The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand

Boulet, Lindsey M.; Stembridge, Mike; Tymko, Michael M.; Tremblay, Joshua C.; Foster, Glen E.

doi:10.1152/ajpheart.00107.2016

Cited by 7 publications

(24 citation statements)

References 57 publications

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“…The contrasting findings may, in part, be due to the nature of our two scenarios. During acute hypoxia prior to LBPP, no change in ventricular volumes was observed, nor would it be expected (Boulet, Stembridge, Tymko, Tremblay, & Foster, 2016). With sustained hypoxic exposure, but it is well established that ventricular volumes decrease (Stembridge & Levine, 2019), especially in the left heart.…”

Section: Discussionmentioning

confidence: 91%

The influence of increased venous return on right ventricular dyssynchrony during acute and sustained hypoxaemia

Ewalts

Dawkins

Boulet

et al. 2021

Experimental Physiology

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Regional heterogeneity in timing of right ventricular (RV) contraction (RV dyssynchrony; RVD) occurs when pulmonary artery systolic pressure (PASP) is increased during acute hypoxia. Interestingly, RVD is not observed during exercise, a stimulus that increases both PASP and venous return. Therefore, we hypothesised that RVD in healthy humans is sensitive to changes in venous return, and examined whether (i) increasing venous return in acute hypoxia lowers RVD and (ii) if RVD is further exaggerated in sustained hypoxia, given increased PASP is accompanied by decreased ventricular filling at high altitude. RVD, PASP and right ventricular end-diastolic area (RVEDA) were assessed using transthoracic two-dimensional and speckle-tracking echocardiography during acute normobaric hypoxia (F iO 2 = 0.12) and sustained exposure (5-10 days) to hypobaric hypoxia (3800 m). Venous return was augmented with lower body positive pressure at sea level (LBPP; +10 mmHg) and saline infusion at high altitude. PASP was increased in acute hypoxia (20 ± 6 vs. 28 ± 7,

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Section: Discussionmentioning

confidence: 91%

The influence of increased venous return on right ventricular dyssynchrony during acute and sustained hypoxaemia

Ewalts

Dawkins

Boulet

et al. 2021

Experimental Physiology

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“…All echocardiographic measurements were collected by a trained sonographer (M. Stembridge) on a commercially available ultrasound system (Vivid E9; GE, Fairfield, CT) using a broadband M5S 5 MHz or a 3-V three-dimensional array transducer. In a previous study, the Cronbach's ␣-reliability test revealed ␣ values of 0.81 and 0.89 for both max and mean LAD velocities, respectively, suggesting good consistency between LAD velocity measurements (5). Participants assumed a left lateral position to allow for data collection.…”

Section: Experimental Measuresmentioning

confidence: 87%

“…Using observer-independent software, VTI is calculated as the integral of individual velocities across the cardiac cycle. Participants who had at least one suboptimal image were excluded before analyses (5).…”

Section: Discussionmentioning

confidence: 99%

“…A strength of our study was that we controlled for end-tidal gases at baseline values, during both CPT and LBNP, and in the ␣ 1 -receptor blockade condition. Fluctations and alterations in PET CO 2 are known to directly influence the diameter of the CCA (35) and LAD VTI (5). Following our ␣ 1 -receptor blockade, which directly affects mean arterial pressure and ventilatory regulation during sympathetic activation, clamping PET CO 2 and PET O 2 to baseline values reduced the possible interference with our carotid and coronary artery responses.…”

Section: Carotid Artery Versus Coronary Arterymentioning

confidence: 97%

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Similarity between carotid and coronary artery responses to sympathetic stimulation and the role of α₁-receptors in humans

