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ANSWER
Findings on this ECG include sinus rhythm at a rate of 60 beats/min, evidence of a second-degree atrioventricular (AV) block (Mobitz I), and a right bundle branch block (RBBB).
To understand the rhythm, it is best to focus on the rhythm strip, particularly lead I at the bottom of the ECG. If you measure the P-to-P interval, you will notice that it is consistent and constant at a rate of 60 beats/min, regardless of the QRS complex. If you look at the PR interval from the second to the sixth QRS complex, you will notice that it is regular until the QRS is dropped after the P wave that follows the sixth QRS complex. Following the pause, the PR interval on the seventh, eighth, and ninth QRS complexes gradually prolongs. Although this is not a classic example of Mobitz I block, it is indicative of an AV node with a conduction abnormality.
Subsequent rhythm strips documented multiple blocked PR intervals that corresponded to the patient’s dizziness. The RBBB is evident by the RSR’ pattern seen in lead V1 with a QRS duration ≥ 120 ms.
ANSWER
Findings on this ECG include sinus rhythm at a rate of 60 beats/min, evidence of a second-degree atrioventricular (AV) block (Mobitz I), and a right bundle branch block (RBBB).
To understand the rhythm, it is best to focus on the rhythm strip, particularly lead I at the bottom of the ECG. If you measure the P-to-P interval, you will notice that it is consistent and constant at a rate of 60 beats/min, regardless of the QRS complex. If you look at the PR interval from the second to the sixth QRS complex, you will notice that it is regular until the QRS is dropped after the P wave that follows the sixth QRS complex. Following the pause, the PR interval on the seventh, eighth, and ninth QRS complexes gradually prolongs. Although this is not a classic example of Mobitz I block, it is indicative of an AV node with a conduction abnormality.
Subsequent rhythm strips documented multiple blocked PR intervals that corresponded to the patient’s dizziness. The RBBB is evident by the RSR’ pattern seen in lead V1 with a QRS duration ≥ 120 ms.
ANSWER
Findings on this ECG include sinus rhythm at a rate of 60 beats/min, evidence of a second-degree atrioventricular (AV) block (Mobitz I), and a right bundle branch block (RBBB).
To understand the rhythm, it is best to focus on the rhythm strip, particularly lead I at the bottom of the ECG. If you measure the P-to-P interval, you will notice that it is consistent and constant at a rate of 60 beats/min, regardless of the QRS complex. If you look at the PR interval from the second to the sixth QRS complex, you will notice that it is regular until the QRS is dropped after the P wave that follows the sixth QRS complex. Following the pause, the PR interval on the seventh, eighth, and ninth QRS complexes gradually prolongs. Although this is not a classic example of Mobitz I block, it is indicative of an AV node with a conduction abnormality.
Subsequent rhythm strips documented multiple blocked PR intervals that corresponded to the patient’s dizziness. The RBBB is evident by the RSR’ pattern seen in lead V1 with a QRS duration ≥ 120 ms.
A 74-year-old man lives alone in his home and cares for a large garden of which he is very proud. Recently, his granddaughter noticed that the garden had not been tended to. When asked, her grandfather told her he had been too tired to take care of it. Further questioning revealed that he had experienced frequent dizzy spells and had passed out in his garden about two weeks ago. Since then, he has been reluctant to go outside. Concerned, his granddaughter brings him to your urgent care clinic for evaluation. During the history, you learn that the patient has not seen a clinician in more than 10 years because he “doesn’t like to be a bother.” He has a long-standing diagnosis of hypertension that is untreated because he doesn’t like to take pills. Eliciting information is difficult, but his granddaughter reports that he had a cholecystectomy in the distant past; she cannot recall any other problems. The patient currently takes no medications; he is allergic to penicillin, which produces a true anaphylactic response. He has a remote history of smoking, but he stopped after his wife died of lung cancer 12 years ago. He drinks two or three cans of beer per week and does not use recreational drugs or herbal medicines. He had one son, who died in an automobile accident five years ago; his daughter-in-law visits infrequently and his granddaughter frequently. He has no living siblings. Review of systems is remarkable for knee and hip pain and stiffness from osteoarthritis, as well as occasional constipation. He denies palpitations, irregular or rapid heartbeats, shortness of breath, and lower extremity swelling. Aside from his dizzy spells, he claims to be “healthy as a horse.” Physical exam reveals a blood pressure of 192/102 mm Hg; pulse, 60 beats/min and irregular; respiratory rate, 18 breaths/min; and temperature, 98.1°F. His height is 66 in and his weight, 164 lb. The patient wears corrective lenses, and arcus senilis is present. There are multiple teeth missing, but those that remain are in good repair. There is no thyromegaly, and a soft bruit is present over the left carotid artery. The patient is somewhat barrel chested, and all breath sounds are clear. There is a harsh, early systolic murmur best heard at the left upper sternal border and no extra heart sounds or rubs. The abdomen is scaphoid and soft, and surprisingly, despite the history of a cholecystectomy, there is no abdominal scar. The extremities are consistent with signs of longstanding osteoarthritis. Peripheral pulses are strong bilaterally, and the neurologic exam is grossly intact. You order a chemistry panel, complete blood count, thyroid function studies, liver function studies, and an ECG. While the laboratory data are still pending, you receive the results of the ECG, which show a ventricular rate of 56 beats/min; PR interval, not measurable; QRS duration, 144 ms; QT/QTc interval, 438/422 ms; P axis, 47°; R axis, –24°; and T axis, 55°. What is your interpretation of this ECG—and have you found a reason for his dizziness?
