A dilated right ventricle highly suggests pulmonary hypertension, chronic or acute. Other signs of right heart dysfunction, such as hypokinesis, septal bowing, or McConnell's sign, can also be helpful in diagnosing acute PE. But what about the assessment of patients in cardiac arrest? Does an enlarged right ventricle reliably indicate a PE? Enough to initiate thrombolytics?
A paucity of trials look at right ventricular enlargement in cardiac arrest. The CASA exam, which minimizes pauses in CPR while allowing evaluation of possible causes of cardiac arrest, also includes a quick echo to assess for pericardial effusion to prompt a quick pericardiocentesis, cardiac activity to determine if resuscitative efforts should continue, and right ventricular enlargement as an indication of a massive pulmonary embolism. (EMN. 2019;41:1; http://bit.ly/2Hcwrsf.)
The REASON trial looked at using ultrasound to assess patients with PEA arrest during ACLS. (Resuscitation. 2016;109:33.) As a subset, they evaluated patients who had been given thrombolytics as a result of right ventricular enlargement and suspected PE. Overall, these patients had better outcomes than other patients presenting with PEA arrest, with a survival rate of 6.7 percent v. 3.8 percent for those with cardiac activity on ultrasound. They represented only 15 of 793 patients, however, and their evaluation and treatment were not standardized.
One of the few studies dedicated solely to the question of what a dilated right ventricle indicates in cardiac arrest was done in a porcine model. Pigs were anesthetized, and cardiac arrest was induced by hypoxia, arrhythmia, or pulmonary embolism in this study. (Crit Care Med. 2017;45:e695.) Ultrasound was then performed to assess the effect on the size of the right ventricle. The researchers found that PE caused more RV enlargement than hypoxia or arrhythmia but only with a difference of 7-9 mm. Physicians evaluating the hearts were only able to detect a difference of 10 mm with a sensitivity of 79 percent.
What does this mean for echo in cardiac arrest? Take a dilated right heart with a grain of tPA. Until more evidence indicates otherwise, a big RV can result from multiple causes. Other findings, such as visible thrombus or septal bowing, or even medical history, may be more indicative of acute PE.
Dr. Buttsis the director of the division of emergency ultrasound and a clinical assistant professor of emergency medicine at Louisiana State University at New Orleans. Follow her on Twitter@EMNSpeedofSound, and read her past columns athttp://bit.ly/EMN-SpeedofSound.