Dysrhythmias, Conduction Defects and Cardioversion

Symptomatic Bradycardia and Emergency Pacing

In the critical care unit, symptomatic bradycardia is recognized when an abnormally low heart rate directly impairs systemic perfusion. Rather than relying on a numerical rate alone, the bedside nurse evaluates the patient for clear signs of inadequate organ perfusion. These clinical manifestations include systemic hypotension, acute alterations in mental status, ischemic chest pain, and the sudden emergence of acute pulmonary edema. Recognizing these signs requires rapid synthesis of bedside data to prevent imminent cardiovascular collapse.

When an adult presents with symptomatic bradycardia and poor perfusion, initial pharmacologic management under an ACLS protocol or provider order begins with atropine 1 mg administered by rapid intravenous push. This dose may be repeated every 3 to 5 minutes as needed, reaching a maximum total dose of 3 mg. However, critical care nurses must anticipate clinical limitations: atropine is generally ineffective when conduction failure originates within the sub-nodal His-Purkinje system, which characterizes high-grade atrioventricular blocks like Mobitz Type II or third-degree atrioventricular block accompanied by a wide QRS complex.

For patients with high-grade conduction blocks or bradycardia refractory to atropine, transcutaneous pacing serves as the primary emergency non-pharmacologic intervention. Under an ACLS protocol or provider order, transcutaneous pacing can be instituted immediately, alongside continuous infusions of dopamine or epinephrine. These vasoactive infusions are carefully titrated to ordered hemodynamic goals while the nurse frequently reassesses patient perfusion. Continuous intra-arterial blood pressure monitoring, when available, provides real-time beat-to-beat hemodynamic assessment during infusion titration and concurrent dysrhythmia management.

Verifying effective transcutaneous pacing requires confirming both electrical and mechanical capture. Electrical capture is observed on the cardiac monitor by a distinct pacing spike followed immediately by a wide QRS complex and a broad T wave. Mechanical capture must be verified independently; the nurse palpates a central pulse, preferably the femoral pulse, ensuring that each pulsed beat corresponds directly to an electrically paced QRS complex. An indwelling arterial pressure line waveform provides valuable additional confirmation of true mechanical ventricular output.