Mil

Tymko

Kerstens

et al. 2018

Journal of Applied Physiology

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Carotid artery (CCA) dilation occurs in healthy subjects during cold pressor test (CPT), while the magnitude of dilation relates to cardiovascular risk. To further explore this phenomenon and mechanism, we examined carotid artery responses to different sympathetic tests, with and without α-receptor blockade and assessed similarity to these responses between carotid and coronary arteries. In randomized order, 10 healthy participants (25 ± 3 yr) underwent sympathetic stimulation using the CPT (3-min left-hand immersion in ice-slush) and lower-body negative pressure (LBNP). Before and during sympathetic tests, CCA diameter and velocity (Doppler ultrasound) and left anterior descending (LAD) coronary artery velocity (echocardiography) were recorded across 3 min. Measures were repeated 90 min following selective α-receptor blockade via oral prazosin (0.05 mg/kg body wt). CPT significantly increased CCA diameter, LAD maximal velocity, and velocity-time integral area-under-the-curve (all P < 0.05). In contrast, LBNP resulted in a decrease in CCA diameter, LAD maximal velocity, and velocity time integral (VTI; all P < 0.05). Following α-receptor blockade, CCA and LAD velocity responses to CPT were diminished. In contrast, during LBNP (-30 mmHg), α-receptor blockade did not alter CCA or LAD responses. Finally, changes in CCA diameter and LAD VTI responses to sympathetic stimulation were positively correlated ( r = 0.66, P < 0.01). We found distinct carotid artery responses to different tests of sympathetic stimulation, where α receptors partly contribute to CPT-induced responses. Finally, we found agreement between carotid and coronary artery responses. These data indicate similarity between carotid and coronary responses to sympathetic tests and the role of α receptors that is dependent on the nature of the sympathetic challenge. NEW & NOTEWORTHY We showed distinct carotid artery responses to cold pressor test (CPT; i.e., dilation) and lower-body negative pressure (LBNP; i.e., constriction). Blockade of α-receptors significantly attenuated dilator responses in carotid and coronary arteries during CPT, while no changes were found during LBNP. Our findings indicate strong similarity between carotid and coronary artery responses to distinct sympathetic stimuli, and for the role of α-receptors.

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“…Hypoxia and hypercapnia affect the systemic, pulmonary, and coronary circulation and may thus influence the echocardiographic appearance indirectly. In most clinical scenarios, the underlying pathology leading to respiratory derangement, including congestive heart failure, PE, and cardiomyopathy, dominates the echocardiographic picture.…”

Section: Echocardiographic Changes Due To Acute Respiratory Failurementioning

confidence: 99%

When appearances deceive: Echocardiographic changes due to common chest pathology

et al. 2018

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Most indications for performing echocardiography focus on the evaluation of properties intrinsic to the heart. However, numerous extra‐cardiac conditions indirectly convey changes to the echocardiographic appearance through alterations in the governing physiology. Pulmonary embolism increases pulmonary arterial pressure if a sufficient cross‐sectional area of the pulmonary vascular bed is occluded. This may result in dilatation of the right ventricle and, in severe cases, concomitant early diastolic septal collapse into the left ventricle. Acute respiratory failure has been shown to yield a similar echocardiographic appearance in experimental conditions due to the resultant pulmonary vasoconstriction. Echocardiography in the presence of pulmonary disease can reveal underlying cardiac pathologies such as pulmonary hypertension that contribute to the clinical severity of respiratory distress. Positive pressure ventilation affects preload, afterload, and compliance of both ventricles. The echocardiographic net result cannot be uniformly anticipated, but provides information on the deciding physiology or pathophysiology. Mediastinal pathology including tumors, herniation of abdominal content, and pleural effusion can often be visualized directly with echocardiography. Mediastinal pathologies adjacent to the heart may compress the myocardium directly, thus facilitating echocardiographic and clinical signs of tamponade in the absence of pericardial effusion. In conclusion, many pathologies of extra‐cardiac origin influence the echocardiographic appearance of the heart. These changes do not reflect properties of the myocardium but may well be mistaken for it. Hence, these conditions are essential knowledge to all physicians performing echocardiography across the spectrum from advanced cardiological diagnostics to rapid point‐of‐care focused cardiac ultrasonography.

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The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand

Cited by 7 publications

References 57 publications

The influence of increased venous return on right ventricular dyssynchrony during acute and sustained hypoxaemia

The influence of increased venous return on right ventricular dyssynchrony during acute and sustained hypoxaemia

Similarity between carotid and coronary artery responses to sympathetic stimulation and the role of α₁-receptors in humans

When appearances deceive: Echocardiographic changes due to common chest pathology

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The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand

Cited by 7 publications

References 57 publications

The influence of increased venous return on right ventricular dyssynchrony during acute and sustained hypoxaemia

The influence of increased venous return on right ventricular dyssynchrony during acute and sustained hypoxaemia

Similarity between carotid and coronary artery responses to sympathetic stimulation and the role of α1-receptors in humans

When appearances deceive: Echocardiographic changes due to common chest pathology

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Similarity between carotid and coronary artery responses to sympathetic stimulation and the role of α₁-receptors in humans