Mechanism of ischemic mitral regurgitation with segmental left ventricular dysfunction: three-dimensional echocardiographic studies in models of acute and chronic progressive regurgitation

OBJECTIVES

This study aimed to separate proposed mechanisms for segmental ischemic mitral regurgitation (MR), including left ventricular (LV) dysfunction versus geometric distortion by LV dilation, using models of acute and chronic segmental ischemic LV dysfunction evaluated by three-dimensional (3D) echocardiography.

BACKGROUND

Dysfunction and dilation-both mechanisms with practical therapeutic implications-are difficult to separate in patients.

METHODS

In seven dogs with acute left circumflex (LCX) coronary ligation, LV expansion was initially restricted and then permitted to occur. In seven sheep with LCX branch ligation, LV expansion was also initially limited but became prominent with remodeling over eight weeks. Three-dimensional echo reconstruction quantified mitral apparatus geometry and MR volume.

RESULTS

In the acute model, despite LV dysfunction with ejection fraction = 23 +/- 8%, MR was initially trace with limited LV dilation, but it became moderate with subsequent prominent dilation. In the chronic model, MR was also initially trace, but it became moderate over eight weeks as the LV dilated and changed shape. In both models, the only independent predictor of MR volume was increased tethering distance from the papillary muscles (PMs) to the anterior annulus, especially medial and posterior shift of the ischemic medial PM, measured by 3D reconstruction (r2 = 0.75 and 0.86, respectively). Mitral regurgitation volume did not correlate with LV ejection fraction or dP/dt.

CONCLUSIONS

Segmental ischemic LV contractile dysfunction without dilation, even in the PM territory, fails to produce important MR. The development of MR relates strongly to changes in the 3D geometry of the mitral apparatus, with implications for approaches to restore a more favorable configuration.

Design of a new surgical approach for ventricular remodeling to relieve ischemic mitral regurgitation: insights from 3-dimensional echocardiography

BACKGROUND

Mechanistic insights from 3D echocardiography (echo) can guide therapy. In particular, ischemic mitral regurgitation (MR) is difficult to repair, often persisting despite annular reduction. We hypothesized that (1) in a chronic infarct model of progressive MR, regurgitation parallels 3D changes in the geometry of mitral leaflet attachments, causing increased leaflet tethering and restricting closure; therefore, (2) MR can be reduced by restoring tethering geometry toward normal, using a new ventricular remodeling approach based on 3D echo findings.

METHODS AND RESULTS

We studied 10 sheep by 3D echo just after circumflex marginal ligation and 8 weeks later. MR, at first absent, became moderate as the left ventricle (LV) dilated and the papillary muscles shifted posteriorly and mediolaterally, increasing the leaflet tethering distance from papillary muscle tips to the anterior mitral annulus (P<0.0001). To counteract these shifts, the LV was remodeled by plication of the infarct region to reduce myocardial bulging, without muscle excision or cardiopulmonary bypass. Immediately and up to 2 months after plication, MR was reduced to trace-to-mild as tethering distance was decreased (P<0.0001). LV ejection fraction, global LV end-systolic volume, and mitral annular area were relatively unchanged. By multiple regression, the only independent predictor of MR was tethering distance (r(2)=0.81).

CONCLUSIONS

Ischemic MR in this model relates strongly to changes in 3D mitral leaflet attachment geometry. These insights from quantitative 3D echo allowed us to design an effective LV remodeling approach to reduce MR by relieving tethering.

Three-dimensional echocardiographic assessment of left ventricular wall motion abnormalities in mouse myocardial infarction

