Meta-analysis shows no impact on mortality for defibrillation threshold testing in ICD patients

                                         

DFT is undertaken at the time of ICD implantation to establish the amount of energy needed to terminate ventricular fibrillation. Based on two large surveys from Italy and Canada, use of DFT varies widely in clinical practice, ranging from 33% to 68% of implantations. Management of DFT has not been mentioned in any guidelines. “Since existing studies evaluating the benefits of DFT haven’t demonstrated definitive results we decided to perform a meta-analysis evaluating the efficacy of DFT compared to no DFT at the time of ICD implantation,” said Stavros Stavrakis, the first author of the study, from the Heart Rhythm Institute at the University of Oklahoma Health Sciences Center, Oklahoma.

In the study, Stavrakis and colleagues identified eight studies from the MEDLINE and EMBASE databases, involving 5,020 patients that evaluated the effect of DFT testing versus no DFT testing at the time of defibrillator implantation. Altogether 3,068 patients underwent DFT and 1,952 did not. It is of note, said the authors, that only one of the studies was randomised, and included a small number of patients. Reasons for not performing DFT included patient characteristics (four studies), the centre’s standard practices (three studies), and being randomised to the arm without treatment (one study).

Results show that based on the pooled estimate across the studies, DFT testing versus no DFT testing did not reduce total mortality (RR=0.94, 95% CI 0.74-1.21; p=0.65) or ventricular arrhythmias
(RR =1.19, 95% CI 0.85-1.68, p=0.30).

“From this we concluded that DFT testing didn’t reduce total mortality or ventricular arrhythmias at a median follow-up of 24 months, bringing into question whether there are any benefits to routinely performing this procedure,” said Stavrakis.

In addition to the cost, he added, it needed to be considered that DFT testing is not without adverse effects. “Repeated inductions of ventricular fibrillation and subsequent shocks might lead to significant decreases in blood pressure, compromised heart function, or even in rare cases, result in death.” That being said, he added, there are still some patients that would still require DFT testing, such as those with right-sided implants, or those who are morbidly obese.

Given the non-randomised nature of most of the studies, he said, there is now a need for further large multicentre randomised controlled trials adequately powered to detect clinical outcomes. “This would be needed to provide sufficient evidence to change clinical practice regarding DFT testing,” said Stavrakis.