The Links Between Echocardiographically Determined Biventricular Function and Prognosis

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Pioneered for very ill infants, extracorporeal membrane oxygenation (ECMO) is now used increasingly often for adults with heart, lung or combined heart-lung failure. Echocardiography has become an invaluable aid to these emerging applications of ECMO.

Prior to cannulation, echocardiography is used to search for any contraindications. During the ECMO period, it can be used to ensure proper cannula positioning, assess cardiac function and adequate decompression of the left ventricle and monitor patients for complications such as tamponade and left ventricular (LV) clot. Echocardiography is also valuable during weaning of ECMO and after decannulation to monitor myocardial recovery and work up any hemodynamic instability.

Because the widespread use of adult ECMO is relatively new, there are no strict guidelines for these echocardiographic assessments. Now, anesthesiologists Adam A. Dalia, MD, MBA, and Gaston A. Cudemus, MD, both of the Department of Anesthesia, Critical Care and Pain Medicine, and their colleagues have published in the Journal of Cardiothoracic and Vascular Anesthesia, the links between echocardiographically determined biventricular function and the prognosis of ECMO patients.

A Retrospective Study

As part of this study, the researchers reviewed the charts of 249 adults who underwent ECMO between 2009 and 2017. Patients were divided into those who had venoarterial versus venovenous ECMO and those who did or did not survive until hospital discharge.

For each group, the researchers collected echocardiographic assessments of LV and right ventricular (RV) function before, during and after decannulation. There were 175 patients (102 nonsurvivors, 73 survivors) in the venoarterial group and 74 (33 nonsurvivors, 41 survivors) in the venovenous group. Not all patients had echocardiography examinations at each time point or both ventricles.

At the time of ECMO, physicians reported quantitatively and qualitatively on LV function and qualitatively on RV function. The researchers assigned each of those examination results a numeric score ranging from one (akinetic) to five (normal or hyperkinetic).

Venoarterial ECMO

Patients who survived after venoarterial ECMO had significantly better post-decannulation LV and RV function than nonsurvivors, and the difference was statistically significant. The average LV function was 3.8 ± 1.7 (mildly dysfunctional) in survivors and 2.8 ± 1.5 (moderately dysfunctional) in nonsurvivors (P<.0001).

The researchers note that the difference between survivors and nonsurvivors was also clinically significant, as there was a full point of improvement. Nevertheless, they say, the variance of 1.7 in survivors and 1.5 in nonsurvivors makes it unclear whether this parameter alone has prognostic utility.

For RV function, survivors had an average post-decannulation score of 3.9 ± 1.8 (mildly dysfunctional) and nonsurvivors had an average of 3.3 ± 1.7 (moderately dysfunctional; P = .007).

Although that difference in function was statistically significant, it would be difficult to detect clinically, the researchers point out. Because of the complex geometry of the right ventricle, its function is hard to assess qualitatively.

Venovenous ECMO

Among patients who underwent venovenous ECMO, there was no significant difference in LV function between survivors and nonsurvivors. However, RV function was significantly better in survivors at 4.4 ± 1.2 (mildly dysfunctional) than in nonsurvivors at 3.3 ± 2.2 (moderately dysfunctional; P = .01).

According to the researchers, these findings suggest that the right ventricle is extremely important in patients on venovenous ECMO. They caution that the results must be considered preliminary because there were only a small number of assessments, and the large variance makes it difficult to establish a cutoff value for prognostication.

But if the data are not a statistical anomaly, the authors continue, it might be possible to improve outcomes by frequently assessing and optimizing RV function during the post-decannulation phase for patients with poor RV function. They also believe it would be worthwhile to assess whether substituting venovenous ECMO for venoarterial ECMO in certain patients with RV dysfunction could reliably improve outcomes.

Differences Between Study Periods

For measuring differences in function between study periods, the researchers included only patients who had reports on LV and RV function before and during ECMO and after decannulation. Altogether, 83 patients who underwent venoarterial ECMO and 30 who underwent venovenous ECMO had complete datasets.

Between cannulation and post-decannulation, average improvement in LV function was 1.2 points in survivors and 0.26 points in nonsurvivors (essentially no clinical improvement). The numbers were similar for RV function.

Between pre-cannulation and post-cannulation, survivors demonstrated an improvement in biventricular function and survivors demonstrated a small setback. Unfortunately, large variance-to-actual differences again made a specific cutoff value for prognostication purposes difficult to select.

The researchers conclude that the study period results reinforce clinician concerns about the prognosis of patients who do not demonstrate significant improvements in biventricular function from before ECMO to after decannulation. They recommend that such patients be considered for more prolonged monitoring in anticipation of complications.

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