Increase in internal defibrillation threshold during acute myocardial infarction.

Area of Science:

• Cardiology
• Electrophysiology
• Medical Devices

Background:

• A 67-year-old male with a history of myocardial infarction and ventricular tachycardia (VT) received an implanted cardioverter defibrillator (ICD).
• The patient experienced an acute anteroseptal myocardial infarction.
• VT was inducible, necessitating ICD implantation previously.

Observation:

• During the acute anteroseptal myocardial infarction, the patient had multiple episodes of ventricular fibrillation (VF).
• The implanted cardioverter defibrillator (ICD) delivered maximum internal shocks at 35-J, but these were ineffective in defibrillating the VF.
• Following recovery from the acute infarction, defibrillation testing showed successful VF termination with a 10-J safety margin.

Findings:

• Acute myocardial ischemia significantly and transiently elevated the internal defibrillation threshold.
• The implanted cardioverter defibrillator (ICD) efficacy was compromised during the acute ischemic event.

Implications:

• This case highlights the potential for acute myocardial ischemia to impair the effectiveness of implanted cardioverter defibrillators (ICDs).
• Clinicians should consider the impact of acute ischemia on defibrillation thresholds when managing patients with ICDs.
• Further research is warranted to understand and potentially mitigate the effects of ischemia on defibrillation efficacy.