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Delayed Repolarization Underlies Ventricular Arrhythmias in Rats With Heart Failure and Preserved Ejection Fraction.

ABSTRACT: BACKGROUND:Heart failure with preserved ejection fraction (HFpEF) represents approximately half of heart failure, and its incidence continues to increase. The leading cause of mortality in HFpEF is sudden death, but little is known about the underlying mechanisms. METHODS:Dahl salt-sensitive rats were fed a high-salt diet (8% NaCl) from 7 weeks of age to induce HFpEF (n=38). Rats fed a normal-salt diet (0.3% NaCl) served as controls (n=13). Echocardiograms were performed to assess systolic and diastolic function from 14 weeks of age. HFpEF-verified and control rats underwent programmed electrical stimulation. Corrected QT interval was measured by surface ECG. The mechanisms of ventricular arrhythmias (VA) were probed by optical mapping, whole-cell patch clamp to measure action potential duration and ionic currents, and quantitative polymerase chain reaction and Western blotting to investigate changes in ion channel expression. RESULTS:After 7 weeks of a high-salt diet, 31 of 38 rats showed diastolic dysfunction and preserved ejection fraction along with signs of heart failure and hence were diagnosed with HFpEF. Programmed electric stimulation demonstrated increased susceptibility to VA in HFpEF rats (P<0.001 versus controls). The arrhythmogenicity index was increased (P<0.001) and the corrected QT interval on ECG was prolonged (P<0.001) in HFpEF rats. Optical mapping of HFpEF hearts demonstrated prolonged action potentials (P<0.05) and multiple reentry circuits during induced VA. Single-cell recordings of cardiomyocytes isolated from HFpEF rats confirmed a delay of repolarization (P=0.001) and revealed downregulation of transient outward potassium current (Ito; P<0.05). The rapid components of the delayed rectifier potassium current (IKr) and the inward rectifier potassium current (IK1) were also downregulated (P<0.05), but the current densities were much lower than for Ito. In accordance with the reduction of Ito, both Kcnd3 transcript and Kv4.3 protein levels were decreased in HFpEF rat hearts. CONCLUSIONS:Susceptibility to VA was markedly increased in rats with HFpEF. Underlying abnormalities include QT prolongation, delayed repolarization from downregulation of potassium currents, and multiple reentry circuits during VA. Our findings are consistent with the hypothesis that potassium current downregulation leads to abnormal repolarization in HFpEF, which in turn predisposes to VA and sudden cardiac death.

SUBMITTER: Cho JH

PROVIDER: S-EPMC5698112 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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Delayed Repolarization Underlies Ventricular Arrhythmias in Rats With Heart Failure and Preserved Ejection Fraction.

Cho Jae Hyung JH Zhang Rui R Kilfoil Peter J PJ Gallet Romain R de Couto Geoffrey G Bresee Catherine C Goldhaber Joshua I JI Marbán Eduardo E Cingolani Eugenio E

Circulation 20171003 21

<h4>Background</h4>Heart failure with preserved ejection fraction (HFpEF) represents approximately half of heart failure, and its incidence continues to increase. The leading cause of mortality in HFpEF is sudden death, but little is known about the underlying mechanisms.<h4>Methods</h4>Dahl salt-sensitive rats were fed a high-salt diet (8% NaCl) from 7 weeks of age to induce HFpEF (n=38). Rats fed a normal-salt diet (0.3% NaCl) served as controls (n=13). Echocardiograms were performed to assess ...[more]

