Left Ventricular Pressure-Strain-Derived Myocardial Work at Rest and during Exercise in Patients with Cardiac Amyloidosis

Evolution and prognostic value of left ventricular deformation and myocardial work parameters in transthyretin amyloid cardiomyopathy

AIMS

Wild-type transthyretin amyloid cardiomyopathy (ATTR-CM) is an increasingly recognized condition. It remains challenging to estimate the extent of disease and the prognosis for most patients. Myocardial work is a sensitive echocardiographic approach that improves the characterization of myocardial damage. We investigate the parameters of myocardial deformation and work in ATTR-CM patients and their changes over time.

METHODS AND RESULTS

We analysed clinical, electrocardiographic, biological, and echocardiographic characteristics in 113 patients [median age 82 (77-85), 90.4% male] diagnosed with wild-type ATTR-CM based on international consensus at a single centre. We compared the data at baseline and 18-month follow-up. Thirty-four patients died and 12 were hospitalized for heart failure at a median follow-up of 935 days (interquartile range 691-1159 days). Left ventricular end-diastolic diameter, left atrial strain during reservoir phase (LASRES), left ventricular longitudinal strain, global work index (GWI), global constructive work significantly decreased from baseline to 18 months, while left ventricular wall thickness increased. Left ventricular ejection fraction, right ventricular free wall strain (FWS), global wasted work (GWW), and global work efficiency did not alter significantly. Strain parameters were identified as prognostic on baseline evaluation using a multivariate analysis: GWI, GWW, FWS, and LASRES. They were significantly associated with the risk of death and hospitalization for heart failure.

CONCLUSION

Multi-chamber strain assessment may improve the surveillance of patients with ATTR-CM, and myocardial work parameters may improve clinical risk stratification in this population.

Evaluation of subclinical left ventricular myocardial systolic dysfunction in type 2 diabetes mellitus patients with and without diabetes peripheral neuropathy by global myocardial work

AIMS

Speckle-tracking echocardiography can non-invasively estimate myocardial work (MW) to evaluate left ventricular (LV) myocardial systolic function. The present study evaluated whether MW may detect subclinical LV myocardial systolic dysfunction in type 2 diabetes mellitus (T2DM) patients with and without diabetes peripheral neuropathy (DPN).

METHODS

A total of 127 T2DM patients were included in the present study, including 67 T2DM patients with DPN. In addition, 73 sex- and age- matched healthy individuals served as normal controls. The global myocardial work index (GWI), global constructive work (GCW), global waste work (GWW), global positive work (GPW), global negative work (GNW), global work efficiency (GWE) and GCW/GWW were measured and analysed. Furthermore, the differences in MW parameters among normal controls, T2DM patients, and T2DM patients with DPN were analysed. Multiple regression models were built to explore for the independent influencing factors of GWI and GPW values in T2DM patients with DPN. Receiver operating characteristic curve analysis was performed to evaluate the sensitivity and specificity of MW in evaluating subclinical LV myocardial systolic dysfunction in T2DM patients with DPN.

RESULTS

The GWI, GCW and GPW of T2DM patients with DPN were significantly decreased compared with those of T2DM patients and normal controls (P < 0.001) and showed a significant decreasing trend overall (P trend < 0.001). GWE and GCW/GWW were significantly decreased in T2DM patients with DPN compared with normal controls (P < 0.05). Although GWW was not significantly different among the three groups, it showed an increasing trend (Ptrend = 0.033). High-density lipoprotein cholesterol (HDL-C) levels were independent influencing factor for decreased GWI (β = 0.21, P = 0.031) and GPW (β = 0.19, P = 0.043) values in T2DM patients with DPN. The combination of the GWI, GCW, GWE, GPW and GCW /GWW had good sensitivity (62.69%) and specificity (89.04%) when evaluating subclinical LV myocardial systolic dysfunction in T2DM patients with DPN.

CONCLUSIONS

Non-invasive evaluation of LV myocardial work can detect subclinical LV myocardial systolic dysfunction in T2DM patients with and without DPN. DPN has additive deleterious effects on LV myocardial systolic function in T2DM patients. The reduction of HDL-C levels may indicate the occurrence of subclinical LV myocardial systolic dysfunction in T2DM patients with DPN.

Echocardiographic Myocardial Work: A Novel Method to Assess Left Ventricular Function in Patients with Coronary Artery Disease and Diabetes Mellitus

Myocardial ischemia caused by coronary artery disease (CAD) and the presence of metabolic abnormalities and microvascular impairments detected in patients with diabetes mellitus (DM) are a common cause of left ventricular (LV) dysfunction. Transthoracic echocardiography is the most-used, non-invasive imaging method for the assessment of myocardial contractility. The accurate evaluation of LV function is crucial for identifying patients who are at high risk or may have worse outcomes. Myocardial work (MW) is emerging as an alternative tool for the evaluation of LV systolic function, providing additional information on cardiac performance when compared to conventional parameters such as left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS) because it incorporates deformation and load into its analysis. The potential of MW in various conditions is promising and it has gained increased attention. However, larger studies are necessary to further investigate its role and application before giving an answer to the question of whether it can have widespread implementation into clinical practice. The aim of this review is to summarize the actual knowledge of MW for the analysis of LV dysfunction caused by myocardial ischemia and hyperglycemia.

Position Statement on the Use of Myocardial Strain in Cardiology Routines by the Brazilian Society of Cardiology's Department Of Cardiovascular Imaging - 2023

Central Illustration : Position Statement on the Use of Myocardial Strain in Cardiology Routines by the Brazilian Society of Cardiology's Department Of Cardiovascular Imaging - 2023 Proposal for including strain in the integrated diastolic function assessment algorithm, adapted from Nagueh et al.67 Am: mitral A-wave duration; Ap: reverse pulmonary A-wave duration; DD: diastolic dysfunction; LA: left atrium; LASr: LA strain reserve; LVGLS: left ventricular global longitudinal strain; TI: tricuspid insufficiency. Confirm concentric remodeling with LVGLS. In LVEF, mitral E wave deceleration time < 160 ms and pulmonary S-wave < D-wave are also parameters of increased filling pressure. This algorithm does not apply to patients with atrial fibrillation (AF), mitral annulus calcification, > mild mitral valve disease, left bundle branch block, paced rhythm, prosthetic valves, or severe primary pulmonary hypertension.

