Click on the button below to go to the main page:
Click on the button below to go to the previous page:
PULMONARY EMBOLUS
The echo features of acute RV pressure overload are:
1. Dilated RV (1:1 with LV; >3cm on PLAx)
2. Dilated RA
3. Decrease TAPSE <17mm
4. McConnell's sign
5. Plethoric IVC
6. Clot in transit: RA, RV, Pulmonary artery
Along with this, the LV with be hyperdynamic and have a D shape in PSAx.
Echo lacks the sensitivity to diagnose PE. Small PEs and even subsegmental PEs may have a normal echo. A recent systematic review showed that only 80% of patients with a confirmed PE have a dilated RV on echo (1). Thus echo is only a rule in test.
I use bedside echo in normotensive patients with suspected PE, to look for signs of right heart strain and risk stratify the patient prior to CT. I am more likely to fully anticoagulate them prior to CT if they have signs of right heart strain. If they then arrest in ED prior to CT, I am more likely to reach for thrombolysis as first line therapy. I am more likely to book a CCU bed etc.
Bedside echo is a RULE IN test for PE
FEATURES OF RIGHT HEART STRAIN
A proximal PE causes signs of acute right ventricular pressure overload. When present, they are highly specific for the diagnosis of PE.
Specificity and LR for signs of right heart strain from Fields et al (1)
RV DILATATION
Remember that the RV is normally 2/3 the size of the LV. A dilated RV is diagnosed based on the impression that it is 1:1 or bigger than the LV, the RVOT in PLAx is >3cm and/or the base of the RV in A4C is > 42mm.
In PLAx, the RV height should be the same size as the ascending aorta and the LA.
In this clip, the RV is clearly bigger than the Aorta and LA
RV dilatation is probably best appreciated in PSAx. In this view, the RV usually drapes over the LV like un underfilled waterbaloon. With pressure overload, it sits on the LV like a large stone and causes the IV septum to become straight or curve into the LV: creating the D shaped LV.
SEPTAL BOWING TO THE LEFT
Normally the interventricular septum bows to the right in systole. In acute RV pressure overload, the IV septum bows to the left in systole. This is best seen in PSAx: The LV which is normally round becomes D shaped due to the septal bowing.
RV FREE WALL HYPOKINESIS
With acute pressure overload, the RV dilates and it's walls don't contract well. This is seen in the A4C (see clip above) as decreased vertical movement of the lateral annulus of the tricuspid (TAPSE <17mm). In PLAx you will see that the RV cavity changes little between systole and diastole.
McCONNELL'S SIGN
This is where a dilated hypocontractile RV still has a briskly contracting apex. Although the systematic review by Fields et al (1) shows that this sign has a high specificity for PE, it may also be present in patients with RV dysfunction due to chronic pulmonary hypertension and right ventricular infarction (2).
A4C: McConnell's Sign
RA ENLARGEMENT
Acute RA enlargement in PE is associated with increased mortality (3,4). Sometimes, this maybe the only sign of right heart strain on the bedside echo in a patient presenting with acute symptoms. Apical four chamber and subxyphoid are probably the best views for this.
RIGHT HEART THROMBUS
Kind of a no brainer. If you see a clot in the right side of the heart: this is likely a PE.
Subxyphoid: showing a mobile hypoechoic mass in the RA
A clot will usually be mobile and hypoechoic.
The differential diagnoses for this are
1. RA tumour (usualy adherent to the wall)
2. congenital: eustacian valve, crista terminalis, chiari network
3. implanted devices eg pacemaker wires (usually very hyperechoic)
4. vegetations associated with a valve
HYPERDYNAMIC LV
Due to lack of venous return to the left side, the LV cavity becomes small and the LV is hyperdynmic. In PSAx, the LV is seen to be D shaped due to septal bowing to the left in systole.
The IVC will normally be plethoric with acute RV pressure overload..
An acutely dilated RV can also occur with RV infarct, mediastinal mass causing extrinsic compression of the pulmonary artery and maybe a tension pneumothorax.
Click on the button below to go to the next page:
REFERENCES
1. Fields JM, Davis J, Girson L, et al. Transthoracic echocardiography for diagnosing pulmonary embolism: a systematic review and meta-analysis. J Am Soc Echocardiogr2017;30:714-23.
2. Walsh BM, Moore CL. McConnell's Sign Is Not Specific for Pulmonary Embolism: Case Report and Review of the Literature. J Emerg Med. 2015 Sep;49(3):301-4. doi: 10.1016/j.jemermed.2014.12.089. Epub 2015 May 16. PMID: 25986329.
3. Khan UA, Aurigemma GP, Tighe DA. Vector velocity imaging echocardiography to study the effects of submassive pulmonary embolism on the right atrium. Echocardiography. 2018 Feb;35(2):204-210.
4. Chow V, Ng AC, Chung T, Thomas L, Kritharides L. Right atrial to left atrial area ratio on early echocardiography predicts long-term survival after acute pulmonary embolism. Cardiovasc Ultrasound. 2013 May 31;11:17