We applied 3-dimensional echocardiographic reconstruction to assess left ventricular (LV) volumes, function, and the extent of wall motion abnormalities in a murine model of myocardial infarction (MI). Consecutive parasternal short-axis planes were obtained at 1-mm intervals with a 13-MHz linear array probe. End-diastolic and end-systolic LV volumes were calculated by Simpson's rule, and the ejection fraction and cardiac output were derived. Echocardiography-derived cardiac output was validated by an aortic flow probe in 6 mice. Echocardiography was then performed in 9 mice before and after the left anterior descending coronary artery was ligated. Wall motion was assessed, and the ratio of the abnormally to normally contracting myocardium was calculated. After MI occurred, LV end-diastolic volume and LV end-systolic volume increased (33 +/- 10 vs 24 +/- 6 microL, P <.05 and 24 +/- 9 vs 10 +/- 4 microL, P <.001), whereas cardiac output decreased (4.2 +/- 1.5 mL/min vs 6.6 +/- 2.3 mL/min, P <.01). Forty percent of the myocardium was normokinetic, 24% was hypokinetic, and 36% was akinetic. Echocardiography can measure LV volumes and regional and global function in a murine model of myocardial infarction, thereby providing the potential to quantitate and compare the responses of various transgenic mice to MI and its therapies.

Determination of right ventricular structure and function in normoxic and hypoxic mice: a transesophageal echocardiographic study

BACKGROUND

Noninvasive cardiac evaluation is of great importance in transgenic mice. Transthoracic echocardiography can visualize the left ventricle well but has not been as successful for the right ventricle (RV). We developed a method of transesophageal echocardiography (TEE) to evaluate murine RV size and function.

METHODS AND RESULTS

Normoxic and chronically hypoxic mice (F(IO2)=0.11, 3 weeks) and agarose RV casts were scanned with a rotating 3.5F/30-MHz intravascular ultrasound probe. In vivo, the probe was inserted in the mouse esophagus and withdrawn to obtain contiguous horizontal planes at 1-mm intervals. In vitro, the probe was withdrawn along the left ventricular posterior wall of excised hearts. The borders of the RV were traced on each plane, allowing calculation of diastolic and systolic volumes, RV mass, RV ejection fraction, stroke volume, and cardiac output. RV wall thickness was measured. Echo volumes obtained in vitro were compared with cast volumes. Echo-derived cardiac output was compared with measurements of an ascending aortic Doppler flow probe. Echo-derived RV free wall mass was compared with true RV free wall weight. There was excellent agreement between cast and TEE volumes (y=0.82x+6.03, r=0.88, P<0.01) and flow-probe and echo cardiac output (y=1.00x+0.45, r=0.99, P<0.0001). Although echo-derived RV mass and wall thickness were well correlated with true RV weight, echo-derived RV mass underestimated true weight (y=0.53x+2.29, r=0.81, P<0.0001). RV mass and wall thickness were greater in hypoxic mice than in normoxic mice (0.78+/-0.19 versus 0.51+/-0.14 mg/g, P<0.03, 0.50+/-0.03 versus 0.38+/-0.03 mm, P<0.04).

CONCLUSIONS

TEE with an intravascular ultrasound catheter is a simple, accurate, and reproducible method to study RV size and function in mice.

Echocardiographic determination of risk area size in a murine model of myocardial ischemia

Genetically altered mice are useful to understand cardiac physiology. Myocardial contrast echocardiography (MCE) assesses myocardial perfusion in humans. We hypothesized it could evaluate murine myocardial perfusion before and after acute coronary ligation. MCE was performed before and after this experimental myocardial infarction (MI) in anesthetized mice by intravenous injection of contrast microbubbles and transthoracic echo imaging. Time-video intensity curves were obtained for the anterior, lateral, and septal myocardial walls. After MI, MCE defects were compared with the area of no perfusion measured by Evans blue staining. In healthy animals, intramyocardial contrast was visualized in all the cardiac walls. The anterior wall had a higher baseline video intensity (53 +/- 17 arbitrary units) than the lateral (34 +/- 13) and septal (27 +/- 13) walls (P < 0.001) and a lower increase in video intensity after contrast injection [50 +/- 17 vs. 60 +/- 24 (lateral) and 65 +/- 29 (septum), P < 0.01]. After MI, left ventricular (LV) dimensions were enlarged, and the shortening fraction was decreased. A perfusion defect was imaged with MCE in every mouse, with a correlation between MCE perfusion defect size (35 +/- 13%) and the nonperfused area by Evans blue (37 +/- 16%, y = 0.77x + 6.1, r = 0.93, P < 0. 001). Transthoracic MCE is feasible in the mouse and can accurately detect coronary occlusions and quantitate nonperfused myocardium.

