Echocardiography plays a pivotal role in various stages of managing critically ill patients on VA ECMO, providing essential information for therapeutic decisions, evaluating responses, and early detection of complications. However, despite its widespread and increasing use, there remains a lack of standardization for necessary parameters and their cutoff values, as well as their potential prognostic value. This study aimed to evaluate the presence and timing of specific “critical” echocardiographic findings and analyze their correlation with in-hospital mortality.
This retrospective study collected clinical, hemodynamic, and echocardiographic data from 130 patients receiving VA ECMO support for cardiogenic shock from diverse etiologies between 2011 and 2018 at Toronto General Hospital, Canada. Data included causes of cardiogenic shock, patient baseline characteristics, validated “survival after veno-arterial ECMO (SAVE)” score, need for left ventricular decompression, survival, and cause of death. Transthoracic (TTE) and transesophageal (TEE) echocardiograms were reviewed, categorized temporally into three groups: the first (within 36 hours post-cannulation), the last (pre-decannulation), and the intermediate. Critical echocardiographic findings were defined as minimal or absent ejection, intracavitary thrombus, pericardial effusion, and cannula malposition.
A total of 236 TTEs and 296 TEEs were analyzed in 126 patients, with a mean support duration of 6.8 ± 4.8 days. The initial echocardiogram showed the highest incidence of critical findings (34.7%): minimal or absent left ventricular (LV) ejection was observed in 23.1% of cases, intracavitary thrombus in 6.6%, tamponade in 4.1%, and cannula malposition in 0.8%. Presence of these parameters was associated with an increased in-hospital mortality with an OR of 2.32 (p = 0.037). In patients without these findings on the first echocardiogram, critical findings appeared in 2.4% of intermediate and 11.3% of final studies. Additionally, the presence of any critical echocardiographic parameter was linked to increased mortality (OR 2.72; p = 0.011).
The authors conclude that echocardiographic monitoring is vital in managing VA ECMO patients, with those at higher risk potentially benefiting from more frequent evaluations to identify prognostic findings.
COMMENTARY:
VA ECMO provides short-term circulatory and respiratory support for patients in cardiogenic shock unresponsive to conventional medical management. However, a notable proportion of patients fail to recover or continue to deteriorate despite its use. Partially due to delayed initiation in cases presented or transferred late to ECMO-capable centers, or when the decision is made after advanced multi-organ failure onset. Additionally, potential complications from ECMO use may have drastic consequences for the patient, alongside common critical care complications like infections. Consequently, in-hospital mortality for cardiogenic shock in contemporary series remains high despite VA ECMO support, reported around 56%. In this study, a similar in-hospital mortality rate of 58.5% was observed, with ECMO-related mortality at 3.9%. The mean age of patients was 48 years (range: 19–75), with higher mortality in older patients (p = 0.004). The authors examined the SAVE score as a prognostic clinical parameter. SAVE, a tool for predicting in-hospital survival for VA ECMO patients based on clinical data, was validated with data from the international ELSO registry and externally in an Australian cohort. A lower SAVE score also correlated with mortality in this study (p < 0.001).
Patients with various etiologies of cardiogenic shock were included, including some associated with lower VA ECMO survival rates, such as post-cardiotomy (39.2%), congenital heart disease (8.5%) (both part of SAVE score), and post-cardiac arrest (20.8%). However, critical echocardiographic findings were not associated with shock etiology in this study. The mode of VA ECMO (peripheral vs. central) was not specified, precluding conclusions on this aspect. No differences were found in patients with new prostheses (OR 1.06; p = 0.93), though the type was unspecified. Nearly half of the deaths (47.4%) occurred due to irreversible multi-organ failure post-decannulation. No cases or reasons were given for potential progression to long-term support or heart transplant. Other non-cardiac deaths included 17.1% from neurological complications and 19.7% from sepsis.
Echocardiography’s low cost, wide availability, and bedside utility make it the primary imaging choice for VA ECMO patients, complementing hemodynamic data on myocardial recovery and helping to address situations where anticipated improvements do not occur. The authors previously published a review of their relevant contributions in this context. Several prior studies have described echocardiographic parameters related to successful VA ECMO weaning, though a direct link between weaning parameters and discharge survival has yet to be established. In the current study, the authors went further by validating the prognostic use of echocardiography, correlating specific critical parameters with mortality, a previously unproven link.
Selected echocardiographic parameters reflect adverse hemodynamic conditions in VA ECMO patients:
- Minimal or absent ventricular ejection (without specific cutoff): In patients with VA ECMO, the LV has decreased systolic function, preload, and myocardial reserve, potentially hindering forward ejection. This may worsen due to increased LV afterload from ECMO return flow, which in severe cases, may prevent aortic valve opening.
- Intracavitary thrombus: Resulting from increased myocardial oxygen consumption, subendocardial ischemia, and functional impairment, this can create a stasis leading to thrombus formation despite systemic anticoagulation.
- Pericardial effusion: Diagnosing tamponade in VA ECMO is challenging due to altered hemodynamics; thus, any pericardial effusion should be monitored closely with clinical and hemodynamic deterioration in mind.
- Cannula malposition or vascular injury: While the centrally or peripherally placed arterial return cannula is often inaccessible for echocardiography, the venous cannula extracting blood from the right atrium is usually visible. Malposition can cause serious complications, including thrombus formation in the cannula lumen, linked to increased mortality in pediatric VA ECMO patients.
In this study, the presence of any of these findings in the initial echocardiogram correlated with in-hospital mortality, with higher prevalence among patients with low pulse pressure (OR 5.58; p < 0.001) and those requiring LV decompression (PR 7.00; p < 0.001). This supports early or even prophylactic decompression measures based on echocardiographic findings to prevent early mortality in VA ECMO patients.
Regarding the modality, though direct comparisons between TTE and TEE in VA ECMO are lacking, TEE generally offers superior spatial resolution, critical in patients with limited acoustic windows. However, its invasive nature entails risks in anticoagulated patients. In this study, TTE and TEE use was nearly equal, with contrast echocardiography applied in 17.5% of cases to enhance TTE resolution. Contrast effect duration is reduced in VA ECMO due to microbubble destruction in the circuit, necessitating focused, brief evaluations. Notably, no complications were reported from contrast use, enhancing its safety in this context. All consoles used were Centrimag, without bubble detection systems. Other consoles might integrate ultrasound sensors that detect bubble or thrombus-associated flow changes. Although contrast bubble size is generally small, high-sensitivity consoles might trigger alarms, causing ECMO flow cessation with potentially catastrophic consequences. Therefore, checking the console’s detection systems and disabling them before using contrast, or opting for TEE over TTE with contrast, is recommended.
In summary, mortality in cardiogenic shock remains high despite short-term circulatory support systems. Echocardiography is invaluable for these patients, and early identification of critical echocardiographic parameters can aid in recognizing patients at higher risk who may benefit from early interventions or closer monitoring. Contrast echocardiography has proven safe with consoles lacking bubble detection.
REFERENCE:
Siriwardena M, Brahmbhatt DH, Douflé G, Fan E, Billia F. Prognostic echocardiographic findings in patients supported with venoarterial extracorporeal membrane oxygenation for cardiogenic shock. Eur Heart J Acute Cardiovasc Care. 2023 Apr 13. doi: 10.1093/ehjacc/zuad038
Douflé G, Roscoe A, Billia F, Fan E. Echocardiography for adult patients supported with extracorporeal membrane oxygenation. Crit Care. 2015 Oct 2;19:326. doi: 10.1186/s13054-015-1042-2
