Reflex cardiac effects of local cutaneous cold exposure in dogs

1980 ◽  
Vol 239 (1) ◽  
pp. H114-H120
Author(s):  
J. F. Borgia ◽  
S. M. Horvath
Keyword(s):  
Heart Rate ◽  
Cardiac Contractility ◽  
Oxygen Demand ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Myocardial Oxygen Demand ◽  
Adrenergic Blockade ◽  
Stroke Index ◽  
Ventricular Contractility ◽  
Cold Stimulation

Cardiovascular responses initiated by local cutaneous cooling were evaluated in 16 anesthetized dogs of which 8 were pretreated with propranolol. Heart rate, cardiac index (CI), and indices of ventricular contractility were significantly elevated in untreated animals during cold stimulation. Myocardial oxygen uptake (MVo2) and left ventricular work (LVW) were also increased, and cardiac mechanical efficiency was significantly reduced. Total peripheral vascular resistance remained unchanged. In the propranolol group, heart rate decreased by 12 beats/min, but CI was maintained constant during cold by a rise in stroke index. Left ventricular dP/dtmax was reduced and ventricular preload elevated, but LVW, MVo2, and cardiac efficiency were unchanged. These data indicate that local cutaneous cooling increases myocardial oxygen demand by reflexly elevating heart rate and cardiac contractility rather than by increasing cardiac afterload. The response is completely eliminated by beta-adrenergic blockade. The significance of these observations in regard to the cold-intolerant individual with coronary disease is discussed.

Asymmetry in the control of cardiac performance by dorsomedial hypothalamus

2013 ◽  
Vol 304 (8) ◽  
pp. R664-R674 ◽  
Author(s):  
Carlos Henrique Xavier ◽  
Mirza Irfan Beig ◽  
Danielle Ianzer ◽  
Marco Antônio Peliky Fontes ◽  
Eugene Nalivaiko
Keyword(s):  
Heart Rate ◽  
Cardiac Contractility ◽  
Left Ventricular Pressure ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Adrenergic Blockade ◽  
Inotropic Effects ◽  
Dorsomedial Hypothalamus ◽  
Anesthetized Rats ◽  
Ectopic Beats

Dorsomedial hypothalamus (DMH) plays a key role in integrating cardiovascular responses to stress. We have recently reported greater heart rate responses following disinhibition of the right side of the DMH (R-DMH) in anesthetized rats and greater suppression of stress-induced tachycardia following inhibition of the R-DMH in conscious rats [both compared with similar intervention in the left DMH (L-DMH)], suggesting existence of right/left side asymmetry in controlling cardiac chronotropic responses by the DMH. The aim of the present study was to determine whether similar asymmetry is present for controlling cardiac contractility. In anesthetized rats, microinjections of the GABAA antagonist bicuculline methiodide (BMI; 40 pmol/100 nl) into the DMH-evoked increases in heart rate (HR), left ventricular pressure (LVP), myocardial contractility (LVdP/d t), arterial pressure, and respiratory rate. DMH disinhibition also precipitated multiple ventricular and supraventricular ectopic beats. DMH-induced increases in HR, LVP, LVdP/d t, and in the number of ectopic beats dependent on the side of stimulation, with R-DMH provoking larger responses. In contrast, pressor and respiratory responses did not depend on the side of stimulation. Newly described DMH-induced inotropic responses were rate-, preload- and (largely) afterload-independent; they were mediated by sympathetic cardiac pathway, as revealed by their sensitivity to β-adrenergic blockade. We conclude that recruitment of DMH neurons causes sympathetically mediated positive chronotropic and inotropic effects, and that there is an asymmetry, at the level of the DMH, in the potency to elicit these effects, with R-DMH > L-DMH.

scholarly journals Effect of exercise on cardiovascular parameters in search and rescue-trained dogs

