite element framework. Effects of pathological conditions, eg, mitral valve regurgitation and atrial fibrillation, and geometric and structural variations, namely, uniform vs non-uniform atrial wall thickness and rule-based vs atlas-based fibre architectures, on the system are investigated. We show that in the case of atrial fibrillation, pulmonary venous flow reversal at late diastole disappears, and the filling waves at the left atrial appendage orifice during systole have reduced magnitude. In the case of mitral regurgitation, a higher atrial pressure and disturbed flows are seen, especially during systole, when a large regurgitant jet can be found with the suppressed pulmonary venous flow. We also show that both the rule-based and atlas-based fibre defining methods lead to similar flow fields and atrial wall deformations. However, the changes in wall thickness from non-uniform to uniform tend to underestimate the atrial deformation. Using a uniform but thickened wall also lowers the overall strain level. The flow velocity within the left atrial appendage, which is important in terms of appendage thrombosis, increases with the thickness of the left atrial wall. Energy analysis shows that the kinetic and dissipation energies of the flow within the left atrium are altered differently by atrial fibrillation and mitral valve regurgitation, providing a useful indication of the atrial performance in pathological situations.

Effect of saline administration on left atrial pressure during transcatheter mitral valve repair

OBJECTIVES

To measure the intraprocedural change in left atrial pressure (LAP) with saline administration during transcatheter mitral valve repair (TMVR).

BACKGROUND

TMVR with MitraClip offers an alternative to surgery in select patients. During this procedure, large volumes of fluid are routinely administered with anesthesia and to facilitate transcatheter valve repair. LAP, a measure used to guide repair, may thereby change as a result of volume expansion, suggesting a need for continuous intracardiac pressure monitoring.

METHODS

Consecutive patients with severe mitral regurgitation underwent TMVR with MitraClip and continuous LAP monitoring through a dedicated sampling catheter. Specific LAP values were acquired immediately after transseptal access; before first clip deployment; and after deployment of the last clip.

RESULTS

151 patients (age 80 ± 8 years, 64% male) underwent TMVR with MitraClip and continuous LAP monitoring. Mean LAP and v-wave pressure increased significantly from baseline to pre-MitraClip deployment (P < 0.0001) and decreased significantly from deployment to procedure end (P < 0.0001). Linear regression of v-wave pressure change (from procedure start to clip deployment) relative to volume administration yielded a significantly nonzero slope (0.28 mmHg/min, P < 0.0001, r = 0.30).

CONCLUSION

Fluid administration during TMVR leads to time-dependent increases in LAP. Such intraprocedural change underscores the need for targeted, if not continuous, LAP measurement during TMVR to optimize MitraClip placement and mitral regurgitation reduction.

Left atrial dilatation in systolic heart failure: a marker of poor prognosis, not just a buffer between the left ventricle and pulmonary circulation

BACKGROUND

The relation between systolic pulmonary pressure (sPAP) and left atrium in patients with heart failure (HF) is unclear. Diastolic dysfunction, expressed as restrictive mitral filling pattern (RMP), and functional mitral regurgitation (FMR) are associated with both LA enlargement and increased sPAP. We aimed to evaluate whether atrial dilation might modulate the consequences of RMP and FMR on the pulmonary circulation of patients with HF with reduced ejection fraction (HFrEF).

METHODS

1256 HFrEF patients were retrospectively recruited in four Italian centers. Left ventricular (LVD) and atrial (LAD) diameters were measure by m-mode, and EF were measured. RMP was defined as E-wave deceleration time lower than 140 ms. FMR was quantitatively measured. sPAP was evaluated based on maximal tricuspid regurgitant velocity and estimated right atrial pressure.

RESULTS

Final study population was formed by 1005 patients because of unavailability of sPAP in 252 patients. Mean EF was 33 ± 3, 35% had RMP, 67% had mild, and 26% moderate-to-severe FMR. 69% of patients had increased sPAP. A significant association was observed between sPAP and EF, RMP, FMR, and LAD (p < 0.0001 for all). At multivariate analysis, LAD was positively associated with sPAP (p < 0.0001) independently of EF, RMP, and FMR. Analogously, LAD (p < 0.05) was associated with more severe symptoms and worse prognosis after adjustment for LV function and FMR.

CONCLUSION

LA dilation was positively associated with sPAP independently of EF, RMP, and FMR. This highlights that LA size should be considered a marker of the severity of the disease.

Mitral Valve Anatomic Predictors of Hemodynamic Success With Transcatheter Mitral Valve Repair

Background

Mitral regurgitation is a heterogeneous disease. Determining which patients derive optimal outcomes from transcatheter edge‐to‐edge mitral valve repair (TMVR) remains challenging. We sought to determine whether baseline mitral valve anatomic characteristics are predictive of left atrial pressure (LAP) changes during TMVR with MitraClip.

