Browsing by Subject "Heart Ventricles"

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    Cavopulmonary assist for the failing Fontan circulation: impact of ventricular function on mechanical support strategy
    (Ovid Technologies (Wolters Kluwer) - Lippincott Williams & Wilkins, 2014-11) Giridharan, Guruprasad A.; Ising, Mickey; Sobieski, Michael A.; Koenig, Steven C.; Chen, Jun; Frankel, Steven C.; Rodefeld, Mark D.; Department of Surgery, IU School of Medicine
    Mechanical circulatory support--either ventricular assist device (VAD, left-sided systemic support) or cavopulmonary assist device (CPAD, right-sided support)--has been suggested as treatment for Fontan failure. The selection of left- versus right-sided support for failing Fontan has not been previously defined. Computer simulation and mock circulation models of pediatric Fontan patients (15-25 kg) with diastolic, systolic, and combined systolic and diastolic dysfunction were developed. The global circulatory response to assisted Fontan flow using VAD (HeartWare HVAD, Miami Lakes, FL) support, CPAD (Viscous Impeller Pump, Indianapolis, IN) support, and combined VAD and CPAD support was evaluated. Cavopulmonary assist improves failing Fontan circulation during diastolic dysfunction but preserved systolic function. In the presence of systolic dysfunction and elevated ventricular end-diastolic pressure (VEDP), VAD support augments cardiac output and diminishes VEDP, while increased preload with cavopulmonary assist may worsen circulatory status. Fontan circulation can be stabilized to biventricular values with modest cavopulmonary assist during diastolic dysfunction. Systemic VAD support may be preferable to maintain systemic output during systolic dysfunction. Both systemic and cavopulmonary support may provide best outcome during combined systolic and diastolic dysfunction. These findings may be useful to guide clinical cavopulmonary assist strategies in failing Fontan circulations.
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    Small conductance calcium-activated potassium current is important in transmural repolarization of failing human ventricles
    (Ovid Technologies Wolters Kluwer - American Heart Association, 2015-06) Yu, Chih-Chieh; Corr, Christopher; Shen, Changyu; Shelton, Richard; Yadava, Mrinal; Rhea, Isaac; Straka, Susan; Fishbein, Michael C.; Chen, Zhenhui; Lin, Shien-Fong; Lopshire, John C.; Chen, Peng-Sheng; Department of Medicine, IU School of Medicine
    BACKGROUND: The transmural distribution of apamin-sensitive small conductance Ca(2+)-activated K(+) (SK) current (IKAS) in failing human ventricles remains unclear. METHODS AND RESULTS: We optically mapped left ventricular wedge preparations from 12 failing native hearts and 2 rejected cardiac allografts explanted during transplant surgery. We determined transmural action potential duration (APD) before and after 100 nmol/L apamin administration in all wedges and after sequential administration of apamin, chromanol, and E4031 in 4 wedges. Apamin prolonged APD from 363 ms (95% confidence interval [CI], 341-385) to 409 (95% CI, 385-434; P<0.001) in all hearts, and reduced the transmural conduction velocity from 36 cm/s (95% CI, 30-42) to 32 cm/s (95% CI, 27-37; P=0.001) in 12 native failing hearts at 1000 ms pacing cycle length (PCL). The percent APD prolongation is negatively correlated with baseline APD and positively correlated with PCL. Only 1 wedge had M-cell islands. The percentages of APD prolongation in the last 4 hearts at 2000 ms PCL after apamin, chromanol, and E4031 were 9.1% (95% CI, 3.9-14.2), 17.3% (95% CI, 3.1-31.5), and 35.9% (95% CI, 15.7-56.1), respectively. Immunohistochemical staining of subtype 2 of SK protein showed increased expression in intercalated discs of myocytes. CONCLUSIONS: SK current is important in the transmural repolarization in failing human ventricles. The magnitude of IKAS is positively correlated with the PCL, but negatively correlated with APD when PCL is fixed. There is abundant subtype 2 of SK protein in the intercalated discs of myocytes.