The patient may have LBBB and ST Elevation MI

Acute ST elevation MI may present with left bundle branch block. Unfortunately left bundle branch block may both mimic the changes of ST elevation MI and may obscure the diagnosis of ST elevation MI.

Supportive signs and symptoms of ST elevation MI would include:
 * The pain is described as a heaviness or crushing sensation
 * Pain radiating to the left arm
 * Elbow pain
 * Shortness of breath or dyspnea
 * Nausea and vomiting
 * Diaphoresis
 * An elevation of the CK MB enzyme
 * An elevation of the troponin enzyme
 * An elevation of the myoglobin

Pseudoinfarct Patterns: Simulation of an Anterior MI

 * 1) LBBB can cause poor R wave progression. Often see a decrease in the amplitude of R waves to the midprecordium in the absence of a septal infarct.
 * 2) QS complexes are often seen in the right precordial leads in uncomplicated LBBB and they may even extend as far out as V5 or V6.
 * 3) Noninfarctional Q waves may be seen in AVL.
 * 4) The Reason: LBBB causes a loss of the normal septal r waves in the right precordial leads. The septum is no longer being depolarized from left to right as it normally does because of the delay down the left bundle.
 * 5) There can occasionally be Rs complexes in V1. These unanticipated initial positive forces are due to early RV depolarization and may actually mask the q waves (i.e. loss of initial septal forces) that accompany an anteroseptal MI.

Simulation of an Inferior MI

 * 1) Noninfarctional QS complexes can be seen in leads II, III, and AVF in LBBB.
 * 2) There are a number of autopsy cases were there are QS waves inferiorly without evidence of an MI.
 * 3) There are several reported cases of intermittent LBBB in which the QS waves inferiorly were present only in the aberrantly conducted beats.
 * 4) Conversely, LBBB may mask the development of Q waves in an IMI.

Secondary ST T Wave Changes

 * 1) Primary ST T wave changes are repolarization changes that are seen with ischemia or electrolyte imbalance and reflect actual changes in the myocardial action potentials.
 * 2) Secondary ST T wave changes occur when the sequence of ventricular activation is altered without any disturbance in the electrical properties of the myocardial cells such as is seen in LBBB.
 * 3) As a result of secondary ST T wave changes, the QRS and the T wave vectors are oriented in opposite directions which is known as discordance of the QRS and T wave vectors.
 * 4) Thus, the QRS is often predominantly negative in the right precordial leads while the T wave is oriented positively. In those leads where there is a tall positive R wave there is a negative T wave.
 * 5) These secondary ST T wave changes often mimic infarction, and furthermore they may mask the ST T wave changes of an MI.
 * 6) Sometimes primary ST T wave changes will be superimposed on the LBBB pattern and the following suggests the diagnosis of ischemia or infarction:
 * 7) * ST segment elevation in leads with a predominant R wave. In uncomplicated LBBB, the ST segment is isoelectric or depressed.
 * 8) * T wave inversions in the right to midprecordial leads or in other leads with a predominantly negative QRS. In other words there is an absence of discordance, and there is the presence of concordance.
 * 9) * Morphology: In leads with a predominant R wave, the ST segment begins to slope downwards and blends into the T wave. The ascending limb of the T wave ascends back to the baseline at a more acute angle.
 * 10) * The ischemic T waves have a more symmetric appearance and a slightly upwardly bowed ST segment.
 * 11) * ST T elevations simulating acute infarction: The ST segment can be markedly elevated ( up to 10 mm or more at the J point ) in leads with a QS or rS segment in uncomplicated LBBB. In addition, there can be a loss of R wave progression.
 * 12) * T wave inversions in intermittent LBBB: May develop deep T wave inversions in the right to midprecordial leads of normally conducted beats in the absence of CAD. These T wave inversions are deepest in leads V1 to V4 with a symmetric or coved appearance.

Can You Read a Left Ventricular Free Wall Infarction In the Presence of a LBBB?

 * 1) No. This pattern of infarction results in abnormal q waves in the midprecordial to lateral precordial leads.
 * 2) In LBBB the initial septal depolarization forces are directed from right to left. These leftward septal forces will produce an initial R wave in the midprecordial to the lateral precordial leads, masking the loss of potential q waves produced by the infarction.
 * 3) Therefore left ventricular free wall infarction by itself will not produce diagnostic q waves in the presence of a LBBB.
 * 4) Poor R wave progression is seen in uncomplicated LBBB.

Can You Read a Septal Infarction in the Presence of LBBB?

 * 1) Yes. Again the septal forces are directed to the left in LBBB.
 * 2) If enough of the septum is infarcted to eliminate these initial leftward septal forces, abnormal QR, QRS, or  qrs types of complexes may appear in the midprecordial to lateral precordial leads.
 * 3) These initial q waves may reflect posterior and superior forces from the spared basal portion of the septum.
 * 4) Small q waves of .03 sec or less may be seen in leads I, V5 to V6 in uncomplicated LBBB.
 * 5) The presence of q waves laterally is an example of false localization.