Denervated heart physiology

8 min read Last updated April 8, 2026

Surgical approach (context: orthotopic heart transplantation)

  • Recipient cardiectomy on cardiopulmonary bypass (CPB); donor heart implanted with atrial and great vessel anastomoses
    • Biatrial technique (older): donor atria sewn to recipient atrial cuffs → larger atria, more tricuspid regurgitation/arrhythmias
    • Bicaval technique (common): separate SVC and IVC anastomoses + LA cuff → better atrial geometry, less TR/arrhythmia
  • Aortic and pulmonary artery anastomoses; de-airing; reperfusion; wean from CPB with inotropes/vasopressors as needed
  • Denervation occurs because autonomic cardiac nerves are transected during explant/implant (variable partial reinnervation over months–years)

Anaesthetic management (for heart transplant / denervated heart patient undergoing surgery)

  • Type of anaesthesia: General anaesthesia (cardiac surgery); for non-cardiac surgery GA or regional may be used with haemodynamic goals in mind
  • Airway: ETT for transplant; for minor non-cardiac surgery ETT or SGA depending on aspiration risk and procedure
  • Duration: transplant typically 4–8+ hours (centre/complexity dependent); non-cardiac varies
  • How painful: sternotomy = severe; requires multimodal analgesia (opioids ± regional fascial plane blocks where appropriate) while avoiding haemodynamic instability
    • Neuraxial techniques in transplant are uncommon due to anticoagulation/CPB and haemodynamic considerations
  • Monitoring (transplant): invasive arterial line, CVC, often PA catheter/TOE; pacing capability; frequent ABGs, electrolytes, lactate
  • Key physiological principles: preload dependence, blunted HR responses, reliance on circulating catecholamines; treat hypotension with direct-acting agents

Definition and causes

  • Denervated heart: loss of sympathetic and parasympathetic (vagal) innervation to SA node, AV node, and myocardium
  • Commonest clinical model: orthotopic heart transplantation
  • Other contexts: surgical cardiac denervation (rare), advanced autonomic neuropathy (e.g. diabetes) causes partial functional denervation
  • Reinnervation: variable, often partial (sympathetic more than parasympathetic); may occur months–years post-transplant and is incomplete/heterogeneous

Baseline physiology in the denervated heart

  • Resting HR typically higher (often ~90–110 bpm) due to loss of vagal tone
  • Loss of rapid reflex control of HR and contractility (baroreceptor-mediated changes are absent at the heart)
    • Baroreflex still acts on peripheral vasculature (sympathetic outflow to vessels intact) → SVR can change, but HR does not respond appropriately
  • Cardiac output regulation relies more on preload (Frank–Starling) and circulating catecholamines (slower onset)
  • Reduced HR variability; absent respiratory sinus arrhythmia
  • Exercise response: delayed rise in HR and contractility; peak HR lower; slower recovery after exercise

Autonomic reflexes and pharmacology: what changes?

  • Vagal manoeuvres (carotid sinus massage, Valsalva) have little/no effect on HR/AV conduction
  • Atropine/glycopyrrolate: minimal effect on HR (no vagal tone to block); may still be used for antisialagogue/other indications but not for bradycardia treatment
  • Indirect-acting sympathomimetics (e.g. ephedrine) may have reduced/unpredictable chronotropic effect because they rely on presynaptic noradrenaline release
  • Direct-acting agents work: adrenaline, noradrenaline, phenylephrine, isoprenaline, dobutamine (act at receptors on myocardium/vessels)
    • Phenylephrine increases SVR; HR may not reflexly fall (no vagal reflex) → can increase BP without bradycardia
  • Adenosine: still acts directly on AV node; can terminate AVNRT but may cause prolonged AV block/asystole—use caution and resuscitation readiness
  • Neostigmine reversal: can cause bradycardia/asystole in transplant patients via non-vagal mechanisms (e.g. direct muscarinic effects on intrinsic cardiac neurons/denervation hypersensitivity); atropine may not reliably prevent/treat
    • Practical: consider sugammadex for aminosteroid NMBAs where appropriate; if neostigmine used, be prepared for pacing/direct chronotropes (isoprenaline/adrenaline)
  • Denervation hypersensitivity: upregulation of postsynaptic receptors may increase sensitivity to catecholamines (variable; more relevant early post-transplant)

Haemodynamic implications for anaesthesia

  • Preload dependence: avoid hypovolaemia, excessive venodilation, and sudden reductions in venous return (e.g. high neuraxial block, rapid position changes, pneumoperitoneum)
  • Blunted tachycardic response to hypotension/anaemia/light anaesthesia: rely on BP trends, stroke volume, and signs other than HR to judge depth/physiology
  • Treat hypotension: first optimise preload; then use direct-acting vasopressors/inotropes (phenylephrine/noradrenaline/adrenaline) rather than ephedrine as first-line
  • Bradycardia management: atropine often ineffective → use isoprenaline/adrenaline, consider pacing (external/transvenous) depending on context
  • Arrhythmias: atrial arrhythmias and conduction issues can occur; transplanted hearts may have dual P waves (recipient atrial remnant + donor atrium) depending on technique

Respiratory and ventilatory considerations

  • Avoid hypoxia, hypercapnia, acidosis: all increase PVR and can precipitate RV failure (especially if pulmonary hypertension present pre-transplant)
  • Positive pressure ventilation reduces venous return; titrate PEEP carefully and monitor stroke volume/BP

Perioperative issues in transplant recipients (important FRCA add-ons)

