Impaired Baroreflex Function in an Ovine Model of Chronic Heart Failure Induced by Multiple Coronary Microembolizations

Figures

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  Figure 1. Representative electrocardiogram traces in sheep before and after microembolizations and mean data on S-T and T-wave segments. (A) Lead II trace highlighting the changes over time in the ECG, with (B) highlighting magnified lead II activity before microembolization and (C) after microembolization. Arrows highlight the T-wave of the ECG, showing a depression after microembolization. (D) Mean data on the height of the S-T segment and (E) T-wave amplitude before and after the individual microembolization procedures. Pre- indicates before microembolization and post- after microembolization. Microembolization 1 (E1) represented by square, microembolization 2 (E2) by circle, and microembolization 3 (E3) by triangle. (F) Ejection fraction before (open square) and after (12–14 weeks after) embolizations (open triangle) in the same animals and (G) fractional shortening before (open square) and after (12–14 weeks after embolizations) (open triangle). *p < 0.05 in E1 only, n = 6, ***p < 0.0001 in ejection fraction, ****p < 0.0001 in fractional shortening, n = 6.

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  Figure 2. Raw traces of sheep diaphragmatic electromyography and respiration rate in control and heart failure sheep. (A) Raw signal of dEMG in a control sheep and (B) raw signal of dEMG in a HF sheep, and (C) raw signal showing an apnea segment in a HF sheep 16 weeks after embolization. (D) Apnea incidence and (E) respiratory rate in control healthy sheep and in HF sheep 16 weeks after microembolization, control (square) and HF (triangle). *p < 0.05, **p < 0.01. Bars represent mean values ± SEM. Data from individual sheep are illustrated with symbols; dEMG, diaphragmatic electromyography.

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  Figure 3. Effect of microembolizations on the arterial baroreflex in conscious healthy and HF sheep. (A) Control animals (solid line) and HF animals (dashed line) (n = 6/group). Error bars at each end of the curves refer to ±SEM of the upper and lower heart rate (HR) plateaus. Circles and error bars represent mean ± SEM of resting systolic blood pressure (sBP) and heart rate (HR). (B) Changes in resting heart rate, due to phenylephrine and sodium nitroprusside infusions, plotted in 3 mmHg change bins. Gray bars represent control animals, black bars represent heart failure animals. *p < 0.05, n = 6/group.

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  Figure 4. Representative sheep cardiac tissue images and effect of microembolizations on collagen deposition and heart weight. (A) Top image shows section of left ventricle wall of the sheep heart in a control healthy animal and (B) bottom image shows section of left ventricle wall in a HF sheep 16 weeks after microembolization. (C) Heart weights of control (square) and HF (triangle) sheep. (D) Collagen content in control and HF sheep, *p < 0.05, ****p < 0.0001. Bars represent mean values ± SEM. Data from individual sheep are illustrated with symbols. C, control (square); HF (triangle), heart failure; LV, left ventricle of heart. Scale bar = 100 μm.