**8. Echocardiographic parameters**

Reduced baroreflex sensivity, a quantitative index of primarily vagal reflexes, evaluated by the phenylephrine method or by a non-invasive measurement [55], is also useful in assess‐

There is evidence that regional and global sympathetic denervation could predispose to ven‐ tricular arrhythmias in post-MI patients. The denervated but viable myocardium could be

Using imaging methods for the evaluation of the sympathetic system in vivo, in human and animal models, such as [12]3I-mIBG cardiac imaging, it has been reported that the mismatch between sympathetic innervation and perfusion could be associated with increased risk of

The extent of sympathetic denervation measured at 4-Hour delayed 123I-mIBG SPECT imag‐ ing has been correlated with inducibility of ventricular arrhythmias in electrophysiological testing [60]. In another study including patients with advanced heart failure, late [12]3I-MIBG SPECT defect score was also an independent predictor for ventricular arrhythmias causing appropriate ICD therapy (primary end point) as well as the composite of appropri‐

More studies are required to determine the role of autonomic imaging in post-MI patients,

Patients after MI have the highest induction rates in electrophysiological study and the pres‐ ence of ejection fraction less than 40% and asymptomatic NSVT is associated with a induci‐

Programmed ventricular stimulation identifies most patients at risk for sustained monomor‐ phic ventricular tachycardia associated with reentrant circuits that result of the healing proc‐

Electrophysiological study was required in MADIT, MUSTT, BEST–ICD [62], but not in

Based on these trials, electrophysiological testing is not required before ICD implantation. It is recommended (class I) for diagnostic evaluation of symptoms suggestive of tachyarrhyth‐ mias, to guide VT ablation and for differential diagnosis of a wide-QRS-complex tachycar‐

Electrophysiological study is also reasonable for risk stratification in patients with NSVT, and LVEF equal or less than 40% (Class IIa). Inducibility of VT in patients with NSVT is as‐

ing the risk of SCD [56, 57].

50 Cardiac Defibrillation

**6. Autonomic imaging**

ventricular arrhythmias.

hyperresponsive to circulating catecholamines [58, 59].

ate ICD therapy or cardiac death (secondary end point) [27]

possibly detailing their correlation with CMR findings.

**7. Electrophysiological testing**

bility of 20-40% [22], [61].

ess after infarction [22].

MADIT –II and SCD-HeFt trials.

dias of unclear mechanism [14].

The echocardiogram is a fundamental exam for the identification of candidates for ICD im‐ plantation. Although an LVEF of <40% is commonly used for stratification of patients at risk for ventricular arrhythmias, it does not allow accurate discrimination of patients with or without sudden arrhythmic death. Moreover, sudden arrhythmic death also occurs in pa‐ tients with an LVEF of ≥40% [64].

The technical advances in echocardiography will probably allow exploring the appraisal val‐ ue of new variables beyond the ejection fraction of the left ventricle in the risk stratification.

In a unicenter study a greater involvement of peri-infarct zone longitudinal strain was inde‐ pendently associated with an increased risk of having an appropriate ICD therapy on followup. In such study the odds of dying in a patient with a peri-infarct zone strain value of -6% was approximately 11.5 times that of a patient with a peri-infarct zone strain value of -17% [65].

## **9. Cardiac magnetic resonance**

Cardiac MRI allows characterization of cardiac morphology in patients with poor echo car‐ diographic window and provides an estimate of the location and amount of intramyocardial fibrosis.

The presence of myocardial scar or fibrosis as measured by delayed enhancement after ad‐ ministration of gadolinium has been recently associated with post-infarct arrhythmic death [66], [67] suggesting that contrast-enhanced MRI may enable better risk stratification for ICD implantation among patients with prior MI compared with traditional variables such as LVEF and NYHA class.

Roes S et al identified infarct tissue heterogeneity on contrast-enhanced MRI as a strong pre‐ dictor of spontaneous ventricular arrhythmia in ICD therapy recipients [68]. In a more re‐ cent study from a tertiary center which included the monitoring of 52 patients, it was identified a relationship between the transmurality of infarction and the occurrence of spon‐ taneous ventricular arrhythmias in patients with chronic ischemic cardiopathy [69].
