The Effect of Atrial Pacing-Induced Tachycardia on Left Ventricular Contractile Function in Conscious Newborn and Adult Sheep

Fisher, David J.; Gross, Donald M.

doi:10.1203/00006450-198308000-00009

Cited by 13 publications

(12 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is similar to what we found in untreated newborn pigs in which baseline heart rate ranged between 130 and 150 beatslmin, and any increase in heart rate beyond that point would contribute very little to the contractile state. Our results differ from those of a previous study done on conscious neonatal lambs (29). This study demonstrated a substantial increase in LV contractility during rapid atrial pacing.…”

Section: Discussioncontrasting

confidence: 57%

Heart Rate Independence of Catecholamine-Induced Myocardial Damage in the Newborn Pig

et al. 1994

View full text Add to dashboard Cite

Neonates undergoing heart surgery are exposed to high levels of circulating catecholamines. Our objective was to determine to what extent epinephrine (E)-related cardiotoxicity can be attributed to induced tachycardia. We assessed left ventricle function by pressure-volume data obtained by conductance catheter/micromanometer technique and correlated it with ultrastructure in newborn piglets (3 to 7 d old). Group A (n = 6) received E (1 p,g/kg/min) for 2 h, whereas group B piglets (n = 6) were atrially paced at a rate (220lmin) matched to group A. Left ventricle peak systolic pressure and stroke work were significantly higher @ < 0.05) in group A. End-systolic elastance increased during E infusion (70%) versus no significant change in group B. After 2 h of E infusion, end-systolic elastance was significantly reduced in group A from 9.8 + 3.5 to 5 + 2.4 mm HgImL ( p < 0.05).Chamber stiffness index increased during E infusion from 0.36 ? 0.2 to 0.6 + 0.3 mL-' ( p < 0.05) and remained High plasma levels of endogenous catecholamines exist in neonates having congenital heart disease (I), and administration of catecholamines is frequently required for hemodynamic support preoperatively. The inotropic effect of all p-agonists is mediated through activation of the enzyme adenylate cyclase, resulting in increased intracellular levels of CAMP and enhancement of transarcolemmal c a 2 + influx (2). The association between high circulating plasma catecholamines and acute cardiotoxicity has previously been studied (3, 4), and the mechanisms are attributed to impaired intracellular c a 2 + handling (5), reduced coronary blood flow, and formation of highly cytotoxic free radicals derived from catecholamine autoxidation (6). Because most p-agonists exert both positive inotropic and chronotropic effects, it is still unclear to what extent catecholamine-induced cardiomy- Supported by a grant from the Ontario Heart Foundation (T-1376).elevated (0.58 t 0.2 mL-') after E infusion was discontinued versus no change in group B. E-induced left ventricle dysfunction was associated with scattered but irreversible ultrastructural changes consisting of sarcolemmal rupture and loss of mitochondrial architecture, whereas only minor reversible changes such as microvesicular lipid accumulation and mitochondria1 swelling were seen in group B. We conclude that E cardiotoxicity in the neonate is independent of induced tachycardia. opathy is attributable to tachycardia. Therefore, this study was designed to compare the effects of rapid atrial pacing with those of E on LV function and ultrastructure in newborn piglets. Myocardial performance was assessed by the end-systolic and diastolic PV relationship (7) and correlated with ultrastructural and metabolic recovery by serial ATP measurements before and after administration of E and pacing.

show abstract

Section: Discussioncontrasting

confidence: 57%

Heart Rate Independence of Catecholamine-Induced Myocardial Damage in the Newborn Pig

et al. 1994

View full text Add to dashboard Cite

show abstract

“…Treatment differences in cardiac output must be explained by changes in either heart rate, contractility, preload, or afterload (14). The increased heart rate in chloralose-treated lambs was within the range associated with increased cardiac output and contractility in conscious lambs tested by electrical pacing of the left atrium (15). The heart rate increase in chloralose-treated lambs would be expected to increase cardiac output; therefore, heart rate changes alone do not explain the reduced cardiac output.…”

Section: Pulmonary Vascular Resistancementioning

confidence: 87%

“…These changes were unrelated to baseline tone of the circulation, cardiac output, mean left atrial pressure, or physiologically important changes in arterial blood gas tensions. In addition, chloralose-treated lambs had increased heart rate, systemic vascular resistance, and pulmonary vascular resistance compared to controls during alveolar hypoxia (13)(14)(15). Importantly, chloralose-treated lambs did not increase their cardiac output during alveolar hypoxia a s did control lambs.…”

mentioning

confidence: 85%

Chloralose Alters Both Basal Hemodynamics and Cardiovascular Responses to Alveolar Hypoxia in Chronically Instrumented, Spontaneously Breathing Lambs'