Methods and Results

Consecutive patients with severe mitral regurgitation undergoing TMVR (n=112) underwent continuous intraprocedural LAP monitoring and retrospective echocardiographic analysis for specific mitral anatomic characteristics. Procedural success (optimal LAP reduction) was defined as ≥40% reduction in left atrial V‐wave pressure compared with baseline. Echocardiographic predictors of optimal LAP reduction and increased postprocedure mean diastolic gradient were evaluated. Mean age was 79±14 years, and 36 patients (32%) were women. Primary, mixed, and secondary mitral regurgitation were present in 78 patients (70%), 22 patients (20%), and 12 patients (10%), respectively. Baseline mean LAP and V‐wave were 22±6 and 38±13 mm Hg; after TMVR, these decreased to 19±5 and 27±10 mm Hg, respectively (P<0.0001 for both). Independent predictors of optimal LAP reduction were the presence of a flail scallop, mitral regurgitation localized to a single scallop, and high‐quality 3‐dimensional echocardiographic imaging. Independent predictors of elevated postprocedure mean diastolic gradient were elevated preprocedure mean diastolic gradient, mitral annular calcification, and implantation of multiple clips.

Conclusions

Mitral valve pathoanatomic features, including a flail leaflet and single jet, are predictive of optimal LAP reduction with TMVR. High‐quality 3‐dimensional imaging may help select patients with the highest likelihood of optimal hemodynamic results with TMVR. These data expand current knowledge about patient selection for TMVR and deserve further study in larger cohorts.

Left atrial deformation: Useful index for early detection of cardiac damage in chronic mitral regurgitation

In chronic mitral regurgitation (MR) left atrium is one of the first cardiac structures that is involved in remodeling and ultrastructural changes for a progressive volume overload. Severe left atrial (LA) dilation on echocardiography and new onset of atrial fibrillation in asymptomatic patients with preserved Left Ventricular (LV) function, appeared as a Class IIb recommendation for consideration for surgical mitral valve repair in the actual guidelines. However, before atrial dilatation and dysfunction, several ultrastructural changes appear in the atrial muscle tissue that are difficult to identify with the standard echocardiography. Speckle tracking echocardiography (STE) can analyze LA function: it has been showed that it can indirectly identify structural tissue modifications from excessive atrial effort in the early stages of MR up to the full depression of atrial function in the late stages where there are advanced ultrastructural alterations. This review aims to summarize current knowledge on the role of atrial strain identifying early structural alterations of the atrial tissue in the rising stages of MR considering that Left Atrial Peak Longitudinal Strain (PALS) considered useful parameter for a more extensive evaluation of MR patients.

Role of Left Atrial Reservoir Strain Rate in Left Atrial Remodeling in Severe Mitral Regurgitation

Background:

Impaired left atrial (LA) reservoir deformation has been found to be associated with poor functional capacity and outcomes in severe chronic mitral regurgitation (MR). Among patients with primary MR (valve incompetence due to mitral valve pathology), we focus on Carpentier II classification (prolapse or flail mitral valve) and aim to investigate determinants for decreased LA reservoir deformation and its impact on LA remodeling in severe MR.

Methods:

Among 159 consecutive patients with severe chronic Carpentier II MR (left ventricular ejection fraction ≥ 60%), 55 underwent follow-up echocardiography, which was compared with their baseline study. We used the change of LA volume index as the rapidity of LA remodeling, LA eccentricity index as LA sphericity, and peak LA reservoir strain as well as reservoir strain rate (LASR_R) derived from two-dimensional speckle-tracking echocardiography as LA reservoir function.

Results:

Older age, elongated left atrium, increased LA volume index, as well as reduced left ventricular global longitudinal strain and LA ejection fraction all linked to a poor baseline LASR_R (all p < 0.001). A second echocardiography during a mean follow-up of 15.3 ± 8.3 months revealed an enlarged left atrium (increased interval change of LA volume index; p < 0.001). In multivariate analysis, only the difference between the baseline and follow-up LASR_R values (Δ: LASR_R; odds ratio (OR) 0.037, 95% confidence interval (CI) 0.003–0.496, p = 0.013) predicted accelerated LA remodeling. A poor baseline LASR_R was significantly associated with its profound deterioration during the follow-up period (β: = -0.424, p = 0.002).

Conclusion:

In severe chronic Carpentier II MR, a reduced follow-up LASR_R predicted future accelerated LA remodeling. Patients with a poor baseline LASR_R are at a higher risk of its deterioration.

Left atrial volume and function in dogs with naturally occurring myxomatous mitral valve disease

OBJECTIVE

Myxomatous mitral valve disease (MMVD) induces progressive left atrial (LA) enlargement. The LA modulates left ventricular filling and performance through its reservoir, conduit, and contractile function. Assessment of LA size and function may provide valuable information on the level of cardiac compensation. Left atrial function in dogs with naturally occurring MMVD remains largely unexplored. The objective of this study was to evaluate LA volume and function in dogs with naturally occurring MMVD.

