Bronchial responsiveness after human heart-lung transplantation

Area of Science:

• Pulmonary Medicine
• Transplantation Immunology
• Respiratory Physiology

Background:

• Heart-lung transplant (HLT) recipients often have altered airway physiology post-transplant.
• Understanding bronchial responsiveness is crucial for managing airway complications in HLT patients.

Purpose of the Study:

• To evaluate bronchial responsiveness to various inhaled agents in HLT recipients.
• To investigate the long-term evolution of bronchial hyperresponsiveness and its characteristics in HLT survivors.

Main Methods:

• Bronchial responsiveness to albuterol, ipratropium bromide, methacholine, and propranolol was assessed in 8 HLT recipients.
• Methacholine provocation tests were repeated in 7 long-term survivors to assess temporal changes.
• Specific airway conductance (sGaw) and forced expiratory volume in 1 second (FEV1) were measured.

Main Results:

• Albuterol and ipratropium bromide significantly improved sGaw, but not FEV1.
• Most HLT recipients were hyperresponsive to methacholine, while only one showed bronchoconstriction to propranolol.
• Ipratropium bromide pretreatment blocked methacholine-induced hyperresponsiveness.
• No time-dependent changes in methacholine hyperresponsiveness were observed in long-term survivors.
• Limited maximal airway narrowing was noted in response to methacholine.

Conclusions:

• HLT recipients exhibit stable bronchial hyperresponsiveness to methacholine, supporting denervation hypersensitivity of muscarinic receptors.
• Ipratropium bromide effectively blocks methacholine hyperresponsiveness in the denervated transplanted lung.
• These findings enhance understanding of airway physiology and potential therapeutic targets in HLT patients.