Editing Pacemaker (section)

=== Epicardial pacing ===
{{Main|Epicardial}}
[[File:Pacemaker dependent asystole.jpg|thumb|ECG rhythm strip of a threshold determination in a patient with a temporary (epicardial) ventricular pacemaker. The epicardial pacemaker leads were placed after the patient collapsed during [[aortic valve]] surgery. In the first half of the tracing, pacemaker stimuli at 60 beats per minute result in a wide QRS complex with a [[right bundle branch block]] pattern. Progressively weaker pacing stimuli are administered, which results in [[asystole]] in the second half of the tracing. At the end of the tracing, distortion results from muscle contractions due to a (short) hypoxic [[seizure]]. Because decreased pacemaker stimuli do not result in a ventricular [[escape rhythm]], the patient can be said to be pacemaker-dependent and needs a definitive pacemaker.]]

Temporary epicardial pacing is used during open heart surgery should the surgical procedure create atrio-ventricular block. The electrodes are placed in contact with the outer wall of the ventricle (epicardium) to maintain satisfactory cardiac output until a temporary transvenous electrode has been inserted.<ref>{{cite book |last1=Valchanov |first1=Kamen |last2=Jones |first2=Nicola |last3=Hogue |first3=Charles W. |title=Core Topics in Cardiothoracic Critical Care |date=2018 |publisher=Cambridge University Press |isbn=978-1-108-66567-4 }}{{pn|date=August 2024}}</ref>

Permanent epicardial pacing leads can be implanted surgically and tunneled to the pulse generator pocket. These leads are either passively touching the heart and sewn in place, or have a screw mechanism to actively fix to the heart.