Figure 35-7 Improper placement of a transesophageal pacemaker. The top recording is electrocardiographic (ECG) lead II, the middle recording is ECG lead III, and the bottom recording is the invasive arterial pressure waveform. This 72-year-old man developed a sinus bradycardia with evidence of tissue underperfusion. A transesophageal pacemaker was placed, and the large electrocardiographic artifacts at 75 beats/min were misinterpreted as ventricular systoles (i.e., capture). They were the pacing stimuli as represented on the ECG monitor. This patient has a sinus rate of 50 beats/min with a first-degree atrioventricular block (PR interval of 280 msec). The patient's native atrial (P) and ventricular (R) depolarizations are identified. The arterial pressure waveform confirms pacing noncapture.