Complete atrioventricular block and intermittent escape rhythm
An escape rhythm in a patient with AV block III is usually regular, with the electrocardiogram showing atrioventricular dissociation and presence of regular ventricular bradycardia with monomorphic QRS complexes. Occasionally, the escape rhythm can be unstable, its activity slowing down or interrupting abruptly, resulting in the occurrence of severe symptoms of varying degree depending on the pause duration and possibly leading to sudden death. This tracing shows the fragile character of the junctional escape rhythm of this patient. When present, the QRS is relatively narrow, the rate is slow but nonetheless ensures correct hemodynamics. When this escape rhythm disappears, a lower-situated ventricular escape focus arises with broad QRS complexes at a slower rate causing the onset of symptoms and suggesting a major risk of sudden death. This patient underwent emergency pacemaker placement.