This trial included patients who met the ICD criteria for
This trial included 1500 patients, who met the ICD criteria for primary prevention (non-ischemic, ischemic, dual chamber ICD or CRT-D). The patients were randomized to 3 arms: (1) conventional therapy: Zone 1(VT) 170bpm, 2.5s delay, Zone 2 (VF) 200bpm, 1s delay; (2) high rate therapy: Zone 1(VT) 170bpm, monitor only, Zone 2 (VF) 200bpm, 2.5s delay; (3) long delay therapy: Zone 1(VT) 170bpm, 60s delay, Zone 2 (VT) 200bpm, 12s delay, Zone 3 250bpm, 2.5s delay. Primary outcomes were assessed as the first occurrence of inappropriate therapy (ATPs or shocks), The secondary end points were assessed as death from any cause and the first episode of syncope.
The MADIT-RIT study enrolled only primary-prevention patients. An earlier study, PainFREE Rx II, explored the over-all rates of inappropriate therapy in both primary and secondary prevention patients . Both groups had a 15% rate of inappropriate therapy, but these were slightly more common in primary-prevention patients. Of all the arrhythmic events detected and treated by the ICD, 46% led to inappropriate therapy in primary-prevention patients compared to 34% in secondary-prevention patients. With secondary-prevention patients, clinicians have arrhythmic history to help guide programming decisions.
The MADIT-RIT study found that high-rate and delayed-therapy were both effective in reducing inappropriate shock and mortality compared to conventional therapy. Since they are both effective, the simpler one should take precedence. Programming a cutoff rate of 200bpm is very straightforward (and much easier to program than delayed therapy) and MADIT-RIT found it reduced both inappropriate therapy and mortality rates. Program a high VF cutoff (for example, 200bpm) and delay the onset of the therapy — MADIT-RIT shows that this saves lives.
Future direction Although “MADIT” studies have proven benefits from ICDs, no randomized controlled have been created for the certain patient subgroups. It remains unclear whether all patients with similar profiles (to inclusion criteria) in cohorts would gain similar benefit from ICDs. In addition, results from previous studies for risk stratification have not been consistent, and could not be applicable reliably to general glut 1 or to ICD candidates. Some questions, which remain unanswered with “MADIT” studies, were whether the patients with advanced heart failure and narrow QRS complex, do they benefit from biventricular pacing? Two prospectively designed, yet moderately large, studies in patients with advanced HF and normal QRS complex have been completed, the ReThinQ  and ESTEEM-CRT  trials; both studies missed the primary end-point and turned out to be negative. What about patients with moderate LV dysfunction and need for RV pacing? HOBIPACE  and PAVE  studies show that patients with preexisting mild to moderate left ventricular dysfunction and an indication for standard pacing have improved left ventricular systolic function, exercise capacity, and quality of life after biventricular pacing compared with right ventricular apical pacing. These results suggest that biventricular pacing may be a feasible option for permanent pacing in the majority of patients who have normal left ventricular systolic function and that it may attenuate the adverse effects of conventional right ventricular apical pacing on left ventricular systolic function. This hypothesis has been recently tested in the PACE trial . The study was a double-blinded, multicenter study, in which 177 patients were assigned to either biventricular pacing (89 patients) or right ventricular apical pacing (88 patients). The PACE study showed that mean LVEF declined by almost 7 percentage points (from 61.5±6.6 to 54.8±9.1) in the first year of right ventricular apical pacing in patients with a normal ejection fraction. There are several limitations of this study: the sample was small, and the study was not powered to detect significant differences in clinical events. The increased cost and complications associated with biventricular pacemakers are potential concerns. Randomized trials with longer follow-up periods, larger samples, and sufficient power to evaluate clinical outcomes between these two pacing strategies are warranted. Even though, the cost of ICDs has come down, financial restrain has not yet been resolved in the new healthcare reform. These questions would be important challenges and would probably be answered in the future trial with the least cost and the most survival implication in the clinical practice.