  • Immunosuppression: infection risk; strict asepsis; consider perioperative antimicrobial prophylaxis as per local protocol
  • Drug interactions: calcineurin inhibitors (tacrolimus/ciclosporin) interact with macrolides/azole antifungals; nephrotoxicity affects fluid/NSAID choices
  • Coronary allograft vasculopathy: can cause silent ischaemia (denervation) → ischaemia may present as heart failure/arrhythmia rather than angina
  • Rejection: may present with reduced exercise tolerance, arrhythmias, heart failure; perioperative decompensation risk

Key drug response summary (high-yield table in words)

  • Reduced/absent effect: atropine, glycopyrrolate (chronotropy), vagal manoeuvres; ephedrine (variable/reduced chronotropy)
  • Preserved effect: adrenaline, noradrenaline, phenylephrine, isoprenaline, dobutamine; adenosine (AV node); amiodarone (antiarrhythmic)
  • Potentially exaggerated/unpredictable: catecholamines (denervation hypersensitivity), neostigmine (bradycardia/asystole risk)
Explain the physiological consequences of cardiac denervation after heart transplantation.

Structure your answer: baseline HR, reflexes, CO control, exercise response.

  • Loss of parasympathetic and sympathetic cardiac nerves → loss of rapid autonomic control of SA/AV node and myocardium
  • Resting HR higher due to loss of vagal tone; reduced HR variability
  • No reflex tachycardia/bradycardia in response to BP changes; baroreflex effects on vessels remain
  • CO becomes more preload dependent; stress/exercise HR rise is delayed and mediated by circulating catecholamines
A transplant patient becomes hypotensive after induction. HR is unchanged. Why, and how do you treat it?

Examiner wants: mechanism + practical, drug-specific management.

  • HR unchanged because cardiac autonomic reflexes are absent; hypotension from vasodilation/reduced preload will not trigger reflex tachycardia
  • Treat causes: reduce anaesthetic depth if appropriate, optimise preload (fluids, leg raise), address bleeding
  • Use direct-acting vasopressors/inotropes: phenylephrine or noradrenaline for vasodilation; adrenaline/dobutamine if low contractility
  • Ephedrine may be less effective/unpredictable (indirect action)
Why is atropine often ineffective for bradycardia in a denervated heart, and what are your alternatives?

Core pharmacology viva.

  • Atropine blocks muscarinic receptors to remove vagal tone; in a denervated heart there is little/no vagal input to block
  • Alternatives: direct chronotropes (isoprenaline, adrenaline) and pacing (transcutaneous/transvenous) depending on severity
  • Correct reversible causes: hypoxia, hyperkalaemia, myocardial ischaemia, drug effects
Discuss the response of a denervated heart to ephedrine vs phenylephrine vs adrenaline.

Focus on indirect vs direct sympathomimetics and reflexes.

  • Ephedrine: mixed but largely indirect (noradrenaline release) → reduced/unpredictable chronotropy/inotropy in denervated heart
  • Phenylephrine: direct α1 agonist → increases SVR and BP; no reflex bradycardia expected
  • Adrenaline: direct β1/β2/α effects → reliable chronotropy/inotropy (dose dependent) and vasopressor effect at higher doses
A heart transplant recipient needs neuromuscular blockade reversal. What are the issues with neostigmine and what would you do?

This has appeared repeatedly as an FRCA-style viva topic (denervated heart + reversal).

  • Neostigmine can cause profound bradycardia/asystole in transplant recipients; atropine may not reliably prevent or treat it
  • Prefer sugammadex for rocuronium/vecuronium where suitable (renal function, availability, anaphylaxis risk considered)
  • If neostigmine used: ensure monitoring, have direct chronotrope ready (isoprenaline/adrenaline) and pacing capability
How does a denervated heart respond to exercise and why?

Mechanism-based explanation required.

  • Initial increase in CO mainly via increased venous return and stroke volume (Frank–Starling)
  • HR rise is delayed because it depends on circulating catecholamines rather than direct sympathetic nerves
  • Lower peak HR and slower recovery after exercise
What ECG features might you see after heart transplantation and why can there be two P waves?

Links surgical technique to physiology.

  • Depending on anastomotic technique, residual recipient atrial tissue can remain electrically active but disconnected from donor atrium/AV node
  • This can produce dual P waves (one from recipient atrium, one from donor SA node) with only donor atrial activity conducting to ventricles
  • Atrial arrhythmias and conduction abnormalities may occur, particularly with biatrial technique
Adenosine for SVT in a transplant patient: does it work and what are the risks?

Direct AV nodal action is preserved; safety considerations are key.

  • Adenosine acts directly on AV node receptors → can terminate AV node–dependent SVT
  • Risk of prolonged AV block/asystole; have resuscitation drugs and pacing/defib available; consider lower initial dose and senior support per local policy
Why might myocardial ischaemia be clinically silent in a transplanted (denervated) heart, and what are the implications for perioperative monitoring?

Classic FRCA concept: denervation abolishes angina.

  • Afferent pain fibres are interrupted → angina may be absent despite ischaemia
  • Ischaemia may present as heart failure, arrhythmias, hypotension, or ECG changes rather than pain
  • Implications: vigilant ECG monitoring, haemodynamic monitoring, low threshold for troponin/echo if unstable; optimise oxygen delivery
Outline key anaesthetic goals for non-cardiac surgery in a stable heart transplant recipient.

A common FRCA-style long viva: physiology + practical management.

  • Maintain preload and avoid sudden vasodilation; treat hypotension with direct-acting vasopressors
  • Do not rely on HR as a marker of pain/light anaesthesia; use BP, stroke volume surrogates, ET agent concentration, clinical signs
  • Plan for bradycardia: atropine may fail; have isoprenaline/adrenaline and pacing access available for higher-risk cases
  • Infection prevention and immunosuppression considerations; avoid nephrotoxins if renal impairment from calcineurin inhibitors

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