Echo-Derived Myocardial Work Indices Track Recovery After Heart Attack

The work, published in Echo Research & Practice, followed 31 patients who suffered a first ST-elevation myocardial infarction and were treated with primary percutaneous coronary intervention at Turku University Hospital between December 2018 and January 2021.

The measurements in question are called myocardial work indices, and they are calculated from speckle-tracking echocardiography, a technique that follows the natural speckled pattern of the heart muscle on ultrasound images to quantify how much each region of the left ventricle deforms during contraction. Standard strain measurements, however, are sensitive to loading conditions and can be distorted by elevated afterload. Myocardial work indices address this by combining the deformation data with a non-invasively estimated left ventricular pressure curve, built by synchronising the strain data with the patient’s systolic blood pressure and the timing of aortic and mitral valve events. The result is an areal pressure-strain loop from which four indices are derived: the myocardial work index (MWI), constructive work (MCW), wasted work (MWW), and work efficiency (MWE).

To anchor these echocardiographic numbers to what was actually happening inside the heart muscle, the researchers paired each baseline ultrasound scan with positron emission tomography using oxygen-15 labelled water. The PET scans, performed on the same day as the baseline echo, a median of roughly eight days after the intervention, quantified absolute myocardial blood flow in millilitres per gram per minute and a perfusable tissue fraction (PTF) that indicates how much living, perfusable tissue remains in each segment. Segments with a PTF of at least 0.60 grams per millilitre were classified as viable, while those below that threshold were considered non-viable. Each patient’s myocardial area at risk was defined from the culprit coronary artery identified on invasive angiography and electrocardiography, allowing regional comparisons between the injured territory and the remote, spared myocardium.

The cohort consisted of patients enrolled during their index hospitalisation who had a left ventricular ejection fraction below 50 percent. All underwent primary percutaneous coronary intervention an average of 4.9 hours after symptom onset. Baseline imaging took place 3 to 14 days after the infarction, and follow-up echocardiography was performed around 210 days later. One patient was lost to follow-up, leaving 30 patients with paired baseline and six-month scans. Notably, no deaths or heart failure hospitalisations occurred during the follow-up period, and only one patient experienced a further, non-ST-elevation infarction related to a different coronary lesion.

The central finding concerns the trajectories of the global work indices. While the ejection fraction and global longitudinal strain remained statistically unchanged between baseline and six months, global MWI, MCW and MWE all rose significantly, and MWW fell, over the same interval. In other words, the heart’s measured pumping efficiency improved in ways that conventional ejection fraction did not capture. Within the area at risk, MWI, MCW and MWE were markedly lower than in the remote myocardium both at baseline and at follow-up, and MWI and MCW increased significantly by six months, with wasted work declining. An illustrative case in the paper shows reduced work indices and reduced blood flow in the anteroseptal region of a patient with a proximal left anterior descending artery occlusion, with partial recovery of the work indices at follow-up.

The changes in work indices also paralleled functional recovery, defined in the study as an increase in ejection fraction of at least 5 percentage points from baseline. Twelve of the 30 patients, or 40 percent, met this criterion. The change in global MWI and in MCW correlated significantly with the change in ejection fraction and with the change in global longitudinal strain, and both indices increased significantly more in the recovery group than in the no-recovery group. Changes in MWE and MWW, by contrast, were neither correlated with ejection fraction change nor different between the two groups. This dissociation matters, because it suggests that the raw work index and constructive work, rather than the efficiency measure, are the components most closely tied to recovery of pumping function.

The PET data added a perfusion dimension. Globally, neither MWI nor MWE correlated with resting myocardial blood flow, a result the authors attribute to the complex interplay between post-ischaemic stunning in viable segments and reduced flow in non-viable segments within the area at risk. Regionally, however, the picture was clearer: within the area at risk, MWI and MWE correlated significantly with regional blood flow (correlation coefficients of 0.53 and 0.59 respectively) and with the perfusable tissue fraction (0.41 and 0.65). Both global indices were also inversely associated with peak troponin T and NT-proBNP levels, the established biochemical markers of infarct size and cardiac stress, and correlated with ejection fraction and global longitudinal strain at both time points.

Perhaps the most clinically suggestive results concern viability at the segment level. Of the 461 analysable segments, 416 were viable and 45 were non-viable by the PET threshold. At baseline, longitudinal strain, MWI, MCW and MWE were all higher in viable segments, and by six months the work indices had risen further in viable tissue while remaining flat in non-viable segments. Receiver operating characteristic analysis showed moderate discriminatory power: an MWI cut-off of 945 mmHg percent and an MCW cut-off of 1202 mmHg percent predicted segmental viability with areas under the curve of 0.708 and 0.697, while MWE performed less well with an area of 0.614 despite showing a significant association in logistic regression. The authors suggest that work efficiency may partly reflect preserved contractile function rather than viability itself, since its calculation incorporates wasted work.

The study’s limitations are acknowledged plainly by its authors. It was a single-centre pilot with relatively few patients, and the imaging window of 3 to 14 days after infarction spans a period during which myocardial stunning and microvascular recovery evolve, although the researchers found no significant differences in the key parameters between patients imaged within seven days and those imaged later. The small sample and the low number of clinical events meant the team could not assess whether the work indices predict hard outcomes such as death or heart failure hospitalisation, and longer-term outcome data were unavailable. Viability was assessed with the oxygen-15 water perfusable tissue fraction rather than fluorodeoxyglucose PET or cardiac magnetic resonance, although the authors note that PTF has yielded results comparable to those established methods, while conceding that PET provides less detailed tissue characterisation than CMR.

Within those constraints, the findings position myocardial work indices as plausible non-invasive markers of myocardial injury severity, segmental viability and functional recovery after a reperfused heart attack. The indices improved over six months in parallel with ejection fraction, tracked the burden of injury as reflected in troponin T and NT-proBNP, distinguished viable from non-viable myocardium at the segment level, and changed over time only where the muscle remained alive. What the pilot study cannot yet establish is whether these measurements, obtained within the first two weeks after infarction, will genuinely forecast which patients will recover function or suffer clinical events in larger and longer follow-up studies. That question, the authors conclude, awaits trials with substantially more patients and extended outcome data before myocardial work indices can move from research tool to routine prognostic instrument in the cardiac catheterisation follow-up clinic.

Subject of Research: Trajectories of echocardiographic myocardial work indices and their relation to perfusion and viability after reperfused acute myocardial infarction

Article Title: Trajectories and determinants of echocardiographic myocardial work indices after acute myocardial infarction: a pilot study

Article References: Ballo, H., Nammas, W., Paunonen, C., Teuho, J., Siekkinen, R., Li, X.-G., Roivainen, A., Knuuti, J., & Saraste, A. (2026). Trajectories and determinants of echocardiographic myocardial work indices after acute myocardial infarction: a pilot study. Echo Research & Practice, 13(1), Article 29. https://doi.org/10.1186/s44156-026-00131-5

Image Credits: AI Generated

DOI: 10.1186/s44156-026-00131-5

Keywords: myocardial work indices, echocardiography, acute myocardial infarction, speckle-tracking strain, PET perfusion, myocardial viability, left ventricular ejection fraction, troponin T, NT-proBNP, functional recovery, pressure-strain loop, pilot study