Sudden cardiac death: The role of imaging

Post-Ablation cardiac Magnetic resonance to assess Ventricular Tachycardia recurrence (PAM-VT study)

AIMS

Conducting channels (CCs) detected by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) are related to ventricular tachycardia (VT). The aim of this work was to study the ability of post-ablation LGE-CMR to evaluate ablation lesions.

METHODS AND RESULTS

This is a prospective study of consecutive patients referred for a scar-related VT ablation. LGE-CMR was performed 6-12 months prior to ablation and 3-6 months after ablation. Scar characteristics of pre- and post-ablation LGE-CMR were compared. During the study period (March 2019-April 2021), 61 consecutive patients underwent scar-related VT ablation after LGE-CMR. Overall, 12 patients were excluded (4 had poor-quality LGE-CMR, 2 died before post-ablation LGE-CMR, and 6 underwent post-ablation LGE-CMR 12 months after ablation). Finally, 49 patients (age: 65.5 ± 9.8 years, 97.9% male, left ventricular ejection fraction: 34.8 ± 10.4%, 87.7% ischaemic cardiomyopathy) were included. Post-ablation LGE-CMR showed a decrease in the number (3.34 ± 1.03 vs. 1.6 ± 0.2; P < 0.0001) and mass (8.45 ± 1.3 vs. 3.5 ± 0.6 g; P < 0.001) of CCs. Arrhythmogenic CCs disappeared in 74.4% of patients. Dark core was detected in 75.5% of patients, and its presence was not related to CC reduction (52.2 ± 7.4% vs. 40.8 ± 10.6%, P = 0.57). VT recurrence after one year follow-up was 16.3%. The presence of two or more channels in the post-ablation LGE-CMR was a predictor of VT recurrence (31.82% vs. 0%, P = 0.0038) with a sensibility of 100% and specificity of 61% (area under the curve 0.82). In the same line, a reduction of CCs < 55% had sensibility of 100% and specificity of 61% (area under the curve 0.83) to predict VT recurrence.

CONCLUSION

Post-ablation LGE-CMR is feasible, and a reduction in the number of CCs is related with lower risk of VT recurrence. The dark core was not present in all patients. A decrease in VT substrate was also observed in patients without a dark core area in the post-ablation LGE-CMR.

Global Longitudinal Strain May Be the One that Appropriately Identifies Candidates of ICD Implantation

Hypertrophic cardiomyopathy (HCM) significantly contributes to an elevated risk of sudden cardiac death. Primary prevention is implemented by using an implantable cardioverter defibrillator (ICD). However, all of the HCM patients do not really need ICD therapy. Providing a superior index for ICD indication compared with the current indices like ejection fraction is essential to differentiate high-risk patients efficiently. The present study assessed the potential of global longitudinal strain (GLS) for the differentiation of HCM patients based on their need for ICD shocks. Patients with HCM were considered in four defined centers between March and June 2021. Those with previous ICD implantation or current candidates for ICD therapy were included in the study. Participants were subjected to speckle-tracking echocardiography, and GLS as well as some other echocardiographic parameters were recorded. Afterwards, data from implanted ICDs were extracted. Patients who received ICD shocks (appropriate) due to ventricular tachycardia (VT)/ventricular fibrillation (VF) were categorized in group A. The remaining patients were constituted group B who received inappropriate shocks, i.e., other than VT/VF. Overall, 34 patients were found eligible to participate with a mean age of 62 ± 16.1 years including 64.7% of males. Among a variety of echocardiographic parameters, GLS was the sole one that was significantly higher in group A compared with that in group B. Our findings revealed that only GLS could predict fatal arrhythmias. To substantiate, the odds of VT were raised by 43% with a single increase in GLS unit. GLS showed the highest accuracy for ICD indication among HCM patients and, therefore, could be a solid and early criterion to predict the incidence of life-threatening arrhythmias. In this regard, identifying appropriate HCM patients with respect to their need for ICD therapy is feasible.