Cardiac amyloidosis and aortic stenosis: a state-of-the-art review

Cardiac amyloidosis is caused by the extracellular deposition of amyloid fibrils in the heart, involving not only the myocardium but also any cardiovascular structure. Indeed, this progressive infiltrative disease also involves the cardiac valves and, specifically, shows a high prevalence with aortic stenosis. Misfolded protein infiltration in the aortic valve leads to tissue damage resulting in the onset or worsening of valve stenosis. Transthyretin cardiac amyloidosis and aortic stenosis coexist in patients > 65 years in about 4-16% of cases, especially in those undergoing transcatheter aortic valve replacement. Diagnostic workup for cardiac amyloidosis in patients with aortic stenosis is based on a multi-parametric approach considering clinical assessment, electrocardiogram, haematologic tests, basic and advanced echocardiography, cardiac magnetic resonance, and technetium labelled cardiac scintigraphy like technetium-99 m (99mTc)-pyrophosphate, 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid, and 99mTc-hydroxymethylene diphosphonate. However, a biopsy is the traditional gold standard for diagnosis. The prognosis of patients with coexisting cardiac amyloidosis and aortic stenosis is still under evaluation. The combination of these two pathologies worsens the prognosis. Regarding treatment, mortality is reduced in patients with cardiac amyloidosis and severe aortic stenosis after undergoing transcatheter aortic valve replacement. Further studies are needed to confirm these findings and to understand whether the diagnosis of cardiac amyloidosis could affect therapeutic strategies. The aim of this review is to critically expose the current state-of-art regarding the association of cardiac amyloidosis with aortic stenosis, from pathophysiology to treatment.

Advance of echocardiography in cardiac amyloidosis

Cardiac amyloidosis (CA) occurs when the insoluble fibrils formed by misfolded precursor proteins deposit in cardiac tissues. The early clinical manifestations of CA are not evident, but it is easy to progress to refractory heart failure with an inferior prognosis. Echocardiography is the most commonly adopted non-invasive modality of imaging to visualize cardiac structures and functions, and the preferred modality in the evaluation of patients with cardiac symptoms and suspected CA, which plays a vital role in the diagnosis, prognosis, and long-term management of CA. The present review summarizes the echocardiographic manifestations of CA, new echocardiographic techniques, and the application of multi-parametric echocardiographic models in CA diagnosis.

State-of-the-Art: Noninvasive Assessment of Left Ventricular Function Through Myocardial Work

The assessment of myocardial work (MW) using noninvasive pressure-strain loop analysis is a novel echocardiographic method that provides a more precise assessment of cardiac performance by considering the left ventricular loading condition. By integrating various MW components such as index, efficiency, and constructive and wasted work, an extensive analysis of left ventricular mechanics and energetics can be achieved. This approach offers a more comprehensive assessment of global cardiac function and performance, surpassing conventional surrogate indices. In this review, we aim to summarize the existing knowledge on MW and its distinctive characteristics in various cardiac pathologies.

Association Between Segmental Noninvasive Myocardial Work and Microvascular Perfusion in ST-Segment Elevation Myocardial Infarction: Implications for Left Ventricular Functional Recovery and Clinical Outcomes

BACKGROUND

Predicting left ventricular recovery (LVR) after acute ST-segment elevation myocardial infarction (STEMI) is of prognostic importance. This study aims to explore the prognostic implications of segmental noninvasive myocardial work (MW) and microvascular perfusion (MVP) after STEMI.

METHODS

In this retrospective study, 112 patients with STEMI who underwent primary percutaneous coronary intervention and transthoracic echocardiography after percutaneous coronary intervention were enrolled. Microvascular perfusion was analyzed by myocardial contrast echocardiography, and segmental MW was analyzed by noninvasive pressure-strain loops. A total of 671 segments with abnormal function at baseline were analyzed. The degrees of MVP were observed following intermittent high-mechanical index impulses: replenishment within 4 seconds (normal MVP), replenishment >4 seconds and within 10 seconds (delayed MVP), and persistent defect (microvascular obstruction). The correlation between MW and MVP was analyzed. The correlation of the MW and MVP with LVR (normalization of wall thickening, >25%) was assessed. The prognostic value of segmental MW and MVP for cardiac events (cardiac death, admission for congestive heart failure, or recurrent myocardial infarction) was evaluated.

RESULTS

Normal MVP was seen in 70 segments, delayed MVP in 236, and microvascular obstruction in 365. The segmental MW indices were independently correlated with MVP; 244 (36.4%) segments had segmental LVR at 3-month follow-up. Segmental MW efficiency and MVP were independently associated with segmental LVR (P < .05). The χ2 of combination of segmental MW efficiency and MVP was higher than either index alone for identifying segmental LVR (P < .001). At a median follow-up of 42.0 months, cardiac events occurred in 13 patients; all regional MW parameters, high sensitivity troponin I, regional longitudinal strain, and so on were associated with cardiac events.

CONCLUSIONS

Segmental MW indices are associated with MVP within the infarct zone following reperfused STEMI. Both are independently associated with segmental LVR, and regional MW is associated with cardiac events, providing prognostic value in STEMI patients.

Strain-derived myocardial work in wild-type transthyretin cardiac amyloidosis with aortic stenosis-diagnosis and prognosis

BACKGROUND

Several echocardiographic parameters have been suggested to differentiate wild-type transthyretin cardiac amyloidosis (ATTRwt) from other causes of hypertrophy. These studies have all been performed in small samples of mixed cardiac amyloidosis. The purpose of this study was to investigate the role of echocardiographic parameters in patients with ATTRwt and aortic stenosis (AS) versus patients with AS. The secondary aim was to investigate the role of myocardial work in the prognosis of patients with ATTRwt.

METHODS

The sensitivity and specificity of the relative apical sparing ratio (RAS), the apical-to-basal ratio (AB), the ejection-fraction-to-global-longitudinal-strain ratio (EF/GLS), and the global myocardial work index (GWI) were calculated using receiver-operated characteristics curves and area under the curve (AUC) in patients with ATTRwt and AS (n = 50) versus patients with AS (n = 354). Multivariable regression was used to assess the prognostic value of GWI in patients with ATTRwt (n = 212).

RESULTS

When used to identify AS from ATTRwt + AS, GWI had a sensitivity of 80% and specificity of 70%. The AUC of GWI was larger than that of AB (p = .01) and EF/GLS (p > .01) but not RAS (p = .15). In patients with ATTRwt multivariable regression found age predicted mortality with an estimate of HR = 1.086 (CI: 1.034-1.141) while GWI predicted survival with an estimate of HR = .837 (CI: .733-.956) per 100 mmHg*% increase.

