Critical care ultrasound has gained its place as an effective and convenient monitoring tool, which become the “visual stethoscope” of the 21st century[15,16]. Echocardiography is an important part of critical care ultrasound, which allows for an anatomical, functional, and hemodynamic assessment of the heart, and has revolutionized the bedside assessment of ICU patients. Many different types of FOCUS exams have been introduced to the emergency departments or ICUs. Previous studies have reported that FOCUS performed by emergency medicine residents is comparable to echocardiography performed by cardiologists. Therefore, echocardiography is a reliable tool and screening test for cardiac abnormalities. After a brief standard training in using echocardiographic system, intensivists can successfully performed and correctly interpreted a focused TTE for critically ill patients. Chest ultrasonography is a valid bedside diagnostic aid to the management of acute respiratory diseases in older patients. FOCUS can be an important tool in the initial evaluation of emargency patients with suspected pulmonary embolism and abnormal vital signs. In cardiac-arrest patients, after return of spontaneously circulation, FOCUS could be included in post-resuscitation care as an adjunctive diagnostic measure. CCUE-plus protocol was effective in the etiological diagnosis in patients with dyspnea and/or hemodynamic instability caused by abdominal abnormalities. However, the prognostic value of echocardiography in ICU patients is seldom studied. It was reported that CCUE protocol could improve the bedside treatment of critically ill patients, and reduce ICU stay. A FOCUS examination for right ventricular strain performed by emergency care practitioners was a significant predictor of in-hospital adverse outcomes among patients diagnosed with pulmonary embolism in the Emergency Department. But the role of echocardiography performed early during admission in general ICU patients has not been assessed in a multiple center cohort. In this study, we described the characteristics of echocardiography manifestation in different groups of ICU patients, and analyzed their associations with outcomes.
This study included 1682 patients from the ICUs in different parts of China. The mean age of the participants was 59.48±17.363 years, and the mean APACHE II score was 15.32±8.452. The overall 28-day mortality was 15.76% (265/1682), which is in line with the general level of ICU patients. We applied echocardiography to these general ICU patients with different primary indications, and analyzed its relationship with the 28-day mortality. Results showed APACHE II scores, the length of MV, HR, MAP and Lac were significantly different between the non-survivors and the survivors. Left ventricle enlargement and other echocardiogram abnormalities were more frequent in the non-survivors than the survivors. The incidence of right ventricle enlargement (446/1682, 26.52%) and EF decrease (453/1682, 26.93%) was high in ICU patients. The EF value was significantly lower, and the decrease in EF value was more frequent in the non-survivors than the survivors. These results indicated that the incidence of cardiac dysfunction was high in ICU patients. Echocardiography at the admission of ICU helps early detection of cardiac abnormalities.
Then we analyzed the characteristic of echocardiography in subgroups with different primary diseases. In patients with acute respiratory failure, the incidence of right ventricle enlargement was even higher (178/533, 33.40%). IVC variability abnormal was more frequent in the non-survivors than the survivors. IVC diameter is a useful mirror of the right atrial pressure (RAP), and IVC variability is a reliable index for assessing fluid responsiveness[13,14]. This indicated that unsuitable volume status might be an important factor for the mortality of acute respiratory failure patients. However, the echocardiography score was not significantly different between the non-survivors and the survivors. A probable reason was that cardiac abnormalities were common in patients with acute respiratory failure, thus the difference was not obvious between groups.
In patients with shock, in echocardiography examinations, only other echocardiogram abnormalities were significantly different between the non-survivors than the survivors. Other cardiac abnormalities including pericardial effusion, heart valve abnormalities, pulmonary hypertension, ventricular wall segmental dyskinesia, were important clinical conditions leading to heart failure and deterioration of diseases. In shock patients, there was no significant difference on EF values between groups, probably because most of the shock patients included in this study were septic shock instead of cardiogenic shock. Also, the echocardiography score was not significantly different between the non-survivors and the survivors, probably because cardiac abnormalities were common in patients with shock.
In postoperative patients, left ventricle enlargement, left ventricular wall thickening, right ventricular wall thickening and other echocardiogram abnormalities were more frequent in the non-survivors than the survivors, indicating that primary heart diseases were important factors for the mortality of postoperative patients. The EF value was significantly lower, and EF<30% is more frequent in the non-survivors than the survivors, indicating that cardiac systolic dysfunction was also important for the outcome of patients. Previous studies has reported that LV ejection fraction <45% was associated with the absence of early recovery and less favorable 1-year outcome in patients with Takotsubo Syndrome. A scoring system including EF is a predictor of 30-day mortality risks for ST-Elevation Myocardial Infarction patients. The echocardiography score was significantly higher in the non-survivors than the survivors. These results indicated that echocardiography screen was important for post-operative patients. And abnormal findings in echocardiography may help divide the non-survivors and survivors.
When analyzing the risk factors for 28-day mortality, the independent risk factors was APACHE II, the length of MV, the length of ICU stay, oxygenation index, right ventricular wall thickening, IVC diameter, IVC variability and the echocardiography score. These data indicated that volume status and fluid responsiveness were critical for the mortality of ICU patients. However, a previous study using IVC variability <20% as the end-point of fluid resuscitation in septic shock requiring ventilatory support did not found significant difference in the amount of fluid infused, time to reach end-point and mortality with the regular care group. As there are few studies on the relationship between IVC variability and mortality, it deserves further study.
In this study, we developed a scoring system by assessing atrium and ventricle enlargement, ventricular wall thickening, IVC diameter and variability, EF, and other echocardiogram abnormalities, therefore to generally evaluate the structural, systolic, diastolic and volumic abnormalities. We found that the echocardiography score was significantly higher in the non-survivors than the survivors. Also, it was an independent risk factor for 28-day mortality. These results indicated that echocardiography makers that reveal the general cardiac function could help to predict the outcome. However, the AuROC of echocardiography score for predicting the 28-day mortality was only 0.595, indicating that it is not a reliable outcome predicting marker. Therefore, this echocardiography score may be better used in combination with other risk factors of mortality.
This study is a multiple center study that comprehensively investigated the characteristics of echocardiography manifestations and their prognostic importance in a larger cohort of ICU patients. However, our study has some limitations. First, as many clinical indicators were not completely recorded in different participating sites, we only analyzed the most complete baseline data including the age, gender, primary indications, HR, MAP, Lac, APACHE II scores, length of MV, length of ICU stay, and 28-day mortality. However, many laboratory indexes were not analyzed because of too many missing data. Second, most participating ICUs are general ICUs, with relatively more surgical patients and fewer internal medical patients. Therefore, a large proportion of the included patients were postoperative patients with less severe conditions.