Diagnosis and management of patients with left ventricular hypertrophy: Role of multimodality cardiac imaging. A scientific statement of the Heart Failure Association of the European Society of Cardiology

Left ventricular (LV) hypertrophy consists in an increased LV wall thickness. LV hypertrophy can be either secondary, in response to pressure or volume overload, or primary, i.e. not explained solely by abnormal loading conditions. Primary LV hypertrophy may be due to gene mutations or to the deposition or storage of abnormal substances in the extracellular spaces or within the cardiomyocytes (more appropriately defined as pseudohypertrophy). LV hypertrophy is often a precursor to subsequent development of heart failure. Cardiovascular imaging plays a key role in the assessment of LV hypertrophy. Echocardiography, the first-line imaging technique, allows a comprehensive assessment of LV systolic and diastolic function. Cardiovascular magnetic resonance provides added value as it measures accurately LV and right ventricular volumes and mass and characterizes myocardial tissue properties, which may provide important clues to the final diagnosis. Additionally, scintigraphy with bone tracers is included in the diagnostic algorithm of cardiac amyloidosis. Once the diagnosis is established, imaging findings may help predict future disease evolution and inform therapy and follow-up. This consensus document by the Heart Failure Association of the European Society of Cardiology provides an overview of the role of different cardiac imaging techniques for the differential diagnosis and management of patients with LV hypertrophy.

Beyond Ejection Fraction: Novel Clinical Approaches Towards Sudden Cardiac Death Risk Stratification in Patients with Dilated Cardiomyopathy

Implantable Cardioverter-Defibrillator (ICD) therapy is indicated for patients at risk for sudden cardiac death due to ventricular tachyarrhythmia. The most commonly used risk stratification algorithms use Left Ventricular Ejection Fraction (LVEF) to determine which patients qualify for ICD therapy, even though LVEF is a better marker of total mortality than ventricular tachyarrhythmias mortality. This review evaluates imaging tools and novel biomarkers proposed for better risk stratifying arrhythmic substrate, thereby identifying optimal ICD therapy candidates.

Cardiac magnetic resonance to predict recurrences after ventricular tachycardia ablation: septal involvement, transmural channels, and left ventricular mass

AIMS

Ventricular tachycardia (VT) substrate-based ablation has an increasing role in patients with structural heart disease-related VT. VT is linked to re-entry in relation to myocardial scarring with areas of conduction block (core scar) and areas of slow conduction [border zone (BZ)]. VT substrate can be analysed by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). Our study aims to analyse the role of LGE-CMR in identifying predictors of VT recurrence after ablation.

METHODS AND RESULTS

We analysed 110 consecutive patients who underwent VT ablation from 2013 to 2018. All patients underwent a preprocedural LGE-CMR, and in 94 patients (85.5%), the CMR was used to aid the ablation. All LGE-CMR images were semi-automatically processed using dedicated software to detect scarring and conducting channels. After a median follow-up of 2.7 ± 1.6 years, the overall VT recurrence was 41.8% with an implantable cardioverter-defibrillator shock reduction from 43.6% to 28.2% before and after ablation, respectively. The amount of BZ (26.6 ± 13.9 vs. 19.6 ± 9.7 g, P = 0.012), the total amount of scarring (37.1 ± 18.2 vs. 29 ± 16.3 g, P = 0,033), and left ventricular (LV) mass (168.3 ± 53.3 vs. 152.3 ± 46.4 g, P < 0.001) were associated with VT recurrence. LGE septal distribution [62.5% vs. 37.8%; hazard ratio (HR) 1.67 (1.02-3.93), P = 0.044], channels with transmural path [66.7% vs. 31.4%, HR 3.25 (1.70-6.23), P < 0.001], and midmural channels [54.3% vs. 27.6%, HR 2.49 (1.21-5.13), P = 0.013] were related with VT recurrence. Multivariate analysis showed that the presence of septal LGE [HR 3.67 (1.60-8.38), P = 0.002], transmural channels [HR 2.32 (1.15-4.72), P = 0.019], and LV mass [HR 1.01 (1.005-1.019), P = 0.002] were independent predictors of VT recurrence.

CONCLUSION

Pre-procedural LGE-CMR is a helpful and feasible technique to identify patients with high risk of VT recurrence after ablation. LV mass, septal LGE distribution, and transmural channels were predictive factors of post-ablation VT recurrence.

Cardiac Sympathetic Innervation Imaging with PET Radiotracers

PURPOSE OF REVIEW

The present article reviews the pathophysiology of cardiac sympathetic denervation, the principles of positron emission tomography (PET) imaging of the sympathetic innervation of the heart and its potential clinical role, based on current and expected future evidence.

