In terms of the definition of nonsustained ventricular tachycardia (NSVT), the 2014 European Heart Rhythm Society/American Heart Rhythm Society/Asia Pacific Heart Rhythm Society (EHRA/HRS/APHRS) “Expert Consensus on Ventricular Arrhythmias” (hereinafter referred to as “Consensus The 2006 American College of Cardiology/American Heart Association/European Society of Cardiology (ACC/AHA/ESC) Guidelines for the Treatment of Ventricular Arrhythmias and Prevention of Sudden Cardiac Death (“2006 Edition Guidelines”) remain consistent with the 2006 ACC/AHA/ESC Guidelines for the Treatment of Ventricular Arrhythmias and Prevention of Sudden Cardiac Death (“2006 Edition Guidelines”). (“2006 Edition Guidelines”): 3 or more consecutive ventricular beats with a frequency greater than 100 beats/min and a duration of less than 30 seconds are referred to as NSVT.
Throughout its length, the 2006 edition of the guidelines does not focus on NSVT. Recognizing the clinical prevalence of NSVT, the consensus devotes a larger space to detail the risk of sudden death, assessment methods and treatment recommendations for patients in the presence of NSVT, and presents them in the form of charts and graphs, which reflects the practicality of the consensus.
I. Clinical assessment of NSVT
For patients with NSVT, the consensus lists the commonly used standard assessment items and further assessment items, and gives the target population for which each test is applicable.
Evaluation of patients with NSVT
Standard evaluation items include history taking, physical examination, 12-lead electrocardiography, echocardiography and laboratory tests.
If these tests are not sufficient to identify the cause, further exercise testing, coronary angiography, cardiac MRI, genetic testing, and electrophysiological testing may be performed.
The purpose of the above tests is to determine whether NSVT patients have combined organic heart disease, because the prognosis of NSVT is related to the underlying heart disease, and the treatment principle is more important to treat the underlying disease than the arrhythmia.
II. Risk and treatment of structurally normal hearts with NSVT
The consensus classifies NSVT as normal cardiac structure combined with NSVT and abnormal cardiac structure combined with NSVT, given that the prognosis of NSVT is closely related to the underlying heart disease.
NSVT originating in the right ventricular outflow tract (RVOT) or left ventricular outflow tract (LVOT) often has characteristic ECG manifestations. These patients are at minimal risk of developing SCD and may receive pharmacologic therapy if symptomatic. Transcatheter radiofrequency ablation is an effective method to treat NSVT that has failed to respond to pharmacologic therapy or to cure this type of NSVT. Idiopathic folding left ventricular ventricular tachycardia (ventricular tachycardia) can be folded back through the pseudotendinous cord, and the choice of verapamil hydrochloride may terminate the ventricular tachycardia episode.
Even if drugs are effective, these ventricular tachycardias are often prone to recurrence, and radiofrequency ablation is recommended. Focal mechanisms of NSVT can originate in the ventricular papillary muscle with little risk of sudden death and can be treated with beta-blockers and radiofrequency ablation.
Exercise-induced NSVT is also common and has a poor prognosis if it occurs after the cessation of exercise. NSVT is considered benign when it occurs during exercise and disappears immediately after exercise cessation, and the athlete does not need to stop training, but the possibility of HCM should be excluded. NSVT appears polymorphic, regardless of whether the patient has symptoms or not, and the presence of coronary artery disease should be excluded.
The possibility of catecholamine-sensitive polymorphic ventricular tachycardia (CPVT) should also be considered if ventricular tachycardia is induced after an increase in heart rate to 120-130 beats/min during exercise, when the patient is at increased risk of sudden death. Other diseases with normal cardiac structure and NSVT should also be considered ion channel diseases, such as long QT syndrome (LQTS).
Risk and treatment of cardiac structural abnormalities with NSVT
Long-term cardiac monitoring in patients with ischemic heart disease, in which NSVT is detected in approximately 30% to 80% of them, is usually asymptomatic. There is no evidence that suppression of NSVT by drugs or radiofrequency ablation improves prognosis, and therefore treatment is not recommended for asymptomatic patients with NSVT.
The consensus lists several common organic heart diseases combined with NSVT disease and gives their SCD risk, diagnosis and treatment strategies. The presence of NSVT early in the onset of acute coronary syndrome (first few days) has no impact on long-term prognosis. If NSVT occurs after 48 hours of acute myocardial infarction, it is associated with poor long-term prognosis even if asymptomatic.
The significance of non-ischemic dilated cardiomyopathy with NSVT for long-term prognosis remains uncertain, and the consensus does not have clear recommendations for the treatment of such patients. Recurrent episodes of NSVT in patients with an embedded cardioverter-defibrillator (ICD) will increase the number of ICD discharges and increase mortality, and the ICD should be controlled to reduce the number of discharges.
If polymorphic NSVT is associated with myocardial ischemia, coronary perfusion should be improved as much as possible. NSVT associated with CPVT or LQTS is at great risk of lethal arrhythmias and treatment with β-blockers and ICDs is recommended. In case of tip-twist ventricular tachycardia (TdP), drugs that delay cardiac repolarization and prevent electrolyte disturbances should be avoided.
The following conditions are recommended for ICD installation.
① Any organic heart disease with an ejection fraction (EF) <35%;
(ii) if the reduction in cardiac function is not severe, EF < 40%, but persistent ventricular fibrillation or persistent ventricular tachycardia is induced by stimulation through electrophysiological examination procedures;
(iii) If the patient has a history of old myocardial infarction or syncope, even if the EF is >40%, the programmed stimulation of the heart can induce sustained ventricular tachycardia.
Asymptomatic patients with NSVT and EF > 40% are treated with the underlying disease and antiarrhythmic therapy is not recommended. In patients with HCM, placement of an ICD is recommended for NSVT regardless of the combination of other risks of sudden death. With the treatment of the underlying disease, the patient still has NSVT symptoms, and it is reasonable to apply antiarrhythmic drugs at this time.
Summary]
NSVT is a very common arrhythmia, and the 2014 expert consensus recommends that patients with NSVT be examined first to assess the presence of underlying heart disease in order to clarify their risk of SCD. The principle of treatment is to treat the primary disease, supplemented by antiarrhythmic therapy. No special treatment is required for arrhythmias in low-risk patients. High-risk patients can be treated with pharmacological therapy, radiofrequency ablation therapy and ICD placement based on improvement of the underlying disease.