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Query: UMLS:C0018801 (heart failure)
 72,216 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Forty-eight dogs had pacing overdrive at 250 beats/min for 4-6 wk until heart failure developed. Myocardium from pacing dogs had a decrease in tension and maximum unloaded velocity of shortening (Vmax). Pacing dogs had an increase in circulating catecholamines during exercise but a lower maximal heart rate (214 +/- 19 vs. 241 +/- 26 beats/min, P less than 0.05). A blunted chronotropic response to isoproterenol was also found. However, despite a decrease in beta-adrenergic receptor density (80 +/- 14 vs. 122 +/- 14 fmol/mg, P less than 0.001) and a decrease in beta-adrenergic signal transduction [isoproterenol-induced adenosine 3',5'-cyclic monophosphate (cAMP) production 230 +/- 45 vs. 339 +/- 64 pmol.mg-1.min-1, P less than 0.001], Vmax normalized in response to isoproterenol in pacing dogs (2.3 +/- 0.6 vs. 2.2 +/- 0.5 Lmax/s, NS, where Lmax is length at which maximum developed tension occurs). Tension did not normalize (8 +/- 2 vs. 12 +/- 2 g/mm2, P less than 0.001). Thus in this model of heart failure, despite widespread evidence of decreased beta-adrenergic signal transduction, indexes of shortening but not force generation normalize in response to isoproterenol.
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PMID:Myocardial beta-adrenergic and mechanical properties in pacing-induced heart failure in dogs. 131 28

Myocardial failure in dilated cardiomyopathy may result from subcellular alterations in contractile protein function, excitation-contraction coupling processes, or recovery metabolism. We used isometric force and heat measurements to quantitatively investigate these subcellular systems in intact left ventricular muscle strips from nonfailing human hearts (n = 14) and from hearts with end-stage failing dilated cardiomyopathy (n = 13). In the failing myocardium, peak isometric twitch tension, maximum rate of tension rise, and maximum rate of relaxation were reduced by 46% (p = 0.013), 51% (p = 0.003), and 46% (p = 0.018), respectively (37 degrees C, 60 beats per minute). Tension-dependent heat, reflecting the number of crossbridge interactions during the isometric twitch, was reduced by 61% in the failing myocardium (p = 0.006). In terms of the individual crossbridge cycle, the average crossbridge force-time integral was increased by 33% (p = 0.04) in the failing myocardium. In the nonfailing myocardium, the crossbridge force-time integral was positively correlated with the patient's age (r = 0.86, p less than 0.02), whereas there was no significant correlation with age in the failing group. The amount and rate of excitation-contraction coupling-related heat evolution (tension-independent heat) were reduced by 69% (p = 0.24) and 71% (p = 0.028), respectively, in the failing myocardium, reflecting a considerable decrease in the amount of calcium released and in the rate of calcium removal. The efficiency of the metabolic recovery process, as assessed by the ratio of initial heat to total activity-related heat, was similar in failing and nonfailing myocardium (0.54 +/- 0.03 versus 0.50 +/- 0.02, p = 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Alteration of contractile function and excitation-contraction coupling in dilated cardiomyopathy. 157 41

The intrinsic metabolic capacity of the liver at end-stage heart failure in the pacing overdrive dog model of congestive heart failure was evaluated ex vivo. Congestive heart failure was induced in seven adult mongrel dogs (20-30 kg) by cardiac electrical pacing at a frequency of 240 stimuli/min until the development of overt heart failure; seven other dogs served as controls. The animals were then anesthetized and the right ventricular papillary muscles and samples from the left lateral hepatic lobes were collected. The degree of myocardial dysfunction as well as the total amount and the activities of cytochromes P-450 were evaluated. Tension, maximum rate of tension rise, and Vmax were significantly lower (40-60%) in the paced than in the control dogs, indicating a marked myocardial dysfunction. Moreover, significant decreases in total cytochrome P-450 (0.31 +/- 0.04 vs. 0.53 +/- 0.03 nmol/mg of microsomal protein, p less than 0.01) and in the intensity of four different electrophoretic protein bands (molecular masses of 46, 48, 50, and 59 kDa) occurred in the dogs with congestive heart failure. The decrease in total cytochrome P-450 was accompanied by a significant reduction in aminopyrine N-demethylase activity (1.74 +/- 0.25 vs. 2.91 +/- 0.40 nmol/min/mg of microsomal protein, p less than 0.05). Immunoblot analysis using antibodies to two different dog liver phenobarbital-inducible cytochromes P-450 demonstrated that PBD-1 (a P-450IIIA) was not affected by congestive heart failure, whereas PBD-2 (a P-450IIB) was markedly decreased.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of congestive heart failure on the intrinsic metabolic capacity of the liver in the dog. 168 47

