Influence of novel risk markers on defibrillator implantation in hypertrophic cardiomyopathy

Background/Introduction

To guide implantable defibrillator (ICD) use in hypertrophic cardiomyopathy (HCM), European Society of Cardiology (ESC) guidelines recommend using individualised sudden death (SCD) risk scores based on quantitative clinical data. Newly published American guidelines are based on the accumulation of binary risk markers, which include imaging-based novel risk markers (NRMs) that were absent from the development of the ESC's algorithm. These NRMs are ejection fraction <50%, apical aneurysm, and extensive late gadolinium enhancement on cardiac magnetic resonance (CMR) imaging.

Purpose

To assess how NRMs may have altered ICD prescription across ESC-based SCD risk status prior to publication of current American guidance.

Methods

We examined electronic records (2013–2020) of a subset of HCM patients with contemporaneous (within 12 months) CMR and echocardiography data for NRMs, ESC risk status, and ICD prescription. Differences in categorical data were assessed by Fisher's exact test.

Results

We studied 334 HCM patients (74% male; age: 58±14 years), of whom 83 (25%) were referred for ICD. ESC risk status was considered low, medium (4–6% 5-year SCD risk), or high in 264, 26, and 20 patients, for whom ICDs were recommended in 40 (15%), 20 (77%), and 18 (90%) patients, respectively. In patients with low SCD risk status, rate of ICD recommendation was significantly higher when ≥1 NRMs were present (34/126 – 27% vs. 0 NRMs: 6/138 – 4%; p<0.0001). NRMs did not appear to influence ICD recommendation in patients with medium (≥1 NRMs: 14/17 – 82% vs. 0 NRMs: 6/9 – 67%; p=0.6) or high (≥1 NRMs: 14/15 – 93% vs. 0 NRMs: 4/5 – 80%; p=0.4) SCD risk status (Figure 1). NRMs were less frequent in low risk patients than in high risk patients (126/264 – 48% vs. 15/20 – 75%; p<0.05), suggesting interaction between ESC status and NRMs (Figure 2).

Conclusion

NRMs have disproportionate influence on ICD prescription in low ESC risk HCM patients. However, NRMs are not independent of ESC risk status, suggesting iterative development of the ESC's algorithmic approach will be the most effective way of predicting SCD.

Funding Acknowledgement

Type of funding sources: None.

Cardiac magnetic resonance imaging predictors of ventricular arrhythmia in mid-cavity obstructive hypertrophic cardiomyopathy

Background/Introduction

Left ventricular (LV) mid-cavity obstruction (LVMCO) in hypertrophic cardiomyopathy (HCM) is an uncommon phenotypic feature predisposed to the formation of myocardial fibrosis and apical aneurysms (LVAA). These features may be independently proarrhythmic, and LVAA is considered a class 2a indication for implantable cardioverter defibrillator (ICD) in current US, but not European guidelines for the primary prevention of sudden cardiac death (SCD). Cardiac magnetic resonance (CMR) imaging is the preferred modality for detecting these and other phenotypic features critical to SCD risk assessment.

Purpose

To assess the ability of CMR imaging parameters to predict occurrence of non-sustained ventricular tachycardia (NSVT) in HCM patients with Doppler-derived evidence of LVMCO.

Methods

Multi-modality imaging records were retrospectively assessed to identify HCM patients with Doppler-LVMCO and CMR scans. CMR images were assessed by an investigator blinded to clinical status. Late gadolinium enhancement (LGE) was quantified using the full-width, half-maximum technique. CMR imaging parameters were assessed for predictive ability using Cox proportional hazards during univariate and multivariate analyses, accounting for time to event (NSVT or censorship of follow-up).

Results

The study cohort included 58 patients (57±11 years, 74% male) with a median follow-up of 6.2 (IQR 4.3) years. Mean mid-cavity gradient was 33±23 mmHg. NSVT was detected in 27/58 (47%) patients, was 4 beats or longer in 23/27 (85%) and was monomorphic in 21/27 (77%).

On univariate analysis, predictors of NSVT during follow-up include LV mass index (HR 1.02, 95% CI 1.00–1.04, p=0.03), LGE in grams (HR 1.04, 95% CI 1.01–1.06, p=0.005), and LVAA (HR 2.57, 95% CI 1.14–5.79, p=0.023). After multivariate adjustment (Table 2), none were significantly associated.

Conclusions

In LVMCO, magnitude of LV hypertrophy, extent of LGE and the presence of an apical aneurysm may not be independent predictors of ventricular arrhythmias. SCD algorithms based on qualitative assessments of these features may overestimate risk.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): National Institute of Health Research (NIHR)

Multi-modality imaging in hypertrophic cardiomyopathy: intermodal discrepancies in key prognostic parameters

Background/Introduction

Multi-modality imaging is crucial for confirming diagnosis and assessing prognosis in patients with hypertrophic cardiomyopathy (HCM). However, inter-modality discrepancies in key parameters are commonly reported.