2018 ◽  
Vol 70 (4) ◽  
pp. 1036-1044 ◽  
Author(s):  
P.O.P.R. Santos ◽  
E.A. Santos ◽  
A.C. Reis ◽  
A.M.M.R. Santos ◽  
M.C.C. Kuster ◽  
...  
Keyword(s):  
Physical Activity ◽  
Heart Rate ◽  
Oxygen Demand ◽  
Poor Performance ◽  
Cardiovascular Responses ◽  
Systemic Blood Pressure ◽  
Left Ventricular ◽  
Search And Rescue ◽  
Exercise Session ◽  
Physical Conditioning

ABSTRACT Physical activity alters the cardiovascular system of dogs, depending on the exercise characteristics and the animal’s physical conditioning. Little is known about the cardiovascular changes in rescue-trained dogs. This study evaluated the cardiovascular responses to a search and rescue exercise session to differentiate these alterations from cases of exhaustion or some possible pathology. Nine healthy rescue-trained dogs that trained for at least one year were used. Seven German Shepherds and two Belgian Shepherd Malinois were evaluated twice, immediately before exercise (M0) and immediately after a 20-minute training (M1). Electrocardiographic, echocardiographic, and systemic blood pressure (SBP) measurements were performed at each evaluation. Heart rate was evaluated in three moments, M0, M1 and five minutes after the end of the physical activity (M2). The results indicated that training increased oxygen demand and significantly increased cardiac output, left ventricular volume in diastole and aortic artery diameter, and the contraction force with the increased mitral annular motion without impairing systolic and diastolic cardiac functions. Heart rate values immediately and five minutes after exercise were similar to baseline values. Training did not alter SBP and the electrocardiographic parameters. The present study indicated good cardiac performance to the physical effort of rescue-trained dogs and reduced the chances of poor performance and the occurrence of sudden death caused by exercise in response to the pattern of activity performed.

scholarly journals Higher left ventricular mass–wall stress–heart rate product and outcome in aortic valve stenosis

Heart ◽  
2019 ◽  
Vol 105 (21) ◽  
pp. 1629-1633 ◽  
Author(s):  
Eva Gerdts ◽  
Sahrai Saeed ◽  
Helga Midtbø ◽  
Anne Rossebø ◽  
John Boyd Chambers ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Cox Regression ◽  
Oxygen Demand ◽  
Wall Stress ◽  
Left Ventricular ◽  
Adverse Event Rate ◽  
Myocardial Oxygen Demand ◽  
Lv Mass ◽  
All Cause Mortality

ObjectiveWhether increased myocardial oxygen demand could help explain the association of left ventricular (LV) hypertrophy with higher adverse event rate in patients with aortic valve stenosis (AS) is unknown.MethodsData from 1522 patients with asymptomatic mostly moderate AS participating in the Simvastatin-Ezetimibe in AS study followed for a median of 4.3 years was used. High LV mass–wall stress–heart rate product was identified as >upper 95% CI limit in normal subjects. The association of higher LV mass–wall stress–heart rate product with major cardiovascular (CV) events, combined CV death and hospitalised heart failure and all-cause mortality was tested in Cox regression analyses, and reported as HR and 95% CI.ResultsHigh LV mass–wall stress–heart rate product was found in 19% at baseline, and associated with male sex, higher body mass index, hypertension, LV hypertrophy, more severe AS and lower LV ejection fraction (all p<0.01). Adjusting for these confounders in time-varying Cox regression analysis, 1 SD higher LV mass–wall stress–heart rate product was associated with higher HR of major CV events (HR 1.16(95% CI 1.06 to 1.29)), combined CV death and hospitalised heart failure (HR 1.29(95% CI 1.09 to 1.54)) and all-cause mortality (HR 1.34(95% CI 1.13 to 1.58), all p<0.01).ConclusionIn patients with initially mild–moderate AS, higher LV mass–wall stress–heart rate product was associated with higher mortality and heart failure hospitalisation. Our results suggest that higher myocardial oxygen demand is contributing to the higher adverse event rate reported in AS patients with LV hypertrophy.Trial registration numberNCT000092677;Post-results.

scholarly journals One-year impact of bariatric surgery on left ventricular mechanics: results from the prospective FatWest study