RECENT FINDINGS

Imaging of cardiac sympathetic denervation can be performed with radiolabeled noradrenaline analogues, e.g., ¹¹C-hydroxyephedrine. A greater burden of sympathetic denervation carries prognostic significance, e.g., in patients with ischemic cardiomyopathy and a left ventricular ejection fraction ≤ 35%, who are more likely to experience sudden cardiac death. Abnormalities of sympathetic cardiac innervation have been demonstrated in hypertrophic, dilated, and arrhythmic right ventricular cardiomyopathies, and may be helpful in better phenotyping patients who will benefit from device therapy, e.g., cardiac resynchronization and implantable cardioverter-defibrillator implantation. The results of future trials, e.g., the Prediction of Arrhythmic Events with Positron Emission Tomography (PAREPET) II study, are awaited to inform on the role of PET cardiac sympathetic imaging in the selection of device therapy. PET cardiac sympathetic innervation imaging allows visualization and quantification of autonomic denervation secondary to various cardiac diseases, and has significant potential to influence clinical decision-making, e.g., the titration of pharmacotherapy and more directed selection of candidates for device implantation.

Global longitudinal strain for prediction of ventricular arrhythmia in patients with heart failure

AIMS

Currently, the ejection fraction [left ventricular ejection fraction (LVEF)] is the main criterion used for implanting implantable cardioverter defibrillators (ICDs) for primary prevention. However, many of ICD receivers would not have an event and do not have any gains from the device. Consequently, improving the discrimination strategies is needed. Here, we aimed at assessing the role of global longitudinal strain (GLS) for such purpose.

METHODS AND RESULTS

Seventy ischaemic or dilated cardiomyopathy cases characterized by LVEF ≤ 40% with a previously implanted ICD were enrolled. LVEF and GLS amounts were evaluated using 3D echocardiography. The occurrence of ventricular arrhythmias was checked by analysing the ICD history. Mean follow-up period of patients was 1.8 ± 0.6 years. There was a significant difference in the amount of GLS in arrhythmic cases compared with non-arrhythmic ones (-6.97 ± 3.06 vs -11.82 ± 4.25; P < 0.001). This difference was found in both ischaemic and dilated cardiomyopathy groups. A GLS below -10 cm/s could predict the occurrence of a ventricular event by 90% specificity and 72.2% sensitivity (area under the curve = 0.84, P < 0.001). While 27.39 (69.2%) patients with GLS below -10 cm/s had a ventricular event, only 3.31 (9.6%) of the patients with GLS above -10 had an event) P < 0.001). Those patients with a GLS ≥ 17 cm/s never experienced a ventricular arrhythmia.

CONCLUSIONS

Global longitudinal strain is a more accurate predictor of ventricular arrhythmias in patients with reduced LVEF. Whether it may help in selecting more appropriate patients for ICD implantation or not should be evaluated within a randomized trial in the future.

Echocardiographic Epicardial Adipose Tissue Thickness for Risk Stratification of Patients With Heart Failure

Background and Aims

Epicardial adipose tissue (EAT) has been shown to be involved in the pathogenesis and progression of heart failure (HF). In this study we aimed to explore the predictive value of echocardiographic EAT thickness on prognosis of a selected population of HF patients.

Methods

The patient population included n. 69 consecutive patients with systolic HF referred to implantable cardioverter defibrillator (ICD) implantation for primary or secondary prevention. At the time of enrolment, echocardiographic EAT thickness was assessed in all patients along with demographic and clinical data. The study had a median follow-up time of 49.8 months. We assessed the prognostic predictive value of EAT thickness on a composite clinical and arrhythmic outcome including HF related deaths, new hospital admissions for HF worsening, and atrial and life threatening ventricular arrhythmic events. Clinical and arrhythmic outcomes were also evaluated separately.

Results

At univariate analysis, EAT thickness significantly predicted all the three outcomes considered. Of interest, at multivariate analysis, after adjusting for known risk factor, EAT remained significantly associated to the composite [HR 1.18 (1.09–1.28); p < 0.001], arrhythmic [HR 1.14 (1.03–1.25); p = 0.008], and clinical [HR 1.14 (1.03–1.27); p = 0.010] outcomes.

Conclusion

Echocardiographic assessment of EAT can predict outcome of HF patients and it is significantly associated with both arrhythmic and clinical events. These preliminary findings pave the way for future and larger studies aimed to definitively recognize the prognostic value of this novel risk marker in HF.

Determination of the theoretical personalized optimum chest compression point using anteroposterior chest radiography

Objective

There is a traditional assumption that to maximize stroke volume, the point beneath which the left ventricle (LV) is at its maximum diameter (P_max.LV) should be compressed. Thus, we aimed to derive and validate rules to estimate P_max.LV using anteroposterior chest radiography (chest_AP), which is performed for critically ill patients urgently needing determination of their personalized P_max.LV.

