Rhythm effects on contractility of the beating isovolumic left ventricle

Lendrum, Bessie L.; Feinberg, Harold; Boyd, Edward G.C.A.; Katz, L. N.

doi:10.1152/ajplegacy.1960.199.6.1115

Cited by 76 publications

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“…Cross-clamping of the aorta in three INTRODUCTION Mechanical alternans in isolated myocardium is said to result from an alternation in muscle fiber stretch (1) or from an alternation in the inotropic state of the muscle (2,3). Similarly, studies in pulsus alternans in the intact heart have shown this phenomenon to be both associated with (4)(5)(6) and independent of (7,8) alternations in ventricular filling or end-diastolic tension. The relative contribution of variations in contractile state and in initial fiber length, and tension to the pathogenesis of pulsus alternans in the intact heart is unknown since alternating beats have not been analyzed in terms of the myocardial length-tension-velocity relationship.…”

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confidence: 99%

The demonstration of alternating contractile state in pulsus alternans

Noble¹,

Nutter²

1970

J. Clin. Invest.

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A B S T R A C T Pulsus alternans was induced in 11anesthetized, open-chest dogs by rapid atrial pacing, and the left ventricular filling characteristics and lengthtension-velocity relationship of alternating beats were compared. The end-diastolic circumferences (circ) of the strong beats were slightly, but significantly, increased over the weak beats (7.3 > 6.9 cm, P < 0.01), confirming that diastolic filling does alternate in pulsus alternans. This alternation in initial fiber length seemed to result from an alternation in the prior end-systolic length, rather than from an alternation in diastolic filling time or compliance. There was also no difference in enddiastolic tension as measured by an isometric strain gauge suggesting no difference in contractile element relaxation before weak and strong beats.The contractile state of the strong beats was consistently greater than that of the weak beats when contractility was defined in terms of: (a) Vmax (3.13 > 2.53 circ/sec, P <0.01); and (b) the velocity of circumferential fiber shortening (0.84 > 0.39 circ/sec, P < 0.001) and developed tension (82.5 > 74 g/cm, P < 0.01) at isolength. The length-tension-velocity relationship of the left ventricle also varied between strong and weak beats when: (a) the maximum velocity of contractile element shortening at least common tension (1.68> 1.28 circ/sec, P <0.05); and (b) the velocity of circumferential fiber shortening (0.81 > 0.39 circ/ sec, P < 0.001) at maximum developed tension were examined. Analysis of the length-tension-velocity characteristics of sequential beats at the onset of alternans in three dogs suggests that an alternation in contractility initiates alternans, with secondary alternations in ventricular filling. Cross-clamping of the aorta in three

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confidence: 99%

The demonstration of alternating contractile state in pulsus alternans

Noble¹,

Nutter²

1970

J. Clin. Invest.

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“…Also the frequency-dependent increase in the contractility decreased when the duration of stimulation was increased. The increase in cardiac contractility with an increase in the frequency of stimulation is well known (Katzung, Rasin & Scheider, 1957;Lendrum, Feinberg, Boyd & Katz, 1960;Blinks & Koch-Weser, 1961). The present results confirm our (Prasad & Kidwai, 1974) preliminary observation that electrical stimulation of isolated sarcolemmal fraction produces an inhibition of the sarcolemmal ATPase.…”

Section: Discussionmentioning

confidence: 97%

Frequency‐dependent Changes in the Cardiac Sarcolemmal Atpase

Khatter

Prasad

1977

British J Pharmacology

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1Effects of various frequencies (0.25, 0.5, 1.0, 1.5 or 2.0 Hz) of stimulation for various durations (2, 5, 10 or 15 min) on the contractile force of trabecular or papillary muscles of dog myocardium were investigated. 2Effects of various frequencies (0, 0.25, 0.5, 1.0, 2.0 Hz) of various stimulus strengths (0.5, 1, 10 V) for various durations (2, 5, 10 or 15 min) on the Mg2+‐dependent Na+‐K+‐adenosinetriphosphatase (ATPase) of isolated sarcolemmal fraction of dog myocardium were determined. 3There was a frequency‐dependent increase in the contractility and inhibition of the Na+‐K+‐ATPase within 2 minutes. 4Frequency‐dependent increase in the contractility and inhibition of Na+‐K+‐ATPase decreased as the duration of stimulation was increased. 5The diminution in the inhibition of ATPase was associated with a decrease in the contractility with prolonged stimulation. 6These results suggest that the frequency‐dependent increase in the myocardial contractility might be mediated through an inhibition of the sarcolemmal ATPase.

