R wave progression (see notes) is the phenomenon where normally, from lead I to lead VI, the pattern is that of a change from the S wave being prominent to the R wave being prominent.
If no R wave develops, this may imply old myocardial death
- this ECG pattern is commonly attributed to a previous anterior myocardial infarction (1)
- a number of other conditions result in a relative decrease in the amplitude of anteriorly directed cardiac electrical forces - poor R wave progression
- for example left bundle branch block, left anterior fascicular block, Wolff-Parkinson-White syndrome, certain types of right ventricular hypertrophy (especially that associated with chronic pulmonary disease), and left ventricular hypertrophy all may result in poor R wave progression
- less common causes of poor Rwave progression include spontaneous pneumothorax, corrected transposition of the great vessels and congenital absence of the pericardium (1)
If the voltages are poor throughout, this can mean dead scar tissue, fluid from a pericardial effusion, myxoedema, or obesity.
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Notes:
- normal R-wave progression in the praecordial leads
- normal chest lead ECG shows an rS-type complex in lead V1 with a steady increase in the relative size of the R-wave toward the left chest and a decrease in the S wave amplitude. Leads V5 and V6 generally show a qR-type complex, with R-wave amplitude in V5 often taller than V6 because of the attenuating effect of the lungs. Normal variations include: narrow QS and rSr patterns in V1 and qRs and R patterns in V5 and V6
- at some point, generally around the V3 or V4 position, the QRS complex changes from predominately negative to predominately positive and the R/S ratio becomes>1. This is known as the transition zone. In some normal individuals, the transition may be seen as early as V2. This is called early transition. At times, transition may be delayed until V4 to V5. This is called delayed transition
- normal R-wave height in V3 is usually greater than 2 mm
- if the height of the r wave in leads V1 to V4 remains extremely small, we say there is "poor R-wave progression" In the literature, definitions of poor R-wave progression have been variable, using criteria such as R-wave less than 2-4 mm in leads V3 or V4 and/or the presence of reversed R-wave progression defined as R in V4 <R in V3 or R in V3 <R in V2 or R in V2 < R in V1, or any combination of these
- poor R wave progression secondary to previous anterior myocardial infarction
- in anterior myocardial infarctions, this produces Q waves in the right and midprecordial leads (V1-V4)
- however, in a significant number of patients the Q waves do not persist
- with previously documented anterior myocardial infarction, the reported estimate of poor Rwave progression on subsequent ECGs varies between 20% and 30%
- average length of time for the complete disappearance of the abnormal Q waves is 1.5 years
- the magnitude of the subsequent leftward forces is less than in patients with poor Rwave progression from other causes
- on the ECG, this results in a diminuation of R-wave amplitude in standard lead I
- up to 85% of patients with old anterior myocardial infarction and poor R-wave progression have either an R-wave in lead I of 4 mm or less or an R-wave in lead V3 of 1.5 mm or less
- absence of these amplitude criteria makes old anterior myocardial infarction unlikely with only a 10%-15% false exclusion of old myocardial infarction
- if poor R-wave progression, additional presence of ST-T wave abnormalities, would provide support for a diagnosis of old anterior myocardial infarction
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