Cardiac Arrhythmias After Coronary Artery Bypass Graft Surgery

Scenario: A 73-year-old man was transferred from the cardiac intensive care unit to the cardiac progressive care unit 2 days after coronary artery bypass graft (CABG) surgery. His medical history included hypertension, prediabetes, and a cerebrovascular accident, which resulted in minimal residual pain in his left arm. On arrival at the cardiac progressive care unit, his vital signs were stable: body temperature, 98.2 °F (36.8 °C); blood pressure, 107/63 mm Hg; pulse rate, 69 beats per minute in normal sinus rhythm; oxygen saturation as measured by pulse oximetry (Spo2), 98% on room air; and respiratory rate, 18 breaths per minute. Four hours after he arrived at the cardiac progressive care unit, the telemetry alarm sounded and the 2-lead (II and V1) electrocardiographic (ECG) rhythm strip shown here printed automatically.Paroxysmal atrial fibrillation (AF) (beats 1 and 2) versus supraventricular tachycardia (beats 3–8) with a 2-second pause followed by sinus bradycardia. Overall, the rhythm is suggestive of tachybrady syndrome.Arrhythmias are relatively prevalent, occurring in 15% to 45% of patients after CABG. The post-CABG arrhythmias encountered most often are of supraventricular origin, including paroxysmal AF and atrial flutter. In the 2-lead telemetry strip shown here, paroxysmal AF is visible based on the initial irregularity of the rhythm and the fine fibrillatory waves in the first 3 beats. After the paroxysmal AF, a more regular rhythm consistent with supraventricular tachycardia (SVT) is apparent, followed by a 2-second pause and then the start of sinus bradycardia. This rapid shift in both rhythm (eg, paroxysmal AF/SVT to pause to sinus bradycardia) and rate (eg, from 110 beats per minute to 50 beats per minute) is a characteristic presentation of tachybrady syndrome. Tachybrady syndrome is a condition marked by the alternation between intermittent supraventricular arrhythmias, most notably paroxysmal AF, and bradycardia. The stark transition from paroxysmal AF/SVT to a pause and subsequently sinus bradycardia underscores the dynamic nature of this cardiac rhythm and the critical importance of vigilant ECG monitoring of post-CABG patients.Since nurses are responsible for bedside monitoring, they should be well-versed in the causes of and risk factors for post-CABG arrhythmias such as paroxysmal AF and SVT. Paroxysmal AF and/or SVT after CABG result from various factors, such as adrenergic stimulation, systemic inflammation, electrolyte imbalances, or autonomic activation during or after surgery, often due to conditions like pain, hypotension, or infection. Patients at greater risk for post-CABG paroxysmal AF/SVT include those with advanced age, a history of AF, an enlarged left atrium, obesity, and chronic obstructive pulmonary disease. Most patients with post-CABG paroxysmal AF/SVT are asymptomatic, meaning bedside monitoring is most likely the only way to identify this complication. Post-CABG paroxysmal AF/SVT is typically noticed within the first few days after surgery and resolves on its own.Upon recognizing a post-CABG patient experiencing paroxysmal AF/SVT, the nurse should assess the patient for symptoms (eg, palpitations, fluttering, dyspnea, numbness, tingling), record vital signs, obtain a 12-lead ECG, and promptly notify a provider. Episodes of AF/SVT may be very brief and paroxysmal, as in this example, so the nurse may need to monitor overall "AF burden" (ie, proportion of time in AF during a monitoring period) per unit policy. In general, greater AF burden is indicative of greater risk for hemodynamic instability and acute stroke, and it may prompt the provider to initiate anticoagulation therapy. Underlying causes of paroxysmal AF such as electrolyte imbalances should be explored. In this case, the post-CABG patient was asympomatic and the nurse identified the paroxysmal AF on the bedside telemetry rhythm strip. The patient continued to have these short episodes characteristic of tachybrady syndrome for 28 hours. The overall AF burden was low (1%), so anticoagulation therapy was not initiated. The patient returned to a stable sinus rhythm before discharge.