Regional Heterogeneity of Systolic Dysfunction Is Associated with Ventricular Dyssynchrony in Patients with Idiopathic Dilated Cardiomyopathy and Narrow QRS Complex

Premature Ventricular Contractions Are Presaged by a Mechanically Abnormal Sinus Beat

BACKGROUND

Frequent premature ventricular contractions (PVCs) can lead to cardiomyopathy; it is unclear if there are abnormal myocardial mechanics operative in the PVC and non-PVC beats.

OBJECTIVES

The aim of this study was to investigate regional and global myocardial mechanics, including dyssynchrony, in patients with frequent PVCs.

METHODS

Fifty-six consecutive patients referred for PVC ablation were prospectively studied. During sinus rhythm (SR) and PVC beats, left ventricular (LV) global longitudinal strain (GLS), LV dyssynchrony (measured as the SD of time to peak GLS), and dyssynergy (measured as maximum regional strain minus minimum regional strain at aortic valve closure) were quantified using 2-dimensional strain echocardiography. GLS, dyssynchrony, and dyssynergy were compared in remote SR, pre-PVC SR, PVC, and post-PVC SR beats.

RESULTS

In SR beats remote from the PVC, GLS was -17.3% ± 4%, dyssynchrony was 49 ± 14 ms, and dyssynergy was 22% ± 9%. Myocardial mechanics were significantly abnormal during PVCs compared with remote SR beats (GLS -7.7% ± 3% [P < 0.001], dyssynchrony 115 ± 37 milliseconds [P < 0.001], and dyssynergy 26% ± 10% [P < 0.001]). There were significant mechanical abnormalities in the SR beat preceding the PVC, which demonstrated significantly lower LV strain (pre-PVC SR, -13% ± 4%; P < 0.001) and more dyssynchrony (pre-PVC SR, 63 ± 19 milliseconds; P < 0.001) compared with remote SR beats. Dyssynergy was significantly higher for pre-PVC SR and PVC beats compared with remote SR (pre-PVC SR, 25% ± 8% [P < 0.001]; PVC, 26% ± 10% [P < 0.001]).

CONCLUSIONS

In patients with frequent PVCs, the SR beat preceding the PVC demonstrates significant mechanical abnormalities. This finding suggests that perturbations in cellular physiological processes such as excitation-contraction coupling may underlie the generation of frequent PVCs.

The interaction of QRS duration with cardiac magnetic resonance derived scar and mechanical dyssynchrony in systolic heart failure: Implications for cardiac resynchronization therapy

Background

Trials using echocardiographic mechanical dyssynchrony (MD) parameters in narrow QRS patients have shown a negative response to CRT. We hypothesized MD in these patients may relate to myocardial scar rather than electrical dyssynchrony.

Methods

We determined the prevalence of cardiac magnetic resonance (CMR) derived measures of MD in 130 systolic heart failure patients with both broad (≥ 130 ms - BQRS) and narrow QRS duration (< 130 ms - NQRS). We assessed whether late gadolinium enhancement derived scar might explain the presence of MD amongst narrow QRS patients. Dyssynchrony was calculated on the basis of a systolic dyssynchrony index (SDI).

Results

Fifty-nine patients (45%) had a NQRS and the remaining had QRS ≥ 130 ms (BQRS group). 25% of NQRS patients had MD based on SDI. In all narrow and broad QRS patients with MD there was a significantly lower scar volume than those without MD (7.4 ± 10.5% vs 13.7 ± 13.3% vs. p < 0.01). This was the case in the BQRS group with a significantly lower scar burden in patients with MD (5.0 ± 7.7% vs 15.4 ± 15.6%, p < 0.01). Notably in the NQRS group this difference was absent with an equal scar burden in patients with MD 13.3 ± 13.9% and without MD 12.5 ± 11%, p = 0.92.

Conclusions

25% of patients with systolic heart failure and a NQRS (< 130 ms) have CMR derived mechanical dyssynchrony. Our findings suggest MD in this group may be secondary to myocardial scar rather than electrical dyssynchrony and therefore not amenable to correction by CRT. This may give insight into non-response and potential harm from CRT in this group.

Left ventricular myocardial function assessed by three-dimensional speckle tracking echocardiography in Takotsubo cardiomyopathy

BACKGROUND

We aimed to investigate left ventricular (LV) functional recovery in Takotsubo cardiomyopathy (TC) using three-dimensional (3D) speckle tracking echocardiography.

