This prospective observational study investigated a simplified method with e’ and E/e’ for assessing diastolic function, and the results showed that regardless of which method used (comprehensive or simplified assessment), a high prevalence of diastolic dysfunction was found. Patients with comorbidities including hypertension, ischemic heart disease, chronic kidney disease, bronchial asthma, as well as patients with increased age, low exercise capacity, and smoking were more likely to have diastolic dysfunction. In this study, the proportion of patients with diastolic dysfunction was higher than expected. In a general population, the prevalence of diastolic dysfunction has been reported to approximately 25-27%[2, 3], in contrast to in this unselected ambulatory surgical cohort in which majority of patients presented with diastolic dysfunction. However, this surgical population is not fully representative of the general population in terms of age and comorbidities, and we believe this somewhat unexpected finding may reflect on the high number of patients with hypertension and IHD. Nonetheless, the results demonstrate that the simplified method using e’-velocities had a high NPV, sensitivity, and AUROC, indicating that this approach may be used to rule out patients with diastolic dysfunction with an appropriate accuracy.
Furthermore, the results are in line with previous studies and indicate that e’-velocities with a cut-off at 9 cm s-1 may be used to discriminate both symptomatic and asymptomatic patients with diastolic dysfunction from patients without these concerns.[13, 14] However, the poor PPV and rather low specificity may allow for misdiagnosis and a test result indicating diastolic dysfunction should be interpreted with caution, and always in a clinical context. Additionally, in this cohort e’-velocities alone could not differentiate between different grades of diastolic dysfunction, which from an anesthesiologist point of view is a clear shortage since different patterns of diastolic filling may require different vigilance and strategies. Hence, in order to with certitude diagnose diastolic dysfunction and to discriminate between different grades of diastolic dysfunction a more comprehensive, but indeed more time consuming, assessment may be required.
Regarding the use of E/e’ for assessing filling pressures, previous evidence is somewhat conflicting.[15, 24] In this study E/e’ seems to, compared with comprehensive echocardiography, exaggerate the severity of diastolic dysfunction. But, in a pre-operative setting, an overestimation may be preferable to the opposite in terms of patient safety. Nonetheless, point-of-care assessment is a real-time and goal-oriented modality not intended to replace a comprehensive assessment[25], but to present a rapid tool for assessing cardiac function for non-cardiologists when hemodynamic instability and need of volume replacement can be expected, and cardiologist referral may not be suitable. Despite the primary aim of this study exploring the feasibility of tissue Doppler velocities to measure diastolic dysfunction in a clinical setting, systolic dysfunction is worth being mentioned briefly. Systolic dysfunction is often accompanied with diastolic dysfunction. Hence, tissue Doppler as a point-of-care modality can be used not only for diastolic function, but for simultaneous assessment of both diastolic and systolic function which may serve an opportunity for a very fast assessment of global LV function. Furthermore, tissue Doppler measurements are acknowledged to be relatively non volume-dependent [26], supported by the results also in this study where no differences in e’-velocities were found between patients in different volume states. Additionally, e’-velocities per se are reliable in atrial fibrillation[26] and fast to measure in a 4-chamber projection. The time needed for tissue Doppler measurements in the point-of-care context is within one minute, as shown in our previous study.[23]
Diastolic dysfunction is initially often asymptomatic, but is still associated with an increased morbidity and all-cause mortality[2], adverse surgical outcome[4-6, 27] and mortality in septic patients.[28, 29] On the other side, in a recently published retrospective study on the prevalence of diastolic dysfunction and postoperative outcomes, no significant association was found between diastolic dysfunction and in-hospital mortality or acute kidney injury.[30] In another recent study no association between diastolic dysfunction and need of intra-operative norepinephrine was observed.[31] Notwithstanding, patients with higher grade diastolic dysfunction have an impaired capacity to manage haemodynamic alterations and are at an increased peri-operative risk.[1] Thus, for elderly and/or patients with risk factors or symptoms, especially in intermediate or high-risk surgery, pre-operative echocardiographic screening conducted by anesthesiologists would allow for a proactive anesthesia plan to minimize intra-operative hemodynamic instability and perioperative complications. Implementation of a revised pre-operative risk assessment including anesthesiologist-performed TTE to screen for the most common and/or serious cardiac pathology (e.g. LV diastolic and systolic dysfunction, major valvular disease, hypertrophic obstructive cardiomyopathy and severe hypovolemia) may face several challenges[12, 32, 33], but might be included in the concept of peri-operative surgical home introduced recently.[32, 34] Availability of equipment, theoretical knowledge, expert supervision, and training in both simulator and practice are all essential factors for a successful implementation.[35] However, it ought to be possible with a robust educational plan.[32, 36-38]
Limitations
This single-centered observational study had a rather small sample size and despite a consecutive unselected enrollment, a vast majority of the included patients were women (partially explained by a high amount of breast cancer surgery in the hospital). Larger, multi-centered studies evaluating e’-velocities as a point-of-care assessment of diastolic dysfunction as well as the impact on post-operative outcome, are warranted. All examinations were conducted by expert sonographers to minimize diagnostic bias and a high reproducibility was obtained. In addition, only four patients were excluded due to unusable image quality. The accuracy of evaluated tests may decrease with a less experienced observer, and this may decrease the applicability of the study results. In this study, the diagnosis and grading of diastolic dysfunction were conducted with the recommended parameters from 2009 American Society of Echocardiography (ASE) guidelines[18], with the exception of deceleration time (DT), and the results are based on this data. The 2016 ASE guidelines[26] brings a substantial number of patients with indeterminate diastolic function (Supplementary file 1) and were not used in this study. High-sensitive troponin I may be used for risk stratification at a cut of level of <5 ng L-1, i.e., well below the concentration used to diagnose myocardial infarction.[21, 39] Most of the patients in the current study had a level ≥5 ng l-1, but the study sample size was too small to evaluate significance of hs-TnI for cardiac risk assessment. In addition, the aim of this pre-operative study was to evaluate the accuracy of e’ and E/e’ in order to identify and grade diastolic dysfunction, and no intra- and postoperative data were analyzed. Hence, association between e’-velocities and/or E/e’ and intra-operative hemodynamic stability and postoperative outcome was not assessed in this study.