A valveless, single orifice polyurethane ventricle was implanted on the brachiocephalic artery in sheep (n = 14) to provide extraaortic counterpulsation. In parallel, an intraaortic balloon was placed in the descending thoracic aorta. Both devices were pneumatically driven by a standard intraaortic balloon pump (IABP) console at a preload of 40 cc. Severe cardiac failure was induced with high dosages of esmolol. Measured parameters were aortic pressure (PA) and flow (QA), coronary flow (QC), and left ventricular pressure (PLV). Tension time index (TTI), total QA and QC, and end-diastolic aortic pressure (EDP) were computed to compare the efficacy of counterpulsation between assisted and unassisted conditions. Three conditions of inflation/deflation timing were examined: Normal timing (NT), early inflation (EI), and late deflation (LD). Results indicated that extraaortic counterpulsation device actuation yielded statistically significant increases in QC, and significant decreases in EDP and TTI for all timing conditions examined, when compared with unassisted conditions. Flow was significantly increased only for EI and NT timing conditions. Counterpulsation delivered with IABP yielded statistically significant increases in EDP for LD timing, and significant decreases in TTI for NT only. These results indicate that EACD is much less dependent on inflation/deflation timing when compared with IABP. The extraaortic counterpulsation device consistently increases QC and decreases TTI, which enhances the oxygen supply/consumption ratio (S/C) of the left ventricle. The intraaortic balloon pump does not significantly increase S/C in severe cardiac failure, and will increase afterload if deflation timing is not properly set.
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PMID:Comparison of an extraaortic counterpulsation device versus intraaortic balloon pumping in severe cardiac failure. 175 Nov 78

Alternans in heart is important as pulsus alternans in cardiac failure and electrophysiological alternans in myocardial ischemia. The explanation of this phenomenon is still unclear. We attempted to investigate the cellular mechanisms of alternans by measuring intracellular free calcium concentration [( Ca2+]i) with the photoprotein aequorin in isolated ferret papillary muscles. Tension and length were also recorded simultaneously. Transient mechanical alternans lasting five to 20 contractions could be reliably induced in this preparation by following a 30-second rest period with stimulation at a fast rate (2-4 Hz). Production of sustained mechanical alternans, which lasted longer than 20 contractions and could persist for several hundred contractions, required additional interventions, consisting of a lower temperature (25 degrees C), a lower external calcium concentration (1 mM), and a lower pH (6.91) than control conditions (0.33-0.5 Hz, 30 degrees C, 2 mM Ca2+, pH 7.36). Transient mechanical alternans was associated with transient in-phase alternation of aequorin light and, hence, [Ca2+]i. Sustained mechanical alternans was associated with sustained in-phase alternation of aequorin light as well as incomplete relaxation of tension. However, when muscles were switched from isometric to unloaded isotonic contraction, relaxation between stimuli was complete but contraction and the aequorin light signal continued to alternate. The addition of 10 mM caffeine or 10 microns ryanodine abolished transient and sustained mechanical alternans and also abolished the associated alternation of aequorin light. Commensurate with the action of ryanodine, which allows the sarcoplasmic reticulum to reaccumulate calcium to a limited extent after a period of rapid stimulation, sustained mechanical alternans sometimes reappeared in an attenuated form 30 to 50 contractions after the addition of ryanodine. These results demonstrate that incomplete muscle relaxation between beats need not be present for alternans to occur, and support the hypothesis that alternans is caused by intracellular calcium cycling involving the sarcoplasmic reticulum.
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PMID:Changes in intracellular calcium during mechanical alternans in isolated ferret ventricular muscle. 230