METHODS

Twenty-one patients with TC who underwent routine and 3D echocardiography as well as electrocardiography were enrolled. 3D images were analyzed to measure 3D radial strain and area tracking (area change of each LV segment). Postsystolic shortening (PSS) or thickening (PST) was defined as a further shortening or thickening occurred after the end-systole. 3D echocardiography and ECG were repeated at 4 weeks and 6 months later.

RESULTS

Mean age was 70.9±11.1 years, and 18 (86%) patients were female. All patients presented classical type of TC with apical ballooning. LV ejection fraction (EF) improved from 49.9±7.2 to 64.9±6.0% (P<.001) at 4 weeks without segmental wall-motion abnormality. However, PSS or PST still existed in 43% of LV segments, and electrocardiographic abnormality was also observed in 51% at 4 weeks and disappeared at 6 months. Mean 3D radial strain decreased from baseline to 6 months at base (36.1±19.6 vs 28.0±12.6%, P=.04), whereas it increased at mid (16.2±7.2 vs 28.7±9.1%, P=.03) and the apex (8.0±4.4 vs 21.2±7.9%, P<.001). Mean area tracking increased from baseline to 6 months at mid and apex (-28.5±9.5 vs -44.5±9.6%, P<.001 for mid, and -24.2±13.0 vs -42.9±16.8%, P=.002 for the apex), while it did not change at base (-37.0±8.9 vs -41.9±9.6%, P=NS).

CONCLUSIONS

Patients with TC show abnormal wall motion during acute phase. Even after LV wall-motion recovery, subtle abnormalities of regional LV function appear to persist at 4 weeks followed by normalization at 6 months.

Phase analysis of gated blood pool SPECT for multiple stress testing assessments of ventricular mechanical dyssynchrony in a tachycardia-induced dilated cardiomyopathy canine model

BACKGROUND

Stress-induced dyssynchrony has been shown to be independently correlated with clinical outcomes in patients with dilated cardiomyopathy (DCM) and narrow QRS complexes. However, the extent to which stress levels affect inter- and intraventricular dyssynchrony parameters remains unknown.

METHODS

Ten large dogs were submitted to tachycardia-induced DCM by pacing the right ventricular apex for 3-4 weeks to reach a target ejection fraction (EF) of 35% or less. Stress was then induced in DCM dogs by administering intravenous dobutamine up to a maximum of 20 μg·kg-1·min-1. Hemodynamic and ventricular dyssynchrony data were analyzed by left ventricular (LV) pressure measurements and gated blood pool SPECT (GBPS) imaging. In order to assess mechanical dyssynchrony in DCM subjects and compare it with that of 8 normal counterparts, we extracted the following data: count-based indices of LV contraction homogeneity index (CHI), entropy and phase standard deviation, and interventricular dyssynchrony index.

RESULTS

A significant LV intraventricular dyssynchrony (CHI: 96.4 ± 1.3% in control vs 78.6% ± 10.9% in DCM subjects) resulted in an intense LV dysfunction in DCM subjects (EF: 49.5% ± 8.4% in control vs 22.6% ± 6.0% in DCM), compared to control subjects. However, interventricular dyssynchrony did not vary significantly between the two groups. Under stress, DCM subjects showed a significant improvement in ventricular functional parameters at each level (EF: 22.6% ± 6.0% at rest vs 48.1% ± 5.8% at maximum stress). All intraventricular dyssynchrony indices showed a significant increase in magnitude of synchrony from baseline to stress levels of greater than or equal to 5 μg·kg-1·min-1 dobutamine. There were individual differences in the magnitude and pattern of change in interventricular dyssynchrony during the various levels of stress.

CONCLUSIONS

Based on GBPS analyses, different levels of functional stress, even in close intervals, can have a significant impact on hemodynamic and intraventricular dyssynchrony parameters in a DCM model with narrow QRS complex.

Narrow QRS systolic heart failure: is there a target for cardiac resynchronization?

Cardiac resynchronization therapy has revolutionized the management of systolic heart failure in patients with prolonged QRS during the past 20 years. Initially, the use of this treatment in patients with shorter QRS durations showed promising results, which have since been opposed by larger randomized controlled trials. Despite this, some questions remain, such as, whether correction of mechanical dyssynchrony is the therapeutic target by which biventricular pacing may confer benefit in this group, or are there other mechanisms that need consideration? In addition, novel techniques of cardiac resynchronization therapy delivery such as endocardial and multisite pacing may reduce potential detrimental effects of biventricular pacing, thereby improving the benefit/harm balance of this therapy in some patients.