A 75-year-old male suffered an acute myocardial infarction (AMI) while driving his car resulting in a head-on collision with an incoming driver. He suffered multiple rib fractures causing a pneumohemothorax and pericardial tamponade and is he being rushed in the operating room for exploration. In the operating room, you note that the patient has intermittent sinus arrest. The surgeon is placing atrial and ventricular pacing wires and is asking you how you would like to pace the patient now that the surgical portion of the case is over.
Which of the following statements is MOST accurate?
A. VOO is the preferred pacing mode for this patientCorrect Answer: E
VOO and DOO are asynchronous modes that both can cause an R-on-T phenomenon. Although VVI and DDD modes should be safer with regards to R-on-T phenomenon because of ventricular sensing, there have been case reports of R-on-T phenomenon in patients paced in a VVI mode as a result of pacemaker undersensing. Another study reported two other cases of undersensing of demand pacemakers in patients with AMI rendering the patients effectively paced in an asynchronous mode. Given that the patient appears to have an intact atrioventricular conduction system, AAI would be a reasonable pacing mode for this patient at this point. Should the patient develop a higher degree of atrioventricular conduction delay (eg Mobitz II or third-degree AVB), DDD would be a reasonable pacing mode.
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