Right ventricular outflow tract function in chronic heart failure

Electrical and Structural Insights into Right Ventricular Outflow Tract Arrhythmogenesis

The right ventricular outflow tract (RVOT) is the major origin of ventricular arrhythmias, including premature ventricular contractions, idiopathic ventricular arrhythmias, Brugada syndrome, torsade de pointes, long QT syndrome, and arrhythmogenic right ventricular cardiomyopathy. The RVOT has distinct developmental origins and cellular characteristics and a complex myocardial architecture with high shear wall stress, which may lead to its high vulnerability to arrhythmogenesis. RVOT myocytes are vulnerable to intracellular sodium and calcium overload due to calcium handling protein modulation, enhanced CaMKII activity, ryanodine receptor phosphorylation, and a higher cAMP level activated by predisposing factors or pathological conditions. A reduction in Cx43 and Scn5a expression may lead to electrical uncoupling in RVOT. The purpose of this review is to update the current understanding of the cellular and molecular mechanisms of RVOT arrhythmogenesis.

Forgotten No More-The Role of Right Ventricular Dysfunction in Heart Failure with Reduced Ejection Fraction: An Echocardiographic Perspective

During the last decade, studies have raised awareness of the crucial role that the right ventricle plays in various clinical settings, including diseases primarily linked to the left ventricle. The assessment of right ventricular performance with conventional echocardiography is challenging. Novel echocardiographic techniques improve the functional assessment of the right ventricle and they show good correlation with the gold standard represented by cardiac magnetic resonance. This review summarizes the traditional and innovative echocardiographic techniques used in the functional assessment of the right ventricle, focusing on the role of right ventricular dysfunction in heart failure with reduced ejection fraction and providing a perspective on recent evidence from literature.

Prognostic Value of Tricuspid Annular Plane Systolic Excursion and Right Ventricular Outflow Tract Fractional Shortening in Mechanically Ventilated Septic Patients

OBJECTIVE

The authors aimed to explore whether tricuspid annular plane systolic excursion (TAPSE) and right ventricular outflow fractional shortening (RVOT-FS) were associated with long-term prognosis in mechanically ventilated septic patients.

DESIGN

A prospective observational study.

SETTING

A tertiary hospital intensive care unit (ICU).

PARTICIPANTS

One hundred eighty-one septic patients who were on mechanical ventilation.

INTERVENTIONS

Echocardiography was performed within 24 hours of ICU admission.

MEASUREMENTS AND MAIN RESULTS

Several echocardiographic parameters, including TAPSE and RVOT-FS, as well as prognostic information, were collected. A Cox regression survival analysis showed that TAPSE was independently associated with one-year all-cause mortality (hazard ratio [HR] 0.407, 95% confidence interval [CI]: 0.200-0.827, p = 0.013), but ROVT-FS was not (HR 0.997, 95% CI: 0.970-1.025, p = 0.828). ROC analysis showed that the optimal cutoff value for TAPSE and RVOT-FS to determine one-year mortality was TAPSE <18 mm and RVOT-FS <40%. The one-year mortality in patients with low TAPSE (n = 88) and in patients with both low TAPSE and low RVOT-FS (n = 60) was 45.5% and 48.3%, respectively; p = 0.724. In a multivariate analysis, RVOT-FS did not add significant prognostic information to that provided by TAPSE <18 mm (p = 0.197).

CONCLUSIONS

TAPSE was an independent predictor of one-year all-cause mortality in mechanically ventilated septic patients. RVOT-FS was not associated with one-year mortality and added no prognostic value to TAPSE in these patients.

Discrepant effects of heart failure on electrophysiological property in right ventricular outflow tract and left ventricular outflow tract cardiomyocytes

Ventricular arrhythmias commonly arise from the right (RVOT) and left ventricular outflow tracts (LVOT) in patients without structural heart disease. Heart failure (HF) significantly increases the risk of ventricular arrhythmias. The regional differences and how HF affects the electrophysiological characteristics of RVOT and LVOT cardiomyocytes remain unclear. The whole-cell patch-clamp technique was used to investigate the action potentials and ionic currents in isolated single RVOT and LVOT cardiomyocytes from control rabbits and rabbits with HF induced by rapid ventricular pacing. Comparison with control LVOT cardiomyocytes showed that control RVOT cardiomyocytes have a shorter action potential duration (APD), smaller late Na+ currents (INa-late), larger transient outward (Ito) and larger delayed rectifier K+ currents (IKr-tail), but had similar L-type Ca2+ currents (ICa-L) and Na+/Ca2+ exchanger (NCX) current. HF increased APD, INa-late and NCX, but decreased ICa-L and Ito in RVOT cardiomyocytes. In contrast with this, HF decreased APD and ICa-L, but increased Ito and IKr-tail in LVOT cardiomyocytes. In conclusion, RVOT and LVOT cardiomyocytes had distinctive electrophysiological characteristics. HF differentially modulates action potential morphology and ionic currents in RVOT and LVOT cardiomyocytes.