Postextrasystolic Contractility Normally Decays in Alternans in Canine In Situ Heart

Shimizu, Juichiro; Mohri, Satoshi; Iribe, Gentaro; Kitagawa, Yutaka; Itô, Haruo; Araki, Junichi; Takaki, Miyako; Suga, Hiroyuki

doi:10.2170/jjphysiol.53.313

Cited by 3 publications

(5 citation statements)

References 29 publications

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“…This difference between E max and LVP, however, existed in the previous study on canine in situ ejecting hearts [14]. These results contrast to the proportional PES alternans decays of both E max and LVP in canine isovolumic LVs at a given LVV [1][2][3][4][5][6].…”

Section: Discussioncontrasting

confidence: 74%

“…Although the PES alternans decays of the systemic arterial pressure and peak LVP have been occasionally observed clinically, to the best of our knowledge the present study is the first one reporting on the LV PES E max alternans in human hearts. This study thus demonstrates that human hearts share the same type of PES E max alternans decay as those observed in canine hearts either ex vivo isovolumic [1][2][3][4][5][6] or in situ ejecting [14]. Although we did not observe an exponential or monotonic decay of PES E max in the studied patient hearts with a spontaneous ES during the diagnostic examination, the present study does not exclude the possibility of the exponential decay of the PES Emax in human hearts.…”

Section: Discussioncontrasting

confidence: 50%

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Alternans Decay of Postextrasystolic Potentiation in Human Left Ventricle

Takao

Onishi

Dohi

et al. 2004

JJP

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One of the present authors, H. Suga, and his group have developed an integrative analysis method to assess the total amount of myocardial Ca 2ϩ handled in the excitation-contraction coupling in beating canine hearts [1][2][3][4][5][6]. This method requires that the intramyocardial Ca 2ϩ recirculation fraction (RF) and the left ventricular (LV) O 2 consumption for the excitationcontraction coupling both be measured in a beating heart [1][2][3][4][5][6]. The RF has conventionally been calculated from the exponential decay rate of the postextrasystolic (PES) potentiated E max [7,8]. However, against general expectations [7,8], Suga's group has found that the LV PES E max generally decays in alternans in canine hearts under both physiological and pathological conditions [1][2][3][4][5][6]9]. Nevertheless, they succeeded in extracting an exponential decay component from the PES E max alternans decay by peeling off the oscillatory component. They obtained the RF from the exponential decay component and then the total amount of Ca 2ϩ handled in the excitation-contraction coupling [1][2][3][4][5][6].We expected that the same approach successfully applied to the beating canine heart would also be applicable to the human heart. We first investigated in patient LVs whether the PES E max would decay in alternans or exponentially. Although the PES potentia- Japanese Journal of Physiology, 54, 87-91, 2004 Key words: arrhythmia, E max , calcium, recirculation fraction. Abstract:An organ-level assessment of the total Ca 2ϩ handled in the excitation-contraction coupling in a beating heart has been accomplished in canine left ventricles (LVs). This approach combines the intramyocardial Ca 2ϩ recirculation fraction (RF) with the cardiac O 2 consumption for the excitation-contraction coupling. The RF has conventionally been obtained from the exponential decay of the postextrasystolic (PES) potentiation of myocardial contractility. However, in canine LVs, the PES contractility in terms of E max (end-systolic pressure-volume ratio) has been shown to decay generally in alternans under both physiological and pathological conditions. Nevertheless, the RF can be obtained from the exponential decay component in the PES E max alternans decay. We expected that the same Ca 2ϩ assessment could be applied to the human heart. As the first step, we investigated whether the PES E max would decay in alternans or exponentially in patient LVs. We retrospectively analyzed 13 patient cases that had stable regular beats unexpectedly interrupted by a spontaneous extrasystole followed by a PES compensatory pause during their diagnostic examination. These patients had either mitral regurgitation, old myocardial infarction, or dilated cardiomyopathy. Their LV E max decayed consistently in alternans within the first several PES beats. These E max alternans decays resemble those reported in canine LVs. This finding suggests for the first time the applicability of the same organ-level RF assessment method developed for canine hearts to human hearts. [The J...

