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    Hypotension and Near-syncope in a 66-year-old Woman

     

    Answer: Pacemaker-mediated tachycardia

    Antibiotic treatment was initiated for possible urosepsis despite the lack of fever and leukocytosis. Although there was no clear evidence of dehydration, IV fluids were administered because of the hypotension, history of vomiting, and possible sepsis. When the patient’s blood pressure remained unchanged, pacemaker interrogation was expedited for possible pacemaker-mediated tachycardia (PMT), which turned out to be the correct diagnosis. The unit was reprogrammed, and all vital signs immediately normalized.

    A second ECG is shown below.



    Discussion

    Pacemaker-mediated tachycardia (PMT) is rare, especially with modern pacemakers, in which a perpetual activation loop occurs between the atrial and ventricular leads. The ventricular rate is typically under 130 beats/min, which represents the upper programmed set rate limit of the pacemaker. Nevertheless, hemodynamic compromise, namely hypotension, may still occur. As in this case, PMT is often not considered until other, more common conditions have been ruled out and no other explanation seems plausible.

    Symptoms typically include generalized weakness and syncope or near-syncope. Palpitations and chest pain may occur. Blood pressure is often low, and the pulse is typically between 110 and 130 beats/min. Neither hypotension nor tachycardia is usually responsive to fluids in patients with PMT, which is one clue to the diagnosis.

    Once the diagnosis of PMT is suspected, a cardiologist should be consulted and a representative from the pacemaker company called to interrogate the pacer. Pacer interrogation can confirm the diagnosis and can be followed by pacer reprogramming to terminate the tachycardia. If the patient is unstable, application of a magnet to the pacemaker should break PMT by switching to a non-synchronous present rate (usually between 60 and 100 beats/min). If a magnet is not available, atrioventricular nodal blockers can be tried, but caution should be used if the diagnosis is uncertain because in other conditions they may worsen hypotension.

    For more information on PMT, see the chart below.

    Excerpt on PACEMAKER MEDIATED TACHYCARDIA (PMT) The Emergency Medicine 1-minute Consult Quick Essentials pocketbook


     

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