Left Bundle Branch Block with Less Than 1 mm of Concordant ST Elevation (in the Setting of Hypertrophic Cardiomyopathy)
Posted May 03 2013 1:39pm
A male in his 60's with a known history of hypertrophic cardiomyopathy (HOCM) presented for chest pain. He thought it was "acid reflux," and it started a few hours prior to his presentation to a non-PCI capable hospital. He denied any associated symptoms. His pain was not relieved with NTG. He had an minimally elevated troponin at the referral institution, (assay unknown). He was diaphoretic and clutching his chest. Here is the first ECG
There is sinus rhythm with LBBB and high voltage, and all leads have appropriate and proportional discordance EXCEPT for lead V4, which has less than 1 mm of (inappropriate) concordant ST elevation. Lead V5 also has significantly less discordance than expected.
Definitions in Left Bundle Branch Block:
Appropriate Discordance: The ST segment (and usually the T-wave) should be in the opposite direction of the majority (not the end) of the QRS in all leads. It should be proportionate, with the ST/S ratio being < 0.25 or ST/R ratio < 0.30.
Concordance: When the ST segment and/or T-wave is in the same direction as the majority of the QRS. This is abnormal for LBBB and, if 1 mm, a specific sign of STEMI-equivalent.
Modified Sgarbossa Rule: Any one of1. 1 mm of concordant ST elevation in at least one lead. Usually leads I, aVL, V5 and V6. May also involve inferior leads. 2.1 mm of concordant ST depression in at least one of leads V1-V3. 3.Excessively discordant ST elevation, as measured by ST elevation (at the J-point, relative to the PR segment) to S-wave ratio of > 0.25
What should the ECG look like if there is both HOCM and LBBB? I don't think anyone knows.
The patient was transferred to a PCI capable hospital where this ECG was recorded
Now the concordant ST elevation is in lead V5, but since V4 now has a predominantly negative QRS, the difference is a result of lead placement differences between the two ECGs. V6 has an inappropriately isoelectric ST segment.
An ECG from 5 years previous was available
This shows inappropriate concordance of less than 1 mm in V4, and inappropriate isoelectric ST segments in V5, so all this configuration is not new for this patient who has known HOCM.
Out of an abundance of caution, the cath lab was activated and the coronaries were clean.
The troponin at the referral institution was normal.
The echocardiogram showed
Normal estimated left ventricular ejection fraction, about 60%. Left ventricular hypertrophy concentric, marked. Dynamic left ventricular outflow/subvalvular obstruction (due to HOCM) Asynchronous interventricular septal motion due to left bundle branch block.
The patient developed abdominal pain in addition to chest pain, had a tender abdomen, and was diagnosed with cholecystitis!!!
1. Perhaps HOCM in the setting of LBBB can have concordant ST elevation 2. Concordant ST elevation of less than 1 mm has a specificity less than if it is greater than 1 mm 3. Troponins at or near the 99% cutpoint may give discordant results, especially with different assays.