Intraoperative Noninvasive Left Ventricular Myocardial Work Indices in Patients Undergoing On-Pump Coronary Artery Bypass Surgery

Intraoperative Transesophageal Echocardiographic Guidance in Cardiac Surgery

Transesophageal echocardiography (TEE) is a valuable tool for diagnosing structural heart diseases, offering superior resolution compared to transthoracic echocardiography. It allows for real-time evaluation of cardiac valves and both systolic and diastolic heart function. Additionally, TEE facilitates the prompt detection of potential complications during cardiac surgeries, such as paravalvular leaks, iatrogenic aortic dissections, and pericardial effusions. Advances in imaging, including 3D echocardiography, have further enhanced the visualization of complex structures like cardiac valves, providing "surgical views" that improve preoperative planning. These features have also made TEE indispensable for postoperative evaluation of cardiac valve repairs and for intraoperative guidance during minimally invasive procedures. This review article aims to summarize the indications for using TEE as an intraoperative tool in cardiac surgery.

Intraoperative Assessment of Noninvasive Left Ventricular Myocardial Work Indices in Patients Undergoing Aortic Valve Replacement

OBJECTIVE

Evaluation of noninvasive left ventricular (LV) myocardial work (MW) enables insights into cardiac contractility and efficacy beyond conventional echocardiography. However, there is limited intraoperative data on patients undergoing surgical aortic valve replacement (AVR). The aim of this study was to describe the feasibility and the intraoperative course of this technique of ventricular function assessment in these patients and compare it to conventional two (2D)- and three-dimensional (3D) echocardiographic measurements and strain analysis.

DESIGN

Prospective observational study.

SETTING

Single university hospital.

PARTICIPANTS

Twenty-five patients scheduled for isolated AVR with preoperative preserved left and right ventricular function, sinus rhythm, without significant other heart valve disease or pulmonary hypertension, and an uneventful intraoperative course.

INTERVENTIONS

Transesophageal echocardiography was performed after induction of anesthesia (T1), after termination of cardiopulmonary bypass (T2), and after sternal closure (T3). Evaluation was performed in stable hemodynamics, in sinus rhythm or atrial pacing and vasopressor support with norepinephrine ≤ 0.1 µg/kg/min.

MEASUREMENTS AND MAIN RESULTS

EchoPAC v206 software (GE Vingmed Ultrasound AS, Norway) was used for analysis of 2D and 3D LV ejection fraction (EF), LV global longitudinal strain (GLS), LV global work index (GWI), LV global constructive work (GCW), LV global wasted work (GWW), and LV global work efficiency (GWE). Estimation of myocardial work was feasible in all patients. Although there was no significant difference in the values of 2D and 3D EF, GWI and GCW decreased significantly after AVR (T1 v T2, 1,647 ± 380 mmHg% v 1,021 ± 233 mmHg%, p < 0.001; T1 v T2, 2,095 ± 433 mmHg% v 1,402 ± 242 mmHg%, p < 0.001, respectively), while GWW remained unchanged (T1 v T2, 296 mmHg% [IQR 178-452) v 309 mmHg% [IQR 255-438), p = 0.97). This resulted in a decreased GWE directly after bypass (T1 v T2, 84% ± 6% v 78% ± 5%, p < 0.001), but GWE already improved at the end of surgery (T2 v T3, 78% ± 5% v 81% ± 5%, p = 0.003). There was no significant change in the values of GWI, GCW, or 2D and 3D LVEF before and after sternal closure (T2 v T3).

CONCLUSION

LV MW analysis showed a reduction of LV workload after bypass in our group of patients, which was not detected by conventional echocardiographic measures. This evolving technique provides deeper insights into cardiac energetics and efficiency in the perioperative course of aortic valve replacement surgery.

From ejection fraction, to myocardial strain, and myocardial work in echocardiography: Clinical impact and controversies

Enhancing an echocardiographic tool, aimed to detect even subtle left ventricular (LV) systolic function abnormalities, capable of obtaining both early diagnosis and risk prediction of heart disease, represents an ambitious, attractive, and arduous purpose in the modern era of cardiovascular imaging. Ideally, that tool should be simple, reliable, and reproducible, in order to be concretely applied in routine clinical practice. Importantly, that technique should be physiologically plausible and useful both at the population-level, as well as in the individual subject. For a long time, LV ejection fraction (EF) has been considered the first-line parameter for assessing LV global systolic function, strictly related to the prognosis, at least in some settings. However, LV EF limitations are well-known, even though frequently overemphasized, including its load-dependency. Therefore, myocardial strain techniques have been proposed, deemed able to disclose even subtle early LV function anomalies. Nevertheless, many disadvantages of myocardial strain have been reported as well. More recently, myocardial work (MW) analysis has been introduced as a new echocardiographic tool for the evaluation of LV global systolic function, attempting to overcome EF and strain disadvantages. However, MW has shown many limits as well. Notwithstanding, LV EF still remains a landmark functional classification marker for heart failure and cardiac oncology, allowing reliable fast reassessment of LV function changes during patient management, in order to guide treatment in individual cases as well. Notably, global longitudinal strain and MW parameters seem to show better meaningful results at the population-level, but controversial clinical impact, major limitations, wide cut-offs spread and overlap, when the single value needs to be applied to the single case. Taking into account the recent literature-based evidence, the scope of the present narrative critical review is trying to delineate the different types of information given by the described LV global systolic function parameters, both at the population-level and in the individual case, in order to trace a comparative analysis of advantages and limitations in clinical practice.