Methods

A retrospective, cross-sectional study was performed with non-cardiac arrest adults who underwent chest_AP within 1 hour of computed tomography (derivation:validation=3:2). On chest_AP, we defined cardiac diameter (CD), distance from right cardiac border to midline (RB), and cardiac height (CH) from the carina to the uppermost point of left hemi-diaphragm. Setting point zero (0, 0) at the midpoint of the xiphisternal joint and designating leftward and upward directions as positive on x- and y-axes, we located P_max.LV (x_max.LV, y_max.LV). The coefficients of the following mathematically inferred rules were sought: x_max.LV=α₀*CD-RB; y_max.LV=β₀*CH+γ₀ (α₀: mean of [x_max.LV+RB]/CD; β₀, γ₀: representative coefficient and constant of linear regression model, respectively).

Results

Among 360 cases (52.0±18.3 years, 102 females), we derived: x_max.LV=0.643*CD-RB and y_max.LV=55-0.390*CH. This estimated P_max.LV (19±11 mm) was as close as the averaged P_max.LV (19±11 mm, P=0.13) and closer than the three equidistant points representing the current guidelines (67±13, 56±10, and 77±17 mm; all P<0.001) to the reference identified on computed tomography. Thus, our findings were validated.

Conclusion

Personalized P_max.LV can be estimated using chest_AP. Further studies with actual cardiac arrest victims are needed to verify the safety and effectiveness of the rule.

Imaging for sudden cardiac death risk stratification: Current perspective and future directions

Sudden cardiac death (SCD) accounts for one fifth of global deaths, and occurs when a trigger (e.g. myocardial ischemia, premature ventricular contraction) interacts with an arrhythmic substrate (e.g. myocardial scar, dilated cardiomyopathy). Multimodality imaging (echocardiographic, cardiac magnetic resonance and nuclear techniques) can potentially visualize many predisposing substrates and triggers. Implantable cardioverter-defibrillator (ICD) is the most effective approach to primary prevention of SCD, and current guidelines regarding ICD implantation are based on a left ventricular ejection fraction (LVEF) ≤35%. This practice is limited by a low sensitivity and specificity, and has limited value when applied to different etiologies. In this review, the role of multimodality imaging in SCD risk-stratification and the limitations of an LVEF-based approach, are discussed. Additional randomized, prospective data are eagerly awaited to inform on the role of imaging in SCD risk-stratification, and ongoing/ planned trials are subsequently discussed.

Risk Stratification of Sudden Cardiac Death in Patients with Heart Failure: An update

Heart failure (HF) is a complex clinical syndrome in which structural/functional myocardial abnormalities result in symptoms and signs of hypoperfusion and/or pulmonary or systemic congestion at rest or during exercise. More than 80% of deaths in patients with HF recognize a cardiovascular cause, with most being either sudden cardiac death (SCD) or death caused by progressive pump failure. Risk stratification of SCD in patients with HF and preserved (HFpEF) or reduced ejection fraction (HFrEF) represents a clinical challenge. This review will give an update of current strategies for SCD risk stratification in both HFrEF and HFpEF.

Sudden Cardiac Death Risk Prediction: The Role of Cardiac Magnetic Resonance Imaging

Sudden cardiac death (SCD) accounts for more than 4 million global deaths per year. While it is most commonly caused by coronary artery disease, a final common pathway of ventricular arrhythmias is shared by different etiologies. The most effective primary and secondary prevention strategy is an implantable cardioverter-defibrillator (ICD). The decision to implant an ICD for primary prevention is largely based on a left ventricular ejection fraction ≤ 35%, but this criterion in isolation is neither sensitive nor specific. Novel imaging parameters hold promise to improve ICD candidate selection. Cardiac magnetic resonance (CMR) imaging is a powerful and versatile technique, with the ability to comprehensively assess cardiac structure and function. A range of variables based on CMR techniques (late gadolinium enhancement, T₁ mapping, T₂* relaxometry, deformation imaging) have been associated with ventricular arrhythmias and SCD risk. The role of CMR in the estimation of ventricular arrhythmias and SCD risk in coronary artery disease, nonischemic cardiomyopathies, cardiac transplant, iron-overload cardiomyopathy and valvular heart disease is reviewed in this article. Prospective, randomized trials and standardization of CMR techniques are required before its routine use can be recommended for guiding SCD prevention strategies.