ANIMALS

This prospective study included 205 client-owned dogs of different breeds, 114 healthy dogs, and 91 dogs with MMVD of different disease severities.

METHODS

Using two-dimensional echocardiography, the biplane area-length method was applied to assess LA volume and calculate volumetric indices of LA reservoir, conduit, and contractile function.

RESULTS

Left atrial volume and LA stroke volume increased, whereas LA reservoir and contractile function decreased with increasing disease severity. A maximal LA volume <2.25mL/kg was the optimal cut off identified for excluding congestive heart failure in dogs with chronic MMVD with a sensitivity of 96% and a specificity of 100%. An active LA emptying fraction <24% and/or a LA expansion index <126% were suggestive of congestive heart failure in dogs with chronic MMVD with a sensitivity of 77% and a specificity of 89% and a sensitivity of 82% and a specificity of 82%, respectively.

CONCLUSION

Dogs with MMVD appear to have larger LA volumes with poorer LA function. Deteriorating LA function, characterized by a decreasing reservoir and active contractile function, was evident in dogs with MMVD with increasing disease severity.

Left Atrial Remodeling and Atrioventricular Coupling in a Canine Model of Early Heart Failure With Preserved Ejection Fraction

BACKGROUND

Left atrial (LA) compliance and contractility influence left ventricular stroke volume. We hypothesized that diminished LA compliance and contractile function occur early during the development of heart failure with preserved ejection fraction (HFpEF) and impair overall cardiac performance.

METHODS AND RESULTS

Cardiac magnetic resonance imaging, echocardiography, left ventricular and LA pressure-volume studies, and tissue analyses were performed in a model of early HFpEF (elderly dogs, renal wrap-induced hypertension, exogenous aldosterone; n=9) and young control dogs (sham surgery; n=13). Early HFpEF was associated with LA enlargement, cardiomyocyte hypertrophy, and enhanced LA contractile function (median active emptying fraction 16% [95% confidence interval, 13-24]% versus 12 [10-14]%, P=0.008; end-systolic pressure-volume relationship slope 2.4 [1.9-3.2]mm Hg/mL HFpEF versus 1.5 [1.2-2.2]mm Hg/mL controls, P=0.01). However, atrioventricular coupling was impaired and the curvilinear LA end-reservoir pressure-volume relationship was shifted upward/leftward in HFpEF (LA stiffness constant [β_LA] 0.16 [0.11-0.18]mm Hg/mL versus 0.06 [0.04-0.10]mm Hg/mL controls; P=0.002), indicating reduced LA compliance. Impaired atrioventricular coupling and lower LA compliance correlated with lower left ventricular stroke volume. Total fibrosis and titin isoform composition were similar between groups; however, titin was hyperphosphorylated in HFpEF and correlated with β_LA. LA microvascular reactivity was diminished in HFpEF versus controls. LA microvascular density tended to be lower in HFpEF and inversely correlated with β_LA.

CONCLUSIONS

In early-stage hypertensive HFpEF, LA cardiomyocyte hypertrophy, titin hyperphosphorylation, and microvascular dysfunction occur in association with increased systolic and diastolic LA chamber stiffness, impaired atrioventricular coupling, and decreased left ventricular stroke volume. These data indicate that maladaptive LA remodeling occurs early during HFpEF development, supporting a concept of global myocardial remodeling.

Echocardiographic Assessment of Left Atrial Size and Function in Warmblood Horses: Reference Intervals, Allometric Scaling, and Agreement of Different Echocardiographic Variables

Background

Echocardiographic assessment of left atrial (LA) size and function in horses is not standardized.

Objectives

The aim of this study was to establish reference intervals for echocardiographic indices of LA size and function in Warmblood horses and to provide proof of concept for allometric scaling of variables and for the clinical use of area‐based indices.

Animals

Thirty‐one healthy Warmblood horses and 91 Warmblood horses with a primary diagnosis of mitral regurgitation (MR) or aortic regurgitation (AR).

Methods

Retrospective study. Echocardiographic indices of LA size and function were measured and scaled to body weight (BWT). Reference intervals were calculated, the influence of BWT, age, and valvular regurgitation on LA size and function was investigated and agreement between different measurements of LA size was assessed.

Results

Allometric scaling of variables of LA size allowed for correction of differences in BWT. Indices of LA size documented LA enlargement with moderate and severe MR and AR, whereas most indices of LA mechanical function were not significantly altered by valvular regurgitation. Different indices of LA size were in fair to good agreement but still lead to discordant conclusions with regard to assessment of LA enlargement in individual horses.

Conclusions and Clinical Importance

Allometric scaling of echocardiographic variables of LA size is advised to correct for differences in BWT among Warmblood horses. Assessment of LA dimensions should be based on an integrative approach combining subjective evaluation and assessment of multiple measurements, including area‐based variables. The clinical relevance of indices of LA mechanical function remains unclear when used in horses with mitral or aortic regurgitation.