et al. 1989

View full text Add to dashboard Cite

ABSTRACT. We studied the effects of chloralose anesthesia on the basal hemodynamic state and on the cardiovascular response to alveolar hypoxia in chronically instrumented, spontaneously breathing lambs, compared with responses to the saline vehicle. Chloralose significantly increased heart rate (23%), mean systemic arterial pressure (]I%), systemic vascular resistance (21%), mean pulmonary arterial pressure (23%), and pulmonary vascular resistance (46%) (n = 30, p < 0.05, ANOVA). These changes were unrelated to baseline tone of the circulation, cardiac output, mean left atrial pressure, or physiologically important changes in arterial blood gas tensions. In addition, chloralose-treated lambs had increased heart rate, systemic vascular resistance, and pulmonary vascular resistance compared to controls during alveolar hypoxia (13-15% FiOz). Importantly, chloralose-treated lambs did not increase their cardiac output during alveolar hypoxia a s did control lambs. During hypoxia, systemic vascular resistance remained elevated in chloralose-treated lambs, but declined in control lambs. Chloralose has been recommended a s an ideal anesthetic agent for cardiovascular experimentation. Our data suggest that chloralose-induced alterations in basal hemodynamics and in cardiovascular responses to alveolar hypoxia represent an uncontrolled variable in acute experimental studies. Complex cardiovascular alterations caused by anesthesia should be considered in experimental design. (Pediatr Res 25389-395, 1989) Abbreviations PVR, pulmonary vascular resistance SVR, systemic vascular resistance

show abstract

“…Fisher and Gross (27) have shown that pacing the newborn lamb heart at rates up to 300 bpm caused no significant increase in left atrial or left ventricular end diastolic pressure. It is more likely that the left atrial hypertension seen at high rates of infusion resulted from the markedly elevated systemic vascular resistance (i.e.…”

Section: Effects Of Dopumine Infusionmentioning

confidence: 99%

The Effects of Dopamine Infusion on Regional Blood Flow in Newborn Lambs

et al. 1987

View full text Add to dashboard Cite

ABSTRACT. The purpose of this project was to investigate the effects of high rates of dopamine infusion on cardiac output and regional blood flow in the lamb. We studied eight unanesthetized newborn lambs (mean age 7 + 2 days) during a 15-min baseline period and while infusing dopamine at 5-, 20-, 80-, and 160 pg/kg/min. We measured cardiac output and mean aortic, pulmonary arterial and left atrial pressures, and organ blood flow using radionuclidelabeled microspheres at each rate of dopamine infusion. Cardiac output increased significantly with increasing rates of infusion up to 80 pg/kg/min but decreased at 160 pg/kg/ min. Aortic, pulmonary arterial, and left atrial pressures increased at rates of infusion above 5 pg/kg/min. Blood flow to all organs was unchanged at the 5 pg/kg/min rate of infusion of dopamine while blood flow to the brain and heart increased at the 80 pg/kg/min rate of infusion and blood flow to the gut and kidney decreased. We conclude that dopamine is an effective inotropic agent in the newborn lamb but that an inotropic:afterload mismatch exists at high infusion rates. Despite an increase in cardiac output at low rates of infusion, dopamine did not selectively vasodilate the vascular bed of any organs tested. Furthermore, at high rates of infusion dopamine actually impaired blood flow to the gut and kidney. (Pediatr Res 21: 131-136, 1987) Dopamine remains an extensively used catecholamine in the management of shock in critically ill infants and children (1). We recently studied the effects of dopamine on hemodynamics in 2-to 3-wk-old lambs and found it to be an effective inotropic agent (2). However, inherent properties of neonatal myocardium may render it relatively unresponsive to the inotropic actions of dopamine and the same effects may not occur in the younger lamb. In the clinical setting, myocardial immaturity may prompt the use of rates of infusion of dopamine in excess of those currently recommended (1). The effects of high rates of infusion on regional blood flow in the newborn are unknown.The purpose of our study was to investigate the effects of dopamine on regional blood flow in newborn lambs over a wide range of infusion rates. We hypothesized that in the newborn lamb dopamine would not increase cardiac output at conventionally used rates of infusion but might at higher rates. At these higher rates, however, we anticipated that the a-adrenergic effect of dopamine would compromise blood flow to vital organs. MATERIALS AND METHODSSurgical preparations. We operated on eight lambs using halothane and nitrous oxide anesthesia delivered by a piston type ventilator. From a left hindlimb cutdown we inserted polyvinyl catheters into a peripheral artery and vein and advanced them into the descending aorta and inferior vena cava, respectively. We also inserted a 3.5 Fr thermistor wire (Edwards Laboratories, Inc., Irvine, CA) into a peripheral artery by separate hindlimb cutdown and advanced it into the descending aorta. Finally, we placed a polyvinyl catheter in a forelimb artery and ad...

show abstract

The Effect of Atrial Pacing-Induced Tachycardia on Left Ventricular Contractile Function in Conscious Newborn and Adult Sheep

Cited by 13 publications

References 25 publications

Heart Rate Independence of Catecholamine-Induced Myocardial Damage in the Newborn Pig

Heart Rate Independence of Catecholamine-Induced Myocardial Damage in the Newborn Pig

Chloralose Alters Both Basal Hemodynamics and Cardiovascular Responses to Alveolar Hypoxia in Chronically Instrumented, Spontaneously Breathing Lambs'

The Effects of Dopamine Infusion on Regional Blood Flow in Newborn Lambs

Contact Info

Product

Resources

About