Non-invasive myocardial work: an echocardiographic measure of post-infarct scar on contrast-enhanced cardiac magnetic resonance imaging

Background

Late gadolinium contrast enhanced cardiac magnetic resonance (LGE CMR) imaging accurately quantifies the extent of fibrosis and transmurality in chronically infarcted left ventricular (LV) segments, and identifies viability. Moreover, CMR characterizes the remote, non-infarcted zone, which is an emerging region of interest following ST-segment elevation myocardial infarction (STEMI). Non-invasive myocardial work is a novel LV function parameter - calculated from speckle-tracking strain echocardiography and sphygmomanometrically-determined blood pressure, which has shown excellent correlation with invasively measured myocardial work.

Purpose

To explore the relation of non-invasively estimated parameters of LV myocardial work to post-infarct scar on LGE CMR, and to compare myocardial work indices between the infarct core and remote zone in STEMI patients who were treated with primary percutaneous coronary intervention (PCI).

Methods

Patients with a STEMI who underwent primary PCI and LGE CMR, in addition to echocardiographic studies where non-invasive myocardial work analysis was feasible, were included. The LV was subdivided into non-infarcted, non-transmural and transmurally infarcted segments. The remote zone was defined as the non-infarcted myocardial segment diametrically opposed to the infarct core, without any evidence of LGE. Myocardial work indices were compared with linear mixed models, ANOVA and Wilcoxon signed rank tests.

Results

53 patients (89% male, age 58±9 years) and 689 segments were analysed. The mean scar burden comprised 14±7% of the total LV mass and 76 (11%) segments showed transmural LGE. The following non-invasive myocardial work indices: myocardial work index (MWI), constructive work (CW) and myocardial work efficiency (MWE) showed a significant inverse relationship with infarct transmurality (p<0.05 for all comparisons) while a positive trend was observed for wasted work (WW) (p=0.086) (Figure 1). The core zone demonstrated lesser MWI (1237±568 vs. 1514±518 mmHg%; p=0.010), CW (1331±627 vs. 1827±537 mmHg%; p<0.001) and MWE (92 (84–98) vs. 98 (95–99) %; p<0.001) as well as greater WW when compared to the remote zone (107 (26–196) vs. 26 (10–90) mmHg%; p=0.001).

Conclusions

In STEMI patients who underwent primary PCI, MWI, CW and MWE were significantly related to the extent of transmural infarction, while WW demonstrated a trend. MWI, CW and MWE were significantly lower, and WW higher, in the core zone compared to the remote zone. Non-invasive myocardial work indices may provide an echocardiographic method for determining post-infarct viability, as well as characterization of the remote zone.

MW and scar transmurality on LGE CMR

Funding Acknowledgement

Type of funding source: None

Progressive left ventricular post-infarction remodelling: impact on outcome

Background

While the presence left ventricular (LV) remodelling after ST-segment elevation myocardial infarction (STEMI) is known to worsen prognosis, the impact of progressive vs. stable LV remodelling on outcome has not been established.

Purpose

To investigate the impact of progressive LV remodelling on outcome in STEMI patients who were treated with primary percutaneous coronary intervention (PCI) and optimal pharmacotherapy.

Methods

Baseline, 3-, 6- and 12-month echocardiograms were analysed. Early LV remodelling (ER) was defined as a ≥20% increase in LV end-diastolic volume (EDV) during the first 3 months post-STEMI, and mid-term remodelling (MTR) as ≥20% LVEDV change by 6 months. Progressive LV remodelling was defined according to spline curve analyses: ≥0% LVEDV increase by 6 months (i.e. further increase after 3 months) for ER, and ≥20% by 12 months (i.e. an additional increase after 6 months) for MTR. The impact of progressive LV remodelling on outcome was evaluated with a Log rank test.

Results

589 STEMI patients (mean age 61±12 years, 78% male) who demonstrated LV remodelling in the first 6 months post-infarct, were analysed: 408 (69%) ER and 181 (31%) MTR. Progressive LV remodelling occurred in 146 (36%) ER and in 12 (7%) MTR. After a median follow-up of 90 (IQR 64–117) months, 39 (10%) ER were hospitalised for heart failure. 25 (14%) MTR remodellers died after a median follow-up of 86 (IQR 66–112) months. Progressive LV remodelling in ER led to a higher rate of heart failure hospitalisation (P=0.017 vs. non-progressive ER, Fig. 1A) but no mortality difference (P=0.10 vs. non-progressive ER). In contrast, MTR with progressive LV remodelling experienced worse survival (P=0.01 vs. non-progressive MTR, Fig. 1B) but no increase in heart failure hospitalisation (P=0.65 vs. non-progressive MTR).

Conclusions

Progressive LV remodelling causes an increased risk of heart failure in ER post-infarct, vs. higher mortality in MTR. These two patterns of progressive, post-infarct LV remodelling possibly represent different underlying pathophysiological mechanisms: i.e. evolution of true post-infarct remodelling in ER, vs. natural history of established heart failure in MTR.

Figure 1

Funding Acknowledgement

Type of funding source: None