scholarly journals Effects of Hypoxia and Metabolic Inhibitors on the Intrinsic Heart Rate and Myocardial Contractility in Dogs

1969 ◽  
Vol 25 (1) ◽  
pp. 53-66 ◽  
Author(s):  
ANTHONY D. JOSE ◽  
FRANK STITT
Keyword(s):  
Heart Rate ◽  
Myocardial Contractility ◽  
Metabolic Inhibitors ◽  
Intrinsic Heart Rate

Circulating Catecholamines and Systolic Time Intervals in Labile and Sustained Hypertension

1978 ◽  
Vol 55 (s4) ◽  
pp. 65s-68s ◽  
Author(s):  
D. Cousineau ◽  
J. de Champlain ◽  
L. Lapointe
Keyword(s):  
Heart Rate ◽  
Essential Hypertension ◽  
Myocardial Contractility ◽  
Systolic Time Intervals ◽  
Normal Range ◽  
Time Intervals ◽  
Hypertensive Patients ◽  
Sustained Hypertension ◽  
Systolic Time ◽  
Hypotensive Response

1. Average supine circulating total catecholamine concentrations were found to be higher than the normal range in about 50% of patients with labile hypertension and in about 30% of patients with sustained essential hypertension. 2. These higher resting concentrations were mainly due to an increase in adrenaline in labile hypertension and to an increase in noradrenaline in sustained hypertension. 3. Patients with elevated catecholamine concentrations were also characterized by a higher heart rate, by an increased myocardial contractility and by greater hypotensive response after treatment with β-adrenoreceptor blocking agents. 4. These studies suggest the existence of subgroups of hypertensive patients with increased sympathetic tone.

Influence of cardiac innervation on intrinsic heart rate in dogs

1990 ◽  
Vol 258 (4) ◽  
pp. H1132-H1137 ◽  
Author(s):  
J. M. Evans ◽  
D. C. Randall ◽  
J. N. Funk ◽  
C. F. Knapp
Keyword(s):  
Heart Rate ◽  
Intrinsic Rate ◽  
Conscious State ◽  
Autonomic Innervation ◽  
Autonomic Activity ◽  
Cardiac Innervation ◽  
Cardiac Denervation ◽  
Ganglionic Blockade ◽  
Intrinsic Heart Rate

Intrinsic heart rate is defined as the rate at which the heart beats when all cardiac neural and hormonal inputs are removed. We determined the effect of prevailing autonomic innervation of the heart on the intrinsic heart rate in chronically maintained, sedated, normally innervated dogs (n = 14), and in 14 other dogs that had previously (greater than 12 day) undergone complete surgical cardiac denervation. Intrinsic rate was determined in both groups using the following two procedures: 1) pharmacological effector blockade; and 2) pharmacological ganglionic blockade. The intrinsic rate determined by effector blockade was 142.9 +/- 7.2 (SE) beats/min in the dogs with intact cardiac innervation. When the same treatment was given after total surgical cardiac denervation, intrinsic rate was 97.9 +/- 4.8 beats/min. Intrinsic heart rate was significantly (P less than 0.05) lower in surgically denervated dogs. Ganglionic blockade in surgically denervated animals yielded an intrinsic rate of 90.0 +/- 8.5 beats/min, which was again significantly lower than the corresponding value of 128.4 +/- 5.5 beats/min in normal dogs. There was no difference in the intrinsic heart rate as determined by effector vs. ganglionic blockade in either group of dogs. An additional six dogs were subjected to selective surgical sinoatrial nodal parasympathectomy; their intrinsic rate (effector blockade) in the conscious state was 115.8 +/- 4.3 beats/min; this was significantly lower than the corresponding value for normal dogs and significantly greater than in dogs subject to total surgical cardiac denervation. The lower rate observed in the totally denervated and selectively denervated dogs after effector and/or ganglionic blockades implies that intrinsic heart rate depends on the level or nature of prevailing autonomic activity.

Positive Inotropic and Lusitropic Effects of Triiodothyronine in Conscious Dogs with Pacing-induced Cardiomyopathy 

1997 ◽  
Vol 87 (1) ◽  
pp. 102-109 ◽  
Author(s):  
Iyad N. Jamali ◽  
Paul S. Pagel ◽  
Douglas A. Hettrick ◽  
Dermot Lowe ◽  
Judy R. Kersten ◽  
...  
Keyword(s):  
Heart Rate ◽  
Myocardial Contractility ◽  
Diastolic Pressure ◽  
Left Ventricular ◽  
Conscious Dogs ◽  
Segment Length ◽  
Lv Function ◽  
Baseline Heart Rate ◽  
Stroke Work ◽  
Lv Dysfunction

Background The effects of triiodothyronine (T3) on systemic hemodynamics, myocardial contractility (preload recruitable stroke work slope; Mw), and left ventricular (LV) isovolumic relaxation (time constant; tau) were examined before and after the development of pacing-induced cardiomyopathy in conscious dogs. Methods Dogs (n = 8) were chronically instrumented for measurement of aortic and LV pressure, dP/dtmax, subendocardial segment length, and cardiac output. Dogs received escalating doses (0.2, 2.0, and 20.0 mg/kg, intravenous) of T3 over 5 min at 1-h intervals, and peak hemodynamic effects were recorded 10 min after each dose and 24 h after the final dose. Dogs were then continuously paced at 220-240 beats/min for 21 +/- 2 days. Pacing was temporarily discontinued after the development of severe LV dysfunction, and administration of T3 was repeated. Results T3 produced immediate and sustained (24 h) increases (P < 0.05) in Mw and dP/dtmax in dogs before the initiation of pacing, consistent with a positive inotropic effect. No changes in tau occurred. Rapid ventricular pacing over 3 weeks increased baseline heart rate (sinus rhythm) and LV end-diastolic pressure, decreased mean arterial and LV systolic pressures, and caused LV systolic (decreases in Mw and dP/dtmax) and diastolic (increases in tau) dysfunction. T3 caused immediate and sustained increases in Mw (63 +/- 7 during control to 82 +/- 7 mmHg after the 2 mg/kg dose) and decreases in tau (65 +/- 8 during control to 57 +/- 6 ms after the 20 mg/kg dose), indicating that this hormone enhanced myocardial contractility and shortened LV relaxation, respectively, in the presence of chronic LV dysfunction. In contrast to the findings in dogs with normal LV function, T3 did not affect heart rate and calculated indices of myocardial oxygen consumption and reduced LV end-diastolic pressure (27 +/- 3 during control to 20 +/- 2 mmHg after the 2 mg/kg dose) in cardiomyopathic dogs. Conclusions The findings indicate that T3 produces favorable alterations in hemodynamics and modest positive inotropic and lusitropic effects in conscious dogs with LV dysfunction produced by rapid LV pacing.

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