Mode of onset of polymorphic ventricular tachycardia in acute myocardial infarction

Ventricular Arrhythmias in Ischemic Cardiomyopathy-New Avenues for Mechanism-Guided Treatment

Ischemic heart disease is the most common cause of lethal ventricular arrhythmias and sudden cardiac death (SCD). In patients who are at high risk after myocardial infarction, implantable cardioverter defibrillators are the most effective treatment to reduce incidence of SCD and ablation therapy can be effective for ventricular arrhythmias with identifiable culprit lesions. Yet, these approaches are not always successful and come with a considerable cost, while pharmacological management is often poor and ineffective, and occasionally proarrhythmic. Advances in mechanistic insights of arrhythmias and technological innovation have led to improved interventional approaches that are being evaluated clinically, yet pharmacological advancement has remained behind. We review the mechanistic basis for current management and provide a perspective for gaining new insights that centre on the complex tissue architecture of the arrhythmogenic infarct and border zone with surviving cardiac myocytes as the source of triggers and central players in re-entry circuits. Identification of the arrhythmia critical sites and characterisation of the molecular signature unique to these sites can open avenues for targeted therapy and reduce off-target effects that have hampered systemic pharmacotherapy. Such advances are in line with precision medicine and a patient-tailored therapy.

Atrial Fibrillation, Ventricular Arrhythmia, and Left Ventricular Remodeling in the ICU – First Results of the Single- Center RHYTHM-ACC Registry

The aim of this study was to investigate the association between left ventricular remodeling, atrial fibrillation (AF), and the severity of ventricular tachycardia (VT) in patients with ventricular rhythm disturbances admitted in a level 3 facility of acute cardiac care. Material and Methods: The RHYTHM-ACC registry was a single-center observational study, including 150 consecutive patients with sustained or non-sustained ventricular tachycardia (sVT and nsVT, respectively) admitted in an intensive cardiac care unit (ICCU), separated in: group 1 - 29 patients (21.01%) with dilated cardiomyopathy (DCM), and group 2 - 109 patients (78.99%) with normal ventricular performance. We investigated the difference between clinical characteristics of patients with sVT versus those with nsVT in each study group, and the association between AF and different forms of ventricular arrhythmia in 38 (25.33%) patients with AF and 112 (74.66%) patients in sinus rhythm. Results: There were no significant differences between the study groups with respect to type of ventricular arrhythmia: sVT (46.87% vs. 36.44%, p = 0.2), nsVT (43.75% vs. 55.93%, p = 0.2), or ventricular fibrillation (VF) (9.37% vs. 7.62%, p = 0.7). However, patients with DCM presented a significantly higher incidence of AF (43.75% vs. 20.33%, p = 0.01) and bundle branch block (37.5% vs. 11.86%, p = 0.0007). VF occurred more frequently in patients with AF compared to those in sinus rhythm (18.42% vs. 4.46%, p = 0.006). Multivariate analysis identified the co-existence of AF (OR = 4.8, p = 0.01) and the presence of a bundle branch block (BBB) (OR = 3.9, p = 0.03) as the most powerful predictors for the degeneration of VT into VF in patients admitted with sVT or nsVT in an ICCU unit. Conclusions: In patients with any type of VT admitted in an ICCU, the presence of ventricular remodeling is associated with a higher incidence of AF and conduction abnormalities, but not with a more severe pattern of ventricular arrhythmia. At the same time, AF and BBB seem to represent the most powerful predictors for degeneration of VT into VF, independent of the type of VT.

Regional differential expression of TREK-1 at left ventricle in myocardial infarction

BACKGROUND

Altered membrane electrophysiology contributes to arrhythmias after myocardial infarction (MI). TREK-1 channel is essential in various physiological and pathological conditions through its regulation on resting membrane potential and voltage-dependent action potential duration.

OBJECTIVES

The aim of this study was to investigate changes in gene expression and electrophysiology of TREK-1 in the left ventricle in a MI model.

METHODS

Fifty-five rats were divided into 5 groups: sham-operated group, 6 hours, 24 hours, 3 days, and 7 days post MI group (n=11 per group). TREK-1 messenger RNA (mRNA) expression level in the infarct region (IR) and infarct border region (IBR) were quantified by real-time polymerase chain reaction (PCR), and TREK-1 current density at the IBR was recorded with whole-cell patch-clamp technique.

RESULTS

TREK-1 mRNA expression decreased significantly in both endocardial and epicardial cells in the infarct region after MI. Conversely, TREK-1 increased significantly in endocardial and epicardial cells from the IBR (P<0.01). Current density of TREK-1 at IBR increased significantly in both epicardial and endocardial cells after MI (P<0.01).

CONCLUSIONS

TREK-1 demonstrates specific changes in expression and electrophysiological function in left ventricle post MI. These results suggest that TREK-1 may participate in pathophysiologic alteration and electrical remodelling of left ventricular myocardium after MI, which may eventually lead to post-MI ventricular arrhythmias.