**6. Future directions**

risk models have not been evaluated in a prospective study and are entirely data derived. [68] This being said, it seems inevitable that the guidelines for the implantation of ICDs will be

Implantation of ICD in cardiomyopathy other than ischemic and non-ischemic dilated cardiomyopathy is not supported by evidence from large ICD trials. The majority of patients enrolled in the large ICD trials were post-MI patients with LV dysfunction and patients with dilated non-ischemic cardiomyopathy. In other forms of cardiomyopathies, like hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, sarcoidosis and other infiltrative cardiomyopathies, secondary prevention of sudden cardiac death with ICD implantation in survivors of SCD and in patients with history of sustained ventricular tachycardia is generally accepted clinical practice. However, implantation of ICD for primary prevention of SCD has remained an unsolved issue in these patients. This has become more of an issue with development of more effective screening of family members, and preparticipation screening of athletes. Risk stratification in them has been attempted for each of

Primary prevention in patients with *hypertrophic cardiomyopathy* is guided by multiple risk factors for sudden cardiac death as discussed above. These risk factors have been defined as discussed earlier and include (1) a family history of premature HCM-related sudden death; (2) a history of unexplained syncope; (3) multiple and/or prolonged runs of nonsustained VT on serial 24-hour ambulatory ECG monitoring at heart rates ≥120 beats/min; (4) a hypotensive or attenuated blood pressure response to exercise; and (5) massive left ventricular (LV) hypertrophy (maximum wall thickness ≥30 mm). The ACC/AHA/ESC guidelines on sudden cardiac death and ventricular arrhythmia recommend implantation of ICD in patients with

Primary prevention of SCD in *arrhythmogenic right ventricular cardiomyopathy* is also guided by a set of high risk factors. A multicenter study evaluated the use of ICD for primary prophylaxis of SCD in patients with ARVC with at least one risk factor for SCD. These included syncope, NSVT, a malignant family history, and inducibility of ventricular arrhythmias with program‐ med ventricular stimulation. Over a mean follow-up of 58 months 25 of 106 patients received appropriate ICD intervention. ACC/AHA/ESC guidelines considers secondary prevention of SCD with AICD to be reasonable (class IIa) in patients with ARVC considered high risk due to LV involvement, one or more affected family member with SCD, or undiagnosed syncope when VT or VF has not been excluded as the cause of syncope, while receiving chronic optimal medical therapy. [165] ACC/AHA/HRS guidelines for device therapy for arrhythmia lists ARVC as reasonable indication for primary implantation of ICD in the presence of one or more

In patients with left ventricular non-compaction, ICD implantation is generally performed for secondary prevention and for primary prevention in the presence of LV systolic dysfunction. Although patients with normal LV systolic function or mild LV systolic dysfunction may be prone to SCD, [125] lack of data makes the decision ICD implantation in these patients difficult.

one or more of these risk factors, for the primary prevention of SCD. [165]

refined in the future and that risk scores will be incorporated.

**5.6. ICD in other forms of cardiomyopathies**

these groups.

194 Cardiomyopathies

risk of SCD. [166]

The prevention of sudden cardiac death in patients with cardiomyopathy has evolved dramatically in recent years. With the increasing use of ICDs in conjunction with pharmaco‐ therapy for heart failure, large number patients have benefited from prevention of SCD. However, risk assessment for SCD is still far from accurate and many patients receiving ICDs ultimately will not use them. Although, attempts have been made to refine the risk stratifica‐ tion, the current risk stratification is insufficient at least for many kinds of cardiomyopathies. Data from subgroup analysis do provide some parameters for refining risk stratification, but testing them in a prospective study will be an expensive and time-consuming undertaking. Risk stratification for less common forms of cardiomyopathy has not largely been possible. Some newer parameters like genetic evaluation may help in refining the risk assessment in the future as more data on genetic analysis in various forms of cardiomyopathy comes forth. Finally, newer pharmacotherapy may help in reducing the risk of SCD in these patients.
