It is dilated. This is very suggestive of high right sided pressures. But that by itself does not help in the diagnosis, because shock from both LV STEMI and PE would increase right sided pressures.
There was a discussion about whether this represented PE or STEMI. Treatment options were considered including TPA or cath lab activation. A second EKG was recorded:
Comment: What is going on?Salient facts:
The patient had sudden SOB with severe hypoxia and shock, but with clear lungs.
Ultrasound further confirmed this with absence of B-lines (not recorded)
Furthermore, a low end tidal CO2
, though also associated with cardiac arrest, is common in patients with massive pulmonary embolism. Because the lungs are ventilated but not perfused, the CO2 cannot be excreted through the airways and the etCO2 is low.
One might be tempted to attribute right sided failure to inferior MI with right ventricular MI and RV failure, but RV failure from RV MI does not cause hypoxia
Acute STEMI only causes hypoxia if it results in pulmonary edema.
This patient had clear lungs. When patients have severe pulmonary edema, the gas exchange is poor, and areas of the lung that are ventilated are OVER-perfused (causing pulmonary edema) and the end tidal CO2 (and arterial and venous pCO2) are high
because the alveoli are filled with fluid.
A chest X-ray, taken 5 minutes after the ECG was recorded, confirmed clear lungs
|There is no pulmonary edema|
The ECG findings were more pronounced now with ST elevation in II, III, aVF, and V4-V6. The cath lab activation was confirmed.
The patient became bradycardic and hypotensive. tPA was given.
Another echo was done:
There is now worsening function of both ventricles.
There was no response to norepinephrine infusion nor to external pacing. He soon became pulseless and compressions were started. The resuscitation was continued for a prolonged period but the patient remained in PEA and never achieved ROSC. No autopsy was performed. Learning Points
1. Hypoxia with clear lungs is pulmonary embolism until proven otherwise (see other etiologies below)
2. STEMI only causes hypoxia by causing pulmonary edema
3. Massive Pulmonary Embolism can result in a STEMI ECG, identical to ACS STEMI. (I have seen this numerous times but this is the first time I've posted one)
4. Low end tidal CO2 is typical of massive PE. High end tidal CO2 is typical of severe pulmonary edema.
5. Shock from STEMI has unmistakably poor LV function and on bedside echo
6. RV failure from RV MI does not cause hypoxia.
7. Perhaps most important:
if the differential is STEMI vs. massive PE, just give the tPA, front loaded (100 mg). There is no contraindication to angiography and PCI for a patient who has received thrombolytics and remains in shock.
In fact, it is the therapy that is recommended therapy for patients who are in shock and need to be transferred to a PCI capable institution.
(Certainly if you know without doubt that STEMI is the diagnosis, then do not give tPA if you are at a PCI capable institution and rapid PCI can be done.)Hypoxia with clear chest X-ray
1. Pulmonary Embolism.
3. Hypoventilation (high pCO2)
4. Sepsis (pulmonary vasodilation and shunting)
5. Anatomic right to left shunt (VSD etc.)
6. Vasodilators such as nitroprusside (cause pulmonary vasodilation and shunting)2013 STEMI Guidelines. JACC 61(4):p. e97
5.3. Transfer to a PCI-Capable Hospital After Fibrinolytic Therapy
5.3.1. Transfer of Patients With STEMI to a PCI-Capable Hospital for Coronary Angiography After Fibrinolytic Therapy: Recommendations.
1. Immediate transfer to a PCI-capable hospital for coronary angiography is recommended for suitable patients with STEMI who develop cardiogenic shock or acute severe HF, irrespective of the time delay from MI onset (354). (Level of Evidence: B)
Also in this section:
Angiography and PCI may be done also for:
2. Patients with STEMI who receive thrombolytics at an outside hosptial and do not have reperfusion (as determined by EKG) should go immediately for PCI.
3. Patients who have successful reperfusion with thrombolytics should wait 2-3 hours for their PCI.