This is the case report of a 71-year-old polymorbid patient who overcame diaphragmatic myocardial infarction after surgical revascularization and with reimplanted pacemaker in DDDM (2007) regime. The patient was admitted to the hospital for persistent atypical ventricular flutter and progression of heart failure. The patient underwent, according to guidelines, unsuccessful medicamentous version. Synchronized biphasic electrical cardioversion was indicated and carried out with transient loss of ventricular stimulation and with persistent atrial stimulation. Control examinations of stimulation parameters prior to as well as after ECV did not reveal any pathological values.