VLPs May Not Reliably Detect Myocardial Fibrosis in Hypertrophic Cardiomyopathy

Ventricular late potentials (VLPs) on signal-averaged electrocardiography may not reliably detect myocardial fibrosis evaluated by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging in patients with hypertrophic cardiomyopathy, according to study results published in the Journal of Electrocardiology.

Although CMR is a common noninvasive imaging technique for identifying myocardial fibrosis, the technique is expensive, not universally available, and sometimes contraindicated. Conduction delays due in part to fibrosis are manifested on electrocardiogram (ECG) as VLPs, which may represent a useful marker of fibrotic disease.

In this single-center retrospective study, 41 consecutive patients with hypertrophic cardiomyopathy (mean age, 62 years; 75.6% men) in normal sinus rhythm who underwent risk assessments that included CMR imaging with LGE and signal-averaged electrocardiography were included. The extent and dispersion of LGE were assessed with CMR. The participants’ ECGs were examined for the occurrence of VLPs. The filtered QRS duration, the low amplitude signal (LAS) of the terminal filtered QRS under 40 𝜇V, and the root mean square (RMS) voltage of the late 40 ms of the QRS were measured. The presence of VLPs was confirmed when ≥two of three of the following criteria were met: LAS >38 ms, RMS <20 𝜇V, and filtered QRS duration >120 ms.

Standard 12-lead ECGs and echocardiograms were also performed. Comparisons between VLPs and LGE on CMR were made using the Mann-Whitney U test, and concordance and discordance rates between VLPs and myocardial fibrosis on CMR were calculated.

There were 13 patients (31.7%) who had LGE on CMR and 14 (34.1%) who had positive VLPs on signal-averaged ECG. Participants with vs without LGE were younger (53 years vs 67 years, respectively; P <.01) and had higher average maximum wall thickness (25.6 mm vs 20.4 mm, respectively; P <.01). No associations between LGE on CMR and VLPs, LAS, filtered QRS duration, or RMS were established. Concordance between LGE and VLP findings was observed in 26 individuals (63.4%).

Patients with discordant vs concordant results had predominantly anterior wall and interventricular septum LGE foci (60% vs 8%, respectively; P <.01), greater LGE volume (2.3±1.2 g/cm vs 0.0±0.8 g/cm, respectively; P <.01), and increased maximum wall thickness (24.1±4.0 mm vs 21.0±5.9 mm, respectively; P <.05), and reduced LGE volume per total number of LGE sites (1.5±0.7 vs 3.1±2.8; P <.01). No significant differences between patients with concordant and discordant VLP and LGE results were found in terms of minimum and maximum QRS durations or QRS dispersion.

Study limitations include its retrospective design, single-center setting, small sample size, highly selected population, inability to generalize findings, unavailability of T1- or T2-mapping on CMR, and lack of an established methodology to assess VLPs.

“Taken together, VLPs cannot be considered a reliable alternative to CMR for the detection of myocardial fibrosis in patients with [hypertrophic cardiomyopathy], although the detailed mechanism remains to be elucidated,” noted the authors.

Reference

Matsuki A, Kawasaki T, Kawamata H, et al. Ventricular late potentials and myocardial fibrosis in hypertrophic cardiomyopathy. J Electrocardiol. 2020;58:87-91. doi:10.1016/j.jelectrocard.2019.10.003