What is the threshold of cardiac ectopy (premature heartbeats) that can cause cardiomyopathy (heart muscle disease)?

From the Guidelines

The threshold of cardiac ectopy that can cause cardiomyopathy is a premature ventricular contraction (PVC) burden of approximately 10% or more of total heartbeats, as evidenced by a study published in Circulation in 2016 1. This threshold is supported by the finding that a PVC burden ≥24% is independently associated with cardiomyopathy, and radiofrequency ablation can result in normalization of ejection fraction (EF) in 82% of patients with left ventricular (LV) dysfunction within 6 months 1. The development of PVC-induced cardiomyopathy depends on multiple factors beyond just the absolute number of PVCs, including:

• PVC characteristics (QRS duration, coupling interval, morphology)
• Duration of exposure
• Individual patient factors such as underlying heart disease The mechanism behind PVC-induced cardiomyopathy involves:
• Ventricular dyssynchrony
• Altered calcium handling
• Abnormal ventricular loading conditions that over time lead to adverse cardiac remodeling For patients with high PVC burdens, especially those with symptoms or early signs of left ventricular dysfunction, treatment options include:
• Antiarrhythmic medications (such as beta-blockers, calcium channel blockers, or class III antiarrhythmics)
• Catheter ablation, with the latter often being more effective for long-term PVC suppression and reversal of cardiomyopathy It is essential to note that the presence of PVCs in a structurally normal heart and subsequent LV dysfunction can infer a direct link between PVCs and cardiomyopathy, as demonstrated in an animal model 1. In contrast, a study published in Circulation in 2015 1 suggests that PVCs recorded at a frequency of >2000 per 24 hours have a higher likelihood of association with underlying cardiac disease, estimated at 30% in this subgroup. However, this study does not provide a clear threshold for PVC-induced cardiomyopathy, and the more recent study 1 provides a more specific and relevant threshold for clinical practice. Therefore, a PVC burden of approximately 10% or more of total heartbeats is the most relevant threshold for considering the risk of cardiomyopathy.

From the Research

Threshold of Cardiac Ectopy for Cardiomyopathy

• The exact threshold of cardiac ectopy that can cause cardiomyopathy is not well-defined, but studies suggest that a high burden of ventricular ectopy can lead to left ventricular dysfunction 2, 3, 4, 5.
• A study published in 2005 found that patients with repetitive monomorphic ventricular ectopy originating from the right ventricular outflow tract had a similar burden of ectopy regardless of whether they had preserved or depressed ventricular function 2.
• Another study published in 2019 found that a ventricular ectopic burden of more than 24% in adults may lead to left ventricular dysfunction, but this threshold may be different in children 4.
• In children, a burden of more than 30% may be associated with an increased risk of developing left ventricular dysfunction 4.
• The development of cardiomyopathy from frequent premature ventricular contractions (PVCs) is likely multifactorial, relating to the burden itself, presence of higher levels of ectopy, and duration of ventricular ectopy 4, 5.

Risk Factors for Ectopy-Mediated Cardiomyopathy

• Risk factors for ectopy-mediated cardiomyopathy include age, male gender, PVC burden, non-right ventricular outflow tract sites of origin, PVC QRS duration, and PVC minimum coupling interval 3.
• However, only gender persisted as a significant predictor on multivariate analysis 3.
• Other studies have suggested that the presence of symptoms, such as palpitations, and signs of increasing left ventricular dimensions or dysfunction should be treated with medication or catheter ablation 5.

Treatment of Ventricular Ectopy

• Treatment of ventricular ectopy depends on the underlying cause and severity of symptoms, but may include catheter ablation, antiarrhythmic medications, or a combination of both 2, 3, 5, 6.
• β-Blockers are currently considered first-line therapy for ventricular ectopy, with amiodarone as a backup option 5, 6.
• Catheter ablation may be a preferable approach in selected patients, particularly when β-blocker therapy has been ineffective or not tolerated 5.