Impaired repolarization parameters may predict fatal ventricular arrhythmias in patients with hypertrophic cardiomyopathy (from the CILICIA Registry)

Mechanisms of ischaemia-induced arrhythmias in hypertrophic cardiomyopathy: a large-scale computational study

AIMS

Lethal arrhythmias in hypertrophic cardiomyopathy (HCM) are widely attributed to myocardial ischaemia and fibrosis. How these factors modulate arrhythmic risk remains largely unknown, especially as invasive mapping protocols are not routinely used in these patients. By leveraging multiscale digital twin technologies, we aim to investigate ischaemic mechanisms of increased arrhythmic risk in HCM.

METHODS AND RESULTS

Computational models of human HCM cardiomyocytes, tissue, and ventricles were used to simulate outcomes of Phase 1A acute myocardial ischaemia. Cellular response predictions were validated with patch-clamp studies of human HCM cardiomyocytes (n = 12 cells, N = 5 patients). Ventricular simulations were informed by typical distributions of subendocardial/transmural ischaemia as analysed in perfusion scans (N = 28 patients). S1-S2 pacing protocols were used to quantify arrhythmic risk for scenarios in which regions of septal obstructive hypertrophy were affected by (i) ischaemia, (ii) ischaemia and impaired repolarization, and (iii) ischaemia, impaired repolarization, and diffuse fibrosis. HCM cardiomyocytes exhibited enhanced action potential and abnormal effective refractory period shortening to ischaemic insults. Analysis of ∼75 000 re-entry induction cases revealed that the abnormal HCM cellular response enabled establishment of arrhythmia at milder ischaemia than otherwise possible in healthy myocardium, due to larger refractoriness gradients that promoted conduction block. Arrhythmias were more easily sustained in transmural than subendocardial ischaemia. Mechanisms of ischaemia-fibrosis interaction were strongly electrophysiology dependent. Fibrosis enabled asymmetric re-entry patterns and break-up into sustained ventricular tachycardia.

CONCLUSION

HCM ventricles exhibited an increased risk to non-sustained and sustained re-entry, largely dominated by an impaired cellular response and deleterious interactions with the diffuse fibrotic substrate.

The predictive value of electrocardiographic polarization parameters on appropriate ICD shock in primary prevention heart failure patients

OBJECT

The effect of frontal QRS-T angle, Tp-e and Tp-e/QT ratio on cardiac events have been shown in many studies. In this study, we aimed to determine the prognostic value of frontal QRS-T angle, TPe and Tp-e/QT ratio on ICD shock in patients who had ICD (Implantable Cardioverter Defibrillator) implanted due to heart failure with reduced ejection fraction (HFrEF).

MATERIAL AND METHOD

158 patients with HFrEF who had previous ICD implantation were retrospectively analyzed. 27 patients were found to have an appropriate shock. Frontal QRS-T angle, Tp-e interval, Tp-e/QT ratio were calculated by evaluating the basal ECG records of the patients. Comparisons of these arrhythmogenic predictors were made in patients with and without ICD shock at follow-up.

RESULT

When 158 patients with previous ICD implantation were analyzed in two groups with and without ICD shock, the number of patients with frontal QRS-T angle >120°, Tp-e interval > 105 ms, Tp-e/QT > 0.2 in the shock group (n: 27) was found to be high with a different significance (p:<0.01, p:<0.01, p:<0.01). There was no significant difference between the two groups regarding other ECG parameters such as QRS duration, QT interval, PR interval, fragmented QRS and positive T wave. In addition, more amiodarone use was observed in the shock group, and more hyperlipidemia cases were observed in the non-shocked group (p:0.01; p:<0.01).

CONCLUSION

Increased frontal QRS-T angle, Tp-e interval, and Tp-e/QT ratio are arrhythmogenic parameters and predict appropriate ICD shock.

