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ANSWER
This ECG shows a junctional rhythm with a rate of 47 beats/min and an incomplete right bundle branch block (RBBB). The QRS complexes are narrow, indicating conduction originating at or above the atrioventricular (AV) node.
With the absence of a P wave for every QRS complex, the origin of each beat occurs at the level of the AV node, with depolarization of the ventricles via the normal conduction pathway. Intrinsic automaticity of the AV node results in a rate of 40 to 60 beats/min. There may be retrograde conduction from the AV node into the atria; however, it is not apparent in this ECG.
An incomplete RBBB is evidenced by a QRS complex with a duration > 100 ms and ≤ 120 ms with a terminal R wave (eg, rsR’) in lead V1 and a slurred S wave in leads I and V6 (more common with complete RBBB).
The presence of new-onset junctional rhythm with an incomplete RBBB is suspicious for conduction system disease. Given her symptomatic bradycardia, the patient underwent implantation of a dual-chamber permanent pacemaker. She has since returned to her normal activities.
Of note: Careful examination of the baseline in this tracing raises suspicion for atrial fibrillation (AF). However, according to her primary care provider, this patient had had no previous episodes of AF. Intracardiac electrograms taken during her pacemaker implantation ruled out this diagnosis.
ANSWER
This ECG shows a junctional rhythm with a rate of 47 beats/min and an incomplete right bundle branch block (RBBB). The QRS complexes are narrow, indicating conduction originating at or above the atrioventricular (AV) node.
With the absence of a P wave for every QRS complex, the origin of each beat occurs at the level of the AV node, with depolarization of the ventricles via the normal conduction pathway. Intrinsic automaticity of the AV node results in a rate of 40 to 60 beats/min. There may be retrograde conduction from the AV node into the atria; however, it is not apparent in this ECG.
An incomplete RBBB is evidenced by a QRS complex with a duration > 100 ms and ≤ 120 ms with a terminal R wave (eg, rsR’) in lead V1 and a slurred S wave in leads I and V6 (more common with complete RBBB).
The presence of new-onset junctional rhythm with an incomplete RBBB is suspicious for conduction system disease. Given her symptomatic bradycardia, the patient underwent implantation of a dual-chamber permanent pacemaker. She has since returned to her normal activities.
Of note: Careful examination of the baseline in this tracing raises suspicion for atrial fibrillation (AF). However, according to her primary care provider, this patient had had no previous episodes of AF. Intracardiac electrograms taken during her pacemaker implantation ruled out this diagnosis.
ANSWER
This ECG shows a junctional rhythm with a rate of 47 beats/min and an incomplete right bundle branch block (RBBB). The QRS complexes are narrow, indicating conduction originating at or above the atrioventricular (AV) node.
With the absence of a P wave for every QRS complex, the origin of each beat occurs at the level of the AV node, with depolarization of the ventricles via the normal conduction pathway. Intrinsic automaticity of the AV node results in a rate of 40 to 60 beats/min. There may be retrograde conduction from the AV node into the atria; however, it is not apparent in this ECG.
An incomplete RBBB is evidenced by a QRS complex with a duration > 100 ms and ≤ 120 ms with a terminal R wave (eg, rsR’) in lead V1 and a slurred S wave in leads I and V6 (more common with complete RBBB).
The presence of new-onset junctional rhythm with an incomplete RBBB is suspicious for conduction system disease. Given her symptomatic bradycardia, the patient underwent implantation of a dual-chamber permanent pacemaker. She has since returned to her normal activities.
Of note: Careful examination of the baseline in this tracing raises suspicion for atrial fibrillation (AF). However, according to her primary care provider, this patient had had no previous episodes of AF. Intracardiac electrograms taken during her pacemaker implantation ruled out this diagnosis.
Accompanied by her daughter, whom she is visiting from out of town, a 72-year-old woman presents with a two-week history of lethargy. She says she had “the flu” three weeks ago and just can’t seem to recover from it. According to her daughter, she doesn’t appear ill but seems to tire very easily after simple tasks such as walking from her bedroom to the kitchen. The patient denies fever, chills, orthopnea, dyspnea, and cough. There have been no episodes of near-syncope or syncope. She repeatedly states that she is “just so tired.” Prior to the onset of her flulike symptoms, she was very active in her retirement community, dancing, gardening, and going on sponsored trips to a local casino without difficulty. She says she wouldn’t even attempt those activities in her current state, as any activity immediately exhausts her. Medical history is remarkable for hypertension, hypothyroidism, osteoarthritis, and diabetes. Surgical history is remarkable for a cholecystectomy, abdominal hysterectomy, and removal of several lipomas from her upper extremities. Her current medications include aspirin, hydrochlorothiazide, lisinopril, metformin, and levothyroxine. She is allergic to penicillin and sulfa, both of which cause hives and flushing. Social history reveals that she is a retired junior high school librarian, the mother of three living children, and a widow. She is a smoker, with a one-pack-per-day history from age 14 until her husband died four years ago. She quit at that time but has recently started again, smoking half a pack per day (but “only” when she goes to the casino). She does not use alcohol or recreational drugs. The review of systems is positive for corrective lenses and symptoms suggestive of a urinary tract infection. On physical exam, her blood pressure is 138/92 mm Hg; pulse, 50 beats/min; respiratory rate, 16 breaths/min-1; and temperature, 98.4°F. Her weight is 224 lb, and her height is 62 in. She walks with the assistance of a cane and appears tired and apprehensive. Pertinent physical findings include bilateral cataracts, clear lung fields, and a soft, early systolic murmur at the left lower sternal border. She has two well-healed scars on her abdomen and multiple well-healed scars on both upper extremities. Her hands show evidence of osteoarthritis, and she has limited range of motion but no pain in her right hip. The neurologic exam is grossly intact. Laboratory tests and an ECG are performed. The ECG findings include a ventricular rate of 47 beats/min; PR interval, not measured; QRS duration, 120 ms; QT/QTc interval, 454/401 ms; P axis, not measured; R axis, 171°; and T axis, 51°. What is your interpretation of this ECG—and does it provide an explanation for the patient’s recent lethargy?
