ECG-derived Parameters for Risk Assessment

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ECG-derived Parameters for Risk Assessment

Similarly to other diseases with intraventricular conduction abnormalities such as IHD and cardiomyopathies, the presence of notched or fragmented QRS,^31,83 (see Figure 3) has been consistently demonstrated to indicate increased arrhythmic risk independently of other clinical and ECG variables (HR 4.9, 95 % CI 1.6-15.4 in the PRogrammed ELectrical stimUlation preDictive valuE (PERLUDE) study).⁸⁵ However, currently the presence of notching/fractionation is assessed only visually using arbitrary descriptive criteria (e.g. number of QRS peaks). The presence of late potentials on the signal-averaged ECG (SAECG) is another marker of intraventricular conduction disturbances which also indicates increased arrhythmic risk in BrS30 independently of QRS fractionation. The standard time-domain SAECG, however, cannot detect conduction abnormalities within the QRS complex, has uncertain value in patients with bundle branch block, and uses only a single-lead ECG complex which is derived from the XYZ orthogonal leads and does not contain any regional information.

 Among asymptomatic BrS patients, those with Brugada ECG pattern in the infero-lateral leads in addition to the right precordial leads,⁸⁸ (increased “spatial Brugada burden”) were recently demonstrated to have several times higher risk of VF compared to those with Brugada type 1 changes only in the right precordial leads.⁸⁹ On the other hand, the number of right precordial leads displaying type 1 pattern and the degree of J-point or ST-segment elevation do not seem to correlate with the arrhythmic risk.^35,36 The “high” (3rd or 2nd i.c. space) positions of leads V1 and V2 are diagnostically more sensitive than their standard positions in the 4th i.c. space^90,91,92 but prognostically their value is the same.⁹³

Infero-lateral early repolarisation (ER) (see Figure 4) is not only more common (up to 15 %94) in BrS patients,^70,94,95 but also carries up to 4-fold increased risk of spontaneous VF^67,70 and even higher risk if the ER has “malignant” morphology,⁹⁶ i.e. is associated with horizontal/descending (as opposed to rapidly ascending) ST segment after the J point.^68,75 The combination of infero-lateral ER and fractionated QRS complex seems to indicate indicate a particularly high arrhythmic risk.⁹⁷

Currently there are only limited data suggesting that other ECG parameters may indicate increased arrhythmic risk. These parameters include changes in repolarisation dynamics (QT/RR and Tpeak-Tend/RR intervals relations),⁹⁸ deep negative T wave in lead V1,⁹⁹< QTc interval more than 460 ms in lead V2 and prolonged Tpeak-Tend interval,¹⁰⁰ dynamic alterations in the amplitude of the ST elevation,¹⁰¹ prolonged PR-interval,⁹³ presence of atrial arrhythmias,^60,61,102 and augmentation of the ST segment elevation during the early recovery phase of exercise test.¹⁰³