Myocardial oxygenation response curve during the HVBH.

<p>Signal intensity increases globally during the HVBH in control animals (A), yet the animals with a stenosis (B) show a significant decrease in the LAD territory (blue), while the remote region (green) remains above baseline with a similar characteristic of the control animals.</p

Myocardial oxygenation in relation to coronary blood flow and FFR.

<p>SI at the end of the HVBH is linearly related to both the coronary blood flow response (%) and the FFR (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164524#pone.0164524.t002" target="_blank">Table 2</a>).</p

Correlation of the regional oxygenation response to invasive measurements.

<p>Correlation of the regional oxygenation response to invasive measurements.</p

Experimental setup.

<p>A. Fluoroscopy image of the left anterior descending (LAD) coronary artery with the perivascular occluder the flow probe in place. B. Example of OS-CMR image with AHA automatic segmentation. C. Assignment of segments to LAD territory (blue) and remote myocardium (green), excluding the segments with possible mixed perfusion.</p

Segmental changes of myocardial oxygenation during the HVBH.

<p>Subtraction images (smoothed using a 6mm Gaussian filter) demonstrate that at the 30s, SI increased homogeneously in the control animal (A), while there was a decrease in the territory of the stenosed LAD (B). The mean response for each segment from all animals similarly shows that in control animals (top row, n = 8), ΔSI[%] is consistently larger for all segments, whereas for the stenosis animals (bottom row, n = 10) in the LAD regions a significant decrease is already observed at 30s, and this continues throughout the breath-hold. (*<i>p</i><0.05 between LAD and remote territory within the group, †<i>p</i><0.05, <0.05‡<i>p</i><0.01 for the difference in LAD response between groups).</p

Breathing maneuver protocol.

<p>For the combined hyperventilation breath-hold (HVBH) maneuver, a single rest measurement was obtained in a short breath-hold (A). The animal was then manually hyperventilated for 60s (B) followed immediately by a long breath-hold (C) that was imaged throughout, with a repeating OS sequence. Hyperventilation analysis was always compared between rest and the start of the breath-hold (red arrow), while the breath-hold could be analyzed at multiple time points with comparison to data obtained at the beginning of the breath-hold (purple arrow). The long breath-hold (LBH) followed step C, starting after a normal ventilation pattern.</p

Baseline Function and Angiography.

<p>Baseline Function and Angiography.</p

Changes of coronary blood flow during breathing maneuvers.

<p>Mean changes of coronary blood flow (ml/min) induced by breathing maneuvers in control (green) and stenosis (blue) animals. All maneuvers significantly changed the flow (*p<0.05) for control animals, while only hyperventilation altered the coronary blood flow for the stenosis group, (%-change is listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164524#pone.0164524.s002" target="_blank">S1 Table</a>). Both hyperventilation (HV) and the hyperventilation breath-hold (HVBH) triggered a flow response that was significantly different between stenosis and control animals (†<i>p</i><0.05), while there was no statistically significant difference between the groups observed with the long breath-hold (LBH).</p

Data_Sheet_1_Altered blood gas tensions of oxygen and carbon dioxide confound coronary reactivity to apnea.PDF

PurposeArterial blood gases change frequently during anesthesia and intensive care. Apnea can occur during diagnostic exams and airway and surgical interventions. While the impact of blood gas levels on coronary blood flow is established, their confounding effect on coronary vasoreactivity in response to an apneic stimulus, especially in coronary artery disease, is not known.MethodsSix anesthetized control swine and eleven swine with coronary artery stenosis were examined. Nine different blood gas levels from a combination of arterial partial pressure of oxygen (70, 100, and 300 mmHg) and carbon dioxide (30, 40, and 50 mmHg) were targeted. Apnea was induced by halting controlled positive pressure ventilation for 3–30s, while the left descending coronary artery flow was measured and reported relative to apnea duration, and at the adjusted mean (12s).ResultsAt normoxemic-normocapnic blood gas levels, apnea increased coronary blood flow in proportion to the duration of apnea in the control (r = 0.533, p ConclusionAlterations of blood oxygen and carbon dioxide affect coronary vascular reactivity induced by apnea in swine, which was attenuated further in the presence of coronary stenosis. Especially hyperoxia significantly reduces coronary blood flow and blunts coronary vascular reactivity.</p