Prognostic Implications of Defibrillation Threshold Testing in Patients With Hypertrophic Cardiomyopathy
Pietro Francia1, Carmen Adduci1, Lorenzo Semprini1
1Cardiology, Department of Clinical and Molecular Medicine, St. Andrea Hospital, Sapienza University, Rome, Italy.
Insights
Defibrillation threshold (DFT) testing in hypertrophic cardiomyopathy (HCM) patients is prompted by younger age and massive left ventricular hypertrophy (LVH). However, DFT testing does not predict the efficacy of implantable cardioverter-defibrillator (ICD) shocks for ventricular arrhythmias.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- The necessity and prognostic value of defibrillation threshold (DFT) testing in patients with hypertrophic cardiomyopathy (HCM) undergoing implantable cardioverter-defibrillator (ICD) implantation remain debated.
- Existing research has not explored the predictive implications of DFT testing in this specific patient population.
Purpose of the Study:
- To identify factors influencing the decision to perform DFT testing in HCM patients.
- To assess the efficacy of ICDs through DFT testing in HCM patients.
- To compare DFT values between HCM patients with and without massive left ventricular hypertrophy (LVH).
- To determine if DFT testing predicts the success of ICD shocks for spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF).
Main Methods:
- Retrospective analysis of a cohort of 66 HCM patients implanted with ICDs.
- DFT was tested at the implanting physician's discretion with a 10 J safety margin.
- Patient data, including age, LVH status, DFT results, and ICD interventions, were evaluated during follow-up (median 53 months).
Main Results:
- DFT testing was performed in 38% of patients, with younger age and massive LVH significantly influencing this decision.
- ICDs demonstrated safety and efficacy, with similar DFT safety margins observed in patients with and without massive LVH.
- During follow-up, 15 shocks were delivered for 12 VT/VF events in 7 patients.
- Four unsuccessful shocks occurred, two in patients who underwent DFT testing and two in those who did not; all unsuccessful shocks were at 35 J or lower.
Conclusions:
- Younger age and massive LVH are key factors prompting DFT testing in HCM patients.
- Contemporary ICDs are effective in HCM patients, irrespective of LVH severity.
- DFT testing does not reliably predict the efficacy of ICD shocks for spontaneous VT/VF in this population.
Introduction:
In hypertrophic cardiomyopathy (HCM) patients the need for defibrillation threshold (DFT) testing at the time of ICD implantation is debated. Moreover, its prognostic implications have never been explored. In a cohort of HCM patients we sought to (a) investigate factors prompting DFT testing, (b) evaluate ICD efficacy by testing DFT, (c) compare DFT in patients with and without massive LVH, and (d) assess whether DFT testing predicts shock efficacy for spontaneous VT/VF.
Methods And Results:
We retrospectively analyzed a cohort of HCM patients implanted with an ICD. DFT was tested at the discretion of the implanting physician with a 10 J safety margin. During follow-up, ICD interventions were evaluated. The study population included 66 patients. DFT was determined in 25 (38%) patients. Age (HR: 0.95; 95%CI: 0.92-0.98; P = 0.004) and massive LVH (HR: 6.0; 95%CI: 2.03-18.8; P = 0.001) affected the decision to test DFT. DFT was at least 10 J less than maximal ICD output in 25/25. Safety margin was similar among patients with and without massive LVH (15 ± 3 J vs. 14 ± 2 J; P = 0.42). During follow-up (median 53 months) 15 shocks were delivered for 12 VT/VF in 7 patients. One VF ended spontaneously after a failed shock. Of 4 unsuccessful shocks, 2 occurred in 1 patient with DFT testing and 2 were delivered in 2 patients without. All unsuccessful shocks were ≤35 J.
Conclusion:
Young age and massive LVH prompt DFT testing. Contemporary ICDs are safe and effective in HCM patients independently from the magnitude of LVH. DFT testing does not predict shock efficacy for spontaneous VT/VF.
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