Myocardial perfusion and wall motion in infarction border zone: assessment by myocardial contrast echocardiography

Several mechanisms have been proposed to explain the decreased wall motion (WM) at the borders of myocardial infarction (MI). We used myocardial contrast echocardiography (MCE) to investigate the relation of perfusion to WM in infarcted border zones (BZs) 6 weeks after MI in 5 sheep. After quantifying the extent of WM abnormality and the perfusion defect, normal (NL), infarcted, and BZs were defined. Peak intensity after contrast was measured in acoustic units (AU). Radiolabeled microspheres were injected to measure regional blood flow. The heart was stained with 2,3, 5-triphenyltetrazolium chloride (TTC). The perfusion defect on MCE was 33% +/- 7% of the total myocardial area and correlated well with TTC (r = 0.92, P <.03). The BZ was 8% +/- 5% of the total myocardial area. Peak intensity after contrast was decreased in MI compared with BZ and NL (MI: 2.5 +/- 1.9 AU, BZ: 8.0 +/- 3.8 AU, P <.005; NL: 10.2 +/- 6.9 AU, P <.02) and comparable in NL and BZ. The blood flow measured by microspheres was not different in NL and BZ but was decreased in MI (NL: 1.6 mL/g/min, BZ: 1.5 +/- 0.5 mL/g/min, MI: 0.7 +/- 0.5 mL/g/min; P <.0001). In this model of chronic ovine MI, the BZ was small and its perfusion was preserved. These findings support the hypothesis that tethering of normal myocardial segments explains the abnormal wall motion noted at the borders of MI.

Kingella endocarditis and meningitis in a patient with SLE and associated antiphospholipid syndrome

We describe a patient with SLE and antiphospholipid syndrome who presented with severe headache and fever. Lumbar puncture analyses indicated meningitis. Kingella kingae was isolated from her blood cultures. A large mobile vegetation was seen on her mitral valve. The association between SLE, Libman-Sacks endocarditis and bacterial endocarditis is discussed.

Dynamic holographic imaging of the beating human heart

Background--Currently, the reporting and archiving of echocardiographic data suffer from the difficulty of representing heart motion on printable 2-dimensional (2D) media. Methods and Results--We studied the capability of holography to integrate motion into 2D echocardiographic prints. Images of normal human hearts and of a variety of mitral valve function abnormalities (mitral valve prolapse, systolic anterior motion of the mitral leaflets, and obstruction of the mitral valve by a myxoma) were acquired digitally on standard echocardiographic machines. Images were processed into a data format suitable for holographic printing. Angularly multiplexed holograms were then printed on a prototype holographic "laser" printer, with integration of time in vertical parallax, so that heart motion became visible when the hologram was tilted up and down. The resulting holograms displayed the anatomy with the same resolution as the original acquisition and allowed detailed study of valve motion with side-by-side comparison of normal and abnormal findings. Comparison of standard echocardiographic measurements in original echo frames and corresponding hologram views showed an excellent correlation of both methods (P<0.0001, r2=0.979, mean bias=2.76 mm). In this feasibility study, both 2D and 3D holographic images were produced. The equipment needed to view these holograms consists of only a simple point-light source. Conclusions--Holographic representation of myocardial and valve motion from echocardiographic data is feasible and allows the printing on a 2D medium of the complete heart cycle. Combined with the recent development of online holographic printing, this novel technique has the potential to improve reporting, visualization, and archiving of echocardiographic imaging.

Dobutamine stress echocardiography in women with systemic lupus erythematosus: increased occurrence of left ventricular outflow gradient

Dobutamine stress echocardiography (DSE) is an accurate noninvasive test used for the diagnosis and evaluation of patients with known or suspected coronary artery disease (CAD). The aim of this study was to determine the rate of positive findings in DSE, to define the echocardiographic and clinical characteristics of women with systemic lupus erythematosus (SLE) and to evaluate the safety of DSE in SLE patients. Thirty consecutive SLE patients were enrolled in the study and underwent DSE study. The mean age of patients was 44 years (range 20-76). Mean duration of SLE was 8.1 years and mean SLEDAI was 5.5. None of the DSE tests performed were positive for myocardial ischaemia. A left ventricular outflow gradient (LVOG) was found in 15/28 (54%) patients who completed the test, a result higher than the reported 20% prevalence of this finding in the literature. There were no significant differences in baseline characteristics between patients who developed a gradient and patients in whom a gradient was not found. There were no significant adverse effects during the study. In the general population, LVOG has been reported to be associated with an increased rate of chest discomfort and with a significantly lower prevalence of CAD. Whether this is true for SLE patients requires further study.

