CLINICAL MANIFESTATIONS OF VENTRICULAR ARRYTHMIAS
Common symptoms of ventricular arrhythmias include palpitations, dizziness, exercise intolerance, episodes of lightheadedness, syncope or sudden cardiac arrest leading to sudden death. Ventricular arrhythmias can also be asymptomatic and encountered unexpectedly as an irregular pulse or heart sounds on examination, or seen on a routine ECG, exercise test or cardiac ECG monitoring.
Syncope is a concerning symptom, that can be due to an episode of VT that produces severe hypotension, which often indicates that there is a risk for cardiac arrest and sudden death with arrhythmia recurrence. Although benign processes, such as reflex mediated neuro-cardiogenic (vasovagal) syncope and orthostatic hypotension, are the most common causes, it is important to consider the possibility of heart disease or a genetic syndrome causing VT. When these are suspected, hospitalization for further evaluation and monitoring is often appropriate.
Sustained VT may present as a wide QRS complex tachycardia that must be distinguished from supraventricular tachycardia with aberrancy (see Chap. 241) causing symptoms that range from mild to severe impairment with hypotension with syncope and imminent cardiac arrest. Sustained VT may degenerate to VF, particularly if it is rapid and polymorphic. Many patients who are at risk for VT have known heart disease and many have an implantable cardioverter defibrillator (ICD). In patients with an ICD, VT episodes may cause transient lightheadedness, palpitations or syncope that may be followed by a shock from the ICD (see below).
EVALUATION OF PATIENTS WITH DOCUMENTED OR SUSPECTED VENTRICULAR ARRYTHMIAS
There are several important considerations that guide evaluation of patients with documented or suspected cardiac arrhythmias. First, establish whether a ventricular arrhythmia is the cause of the symptoms or clinical presentation. Second, determine whether the arrhythmia is associated with a cardiac disease and establish the prognostic significance of that disease, and in particular whether it is associated with a risk of sudden cardiac death. Finally, define the likelihood of arrhythmia recurrence and the symptoms and risk imposed by the recurrence. The risk of cardiac arrest and sudden cardiac death are largely determined by the cause of the arrhythmia and the associated underlying heart disease.
The diagnosis of ventricular arrhythmias is established by recording of the arrhythmia on an ECG, by an implanted rhythm management device such as a pacemaker or ICD, or in some cases, initiation of the arrhythmia during an electrophysiologic study (Table 247-1). A 12 lead ECG of the arrhythmia should be obtained when possible and often provides clues to the potential site of origin and possible presence of underlying heart disease (see above). For patients with sustained wide complex tachycardia initial management is guided by the patient’s hemodynamic stability. The approach to sustained wide complex tachycardia is discussed in Chap. 249. The management of VT that causes cardiac arrest is discussed in Chap. 299. Once hemodynamic stability is restored further management is guided by ...