The calcium sensitizing effects of the cardiotonic agent pimobendan on force production were investigated on chemically skinned human papillary muscle fibres. The papillary muscles were obtained from patients undergoing mitral valve replacement operations. Tension was produced by different free calcium concentrations and 100 mumol/l of pimobendan shifted the pCa-tension relationship significantly to the left. The effects of pimobendan were concentration dependent (10-300 mumol/l) but additionally also correlated with the state of left ventricular performance of the patients. Skinned papillary muscle fibres obtained from patients with reduced ventricular performance were more sensitive to calcium as well as pimobendan compared with fibres from patients with normal left ventricular performance. No differences in response to pimobendan were observed between fibres from NYHA II and NYHA III heart failure patients.
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PMID:Pimobendan increases calcium sensitivity of skinned human papillary muscle fibers. 272 24

We hypothesized that myocardial loading can be increased when extracorporeal pulse flow occurs during systole, and that this may adversely affect myocardial working conditions in heart failure patients supported by extracorporeal life support (ECLS). This study was designed to compare myocardial loading and myocardial oxygen consumption/supply balance between nonpulsatile ECLS and asynchronized pulsatile ECLS in a myocardial stunning model. Thirteen, 23-42 kg dogs were allotted to a nonpulsatile group and an asynchronous pulsatile group. Coronary sinus lactate level, mixed venous oxygen consumption (MvO2), and left anterior descending coronary artery flow were measured. The real-time pressure of the left ventricle and the ascending aorta was monitored, and the lowest left ventricular pressure and tension time index were calculated. Our results showed that the lactate level and the lowest left ventricular pressure were lower in the pulsatile group than in the nonpulsatile group at 30 minutes after ECLS was applicated (p < 0.05, respectively). Tension time index in the pulsatile ECLS group was substantially lower than in the nonpulsatile group. Left anterior descending coronary flow did not show significant difference between the two groups. In conclusion, asynchronous pulsatile ECLS may also be superior to nonpulsatile ECLS in myocardial volume unloading and oxygen consumption/supply balance.
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PMID:Comparison of myocardial loading between asynchronous pulsatile and nonpulsatile percutaneous extracorporeal life support. 1835 51

1. There is evidence that different aetiologies of heart failure, especially ischaemic vs dilated cardiomyopathy (ICM and DCM, respectively), may influence the prognosis of patients with this disease. Patients with ICM have a worse prognosis than those with DCM; the mechanisms underlying this difference have not yet been clarified. The aim of the present study was to investigate whether there are changes in myofibrillar function depending on the aetiology of human heart failure. 2. Ca(2+) -dependent tension (DT) and actomyosin ATPase activity (MYO) in Triton X-skinned fibre preparations of the left ventricular myocardium from patients with heart failure due to ICM (n=5) and DCM (n=5) were measured. Tension-dependent ATP consumption was calculated by the ratio of DT and MYO ('tension cost'). Non-failing myocardium (NF) from donor hearts, which could not be transplanted because of technical reasons, was evaluated as a control. 3. Although DT was reduced, the myofibrillar Ca(2+) sensitivity of DT and MYO, as well as tension cost, were increased in preparations from ICM and DCM myocardium compared with NF. The Ca(2+) sensitivity of DT and MYO was significantly increased in ICM compared with DCM preparations, resulting in more economic cross-bridge cycling in ICM than in DCM. 4. In conclusion, ICM is associated with an increased Ca(2+) sensitivity of myofibrillar tension and ATPase activity accompanied by decreased tension cost compared with DCM. Thus, the worse prognosis associated with ICM does not seem to be due to differences in myofibrillar function.
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PMID:Increased Ca2+ sensitivity of myofibrillar tension in ischaemic vs dilated cardiomyopathy. 2080 10

Tension hydrothorax is a rare complication of pneumonectomy for pleural mesothelioma and an exceptionally rare cause of heart failure. We describe a patient who had undergone extrapleural pneumonectomy, chemotherapy, and radiation for pleural mesothelioma and who developed heart failure symptoms within months of the completion of treatment. Investigation showed a massive left pleural effusion resulting in tension hydrothorax, mediastinal shift, and evidence of right heart failure with constrictive physiology and low cardiac output. Therapeutic thoracentesis resulted in increase in cardiac output and symptomatic improvement.
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PMID:Heart failure due to tension hydrothorax after left pneumonectomy. 2437 Aug