Does global longitudinal strain predict long-term outcome in patients presenting to the emergency department with chest pain?

Funding Acknowledgements

Type of funding sources: None.

Background

 Two-Dimensional Strain for Diagnosing Chest Pain in the Emergency Room (2DSPER) was a prospective multicenter study designed to determine whether 2D longitudinal strain (2DLS) can assist in triage of patients with chest pain in the emergency department (ED). In that study 2DLS was not useful to rule out acute coronary syndromes (ACS) in the ED, partly because many patients without ACS had abnormal 2DLS. The prognostic significance of 2DLS in these patients is unclear.

The aim of the current study was to determine whether global longitudinal strain (GLS), measured using 2D echocardiography in the ED, can predict long-term outcome.

Methods

 Long-term (median 7.7 years [IQR 6.7-8.2]) major adverse cardiac events (MACE; cardiac death, ACS, revascularization, hospitalization for heart failure or atrial fibrillation) was available in 525 of 605 patients (87%) enrolled in the 2DSPER study. The study prospectively enrolled patients presenting to the ED with chest pain and suspected ACS but without a diagnostic ECG or elevated troponin. Global longitudinal strain (GLS) was computed from echocardiograms performed within 24 hours of chest pain using a dedicated 2DLS software (EchoPAC SW; GE Vingmed Ultrasound AS). MACE of patients with worse GLS (&gt;median) was compared to those with better GLS (≤median).

Results

 Median GLS was -18.8%. MACE occurred in 43/249 (17.3%) of patients with worse GLS (-16.8 ± 1.5) as compared with 49/276 (17.8%) with better GLS (-20.8 ± 1.6), HR 0.98 (95%CI 0.65-1.4, p = 0.9) (Figure). Similarly, there was no significant difference in total mortality (6% vs. 4.7%, p = 0.5), cardiac death (0.4% vs. 0.7%, p = 0.6), ACS (8% vs. 8.3%, p = 1), revascularization (10% vs. 10.9%, p = 0.8), hospitalization for heart failure (0.8% vs. 2.2%, p = 0.2) or atrial fibrillation (3.6% vs. 4.3%, p = 0.7) between groups. Predictors of MACE were male gender (HR 2.5, 1.4-4.3, p = 0.02), history of coronary artery disease (HR 3.3, 2-5.4, p &lt; 0.0001) and hypertension (HR 1.8, 1.2-2.8, p = 0.005), but not GLS (HR 0.98, 0.7-1.5, p = 0.9).

Conclusions

 GLS did not predict long term outcome in patients presenting to the ED with chest pain. Long-term outcome was favorable in the group of patients with worse GLS, similar to better GLS.

Abstract Figure.

Prognostic value of incidental finding of pulmonary hypertension detected by echocardiography in patients without known cardiovascular or pulmonary disease

Funding Acknowledgements

Type of funding sources: None.

Introduction

The estimated overall prevalence of pulmonary hypertension (PHT) is ∼1% in the global population, and up to 10% among patients older than 65 years. PHT is associated with a worst prognosis in patients with cardiovascular or pulmonary disease. However, the significance of PHT as an incidental finding among subjects who do not suffer from cardiac or pulmonary diseases is unknown. The aim of our study is to examine whether incidental diagnosis of PHT in patients without cardiovascular or pulmonary comorbidity is associated with long-term all-cause mortality.

