Discussion
In the European Guidelines, ICD implantation is a class 1B recommendation for patients with nonischemic heart failure, and a class 1A recommendation for patients with ischemic heart failure.[7] However, no difference was found between the long-term benefits of DCM patients and ICM patients receiving ICD as primary prevention treatment in this study.
Patients with extensive comorbidity may experience less benefit from ICDs than those with less comorbidity.[10] We can see that patients in the ICM group have prevalence of hypertension and diabetes than patients in the DCM group. In this study, 38% of deaths were attributed to non-cardiovascular diseases, emphasizing the importance of strict screening criteria for ICD implantation. ICD implantation in NICM patients had a less benefit, which provided a basis for not implanting ICD in frail patients, which is in line with the guidelines that recommend.[11, 12]
Cox regression analysis found that all-cause mortality of ICM was higher than that of DCM group. Patients with more comorbidities benefited less from ICD treatment. Therefore, it is not recommended to install ICDs in patients who cannot tolerate or are not suitable for CRT treatment, VAD (ventricular assist device), NYHA Class IV heart transplantation, or patients with severe comorbidities. The life expectancy of these patients is difficult to exceed One year, it is difficult to obtain benefits from expensive ICD treatment. Studies have also shown that ICM patients in NYHA II-III patients have a greater risk of death than NICM patients, so it is more recommended to carry out drug or ICD primary prevention treatment in the early stage of the disease.[13]
As we know, ICD is superior to antiarrhythmic drugs in increasing overall survival.[14] Studies have shown that, ICD was superior to amiodarone for the prevention of SCD.[15] In this study, due to the small number of patients taking amiodarone, and rare arrhythmia events during the follow-up results, so their effects could not be compared.
The European Guidelines have recommended ICD implantation in patients with NYHA class II-III. Although ICD treatment could reduce the risk of SCD in some NYHA class IV patients, these patients often survived less than 1 year due to the presence of severe diabetes, cerebral infarction and other non-cardiovascular diseases. Due to the high survival rate (50% at 10 years), heart transplantation became a choice for patients with severe HF.[16] However, due to the limited donor heart, these patients had a very high risk of SCD while waiting for surgery, which was a special indication for ICD implantation. Some retrospective studies showed that the use of ICD in patients waiting for heart transplantation can reduce overall mortality by 36% to 49%.[17] Interestingly, 2 patients in the DCM group successfully received heart transplantation in this study.
Among the patients included in this study, 3 (12%) in the ICM group and 20 (37.7%) in the DCM group have received CRT treatment.[18, 19] Reversing LV remodeling is one of the most important effects of CRT. However, it is difficult for CRT to reverse cardiac remodeling of ICM patients whose LV were covered with scar tissues to the same extent as DCM, which was consistent with our results.[20] In this study, more patients received CRT-D treatment in the DCM group, which may be a choice based on the patient’s situation in clinical practice, but there is a lack of function evaluation after receiving CRT-D treatment in both groups.
Limitations of our research need to be recognized. The sample size of this study was small, and the conclusions were greatly affected by individual differences. Multi-center studies could be conducted in the future.
In conclusion, DCM patients with ICD implantation compared could be benefit with a reduction in the risk of all-cause mortality and cardiovascular disease with ICM patients, while the occurrence of SCD had no difference in two groups.