CONCLUSION

GWI was demonstrated to be a viable classifier in ATTRwt and AS versus AS. GWI was demonstrated to independently predict survival in patients with ATTRwt. Further studies examining the role of myocardial work in ATTRwt are warranted.

Cardiac Mechanical Performance Assessment at Different Levels of Exercise in Childhood Acute Lymphoblastic Leukemia Survivors

BACKGROUND

There is a shortage of relevant studies interested in cardiac mechanical performance. Thus, it is clinically relevant to study the impact of cancer treatments on survivors' cardiac mechanical performance to improve our knowledge. The first objective of this study is to assess survivors' cardiac mechanical performance during a cardiopulmonary exercise test (CPET) using both ventricular-arterial coupling (VAC) and cardiac work efficiency (CWE) from cardiac magnetic resonance (CMR) acquisitions. The second objective is to assess the impact of doxorubicin and dexrazoxane (DEX) treatments.

METHODS

A total of 63 childhood acute lymphoblastic leukemia survivors underwent a CMR at rest on a 3T magnetic resonance imaging system, followed by a CPET on ergocycle. The CircAdapt model was used to study cardiac mechanical performance. At different levels of exercise, arterial elastance, end-systolic elastance, VAC, and CWE were estimated.

RESULTS

We observed significant differences between the different levels of exercise for both VAC ( P <0.0001) and CWE parameters ( P =0.001). No significant differences were reported between prognostic risk groups at rest and during the CPET. Nevertheless, we observed that survivors in the SR group had a VAC value slightly lower than heart rate (HR)+DEX and HR groups throughout the CPET. Moreover, survivors in the SR group had a CWE parameter slightly higher than HR+DEX and HR groups throughout the CPET.

CONCLUSIONS

This study reveals that the combination of CPET, CMR acquisitions and CircAdapt model was sensitive enough to observe slight changes in the assessment of VAC and CWE parameters. Our study contributes to improving survivors' follow-up and detection of cardiac problems induced by doxorubicin-related cardiotoxicity.

Effects of continuous positive airway pressure therapy on left ventricular performance in patients with severe obstructive sleep apnea

We investigated myocardial performance concerning obstructive sleep apnea (OSA) severity and the benefits of continuous positive airway pressure (CPAP) therapy. In this randomized sham-controlled trial, 52 patients (mean age, 49 years; 92%, males; mean AHI, 59) with severe OSA were randomly assigned to receive either CPAP or sham treatment for 3 months. The severity of OSA was determined using the apnea/hypopnea index (AHI), oxygen desaturation index (ODI), percentage of sleep time below 90% oxygen saturation (T90), and average O₂ saturation during sleep (mean SpO₂). We compared the changes in myocardial work after 3 months of CPAP (n = 26) versus the sham group (n = 26) at rest and during an exercise stress test. Unlike AHI or ODI, indices of hypoxemia including T90 and mean SpO₂ were significantly correlated with global constructive work, as defined by work of left ventricle (LV) that contributes to LV ejection during systole (T90, β = 0.393, p = 0.012; mean SpO₂, β = 0.331, p = 0.048), and global wasted work (GWW), as defined by work of LV that does not contribute to LV ejection (T90, β = 0.363, p = 0.015; mean SpO₂, β =  - 0.370, p = 0.019). After 3 months, GWW decreased (80.0 ± 49.2 to 60.8 ± 26.3, p = 0.009) and global work efficiency increased (94.0 ± 4.5 to 95.7 ± 2.0, p = 0.008) in the CPAP group compared to those in the sham group. At the 3-month follow-up exercise stress echocardiography, worsening of GWW during exercise was significantly decreased in the CPAP group compared to that in the sham group (p = 0.045 at 50 W). Hypoxemia indices were closely associated with myocardial performance in patients with severe OSA. CPAP treatment for 3 months improved left ventricular myocardial performance by decreasing wasted work and increasing work efficacy compared to the sham treatment.

The value of myocardial work in patients with left ventricular hypertrophy

Myocardial work derived from pressure-strain analysis resembles a novel non-invasive method for myocardial function evaluation. Left ventricular hypertrophy (LVH) is commonly detected in Fabry disease (FD), cardiac amyloidosis (CA) and hypertension (HTN). The study aimed to demonstrate the characteristics of myocardial work in patients with LVH suffering from FD, CA, and HTN. Echocardiography were performed in patients with LVH suffering from FD (n = 13), light chain associated cardiac amyloidosis (AL-CA) (n = 29) and HTN (n = 72), 25 healthy controls were also included in the current study. Conventional and myocardial work parameters were assessed and compared among FD, AL-CA, HTN and controls. Patients with FD and AL-CA were included in the group of infiltrative cardiomyopathy. Logistic regression analysis was used to identify independent predictors for discriminating infiltrative cardiomyopathy from hypertension. Compared with controls, HTN patients had preserved global work index (GWI) and global constructive work (GCW) and reduced global longitudinal strain (GLS) and global work efficiency (GWE) (p < 0.05), but patients with FD and AL-CA had reduced GLS, GWI, GCW and GWE and increased global wasted work (GWW) (p < 0.05). GWI and GCW could discriminate infiltrative cardiomyopathy from HTN independently with high accuracy (GWI cut-off value 1626 mmHg%, sensitivity 0.87, specificity 0.82, area under the curve 0.90; GCW cut-off value 2021 mmHg%, sensitivity 0.84, specificity 0.88, area under the curve 0.91). GWI and GCW were reduced in FD and AL-CA patients, but not in patients with HTN. Myocardial work had an addictive value in differentiating infiltrative cardiomyopathy from hypertension.

Myocardial Work in Echocardiography

Myocardial work is an emerging tool in echocardiography that incorporates left ventricular afterload into global longitudinal strain analysis. Myocardial work correlates with myocardial oxygen consumption, and work efficiency can also be assessed. Myocardial work has been evaluated in a variety of clinical conditions to assess the added value of myocardial work compared to left ventricular ejection fraction and global longitudinal strain. This review showcases the current use of myocardial work in adult echocardiography and its possible role in cardiac pathologies.

