This is the conclusion of the previous case:Â http://ems12lead.com/2014/01/87-yom-complaining-of-chest-pain-and-dyspnea/
So, as mentioned before, you obtain this 12 lead ECG:
A few minutes later, the LIFEPAK 15 prints out another 12 lead ECG:
Although the computer suggests Atrial fibrillation, this irregular tachycardia has a group beating pattern with presence of P waves prior the QRS complexes and no sign of AV dissociation, which suggests Sinus Tachychardia with Premature Atrial Complexes (PACs)
The patient was able to stand and pivot from the bed to the stretcher with assistance. The patient was placed in sitting position which seemed to help with his breathing. Because of the history, presentation and criteria which we will cover in a moment, EMS did not call a STEMI ALERT, but decided to transport emergency to the closest appropriate receiving facility.
Pre-hospital Treatment: (per local protocol)
- The patient was placed on CPAP at 10 cmH2O per their protocol, and able to tolerate the positive pressure throughout transport.
- The patient was given a total of five 0.4 mg Nitroglycerin (NTG) tablets sublingual every 5 minutes with improvement of chest discomfort to 1/10 pain scale, but pulmonary edema was still present.
- The patient was given 2 mg of bumetanide (Bumex) slow IV push.
- 4 mg Zofran slow IV push for nausea and vomiting.
Upon arrival to the ED, the patient condition had improved drastically, with the following vital signs:
- Blood Pressure: 180/87 mmHg
- Heart Rate: 100 beats/min
- Respiratory Rate: 26 breaths/min
- SpO2: 98%
- ETCO2: 33 mmHg
ED staff and attending physician were presented with the case and STEMI ALERT was activated based on the pre-hospital 12 lead ECG. That is, until a previous ECG was obtained from the patientâ€™s records, which revealed a very similar ECG and the STEMI ALERT was downgraded.
The following 12 lead ECG was obtained at 03:02 hrs, approximately 4 minutes after patient care was transferred to the ED staff.
Now that we have reviewed the case, lets break it down.
Before we move on, lets clarify some terms to avoid confusion:
DiscordanceÂ =Â ST-T vector going the opposite direction of the terminal QRS. In other words, when the QRS is positive, the ST segment and T wave are negative and vise versa.
ConcordanceÂ =Â ST-T vector going the same direction as the QRS.
As previously mentioned, there is excessive discordant ST elevation, > 5mm
Remember Sgarbossaâ€™s Criteria?
It is used to determine STEMI in the presence of a LBBB.
- Concordant ST Segment Elevation > 1 mm in at least one lead = 5 points
- Concordant ST Segment Depression > 1 mm in V1-3 = 3 points
- Excessive discordant ST Segment Elevation > 5mm
When you get 3 points or more, specificity for MI is at least 90%. However, the last criterion is not as sensitive or specific for MI. Because of this,Â Dr. Stephen SmithÂ has developed aÂ MODIFIED SGARBOSSA RULE,Â which replaces the excessive discordance > 5mm criterion:
- ST/T ratio less than or equal to -.25
What does this mean?
- Find the lead with the highest ST segment elevation > 5mm
- Measure the ST segment elevation in millimeters (mm)
- Divide the ST elevation result by the depth of that preceding S wave
- If the result is more than -.25, both sensitivity and specificity for MI increase dramatically, you are almost certainly dealing with STEMI.
Why a negative number?
Because when we divide the ST elevation which is a positive number, by the S wave which is a negative number, we get a negative number.
This also applies to the lead with excessive negative discordance. In other words, a lead ending with a terminal R wave with deep ST segment depression. Divide the ST depression by the height of the R wave
Increased ST segment elevationÂ and voltage canÂ be exagerated by:
- Pulmonary Edema
- Respiratory failure
- Ischemia without occlusion
3rd ECG with ST/T ratio of approximately -.17.5 in V2
Hospital ECG with ST/T ratio of -.12 in V2
- Troponin T (cTnT) was 0.8 ng/L
- B-type Natriuretic Peptide (BNP) > 4,000 pg/mL (BNP is used to assess levels of Heart Failure). Normal is < 100 pg/mL
- Serum Creatine and BUN elevated
Echocardiogram and angiography revealed no severely abnormal wall motion or occluded coronary vessels. The patient was diagnosed with CHF secondary to Acute Renal Failure and was admitted for further treatment and observation.
Next day follow up:
The patient was sitting on the edge of the bed without Cpap or O2, with sinus rhythm and LBBB showing on the monitor and absent Pulmonary Edema.