Abnormal Ventricular Mechanics Just Before a Premature Ventricular Contraction! Difficult to Predict What Will be Predictive

Dear Readers,

It is known that patients with a cardiomyopathy have abnormal left ventricular (LV) mechanics that, when pronounced, can lead to heart failure, and when alternating, can manifest as mechanical alternans. Premature ventricular contractions (PVCs) are common and usually benign. At times, PVCs can be excessive and result in a PVC-induced cardiomyopathy. Interestingly, a single PVC can transiently potentiate mechanical alternans for some time after its occurrence.¹ The mechanisms by which intermittent PVCs result in ventricular mechanical dysfunction during sinus beats are not clear.

Dr Edward Gerstenfeld and colleagues from the University of California-San Francisco have been investigating the relationship between PVCs and ventricular function, and appear to have discovered something very interesting.² They looked at the preprocedural echocardiograms in patients who underwent catheter ablation for frequent PVCs and used the LV strain measurements to study myocardial mechanics. Three measurements were made when the aortic valve was closed:

1. Global longitudinal strain (GLS; defined as the mean peak systolic strain in an 18-segment model)

2. LV dyssynchrony (defined as the time interval between the onset of the QRS complex and peak systolic strain in each of the 18 segments)

3. LV dyssynergy (defined as the difference between the maximum and minimum strain values)

As might be expected, all measures of LV mechanics were reproducibly normal during sinus rhythm beats remote from the PVC (this is not clear from their central illustration), abnormal with the PVC beats, and augmented during the post-PVC beats. This was not a surprise—it is well known that even systolic blood pressure is diminished with a PVC and potentiated after a PVC. What was a surprise was the observation that the sinus beats immediately before the PVCs were associated with abnormal LV mechanics. Why would the normal beat just before a PVC be associated with abnormal contraction? Premonition? Possibilities include a shared cause such as an increase in sympathetic tone before the PVC. Other possibilities include a decrease in calcium-induced calcium release causing mechanical dysfunction that rebounds with the next beat, triggering a delayed afterdepolarization that causes a PVC, which diminished mechanical function for other reasons.

The observation that LV mechanical function is abnormal just before a PVC is fascinating. This implies that the PVC is not the original sin—it is the beat before it. Although it is difficult to predict how this discovery might lead to a better understanding of LV dysfunction and PVCs, or therapeutics for heart failure, it is clear that we cannot always predict what is going to be predictive. 

Disclosures: Dr Knight reports that he has served as a consultant, speaker, investigator, and/or has received EP fellowship grant support from Abbott, AtriCure, Baylis Medical, Biosense Webster, Biotronik, Boston Scientific, CVRx, Medtronic, Philips, and Sanofi. He has no equity or ownership in any of these companies.

References

1. Panutich M, Knight BP. Augmentation of pulsus alternans by a premature ventricular beat. J Cardiovasc Electrophysiol. 2006;17:918. doi:10.1111/j.1540-8167.2006.00513.x

2. Alhede C, Higuchi S, Hadjis A, et al. Premature ventricular contractions are presaged by a mechanically abnormal sinus beat. J Am Coll Cardiol EP. Published online June 29, 2022. https://doi.org/10.1016/j.jacep.2022.05.005