Updated risk assessments for sudden cardiac death in hypertrophic cardiomyopathy patients with implantable cardioverter-defibrillator

Hypertrophic cardiomyopathy (HCM) is a genetic disease associated with a risk of malignant ventricular tachyarrhythmias and sudden cardiac death (SCD). Assessment of the SCD risk is crucial for its clinical management, and there has been considerable interest in developing risk stratification strategies. An implantable cardioverter-defibrillator (ICD) is a life-saving treatment for patients with HCM who are at a high-risk of ventricular tachyarrhythmias and SCD. However, a substantial number of ICD recipients experience adverse effects arising from inappropriate device therapy and implant-related complications. This has led to numerous investigations of the risk of SCD and the indications for ICD implantation. American guidelines were recently updated to include new risk markers, including left ventricular systolic dysfunction, apical aneurysm, and extensive late gadolinium enhancement, while European guidelines recommend individualized estimated 5-year SCD risk assessment models. Studies evaluating other risk factors for SCD in patients with HCM have also been published. Drawing on recent guidelines and publications on clinical risk factors, we focus this review on updated risk assessments for SCD with ICD therapy in patients with HCM.

Electrocardiographic Parameters Associated with Adverse Outcomes in Children with Cardiomyopathies

Cardiomyopathies have a low prevalence in children and thus may lead to malignant ventricular arrhythmias or the progression of heart failure, resulting in death. In adults, the QRS-T angle derived from ECG has been associated with adverse outcomes in patients with hypertrophic and dilated cardiomyopathies. We aimed to assess the electrocardiographic parameters, including QRS-T angle, associated with adverse cardiac events in children with cardiomyopathies. Forty-two children with cardiomyopathies were included in this study: 19 with dilated cardiomyopathy, 17 with hypertrophic cardiomyopathy, and 6 with left ventricular non-compaction. Additionally, 19 control subjects were recruited. In terms of ECG parameters, the QRS-T angle was significantly greater among patients with adverse outcomes compared to patients without the end points of the study (133° vs. 65°, p < 0.001). On Kaplan−Meier survival curves, QRS-T angle > 120°, increased serum concentrations of NT-proBNP and troponin I levels as well as greater NYHA or Ross scale were associated with the greatest risk of unfavorable outcome. The QRS-T angle appears to be a valuable component of 12-lead ECG interpretation, and might be helpful in outlining patients with the greatest cardiovascular risk. Additionally, serum biomarkers such as NT-proBNP (p = 0.003) and troponin (p < 0.001) are useful in outlining patients with the worst survival.

Relationship between impaired repolarization parameters and poor cardiovascular clinical outcomes in patients with potentially serious coronary artery anomalies

BACKGROUND

Congenital coronary artery anomalies (CCAAs) have the potential for life-threatening complications, including malignant ventricular arrhythmias and sudden cardiac death (SCD). In this study, we aimed to evaluate the relationship between impaired repolarization parameters and poor cardiovascular clinical outcomes in patients with potentially serious CCAAs.

METHODS

This retrospective study included 85 potentially serious CCAA patients (mean age: 54.7 ± 13.6 years; male:44) who were diagnosed with conventional and coronary computed tomography angiography (CCTA). All patients underwent transthoracic echocardiography and 12-lead surface electrocardiography. Cardiac events were defined as sustained ventricular tachycardia or fibrillation, syncope, cardiac arrest and SCD.

RESULTS

The presence of interarterial course (IAC) was confirmed by CCTA in 37 (43.5%) patients. During a median follow-up time of 24 (18-50) months, a total of 11 (12.9%) patients experienced cardiac events. The presence of IAC was significantly more frequent and Tp-e interval, Tp-e/QTc ratio and frontal QRS/T angle (fQRSTa) were significantly greater in patients with poor clinical outcomes. Moreover, the presence of IAC, high Tp-e/QTc ratio and high fQRSTa were found to be independent predictors of poor clinical outcomes and decreased long-term cardiac event-free survival in these patients. A net reclassification index was +1.0 for the Tp-e/QTc ratio and +1.3 for fQRSTa which were confirmable for additional predictability of these repolarization abnormalities.

CONCLUSION

Impaired repolarization parameters, including wider fQRSTa, prolonged Tp-e interval, and increased Tp-e/QTc ratio, and IAC may be associated with poor cardiovascular clinical outcomes in potentially serious CCAA patients.