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

Prognostic relevance of global work index and global constructive work in patients with non-ischemic dilated cardiomyopathy

Myocardial work (MW) derived from pressure-strain loops is a novel non-invasive tool to assess left ventricular (LV) function, incorporating global longitudinal strain (GLS) by speckle tracking echocardiography and non-invasively assessed blood pressure. Studies on the role of MW in dilated cardiomyopathy (DCM) are still limited. Therefore, the aim of this study was to evaluate the potential value of MW for predicting adverse outcomes in patients with DCM. 116 consecutive patients with DCM who underwent heart catheterization were retrospectively recruited from June 2009 to July 2014. 34 patients (30%) met the composite endpoints for major adverse cardiac events (MACE) of cardiac transplantation, need for implantable cardioverter-defibrillator (ICD) therapy, heart failure hospitalization and all-cause mortality. Patients with DCM were followed up for a mean of 5.1 years (IQR: 2.2-9.1 years). Global work index (GWI) and global constructive work (GCW) were not only independent predictors but also provided incremental predictive values (Integrated discrimination improvement [IDI] > 0) of MACE in multivariate Cox models. Furthermore, Patients with GWI < 788 mm Hg% (HR 5.46, 95%CI 1.66-17.92, p = 0.005) and GCW < 1,238 mm Hg% (HR 4.46, 95%CI 1.53-12.98, p = 0.006) had higher risks of MACE. GWI and GCW assessed by strain imaging echocardiography may have an additional value beyond LV-EF and GLS for predicting adverse outcomes in DCM.

Noninvasive Assessment of Myocardial Work in Children

The noninvasive assessment of ventricular function is an ongoing challenge, with new tools and measurements always being considered and tested. The noninvasive assessment of myocardial work via the pressure-strain relationship is one of the newer tools proposed to evaluate ventricular systolic function. However, prior to using any new tool, one should understand its properties, utility, and limitations. In this commentary we focus on the noninvasive assessment of myocardial work via the pressure-strain relationship from a pediatric point of view. We address the current knowledge and limitations and propose future directions to better understand this tool.

Timing and Patient Position During Cuff Blood Pressure Measurement Affect Myocardial Work Parameters Measured by Echocardiography

BACKGROUND

Although cuff blood pressure measurement is a critical parameter to calculate myocardial work noninvasively, there is no recommendation about when and how to measure it. Accordingly, we sought to evaluate the effects of the timing during the echo study and the patient's position on the scanning bed during the cuff blood pressure measurement on myocardial work parameter calculations.

METHODS

One hundred one consecutive patients (44 women, 66 ± 14 years) undergoing clinically indicated echocardiography were prospectively enrolled. During the echocardiographic study, we measured the cuff blood pressure 4 times, using a fully automatic digital blood pressure monitor applied to the right and left arm in the same position throughout the study: BP1, before the start of the echo study, with the patient lying in the supine position; BP2, after positioning the patients on their left side to start the echo study; BP3, at the time of the acquisition of the 3 apical views (4- and 2-chamber and long-axis) used to measured left ventricular global longitudinal strain; and BP4, at the end of the echo study with the patient again in the supine position.

RESULTS

Systolic blood pressureat BP1 was 147 ± 21 mm Hg. Between BP1 and BP2, it dropped by 17 ± 9 mm Hg (P < .05). Systolic blood pressure at BP3 was significantly lower than BP2 (130 ± 20 mm Hg vs 122 ± 18 mm Hg, P < .05), and at BP4 was significantly lower than at BP1 (-9 ± 13 mm Hg, P < .05). The average global longitudinal strain was -16% ± 3%. Accordingly, the global work index was 1,929 ± 441 mm Hg% at BP1, dropped to 1,717 ± 421 at BP2, decreased to 1,602 ± 351 mm Hg% at BP3, and increased to 1,815 ± 386 mm Hg% at BP4 (P < .001).

