Serial electrocardiographic evaluation is needed while managing patients with acute coronary syndrome. All changes in ECG need produce variation in symptoms, though symptoms may be most often associated with changes in an ECG recorded during the episode. That is one reason to recommend an ECG during an episode of pain or other important coronary symptom.
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The ECG shown above has an irregular baseline with no regular P waves, indicating atrial fibrillation. rSR’ pattern with T wave inversion is visible in the anterior chest leads. It may be noted that r waves are tiny while the R’ waves are prominent and slurred. The tiny r waves (poor progression of r waves in anterior leads) indicate anterior myocardial infarction as they are equivalent to q waves. Slurred R’ waves indicate the presence of a right ventricular conduction delay in the form of right bundle branch block (RBBB). Symmetric arrowhead inverted T waves also indicate myocardial ischemia. Serial ECG showing resolution of RBBB is seen below:
It may be noted that there are regular P waves preceding each QRS complex, indicating sinus rhythm and the secondary R’ indicating right bundle branch block is absent. Recovery of conduction in the right bundle branch can occur with relief of ischemia in the setting of anterior wall infarction.
In general, presence of RBBB indicates more extensive myocardial damage in AWMI. Those with RBBB along with AWMI, are more likely to have left ventricular dysfunction. Occlusion of proximal septal branch of the left anterior descending coronary artery is associated with RBBB and RBBB is associated with a larger septal scar in AWMI . RBBB has been shown to be a predictor of increased mortality in those myocardial infarction and left ventricular dysfunction . In one study there was a difference between ST elevation myocardial infarction (STEMI) and non ST elevation myocardial infarction (NSTEMI), which found that RBBB was not an independent predictor of mortality in NSTEMI while it was so in STEMI .
A small study suggesting RSR’ complexes as a manifestation of delayed terminal conduction in impaired tissue surrounding a myocardial scar has also been published .
Lewinter C, Torp-Pedersen C, Cleland JG, Køber L. Right and left bundle branch block as predictors of long-term mortality following myocardial infarction. Eur J Heart Fail. 2011 Dec;13(12):1349-54.
Kleemann T, Juenger C, Gitt AK, Schiele R, Schneider S, Senges J, Darius H, Seidl K; MITRA PLUS Study Group. Incidence and clinical impact of right bundle branch block in patients with acute myocardial infarction: ST elevation myocardial infarction versus non-ST elevation myocardial infarction. Am Heart J. 2008 Aug;156(2):256-61.
Varriale P, Chryssos BE. The RSR’ complex not related to right bundle branch block: diagnostic value as a sign of myocardial infarction scar. Am Heart J. 1992 Feb;123(2):369-76.