Purpose

To assess real-world inter-modal reporting discrepancies between transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) imaging in the measurement of four key parameters in HCM patients.

Methods

Consecutive HCM patients with TTE and CMR performed within 6 months of each other at a tertiary centre were retrospectively assessed for reported maximum wall thickness (MWT), left atrial diameter (LAd), left ventricular ejection fraction (LVEF) and presence of left ventricular apical aneurysm (LVAA). The CMR report was considered gold standard. Data are reported as mean ± standard deviation (SD) or median and interquartile range (IQR) as appropriate.

Results

353 consecutive HCM patients (72% male, median age 60.9 years, IQR 49.8–71.6 years) with TTE and CMR within 6 months (median difference 1.7 months, IQR 1.1–3.4 months) were assessed between 4th January 2018 and 9th April 2019. Of 284 patients with paired MWT data, median difference was 0.0 mm (IQR −1.0 to 3.0 mm, p=0.02), likely representing a difference in distributions of MWT. TTE both over and underestimated MWT (in 36% and 46% cases respectively).

Of the 94 patients with paired LAd data, mean difference was 0.4±5.7 mm (95% CI −0.8010 to 1.546, p=0.5).

N=320 patients with paired LVEF data (after excluding patients with atrial fibrillation (n=20)). Median difference in LVEF was 12% (IQR 5–19% p<0.0001). TTE underestimated LVEF in 88% of cases. CMR and TTE both identified 14 (5%) patients as having LVEF <50%. There were however 8 cases of disagreement in classification of LVEF <50%, due to over (n=4) or underestimation (n=4) by TTE.

LVAA was accurately identified by TTE in only 9/30 (30%) of those patients with demonstrable LVAA by CMR (p=0.0008). TTE evidence of a discreet apical chamber (paradoxical jet on spectral or colour Doppler) was present in 16/21 (76%) cases where TTE failed to overtly identify LVAA. However, apical or mid-cavity obliteration was reported in 15/21 (71%) cases where TTE failed to identify LVAA.

Conclusion(s)

Echocardiography and CMR measurements are often used interchangeably in clinical practice but inter-modality discrepancies can affect diagnosis and sudden cardiac death (SCD) risk assessment. This is particularly important for binary risk factors such as LVEF<50% or LVAA which are considered major SCD risk factors in the latest American Heart Association guidelines. 25 (7%) patients in our cohort had major risk factors identified by CMR that were not identified on TTE. CMR is an important, recommended tool where TTE imaging is suboptimal, but attention to more subtle elements of abnormal intracavity blood flow may be able to increase LVAA detection during TTE.

Funding Acknowledgement

Type of funding sources: None.

1174Characterization of disease hot-phases using 18f-fluorodeoxyglucose positron emission tomography in arrhythmogenic cardiomyopathy caused by desmosomal gene mutations

Introduction

Mutations in the genes encoding for desmosomal proteins are associated with Arrhythmogenic Cardiomyopathy (AC), a condition in which “hot-phases” reminiscent of myocarditis can develop and which represent active disease progression. Detection of hot-phase disease can offer novel treatment opportunities.

Purpose

We used 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to determine the prevalence of myocardial inflammation during clinical hot phases in AC.

Methods

Nineteen (12 male; age 38±14 years) symptomatic desmosomal gene mutation carriers (PKP-2, n=6; DSG-2, n=3; DSC-2, n=1; DSP, n=9) underwent FDG-PET and cardiac magnetic resonance (CMR). AC was diagnosed according to the 2010 Task Force diagnostic criteria. The indication for FDG-PET was presentation with clinically suspected myocarditis in 10 (53%), increase in arrhythmic burden in 4 (21%), deteriorating left ventricular (LV) systolic function in 3 (16%) and as part of a diagnostic workup in 2. We compared regional distribution of FDG uptake and late gadolinium enhancement (LGE) on CMR using a standard 16-segment model. Concordance between the two tests was defined as >50% of segment overlap and partial concordance as 1- 50%. Cohen's κ was used to evaluate the inter-method agreement between FDG and LGE.

Results

Nine (47%) patients (5 male) had LV heterogeneous FDG uptake. RV uptake was never observed. Eight of these cases had a definite and 1 had a borderline diagnosis of AC. FDG uptake associated with the presence of DSP gene mutations (7/9, 78% vs 2/10, 20%, p=0.02) and older age (44±12 vs 33±15 years, p=0.05). Concurrent CMR study was available in 15 patients, including all nine with a positive FDG-PET. RV LGE was present in 6 (40%) and LV LGE in 14 cases (93%). All nine (100%) patients with FDG uptake had LV LGE. The commonest segments with FDG-uptake were the basal-anterior, mid-inferolateral and mid-anterolateral (5 cases, 56%), whereas LGE was most commonly present in the mid-anteroseptal (8 cases, 89%) followed by the basal- and mid-inferior segments (6 cases, 67%). Concordance of FDG uptake and LGE was present in 2 cases (22%). There was no concordance in 1 case (11%). Partial concordance was present in 6 (67%). There was poor inter-method topographical agreement between FDG-PET and CMR, κ = 0.04, p=0.64.