2021 ◽  
Vol 1 (2) ◽  
Author(s):  
Lisa M D Grymyr ◽  
Saied Nadirpour ◽  
Eva Gerdts ◽  
Bjørn G Nedrebø ◽  
Johannes Just Hjertaas ◽  
...  
Keyword(s):  
Bariatric Surgery ◽  
Heart Rate ◽  
Oxygen Demand ◽  
Left Ventricular ◽  
Myocardial Oxygen Demand ◽  
Rapid Weight Loss ◽  
Obese Patients ◽  
Lv Mass ◽  
Severely Obese ◽  
One Year

Abstract Aims Patients with severe obesity are predisposed to left ventricular (LV) hypertrophy, increased myocardial oxygen demand, and impaired myocardial mechanics. Bariatric surgery leads to rapid weight loss and improves cardiovascular risk profile. The present prospective study assesses whether LV wall mechanics improve 1 year after bariatric surgery. Methods and results Ninety-four severely obese patients [43 ± 10 years, 71% women, body mass index (BMI) 41.8 ± 4.9 kg/m2, 57% with hypertension] underwent echocardiography before, 6 months and 1 year after gastric bypass surgery in the FatWest (Bariatric Surgery on the West Coast of Norway) study. We assessed LV mechanics by midwall shortening (MWS) and global longitudinal strain (GLS), LV power/mass as 0.222 × cardiac output × mean blood pressure (BP)/LV mass, and myocardial oxygen demand as the LV mass-wall stress-heart rate product. Surgery induced a significant reduction in BMI, heart rate, and BP (P &lt; 0.001). Prevalence of LV hypertrophy fell from 35% to 19% 1 year after surgery (P &lt; 0.001). The absolute value of GLS improved by—4.6% (i.e. 29% increase in GLS) while LV ejection fraction, MWS, and LV power/mass remained unchanged. In multivariate regression analyses, 1 year improvement in GLS was predicted by lower preoperative GLS, larger mean BP, and BMI reduction (all P &lt; 0.05). Low 1-year MWS was associated with female sex, preoperative hypertension, and higher 1-year LV relative wall thickness and myocardial oxygen demand (all P &lt; 0.001). Conclusion In severely obese patients, LV longitudinal function is largely recovered one year after bariatric surgery due to reduced afterload. LV midwall mechanics does not improve, particularly in women and patients with persistent LV geometric abnormalities. ClinicalTrials.gov identifier NCT01533142, 15 February 2012.

Cardiovascular responses to metabolic acidosis

1965 ◽  
Vol 208 (2) ◽  
pp. 237-242 ◽  
Author(s):  
S. Evans Downing ◽  
Norman S. Talner ◽  
Thomas H. Gardner
Keyword(s):  
Heart Rate ◽  
Metabolic Acidosis ◽  
Vascular Resistance ◽  
Diastolic Pressure ◽  
Cardiovascular Responses ◽  
Aortic Pressure ◽  
Left Ventricular ◽  
Ventricular Contractility ◽  
Precise Control ◽  
Arterial Ph

The performance of the left ventricle was examined in a feline preparation which allowed precise control of aortic pressure, cardiac output, heart rate, and temperature. The arterial pH, Po2, and Pco2 were continuously measured with a Jewett flow-through electrode assembly. Reduction of arterial pH from 7.45 to 6.80 by HCl or lactic acid infusion was associated with a minimal reduction or no change of left ventricular contractility as measured by the stroke volume or mean ejection rate for a given left ventricular end-diastolic pressure at a constant aortic pressure and heart rate. No evidence for a diminished positive inotropic response to norepinephrine was found. Simultaneous systemic and pulmonary pressure-flow curves demonstrated that metabolic acidosis caused a reduction of systemic vascular resistance and a concurrent increase of pulmonary vascular resistance.

scholarly journals Effect of aging on cardiac function during cold stress in humans