Echocardiographic reference ranges for noninvasive left ventricular 18-segment myocardial work index and work efficiency in a healthy Asian population

BACKGROUND

Left ventricular (LV) myocardial work index (WI) and work efficiency (WE) have become the latest indicators for assessing LV function. Reference ranges for normal LV segmental WI and WE have not been established.

METHODS

Four hundred eleven healthy Asian subjects (47% men, median age: 35 years) were enrolled prospectively. WI and WE were analysed using the LV pressure-strain loop (LVPSL) with specific software.

RESULTS

WI and WE differed significantly between segments as well as between walls and levels of the left ventricle. The anteroseptal basal segment had the lowest WI and WE (1440 mmHg ± 324 and 92% [88-96], respectively) among the eighteen segments. Significant WI and WE differences were found between sexes and age groups. No correlation was observed between age groups and the average WI of any wall or level in men, while the average WI of several different walls and levels in women showed significant differences between age groups. The average WI of most walls and levels increased with age in women. No correlation was found between age groups and the average WE of any wall or level in either men or women.

CONCLUSIONS

This study establishes the normal reference values of WI and WE of eighteen segments for clinical work and clinical experiments. There were significant differences in WI and WE between segments, levels, and walls of the normal left ventricle. Sex should be considered when analysing WI and WE. Age should be considered when analysing WI in women.

Clinical research progress of myocardial work in assessment and prediction of coronary artery disease in noninvasive pressure-strain loop technique

Early identification and treatment of high-risk coronary artery disease (CAD) is the main goal of current cardiovascular disease treatments. Speckle-tracking ultrasound technology can quantify myocardial work using pressure-strain loops. Because myocardial work takes into account the effect of the left ventricular systolic function afterload, it can more objectively reflect left ventricular myocardial mechanical function than the overall left ventricular longitudinal strain. Therefore, this technique is more widely used in diseases caused by CAD. This article reviews the evaluation and prediction of different CAD types using a variety of myocardial work parameters and provides a new method for clinical research to assess myocardial function, which is expected to become a new prediction method for CAD.

Identification of wild-type transthyretin cardiac amyloidosis in patients with carpal tunnel syndrome surgery (CACTuS)

AIMS

Wild-type transthyretin cardiac amyloidosis (ATTRwt) is an infiltrative cardiomyopathy with a poor prognosis. The condition is associated with carpal tunnel syndrome (CTS), which often precedes the ATTRwt diagnosis by several years. The aim of the study was (i) to screen patients with a recent history of CTS for ATTRwt using red flags, (ii) to determine whether patients with screened ATTRwt had less advanced disease compared with patients with clinical ATTRwt, and (iii) to assess the sensitivity and specificity of known red flags in ATTRwt.

METHODS AND RESULTS

Patients aged ≥60 years at the time of CTS surgery were invited for screening. Red flags were defined as elevated biomarker levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP) or cardiac troponin, an electrocardiogram pattern associated with ATTRwt, left ventricular hypertrophy (LVH), and impaired longitudinal strain with apical sparring. All patients with a red flag were referred for a diagnostic scintigraphy. Patients with ATTRwt diagnosed by screening were compared with patients with clinical ATTRwt (n = 51) matched by age, gender, and CTS surgery. Among the 120 enrolled subjects (mean age 74.5 years, 90% male), the suspicion of ATTR was raised in 67 (55.8%), and 10 (8.3%) were diagnosed with ATTRwt. Patients identified with ATTRwt were predominantly asymptomatic and had mildly elevated NT-proBNP, mildly increased LVH, preserved left ventricular ejection fraction, and systolic longitudinal function, which differed significantly from clinical ATTRwt controls (P < 0.001).

CONCLUSIONS

The study found an ATTRwt prevalence of 8.3% in a population of age and gender-selected patients with a recent history of CTS. The identified patients with ATTRwt had less structural and functional cardiac involvement than clinical ATTRwt controls.

Myocardial work: the analytical methodology and clinical utilities

The evaluation of left ventricular (LV) systolic function is an essential part of the clinical practice of cardiology. Although left ventricular ejection fraction (LVEF) is the most validated and widely used parameter, it has fundamental limitations. LV strain is more sensitive to detect subtle myocardial dysfunction when LVEF was preserved, but it is load-dependent. Invasive left ventricular pressure-volume loop (LV-PVL) is the reliable standard to evaluate cardiac function, but its wide clinical application is limited by the risk of invasive LV pressure detection. Until the advent of non-invasive LV pressure-strain loop (LV-PSL), things have changed. LV-PSL is in good agreement with regional myocardial oxygen consumption and metabolism. Compared with traditional echocardiographic parameters or LV strain, myocardial work (MW) derived from LV-PSL is a more advanced tool that combines deformation as well as hemodynamics through integration of global longitudinal strain and non-invasive LV systolic pressure. In recent years, researches on MW are going on in full swing and show many advantages of MW. This review described the method and discussed the applications, advantages, limitations, and prospects of MW in multiple cardiovascular diseases. The goal is to provide the readers new insights for evaluating LV systolic function and promote the incorporation of MW into daily practice.

Myocardial work index during normal dobutamine stress echocardiography

Dobutamine stress echocardiography is an alternative method to exercise stress echocardiography for the evaluation of ischemia. Recently, the novel speckle tracking imaging derived parameter, myocardial work index, was suggested for the evaluation of cardiac performance and was evaluated during exercise stress echocardiography. In this study, we analyzed the effect of dobutamine on myocardial work index variables during normal dobutamine stress echocardiography. Echocardiography examinations of patients with normal dobutamine stress echocardiography were collected and underwent off-line speckle tracking imaging analysis. Myocardial work index parameters were calculated at each dose of dobutamine and compared. 286 patients underwent dobutamine stress echocardiography during the study period. 102 patients were excluded due to pre-existed coronary artery disease or ischemia at dobutamine stress echocardiography. 65 patients were excluded due to suboptimal image quality unsuitable for speckle tracking imaging analysis. The remaining 119 patients with normal results were included. The global work index decreased from 2393.3 to 1864.7 mmHg%, p < 0.0004. Global constructive work decreased from 2681.7 to 2152.6 mmHg%, p = 0.001. Global wasted work increased from 78.8 to 128.3 mmHg%, p < 0.003. Global work efficacy decreased from 96.1 to 91.9%, p < 0.00001. Global strain increased from—19.6 to − 23.7%, p < 0.00001. Dobutamine stress echocardiography results in a decrease of all specific myocardial work index parameters even in normal subjects. Only global myocardial strain improved.

