Second Degree Heart Block Type I - EKG Reference Caliper Time Interval: ___ seconds Key Features RhythmIrregular but with progressively longer PR interval lengthening RateThe underlying rate P WaveNormal PR IntervalProgressively longer until a QRS complex is missed, then cycle repeats QRSNormal (0.06-0.10 sec) Notes Second Degree Heart Block Type I EKG Reference Quick Links Sinus Atrial Junctional Ventricular Atrioventricular Pacemaker All