R wave progression in the precordial leads:
The normal R wave height increases from V1-5. The normal R wave height in V5 is always taller than that in V6, because of the attenuating effect of the lungs. The normal R wave height in lead V3 is usually >2 mm.

"Poor R wave progression":
A non-preferred term, according to the AHA criteria for terminology. The term "poor wave progression" (PRWP) is itself a poor one, because most people use this term to imply the presence of an anterior MI, when it may not be present. One should exclude the following causes of either small R waves in the right precordium or a late QRS transition before diagnosing MI.

Reversed R wave progression (RRWP):
Reversed R wave progression is defined as a loss of R wave height between leads V I and V2 or between leads V2 and V3 or between leads V3 and V4. In the absence of LVH, this finding suggests anterior MI or precordial lead reversal (see next page).

Causes of small R waves in the right precordial leads:

1. LVH
2. LAFB
3. LBBB
4. Cor pulmonale (with the type C loop of RVH) or COPD

Tall R waves in the right precordial leads:
A common problem in electrocardiography is the presence of tall R waves in the right precordial leads, usually V1 and sometimes V2, or an R/S ratio > 1 in lead V1. Causes include the following:

1. RVH (the most common cause):
   There is an R/S ratio > 1 or an R wave height > 7 mm tall in lead V1.
2. Posterior MI:
   There is an R wave > 6 mm in lead V1 or > 15 mm in lead V2.
3. Right bundle branch block:
   The QRS duration is prolonged and typical waveforms are present (see above).
4. The WPW pattern:
   Left-sided accessory pathway locations produce prominent R waves with an R/S ratio > 1 in V1.
5. Rare or uncommon causes:
   • The normal variant pattern of early precordial QRS transition. (not uncommon) Diagnosis is usually made on clinical grounds.
   • The reciprocal effect of deep a Q wave in leads V5-6 (very rare)
   • Duchenne's muscular dystrophy (very rare)
   • Chronic constrictive pericarditis (very rare).
   • Reversal of the right precordial leads: In this case, lead V1 may really be lead V3. The key is in the P wave. Lead V1 always has the most negative net area of all P waves in the precordial leads. If this sign is found in lead V3, there is lead reversal.

In mirror-image dextrocardia, standard lead V1 may really be lead V2 if right anterior precordial leads are recorded, with an attendant relatively tall R wave. In this case, the alerting sign is in lead I. The QRS is negative, with an inverted P wave and T wave. In the precordial leads there is an abnormal QRS progression and an abnormal R/S ratio < 1 in V6.

How to distinguish the tall R wave of RVH from the tall R wave of posterior MI in lead V1:
In the "type A loop" of RVH (producing tall R waves in V1), there is an obligatory repolarization abnormality producing a downsloaine ST segment and an, inverted T wave. In these patients, there is usually right axis deviation, In contrast, when tall R waves in V 1 are produced by a fully evolved posterior MI, there is usually an upright. commonly tall T wave. Because posterior MI is usually associated with concomitant inferior MI, there should be left axis deviation, if any deviation exists.

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