Introduction Defibrillation Threshold Testing (DFT) testing is a lengthy, potentially painful, and a hazardous process. Little information is available concerning the identification of patients with high DFT who undergo ICD implantation with transvenous leads. Patients with predicted low DFTs may be eligible for abbreviated ICD testing but high-risk patients who require multiple shocks may require general anesthesia for patient comfort. Some suggested clinical characteristics that identify high DFT other than prior amiodarone use preoperatively. These include NYHA Class III, IV, low ejection fraction, no previous history of bypass surgery, and presenting with ventricular fibrillation. However, no specific recommendations have ever been suggested for DFT testing in patients having one or more high DFT predictors.Aim of the Study: The aim of our study is to search for clinical predictors for defibrillation thresholds (DFTs) of implantable-cardioverter defibrillators (ICDs) in order to suggest the most suitable protocol for intraopertaive testing for DFTs to reduce episodes of VF induction and subsequently reducing the number of shocks in the procedure, if possible.Methods: Our study group comprised 50 consecutive patients who received ICDs for primary or secondary prevention of sudden cardiac arrest who were recruited in the period between January 2006 and December 2008 in St Thomas Hospital, University of London, London, UK, University of Maryland Medical Center, University of California San Diego Hospital, and St Vincent Mercy Medical Center, Toledo, Ohio. The study group mean age was 59 ± 13 year. The 50 patients included 31male and 19 female. Thirty patients (60%) had hypertension, and 13 (26%) had diabetes MellitusResults: According to the measured DFT, the study group was subdivided into two groups; group I (n=42, 84%) with normal DFT defined as DFT <20J and group II (n=8, 16%) with high DFT defined as DFT ≥ 20J. The continuous clinical variables which were used for comparison between groups I and II included: age, body Surface Area (BSA), Body Mass Index (BMI), QRS complex duration, Left Ventricular Ejection Fraction (LVEF), R wave amplitude, RV Pacing threshold and Pace/sense lead impedance. Despite the trend of increase in DFT with the increase of age, there was no significant correlation between the two variables. Comparison between the two groups in terms of sex with more males in the high DFT group compared to lower DFT group. Also, patients in group II, with higher DFT, were more likely to have the diagnosis of dilated cardiomyopathy, have lower LVEF and were likely to receive 3 or more shocks during DFT testing. Multivariate regression analysis was conducted for the study group utilizing DFT as the dependent variable. Both pacing threshold and LVEF were found to correlate with DFT. It was found that pacing threshold had a negative correlation with DFT.Conclusion: Our study demonstrated that the clinical variables of male sex, presence of non-ischemic cardiomyopathy, and higher degree of myocardial dysfunction reflected by lower LVEF and higher pacing thresholds may predict the group of patients who have higher DFT.