2010 ◽  
Vol 298 (6) ◽  
pp. R1627-R1633 ◽  
Author(s):  
Thad E. Wilson ◽  
Zhaohui Gao ◽  
Kari L. Hess ◽  
Kevin D. Monahan
Keyword(s):  
Young Adults ◽  
Oxygen Demand ◽  
Skin Surface ◽  
Left Ventricular ◽  
Myocardial Oxygen Demand ◽  
Internal Diameter ◽  
Ventricular Contractility ◽  
Left Ventricular Contractility ◽  
End Diastolic Volume ◽  
Left Ventricular Preload

To determine whether skin surface cooling increases left ventricular preload and contractility to a greater extent in older compared with young adults we studied 11 young (28 ± 2 yr; means ± SE) and 11 older (64 ± 3 yr) adults during normothermia (35°C water perfused through a tube-lined suit) and cooling (15°C water perfused for 20 min) using standard and tissue Doppler echocardiography. Cooling significantly decreased skin surface temperature in young (Δ2.8 ± 0.3°C) and older (Δ3.0 ± 0.3°C) adults and increased rate-pressure product, an index of myocardial oxygen demand, in older (6,932 ± 445 to 7,622 ± 499 mmHg·beats/min for normothermia and cooling, respectively), but not young (7,085 ± 438 to 7,297 ± 438 mmHg·beats/min) adults. Increases in blood pressure (systolic and mean blood pressure) during cooling were greater ( P < 0.05) in older than in young adults. Cooling increased preload in older (left ventricular end-diastolic volume from 106 ± 7 to 126 ± 9 ml and left ventricular internal diameter in diastole from 4.69 ± 0.12 to 4.95 ± 0.14 cm; both P < 0.01), but not young adults (left ventricular end-diastolic volume from 107 ± 7 to 111 ± 7 ml and left ventricular internal diameter in diastole from 4.70 ± 0.10 to 4.78 ± 0.10 cm). Indices of left ventricular contractility (ejection fraction, myocardial acceleration during isovolumic contraction, and peak systolic mitral annulus velocity) were unchanged during cooling in both young and older adults. Collectively, these data indicate that cooling increases left ventricular preload, without affecting left ventricular contractility in older but not young adults. Greater increases in preload and afterload during cooling in older adults contribute to greater increases in indices of myocardial oxygen demand and may help explain the increased risk of cardiovascular events in cold weather.

HEART COMPLICATIONS IN HYPERTHYROIDISM

2011 ◽  
pp. 7-17
Author(s):  
Hai Thuy Nguyen ◽  
Anh Vu Nguyen
Keyword(s):  
Atrial Fibrillation ◽  
Blood Pressure ◽  
Heart Rate ◽  
Heart Diseases ◽  
Systolic Dysfunction ◽  
Oxygen Demand ◽  
Left Ventricular ◽  
Cardiac Contraction ◽  
Cardiac Complications ◽  
Cardiac Symptoms

Thyroid hormone increases the force of the contraction and the amount of the heart muscle oxygen demand. It also increases the heart rate. Due to these reasons, the work of the heart is greatly increased in hyperthyroidism. Hyperthyroidism increases the amount of nitric oxide in the intima, lead them to be dilated and become less stiff. Cardiac symptoms can be seen in anybody with hyperthyroidism, but can be particularly dangerous in whom have underlying heart diseases. Common symptoms include: tachycardia and palpitations. Occult hyperthyroidism is a common cause of an increased heart rate at rest and with mild exertion. Hyperthyroidism can also produce a host of other arrhythmias such as PVCs, ventricular tachycardia and especially atrial fibrillation. Left ventricular diastolic dysfunction and systolic dysfunction, Mitral regurgitation and mitral valve prolapsed are heart complications of hyperthyroism could be detected by echocardiography. The forceful cardiac contraction increases the systolic blood pressure despite the increased relaxation in the blood vessels reduces the diastolic blood pressure. Atrial fibrillation, atrial enlargement and congestive heart failure are important cardiac complications of hyperthyroidism. An increased risks of stroke is common in patients with atrial fibrillation. Graves disease is linked to autoimmune complications, such as cardiac valve involvement, pulmonary arterial hypertension and specific cardiomyopathy. Worsening angina: Patients with coronary artery disease often experience a marked worsening in symptoms with hyperthyroidism. These can include an increase in chest pain (angina) or even a heart attack.

