Cardiac magnetic resonance strain and mechanical dispersion assessment in patients with chronic total coronary artery occlusion

Background

Chronic total occlusions (CTO) are a frequent angiographic finding. Viability of CTO-subtended myocardium is dependent on the presence of an adequate collateral circulation. At rest, collateral supply may be sufficient to avert ischaemia and maintain normal systolic function. However, it remains unclear whether CTO-subtended myocardium may be considered truly normal, or whether subtle functional abnormalities may be present at rest.

Purpose

To determine whether, in the absence of infarction and hibernation, CTO-subtended myocardium remains functionally normal or whether abnormalities of strain and/or mechanical dispersion may be present at rest.

Methods

In a retrospective, single centre, observational study, we studied patients with ≥1 angiographically-diagnosed CTO referred for clinical stress perfusion cardiovascular magnetic resonance (CMR), and compared healthy volunteers (HVs) with a normal stress CMR scan. CMR imaging comprised functional and scar assessment with qualitative [visual] evaluation of infarction and segmental wall motion. Patients with infarction and/or wall motion score index (WMSI) ≥1 were excluded from further analysis. In remaining CTO subjects and HVs, segmental peak systolic longitudinal strain and circumferential strain were analysed (in 3 long-axis planes and 3 short-axis planes, respectively) and mechanical dispersion for both orientations was computed. Image analysis was performed using Medis (QStrain) software blinded to all clinical information.

Results

From a total of 389 patients with ≥1 angiographically-diagnosed CTO, 68 had normal WMSI and no infarction (63.0±11.7 years, 79.4% male, LVEF 62.6±4.5%). Fifty HVs (61.1±7.0 years, 74.0% males, LVEF 61.1±5.3%) were also studied. The majority of CTO patients had concomitant coronary artery disease in at least one non-CTO vessel (n=37, 54.4%). GLS was lower in CTO patients than HVs (−21.8%±1.5% versus −24.0±1.1%; p<0.0001; Figure 1). By contrast, GCS was greater in CTO patients (−32.7±2.5% versus −28.8±2.1%; p<0.0001). Mechanical dispersion was increased in CTO patients (Figure 2), both longitudinally (90.3±14.6 ms in CTO patients versus 68.6±11.1 ms in HVs; p<0.0001) and circumferentially (66.7±9.1 ms versus 55.3±6.6 ms, respectively; p=0.02).

Conclusion

Subclinical changes in left ventricular dynamics are present at rest in CTO patients with fully viable myocardium and no evidence of resting regional wall abnormality. Further study is warranted to evaluate the potential association between mechanical dispersion and arrhythmic events in CTO.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): NIHR Clinician Scientist Award (CS-2018-18-ST2-007 to J.R.A.) and Research Professorship award (RP-2017-08-ST2-007 to G.P.M.). Figure 1. Strain analysis. CTO vs HVFigure 2. Mechanical dispersion. CTO vs HV

Cardiovascular magnetic resonance to predict clinical outcome in chronic total coronary artery occlusion

Background

Chronic total coronary artery occlusions (CTOs) are present in approximately 20–30% of patients undergoing invasive angiography. Despite their prevalence, the optimum management strategy of CTOs remains uncertain. A potential limitation in published trials of CTO revascularisation is their failure to incorporate systematic assessment of ischaemia/viability in informing revascularisation decisions.

Aim

We sought to determine the prognostic utility of ischaemia/viability assessment by cardiovascular magnetic resonance (CMR) in a large, contemporaneous, real-world CTO population.

Methods

We retrospectively studied consecutive adult patients with≥1angiographically identified CTO who were referred for clinical CMR imaging during a consecutive 8-year period in our centre (2010–2018). Multi-parametric CMR comprised functional assessment, adenosine-stress perfusion and scar imaging. For perfusion assessment, images were analysed qualitatively with a concurrent examination of scar images. Myocardial segments were assigned to CTO or non-CTO territories according to standard criteria, taking into account coronary dominance. Significant ischaemia was defined as ≥10% and/or ≥2 contiguous myocardial segments with hibernation. Angiographic collateral flow to the CTO territory was graded using the Rentrop classification and the Collateral Connection (CC) Score. Significant CAD in non-CTO vessels was defined angiographically as ≥50% stenosis in any epicardial coronary artery/branch with diameter ≥2mm. The composite clinical endpoint comprised all-cause mortality, myocardial infarction and heart failure hospitalisation.

Results

From a total of 27,201 invasive angiograms performed during the study period, 389 patients were diagnosed with CTO and underwent CMR imaging (mean age 65.0±11.0 years, 84% male). CTO was present most frequently in the right coronary artery (59% of subjects, 229/389), with left circumflex (LCx) artery involvement in 29% (112/389) and left anterior descending (LAD) artery in 29% (111/389). Collaterals with CC grade ≥2 were identified in 186 subjects (48%), and Rentrop score ≥2 in 300 (77%). Significant ischaemia was present in 61% of patients, and infarction in 71% (median infarction 8.6% [interquartile range (IQR) 4.5–14.1]. With a median follow-up time of 3.30 years [IQR 0.04–8.64], 65 (17%) met the composite endpoint. On multivariate analysis, neither significant ischaemia nor infarction was associated with the composite endpoint. However, non-CTO territory ischaemia was independently predictive of adverse outcome (hazard ratio 1.93; 95% CI 1.16–3.21; p=0.0113).

Conclusion

CTO-territory ischaemia and infarction are not predictive of adverse clinical outcome, challenging the assertion that CTO revascularisation may be guided by ischaemia assessment. The finding that non-CTO territory ischaemia is associated with adverse cardiovascular events warrants further investigation.

Kaplan-Meier curves_CTO

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): British Heart Foundation

Male gender and chronic obstructive pulmonary disease predict a poor clinical response in patients undergoing cardiac resynchronisation therapy

AIMS

Current guidelines advocate cardiac resynchronisation therapy (CRT) in patients with class III/IV New York Heart Association (NYHA) heart failure, depressed left ventricular function and a broad QRS. However, a significant proportion of patients do not derive any benefit from CRT. The aim of this study was to identify clinical, electrocardiographic and echocardiographic predictors of response to CRT.

METHODS

A retrospective analysis of patients undergoing CRT in our institution was performed. A favourable clinical response to CRT was defined as an improvement in NYHA Heart failure class of ≥ 1 and lack of hospitalisation with heart failure. Comparisons were made between responders and non-responders in terms of baseline characteristics and potential predictors of CRT response (QRS width, presence of left bundle branch block, atrial fibrillation, evidence of mechanical dyssynchrony on echocardiography and LV lead position).

RESULTS

A total of 164 patients had full follow-up data. The mean follow-up was 293 days. Of patients undergoing CRT, 90 (58.9%) had a favourable clinical response to CRT. Predictors of a lack of clinical response to CRT were male gender (p = 0.012) and chronic obstructive pulmonary disease (COPD) (0.008). Pre-implant echocardiographic dyssynchrony assessment appeared not to predict response to CRT (p = 0.87); however, there was a trend towards a positive response in those patients with significant dyssynchrony (p = 0.09) defined as interventricular delay > 40 ms or maximal LV delay of > 80 ms.

CONCLUSION

Male gender and coexisting COPD were shown to be independent predictors of non-response to CRT in this cohort of patients fulfilling current criteria for CRT.