Methods

This retrospective cohort study included 8296 patients (58% females, mean age, 63 ± 14 years), who performed a first echo study (echo 1) in the years 2006-2009 and a follow up study (echo 2) until 01/2020 in a large single center echo-lab. Patients were excluded if they had evidence of moderate or more left ventricular dysfunction (LVD), significant valvular disease or diagnosis of pulmonary disease at echo 1. The association between PHT and LV function degree (Ejection fraction above or below 55%) to all-cause mortality was examined between four groups [group 1 (G1)- normal LV function (NLV)+ no PTH (NPH), G2- LVD and NPH, G3- NLV and PHT, G4- LVD and PHT] using a Kaplan-Meier analysis and Cox proportional-hazards model, accounting for various covariates.

Results

Survival time of patients with or without PHT in echo 1 and LV function status at echo 2 was found significantly different among all groups (Pv &lt; 0.001 for all comparisons) (Figure 1). Patients in G1 had the longest mean survival time (141 ± 23 months) compared to any other group (G2-134 ± 30 months, G3-129 ± 32 months, G4-119 ± 38 months). In the multivariable analysis conducted (Table 1), PHT adjusted for various demographic factors and comorbidities was found to be an independent risk factor for long term all-cause mortality with increased risk of up to 34% (adjusted HR-1.34; 95% CI: 1.21-1.47, PV &lt; 0.001).

Conclusion

Incidental finding of PHT in patients without known cardiovascular or pulmonary disease is an independent risk factor for long term all-cause mortality. Future studies should be conducted to assess the impact of an early diagnosis on all-cause mortality, and the need for further diagnostic and therapeutic steps. Abstract Figure.  Abstract Figure.

A novel artificial intelligence-based system provides global longitudinal strain automatically behind the scenes

Funding Acknowledgements

Type of funding sources: None.

Background

Global longitudinal strain (GLS) evaluation is an essential part of echocardiography studies and is indicated in many clinical situations. It is most frequently undertaken using software available on an ultrasound (US) device or on a dedicated workstation. Evaluating GLS is time-consuming because it requires selection of 3 apical views with sufficient image quality. In addition, the software for strain evaluation varies between vendors and may provide different results. LVivo Seamless (DiA Imaging Analysis) is a novel artificial intelligence (AI) based vendor neutral solution that performs automated evaluation of US exams in DICOM format on the server without user involvement. The system selects the optimal views, performs the evaluation, and sends the results to the PACS, providing a novel workflow (Fig.1).

Purpose

To evaluate the ability of LVivo Seamless to automatically identify 4 chamber (4CH), 2 chamber (2CH) and 3 chamber (3CH) views and to compare the automated GLS results based on these 3 views, to GLS results calculated by the routinely used method.

Methods

100 full echo examinations for which GLS was previously calculated by Automated Functional Imaging (AFI, GE Healthcare) were retrospectively collected from Soroka University Medical center. The examinations were processed by LVivo Seamless. The 4CH, 2CH and 3CH views were automatically recognised by the system and the optimal views for evaluation were selected according to quality and depth criteria. A GLS result was only possible if all three views were selected by the system. The automatically calculated GLS values were compared to those reported by AFI.

Results

LV function was impaired in 48% (21% severe, 14% moderate, 13% mild). Moderate or severe valvular heart disease was found in 17%. 13% of the studies included patients receiving chemotherapy. 28% of the patients had normal GLS (GLS&lt;-18%). LVivo Seamless successfully identified the 3 apical views in 95% of the studies. In 2 cases the identified views did not pass the system’s criteria. Of 93 cases available for analysis, fully automated GLS calculation was possible in 87 cases. Excellent correlation was found between GLS by AFI and GLS by LVivo Seamless with r = 0.88 [95% CI: 0.82-0.91]. The average difference and limits of agreements were -1.4 ± 3.9%. The specificity and sensitivity using a normal\abnormal threshold of -18% were 0.9 and 0.83 respectively (Fig.2).

Conclusions

The results provided by the AI based LVivo Seamless solution showed excellent capability to automatically identify 4CH, 2CH and 3CH views, along with excellent GLS results compared to AFI. LVivo Seamless has the potential to improve echocardiography workflow by making the results available to the cardiologist when starting the study review and in the future may become the standard method for strain evaluation. Abstract Figure. Fig.1 Seamless Workflow  Abstract Figure. Fig.2 GLS by LVivo Seamless vs AFI