Supraventricular Tachycardia After Open-Heart Surgery

Authors: Ash, A., DO, Calise, A.G., DO
St. Michael's Medical Center,
Department of Emergency Medicine, Newark, NJ

HISTORY: A 33-year-old male was brought by ambulance to the Emergency Department complaining of palpitations that began approximately one hour prior to presentation. He was discharged one day prior to presentation from another institution after having an aortic valve replacement as the result of a bicuspid aortic valve. He also complained of shortness of breath and dizziness. Physical exam was significant for an anxious appearing tachypneic male with a heart rate of 229 beats per minute.

ER/HOSPITAL Course: The patient was placed on a monitor and an EKG showing a narrow complex tachycardia at a rate of 229 beats per minute was obtained. Adenosine, 6mg IV, was given and failed to convert the rhythm. 12mg was then given twice, and again failed. Lopressor, 5mg IV, was then administered at which time the patient's blood pressure dropped into the 70's. Synchronized cardioversion at 50J was attempted and the patient became apenic and pulseless and deteroriated into v-fib arrest. He was defibrilated 3 times, intubated, and given 1mg of epinephrine IV, at which time his pulse returned and his monitor showed sinus tachycardia. Laboratory blood work was significant for a troponin of .57 and a BNP of 446. The patient was admitted to the intensive care unit, and a 2D echo was performed and showed a normal ejection fraction with mild left ventricular hypertrophy. There was no aortic stenosis or insufficiency. The cardiologist interpreted the EKG as atrial flutter with one-to-one conduction, and the patient went for electrophysiologic studies, which showed inducible, typical, counter-clockwise atrial flutter. Radiofrequency ablation was then performed, and the patient was eventually discharged on Toprol-XL.

DISCUSSION: Post-operative atrial tachycardia is a common phenomenon in patients who have undergone open-heart surgery. It is estimated that 40% of patients develop an atrial tachydysrhytmia in the recovery period following coronary artery bypass grafting. This figure is even higher (50%) for patients who have a valve repair. Although the majority of arrhythmias occur 2-3 days following surgery, they can occur at any time during the recovery period. Because of this, it is crucial that the emergency physician be aware of the pitfalls involved in treating such patients. Thromboembolic events are extremely common in post-open heart surgery patients. Stroke, for example, occurs in up to 6% of patients after CABG. One of the risk factors for such an event is atrial tachycardia. This is significant because, in the absence of atrial fibrillation or atrial flutter, the young patient with atrial tachycardia does not routinely receive anticoagulation. In the post-operative patient, however, anticoagulation is of critical importance, regardless of the atrial rhythm. Additionally, the use of adenosine in the setting of supraventricular tachycardia that is not likely to be terminated by this medication is potentially hazardous. Brodsky et. al. report a case of accelerated atrioventricular conduction during atrial flutter after administration of adenosine, and there has also been a case report of Torasades induced by adenosine in a patient with prolonged- QT syndrome masked by an underlying tachycardia. In light of this, adenosine should be avoided in this group of patients, unless the diagnosis of re-entry SVT likely to be terminated by the drug is certain.
In patients with post-operative SVT, anticoagulation is essential to prevent thromboembolic events. Additionally, it is probably safer and more effective to attempt to convert these patients with drugs other than adenosine.