**5. Conclusions**

is present. When a PVC burden is greater than 10% (approximately 10,000 PVCs/24 h), the risk of PVC-induced cardiomyopathy is significant. Therefore, such high-burdened PVCs have to be treated when they are symptomatic. When they are asymptomatic, a close follow-up with repeat echocardiography and Holter monitoring should be considered to detect any occurrence of PVC-induced cardiomyopathy. In patients with fewer PVCs, further investigation is only necessary should the symptoms increase. For patients without SHD and mild symptoms, education of the benign nature of this arrhythmia and reassurance should be considered as the first step in the treatment of patients with PVCs. For patients whose symptoms are not effectively managed in this manner, beta-blockers or non-dihydropyridine calcium antagonists may be attempted although the efficacy of these agents is quite limited with only 10–15% of patients achieving a 90% PVC suppression, similar to placebo [4, 5]. It should also be recognized that these agents may themselves produce significant side effects rather than relieve the PVC symptoms. Membrane-active anti-arrhythmic drugs (AADs) are more effective for suppressing PVCs and can be attempted when beta-blockers or non-dihydropyridine calcium antagonists are not effective. Because these agents may increase the risk of mortality in patients with significant SHD, perhaps with the exception of amiodarone, caution is

When idiopathic PVCs are refractory to medication or patients cannot tolerate medication, catheter ablation can be a next option for their treatment. Randomized trials of PVC suppression with catheter ablation have not been performed. However, multiple studies have revealed that catheter ablation is highly successful with PVC elimination in 74–100% of highly symptomatic patients with a very high PVC burden [4, 5]. Procedural success may be dependent on the site of the VA origin with a lower efficacy reported for IVAs with epicardial foci and anatomical challenges than for other IVAs [1–5]. Although complete PVC elimination is the goal of ablation, partial success with a significant reduction in the PVC burden may still be associated with significant improvement in the symptoms as well as LV systolic function. Catheter ablation of IVAs may be less successful when multiple morphologies of PVCs present or the clinical PVC morphology cannot be induced at the time of the procedure [1–5]. The published complication rates of catheter ablation for PVC suppression are generally low (<1%) [1–5]. According to the current recommendations of the experts' consensus, catheter ablation of PVCs may be considered for highly selected patients who remain very symptomatic despite conservative treatment or for those with high PVC burdens associated with a

Idiopathic VTs are basically monomorphic and hemodynamically stable. When SHD is absent, sustained idiopathic VTs are generally associated with an excellent prognosis [1, 4, 5]. Idiopathic VTs rarely can have a malignant clinical course, usually with a very rapid rate or a short initiating coupling interval [1, 4, 5]. Idiopathic non-sustained VTs (NSVTs) usually present with frequent PVCs with the same QRS morphology, and most of them originate from the RVOT or LVOT. These arrhythmias only require treatment if they are symptomatic, incessant, or produce LV dysfunction. The treatment of these VTs is either medical with beta-blockers, non-hydropyridine calcium blockers, or class IC drugs, or catheter ablation with a high success rate and low risk of complications [1, 4, 5]. Non-sustained and sustained VTs with a focal mechanism likely based on abnormal automaticity may also occur from the papillary

advised before using them for PVC suppression.

96 Cardiac Arrhythmias

decline in the LV systolic function [4, 5].

The sites of IVA origins have been increasingly recognized for the past two decades. IVAs usually originate from specific anatomical structures, commonly endocardial but sometimes epicardial, and exhibit characteristic ECGs based on their anatomical background. IVAs are basically benign, but they require medical treatment or catheter ablation when IVAs are symptomatic, incessant, or produce LV dysfunction.
