The Effects of Shock from Defibrillation Threshold Testing on Cardiac Systolic and Diastolic Function

Area of Science:

• Cardiology
• Electrophysiology
• Medical Devices

Background:

• Inappropriate implantable cardioverter defibrillator (ICD) shocks are linked to increased mortality.
• The direct impact of defibrillation threshold (DFT) testing shocks on cardiac function remains under investigation.

Purpose of the Study:

• To evaluate the immediate effects of DFT testing shocks on left ventricular (LV) systolic and diastolic function.
• To assess changes in hemodynamic parameters following DFT testing in patients undergoing ICD implantation or generator exchange.

Main Methods:

• DFT testing was conducted in 34 patients receiving ICD or cardiac resynchronization therapy with a defibrillator.
• Cardiac function was assessed using a Mikro-Cath™ diagnostic pressure catheter, measuring parameters like LV systolic and end-diastolic pressure, peak positive and negative dp/dt, and the tau index.
• Hemodynamic parameters were recorded before and at multiple intervals (1, 3, 5, 10, 15 minutes) after DFT testing.

Main Results:

• Peak positive dp/dt significantly increased post-DFT testing compared to baseline (P < 0.01).
• Peak negative dp/dt and the tau index significantly decreased post-DFT testing compared to baseline (P < 0.01 for dp/dt, P < 0.05 for tau index).
• These changes indicate an immediate improvement in both systolic and diastolic function.

Conclusions:

• Shocks delivered during DFT testing led to immediate improvements in LV systolic and diastolic function.
• The positive effects were more pronounced in patients with preserved LV ejection fraction.
• DFT testing may have a transient beneficial effect on cardiac function.