Early left atrial tissue features in patients with chronic mitral regurgitation and sinus rhythm: Alterations of not remodeled left atria

OBJECTIVE

Left atrial (LA) enlargement, a compensatory mechanism in chronic mitral regurgitation (MR) increasing the risk of atrial fibrillation (AF) and predictive of cardiac events, involves structural alterations. We characterized LA features in patients in sinus rhythm with severe degree of MR, similar degrees of left ventricular remodeling but divergent LA size.

METHODS

Among a consecutive series of 163 patients in stable sinus rhythm undergoing isolated mitral valve surgery for severe non-rheumatic MR, two groups were arbitrarily selected according to their LA size (antero-posterior): NRLA group (non-remodeled LA) included 8 patients with LA≤40mm, RLA group (remodeled LA) included 8 patients with LA>55mm. LA biopsies were processed for paraffin inclusion and sectioning. Fibrosis, cardiomyocytes morphology, capillaries density, cytochrome c and F-actin expression were evaluated by microscopy.

RESULTS

Histology and immunohistochemistry demonstrated alteration of moderate entity: higher amounts of endomysial fibrosis (not of collagen type III) and of hypertrophic cardiomyocytes in RLA than in NRLA. Confocal microscopy displayed focally disorganized F-actin and no nuclear fragmentation in both groups, but more intra-cytoplasm cytochrome c in RLA vs. NRLA, possibly indicative of more successful escape to apoptosis by NRLA cardiomyocytes.

CONCLUSIONS

Our study shows the presence of early cellular and interstitial alterations in LA tissue in patients with chronic MR and sinus rhythm. These features were analogous to those of patients with AF, and suggest that macroscopic remodeling LA in the settings of MR is preceded by structural changes, paving the way to further investigation on the preventive role of early mitral valve repair.

Noninvasive estimation of pulmonary capillary wedge pressure in patients with mitral regurgitation: A speckle tracking echocardiography study

BACKGROUND

Echocardiographic parameters to predict pulmonary capillary wedge pressure (PCWP) in mitral regurgitation (MR) are not yet elucidated. We reported that PCWP could be accurately estimated by novel KT index which is defined as log10[left atrial (LA) emptying function (EF)/LA volume]. We examined the usefulness of the KT index as a predictor of PCWP in primary and secondary MR with sinus rhythm and also MR with atrial fibrillation.

METHODS

LA dimension, strain, volume, EF, and E/e' were measured in moderate to severe MR with sinus rhythm (n=58, age: 67±8 years) and MR with atrial fibrillation (n=24, age: 69±11 years) just before catheterization and in normal subjects (n=26, age: 67±11 years) using speckle tracking echocardiography. MR with sinus rhythm was divided into primary MR (n=27) and secondary MR (n=31). The estimated PCWP (ePCWP) was calculated as 10.8-12.4×KT index.

RESULTS

There was a correlation between PCWP and LA dimension, E/e', minimum LA volume index, active LAEF, total LAEF, or LA strain (r=0.32, r=0.31, r=0.55, r=-0.61, r=-0.51, and r=-0.50, respectively, p<0.05). The better correlation was found between PCWP and ePCWP in MR including both primary and secondary MR and also MR with atrial fibrillation (r=0.70, r=0.67, and r=0.58, respectively, p<0.01). Multiple regression analysis revealed that ePCWP was an independent predictor of PCWP in MR. The ePCWP demonstrated good diagnostic accuracy (area under the curve of 0.86) and sensitivity (81%) and specificity (71%) to predict elevated PCWP >15mmHg using a cut-off of 16mmHg.

CONCLUSION

The ePCWP was the reliable echocardiographic parameter to predict PCWP in primary and secondary MR and might also be useful in MR with atrial fibrillation. The ePCWP may have an incremental value in a clinical setting.

A novel ultrasound predictor of pulmonary capillary wedge pressure assessed by the combination of left atrial volume and function: A speckle tracking echocardiography study

BACKGROUND

We hypothesized that a development of a novel index based on the combination of left atrial volume (LAV) and left atrial (LA) function evaluated by the time-LA volume curve using speckle tracking echocardiography (STE) would be accurate and useful to estimate pulmonary capillary wedge pressure (PCWP). Our goal was to develop a novel index of PCWP based on a combination of LAV and LA function using STE.

METHODS

A cross-validation study was performed with the patients divided into a training study to define the novel index (n=50) and a testing study to validate the index (n=196). PCWP was measured by right heart catheterization, and phasic LAV and emptying function (EF) were measured by STE.