New Advanced Imaging Parameters and Biomarkers—A Step Forward in the Diagnosis and Prognosis of TTR Cardiomyopathy

Transthyretin amyloid cardiomyopathy (ATTR-CM) is an infiltrative disorder characterized by extracellular myocardial deposits of amyloid fibrils, with poor outcome, leading to heart failure and death, with significant treatment expenditure. In the era of a novel therapeutic arsenal of disease-modifying agents that target a myriad of pathophysiological mechanisms, timely and accurate diagnosis of ATTR-CM is crucial. Recent advances in therapeutic strategies shown to be most beneficial in the early stages of the disease have determined a paradigm shift in the screening, diagnostic algorithm, and risk classification of patients with ATTR-CM. The aim of this review is to explore the utility of novel specific non-invasive imaging parameters and biomarkers from screening to diagnosis, prognosis, risk stratification, and monitoring of the response to therapy. We will summarize the knowledge of the most recent advances in diagnostic, prognostic, and treatment tailoring parameters for early recognition, prediction of outcome, and better selection of therapeutic candidates in ATTR-CM. Moreover, we will provide input from different potential pathways involved in the pathophysiology of ATTR-CM, on top of the amyloid deposition, such as inflammation, endothelial dysfunction, reduced nitric oxide bioavailability, oxidative stress, and myocardial fibrosis, and their diagnostic, prognostic, and therapeutic implications.

Value of UGT2B7-161 Single Nucleotide Polymorphism in Predicting the Risk of Cardiotoxicity in HER-2 Positive Breast Cancer Patients Who Underwent Pertuzumab Combined with Trastuzumab Therapy by PSL

Objective

To explore the value of uridine diphosphate-glucuronosyltransferase 2B7 (UGT2B7)-161 single nucleotide polymorphism in predicting the occurrence of cardiotoxicity in Chinese human epidermal growth factor 2 (HER-2) positive breast cancer patients who underwent pertuzumab combined with trastuzumab Therapy.

Methods

Fifty patients with HER-2 positive breast cancer who planned to receive trastuzumab and pertuzumab therapy for more than four cycles were enrolled in this study, and blood samples were collected. Thirty healthy volunteers of matching ages were selected as the control group. Myocardial parameters such as global work index, global effective work, and global wasted work were measured before treatment (M0) and at the end of four cycles of treatment month three (M3). Blood samples were collected from patients at the M0 stage, and polymorphisms of the UGT2B7-161 gene were detected to evaluate the predictive ability of different gene phenotypes on the myocardial drug toxicity injury.

Results

There were 35 myocardial work decreased events among 50 patients. There were 24 (47.3%), 15 (40.8%), and 11 (11.8%) patients carrying UGT2B7-161 CC, CT, and TT genotypes, respectively. The occurrence of myocardial work decreased was decreased in UGT2B7-161 TT and CT genotypes (12.5%) compared with CC genotype (41.7%) with statistical significance (P < 0.001). Multivariate logistic regression model analysis exhibited that UGT2B7-161 genotypes, body mass index, and cardiac troponin I were independent factors influencing the risk of cardiotoxicity.

Conclusion

UGT2B7-161 single nucleotide polymorphism is a potential predictive factor for cardiotoxicity in HER-2 positive breast cancer patients receiving trastuzumab and pertuzumab dual-targeted drug therapy.

Multimodality Imaging in Cardiomyopathies with Hypertrophic Phenotypes

Multimodality imaging is a comprehensive strategy to investigate left ventricular hypertrophy (LVH), providing morphologic, functional, and often clinical information to clinicians. Hypertrophic cardiomyopathy (HCM) is defined by an increased LV wall thickness not only explainable by abnormal loading conditions. In the context of HCM, multimodality imaging, by different imaging techniques, such as echocardiography, cardiac magnetic resonance, cardiac computer tomography, and cardiac nuclear imaging, provides essential information for diagnosis, sudden cardiac death stratification, and management. Furthermore, it is essential to uncover the specific cause of HCM, such as Fabry disease and cardiac amyloidosis, which can benefit of specific treatments. This review aims to elucidate the current role of multimodality imaging in adult patients with HCM.

Myocardial Injury in Multiple Myeloma Patients With Preserved Left Ventricular Ejection Fraction: Noninvasive Left Ventricular Pressure-Strain Myocardial Work

Introduction

Over one-half of patients with multiple myeloma (MM) die of heart failure or arrhythmia. Left ventricular ejection fraction (LVEF) is used to describe left ventricular systolic function. However, depressed LVEF means advanced stage of left ventricular dysfunction in patients with MM. Left ventricular pressure-strain-derived myocardial work (LVMW) is a novel and noninvasive method for evaluating LV function related to LV dynamic pressure load. MW is assessed by LV MW index (LVMWI), constructive work, wasted work, and LV MW efficiency (LVMWE). In this study, we aimed to investigate the value of LVMW in cardiac function assessment and clinical prognosis of MM patients with preserved LVEF.

Methods

A total of 72 subjects, including 40 untreated MM patients with preserved EF (including the thick wall and normal wall groups) and 32 non-MM patients, were enrolled in this study. Laboratory data and clinical history of all the patients were collected. All the patients underwent comprehensive echocardiographic examinations and then LVMWI and LVMWE were calculated. Moreover, cardiac adverse events (CAEs) were observed in MM patients treated with bortezomib-based therapy after 6 months and the prognostic value of MW was assessed.

Results

(1) LV myocardial global work index (GWI), myocardial global work efficiency (GWE), and global longitudinal strain (GLS) were lower in the thick wall group of patients with MM compared with the normal wall group and controls. Cardiac segmental analysis of LVMWI in patients with MM showed an apical sparing pattern; (2) The area under the curve (AUC) of GWE for judging the disease severity based on the Revised International Staging System (R-ISS) was 0.835 (95% CI: 0.684–0.933, p < 0.05); (3) GWE, Lg_dFLC, and arrhythmia were independent risk factors of CAEs. The AUC of GWE for predicting CAEs in MM patients treated with bortezomib-based therapy for 6 months follow-up was 0.896 (95% CI: 0.758–0.970, p < 0.05).

Conclusion

MM Patients with preserved EF had subclinical LV systolic dysfunction, which was worse in the thick wall group. LVMWI was presented as “apical sparing” in patients with MM. A lower LVGWE may have a predictive value for CAEs in patients with MM after 6 months of follow-up.