alpha-Adrenergic control of oxygen delivery to myocardium during exercise in conscious dogs

1982 ◽  
Vol 242 (5) ◽  
pp. H805-H809 ◽  
Author(s):  
G. R. Heyndrickx ◽  
P. Muylaert ◽  
J. L. Pannier
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Oxygen Consumption ◽  
Coronary Blood Flow ◽  
Coronary Sinus ◽  
Oxygen Delivery ◽  
Left Ventricular ◽  
Conscious Dogs ◽  
Adrenergic Blockade ◽  
Adrenergic Control

alpha-Adrenergic control of the oxygen delivery to the myocardium during exercise was investigated in eight conscious dogs instrumented for chronic measurements of coronary blood flow, left ventricular (LV) pressure, aortic blood pressure, and heart rate and sampling of arterial and coronary sinus blood. After alpha-adrenergic receptor blockade a standard exercise load elicited a significantly greater increase in heart rate, rate of change of LV pressure (LV dP/dt), LV dP/dt/P, and coronary blood flow than was elicited in the unblocked state. In contrast to the response pattern during control exercise, there was no significant change in coronary sinus oxygen tension (PO2), myocardial arteriovenous oxygen difference, and myocardial oxygen delivery-to-oxygen consumption ratio. It is concluded that the normal relationship between myocardial oxygen supply and oxygen demand is modified during exercise after alpha-adrenergic blockade, whereby oxygen delivery is better matched to oxygen consumption. These results indicate that the increase in coronary blood flow and oxygen delivery to the myocardium during normal exercise is limited by alpha-adrenergic vasoconstriction.

The effect of diabetes on heart rate and other determinants of myocardial oxygen demand in acute coronary syndromes

2004 ◽  
Vol 21 (9) ◽  
pp. 1025-1031 ◽  
Author(s):  
K. Foo ◽  
N. Sekhri ◽  
C. Knight ◽  
A. Deaner ◽  
J. Cooper ◽  
...  
Keyword(s):  
Heart Rate ◽  
Acute Coronary Syndromes ◽  
Oxygen Demand ◽  
Myocardial Oxygen Demand ◽  
Coronary Syndromes

Alteration in myocardial oxygen balance during exercise after beta-adrenergic blockade in dogs

1980 ◽  
Vol 49 (1) ◽  
pp. 28-33 ◽  
Author(s):  
G. R. Heyndrickx ◽  
J. L. Pannier ◽  
P. Muylaert ◽  
C. Mabilde ◽  
I. Leusen
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Oxygen Consumption ◽  
Myocardial Blood Flow ◽  
Coronary Blood Flow ◽  
Coronary Sinus ◽  
Myocardial Oxygen Consumption ◽  
Left Ventricular ◽  
Adrenergic Blockade ◽  
Oxygen Balance

The effects of beta-adrenergic blockade upon myocardial blood flow and oxygen balance during exercise were evaluated in eight conscious dogs, instrumented for chronic measurements of coronary blood flow, left ventricular pressure, aortic blood pressure, heart rate, and sampling of arterial and coronary sinus venous blood. The administration of propranolol (1.5 mg/kg iv) produced a decrease in heart rate, peak left ventricular (LV) dP/dt, LV (dP/dt/P, and an increase in LV end-diastolic pressure during exercise. Mean coronary blood flow and myocardial oxygen consumption were lower after propranolol than at the same exercise intensity in control conditions. The oxygen delivery-to-oxygen consumption ratio and the coronary sinus oxygen content were also significantly lower. It is concluded that the relationship between myocardial oxygen supply and demand is modified during exercise after propranolol, so that a given level of myocardial oxygen consumption is achieved with a proportionally lower myocardial blood flow and a higher oxygen extraction.

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