RESULTS

Simple linear regression analysis in the training study revealed that the novel index that best estimated PCWP was the kinetics-tracking index [KT index=log10 (active LAEF/minimum LAV index)]. Multiple regression analysis revealed that the KT index was the most reliable predictor of PCWP. It had the strongest correlation with PCWP (r=-0.86, p<0.001) among all echocardiographic parameters. In the testing study, PCWP estimated by the KT index was also strongly correlated with measured PCWP (r=0.92, p<0.001). These correlations were also strong in the patients with reduced left ventricular ejection fraction (<50%), chronic heart failure, and chronic atrial fibrillation (r=0.92, r=0.91, r=0.79, p<0.001, respectively).

CONCLUSIONS

A novel index (KT index) using a combination of LAV and LA function was a powerful and useful predictor of PCWP and may be valuable in routine clinical practice.

Preoperative left ventricular ejection fraction and left atrium reverse remodeling after mitral regurgitation surgery

Background

Left atrium enlargement has been associated with cardiac events in patients with mitral regurgitation (MR). Left atrium reverse remodeling (LARR) occur after surgical correction of MR, but the preoperative predictors of this phenomenon are not well known. It is therefore important to identify preoperative predictors for postoperative LARR.

Methods

We enrolled 62 patients with chronic severe MR (prolapse or flail leaflet) who underwent successful mitral valve surgery (repair or replacement); all with pre- and postoperative echocardiography. LARR was defined as a reduction in left atrium volume index (LAVI) of ≥25%. Stepwise multiple regression analysis was used to identify independent predictors of LARR.

Results

LARR occurred in 46 patients (74.2%), with the mean LAVI decreasing from 85.5 mL/m² to 49.7 mL/m² (p <0.001). These patients had a smaller preoperative left ventricular systolic volume (p =0.022) and a higher left ventricular ejection fraction (LVEF) (p =0.034). LVEF was identified as the only preoperative variable significantly associated with LARR (odds ratio, 1.086; 95% confidence interval, 1.002–1.178). A LVEF cutoff value of 63.5% identified patients with LARR of ≥25% with a sensitivity of 71.7% and a specificity of 56.3%.

Conclusions

LARR occurs frequently after mitral valve surgery and is associated with preoperative LVEF higher than 63.5%.

Left atrial function in patients with mitral valve regurgitation

The purpose of this study was to assess left atrial (LA) function and myocardial mechanics in patients with degenerative mitral regurgitation (MR). Eighty patients with degenerative MR and twenty control subjects were included prospectively. LA volume (LAV) and right atrial (RA) volume (RAV) were measured with three-dimensional transthoracic echocardiography at three phases of the cardiac cycle as maximal volume (LAVmax and RAVmax), minimal volume (LAVmin and RAVmin), and volume before atrial contraction (LAVpre-A and RAVpre-A). From these volumes, active stroke volume (SV), distensibility, and emptying fraction were calculated. LA strain and strain rate were measured with vector velocity imaging on four- and two-chamber views. Left ventricular (LV) filling pressures were increased in patients with severe MR (E/E': 16 ± 4 vs. 10 ± 3 in control subjects). LAVmax, LAVmin, and LAVpre-A all increased with increasing MR volume. As LAVpre-A increased, both LA total SV (r = 0.68, P < 0.001) and passive filling volume (r = 0.76, P < 0.001) increased. LA active SV increased with LAVpre-A up to a certain point, upon which it decreased despite further increased LAVpre-A (r = 0.53, P < 0.001). LA late negative strain decreased with increasing MR volume. A positive correlation existed between LA late negative strain and LA active emptying fraction (r = 0.55, P < 0.001). In contrast, RA function was comparable between groups. In conclusion, LA contractility (active SV) increased in response to an increase in LA preload (LAVpre-A) up to a point beyond which LA contractility (active SV) decreased. Whether this is due to working of the LA at the descending limb of the Frank-Starling curve or mainly due to changes in afterload still remains unclear.

The three integrated phases of left atrial macrophysiology and their interactions

Our understanding of the left atrium is growing, although there are many aspects that are still poorly understood. The left atrium size as an imaging biomarker has been consistently shown to be a powerful predictor of outcomes and of different cardiovascular disorders, such as, but not limited to, atrial fibrillation, congestive heart failure, mitral regurgitation and stroke. Left atrial function has been conventionally divided into three integrated phases: reservoir, conduit and booster-pump. The highly dynamic left atrium and its response to the stretch and secretion of atrial neuropeptides leaves the left atrium far from being a simple transport chamber. The aim of this review is to provide an understanding of the left atrial physiology and its relation to disorders within the heart.

Left atrial function by two-dimensional speckle-tracking echocardiography in patients with severe organic mitral regurgitation: association with guidelines-based surgical indication and postoperative (long-term) survival

BACKGROUND

Left atrial (LA) mechanics in patients with severe mitral regurgitation (MR) remain largely unexplored. The aim of the present evaluation was to assess the effect of severe MR on LA function, its potential relation with conventional surgical indications, and long-term postoperative survival.