The fundamental role of stress echo in evaluating coronary artery disease in specific patient populations

Stress echocardiography (SE) was initially used for assessing patients with known or suspected coronary heart disease by detecting and evaluating myocardial ischemia and viability. The implementation of SE has gradually been extended to several cardiovascular diseases beyond coronary artery disease, and SE protocols have been modified and adapted for the detection of coronary artery disease (CAD) or other cardiovascular diseases in specific patient populations. This review attempts to summarize current data concerning SE implementation and clinical value in these specific and diverse populations: patients with an intramural course of a coronary artery - known as a myocardial bridge, chronic severe or end-stage hepatic disease, chronic severe or end-stage kidney disease, cardiac allograft vasculopathy, patients scheduled for solid-organ transplantation and other intermediate and high-risk surgery and, finally, patients treated with anticancer drugs or radiotherapy.

Normal Ranges of Global Left Ventricular Myocardial Work Indices in Adults: A Meta-Analysis

BACKGROUND

Recent studies have demonstrated left ventricular myocardial work (MW) is incremental in diagnosis and prognostication when compared to left ventricular ejection fraction and myocardial strain. We performed a meta-analysis of normal ranges of non-invasive MW indices including global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE) and to determine confounder that may contribute to variance in reported values.

METHODS

Four databases including Pubmed, Scopus, Embase, and Cochrane Library were searched through January 2021 using the key terms "myocardial work", "global constructive work", "global wasted work", "global work index", "global work efficiency". Studies were included if the articles reported LV myocardial work using 2D transthoracic echocardiography in healthy normal subjects, either in control group or comprising of the entire study cohort. The weighted mean was estimated by using the random effect model with a 95% confidence interval. Heterogeneity across included studies was assessed using the I² test. Funnel plot and Egger's regression test were used to assess potential publication bias RESULTS: The search yielded 476 articles. After abstract and full-text screening, we included 13 datasets with 1665 patients for the meta-analysis. The reported normal mean values of GWI and GCW among the studies were 2010 mmHg% (95% CI, 1907 to 2113), and 2278 mmHg% (95% CI, 2186 to 2369) respectively. The mean GWW was 80 mmHg% (95% CI, 73 to 87), and the mean GWE was 96.0% (95% CI, 96% to 96%). Furthermore, gender significantly contributed to variations in normal values of GWI, GWW, and GWE. No evidence of significant publication bias was observed.

CONCLUSION

In this meta-analysis, we provide echocardiographic reference ranges for non-invasive indices of MW. These normal values could be served as a reference for clinical and research use.

The Role of New Imaging Technologies in the Diagnosis of Cardiac Amyloidosis

Cardiac amyloidosis is an infiltrative disorder caused by transthyretin or immunoglobulin free light-chain deposition, which determines clinical disease with similar phenotype but different time course, prognosis and therapy. Multimodality imaging is the cornerstone for disease diagnosis and management. Multimodality imaging has revolutionized the approach to the disease favoring its awareness and simplifying its diagnosis, especially in ATTR cardiac amyloidosis. This describes the different imaging tools, from the traditional to the more novel ones, and highlights the different approach in each different setting (prognosis, subtyping, prognosis, monitoring disease progression, and response to therapy).

Transthyretin cardiac amyloidosis in patients after TAVR: clinical and echocardiographic findings and long term survival

Aims

The aim of this study was to examine the prevalence of amyloid transthyretin (ATTR) cardiac amyloidosis in patients 1–2 years after trans‐catheter aortic valve replacement (TAVR) and to assess their clinical and echocardiographic outcome and long‐term survival.

Methods and results

We enrolled 88 patients, mean age 81 years, 534 (390–711) days after TAVR. Patients underwent a Tc99m‐PYP scintigraphy for the diagnosis of ATTR cardiac amyloidosis. Eleven (12.5%) participants were diagnosed with ATTR cardiac amyloidosis. Eighty eight per cent of patients without amyloidosis were in New York Heart Association Classes 1–2 after TAVR, compared with 64% patients with ATTR cardiac amyloidosis (P = 0.022). There were no differences in left ventricular (LV) ejection fraction (P = 0.69) between patients with and without ATTR cardiac amyloidosis at enrolment. The LV mass index and pulmonary artery pressure were significantly higher in patients with ATTR cardiac amyloidosis (P = 0.046 and P = 0.002, respectively). Global longitudinal strain and myocardial work efficiency were significantly lower in patients with ATTR cardiac amyloidosis (P = 0.031 and P = 0.048, respectively). We assessed changes in echocardiographic data, from the time of TAVR to enrolment, and as expected, there was a significant decrease in aortic valve gradient in both groups. There was a significant reduction in LV mass and LV mass index and improvement in basal segment LV strain in the ATTR cardiac amyloidosis negative group (P = 0.045, P = 0.046 and 0.023, respectively). However, in the ATTR cardiac amyloidosis group the change in LV mass and LV mass index and LV basal strain values was not significant (P = 0.24, P = 0.13 and P = 0.35, respectively). The were no significant changes in other echocardiographic parameters in both groups. The patients were followed for 1150 (1086–1221) days after enrolment. Twenty seven patients had at least one cardiac hospitalization during of follow up, of them seven were with ATTR cardiac amyloidosis and 20 patients without amyloidosis (P = 0.017). Eighteen patients (20%) died during follow up; 12 (14%) patients died due to cardiac causes. There was no difference in all‐cause and cardiac mortality between patients with and without ATTR cardiac amyloidosis (P = 0.6 and P = 0.53, respectively).

Conclusions

The long‐term survival after TAVR is not significantly affected by the presence of ATTR cardiac amyloidosis. However, the clinical course of these patients and the LV hemodynamic improvement is less favourable. This hypothesis‐generating study suggests screening for ATTR cardiac amyloidosis in patients who underwent TAVR and have limited clinical or echocardiographic improvement, because they may potentially improve with new therapies for ATTR cardiac amyolidosis.

Global Myocardial Work Combined with Treadmill Exercise Stress to Detect Significant Coronary Artery Disease

BACKGROUND

Myocardial work (MW) derived from the left ventricular pressure-strain loop is a novel and noninvasive method for assessing left ventricular function that accounts for loading conditions. We aimed to explore whether global MW combined with treadmill exercise stress could detect significant coronary artery disease (CAD) in patients with angina pectoris.

