Spatial correlation of action potential duration and diastolic dysfunction in transgenic and drug-induced LQT2 rabbits.
Heart Rhythm
; 10(10): 1533-41, 2013 Oct.
Article
em En
| MEDLINE
| ID: mdl-23892340
ABSTRACT
BACKGROUND:
Enhanced dispersion of action potential duration (APD) is a major contributor to long QT syndrome (LQTS)-related arrhythmias.OBJECTIVE:
To investigate spatial correlations of regional heterogeneities in cardiac repolarization and mechanical function in LQTS.METHODS:
Female transgenic LQTS type 2 (LQT2; n = 11) and wild-type littermate control (LMC) rabbits (n = 9 without E4031 and n = 10 with E4031) were subjected to phase contrast magnetic resonance imaging to assess regional myocardial velocities. In the same rabbits' hearts, monophasic APDs were assessed in corresponding segments.RESULTS:
In LQT2 and E4031-treated rabbits, APD was longer in all left ventricular segments (P < .01) and APD dispersion was greater than that in LMC rabbits (P < .01). In diastole, peak radial velocities (Vr) were reduced in LQT2 and E4031-treated compared to LMC rabbits in LV base and mid (LQT2 -3.36 ± 0.4 cm/s, P < .01; E4031-treated -3.24 ± 0.6 cm/s, P < .0001; LMC -4.42 ± 0.5 cm/s), indicating an impaired diastolic function. Regionally heterogeneous diastolic Vr correlated with APD (LQT2 correlation coefficient [CC] 0.38, P = .01; E4031-treated CC 0.42, P < .05). Time-to-diastolic peak Vr were prolonged in LQT2 rabbits (LQT2 196.8 ± 2.9 ms, P < .001; E4031-treated 199.5 ± 2.2 ms, P < .0001, LMC 183.1 ± 1.5), indicating a prolonged contraction duration. Moreover, in transgenic LQT2 rabbits, diastolic time-to-diastolic peak Vr correlated with APD (CC 0.47, P = .001). In systole, peak Vr were reduced in LQT2 and E4031-treated rabbits (P < .01) but longitudinal velocities or ejection fraction did not differ. Finally, random forest machine learning algorithms enabled a differentiation between LQT2, E4031-treated, and LMC rabbits solely based on "mechanical" magnetic resonance imaging data.CONCLUSIONS:
The prolongation of APD led to impaired diastolic and systolic function in transgenic and drug-induced LQT2 rabbits. APD correlated with regional diastolic dysfunction, indicating that LQTS is not purely an electrical but an electromechanical disorder.Palavras-chave
APD; APD(75); CC; Cardiac MRI; Cardiac electrophysiology; Diastolic function; ECG; EPS; I(Ca,L); I(Kr); IV; L-type Ca2+ current; LMC; LQT2; LQTS; LV; Long QT syndrome; MAP; MRI; QTc; Rabbits; Repolarization; SD; TTP; Vr; Vr_dia; Vz; Vz_dia; [Ca(2+)](i); action potential duration; action potential duration at 75% of repolarization; correlation coefficient; cytoplasmic Ca(2+) concentration; diastolic peak long-axis velocities; diastolic peak radial velocities; electrocardiogram; electrophysiological study; heart-rate corrected QT; intravenously; left ventricle/ventricular; long QT syndrome; long QT syndrome type 2; long-axis velocities; magnetic resonance imaging; monophasic action potential; pVT; polymorphic ventricular tachycardia; radial velocities; rapid delayed rectifier potassium current; standard deviation; time-to-peak velocities; wild-type littermate control
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Arritmias Cardíacas
/
Síndrome do QT Longo
/
Potenciais de Ação
Tipo de estudo:
Diagnostic_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
2013
Tipo de documento:
Article