METHODS

Two-dimensional speckle-tracking strain and volumetric indices of LA reservoir, conduit, and contractile function were assessed in 121 patients with severe MR and 70 controls. Patients were divided according to the presence (n = 46) or absence (n = 75) of one or more guidelines-based criteria for mitral surgery (symptoms, left ventricular ejection fraction ≤ 60%, left ventricular end-systolic diameter ≥ 40 mm, atrial fibrillation, or systolic pulmonary arterial pressure >50 mm Hg).

RESULTS

In patients with severe MR compared with controls, significant LA reservoir and contractile dysfunction was observed, which was more pronounced in patients with mitral surgery indication (P < .05 for all strain and volumetric indices). Of all indices of LA function, LA reservoir strain was an independent predictor (odds ratio, 0.88; 95% confidence interval, 0.82-0.94; P < .001) and had the highest accuracy to identify patients with indications for mitral surgery (area under the receiver operating characteristic curve, 0.8; 95% confidence interval, 0.72-0.87). A total of 117 patients underwent mitral valve surgery. Patients with LA reservoir strain ≤24% showed worse survival at a median of 6.4 years (interquartile range, 4.7-8.7 years) after mitral surgery (P = .02), regardless the symptomatic status before surgery. LA reservoir strain, on top of mitral surgery indications, provided incremental predictive value for postoperative survival.

CONCLUSIONS

Impaired LA reservoir strain in patients with severe organic MR relates to long-term survival after mitral valve surgery, independently of and incremental to current guidelines-based indications for mitral surgery.

Left atrial strain and strain rate before and following restrictive annuloplasty for ischaemic mitral regurgitation evaluated by two-dimensional speckle tracking echocardiography

AIMS

We retrospectively evaluated left atrial (LA) strain and strain rate (SR) before and after undersized mitral ring annuloplasty (UMRA) for chronic ischaemic mitral regurgitation (CIMR) with two-dimensional speckle-tracking echocardiography.

METHODS AND RESULTS

Left atrial volumes, LA reservoir, LA conduit, LA contractile phases, and LA ejection fraction (LAEF) were measured in 95 CIMR patients who underwent coronary bypass grafting and UMRA. Left atrial peak global strain (ε), LA reservoir (SRp), LA conduit (SRE), and LA contractile phase (SRA) strain rates were obtained at the baseline and at the follow-up (median 41.5 months, interquartile range 23-61). Based on the recurrence of mitral regurgitation (MR) at the follow-up, the patients were divided into two groups: patients with (group MR+, n = 30) or without (group MR-, n = 65) recurrent MR. Twenty age-and gender-matched healthy adults were controls. In the MR- group, baseline ε (P < 0.001), SRP (P < 0.001), SRE (P < 0.001), and SRA (P < 0.001) were enhanced, while in MR+ group, ε (P < 0.001), SRP (P = 0.03), SRE (P = 0.03), and SRA (P = 0.003) were worse than controls. At the follow-up, none of these indices changed in the MR+ group while all returned to normal values in patients belonging to the MR- group. Left atrial deformation correlated with corresponding volumetric parameters. Furthermore, we found a direct correlation between SRE and early peak diastolic velocity (E) (ρ = 0.52, P = 0.02) and E-wave deceleration time (ρ = 0.50, P = 0.02). Finally, there was a strong correlation between ε, SRP, and SRA (ρ = 0.72, P < 0.001 and ρ = 0.79, P < 0.001, respectively) and SRE (ρ = 0.69, P < 0.001 and ρ = 0.71, P < 0.001, respectively). Finally, ε, SRP, and SRE (all, P < 0.001) were co-factors associated to recurrent MR.

CONCLUSION

Left atrial peak global strain, peak systolic SR, and peak early diastolic SR were cofactors associated to recurrent MR. The assessment of LA strain and SR, in addition to other echocardiographic parameters, can be helpful in detecting patients undergoing UMRA who are unlikely to benefit from annuloplasty.

Comparative effects of amlodipine and benazepril on left atrial pressure in dogs with experimentally-induced mitral valve regurgitation

Background

One of the purposes of treatment for dogs with mitral regurgitation (MR) is lowering left atrial pressure (LAP). There has been few study of the amlodipine in dogs with MR and amlodipine’s effect on LAP has not been fully evaluated in a quantitative manner because of difficulties in directly measuring LAP. The objective of our study was to compare the short-term effects of amlodipine (0.2 mg/kg PO q12h) vs benazepril (0.5 mg/kg PO q12h), on LAP and echocardiographic parameters in five beagle dogs with experimentally-induced MR. LAP of eight dogs that has own control were measured using radiotelemetry system at baseline and again on days 1, 2, 3, 4, 5, 6, 7 of the drug administration.

Results

Mean LAP decreased significantly after amlodipine (11.20 ± 4.19 mmHg vs 14.61 ± 3.81 mmHg at baseline, p < .01) but not after benazepril treatment (13.19 ± 3.47 mmHg, p > .05). LAP was lower after 7 days of amlodipine treatment than after 7 days of benazepril treatment. Significant reduction was seen for the first time 4 days after the administration amlodipine. The rate of the maximal area of the regurgitant jet signals to the left atrium area (ARJ/LAA) of the amlodipine treatment was significantly lower (p < .05) after 7 days compared to baseline. Other echocardiographic parameters did not change significantly.

