Wednesday, December 11, 2013

Pseudoanteroseptal STEMI in the Setting of Paced Rhythm

This is a case we published in JAMA internal medicine this year.  I can't give you the full text, but even limited access is pretty good.  You can read the history there as well.  Here is the link:

What is the diagnosis?  See below for answer.

There is a paced rhythm with PVCs.  There is excessively discordant ST elevation, as measured using the Modified Sgarbossa Rule for Left Bundle Branch Block.  There is no data on the use of this modified rule for Paced Rhythm, but it is fairly well accepted that the same concordance/discordance rules apply to paced complexes that we use in LBBB (see annotated bibiliography below).

The excessive discordance is in BOTH inferior leads and anterior leads (II,III,aVF and V2-V4, with some concordance in V1).  Is this an anterior and inferior STEMI, right?

But there are two ventricles that are recorded with anterior leads: both right and left ventricle.  Could this be an RCA occlusion with both inferior and RV infarct, in the setting of paced rhythm?  The fact that there is shock and clear lungs (RV, but not LV, failure) supports this.

In fact, angiography revealed an RCA occlusion proximal to the RV marginal branch which supplies the RV.

1. Inferior STEMI with anterior ST elevation can be due to:
     a) A wraparound LAD that supplies the inferior and anterior walls of the LEFT ventricle or
     b) An RCA occlusion proximal to the RV marginal, without collateral circulation to the RV from the LAD.
2. RV infarct is associated with hypotension and clear lungs (RV failure, not LV)
3. Not all proximal RCA occlusions result in clinical RV infarct.  The LAD often has small branches that will give the RV enough blood supply so that only a minority of proximal occlusions reveal themselves with RV ST elevation and hypotension.

Anterior ST elevation due to RV infarct is often called "Pseudoanteroseptal MI"  See literature below.

Here is one case of pseudoanteroseptal MI in normal conduction.
Here is another case of Pseudoanteroseptal MI, with cardiac arrest.

Annotated Bibliography on STEMI in Paced Rhythm, Pseudoanteroseptal MI, and RV MI in LBBB:

AMI in paced rhythms 

1.  Maloy KR, Bhat R, Davis J, Reed K, Morrissey R. Sgarbossa criteria are highly specific for acute myocardial infarction with pacemakers. West J Emerg Med. 2010;11(4):354-357.3.; 

     The authors assessed the Sgarbossa criteria in 57 cases of paced ECG in biomarker-diagnosed AMI (not angiographic occlusions), and compared them to 99 troponin negative paced controls who were otherwise of comparable age and sex.  There were no cases of concordant ST elevation.  Concordant ST depression in one of leads V1-V3 had sensitivity of 19% (95% CI 11–31%) and specificity 81% (95% CI 72–87%).  For ST-segment elevation >5mm and discordant with QRS complex, the sensitivity was 10% (95% CI 5–21%) and specificity 99% (95% CI 93–99%).  They do not tell us how many met each criterion.  Only one patient (a control) met both criteria, so even though they do not give us the actual numbers in the paper, it appears that the sensitivity of the overall rule was 29%.  Given that only about 30% of troponin diagnosed MI are STEMI-equivalents (occlusion or near occlusion, as opposed to Non STEMI), this is surprisingly high sensitivity for a group that had no concordant ST elevation.

2. Sgarbossa EB, Pinski SL, Gates KB,Wagner GS; GUSTO-1 Investigators. Early electrocardiographic diagnosis of acutemyocardial infarction in the presence of ventricular paced rhythm. Am J Cardiol. 1996;77(5):423-424.

The authors analyzed data from GUSTO-1. They looked at all patients in the study who had a paced rhythm and were diagnosed with AMI and included in the GUSTO trial.  Many physicians, however, have been reluctant to make this diagnosis and to enter a patient with chest pain and a paced rhythm into a thrombolytic trial.  Consequently, only 32 patients (0.1%) with pacemakers were included in GUSTO-1, which is much lower than the percentage of patients with CP and AMI who have a ventricular pacemaker.  We do not know the incidence of (and therefore the pre-test probability of) AMI in patients with CP and a pacemaker and this study provides no helpful data in that regard.  Fifteen of these 32 patients were excluded because their rhythms were not generated by the pacer.  The ECG’s of the 17 remaining AMI patients were matched with 17 patients with pacers, stable CAD and no CP.  The ECG criteria developed by Sgarbossa et al. (246) for LBBB were then tested on patients and controls.  Results, as follows, were similar to those in the LBBB study.
·       --ST elevation >/= 5 mm in one lead with a predominantly negative QRS was the only criterion that had statistical significance and high specificity (positive likelihood ratio = 4.41).
Additional findings that could be useful but were not statistically significant:
·       --ST elevation >/= 1mm in leads with predominantly positive QRS (sensitivity 53%, specificity 88%).
·       --ST depression of >/= 1mm in one of leads V1-V3 (sensitivity 29%, specificity 82%).

"Pseudoanteroseptal AMI" in normal conduction

3. Khan ZU, Chou TC. Right ventricular infarction mimicking acute anteroseptal left ventricular infarction.  Am Heart J 1996; 132:1089-1093.
The authors studied 4 patients whose concurrent inferior and RV AMI mimicked inferior and anteroseptal LV AMI and found that the ECG’s of all patients showed ST elevation not only in V1, but also in V2-V3. More surprising still was the development of Q-waves in V1-V3 without the presence of anterior AMI.

4. Geft IL, Shah PK, Rodriguez L, et al. ST elevations in leads V1 to V5 may be caused by right coronary artery occlusion and acute right ventricular infarction. Am J Cardiol. 1984;53(8):991-996.
These authors used angiography and scintigraphy to study 69 patients with ST elevation in V1-V5 and found that the RCA was occluded, the LAD was open, and the RV was the area of infarct in 5 patients (7%).   In cases of anterior AMI due to LAD occlusion, ST elevation was least in V1 and maximal in V2 to V4, whereas in RV AMI, ST elevation was highest in V1-V2 and decreased toward V5.  RV AMI’s were also associated with inferior ST elevation.

Pseudoanteroseptal MI in LBBB

5. Smith SW, HeegaardW, Bachour FA, BradyWJ.  Acute myocardial infarction with left bundle-branch block: disproportional anterior ST elevation due to right ventricular myocardial infarction in the presence of left bundle-branch block. Am J Emerg Med. 2008;26(3):342-347.

We reported here a case of precordial and inferior ST elevation in LBBB that was due to inferior and RV STEMI.

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