METHODS

Eighty-five patients with angina pectoris and no prior CAD history were included. All patients underwent treadmill exercise stress echocardiography and coronary angiography. Global MW was constructed from speckle-tracking echocardiography indexed to the brachial systolic blood pressure. The association between MW parameters and the presence of significant CAD was assessed with logistic regression. The discriminative power of MW parameters to detect CAD was assessed with receiver operative characteristic curve, net reclassification improvement, and integrated discrimination improvement analysis.

RESULTS

Twenty-five patients had a positive exercise echocardiogram, while significant coronary artery stenosis (≥70% in one or more major epicardial vessels or ≥50% in the left main coronary artery) was observed in 41 patients. The global wasted work (GWW) and global work efficiency (GWE) were significantly higher or lower, respectively, in patients with significant CAD compared with those of nonsignificant CAD at the peak exercise and during recovery periods (P < .05 for all). Multivariate logistic regression analysis demonstrated that peak GWE and recovery GWW could predict significant CAD. Peak GWE had the highest area under the receiver operating characteristic curve (AUC) among all global MW parameters (AUC = 0.836). Furthermore, a model comprising peak GWE and recovery GWW performed better for the identification of significant CAD than peak GWE alone (AUC = 0.856).

CONCLUSIONS

Peak GWE could detect significant CAD. The new model, incorporating peak GWE and recovery GWW, not only identified but also provided additional value for estimating the probability of significant CAD. Global MW parameters combined with exercise stress perform as an accurate noninvasive screening before the invasive diagnostic technique.

Myocardial Work Does Not Have Additional Diagnostic Value in the Assessment of ATTR Cardiac Amyloidosis

Background: Reduced LV longitudinal strain (GLS) and increased relative apical sparing (RELAPS) and increased wall thickness have been proposed as features for transthyretin cardiac amyloidosis (ATTR-CA). Myocardial work (MW) has recently been shown as useful afterload independent disease marker, hence we aimed to investigate its use in differentiating ATTR-CA from heart failure with increased septal thickness but no cardiac amyloidosis (CA) (HFnCA). Methods: This study included patients with HF and increased septal thickness ≥ 14 mm. We included 59 patients with hereditary (ATTRv) and 27 wild type transthyretin amyloidosis (ATTRwt) described as ATTR-CA based on DPD scintigraphy. We also enrolled 30 non-amyloidosis heart failure patients with negative DPD scintigraphy, as a control group. Myocardial work (MW) was used to assess the index (GWI), constructive (GCW) and wasted (GWW) work. Relative wall thickness (RWT) and relative apical sparing (RELAPS) were tested as conventional measures. Results: The RWT and RELAPS were higher in ATTR-CA (p < 0.001) and predicted ATTR-CA (RWT; AUC = 0.84, p < 0.001) and RELAPS (AUC = 0.81, p < 0.001). MW; GWI (p = 0.04), GCW (p = 0.03), GWW (p = 0.001) were all lower in ATTR-CA compared with HFnCA but only GWW predicted ATTR-CA, (AUC = 0.75, p < 0.001). Binary logistic univariate regression analysis showed RWT (p = 0.003, β = 16.2) and RELAPS (p = 0.003, β = 2.3) to be associated with ATTR-CA but not MW. GWI and GCW correlated with NT-proBNP (p < 0.05) and Troponin (p < 0.01), but not RWT or RELAPS. Conclusion: Myocardial work had lower accuracy, compared to RWT or RELAPS, in identifying ATTR-CA but was better related to biomarkers. Thus, MW assessment is unlikely to have additional value in improving the diagnosis of heart failure due to ATTR-CA.

Myocardial Work by Echocardiography: Principles and Applications in Clinical Practice

Left ventricular (LV) global longitudinal strain (GLS) has established itself in the last decade as a reliable, more objective method for the evaluation of LV systolic function, able to detect subtle abnormalities in LV contraction even in the presence of preserved ejection fraction (EF). However, recent studies have demonstrated that GLS, similar to LV EF, has important load dependency. Non-invasive myocardial work (MW) quantification has emerged in the last years as an alternative tool for myocardial function assessment. This new method, incorporating measurement of strain and LV pressure, has shown to overcome GLS and LV EF limitations and provide a loading-independent evaluation of myocardial performance. The presence of a commercially available echocardiographic software for the non-invasive MW calculation has allowed the application of this new method in different settings. This review sought to provide an overview on the current knowledge of non-invasive MW estimation, showing its potential applications and possible added value in clinical practice.

Myocardial work and left ventricular contractile reserve during stress echocardiography: An angiographic validation

OBJECTIVE

This study sought to determine the contractile reserve (CR) response to exercise stress echocardiography (ESE) quantified by the novel parameter, non-invasive myocardial work (MW), in subjects with angiographically proven coronary artery disease (CAD).

METHODS

CR was measured by the relative change in ejection fraction (EF), global longitudinal strain (GLS) and MW indices from rest to peak exercise in 304 patients referred for clinically indicated ESE. Positive ESE patients proceeded to coronary angiography and further risk stratified based on either percutaneous or surgical intervention.

RESULTS

CR_GLS and global work index (CR_GWI ) significantly decreased with exercise induced ischemia and angiographically proven significant CAD (CR_GLS -1.6±3.5%; CR_GWI -8.6±511 mm Hg% decrement, p < 0.001) compared to non-ischemic patients (CR_GLS 1.4±2.2%; CR_GWI 398±404 mm Hg% improvement). Global constructive work (CR_GCW ) was significantly higher (p < 0.0001) in non-ischemic (818±457 mm Hg%) and blunted in ischemic patients (208±550 mm Hg%). CR_GCW (AUC .81; 95%CI:.75-.86) demonstrated the most association for inducible ischemia followed by CR_GLS (AUC .75; 95%CI:.69-.80), CR_GWI (AUC .73, 95%CI:.67-.79) and CR_EF (AUC .71; 95%CI:.65-.77, p < 0.001). Subgroup analysis showed patients requiring surgical revascularization demonstrated a significantly lower CR_GWE (-11.5±7.6%, p < 0.05) as a result of reduced CR_GCW (281±573 mm Hg%, p < 0.05) and increased global wasted work (CR_GWW , 289±151 mm Hg%, p = 0.09).

CONCLUSION

Multivessel disease requiring surgical revascularization have the greatest reduction in CR. MW may potentially improve detection of ischemia and further risk stratification during ESE to maximize the benefits of revascularization.