Conclusions

LAP was significantly decreased after amlodipine treatment in dogs with surgically-induced MR but not after benazepril treatment. Although this study did not focus on adverse effects, amlodipine may be an effective drug for helping the patients with acute onset of severe MR, such as rupture of chordae tendinae or end stage patients were the LAP is likely to be elevated. Additional studies in clinical patients with degenerative mitral valve disease and acute chordal rupture are warranted because the blood-pressure lowering effects of amlodipine can decrease renal perfusion and this can further activate the RAAS.

A single strain-based growth law predicts concentric and eccentric cardiac growth during pressure and volume overload

Adult cardiac muscle adapts to mechanical changes in the environment by growth and remodeling (G&R) via a variety of mechanisms. Hypertrophy develops when the heart is subjected to chronic mechanical overload. In ventricular pressure overload (e.g. due to aortic stenosis) the heart typically reacts by concentric hypertrophic growth, characterized by wall thickening due to myocyte radial growth when sarcomeres are added in parallel. In ventricular volume overload, an increase in filling pressure (e.g. due to mitral regurgitation) leads to eccentric hypertrophy as myocytes grow axially by adding sarcomeres in series leading to ventricular cavity enlargement that is typically accompanied by some wall thickening. The specific biomechanical stimuli that stimulate different modes of ventricular hypertrophy are still poorly understood. In a recent study, based on in-vitro studies in micropatterned myocyte cell cultures subjected to stretch, we proposed that cardiac myocytes grow longer to maintain a preferred sarcomere length in response to increased fiber strain and grow thicker to maintain interfilament lattice spacing in response to increased cross-fiber strain. Here, we test whether this growth law is able to predict concentric and eccentric hypertrophy in response to aortic stenosis and mitral valve regurgitation, respectively, in a computational model of the adult canine heart coupled to a closed loop model of circulatory hemodynamics. A non-linear finite element model of the beating canine ventricles coupled to the circulation was used. After inducing valve alterations, the ventricles were allowed to adapt in shape in response to mechanical stimuli over time. The proposed growth law was able to reproduce major acute and chronic physiological responses (structural and functional) when integrated with comprehensive models of the pressure-overloaded and volume-overloaded canine heart, coupled to a closed-loop circulation. We conclude that strain-based biomechanical stimuli can drive cardiac growth, including wall thickening during pressure overload.

Echocardiographic evaluation of the left atrium of healthy dogs using the conventional M-mode and the bidimensional mode

The left atrium (LA) was evaluated through the bidimensional method (2-D) (short axis) and the relation left atrium:aorta (LA:Ao) in a group of 40 healthy adult dogs between 1.5 and 7 years of age and weights ranging from 3.2 to 38.3kg, and these values were compared to those in the conventional M-mode. Comparing the variable LA and Ao with the two methods and their respective indexes, significant statistical difference was observed (P<0,001), high positive correlation between the weight and LA-2D and LAM, between body surface and LA-2D and LAM. A difference between LA and Ao in both methods and these respective indicators were observed. The association was higly positive between weight and body surface area (BSA) and between M- mode LA (LAM) and 2-D mode LA (LA-2D). No correlation was observed between these indicators and weight and BSA, in both methods, so these indicators are weight and BSA-independent. Conclusions: LA-2D is bigger than LAM, the LA-2D:Ao-2D average index is 1,379 and the confidence interval is 1,337 to 1,422. The index in the 2-D method is, therefore, superior to the index in the M-mode.

Left atrial eccentricity in chronic mitral regurgitation: relation to left atrial function

AIMS

The aim of this study was to assess the changes in the left atrial (LA) shape and to identify the determinants of these changes in chronic mitral regurgitation (MR).

METHODS AND RESULTS

We enrolled 125 consecutive patients (56 ± 16 years, 51% men) with chronic MR caused by myxomatous mitral valve disease in sinus rhythm and 45 control patients (54 ± 15 years, 55% men) undergoing transthoracic Doppler echocardiography. The LA eccentricity index (LAEi) and the LA volume index (LAVi) were used to estimate the LA shape and size, respectively. There were significant decreases in LAEi (r= -0.723, P< 0.001) and increases in LAVi (r= 0.642, P< 0.001) with increasing severity of MR. In multivariate stepwise linear regression analysis, regurgitant fraction (RF) was an independent determinant of the LAE, whereas RF, left ventricular (LV) mass index and LV diastolic dysfunction grade were independent determinants of the LA volume. The LAEi was positively related to the velocity of A' in the entire population (r = 0.238, P = 0.002). On the receiver operating characteristic (ROC) curve analysis, LAEi ≤1.30 was the best cut-off value to reflect the LA systolic dysfunction (A' velocity <7 cm/s; area under the curve was 0.78, P < 0.001).

