Not much to add to Christopher's thorough interpretation. To my eye, all of the conducted sinus beats appear to have normal P-R intervals instead of marginal-to-prolonged P-R intervals. As is, there is probably a greater-than 70% likelihood this is Type II (infraHisian) A-V block. Type I A-V block cannot be ruled out completely. There is a repeating bigeminal pattern of paired beats. The first beat in each pair is right ventricular (RV) paced beat in demand (VVI) mode. The role of the pacemaker is serving as an artificial analogue equivalent to that of a ventricular escape beat. There are dissociated sinus impulses seen at the J-point of the paced beats. I would not infer a 2:1 ratio since it is unknown if the dissociated sinus impulse would (or could) have conducted if not for the paced beat interfering and obstructing it's descending journey to the ventricles. In the absence of any pacing, it's possible this could be a 3:1 high-grade (advanced) A-V block. The pacemaker would have to temporarily be inhibited in order to test the degree of block and intrinsic conduction. The second beat in each pair is a conducted (capture) beat with LBBB. This is just one of many different manifestations of "escape-capture bigeminy". If anyone has a copy of the book, Dr. Marriott has a somewhat similar example of "escape-capture bigeminy" on page 406 of Practical Electrocardiography, 8th ed. 1988. His example also features a pacemaker.
Rate: atrial rate of ~90, effective vent rate of 60 bpm.
ReplyDeleteRegularity: regular irregularities
P-waves: presumed sinus, dropped QRS, backup V-pacing present
PRi: ~200-220ms, borderline prolonged
QRSd: wide and wide-wide, V1-negative LBBB and RV pacing present
Rhythm: normal sinus with 2AVB Type II 2:1 w/ backup V-pacing @ a failsafe of 60 bpm.
Axis: -30 deg in normal conduction, v-pace w/ RV pacing.
ST/T-waves: relatively unremarkable for the rhythm
Diagnosis: suspected 2AVB Type II w/ NSR and failsafe pacing at 60 bpm.
This comment has been removed by the author.
ReplyDeleteNot much to add to Christopher's thorough interpretation. To my eye, all of the conducted sinus beats appear to have normal P-R intervals instead of marginal-to-prolonged P-R intervals. As is, there is probably a greater-than 70% likelihood this is Type II (infraHisian) A-V block. Type I A-V block cannot be ruled out completely. There is a repeating bigeminal pattern of paired beats. The first beat in each pair is right ventricular (RV) paced beat in demand (VVI) mode. The role of the pacemaker is serving as an artificial analogue equivalent to that of a ventricular escape beat. There are dissociated sinus impulses seen at the J-point of the paced beats. I would not infer a 2:1 ratio since it is unknown if the dissociated sinus impulse would (or could) have conducted if not for the paced beat interfering and obstructing it's descending journey to the ventricles. In the absence of any pacing, it's possible this could be a 3:1 high-grade (advanced) A-V block. The pacemaker would have to temporarily be inhibited in order to test the degree of block and intrinsic conduction. The second beat in each pair is a conducted (capture) beat with LBBB. This is just one of many different manifestations of "escape-capture bigeminy". If anyone has a copy of the book, Dr. Marriott has a somewhat similar example of "escape-capture bigeminy" on page 406 of Practical Electrocardiography, 8th ed. 1988. His example also features a pacemaker.
ReplyDeleteI'm still working through a book on pacemakers as my knowledge of their activity is woefully inadequate.
ReplyDeleteI'd wondered how I could tell if this were DDD vs VVI (or if you even CAN tell from just a tracing like this)?