A type I second degree AV block means that the AV node is only working intermittently to transmit the impulse through to the ventricles. This causes the PR interval to progressively lengthen until there is a P wave without a QRS complex after it, then a pause before it all resets. This is also known as Wenckebach.See also: AV Blocks
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This ECG is from a female in her 60s presented with 2-3 days of fatigue and shortness of breath. She called EMS when her symptoms acutely worsened while she was shopping. EMS arrived and recorded a heart rate of 27. On arrival to the ED she was noted to be in complete heart block. She was given atropine with transient increase in HR to 80s. This ECG was recorded after atropine.
This ECG shows sinus rhythm with second degree type 1 AV block and LBBB. Concordant ST elevation in III and aVF and concordant ST depression in V2. The cause was an occluded proximal right coronary artery. This was missed and the patient died.