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Chemoreflexes
An Experimental Study
Benjamin B. Y. Chiang, MD;
Andrew M. Roberts, PhD;
Abul M. Kashem, MD, PhD;
William P. Santamore, PhD;
Sufan Chien, MD;
Laman Gray, Jr, MD;
Robert Dowling, MD
Arch Surg. 2000;135:577-581.
Hypothesis Transmyocardial laser revascularization (TMLR) will not denervate the heart, because it does not destroy all of the afferents. This study was designed to determine if stimulation of cardiac sympathetic and vagal afferents from an area of the left ventricle treated with TMLR could evoke reflex effects, and thus whether TMLR would denervate the heart.
Methods The effect of TMLR on reflexes evoked by chemically stimulating cardiac afferents was examined in 9 dogs. Bradykinin and capsaicin were applied topically or injected into the left anterior descending coronary artery before and after TMLR and after bilateral vagotomy and sympathectomy. Aortic (AoP) and left ventricular pressures (LVP) and electrocardiography were monitored. The first derivatives of LVP (dP/dt) were calculated.
Results Topical bradykinin elicited variable hemodynamic responses. Topical capsaicin evoked pressor responses, increasing mean (± SEM) AoP (105±9 to 115±9 mm Hg; P<.001) and positive dP/dt (+dP/dt) (1032±81 to 1159±10 mm Hg/s; P<.01) before TMLR. Intracoronary capsaicin evoked a depressor response before TMLR. Pressor responses remained intact after TMLR with increases in mean AoP and +dP/dt (115±6 to 128±5 mm Hg and 1039±98 to1136±100 mm Hg/s, respectively; P<.01). Depressor responses also remained intact after TMLR (91±10 vs 101±11 mm Hg [P<.02], and 865±104 vs 931±104 mm Hg/s [P<.05], respectively). Hemodynamic responses were diminished after bilateral vagotomy and abolished after bilateral sympathectomy.
Conclusion Since activation of cardiac afferent nerves and reflex responses remained intact after TMLR, but changed after vagotomy or sympathectomy, TMLR does not denervate the heart sufficiently to be the cause of improved angina after TMLR.
From the Division of Cardiothoracic Surgery, Department of Surgery, The Jewish Hospital Heart and Lung Institute, Cardiothoracic Research Institute (Drs Chiang, Kashem, Santamore, Chien, Gray, and Dowling), and the Department of Physiology and Biophysics (Dr Roberts), University of Louisville School of Medicine, Louisville, Ky.
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