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Effects of left circumflex coronary flow transducer implantation on posterior wall innervation
Insights
Coronary artery instrumentation with a flow transducer does not cause significant regional heart denervation. Studies show normal sympathetic nerve responses and norepinephrine levels after device implantation, ensuring cardiac autonomic function preservation.
Area of Science:
- Cardiovascular Surgery
- Autonomic Nervous System
- Cardiac Physiology
Background:
- Surgical procedures involving the coronary arteries may risk damaging cardiac nerves.
- Assessing regional denervation is crucial for understanding the impact of cardiac instrumentation on autonomic function.
Purpose of the Study:
- To investigate if dissecting around a coronary artery and implanting a flow transducer causes regional heart denervation.
- To evaluate the effects of such procedures on left ventricular wall thickening and norepinephrine content.
Main Methods:
- Four groups of dogs underwent either sham operations, flow transducer implantation, selective coronary artery denervation, or extensive posterior wall denervation.
- Ansae subclaviae stimulation was used to assess sympathetic nerve response.
- Left ventricular wall thickening and posterior LV wall norepinephrine levels were measured.
Main Results:
- Sympathetic stimulation increased posterior left ventricular wall thickening in sham and flow probe groups, but not in denervated groups.
- Norepinephrine levels were significantly reduced only in the extensively denervated group.
- Flow probe implantation did not alter norepinephrine levels or sympathetic response compared to sham operations.
Conclusions:
- Chronic instrumentation of the left circumflex coronary artery with a flow transducer does not lead to significant regional denervation of the posterior myocardium.
- Properly applied surgical instrumentation preserves cardiac autonomic function and regional sympathetic responses.
Abstract:
To determine whether dissection around a coronary artery and implantation of a flow transducer resulted in partial regional denervation of the heart, the effects of bilateral stimulation of the ansae subclaviae were evaluated on regional left ventricular (LV) wall thickening (WT) and tissue norepinephrine content in four groups of dogs following 1) sham operations (n = 6),2) implantation of a Doppler flow transducer on the left circumflex coronary artery (n = 6), 3) selective circumflex coronary artery denervation with topical phenol application (n = 5), and 4) selective denervation of the posterior LV wall by extensive surgical stripping of the left circumflex coronary artery and local application of phenol (n = 6). One week later after anesthesia (chloralose 100 mg/kg) and a second thoracotomy for implantation of ultrasonic WT crystals, stimulation of the ansae subclaviae increased posterior WT by 67 +/- 9% in the sham group, 71 +/- 14% in the flow probe group, and did not increase systolic WT in the denervated group. In the posterior LV wall, norepinephrine levels were reduced (P less than 0.01) in the denervated group (6 +/- 4 pg/mg) but not in the flow probe group (629 +/- 4 pg/mg) compared with the sham group (589 +/- 88 pg/mg). Selective left circumflex coronary artery denervation did not result in either diminished norepinephrine levels in the posterior LV wall nor diminished response of WT to sympathetic nerve stimulation. Thus chronic instrumentation applied properly to the left circumflex coronary artery does not result in significant regional denervation of the posterior myocardium.