CONCLUSIONS

The timing during the echocardiography study and the patient's position on the scanning bed are critical determinants of the measured cuff systolic blood pressure and the resulting values of myocardial work parameters.

Global left ventricular myocardial work index and medium-term adverse cardiovascular events after ST-elevation myocardial infarction

BACKGROUND

Left ventricular global longitudinal strain (GLS) has incremental prognostic value over ejection fraction (EF) in patients with ST-segment-elevation myocardial infarction (STEMI), but it is also load dependent. It has been recently demonstrated that Myocardial work (MW), integrating blood pressure with GLS, predicts long-term all-cause mortality. We aimed to further explore the prognostic value of MW for cardiovascular endpoints in patients with STEMI.

METHODS AND RESULTS

Retrospective study of 200 consecutive patients admitted with a STEMI, mean age of 62 (SD 12) years, 79.5% males, that survived to discharge. Transthoracic echocardiography was performed before discharge (5 ± 3 days after admission). Mean follow-up was 790 days. The primary outcome was a composite of cardiovascular death, non-fatal myocardial infarction, and unplanned cardiovascular admission (ACE). During follow-up, 26 patients had a ACE. In univariable Cox regression analysis, male gender, body mass index, GRACE risk score and Global Work Index (GWI) were selected to the multivariable analysis, in which, only GWI (per 100 mmHg% decrease: hazard ratio estimate 1.19, 95% confidence interval 1.07-1.34, p-value = 0.002) remained independently associated with ACE, with effective reclassification of non-events. The best GWI cut-off to predict ACE was ≤1165 mmHg% (Log-rank, p = 0.034).

CONCLUSIONS

LV GWI is independently associated with medium-term ACE. Nevertheless, prospective studies in a larger sample of patients are warranted to confirm this finding.

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.

Myocardial Work Assessment in Patients after Coronary Artery Bypass Grafting during Cardiac Rehabilitation

BACKGROUND

Myocardial work is an innovative echocardiographic tool to assess left ventricular performance. Emerging data have shown the added value of this method for evaluating cardiac function compared to traditional echocardiographic parameters and global longitudinal strain. However, few studies are present in the literature about the role of myocardial work during cardiac rehabilitation. Our aim was to assess the impact of a rehabilitation program on myocardial work indices in patients with preserved left ventricular ejection fraction and after coronary artery bypass grafting. In addition, we assessed the correlation between baseline myocardial work indices and their change after cardiac rehabilitation, establishing an optimal cut-off value to predict the improvement.

METHODS

An observational, single-center, and prospective study was conducted. We enrolled patients referred to cardiac rehabilitation after coronary artery bypass grafting and with preserved left ventricular ejection fraction. Before and after the cardiac rehabilitation program, a comprehensive patient assessment was performed, including traditional transthoracic echocardiography, myocardial work analysis, and a six-minute walk test.

RESULTS

Eighty-four patients were enrolled; the mean age was 67.96 (±7.42) years and 78.6% were male. The left ventricular ejection fraction was preserved in all patients, and the global longitudinal strain was -16.18 ± 2.55%, the global work index was 1588.56 ± 345 mmHg%, the global constructive work was 1771.27 ± 366.36 mmHg%, the global wasted work was 105.8 ± 72.02 mmHg%, and the global work efficiency was 92.63 ± 3.9% at baseline. After the cardiac rehabilitation program, the global work index, the global constructive work, and the six-minute walk test improved significantly (1588.56 ± 345 vs. 1960.2 ± 377.03 mmHg%, p-value < 0.001; 1771.27 ± 366.36 vs. 2172.01 ± 418.73 mmHg%, p-value < 0.001; 70.71 ± 40.2 vs. 437.5 ± 108.70 m, p-value < 0.001, respectively).

CONCLUSIONS

Myocardial work indices, specifically global work index and global constructive work, improve after cardiac rehabilitation program in patients undergoing coronary artery bypass grafting with preserved left ventricular ejection fraction.