CONCLUSION

LA becomes more spherical with increasing severity of MR, suggesting a decrease in LAE, which is mainly determined by the volume overload. LAE might be closely related to the LA systolic function in chronic MR.

How should we measure left atrium size and function?

Echocardiographic assessment of left atrial size from M-mode or 2D echocardiography measurements has been used in clinical and research studies for years, but its accuracy is now questioned. New techniques, such as 3D and tissue Doppler imaging, assessing velocities, strain and strain rate, provide improved prognostic value in a wide range of diseases. 2D strain imaging using speckle tracking on B-mode images may yield even better, angle-independent, results than tissue Doppler imaging-derived strain echocardiography. Finally, velocity vector imaging is a novel image analysis technique that may be used to quantify left atrial volume.

Survival characteristics and prognostic variables of dogs with preclinical chronic degenerative mitral valve disease attributable to myxomatous degeneration

BACKGROUND

Preclinical myxomatous mitral valve degeneration (MMVD) includes a heterogeneous group of dogs. Therefore, identifying risk factors for progression of the disease is of clinical importance.

OBJECTIVES

To investigate survival time and risk factors for clinical and echocardiographic variables taken at initial examination for clinical progression in preclinical MMVD dogs.

ANIMALS

A total of 256 dogs with stage B1 or B2 MMVD.

MATERIALS AND METHODS

Medical records of 256 dogs with preclinical MMVD were reviewed retrospectively. Long-term outcome was assessed by telephone interview. Dogs alive at the time of phone interview were asked to return to the hospital for re-evaluation of their cardiac status.

RESULTS

Seventy of 256 (27.3%) dogs died during the observation period. The median survival time, regardless of cause of death, was 588 (range 75-1,668) days. The presence of a murmur was associated with an increased risk of death (AHR 2.14; 95% CI 1.12, 4.11; P = 0.022). Thirty (12%) deaths were considered cardiac related. LA/Ao > 1.4 was the only negative predictor (AHR 2.64; 1.13, 6.13; P = 0.024) for cardiac-related deaths. Eighty-three dogs were re-examined, of which 34 progressed to a more advanced stage of MMVD. The presence of Emax > 1.2 (AHR 2.75; 95% CI 1.01, 7.48; P = 0.047) and cough (AHR 7.89; 95% CI 3.18, 20.07; P < 0.001) were significant in the multivariate analysis.

CONCLUSIONS AND CLINICAL IMPORTANCE

Preclinical MMVD represents a relatively benign condition in dogs. Clinicians might find stratification of this dog population according to risk factors based on clinical and echocardiographic findings helpful in determining treatment.

Atrioventricular reverse remodeling after valve repair for chronic severe mitral regurgitation: 1-year follow-up

BACKGROUND

Chronic severe mitral regurgitation is associated with poor clinical outcome because chronic volume overload leads to hemodynamic changes and left ventricular and left atrial remodeling. Few data are available regarding left atrial volume index regression (LAVIR) and left ventricular mass index regression (LVMIR) after valve surgery for mitral regurgitation. We aimed to identify predictive correlates of LAVIR and LVMIR and to assess the relationship between these regressions.

HYPOTHESIS

Volume overload in chronic severe mitral regurgitation may influence left atrial and ventricular remodeling and reverse remodeling.

METHODS

Eighty-five patients who underwent valve repair for severe chronic mitral regurgitation were consecutively enrolled. Plasma N-terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP) and echocardiographic measurements were performed before surgery, before discharge, and at 12 months after surgery. LAVIR and LVMIR were assessed using serial echocardiography.

RESULTS

There were significant decreases in left ventricular mass index (LVMI; from 125.9 ± 31.3 g/m² to 94.8 ± 28.6 g/m², P = 0.001) and left atrial volume index (LAVI; from 75.3 ± 33.5 mL/m² to 41.7 ± 16.0 mL/m², P = 0.001) after surgery. Preoperative LAVI positively correlated with preoperative LVMI (r = 0.437, P = 0.001) and LAVIR positively correlated with LVMIR (r = 0.347, P = 0.001). In multivariate stepwise linear regression analysis, preoperative LAVI, age, hypertension, and atrial fibrillation were independently predictive of LAVIR, and preoperative LVMI, hypertension, and NT-proBNP were independently predictive of LVMIR.

CONCLUSIONS

Volume overload in chronic severe mitral regurgitation may influence left ventricular remodeling and reverse remodeling, as well as left atrial remodeling and reverse remodeling. Preoperative lower LAVI, younger age, absence of hypertension, and absence of atrial fibrillation may predict LAVIR, and preoperative lower LVMI, lower NT-proBNP levels, and absence of hypertension may predict LVMIR after surgery for chronic severe mitral regurgitation.