PMID: 28974519

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Project description:ObjectivesTo determine clinical and prognostic differences between preserved and deteriorated systolic function (defined as left ventricular (LV) ejection fractions > or = 50% and < 50%, respectively) in patients with heart failure satisfying modified Framingham criteria.Patients and methodsRecords were studied of 1252 patients with congestive heart failure (CHF) (mean (SD) age 69.4 (11.7) years; 485 women, 767 men) who had been admitted to a cardiology service for CHF in the period 1991-2002 and whose LV systolic function had been echocardiographically evaluated within two weeks of admission. Data were collected on the main clinical findings, supplementary examinations, treatment, and duration of hospitalisation. Whether the patient was alive in the spring of 2003 was evaluated by searching the general archives of the hospital and by telephone survey.ResultsLV systolic function was preserved in 39.8% of patients. Age, female to male sex ratio, and prevalence of atrial fibrillation, valve disease, and other non-ischaemic, non-dilated cardiopathies were all significantly greater in the group with preserved systolic function. New York Heart Association functional class IV, third heart sound, jugular vein congestion, cardiomegaly, radiological signs of lung oedema, pathological Q waves, left bundle branch block, sinus rhythm, ischaemic cardiopathy, and dilated cardiomyopathy were all significantly more prevalent in the group with deteriorated systolic function, as was treatment with angiotensin converting enzyme inhibitors and most other antihypertensive drugs on discharge from hospital. There was no significant difference in survival between the groups with preserved and deteriorated systolic function (either survival regardless of age at admission or in subgroups aged < 75 and > or = 75 years at admission). In the whole group, survival rates after one, three, and five years were 84.0%, 66.7%, and 50.9%, respectively.ConclusionIn view of the poor prognosis of patients with CHF with preserved LV systolic function, who are currently treated empirically, it is to be hoped that relevant controlled clinical trials under way will afford information allowing optimisation of their treatment.

Project description:AIMS:Neuregulin1-? (NRG1-?) is released from microvascular endothelial cells in response to inflammation with compensatory cardioprotective effects. Circulating NRG1-? is elevated in heart failure (HF) with reduced ejection fraction (HFrEF) but not studied in HF with preserved EF (HFpEF). METHODS AND RESULTS:Circulating NRG1-? was quantified in 86 stable patients with HFpEF (EF ?45% and N-terminal pro-brain natriuretic peptide >300 ng/L), in 86 patients with HFrEF prior to and after left ventricular assist device (LVAD) and/or heart transplantation (HTx) and in 21 healthy controls. Association between NRG1-? and the composite outcome of all-cause mortality/HF hospitalization in HFpEF and all-cause mortality/HTx/LVAD implantation in HFrEF with and without ischaemia assessed as macrovascular coronary artery disease was assessed. In HFpEF, median (25th-75th percentile) NRG1-? was 6.5 (2.1-11.3) ng/mL; in HFrEF, 3.6 (2.1-7.6) ng/mL (P = 0.035); after LVAD, 1.7 (0.9-3.6) ng/mL; after HTx 2.1 (1.4-3.6) ng/mL (overall P < 0.001); and in controls, 29.0 (23.1-34.3) ng/mL (P = 0.001). In HFrEF, higher NRG1-? was associated with worse outcomes (hazard ratio per log increase 1.45, 95% confidence interval 1.04-2.03, P = 0.029), regardless of ischaemia. In HFpEF, the association of NRG1-? with outcomes was modified by ischaemia (log-rank P = 0.020; Pinteraction = 0.553) such that only in ischaemic patients, higher NRG1-? was related to worse outcomes. In contrast, in patients without ischaemia, higher NRG1-? trended towards better outcomes (hazard ratio 0.71, 95% confidence interval 0.48-1.05, P = 0.085). CONCLUSIONS:Neuregulin1-? was reduced in HFpEF and further reduced in HFrEF. The opposing relationships of NRG1-? with outcomes in non-ischaemic HFpEF compared with HFrEF and ischaemic HFpEF may indicate compensatory increases of cardioprotective NRG1-? from microvascular endothelial dysfunction in the former (non-ischaemic HFpEF), but this compensatory mechanism is overwhelmed by the presence of ischaemia in the latter (HFrEF and ischaemic HFpEF).

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Delayed Repolarization Underlies Ventricular Arrhythmias in Rats With Heart Failure and Preserved Ejection Fraction.

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Delayed Repolarization Underlies Ventricular Arrhythmias in Rats With Heart Failure and Preserved Ejection Fraction.

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