Anatomical considerations for the nontransvenous implantable cardioverter-defibrillator implantation: A cadaver-based analysis.

Background: Sudden cardiac death is a severe health issue, responsible for many deaths annually in the United States. It occurs unexpectedly in individuals without a prior diagnosis of a life-threatening condition. Implantable cardiac defibrillators (ICDs), introduced in the 1980s, have been pivotal in improving survival rates for high-risk patients by detecting and correcting dangerous cardiac rhythms. Traditional transvenous ICD implantation, involving leads threaded through veins, carries risks such as vascular damage and infection. Nontransvenous ICD options, such as subcutaneous ICDs (S-ICDs) and extravascular ICDs, present alternative approaches that may reduce these risks. Implantation techniques for S-ICDdevices have evolved greatly over the years, with the most recently recommended approach being an intermuscular technique. However, this anatomical space has not been adequately studied. Objective: The purpose of this study was to better understand the anatomical variations associated with S-ICD implantation. Methods: This investigation involved a detailed examination of 18 cadaveric specimens (12 females and 6 males) to map the anatomical relationships between the latissimus dorsi muscle (LDM), the serratus anterior muscle, and the long thoracic nerve (LTN), which are critical for refining nontransvenous ICD implantation techniques. Measurements included the distance from the anterior border of the LDM to the back, the anterior-posterior diameter of the chest at the fifth and seventh rib levels, and the positioning of the LTN relative to the chest wall. Results: The analysis showed that at the fifth rib level, the average distance from the back to the LDM border was 7.5 cm, and at the seventh rib level, it was 7.6 cm. The overall average distance from the back to the LDM border across both rib levels was 7.5 cm. The LTN was positioned at an average distance of 8.5 cm from the back at the fourth rib, decreasing to 5.7 cm at the sixth rib. The LTN tended to be more anterior in males than in females, but this difference was not statistically significant. Conclusion: The findings highlight the importance of accurate anatomical knowledge for the effective placement of nontransvenous ICDs. Understanding the specific anatomical layout of the LDM, the serratus anterior muscle, and the LTN is crucial to prevent complications such as LTN injury and to improve the safety and efficacy of ICD implantation. The results advocate for personalized assessment approaches to improve procedural success and patient outcomes in nontransvenous ICD implantation.