Afterload-related reference values for myocardial work indices

BACKGROUND

The novel noninvasive pressure-strain loop (PSL) is a reliable tool that reflects myocardial work (MW). Systolic blood pressure (SBP) is the only independent factor for MW indices. However, afterload-related reference values have not been previously reported. The aim of the present study was to establish reference values for MW parameters by wide range SBP grading.

METHODS

We prospectively selected healthy individuals and subjects with SBP ≥ 140 mmHg at the time of study without myocardial remodeling. MW parameters were collected and the reference values achieved were grouped by SBP in 10-mmHg.

RESULTS

Significant differences were noted among the SBP-groups for global work index (GWI) and global constructive work (GCW). The majority of statistical comparisons of the differences in GWI and GCW were significant at each SBP-group. With SBP ranging from 90 to 189 mmHg, the parameters GWI and GCW tended to increase linearly with afterload. Overall, the global wasted work (GWW) tended to rise as SBP was increased, but not all of the differences noted in GWW were significant for each SBP-group. Global work efficiency (GWE) remained stable across all SBP-groups, with the exception of a slight drop noted when it exceeded 160 mmHg.

CONCLUSIONS

The amount of MW but not the work efficiency varied greatly according to the different afterload. This finding cannot be ignored during clinical research or diagnosis and afterload-related reference values are required to make a reasonable judgment on the myocardial function.

The non-invasive assessment of myocardial work by pressure-strain analysis: clinical applications

Pressure–volume (PV) analysis is the most comprehensive way to describe cardiac function, giving insights into cardiac mechanics and energetics. However, PV analysis still remains a highly invasive and time-consuming method, preventing it from integration into clinical practice. Most of the echocardiographic parameters currently used in the clinical routine to characterize left ventricular (LV) systolic function, such as LV ejection fraction and LV global longitudinal strain, do not take the pressure developed within the LV into account and therefore fall too short in describing LV function as a hydraulic pump. Recently, LV pressure-strain analysis has been introduced as a new technique to assess myocardial work in a non-invasive fashion. This new method showed new insights in comparison to invasive measurements and was validated in different cardiac pathologies, e.g., for the detection of coronary artery disease, cardiac resynchronization therapy (CRT)-response prediction, and different forms of heart failure. Non-invasively assessed myocardial work may play a major role in guiding therapies and estimating prognosis. However, its incremental prognostic validity in comparison to common echocardiographic parameters remains unclear. This review aims to provide an overview of pressure-strain analysis, including its current application in the clinical arena, as well as potential fields of exploitation.

The Utility of Myocardial Work in Clinical Practice

Myocardial work (MW) is a novel technique used in the advanced assessment of left ventricular function. In the past few years, this invasive measure has evolved to become a more attainable noninvasive technique. MW has benefits over left ventricular ejection fraction and global longitudinal strain by speckle-tracking echocardiography, as it includes the afterload-dependent limitation and dynamic myocardial contraction in relationship to various loading conditions. In this article, the authors provide a summary overview and discuss the additive value noninvasive MW provides to left ventricular systolic function assessment. The authors explore the evolution of invasive to noninvasive MW, examine how to acquire and measure, discuss normal reference values, examine its role in a multitude of cardiac conditions that have been investigated in current research, review a variety of clinical applications, and discuss potential limitations. The goal is to allow the reader to see the benefits of this rapidly emerging application and be able to incorporate it into everyday practice.

Myocardial Work: Methodology and Clinical Applications

A precise and accurate assessment of left ventricular (LV) contractility is of utmost importance in terms of prognosis in most cardiac pathologies. Given the limitations of ejection fraction (EF) and global longitudinal strain (GLS) due to their load dependency, a novel imaging tool called myocardial work (MW) has emerged as a promising method for LV performance evaluation. MW is a novel, less load-dependent method based on computation of myocardial strain-arterial blood pressure curves. This method provides a more detailed assessment of segmental and global LV function incorporating the patient's LV pressure and is derived by brachial artery pressure utilizing an empiric reference curve adjusted to the duration of the isovolumic and ejection phases as determined by echocardiography. The clinical implications of this unique method have been expanding in the last few years, which attest to the robust additive role of MW in routine practice.

The Role of Multi-modality Imaging in the Diagnosis of Cardiac Amyloidosis: A Focused Update

Cardiac amyloidosis (CA) is a unique disease entity involving an infiltrative process, typically resulting in a restrictive cardiomyopathy with diastolic heart failure that ultimately progresses to systolic heart failure. The two most common subtypes are light-chain and transthyretin amyloidosis. Early diagnosis of this disease entity, especially light-chain CA subtype, is crucial, as it portends a poorer prognosis. This review focuses on the clinical utility of the various imaging modalities in the diagnosis and differentiation of CA subtypes. This review also aims to highlight the key advances in each of the imaging modalities in the diagnosis and prognostication of CA.

Noninvasive Myocardial Work Index: Characterizing the Normal and Ischemic Response to Exercise

BACKGROUND

Myocardial work index (MWI) and work efficiency are new parameters for assessing left ventricular function. We aim to characterize the normal response to exercise in a mixed population and determine whether MWI can identify patients with inducible ischemia.

METHODS

Patients were retrospectively enrolled from an existing database of exercise stress echocardiography. Inclusion criteria were a clinical indication of possible ischemia and technical suitability to calculate MWI. Exclusion criteria were abnormal baseline left ventricular function or inadequate image quality. Echocardiograms positive for ischemia were defined by independent visual assessment and compared with angiographic findings where available. Myocardial work index was determined using a proprietary algorithm and efficiency calculated as constructive work divided by the sum of constructive and wasted work.

RESULTS

A total of 177 patients met inclusion criteria; 117 were excluded, leaving 40 normal and 20 positive tests. During normal exercise, global MWI increased 54% (from 2,296 to 3,523 mm Hg%) and efficiency remained at 96%. However, in patients with inducible ischemia, MWI decreased in affected segments, global MWI did not increase (2,069-2,070 mm Hg%), and global efficiency fell from 93% to 87%. The receiver operating characteristic curve for MWI had an area under the curve of 0.94.

CONCLUSIONS

During normal exercise, MWI increases and efficiency remains unchanged. However, during exercise-induced ischemia, MWI paradoxically decreases in affected segments, while globally MWI fails to increase and efficiency decreases. We have demonstrated that MWI can be applied to stress echocardiography to identify ischemia, but its utility remains uncertain. Further research that makes comparisons with an objective measure of functional ischemia is needed.