br Sustained monomorphic ventricular tachycardia
Sustained monomorphic ventricular tachycardia
Monomorphic VT is defined as sustained when lasting longer than 30s or requires earlier intervention due to haemodynamic instability . Most commonly, sustained MMVT occurs in the setting of diseased myocardium, but may also be idiopathic, occurring in patients with no detectable myocardial disease.
Sustained polymorphic ventricular tachycardia/ventricular fibrillation
Polymorphic ventricular tachycardia is defined as a ventricular rhythm faster than 100b.p.m., with clearly defined QRS complexes that change continuously from beat to beat indicating a changing ventricular activation sequence. The QT interval can either be normal or prolonged during intervening sinus rhythm in patients with PMVT. When PMVT occurs in the setting of a prolonged QT interval and has a distinctive pattern where the QRS complexes appear to be twisting around the isoelectric baseline, the arrhythmia is referred to as TdP . In cases of TdP, a long – short ventricular insulin receptor inhibitor length typically characterizes the initiating sequence, and the QT interval is almost always prolonged during sinus rhythm . Torsades de pointes VT is strongly associated with drugs or electrolyte abnormalities that delay repolarization. Thus, the occurrence of this arrhythmia should always prompt a search for precipitating factors that should be corrected.
The resuscitated cardiac arrest survivor Patients who are resuscitated from cardiac arrest must be rapidly evaluated for the presence of SHD, an inherited arrhythmia syndrome, a triggering VA focus, or a non-cardiac cause (see Fig. 6). Immediately following resuscitation, the clinical focus must be to minimize cerebral damage, often with the use of therapeutic hypothermia [161–164]. Evidence of MI or ischaemia usually requires prompt coronary angiography and revascularization . In addition, the function of both ventricles should be evaluated with echocardiography. These considerations have been discussed in detail in the preceding sections.
Ventricular arrhythmias in congenital heart disease
Ventricular arrhythmias are common in patients with CHD, often encountered as asymptomatic findings of PVCs and NSVT [250–254] on routine monitoring studies, and sometimes requiring treatment . Ventricular arrhythmias may occur in any con-genital defect, but the most common is tetralogy of Fallot and its variants, a malformation that has a long history of surgical repair, is prevalent, and often arrhythmogenic (Table 8 and Fig. 7). A recent consensus document addresses recognition and management details in greater detail [256,257]. The connection between PVCs or NSVT, SMVT, and risk of SCD is not well established in CHD patients, although occurrence of sustained VT is generally considered to imply an elevated risk of SCD. Sustained VT is a rare clinical arrhythmia in CHD, with relatively few cases reported in large series in recent decades. Sudden cardiac arrest causes approximately one-fifth of the mortality in adults with CHD, [258,259] with greater risk noted in certain types (e.g. tetralogy of Fallot, Ebstein׳s disease, left-sided obstructive disease) . However, the annual mortality rates are low compared with adult populations (0.1–0.3% per patient-year) [261–264]. Patients with CHD deemed at elevated risk for SCD are considered for ICD implantation, although this may be difficult in small patients or those with malformations that limit lead placement. Indications for ICD implantation in CHD are largely based on expert consensus. Risk assessment strategies, [265–270] descriptions of implantation techniques,  and current guidelines for ICD implantation in CHD [1,6,272,273] are available from other sources and not discussed here. A recent consensus document addresses recognition and management details in greater detail [256,257].
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