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Section: Discussioncontrasting

confidence: 74%

Section: Discussioncontrasting

confidence: 50%

Alternans Decay of Postextrasystolic Potentiation in Human Left Ventricle

Takao

Onishi

Dohi

et al. 2004

JJP

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“…It has been generally believed that PES contractility potentiation would decay exponentially in normal hearts under physiological conditions [26]. However, we have already reported that PESP usually decays in alternans in the canine excised, cross-circulated heart [9], and even in the canine in situ heart [11], which is more physiological than the excised, cross-circulated one. The present results also confirm the phenomenon.…”

Section: Discussionmentioning

confidence: 86%

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Arterial and Left Ventricular Pressures Illude Transient Alternans of Contractility during Postextrasystolic Potentiation

Iribe

Shimizu

Mohri

et al. 2004

JJP

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(PES) potentiation (PESP) is generally observed in isolated cross-circulated canine hearts [9,10] and in open-chest in situ hearts [11].On the other hand, the transient alternans of contractility obviously affects the alternans amplitudes of arterial pressure (AP) and left ventricular (LV) pressure (LVP) to various extents, depending on the cardiodynamic factors [1,3]. However, it remains uncertain which and how cardiodynamic factors affect the amplitude of alternans. Abstract:We have previously found that the postextrasystolic (PES) potentiation (PESP) of the left ventricular (LV) contractility (Emax) decays typically in transient alternans even in the normally ejecting canine heart. This contradicted the general expectation that arterial pressure (AP) and LV pressure (LVP) usually decay exponentially during PESP. We hypothesized this contradiction to be due to the different cardiodynamic behaviors of AP and LVP from LV Emax during PESP. We tested this hypothesis by measuring AP, LVP, LV volume, Emax, effective arterial elastance (Ea) as an index of afterload, and pulse pressure (PP) during PESP in eight anesthetized open-chest dogs by using the conductance catheter system. We changed Ea by changing the total peripheral resistance (TPR) with methoxamine hydrochloride (iv) and repeated the measurements. Although the Emax alternans patterns during PESP were comparable between the normal and high afterloads, LVP and PP were slightly potentiated and alternated under the normal afterload, whereas LVP and PP were obviously potentiated and alternated under the high afterload. We also simulated the effects of Ea/Emax on the transient alternans of AP and LVP on a computer. Despite the same alternans pattern of Emax, a higher Ea/Emax, which is typical in heart failure, caused a larger PP alternans, whereas a lower Ea/Emax, which is typical in normal hearts, almost eliminated it. These results suggest that a transient alternans of LV contractility during PESP could be overlooked when AP and LVP are monitored in in situ normal hearts.

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Decay of postextrasystolic potentiation in the left and right ventricles of intact canine hearts

Black¹,

Ewert

Mulligan

2009

2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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Intracellular regulation of myocardial Ca2+ has long been of interest to physiologists. The force-interval relationship provides a phenomenological approach that permits insight into aspects of calcium regulation. The response to an extrasystole is a potentiation in contractile force and the recovery in contractile force is described by the recirculation fraction (RF). The RF provides a gross estimation of calcium uptake by sarcoplasmic reticulum (SR), leading to myocardial relaxation. The current study focused on the relationship of right (RV) and left ventricular (LV) RF in canines under several contractile states. Anesthetized canines (n = 5) were catheterized for RV and LV pressure measurements. dP/dt(max) for the RV and LV was calculated for three baseline beats, one extrasystole and the first five postextrasystolic beats. The relationship between the LV dP/dt(max) and RV dP/dt(max) for all of the mentioned beats was then examined. Contractility was increased with calcium chloride and extrasystoles were delivered. Once cardiac function returned to a baseline level, contractility was reduced by increasing the concentration of isoflurane and the evaluation repeated. All ventricular contractions were controlled by RA pacing to maintain intrinsic conduction. A strong linear relationship between RV and LV dP/dt(max) (r = 0.94 +/- .06) existed for most canine's contractile states. These results build on findings in isolated hearts and demonstrate that biventricular response to extrasystoles and subsequent contractile recovery is both linear and correlated, suggesting that intracellular calcium regulation in a given heart across contractile state is static.

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Postextrasystolic Contractility Normally Decays in Alternans in Canine In Situ Heart

Cited by 3 publications

References 29 publications

Alternans Decay of Postextrasystolic Potentiation in Human Left Ventricle

Alternans Decay of Postextrasystolic Potentiation in Human Left Ventricle

Arterial and Left Ventricular Pressures Illude Transient Alternans of Contractility during Postextrasystolic Potentiation

Decay of postextrasystolic potentiation in the left and right ventricles of intact canine hearts

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