Conclusion

Up to 50% of desmosomal gene positive AC patients, and especially those with DSP mutations, and clinical “hot phases” have evidence for myocarditis on FDG-PET. The topographical variation between PET and CMR highlight the underlying pathophysiological stage of disease (inflammation versus scar) and suggest that the imaging modalities provide complementary information on tissue characterisation in AC.

Acknowledgement/Funding

Alexandros Protonotarios is funded by a BHF Clinical Research Training Fellowship no. FS/18/82/34024

T-cell immunity in myocardial inflammation: pathogenic role and therapeutic manipulation

T-cell-mediated immunity has been linked not only to a variety of heart diseases, including classic inflammatory diseases such as myocarditis and post-myocardial infarction (Dressler's) syndrome, but also to conditions without an obvious inflammatory component such as idiopathic dilated cardiomyopathy and hypertensive cardiomyopathy. It has been recently proposed that in all these conditions, the heart becomes the focus of T-cell-mediated autoimmune inflammation following ischaemic or infectious injury. For example, in acute myocarditis, an inflammatory disease of heart muscle, T-cell responses are thought to arise as a consequence of a viral infection. In a number of patients, persistent T-cell-mediated responses in acute viral myocarditis can lead to autoimmunity and chronic cardiac inflammation resulting in dilated cardiomyopathy. In spite of the major progress made in understanding the mechanisms of pathogenic T-cell responses, effective and safe therapeutic targeting of the immune system in chronic inflammatory diseases of the heart has not yet been developed due to the lack of specific diagnostic and prognostic biomarkers at an early stage. This has also prevented the identification of targets for patient-tailored immunomodulatory therapies that are both disease- and organ-selective. In this review, we discuss current knowledge of the development and functional characteristics of pathogenic T-cell-mediated immune responses in the heart, and, in particular, in myocarditis, as well as recent advances in experimental models which have the potential to translate into heart-selective immunomodulation.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

Myocardial bridging does not predict sudden death in children with hypertrophic cardiomyopathy but is associated with more severe cardiac disease

OBJECTIVES

We sought to examine the association between systolic compression of sections of epicardial coronary vessels (myocardial bridging) with myocardial perfusion abnormalities and clinical outcome in children with hypertrophic cardiomyopathy (HCM).

BACKGROUND

It has recently been suggested that myocardial bridging is an important cause of myocardial ischemia and sudden death in children with HCM.

METHODS

Angiograms from 57 children with HCM were reviewed for the presence of bridging (50% or more maximum systolic arterial compression). QT interval indices, echocardiographic and cardiac catheterization findings, treadmill exercise tests, exercise thallium scintigraphy, Holter monitoring and electrophysiologic study findings were compared in children with and without bridging. The findings were also related to the presence or absence of compression of septal branches of the left anterior descending artery (LAD).

RESULTS

Bridging was present in 23 (40%) of the children. Multiple coronary arteries were involved in four children. Bridging involved the LAD in 16 of 28 (57%) affected vessels. Myocardial perfusion abnormalities were present in 14 of 30 (47%) children without bridging and in 17 of 22 (94%) children with bridging, p = 0.002. However, bridging was associated with more severe septal hypertrophy (19+/-8 mm vs. 28+/-8 mm, p < 0.001), a higher septum:posterior wall thickness ratio (2.7+/-1.2 vs. 1.8+/-0.9, p < 0.001), and higher left ventricle (LV) outflow gradient (45+/-37 mm Hg vs. 16+/-28 mm Hg, p = 0.002). Compression of septal LAD branches was present in 37 (65%) of the children and was significantly associated with bridging, severity of LV hypertrophy and outflow obstruction. Multivariate analysis demonstrated that LV septal thickness and septal branch compression, and not bridging, were independent predictors of thallium perfusion abnormalities. There was a 90% power at 5% significance to detect an effect of bridging on thallium abnormalities at an odds ratio of 3. Bridging was also not associated with significantly greater symptoms, increased QT and QTc intervals and QTc dispersion, ventricular tachycardia on Holter or induced at EP study, or a worse prognosis.

CONCLUSIONS

Bridging and compression of septal branches of the LAD are common in HCM children and are related to magnitude of LV hypertrophy. Left ventricular hypertrophy and compression of intramyocardial branches of the epicardial coronary arteries may contribute to myocardial perfusion abnormalities. Our findings suggest that bridging does not result in myocardial ischemia and may not cause arrhythmias or sudden death in HCM children.