Myocardial Force-Velocity Relations Studied in Intact Unanesthetized Man*

Glick, Gerald; Sonnenblick, Edmund H.; Braunwald, Eugene

doi:10.1172/jci105215

Cited by 109 publications

(49 citation statements)

References 21 publications

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“…Since increasing heart rate is believed to increase myocardial contractility [8], the present results might in part be related to the observation of a statistically significant decrease in heart rate in the puppies treated with propranolol, while adult heart rate was not significantly changed (Table I). When ventricular pacing was employed in four puppies treated with propranolol, however, returning the heart rate to control values did not alter the contractility indices significantly (Fig.…”

Section: Discussionmentioning

confidence: 56%

Cardiovascular Effects of Propranolol in Intact Puppies and Adult Dogs

Truccone

Levine

1973

Pediatr Res

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ExtractThe cardiovascular effects of propranolol (Inderal) [24] were compared in 13 adult dogs and 14 puppies. Left ventricular (LV) pressure was measured with a catheter tip manometer and myocardial contractility was assessed by LV measurements of peak rate of pressure development (LV dp/dt), LV dp/dt at 40 mm Hg LV pressure (P 40 dp/dt), and peak LV (dp/dt)/P. Cardiac output was measured by indocyanine green dye dilution. Measurements were made before and 5 min after intravenous propranolol (0.5 g/kg) administered over a period of 1 min. In the adult dog, propranolol produced a significant depression of cardiac index and peak LV systolic pressure, significant elevation of systemic resistance index and LV end-diastolic pressure, and a significant fall in indices of myocardial contractility. The changes in heart rate, cardiac index, peak LV systolic pressure, and contractility indices produced by propranolol were 2-4 times greater, on a percentage basis, in the puppies as in the adult dogs. The systemic resistance index and LV end-diastolic pressure changed similarly in both groups. The increased sensitivity of the puppies to propranolol appears to reflect a greater dependence on circulating catecholamines in the immature circulation. Speculation

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Section: Discussionmentioning

confidence: 56%

Cardiovascular Effects of Propranolol in Intact Puppies and Adult Dogs

Truccone

Levine

1973

Pediatr Res

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“…This demonstration of an augmentation in contractility for the strong beat was supported when the forcevelocity relation was examined during ventricular ejection. The force-velocity relation at any instant in time is a function of the instantaneous muscle length (24); therefore, the measurement of tension and velocity in alternating beats at a common length during ejection should provide an additional comparison of the contractile state of the two beats (16). The greater velocity of circumferential shortening (VcF) and the greater wall tension developed by the strong beat at systolic isolength indicates an enhanced contractile state.…”

Section: Resultsmentioning

confidence: 99%

“…K is the modulus of elasticity of the series elastic element which is equal to 28 in the dog heart (13) (14). Vee was also used to assess the ventricular performance of weak and strong beats by comparing Vee at the least tension common to both beats (15 The contractile state of alternating beats was estimated by comparing Vf and tension at equal lengths; i.e., at the isolength point on the dimension trace (16). All D, T, and Vcr comparisons were performed during an interval from 10 mnsec before peak aortic flow to 30 msec after peak aortic flow to assure that the length-tension-velocity relationship was determined during the maximum active state of the muscle (12 FlowAO Diameter LV dp/dt LV Pressure LV ECG" FIGURE 1 Left ventricular stroke volume, diameter, and pressure in pulsus alternans.…”

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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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“…scribed in detail previously (12,18). When, at any given instantaneous myocardial diameter or length (isolength point), the velocity of shortening (Vlsolength, i.e., V,.0) increases, while intraventricular pressure (Pisolength, i.e., P1s0) rises or remains constant, a shift in myocardial force-velocity relations reflecting a positive inotropic effect is considered to have occurred.…”

Section: Methodsmentioning

confidence: 99%

Extent of Carotid Sinus Regulation of the Myocardial Contractile State in Conscious Dogs

Vatner¹,

Higgins²,

Franklin³

et al. 1972

J. Clin. Invest.

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A B S T R A C T The effects of bilateral carotid artery occlusion (BCO) and carotid sinus nerve stimulation (CSNS) on left ventricular (LV) pressure (P), diameter (D), velocity of contraction (V), rate of change of pressure (dP/dt), and cardiac output were studied in conscious dogs instrumented with ultrasonic diameter gauges, miniature pressure gauges, and aortic electromagnetic flow transducers. The effects of BCO and CSNS were also studied after autonomic blockade and were compared to similar alterations in pressure produced by norepinephrine, methoxamine, and nitroglycerin. When heart rate was maintained constant with atrial stimulation, BCO had little effect on ventricular contractility, increasing isolength systolic pressure (LV Pis.) by 36% while isolength velocity of myocardial shortening (Vt..) decreased by 12% and (dP/dt)/P fell by 8%. These effects could be explained largely by vasoconstriction, since elevating systolic pressure with methoxamine produced similar results, while norepinephrine increased Vt.. by 36% and (dP/dt)/P by 56%S. CSNS produced directionally opposite results from BCO; it decreased Pi.8 by 15%, Vt.0 increased by 11%, while (dP/dt)/P remained almost constant. These effects may be explained largely by vasodilatation since reducing systolic pressure to the same level with nitroglycerin produced similar results. When peripheral vasoconstriction was minimized by phenoxybenzamine pretreatment, BCO produced a slight positive inotropic effect (Ptso increased by 8%o, Vt.. by 4%, and (dp/ This study was presented in part at the 44th Annual Scientific Sessions of the American Heart Association, Anaheim, Calif., November 1971. An

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Myocardial Force-Velocity Relations Studied in Intact Unanesthetized Man*

Cited by 109 publications

References 21 publications

Cardiovascular Effects of Propranolol in Intact Puppies and Adult Dogs

Cardiovascular Effects of Propranolol in Intact Puppies and Adult Dogs

The demonstration of alternating contractile state in pulsus alternans

Extent of Carotid Sinus Regulation of the Myocardial Contractile State in Conscious Dogs

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