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“…Alternation of end-diastolic volume has been considered an essential feature of mechanical alternans by some authors,6'5'6 but not by others. [8][9][10]17 On the basis of our findings, we suggest that in conditions of advanced LV disease or LV failure portions of the myocardium may contract with alternate strong or weak contractions in successive beats, while other portions of the ventricular myocardium contract with a discordant alternans or without any alternans. It seems reasonable to speculate that such discordant alternans would occur most often in patients with patchy involvement of the myocardium such as is seen in ischemic heart disease.…”

Section: Discussionmentioning

confidence: 97%

Echocardiography in mechanical alternans. With a note on the findings in discordant alternans within the left ventricle.

D’Cruz¹,

Cohen²,

Prabhu³

et al. 1976

Circulation

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SUMMARY We describe the echocardiographic manifestations of mechanical alternation of left ventricular (LV) contraction during regular sinus rhythm. Chronic LV dilatation and failure existed in all our four cases. Alternation was observed with respect to the following echocardiographic variables: amplitude and rate of increase of amplitude of systolic excursions of the LV posterior wall and ventricular septum (VS); reciprocal changes in the duration of LV ejection and pre-ejection periods (on the aortic valve echo) such that the SINCE PULSUS ALTERNANS was first described by Traube,' it has been the subject of extensive experimentation and comment, including a recent review.2 In addition, a number of hemodynamic studies have been carried out in man.3-10 Katz and Feil in 1937,11 and more recently, Spodick and St. Pierre"2 used phonocardiography and systolic time intervals in external arterial pulse tracings to investigate the pathophysiology of mechanical alternans. Visualization of alternately strong and weak ventricular contractions has been obtained by angiocardiographic methods,"M but hitherto, to our knowledge, no echocardiographic description of the phenomenon has appeared. Case Reports Patient 1Patient 1, a 30-year-old woman, had been admitted on several occasions for recurrent heart failure since the postpartum onset of her symptoms five years earlier. On examination she exhibited florid signs of severe left and right heart failure, including dyspnea at rest, orthopnea, basal pulmonary rales, gallop rhythm, and hepatomegaly. Pulsus alternans was evident on palpation of the radial pulse, and confirmed by sphygmomanometry which showed a difference of 15 to 20 mm Hg in systolic pressure between alternate beats. Her electrocardiogram (ECG) showed left ventricular (LV) hypertrophy and strain, and regular sinus rhythm with occasional ventricular premature beats. No electrical alternans was present. Her chest roentgenogram revealed considerable cardiomegaly and pulmonary venous congestion. An external carotid pulse tracing depicted an alternation in the amplitude of the arterial pulse, at a regular heart rate. total duration of LV electromechanical systole remained constant; reciprocal changes in the duration of RV ejection and pre-ejection periods (on the pulmonic valve echo) such that the total duration of RV electromechanical systole remained constant; systolic anterior excursion of the aortic root as a whole; steepness of the mitral EF slope; septal and LV posterior wall diastolic position; and end-systolic LV diameter. In two patients, discordant alternans of the motion of the LV posterior wall and the VS was observed.Echocardiography was performed using a Picker Echoview 10 ultrasonoscope connected to a Honeywell 1856 strip-chart Visicorder. Echocardiography of the aortic root ( fig. 1, top) showed alternation in the amplitude of anterior systolic motion of the aortic root as a whole, and in the velocity of this anterior excursion. Alternation was manifest also in the duration of systolic opening of the aor...

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Rhythm effects on contractility of the beating isovolumic left ventricle

Cited by 76 publications

References 0 publications

The demonstration of alternating contractile state in pulsus alternans

The demonstration of alternating contractile state in pulsus alternans

Frequency‐dependent Changes in the Cardiac Sarcolemmal Atpase

Echocardiography in mechanical alternans. With a note on the findings in discordant alternans within the left ventricle.

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